GNF - FeCrAl Lead Test Assemblies, RAJ-II Letter

Attachment 3

M180196

GNF FeCrAl Lead Test Assemblies, RAJ-II Letter Authorization Request and Technical Basis

Non-Proprietary Information

INFORMATION NOTICE

This is a non-proprietary version of M180196 Enclosure 2, which has the proprietary information removed.

Portions of the document that have been removed are indicated by an open and closed bracket as shown

here [[ ]].

M180196 Non-Proprietary Information Attachment 3 ATF RAJ-II Letter Authorization Technical Basis

Page 1 of 70

Table of Contents 1.0 General Information ................................................................................................ 8

1.1 Introduction ............................................................................................................. 8

1.2 Package Description ............................................................................................... 9

1.2.1 Packaging ................................................................................................................ 9

1.2.2 Contents .................................................................................................................. 9

1.2.3 Special Requirements for Plutonium ..................................................................... 11

1.2.4 Operational Features ............................................................................................. 11

1.3 Appendix ............................................................................................................... 11

1.3.1 RAJ-II General Arrangement Drawings ................................................................. 11

1.3.2 References ............................................................................................................ 11

1.4 Additional GNF FeCrAl Specific Information ......................................................... 12

1.4.1 GNF FeCrAl LTA Description ................................................................................ 12

1.4.2 GNF FeCrAl Fuel Rod Description ........................................................................ 12

1.5 GNF FeCrAl Letter Authorization Comingling Restriction ..................................... 14

2.0 Structural Evaluation ............................................................................................. 15

2.1 Description of Structural Design ........................................................................... 15

2.1.1 Discussion ............................................................................................................. 15

2.1.2 Design Criteria ....................................................................................................... 17

2.1.3 Weights and Centers of Gravity ............................................................................ 18

2.1.4 Identification of Codes and Standards for Package Design .................................. 18

2.2 Materials ............................................................................................................... 18

2.2.1 Material Properties and Specifications .................................................................. 18

2.2.2 Chemical, Galvanic, or Other Reactions ............................................................... 19

2.2.3 Effects of Radiation on Materials ........................................................................... 19

2.3 Fabrication and Examination ................................................................................ 20

2.3.1 Fabrication ............................................................................................................. 20

2.3.2 Examination ........................................................................................................... 20

2.4 General Requirements for All Packages ............................................................... 20

2.5 Lifting and Tie-Down Standards for All Packages ................................................. 20

2.6 Normal Conditions of Transport ............................................................................ 20

2.6.1 Heat ....................................................................................................................... 20

2.6.2 Cold ....................................................................................................................... 21

2.6.3 Reduced External Pressure .................................................................................. 21

2.6.4 Increased External Pressure ................................................................................. 21


Page 2 of 70

2.6.5 Vibration ................................................................................................................ 21

2.6.6 Water Spray .......................................................................................................... 21

2.6.7 Free Drop .............................................................................................................. 21

2.6.8 Corner Drop ........................................................................................................... 21

2.6.9 Compression ......................................................................................................... 21

2.6.10 Penetration ............................................................................................................ 22

2.7 Hypothetical Accident Conditions ......................................................................... 22

2.7.1 Free Drop .............................................................................................................. 22

2.7.2 Crush ..................................................................................................................... 22

2.7.3 Puncture ................................................................................................................ 22

2.7.4 Thermal ................................................................................................................. 22

2.7.5 Immersion—Fissile Material .................................................................................. 23

2.7.6 Immersion—All Packages ..................................................................................... 23

2.7.7 Deep Water Immersion Test (for Type B Packages Containing More than 105 A2) .............................................................................................................................. 23

2.7.8 Summary of Damage ............................................................................................ 23

2.8 Accident Conditions for Air Transport of Plutonium .............................................. 23

2.9 Accident Conditions for Fissile Material Packages for Air Transport .................... 23

2.10 Special Form ......................................................................................................... 23

2.11 Fuel Rods .............................................................................................................. 23

2.12 GNF FeCrAl Bundle 9m Drop Evaluation ............................................................. 24

2.13 APPENDIX ............................................................................................................ 24

2.13.1 References ............................................................................................................ 24

3.0 Thermal Evaluation ............................................................................................... 25

3.1 Description of Thermal Design .............................................................................. 25

3.1.1 Design Features .................................................................................................... 25

3.1.2 Content’s Decay Heat ........................................................................................... 25

3.1.3 Summary Tables of Temperatures ........................................................................ 25

3.1.4 Summary Tables of Maximum Pressures ............................................................. 25

3.2 Material Properties and Component Specifications .............................................. 25

3.2.1 Material Properties ................................................................................................ 25

3.2.2 Component Specifications ..................................................................................... 25

3.3 Thermal Evaluation Under Normal Conditions of Transport ................................. 26

3.3.1 Heat and Cold ....................................................................................................... 26

3.3.2 Maximum Normal Operating Pressure .................................................................. 26

3.4 Thermal Evaluation Under Hypothetical Accident Conditions ............................... 26

3.4.1 Initial Conditions .................................................................................................... 26


Page 3 of 70

3.4.2 Fire Test Conditions .............................................................................................. 26

3.4.3 Maximum Temperatures and Pressure ................................................................. 26

3.4.4 Maximum Thermal Stresses .................................................................................. 27

3.4.5 Accident Conditions for Fissile Material Packages for Air Transport ..................... 27

3.5 Appendix ............................................................................................................... 27

3.5.1 References ............................................................................................................ 27

3.5.2 ANSYS Input File Listing ....................................................................................... 27

3.5.3 NCT Transient Analysis ......................................................................................... 28

4.0 Containment .......................................................................................................... 29

4.1 Description of the Containment System ................................................................ 29

4.2 Containment under Normal Conditions of Transport ............................................ 30

4.3 Containment under Hypothetical Accident Conditions .......................................... 30

4.4 Leakage Rate Tests for Type B Packages ........................................................... 30

4.5 Appendix ............................................................................................................... 30

4.5.1 Determination of Allowable Leak Rates ................................................................ 30

4.5.2 Summary ............................................................................................................... 30

4.5.3 References ............................................................................................................ 30

5.0 SHIELDING EVALUATION ................................................................................... 31

5.1 References ............................................................................................................ 31

6.0 Criticality Evaluation .............................................................................................. 32

6.1 Description of Criticality Design ............................................................................ 32

6.1.1 Design Features .................................................................................................... 33

6.1.2 Summary Table of Criticality Evaluation ................................................................ 33

6.1.3 Criticality Safety Index ........................................................................................... 34

6.2 Fissile Material Contents ....................................................................................... 34

6.3 General Considerations ........................................................................................ 34

6.3.1 Model Configuration .............................................................................................. 34

6.3.2 Materials Properties .............................................................................................. 35

6.3.3 Computer Codes and Cross-Section Libraries ...................................................... 36

6.3.4 Demonstration of Maximum Reactivity .................................................................. 36

6.4 Single Package Evaluation ................................................................................... 41

6.5 Evaluation of Package Arrays under Normal Conditions of Transport .................. 42

6.6 Package Arrays Under Hypothetical Accident Conditions (2N=4) ........................ 42

6.6.1 Configuration ......................................................................................................... 42

6.6.2 Results .................................................................................................................. 42

6.7 Fuel Rod Transport in the RAJ-II .......................................................................... 54


Page 4 of 70

6.8 Fissile Material Packages for Air Transport .......................................................... 54

6.9 Conclusion ............................................................................................................ 54

6.10 Benchmark Evaluations ........................................................................................ 55

6.10.1 SCALE 4.4a and GEMER ..................................................................................... 55

6.10.2 KENO-VI ................................................................................................................ 55

6.11 KENO-VI Inputs .................................................................................................... 55

6.12 References ............................................................................................................ 55

6.13 Limiting Parameter Studies ................................................................................... 56

6.13.1 Fuel Assembly Gadolinia-Urania Rod Study for 2N=49 HAC Arrays .................... 56

6.13.2 Fuel Assembly Channel Study (2N=49) ................................................................ 56

6.13.3 Fuel Pellet Diameter Sensitivity Study (2N=100) .................................................. 56

6.13.4 Fuel Rod Cladding Thickness Study (2N=100) ..................................................... 57

6.13.5 Limiting Cladding Material (2N=100) ..................................................................... 58

6.13.6 Impact of Segmented GNF FeCrAl LTRs (2N=49) ................................................ 59

6.13.7 Limiting Fuel Enrichment Zone for Section 6.13 and 6.14 Evaluations (2N=49) ... 64

6.13.8 Material Distribution Reactivity Sensitivity Study for Sections 6.13 and 6.14 Evaluations (2N=49) ............................................................................................. 64

6.14 Package Arrays Under Hypothetical Accident Conditions (2N=49) ...................... 66

6.14.1 Configuration (2N=49) ........................................................................................... 66

6.14.2 Results (2N=49) .................................................................................................... 66

7.0 Package Operations ............................................................................................. 69

7.1 References ............................................................................................................ 69

8.0 Acceptance Tests and Maintenance Program ...................................................... 70

8.1 References ............................................................................................................ 70


Page 5 of 70

LIST OF TABLES

Table 1-1. GNF FeCrAl Parameters Outside of Reference 1-1 ................................................. 9

Table 1-2. RAJ-II Content Radionuclide Maximum Concentrations ........................................ 10

Table 2-1. Changes to Reference 2-2 Table 3 Fuel Assembly Parameters ............................ 16

Table 2-2. GNF FeCrAl Alloy Nominal Material Composition (wt%) ........................................ 19

Table 3-1. GNF FeCrAl Melting Point ...................................................................................... 26

Table 4-1. RAJ-II Content Radionuclide Maximum Concentrations ........................................ 29

Table 6-1. LTA Parameters Outside of the RAJ-II SAR .......................................................... 33

Table 6-2. Criticality Evaluation Summary for RAJ-II GNF FeCrAl LTA and GNF2 Configurations ........................................................................................................ 33

Table 6-3. Summary of Criticality Safety Index for RAJ-II GNF FeCrAl LTA and GNF2 Configurations ........................................................................................................ 34

Table 6-4. Material Specifications for the GNF FeCrAl LTA RAJ-II Letter Authorization ......... 36

Table 6-5. Limiting HAC Model Parameters for RAJ-II Package Array Containing the Bounding GNF Letter Authorization Fuel Assembly ............................................... 37

Table 6-6. Increased Rod-to-Rod Pitch at Optimal Moderation ............................................... 38

Table 6-7. Summary of Impact on Hypothetical Radial and Axial Fuel Movements ................ 46

Table 6-8. Results of Hypothetical Radial and Axial Fuel Movements of 8 GNF FeCrAl LTRs from Primary Bundle Locations (2N=4) ........................................................ 46

Table 6-9. Results of Hypothetical Radial and Axial Fuel Movements of 8 GNF FeCrAl LTRs from Secondary Bundle Locations (2N=4) .................................................... 47

Table 6-10. Results of Removing the 8 Hypothetical Failed GNF FeCrAl Fuel Segments from the LTA (2N=4) .............................................................................................. 52

Table 6-11. Results from RAJ-II HAC Channel Study (2N=49) ................................................. 56

Table 6-12. Comparison of Fuel Rod OD and Cladding Thickness for GNF Letter Authorization Bundle .............................................................................................. 58

Table 6-13. Results of Segmented GNF FeCrAl LTRs in Primary Locations [[ ]] ................................................................................................................. 61

Table 6-14. Results of Segmented GNF FeCrAl LTRs in Primary Locations [[ ]] .................................................................................................... 62

Table 6-15. Results of Segmented GNF FeCrAl LTRs in Secondary Locations [[ ]] ............................................................................................. 64

Table 6-16. Comparison of Limiting Fuel Enrichment Zones .................................................... 64


Page 6 of 70

LIST OF FIGURES

Figure 1-1. Allowable Locations for LTRs ................................................................................. 12

Figure 1-2. Segment Schematic ............................................................................................... 13

Figure 1-3. Example Segmented Rod Axial Arrangement ........................................................ 14

Figure 2-1. Potential Locations for GNF FeCrAl Full Length Rods within BWR 10x10 Fuel Assembly ............................................................................................. 16

Figure 6-1. RAJ-II Cross-Section HAC Model without Gadolinia Rods .................................... 35

Figure 6-2. Moderator Density Sensitivity Study for the RAJ-II HAC Worst Case Parameter Fuel Design .......................................................................................... 40

Figure 6-3. PCF Thickness Sensitivity Study for 2N=4 HAC Array .......................................... 41

Figure 6-4. Hypothetical Radial Fuel Relocation Positions (Red) ............................................. 44

Figure 6-5. Primary (Green) and Secondary (Purple) GNF FeCrAl LTRs with Hypothetical Radial Fuel Relocation Positions (Red) ............................................. 45

Figure 6-6. Example of Axial Fuel Movement (Green Rods) into Top of Fuel Bundle .............. 45

Figure 6-7. IC Moderation Density Study for Evaluation 40 ...................................................... 49

Figure 6-8. OC Moderation Density Study for Evaluation 40 .................................................... 50

Figure 6-9. IC and OC Moderation Density Study for Evaluation 40 ........................................ 51

Figure 6-10. IC Moderation Density Study for Evaluation 78 ...................................................... 52

Figure 6-11. OC Moderation Density Study for Evaluation 78 .................................................... 53

Figure 6-12. IC and OC Moderation Density Study for Evaluation 78 ........................................ 54

Figure 6-13. RAJ-II HAC Array Pellet Diameter Sensitivity Study .............................................. 57

Figure 6-14. Limiting Cladding Material Study for Bounding GNF Letter Authorization Bundle .................................................................................................................... 59

Figure 6-15. Potential GNF FeCrAl LTR Locations and Axis of Symmetry ................................ 60

Figure 6-16. Examples of GNF FeCrAl LTRs in Primary (Red) Locations .................................. 61

Figure 6-17. Examples of GNF FeCrAl LTRs in Secondary (Green) Locations ......................... 63

Figure 6-18. PCF Thickness Sensitivity Study for 2N=49 HAC Array ........................................ 65

Figure 6-19. IC Moderator Density Sensitivity Study for Type A GNF Letter Authorization Fuel Assembly Shipments ...................................................................................... 67

Figure 6-20. PCF Thickness Sensitivity Study for Type A GNF Letter Authorization Fuel Assembly Shipments .............................................................................................. 68


Page 7 of 70

ACRONYMS

Term Definition

ASME American Society of Mechanical Engineers

ASNT American Society for Non-destructive Testing

ASTM American Society for Testing and Materials

B&PVC Boiler and Pressure Vessel Code

ATF Accident Tolerant Fuel

BWR Boiling Water Reactor

CoC Certificate of Compliance

CFR Code of Federal Regulations

CSA Criticality Safety Analysis

CSI Criticality Safety Index

CTU Certification Test Unit

DOE Department of Energy

FeCrAl Iron Chrome Aluminum Alloy

Gd2O3-UO2 Gadolinia-Urania

GNF Global Nuclear Fuel

HAC Hypothetical Accident Conditions

IC Inner Container

ID Inner Diameter

JIS Japanese Industrial Standard

JSNDI / JSND

Japanese Society for Non-destructive Inspection

LTA Lead Test Assembly

LTR Lead Test Rod

MNOP Maximum Normal Operating Pressure

NCT Normal Conditions of Transport

NRC Nuclear Regulatory Commission

OC Outer Container

OD Outer Diameter

PCF Polyethylene Cushioning Foam

SAR Safety Analysis Report

U-235 Uranium-235

UO2 Uranium Oxide

USL Upper Subcritical Limit

wt% Weight Percent


Page 8 of 70

1.0 GENERAL INFORMATION

The purpose of this letter authorization is to request from the United States Nuclear Regulatory Commission (NRC) a letter authorization to ship Global Nuclear Fuel (GNF) Boiling Water Reactor (BWR) 10x10 Lead Test Assemblies (LTAs) from GNF containing several GNF FeCrAl Lead Test Rods (LTRs) which may be segmented. As part of the United States Department of Energy’s (DOE) Accident Tolerant Fuel (ATF) program, GNF is preparing fuel rod specimens with various GNF FeCrAl alloys that are considered ferritic steels for irradiation in commercial BWRs. The LTAs support material characterization and irradiated material testing for the ATF program. The evaluations presented in this letter authorization provide the safety basis for a change in approved contents of Reference 1-1, and evaluates the change relative to the approved safety evaluations documented in the Reference 1-2.

The GNF FeCrAl fuel rods are restricted to contain only Type A(F) material (enriched commercial grade uranium as defined by American Society for Testing and Materials (ASTM) C996). As discussed in Section 2.12, it is conservatively assumed that all Type A(F) GNF FeCrAl rods completely fail upon impact during the 9 meter Hypothetical Accident Conditions (HAC) drop. Supplemental criticality evaluations are provided to address the consequences of failure of these rods during HAC and to demonstrate criticality safety. All other zirconium alloy fuel rods within the assembly shall provide containment of their respective Type B(F) material as described in the existing Reference 1-2 and comply with the requirements of Reference 1-1.

While all the LTA fuel rods, both zirconium alloy and GNF FeCrAl alloy, shall be confirmed to be leak tight prior to transport, information regarding release and leak rates in Chapter 4.0 is only provided for the fuel rods containing Type B(F) material. No information regarding release or leak rates is provided for the GNF FeCrAl fuel rods, as this is not required for Type A(F) material.

The sections from Reference 1-2 that remain applicable to the subject LTAs are referenced in this letter authorization, while GNF FeCrAl supplemental evaluations are discussed in detail. For completeness, Section 1.4 provides a detailed description of the GNF FeCrAl segmented rod design. The design description is provided to compare the LTA design to an example of the currently approved content as described in Reference 1-1.

The current revision of the NRC-approved GNF quality assurance program (Reference 1-3) applies to this work, which specifically complies with Title 10 of the Code of Federal Regulations, Part 50 (10 CFR 50) Appendix B requirements and is adopted to meet the requirements of 10 CFR 71, Subpart H for transportation of radioactive material.

1.1 Introduction

The model RAJ-II package (identification number USA/9309/B(U)F-96) is approved for shipments of unirradiated BWR assemblies, in addition to loose rods (uranium carbide or generic BWR and pressurized water reactor rods).

This letter authorization seeks approval to use the RAJ-II package to ship unirradiated GNF 10x10 BWR assemblies that contain a limited quantity of GNF FeCrAl fuel rods with specific parameters outside the approved range of GNF 10x10 fuel assembly parameters described in Table 3 of Reference 1-1.


Page 9 of 70

The new content description is as follows: two 10x10 GNF BWR fuel assemblies per package, each comprised of 91-100 rods in a square array with a maximum active fuel rod length of 385 cm, where up to eight (8) of the full-length rods at controlled locations are in accordance with the GNF FeCrAl parameters included in Table 1-1. Aside from the GNF FeCrAl fuel rods, the parameters listed in Table 3 of Reference 1-1 apply. The GNF FeCrAl fuel rod controlled locations are documented in Figure 1-1 and may be of a segmented design; this is further detailed in Section 1.4. For the new content, there shall be two (2) water rods in the assembly, and the water rod locations must occupy a space equivalent to two 2x2 fuel rod equivalent spaces on a diagonal at the center of the assembly.

Table 1-1. GNF FeCrAl Parameters Outside of Reference 1-1

Affected Parameters in Table 3 of Reference 1-1

Units Current Limit (GNF 10x10)

GNF FeCrAl 10x10

UO2 Theoretical Density (% Theoretical) N/A ≤ 98% ≤ 100%

Fuel Pellet Outer Diameter (OD) cm ≤ 0.895 [[ ]]

Cladding Type N/A Zirconium Alloy GNF FeCrAl

Cladding Inner Diameter (ID) cm ≤ 0.934 [[ ]]

Cladding Thickness cm ≥ 0.038 [[ ]]

Number of GNF FeCrAl LTRs per Bundle

[[ ]] N/A 0 ≤ 8

The Criticality Safety Index (CSI), equivalent to the transport index, as defined in 10 CFR 71.59 of the RAJ-II package with a payload of two GNF BWR 10x10 LTAs in each package, modeled with additional conservatism, is 25, per Section 6.1.3.

All package descriptions contained in Section 1.1 of Reference 1-2 remain applicable to this letter authorization, except as described. No additional full-scale engineering development package tests are performed for the introduction of this new content into the package.

1.2 Package Description

The RAJ-II package is designed for shipment as a Type B(U) fissile package. The packaging description of the RAJ-II is provided in detail in Chapter 1.0 in Reference 1-2 and remains unchanged for this letter authorization. The GNF FeCrAl LTA shipment only alters the contents, as described in Section 1.1.

1.2.1 Packaging

The corresponding section of Reference 1-2 applies, with the supplemental restriction that the content of the GNF FeCrAl fuel rods shall be limited to Type A(F) quantities of radioactive material, as discussed in Chapter 4.0. The weights and dimensions of the RAJ-II package remain as listed in Table 1-1 of Reference 1-2, and the relevant drawings remain as listed in Section 5.(a)(3) of Reference 1-1.

1.2.2 Contents

For this letter authorization, a maximum of two BWR fuel assemblies are placed in each package, consistent with the shipping contents described in Reference 1-2. The packaging is


Page 10 of 70

designed and analyzed to ship fuel assembled in a 10x10 array of fuel rods without a fuel channel (unchanneled). The 10x10 fuel assembly is described in Section 1.1 and 1.4.

1.2.2.1 Maximum Quantity of Fissile and Radioactive Materials

The fuel pellets located in rods and contained in the package are uranium dioxide (UO2). The fuel assembly average enrichment is less than or equal to 5.0 wt% U-235 (the fuel rod maximum enrichment is less than or equal to 5.0 wt% U-235).

Table 1-2 of Reference 1-2 applies to the package, while the RAJ-II content radionuclide maximum concentrations for both zirconium alloy and GNF FeCrAl alloy fuel rods is provided in Table 1-2 below. The requirements for the zirconium alloy fuel rods is unchanged from Reference 1-1.

Table 1-2. RAJ-II Content Radionuclide Maximum Concentrations

Isotope Maximum Content for GNF

FeCrAl Fuel Rods Maximum Content for

Zirconium Alloy Fuel Rods

U-232 0.0001 μg/g U 0.05 μg/g U

U-234 11,000 μg/g U 2,000 μg/g U

U-235 50,000 μg/g U 50,000 μg/g U

U-236 250 μg/g U 25,000 μg/g U

Tc-99 0.01 μg/g U 5 μg/g U

Np-237 Not detectable 1.66 μg/g U

Pu-238 Not detectable 0.000062 μg/g U



Gamma Emitters Not detectable 4.4x105 MeV Bq/kg U

1.2.2.2 Chemical and Physical Properties

Chemical properties included in Section 1.2.2.2, including Table 1-4 of Reference 1-2, remain unchanged, except for the addition of GNF FeCrAl alloy as a typical structural material for the following component parts: cladding tubes and end plugs. GNF FeCrAl is also a chemically stable heat and corrosion resistant alloy. The applicable density of GNF FeCrAl is approximately 7.2 g/cm3 (0.260 lb/in3).

1.2.2.3 Nonfissile Materials: Neutron Absorbers or Moderators

The corresponding section of Reference 1-2 applies to the RAJ-II package.

1.2.2.4 Physical Configuration

1.2.2.4.1 Fuel Assembly

The corresponding section of Reference 1-2 applies to the RAJ-II package, except as noted. The CSI for the GNF FeCrAl fuel assembly is 25. See Chapter 6.0 of this letter authorization for the Criticality Safety Analysis (CSA) of this new content.


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1.2.2.4.2 Fuel Rods

This letter authorization does not request that loose rod contents be included. Therefore, this section does not apply to the letter authorization request.

1.2.2.5 Maximum Normal Operating Pressure

The maximum internal pressure of the fuel rods at room temperature and the maximum normal operating pressure of the contents are described in Section 3.3.2.

1.2.2.6 Maximum Weights of the Contents

The total weight of the payload contents for the GNF FeCrAl LTA shipments (fuel assemblies and packing material) remains unchanged from the corresponding section of Reference 1-2.

1.2.2.7 Maximum Decay Heat

The corresponding section of Reference 1-2 applies to this letter authorization request. There is no change in the decay heat load on the RAJ-II package as a result of the addition of GNF FeCrAl clad fuel rods.

1.2.3 Special Requirements for Plutonium

The corresponding section of Reference 1-2 applies to the zirconium alloy fuel rods within the assembly. There is no detectible level of plutonium within the GNF FeCrAl fuel rods. See Table 1-2.

1.2.4 Operational Features

The corresponding section of Reference 1-2 applies to this letter authorization request. There are no changes to Chapter 7.0 resulting from the introduction of limited numbers of GNF FeCrAl LTRs.

1.3 Appendix

1.3.1 RAJ-II General Arrangement Drawings

The corresponding section of Reference 1-2 applies to the use of the RAJ-II package under this letter authorization request. The package drawings are provided in Section 1.3 of Reference 1-2. No changes in the RAJ-II package are required because of the addition of FeCrAl LTRs.

1.3.2 References

1-1 “RAJ-II Certificate of Compliance No. 9309,” Docket Number 71-9309, Revision 11, Package Identification No. USA/9309/B(U)F-96, August 2017.

1-2 NEDC-33869P, RAJ-II Safety Analysis Report, Revision 9, September 2016, supplemented by Letter from B. R. Moore (GNF) to Director, Division of Spent Fuel Management (US NRC), Subject: GNF Responses to the NRC Request for Supplemental Information on the RAJ-II Transportation Package, November 28, 2016, MFN 16-088, and Letter from B. R. Moore (GNF) to Director, Division of Spent Fuel Management (US NRC), Subject: GNF Responses to the NRC Requests for Additional Information for Review of the Model No. RAJ-II, April 7, 2017, M170059.


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1-3 NEDO-11209-A, “GE Hitachi Nuclear Energy Quality Assurance Program Description,” current approved revision.

1.4 Additional GNF FeCrAl Specific Information

This section provides additional information specific to the GNF FeCrAl LTA letter authorization.

1.4.1 GNF FeCrAl LTA Description

GNF plans to ship GNF FeCrAl LTAs, with each assembly containing up to eight (8) GNF FeCrAl alloy fuel rods, which may be segmented.

Figure 1-1 illustrates the allowed locations of GNF FeCrAl LTRs within the fuel assembly lattice. Except for the GNF FeCrAl fuel rods, all other attributes are in compliance with the 10x10 fuel assembly parameters of Reference 1-1.

[[

]]

Figure 1-1. Allowable Locations for LTRs

1.4.2 GNF FeCrAl Fuel Rod Description

The GNF FeCrAl fuel assemblies are standard GNF BWR 10x10 fuel assemblies, with up to eight (8) GNF FeCrAl full length fuel rods ([[ ]], see Section 6.9) instead of zirconium alloy full length fuel rods. The GNF FeCrAl alloy material is considered a ferritic steel, and the alloying elements are summarized in Section 2.2.

The GNF FeCrAl fuel rods may be comprised of segments, as shown schematically in Figures 1-2 and 1-3. If segmented, the segments are combined to make a complete fuel rod with connecting components at both ends. Potential GNF FeCrAl lattice locations are depicted in Figure 1-1.


Page 13 of 70

[[

]]

Figure 1-2. Segment Schematic


Page 14 of 70

[[

]]

Figure 1-3. Example Segmented Rod Axial Arrangement

1.5 GNF FeCrAl Letter Authorization Comingling Restriction

This letter authorization is limited to the transport of the RAJ-II package with the new content described in Section 1.1. Packages subject to the conditions of this letter authorization shall only comingle with other RAJ-II packages transporting GNF BWR 10x10 fuel assemblies with two (2) water rods and six (6) short and eight (8) long partial length rods. The water rod locations shall occupy a space equivalent to two 2x2 fuel rod equivalent spaces on a diagonal at the center of the assembly. GNF2 is an approved content of Reference 1-1. Comingling of GNF FeCrAl LTAs and GNF2 bundles is demonstrated in the criticality safety analysis provided in Chapter 6.0.


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2.0 STRUCTURAL EVALUATION

This chapter includes evaluations demonstrating that the RAJ-II package meets applicable structural criteria with the introduction of the GNF FeCrAl BWR 10x10 fuel assembly content. The RAJ-II package, consisting of an Inner Container (IC) and an Outer Container (OC), remains unchanged from the RAJ-II SAR (Reference 2-1). Due to the introduction of the new GNF FeCrAl content, supplemental evaluations are provided to address 10 CFR 71 performance requirements regarding the change in content.

With respect to the new content, only a limited quantity of GNF FeCrAl full length Lead Test Rods (LTRs) shall be transported within each BWR 10x10 fuel assembly. Aside from the GNF FeCrAl fuel rods, all other components (specifically the zirconium alloy fuel rods) in the BWR 10x10 assembly remain unchanged from the RAJ-II SAR (Reference 2-1) and comply with the conditions of Reference 2-2.

Bounding Hypothetical Accident Condition (HAC) evaluations, using analytic techniques, are provided to address 10 CFR 71 performance requirements supporting the introduction of the GNF FeCrAl fuel rod design. The GNF FeCrAl fuel rods shall be conservatively restricted to Type A(F) quantity material, as described in Chapter 4.0 of this letter authorization.

2.1 Description of Structural Design

2.1.1 Discussion

A comprehensive discussion of the RAJ-II package design is provided in Chapter 1.0 of the RAJ-II SAR (Reference 2-1) and remains unchanged, except as stated in this letter authorization. Drawings provided in Section 1.3.1 of the RAJ-II SAR (Reference 2-1) also remain unchanged for this letter authorization.

This letter authorization is limited to the use of the RAJ-II package for transport of BWR 10x10 fuel assemblies with two (2) water rods, and the water rod locations shall occupy a space equivalent to two 2x2 fuel rod equivalent spaces on a diagonal at the center of the assembly. The fuel assembly shall include 91-100 fuel rods, with up to eight (8) GNF FeCrAl full length LTRs at controlled locations shown in Figure 2-1, and the remaining zirconium alloy BWR 10x10 fuel rods are in accordance with conditions of Table 3 of Reference 2-2.

The GNF FeCrAl full length fuel rods may be segmented and are in accordance with the parameters of Reference 2-2 Table 3, except as shown in Table 2-1.

The primary containment of the fuel rods remains unchanged from the description provided in Section 2.1.1.1 of the RAJ-II SAR (Reference 2-1), with a supplemental restriction that the content of the GNF FeCrAl fuel rod shall be limited to a Type A(F) quantity of radioactive material, as discussed in Chapter 4.0. The fuel rod end plugs are welded to the cladding with full penetration circumferential welds. This design remains unchanged from the RAJ-II SAR (Reference 2-1), and the welding design and process is qualified during fabrication to meet required material properties.


Page 16 of 70

[[

]]

Figure 2-1. Potential Locations for GNF FeCrAl Full Length Rods within BWR 10x10 Fuel Assembly

Table 2-1. Changes to Reference 2-2 Table 3 Fuel Assembly Parameters

Parameter Units Type

Fuel Assembly Type Rods GNF FeCrAl, 10x10

UO2 Density (Theoretical) N/A ≤ 100%

Number of GNF FeCrAl rods per

Bundle [[ ]]

# ≤ 8

Fuel Pellet OD cm [[ ]]

Cladding Type N/A GNF FeCrAl

Cladding ID cm [[ ]]

Cladding Thickness cm [[ ]]

Channel Thickness cm 0 (unchanneled)

Weights for the various components and the assembled packaging are unchanged from Section 2.1.3 of the RAJ-II SAR (Reference 2-1).


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2.1.1.1 Containment Structures

The primary containment for the zirconium alloy fuel rods remains unchanged from the description provided in Section 2.1.1.1 of the RAJ-II SAR (Reference 2-1). Section 2.1.1 provides a description of the confinement system required for the GNF FeCrAl fuel rods due to the supplemental Type A(F) radioactive material restriction.

All fuel rods within the GNF FeCrAl fuel assembly, whether zirconium alloy or GNF FeCrAl alloy, shall be verified to be leak tight before shipment, as discussed in Section 4.1.

2.1.1.2 Non-Containment Vessel Structures

The corresponding section of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods.

2.1.2 Design Criteria

Proof of performance for the RAJ-II package is achieved by a combination of analytic and empirical evaluations. The acceptance criteria for analytic assessments are in accordance with 10 CFR 71 and the applicable regulatory guides. The acceptance criterion for empirical assessments remains unchanged from the RAJ-II SAR (Reference 2-1); however, supplemental evaluations are provided to support the introduction of the new content. Package deformations obtained from certification testing remain unchanged from the RAJ-II SAR (Reference 2-1) and are considered in subsequent thermal, shielding, and criticality evaluations.

2.1.2.1 Analytic Design Criteria (Allowable Stresses)


See Section 2.12 for a supplemental impact analysis of the new content.

2.1.2.2 Containment Structures

See Section 2.1.1.1.

2.1.2.3 Non-Containment Structures


2.1.2.4 Miscellaneous Structural Failure Modes

2.1.2.4.1 Brittle Fracture

By avoiding the use of ferritic steels in the RAJ-II package, IC and OC brittle fracture concerns are precluded. Specifically, most primary structural components are fabricated of austenitic stainless steel. Because this material does not undergo a ductile-to-brittle transition in the temperature range of interest (above -40ºF), it is safe from brittle fracture.

The closure bolts used to secure the IC and OC lids are stainless steel socket head cap screws ensuring that brittle fracture is not of concern. Other critical fasteners used in the RAJ-II package assembly provide redundancy and are made from stainless steel, again eliminating brittle fracture concerns, and remain unchanged from the corresponding section in the RAJ-II SAR (Reference 2-1).


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See Section 2.12 for further detail regarding GNF FeCrAl material.

2.1.2.4.2 Extreme Total Stress Intensity Range

The corresponding section of the RAJ-II SAR (Reference 2-1) applies to use of the RAJ-II package with the addition of GNF FeCrAl fuel rod content; Section 2.12 addresses the GNF FeCrAl fuel rod.

2.1.2.4.3 Buckling Assessment

The buckling assessment provided in the corresponding section of the RAJ-II SAR (Reference 2-1) applies to the use of the RAJ-II package with the addition of GNF FeCrAl fuel rod content. See Section 2.12 for a discussion of the GNF FeCrAl fuel rods.

2.1.3 Weights and Centers of Gravity


2.1.4 Identification of Codes and Standards for Package Design

The corresponding section of the RAJ-II SAR (Reference 2-1) applies to this letter authorization request, except where noted below for the GNF FeCrAl fuel rods.

The GNF FeCrAl fuel rod isotopic content is defined in Chapter 4.0.

The fuel cladding, whether zirconium alloy or GNF FeCrAl alloy, due to its service in the reactor and need for high integrity, is designed and fabricated to standards that exceed those required by ASME Section III Subsection ND. Chapter 6.0 demonstrates that the packaging remains subcritical. The codes used in package fabrication are called out on the drawings in Section 1.3.1 of the RAJ-II SAR (Reference 2-1). The sheet metal construction of the package is unchanged from the RAJ-II SAR (Reference 2-1).

2.1.4.1 JIS/ASTM Comparison of Materials


2.1.4.2 JIS/ASME Weld Comparison


2.1.4.3 JIS/JSNDI/ASNT Non-Destructive Examination Personnel Qualification and Certification Comparison


2.2 Materials

2.2.1 Material Properties and Specifications

The major structural components (i.e., the OC and IC walls, supports, and attachment blocks) remain unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1). The following materials performing a structural function also remain unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1): lumber (bolster), balsa (shock


Page 19 of 70

absorber), paper honeycomb (shock absorber), alumina silicate (thermal insulator), polyethylene foam (cushioning material), and zirconium alloy (fuel rod cladding). However, the GNF FeCrAl alloy is introduced as an additional fuel rod cladding and end plug material within this letter authorization. For mechanical properties of the unchanged components, see Table 2-2 and Table 2-3 of the RAJ-II SAR (Reference 2-1). For the nominal material composition of GNF FeCrAl, see Table 2-2. Chemical variation within each alloy of GNF FeCrAl shall be specified in line with standard industry practice and applicable product tolerance requirements.

The drawings presented in Section 1.3.1 of the RAJ-II SAR (Reference 2-1) delineate the specific material(s) used for each RAJ-II package and remain unchanged for this letter authorization.

Table 2-2. GNF FeCrAl Alloy Nominal Material Composition (wt%)

[[

]]

2.2.2 Chemical, Galvanic, or Other Reactions

The major materials of construction of the RAJ-II packaging (i.e., austenitic stainless steel, polyethylene foam, alumina thermal insulator, resin impregnated paper honeycomb, lumber (hemlock and balsa), and natural rubber), remain unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1).

2.2.2.1 Content Interaction with Packaging Materials of Construction

The materials of construction of the RAJ-II packaging are checked for compatibility with the materials that make up the contents or fuel to be shipped in the RAJ-II. The primary materials of construction of the fuel assembly that could come in contact with the packaging are the stainless steel and the zirconium alloy material used for the fuel rod cladding. The zirconium alloy, stainless steel, and Ni-Cr-Fe alloy, which form a passivated oxide film on the surface under normal atmosphere with slight moisture, are essentially stable and remain unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1).

The only new material introduced in this letter authorization is the GNF FeCrAl fuel rod cladding and end plugs. GNF FeCrAl is an iron-based steel and therefore does not present any new or significantly different performance deficiency relative to existing materials that the RAJ-II package is constructed from with regard to chemical, galvanic or other reactions within the temperature range applicable to NCT and HAC. GNF FeCrAl is chemically stable, stress corrosion cracking resistant, and passivates when subjected to an oxidizing atmosphere. GNF FeCrAl is therefore compatible with all the potential RAJ-II packaging materials it comes in contact with.

2.2.3 Effects of Radiation on Materials

Because this is an unirradiated fuel package, the radiation to the packaging material is insignificant and remains unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1). Furthermore, the primary materials of construction and containment, austenitic stainless steel and the zirconium alloy or GNF FeCrAl alloy fuel cladding, are highly resistant to radiation.


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2.3 Fabrication and Examination

2.3.1 Fabrication

The RAJ-II packaging is fabricated as described in the corresponding section of the RAJ-II SAR (Reference 2-1).

The containment boundary, the fuel rod cladding, is fabricated to standards that exceed Section VIII of the ASME Boiler and Pressure Vessel Code (B&PVC) due to the service requirements of the fuel in reactors, and remains unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1), even considering the introduction of the additional GNF FeCrAl alloy material.

2.3.2 Examination

The RAJ-II packaging is examined as described in the corresponding section of the RAJ-II SAR (Reference 2-1).

2.4 General Requirements for All Packages

The corresponding section and subsections of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods.

2.5 Lifting and Tie-Down Standards for All Packages

The corresponding section and subsections of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods.

2.6 Normal Conditions of Transport

The corresponding section of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods, except as noted. Supplemental analytical evaluations for the new GNF FeCrAl under HAC are provided in Section 2.7 and are considered to bound NCT.

Discussions regarding brittle fracture and fatigue are presented in Section 2.7 and are shown to not be the limiting cases for the RAJ-II package design. The ability of the welded containment, the zirconium alloy fuel rod cladding, to remain leak-tight is unchanged from Chapter 4.0 of the RAJ-II SAR (Reference 2-1), while supplemental analytical evaluations are provided in Section 2.7.

2.6.1 Heat


2.6.1.1 Summary of Pressures and Temperatures


The maximum temperature of 77ºC (171ºF) remains unchanged.

The resulting pressure at the maximum temperature remains unchanged from the RAJ-II SAR (Reference 2-1) for Boiling Water Reactor (BWR) zirconium alloy fuel types. See Section 2.12 for a discussion of GNF FeCrAl alloy fuel rods.


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2.6.1.2 Differential Thermal Expansion

The corresponding section of the RAJ-II SAR (Reference 2-1) applies to the package and GNF BWR 10x10 content. See Section 2.12 for a discussion of the GNF FeCrAl fuel rod.

2.6.1.3 Stress Calculations

Because the temperatures and pressures generated under NCT are well below the design conditions for reactor fuel, no specific calculations were performed for the fuel containment.

2.6.1.4 Comparison with Allowable Stresses

The NCT are well below the operating conditions of the fuel. Therefore, no comparison to allowable stresses was performed.

2.6.2 Cold


2.6.3 Reduced External Pressure


2.6.4 Increased External Pressure


2.6.5 Vibration


No supplemental vibration testing is performed for the GNF FeCrAl fuel rods.

2.6.6 Water Spray


2.6.7 Free Drop

The corresponding section of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods. Bounding HAC supplemental evaluations are provided in Section 2.7 for the introduction of the GNF FeCrAl fuel rods.

2.6.8 Corner Drop


2.6.9 Compression



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2.6.10 Penetration


2.7 Hypothetical Accident Conditions

The RAJ-II package, when subjected to the sequence of HAC tests specified in 10 CFR 71.73, is shown to meet the performance requirements specified in Subpart E of 10 CFR 71. The primary proof of performance for the HAC tests is via the use of full-scale testing, and this letter authorization remains unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1).

A certification test unit (CTU) was free dropped and puncture tested to confirm that both the IC and OC protected the fuel and allowed containment to be maintained after a worst-case HAC sequence. Another CTU was free dropped from 9 meters on its end with the fuel maintaining containment after the drop. Observations from testing confirm the conservative nature of the deformed geometry assumptions used in the criticality assessment provided in Chapter 6.0, and remain unchanged from the RAJ-II SAR (Reference 2-1).

A discussion on the introduction of the GNF FeCrAl fuel rods into the GNF BWR 10x10 bundle is provided in Section 2.12.

2.7.1 Free Drop


2.7.2 Crush


2.7.3 Puncture


2.7.4 Thermal


2.7.4.1 Summary of Pressures and Temperatures

The maximum predicted HAC temperature for the fuel is 648°C (921 K, 1,198°F) during the fire event and remains unchanged from the corresponding section of the RAJ-II SAR (Reference 2-1). The zirconium alloy fuel rod is designed to withstand a minimum temperature of 800°C without bursting. A discussion of the GNF FeCrAl rods is provided in Section 2.12.

2.7.4.2 Differential Thermal Expansion

The cladding of the fuel, which serves as the containment, is not stressed due to differential thermal expansion between the pellet and cladding; see Section 2.6.1.2 for supplemental evaluations for the new content. The fuel cladding is not restricted by the packaging and hence will not develop any significant differential thermal expansion stresses. The packaging itself is


Page 23 of 70

made of the same metal (austenitic stainless steel) eliminating any significant stresses due to differential thermal expansion.

2.7.4.3 Stress Calculations

Stress calculations for the controlling hoop stress for the fuel cladding that provides containment is provided in Chapter 3.0.

2.7.4.4 Comparison with Allowable Stresses


2.7.5 Immersion—Fissile Material

Subpart F of 10 CFR 71 requires performing an immersion test for fissile material packages in accordance with the requirements of 10 CFR 71.73(c)(5). The criticality evaluation presented in Chapter 6.0 assumes optimum hydrogenous moderation of the contents, thereby conservatively addressing the effects and consequences of water in-leakage. See Chapter 6.0 for a discussion of the GNF FeCrAl fuel rods.

2.7.6 Immersion—All Packages

See Section 2.7.5. Otherwise, the corresponding section of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods.

2.7.7 Deep Water Immersion Test (for Type B Packages Containing More than 105 A2)


2.7.8 Summary of Damage

The corresponding section of the RAJ-II SAR (Reference 2-1) does not change as a result of the addition of GNF FeCrAl fuel rods, except as stated. Subsequent helium leak testing is not performed for the GNF FeCrAl fuel rods, which are limited to Type A(F) radioactive material.

2.8 Accident Conditions for Air Transport of Plutonium


2.9 Accident Conditions for Fissile Material Packages for Air Transport


2.10 Special Form


2.11 Fuel Rods

In each event evaluated above either by analysis or by test, the unirradiated fuel rods were protected by the RAJ-II package so that they sustained no significant damage. Fuel rod cladding is considered to provide containment of radioactive material under both normal and accident test conditions for zirconium alloy fuel rods containing Type B(F) radioactive material.


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GNF FeCrAl alloy fuel rods containing Type A(F) radioactive material are discussed in Chapter 4.0.

Discussion of fuel rods and their ability to maintain sufficient mechanical integrity is described in the corresponding section of the RAJ-II SAR (Reference 2-1) for the Type B(F) fuel rods and Section 2.12 for the Type A(F) GNF FeCrAl fuel rods.

2.12 GNF FeCrAl Bundle 9m Drop Evaluation

Sections 2.12.2 and 2.12.3 of the RAJ-II SAR (Reference 2-1) do not change as a result of the addition of GNF FeCrAl fuel rods.

During a 9 meter drop of the RAJ-II package with up to eight (8) GNF FeCrAl rods, it is conservatively assumed that all Type A(F) GNF FeCrAl rods completely fail upon impact. As a result, no structural, thermal, and containment evaluations are performed on the GNF FeCrAl rods. Safety and regulatory compliance is demonstrated through the criticality evaluation in Chapter 6.0. The FeCrAl rod failure scenario does not detrimentally affect the surrounding Type B(F) zirconium alloy rods.

2.13 APPENDIX

2.13.1 References


2-2 “RAJ-II Certificate of Compliance No. 9309,” Docket Number 71-9309, Revision 11, Package Identification No. USA/9309/B(U)F-96, August 2017.


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3.0 THERMAL EVALUATION

This chapter provides an evaluation of the RAJ-II package to protect the fuel during varying thermal conditions. The existing description in Reference 3-1 applies to the RAJ-II package. A supplemental evaluation is provided for the new contents, GNF FeCrAl fuel rods, which are to be transported within each 10x10 BWR fuel assembly. The GNF FeCrAl fuel rods may be segmented. All other 10x10 BWR fuel rods are in compliance with the existing description. Those sections affected by the differences between the new content and currently approved contents contain evaluations to demonstrate compliance with relevant criteria, and those sections unaffected by these differences are stated as such.

3.1 Description of Thermal Design

There is no change in this section as a result of the addition of GNF FeCrAl fuel rods.

3.1.1 Design Features

The GNF FeCrAl fuel rods are restricted to Type A materials. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during Hypothetical Accident Conditions (HAC). As a result, no thermal evaluation is performed on the FeCrAl fuel rods

All other 10x10 BWR Zr-clad fuel rods are in compliance with the existing description. Section 3.3 and Section 3.4 demonstrate acceptable thermal performance during all conditions of transport.

3.1.2 Content’s Decay Heat

There is no change in the decay heat load on the RAJ-II package as a result of the addition of GNF FeCrAl fuel rods.

3.1.3 Summary Tables of Temperatures

There is no change in the summary tables of temperatures as a result of the addition of GNF FeCrAl fuel rods. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

3.1.4 Summary Tables of Maximum Pressures

There is no change in the summary tables of pressures as a result of the addition of GNF FeCrAl fuel rods. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

3.2 Material Properties and Component Specifications

3.2.1 Material Properties

There is no change in the RAJ-II package material properties as a result of the addition of GNF FeCrAl fuel rods.

3.2.2 Component Specifications

Supplemental information is summarized in Table 3-1 regarding the lower melting point temperature of GNF FeCrAl fuel rods within the 10x10 BWR fuel assembly. There is no change in the other lower melting point temperatures as a result of the addition of GNF FeCrAl fuel rods.


Page 26 of 70

As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

Table 3-1. GNF FeCrAl Melting Point

Material Lower Melting

Point Temperature

GNF FeCrAl 1,450°C (2,642°F)

3.3 Thermal Evaluation Under Normal Conditions of Transport

3.3.1 Heat and Cold

There is no change in the heat and cold inputs as a result of the addition of GNF FeCrAl fuel rods.

3.3.1.1 Maximum Temperatures

There is no change in the maximum temperatures as a result of the addition of GNF FeCrAl fuel rods.

3.3.1.2 Minimum Temperatures

There is no change in the minimum temperatures as a result of the addition of GNF FeCrAl fuel rods.

3.3.2 Maximum Normal Operating Pressure

There is no change in maximum normal operating pressure for all other 10x10 BWR Zr-clad fuel rods. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

3.4 Thermal Evaluation Under Hypothetical Accident Conditions

The addition of GNF FeCrAl fuel rods does not affect the general description of the HAC thermal analysis assumptions and methodology.

3.4.1 Initial Conditions

The addition of GNF FeCrAl fuel rods does not affect the initial conditions.

3.4.2 Fire Test Conditions

The addition of GNF FeCrAl fuel rods does not affect the fire test conditions or the heat transfer coefficient during the fire event or during the post-fire period.

3.4.3 Maximum Temperatures and Pressure

3.4.3.1 Maximum Temperatures

There are no changes to the maximum temperatures described in Reference 3-1. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.


Page 27 of 70

3.4.3.2 Maximum Internal Pressure

There are no changes to the maximum internal pressure described in Reference 3-1. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

3.4.3.2.1 Maximum Internal Pressure: GNF BWR

There are no changes to the existing description in Reference 3-1. As discussed in Chapter 2.0, integrity of the GNF FeCrAl fuel rods is not credited during HAC. As a result, no thermal evaluation is performed on the FeCrAl fuel rods.

3.4.3.2.2 Maximum Internal Pressure: Non-BWR

There are no changes to the existing description in Reference 3-1. This non-BWR subsection is not applicable to the GNF FeCrAl fuel rods.

3.4.4 Maximum Thermal Stresses


3.4.4.1 Maximum Thermal Stress: BWR


3.4.4.2 Maximum Thermal Stress: non-BWR

There are no changes to the existing description in Reference 3-1. This non-BWR subsection is not applicable to the GNF FeCrAl fuel rods.

3.4.5 Accident Conditions for Fissile Material Packages for Air Transport

The existing RAJ-II container approval does not allow for air transport. No change to that basis is requested for the shipment of GNF FeCrAl rods in the RAJ-II package.

3.5 Appendix

3.5.1 References


3.5.2 ANSYS Input File Listing

There are no changes to the existing ANSYS input file in Reference 3-1.


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3.5.3 NCT Transient Analysis

There are no changes to the existing NCT transient analysis in Reference 3-1.


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4.0 CONTAINMENT

This chapter presents evaluations demonstrating that the RAJ-II package meets applicable containment criteria with the introduction of limited numbers of GNF FeCrAl LTRs. Supplemental information is provided for the limited quantity of GNF FeCrAl full length fuel rods within each 10x10 bundle. The GNF FeCrAl fuel rods are restricted to Type A quantity material. All other 10x10 fuel rods are in compliance with the existing description in Reference 4-1. Those sections affected by the differences between the GNF FeCrAl fuel rods and the currently approved contents contain evaluations to demonstrate compliance with relevant criteria, and those sections unaffected by these differences are stated as such.

4.1 Description of the Containment System

This letter authorization is limited to the use of the RAJ-II package for transport of GNF 10x10 fuel assemblies with a limited number of GNF FeCrAl LTRs. The containment description of Section 4.1 in Reference 4-1 applies to this letter authorization, with a supplemental restriction for the limited quantity of GNF FeCrAl full length fuel rods within each 10x10 bundle. The containment system for all 10x10 fuel rods is in compliance with the description of Reference 4-1, Section 4.1, except as noted for the GNF FeCrAl fuel rods.

In this letter authorization, as with Reference 4-1, the RAJ-II package includes unirradiated fuel assemblies with low enriched uranium nuclear reactor fuel (GNF FeCrAl fuel assemblies shall be unchanneled). While the zirconium alloy fuel rods are in compliance with Reference 4-1, no reprocessed material is permitted within the GNF FeCrAl fuel rods. Thus, the content of the GNF FeCrAl fuel rods shall be restricted to the ASTM C996 standard of enriched commercial grade (non-reprocessed) component allowances illustrated in Table 4-1.

Table 4-1. RAJ-II Content Radionuclide Maximum Concentrations

Radionuclide Maximum Content for GNF

FeCrAl Fuel Rods Maximum Content for

Zirconium Alloy Fuel Rods

U-232 0.0001 μg/g U 0.05 μg/g U

U-234 11,000 μg/g U 2,000 μg/g U

U-235 50,000 μg/g U 50,000 μg/g U

U-236 250 μg/g U 25,000 μg/g U

Tc-99 0.01 μg/g U 5 μg/g U

Np-237 Not detectable 1.66 μg/g U




Gamma Emitters Not detectable 4.4x105 MeV Bq/kg U

As per the requirements of 10 CFR 71.22, the GNF FeCrAl fuel rods shall be considered Type A(F), as opposed to the Type B(F), which applies to all other 10x10 Zr-clad fuel rods. Although Type A(F) packages are only required to maintain criticality safety geometry (which is demonstrated in Chapter 6.0), the rods shall be prepared for transport in a similar manner to that described in Reference 4-1, with cladding and a welded endplug encapsulating the radioactive ceramic pellets. Additionally, all fuel rods (zirconium alloy and GNF FeCrAl alloy) shall be leak tested to the same leak tight criteria per the approved methods of Reference 4-1.


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However, with the Type A(F) restriction, no further leak testing or allowable release rates are provided for the GNF FeCrAl letter authorization for subsequent conditions of transport.

4.2 Containment under Normal Conditions of Transport

The existing description in Reference 4-1 applies to the package. The GNF FeCrAl fuel rods are restricted to Type A quantity material, while all other 10x10 fuel rods are in compliance with the existing description of Reference 4-1. Per the requirements of 10 CFR 71.22, only critical geometry must be maintained and, as such, no further calculations for containment under NCT are provided. Acceptable criticality safety geometry during NCT is demonstrated in Chapter 6.0. No further discussion is required in this section for the GNF FeCrAl material.

4.3 Containment under Hypothetical Accident Conditions

The existing description in Reference 4-1 applies to the package. The GNF FeCrAl fuel rods are restricted to Type A quantity material, while all other 10x10 fuel rods are in compliance with the existing description of Reference 4-1. Per the requirements of 10 CFR 71.22, only critical geometry must be maintained and, as such, no further calculations for containment under HAC are provided. Acceptable criticality safety geometry during HAC is demonstrated in Chapter 6.0. No further discussion is required in this section for the GNF FeCrAl material.

4.4 Leakage Rate Tests for Type B Packages

The existing description in Reference 4-1 applies to the package. The GNF FeCrAl fuel rods are restricted to Type A quantity material, while all other 10x10 fuel rods are in compliance with the existing description of Reference 4-1. Note that the GNF FeCrAl fuel rods shall be leak tested to the same leak tight criteria per the approved methods of Reference 4-1 prior to transport only.

4.5 Appendix

4.5.1 Determination of Allowable Leak Rates

The existing description in Reference 4-1 applies to the package. Because the GNF FeCrAl fuel rods are restricted to Type A quantity material, no allowable release rate is provided for the GNF FeCrAl letter authorization for subsequent conditions of transport.

4.5.2 Summary

There is no change in the conclusions stated in Reference 4-1 resulting from the addition of the GNF FeCrAl fuel rods.

4.5.3 References



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5.0 SHIELDING EVALUATION

There are no changes to this section as a result of the introduction of a limited number of GNF FeCrAl lead test fuel rods. Thus, Chapter 5.0 of the RAJ-II Safety Analysis Report (Reference 5-1) remains applicable.

5.1 References



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6.0 CRITICALITY EVALUATION

This chapter presents evaluations demonstrating that the RAJ-II package meets applicable criticality criteria with the introduction of GNF2 LTAs containing several GNF FeCrAl LTRs. The FeCrAl LTRs have a ferritic steel alloy cladding and additional physical characteristics that are outside of the approved RAJ-II Certificate of Compliance (CoC) Number 9309 Revision 11 (Reference 6-1).

The criticality evaluation sections affected by the differences between the new content (GNF FeCrAl) and the currently approved contents contain evaluations to demonstrate compliance with relevant criteria. Those sections unaffected by these differences are stated as such. The GNF FeCrAl LTA fuel assembly design is compared to the most similar approved contents reference case of the RAJ-II Safety Analysis Report (SAR) Revision 9, as supplemented (Reference 6-2) and the RAJ-II CoC (Reference 6-1). Because the GNF FeCrAl LTA is a 10x10 lattice, the most similar reference case is the GNF2 10x10 fuel assembly.

In this letter authorization request, the RAJ-II package continues to include unirradiated fuel assemblies which consist of fuel rods that provide containment (zirconium alloy cladding),confinement (GNF FeCrAl cladding), an IC, and an OC. Existing analyses using analytical techniques demonstrating compliance to the requirements of 10 CFR 71 for NCT and HAC, included in Reference 6-2, are referenced as applicable.

The objective of this analysis is to evaluate criticality safety for the RAJ-II package loaded with GNF FeCrAl LTAs and/or standard GNF2 fuel assemblies. The CSA for the RAJ-II package was performed for several types of GNF BWR fuel designs, including 8x8, 9x9 and 10x10 fuel assemblies, in the RAJ-II SAR (Reference 6-2). Most design parameters (important to criticality safety) of the GNF FeCrAl LTA are either identical to or bounded by the current GNF 10x10 fuel assembly in the RAJ-II SAR (Reference 6-2), but the design configurations for LTRs are beyond the limitations established by Table 6-1 of the RAJ-II SAR (Reference 6-2). Therefore, the potential effect of these GNF FeCrAl LTR parameters on RAJ-II package criticality safety are evaluated and will support mixed shipments of both GNF2 assemblies containing FeCrAl LTRs and standard GNF2 fuel assemblies.

This analysis only evaluates the package array under HAC, which was demonstrated to be the most reactive configuration and was used to determine the CSI in the RAJ-II SAR (Reference 6-2). The HAC configuration in this letter authorization for the RAJ-II package is the same as that described in Section 6.3.1.1.2 of the RAJ-II SAR (Reference 6-2), except for the fuel type, limiting rod-to-rod pitch, and the size of the HAC package array.

The GNF FeCrAl LTRs will be conservatively limited to only Type A material, for which only confinement is required. Therefore, this CSA provides supplemental analyses to demonstrate criticality safety under a loss of containment event. See Section 6.6.2.2 for additional information.

6.1 Description of Criticality Design

Section 6.1 of the RAJ-II SAR (Reference 6-2) remains largely unaffected by this letter authorization except for those key parameters included in Table 6-1. Table 6-1 is a comparison of the differences between the GNF FeCrAl LTA and the parameters listed in Table 6-1 of the RAJ-II SAR (Reference 6-2).


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Table 6-1. LTA Parameters Outside of the RAJ-II SAR

Affected Parameters in Table 6-1 of the RAJ-II SAR (Reference 6-2)

Current Limit LTA Valuea

UO2 Theoretical Density ≤98% ≤100%

Fuel Pellet Outer Diameter ≤0.895 cm [[ ]]

Cladding Material Zircaloy FeCrAl

Cladding ID ≤0.934 cm [[ ]]

Cladding Thickness ≥0.038 cm [[ ]]

Number of GNF FeCrAl LTRs per Bundle [[ ]] 0 ≤8

a For conservatism, this CSA will use the most bounding (limiting) parameter from the LTA and/or the RAJ-II SAR (Reference 6-2).

6.1.1 Design Features

There are no changes to the design features of the RAJ-II package resulting from the addition of GNF FeCrAl LTRs. Thus Section 6.1.1 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.1.2 Summary Table of Criticality Evaluation

The criticality evaluation summary for BWR 8x8, 9x9, and 10x10 fuel assemblies and fuel rods, along with Canada deuterium uranium and generic pressurized water reactor fuel rods, is described in Table 6-3 of the RAJ-II SAR (Section 6.1.2 of Reference 6-2). There is no intention to ship loose GNF FeCrAl LTRs and it is not part of the requested letter authorization.

The criticality evaluation in the RAJ-II SAR (Reference 6-2) covers both a single package and a package array under NCT and HAC. The GNF 10x10 HAC package array is demonstrated as the bounding transport configuration. Therefore, this analysis only performs criticality evaluations for the RAJ-II package array containing GNF FeCrAl LTAs and GNF2 fuel assemblies under HAC as configured in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2).

Table 6-2 summaries the criticality evaluation of the bounding HAC array for the RAJ-II package containing the most limiting configuration of GNF FeCrAl LTAs and GNF2 fuel assemblies (the bounding GNF letter authorization assembly). The effective neutron multiplication factor (keff) is below the maximum keff Upper Subcritical Limit (USL) of [[ ]]. The USL provided is described in Section 6.10 of the RAJ-II SAR (Reference 6-2).

Table 6-2. Criticality Evaluation Summary for RAJ-II GNF FeCrAl LTA and GNF2 Configurations

Case Maximum

keff

Maximum keff + 2

∆ keff to USL [[ ]]

2x1x2 HAC Package Array with Type A GNF FeCrAl LTRs

0.91578 0.00026 0.91630 [[ ]]


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6.1.3 Criticality Safety Index

Per 10 CFR 71.59, the CSI is defined as 50/N, where the number of undamaged packages in an array is 5N, and the number of damaged packages in an array is 2N. Table 6-3 lists the CSI for this letter authorization.

Table 6-3. Summary of Criticality Safety Index for RAJ-II GNF FeCrAl LTA and GNF2 Configurations

Case 2N N CSI

2x1x2 HAC Package Array 4 2 25

Based on the analysis results in Section 6.6, it is concluded that the RAJ-II package meets the regulatory requirements for mixed shipments of both GNF FeCrAl LTA and standard GNF2 fuel assemblies with a maximum U-235 enrichment of 5.0 Weight Percent (wt%) without crediting gadolinia. As shown in Table 6-3, criticality safety is demonstrated for a shipment of up to 24 RAJ-II packages containing GNF FeCrAl LTA or standard GNF2 or mixed fuel assemblies under the worst credible HAC.

6.2 Fissile Material Contents

GNF FeCrAl LTRs are conservatively limited to Type A fissile material. The specific fissile material contents for GNF FeCrAl LTRs are provided in Section 2.2. There are no additional changes to this section; thus Table 6-5 in Section 6.2 of the RAJ-II SAR (Reference 6-2) remains applicable for all fuel rods in this CSA (i.e., fuel rods with zirconium alloy or GNF FeCrAl alloy cladding).

6.3 General Considerations

Because of the similarity of the GNF FeCrAl LTA design to other GNF 10x10 fuel bundles, this analysis only performs criticality evaluations for the RAJ-II package array containing the most limiting assembly under HAC as configured in the RAJ-II SAR (Reference 6-2). For increased confidence in criticality safety, a more conservative configuration is analyzed and demonstrated to remain below the USL. This configuration combines the worst parameters from the GNF 10x10 fuel assembly in Table 6-1 of the RAJ-II SAR (Reference 6-2) and the parameters listed in Table 6-1 to generate a bounding GNF letter authorization assembly. Additional conservatisms are applied to the rod-to-rod pitch for hypothetical fuel relocations due to a complete failure of the GNF FeCrAl LTRs, as described in Section 6.3.4.5. The GNF letter authorization assembly will bound both GNF FeCrAl LTA and GNF2 assemblies.

6.3.1 Model Configuration

The RAJ-II package array HAC model considered in this analysis includes a 7x1x7 (2N=49) array and a 2x1x2 (2N=4) array of RAJ-II packages. The 2x1x2 RAJ-II package array is used to demonstrate that the proposed CSI in Table 6-3 will remain below the USL for hypothetical fuel relocations due to a complete failure of the 8 GNF FeCrAl LTRs. The 7x1x7 RAJ-II array configuration is used for the generic demonstration of key concepts in Sections 6.13 and 6.14 that are not affected by the array size.

The RAJ-II package is comprised of an IC and an OC fabricated from stainless steel. The IC is lined with Polyethylene Cushioning Foam (PCF). The fuel assembly rests against the PCF at a fixed position in each IC fuel compartment. The IC, with the encased alumina-silicate thermal


Page 35 of 70

insulation between the inner and outer walls, is positioned within the OC. Some of the packaging materials, such as honeycomb shock absorbers and wood, are not explicitly modeled. This is acceptable as these do not provide as effective neutron moderation as water. Figure 6-1 is a cross-sectional illustration of the RAJ-II HAC model (similar to Figure 6-8 in the RAJ-II SAR (Reference 6-2)). A detailed description of the RAJ-II package array HAC model is provided in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2).

Shipping loose GNF FeCrAl LTRs is not part of the requested content for this letter authorization. Therefore, Section 6.3.1.3 (and applicable subsections) of the RAJ-II SAR (Reference 6-2) is not applicable. [[

]]

Figure 6-1. RAJ-II Cross-Section HAC Model without Gadolinia Rods

6.3.2 Materials Properties

Material properties are described in further detail in Section 6.3.2 of the RAJ-II SAR (Reference 6-2). The changes to the UO2 constituents are summarized in Table 6-4 due to changes in material density. The material properties for GNF FeCrAl LTRs are summarized in Section 2.2.


Page 36 of 70

Table 6-4. Material Specifications for the GNF FeCrAl LTA RAJ-II Letter Authorization

Material Density (g/cm3)

Constituent Atomic Density (atoms/b-cm)

U(5.0)O2 100% Theoretical

Density 10.96

U-235 U-238 O-16

1.2376x10-3

2.3218x10-2

4.8911x10-2

6.3.3 Computer Codes and Cross-Section Libraries

KENO-VI with the ENDF/B-VII continuous-energy neutron cross-section library was used for this analysis (Reference 6-3). There are no changes to this section, thus Section 6.3.3 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4 Demonstration of Maximum Reactivity

Maximum reactivity for GNF 10x10 assemblies is demonstrated in Section 6.3.4 in the RAJ-II SAR (Reference 6-2) through studies of the following factors on reactivity of the RAJ-II NCT and/or HAC arrays:

(1) Fuel Assembly Orientation (RAJ-II SAR Section 6.3.4.1) (2) Fuel Assembly Gadolinia Rod Loading Pattern (RAJ-II SAR Section 6.3.4.2) (3) Fuel Assembly Channel (RAJ-II SAR Section 6.3.4.3) (4) Polyethylene Mass (RAJ-II SAR Section 6.3.4.4) (5) Fuel Rod Pitch Sensitivity (RAJ-II SAR Section 6.3.4.5) (6) Fuel Pellet Diameter Sensitivity (RAJ-II SAR Section 6.3.4.6) (7) Fuel Rod Clad Thickness Sensitivity (RAJ-II SAR Section 6.3.4.7) (8) Worst Case Parameter Fuel Designs (RAJ-II SAR Section 6.3.4.8) (9) Part Length Fuel Rod (RAJ-II SAR Section 6.3.4.9) (10) Moderator Density (RAJ-II SAR Section 6.3.4.10) (11) Material Distribution Reactivity (RAJ-II SAR Section 6.3.4.11) (12) Inner Container Partial Flooding (RAJ-II SAR Section 6.3.4.12) (13) RAJ-II Container Spacing (RAJ-II SAR Section 6.3.4.13) (14) Methodology Justification for Uniform Enrichment Distribution, As-Built Part Length

Rod Configurations, and Annular Wrapping of Polyethylene Packing Materials (RAJ-II SAR Section 6.3.4.14)

This letter authorization provides the following supplemental maximum reactivity studies to support up to (≤) 8 GNF FeCrAl LTRs [[ ]].

(1) Fuel Assembly Gadolinia-Urania Rod Study for GNF FeCrAl LTA (Section 6.3.4.2) (2) Fuel Rod Pitch Sensitivity for 8 Type A GNF FeCrAl LTRs (Section 6.3.4.5) (3) Hypothetical Fuel Relocation of 8 GNF FeCrAl LTRs (Section 6.6.2.2) (4) Limiting Pellet Diameter (Section 6.13.3) (5) Limiting Fuel Rod Cladding Thickness (Section 6.13.4) (6) Limiting Cladding Material (Section 6.13.5) (7) Impact of Segmented GNF FeCrAl LTRs (Section 6.13.6)

Due to the similarity of the GNF FeCrAl LTAs to the RAJ-II SAR (Reference 6-2) GNF 10x10 assembly in structure and nuclear design, the HAC array model configuration based on the above studies for demonstration of maximum reactivity in the RAJ-II SAR (Reference 6-2)


Page 37 of 70

remains applicable to this analysis, as confirmed by the results in the following subsections of this letter authorization request. The most limiting RAJ-II package array HAC model parameters for this letter authorization are summarized in Table 6-5.

Table 6-5. Limiting HAC Model Parameters for RAJ-II Package Array Containing the Bounding GNF Letter Authorization Fuel Assembly

Parameter Unit Value or Assumption Reference

Max U-235 Pellet Enrichment wt% 5.0 Section 6.3.4.2

Limiting Lattice Enrichment Zone with Gadolinia-Urania (Gd2O3-UO2)

wt% 5.0 wt% U-235 without Gd2O3-

UO2 rods Section 6.3.4.2

UO2 Density g/cm3 10.96 (100% theoretical density) -

Fuel Pellet Outer Diameter cm [[ ]] Section 6.13.3

Fuel Rod Outer Diameter cm 1.01 Table 6-1 of RAJ-II SAR

Cladding Thickness cm [[ ]] Section 6.13.4

Active Fuel Length cm 385 (full length rod) Table 6-1 of RAJ-II SAR

Fuel Rod Pitch cm [[ ]] Section 6.3.4.5

Number of GNF FeCrAl Rods - ≤ 8 Section 6.9

Fuel Channel Thickness cm Any Table 6-1 of RAJ-II SAR

IC Dimensions

(Length x Width x Height) cm 459.06 × 45.88 x 28.05 Figure 6-7 of RAJ-II SAR

OC Dimensions

(Length x Width x Height) cm 502.03 x 71.93 x 61.75 Figure 6-6 of RAJ-II SAR

PCF Thickness cm 1.1 (optimal thickness) Section 6.3.4.11

Reflector (full density water) cm 30.48 (all sides) Section 6.3.1.2.2 of RAJ-II SAR

Fuel Bundle Orientation - Centralized Section 6.3.4.1 of RAJ-II SAR

Maximum Polyethylene per Assembly

kg 10.2 Table 6-1 of RAJ-II SAR

Package Array - 2x1x2 (2N=4) Section 6.6.2.2

6.3.4.1 Fuel Assembly Orientation

There are no changes to the fuel assembly orientation of the RAJ-II package resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.1 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4.2 Fuel Assembly Gadolinia-Urania Rod Study (2N=4)

As shown in Table 6-5, the limiting fuel enrichment zone used in this analysis (5.0 wt% U-235) conservatively does not credit Gd2O3-UO2 rods for this CSA. This is 12 fewer Gd2O3-UO2 rods than what is required in Table 6-1 of the RAJ-II SAR (Reference 6-2). The fuel enrichment zones from Table 6-1 of the RAJ-II SAR (Reference 6-2) are required for any GNF 10x10 fuel assembly to ship within the RAJ-II package. This CSA does not use Gd2O3-UO2 rods for the limiting demonstrations (2N=4).


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This limiting fuel assembly configuration conservatively bounds the GNF 10x10 fuel assemblies presented in Section 6.3.4.2 of the RAJ-II SAR (Reference 6-2).

6.3.4.3 Fuel Assembly Channel Study

There are no changes to the fuel assembly channel study resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.3 of the RAJ-II SAR (Reference 6-2) remains applicable. Additional confirmation studies are presented in Section 6.13.2.

6.3.4.4 Polyethylene Mass Study

There are no changes to the polyethylene mass study resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.4 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4.5 Fuel Rod Pitch Sensitivity Study (2N=4)

The rod-to-rod pitch presented in Section 6.3.4.5 of the RAJ-II SAR (Reference 6-2) is based on physical drop tests and is conservatively increased further using bounding mechanical and structural calculations. The bounding rod-to-rod pitch presented in Table 6-1 of the RAJ-II SAR (Reference 6-2) is [[ ]] larger than a nominal GNF 10x10 fuel bundle.

To support the hypothetical FeCrAl cladding failure analyses in Section 6.6.2.2, it is required that the rod-to-rod pitch be increased an additional [[ ]] beyond the HAC rod pitch sensitivity study in Section 6.3.4.5 of the RAJ-II SAR (Reference 6-2). This additional [[ ]] rod-to-rod pitch increase is required to allow relocation of fuel segments/pellets within the GNF 10x10 bundle matrix. More specifically, it takes an additional [[ ]] rod-to-rod pitch to allow fuel pellets to migrate from their normal fuel rod locations into the [[ ]]. See Section 6.6.2.2 for additional explanation about hypothetical fuel movements.

This rod-to-rod pitch is not credible because it requires a complete failure of all bundle structural components (e.g., [[ ]]). However, for the purposes of this analysis, the [[ ]] larger rod-to-rod pitch is used to demonstrate the minimal effect of hypothetical fuel relocations from 8 GNF FeCrAl LTRs.

A comparison of the RAJ-II SAR (Reference 6-2) and [[ ]] increased rod-to-rod pitch at optimal moderation is summarized in Table 6-6. The larger rod-to-rod pitch will be used in the bounding GNF letter authorization assembly.

Table 6-6. Increased Rod-to-Rod Pitch at Optimal Moderation

keff σ keff + 2σ Δkeff

Optimal moderation using pitch in RAJ-II SAR (Reference 6-2)

0.85388 0.00026 0.85440 -

Optimal moderation with a [[ ]] larger pitch

0.90677 0.00026 0.90729 0.05289

6.3.4.6 Fuel Pellet Diameter Sensitivity Study

A pellet diameter of [[ ]] was determined to be appropriate as the upper bound for the GNF letter authorization fuel assembly. See Section 6.13.3 for additional information.


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6.3.4.7 Fuel Rod Cladding Thickness Study

The results presented in Section 6.13.4 demonstrate that reactivity increases with the thinnest cladding (minimum cladding thickness) and limiting rod OD (Base) from Table 6-1 of the RAJ-II SAR (Reference 6-2). A bounding cladding thickness of [[ ]] and fuel rod OD of 1.01 cm is found to be the most limiting combination for the GNF letter authorization fuel assembly.

6.3.4.8 GNF Letter Authorization Bundle Worst Case Parameter Design

The previous evaluations have varied single parameters and assessed the effect on reactivity. The subsections below are combined with the worst single parameters to develop a limiting GNF letter authorization assembly that will allow combined shipments of GNF FeCrAl LTA and GNF2 fuel bundles (bounding fuel parameters from GNF 10x10 and GNF FeCrAl LTA).

6.3.4.8.1 Limiting Cladding Material

As shown in Section 6.13.5, the most limiting cladding material is zirconium. Zirconium cladding will be used in the bounding GNF letter authorization assembly.

6.3.4.8.2 Impact of Segmented GNF FeCrAl LTR

As shown in Section 6.13.6, [[ ]] System reactivity decreases with an increase in the number of segmented GNF FeCrAl LTRs in a GNF2 assembly.

6.3.4.9 Part Length Fuel Rod Study

There are no changes to the part length fuel rod study resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.9 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4.10 Moderator Density

There are no changes to the moderator density study resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.10 of the RAJ-II SAR (Reference 6-2) remains applicable. However, it was reconfirmed that an RAJ-II IC at full moderator density with the parameters in Table 6-5 has the most limiting configuration. Results are presented in Figure 6-2.


Page 40 of 70

[[

]]

Figure 6-2. Moderator Density Sensitivity Study for the RAJ-II HAC Worst Case Parameter Fuel Design

6.3.4.11 Material Distribution Reactivity (2N=4)

A study is performed to determine the worst packing material distribution within the RAJ-II IC. The material normally present around the IC fuel compartment is a thermal insulator consisting of alumina silicate. The material normally lining the IC fuel compartment is PCF.

The PCF would be susceptible to fire in a similar fashion as the polyethylene packing materials. It is extremely unlikely that the configuration for this sensitivity would exist post thermal excursion. However, the incomplete PCF burn is considered in this study for conservatism. The limiting HAC 2x1x2 array and GNF letter authorization assembly parameters from Table 6-5 are used in this study. The RAJ-II IC and OC are at optimal moderation.

The results are presented in Figure 6-3 and summarized in Table 6-6. An optimal PCF thickness of 0.0 cm is used throughout the rest of the CSA.

There are no additional changes to this section. Thus, the remainder of Section 6.3.4.11 of the RAJ-II SAR (Reference 6-2) remains applicable.


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[[

]]

Figure 6-3. PCF Thickness Sensitivity Study for 2N=4 HAC Array

6.3.4.12 Inner Container Partial Flooding

There are no changes to the IC partial flooding resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.12 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4.13 RAJ-II Container Spacing

There are no changes to the RAJ-II container spacing resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.13 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.3.4.14 Methodology Justification for Uniform Enrichment Distribution, As-Built Part Length Rod Configurations, and Annular Wrapping of Polyethylene Packing Materials

There are no changes to this section resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.3.4.14 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.4 Single Package Evaluation

The single package evaluation for GNF 10x10 fuels is performed in Section 6.4 of the RAJ-II SAR (Reference 6-2). No evaluation is needed for the GNF letter authorization fuel assembly because the HAC array bounds the single package evaluation. There are no changes to the single package evaluation resulting from the addition of GNF FeCrAl LTRs. Thus, Section 6.4 of the RAJ-II SAR (Reference 6-2) remains applicable.


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6.5 Evaluation of Package Arrays under Normal Conditions of Transport

The evaluation of package arrays under NCT for GNF 10x10 fuels is performed in Section 6.5 of the RAJ-II SAR (Reference 6-2). As summarized in Table 6-3 of the RAJ-II SAR (Reference 6-2), the HAC array and single package demonstrations significantly bound the NCT array and single package configuration.

This is the result of the optimal moderation condition and the physical reduction of the RAJ-II package for HAC. The RAJ-II package HAC model is physically smaller (more compact) than the NCT RAJ-II package model, and the moderator is only present in the IC under HAC. Under the NCT RAJ-II configuration, moderator is present in both the inner and outer container.

A similar moderation study for NCT is shown in Figures 6-8, 6-9, 6-11, and 6-12, where moderation is varied in the OC. This further demonstrates that no NCT evaluations are needed for the GNF letter authorization fuel assembly because the HAC array bounds the NCT array package. Thus, Section 6.5 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.6 Package Arrays Under Hypothetical Accident Conditions (2N=4)

6.6.1 Configuration

The package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) is used to demonstrate the criticality safety of a 2x1x2 array (2N=4) of RAJ-II packages using the GNF letter authorization worst case fuel design at an average enrichment of 5.0 wt% U-235 without Gd2O3-UO2 fuel rods (see Table 6-5). The calculation using the HAC model involves a moderator density sensitivity study. In this study, no moderator is present in the OC, while the moderator density is uniformly varied in the IC and pellet-cladding gap region in all rods to account for confinement of fissile material. The PCF inside the IC fuel compartment is modeled at an optimal thickness of 0.0 cm (see Section 6.3.4.11).

6.6.2 Results

The results of the RAJ-II package array (2N=2x1x2=4) HAC model calculations are shown in Figure 6-2 for the reactivity change with the change in moderator density in the IC at optimal PCF thickness. The system reactivity begins at its lowest value and increases with increasing moderator density. This trend highlights the neutronics of the system. Initially, no moderator, other than the polyethylene packing material surrounding the fuel rods, is present to thermalize neutrons that enter the IC. The maximum keff + 2σ for the package array HAC case is provided in Table 6-2, which is below the USL of [[ ]]. Section 6.6.2.2.1.3 confirms that void in the OC and full moderator density in the IC and pellet-cladding gap region is the most reactive configuration. Therefore, criticality safety of the RAJ-II package array is demonstrated under HAC.

6.6.2.1 Pu-239 Effect on Reactivity for the RAJ-II Package Array HAC

GNF FeCrAl LTRs are administratively limited to Type A material content. Therefore, plutonium shipments within the GNF FeCrAl LTRs are not allowed. Only zirconium rods can contain Type B fissile material and, consequently, Pu-239. Therefore, no additional changes are required for this section. Thus, Section 6.6.2.1 of the RAJ-II SAR (Reference 6-2) remains applicable.


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6.6.2.2 Supplemental Type A Confinement Evaluation

GNF FeCrAl LTRs are conservatively limited to Type A material only. For the purposes of the analyses presented within the subsections below, it is assumed that the HAC accident is severe enough to cause a total failure of all bundle structural components (see Section 6.3.4.5), which would allow fuel movements from the hypothetically failed GNF FeCrAl LTRs.

6.6.2.2.1 Hypothetical Radial and Axial GNF FeCrAl LTR Fuel Movements (2N=4)

6.6.2.2.1.1 Configuration

The package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) is used to demonstrate the criticality safety of a 2x1x2 array (2N=4) of RAJ-II packages using the GNF letter authorization worst case fuel design at an average enrichment of 5.0 wt% U-235 without Gd2O3-UO2 fuel rods as described in Table 6-5. In this study, no moderator is present in the OC while the IC and pellet-cladding gap region is at full moderator density.

[[

]] Figure 6-4 shows each of the radial fuel columns (red), while Figure 6-5 indicates the primary (green) and secondary (purple) GNF FeCrAl LTA relocation sections. Figure 6-6 provides an example of the axial change case (fuel moved to the top of the bundle).

The most limiting hypothetical fuel relocation evaluation was then used in a moderation density sensitivity study for confirmation purposes. In the first study, no moderator is present in the OC while the moderator density inside the IC and pellet-cladding gap region is varied uniformly. In the second study, the moderator in the IC is at full density while the moderator density inside the OC is varied. In the third study, moderator density is varied uniformly in the OC and IC.


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[[

]]

Figure 6-4. Hypothetical Radial Fuel Relocation Positions (Red)


Page 45 of 70

[[

]]

Figure 6-5. Primary (Green) and Secondary (Purple) GNF FeCrAl LTRs with Hypothetical Radial Fuel Relocation Positions (Red)

[[

]]

Figure 6-6. Example of Axial Fuel Movement (Green Rods) into Top of Fuel Bundle

6.6.2.2.1.2 Results of Hypothetical Radial and Axial Fuel Movements

The results of the hypothetical radial and axial fuel movements of 8 GNF FeCrAl LTRs from their primary and secondary locations within the GNF FeCrAl LTA are provided in Tables 6-8 and 6-9. Table 6-7 compares the most limiting condition of this study to the limiting fuel rod-to-rod pitch sensitivity results in Section 6.3.4.5. It confirms that criticality safety of the


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RAJ-II package array is demonstrated under HAC and that radial and axial fuel movements due to the hypothetical failure of 8 GNF FeCrAl LTRs has a minimal effect on system reactivity.

Table 6-7. Summary of Impact on Hypothetical Radial and Axial Fuel Movements

keff σ keff + 2σ Δkeff

Limiting evaluation from Section 6.3.4.5 0.90677 0.00026 0.90729 -

Most limiting radial and axial GNF FeCrAl fuel movement (Evaluation 40)

0.91578 0.00026 0.91630 0.00901

Table 6-8. Results of Hypothetical Radial and Axial Fuel Movements of 8 GNF FeCrAl LTRs from Primary Bundle Locations (2N=4)

Evaluation #

[[

keff σ keff + 2*σ

1 0.90591 0.00026 0.90643

2 0.88772 0.00028 0.88828

3 0.88916 0.00025 0.88966

4 0.91068 0.00025 0.91118

5 0.90594 0.00030 0.90654

6 0.90689 0.00029 0.90747

7 0.90810 0.00031 0.90872

8 0.90470 0.00026 0.90522

9 0.89527 0.00029 0.89585

10 0.89733 0.00028 0.89789

11 0.89924 0.00029 0.89982

12 0.89448 0.00027 0.89502

13 0.89908 0.00026 0.89960

14 0.89925 0.00027 0.89979

15 0.89904 0.00026 0.89956

16 0.89836 0.00027 0.89890

17 0.91016 0.00027 0.91070

18 0.91142 0.00028 0.91198

19 0.91279 0.00029 0.91337

20 0.90869 0.00026 0.90921

21 0.90696 0.00030 0.90756

22 0.90872 0.00025 0.90922

23 0.90745 0.00028 0.90801

24 0.90267 0.00026 0.90319

25 0.90254 0.00030 0.90314

26 0.90511 0.00025 0.90561


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Evaluation #

[[

keff σ keff + 2*σ

27 0.90571 0.00028 0.90627

28 0.90163 0.00028 0.90219

29 0.90518 0.00027 0.90572

30 0.90639 0.00026 0.90691

31 0.90614 0.00027 0.90668

32 0.90538 0.00028 0.90594

33 0.90985 0.00026 0.91037

34 0.91045 0.00030 0.91105

35 0.90817 0.00025 0.90867

36 ]] 0.90327 0.00027 0.90381

Table 6-9. Results of Hypothetical Radial and Axial Fuel Movements of 8 GNF FeCrAl LTRs from Secondary Bundle Locations (2N=4)

Evaluation #

[[

keff σ keff + 2*σ

37 0.91086 0.00027 0.91140

38 0.90007 0.00028 0.90063

39 0.90285 0.00028 0.90341

40 0.91578 0.00026 0.91630

41 0.90729 0.00028 0.90785

42 0.90887 0.00024 0.90935

43 0.91004 0.00027 0.91058

44 0.90604 0.00028 0.90660

45 0.89821 0.00028 0.89877

46 0.90057 0.00024 0.90105

47 0.90256 0.00026 0.90308

48 0.89767 0.00029 0.89825

49 0.90250 0.00025 0.90300

50 0.90204 0.00025 0.90254

51 0.90270 0.00028 0.90326

52 0.90174 0.00030 0.90234

53 0.91313 0.00028 0.91369

54 0.91437 0.00029 0.91495

55 0.91529 0.00030 0.91589

56 0.91115 0.00029 0.91173

57 0.90684 0.00026 0.90736

58 0.90913 0.00027 0.90967


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Evaluation #

[[

keff σ keff + 2*σ

59 0.90822 0.00027 0.90876

60 0.90334 0.00026 0.90386

61 0.90288 0.00025 0.90338

62 0.90541 0.00030 0.90601

63 0.90673 0.00026 0.90725

64 0.90272 0.00028 0.90328

65 0.90628 0.00027 0.90682

66 0.90603 0.00026 0.90655

67 0.90651 0.00026 0.90703

68 0.90567 0.00026 0.90619

69 0.91009 0.00025 0.91059

70 0.91150 0.00030 0.91210

71 0.90782 0.00024 0.90830

72 ]] 0.90313 0.00027 0.90367

6.6.2.2.1.3 Moderation Density Study Results of Evaluation 40

The most limiting hypothetical radial and axial fuel movement from Section 6.6.2.2.1.2 (Evaluation 40) was used in the moderation studies presented below. Figure 6-7 uniformly varies moderation density in the IC and pellet-cladding gap region with no moderator in the OC. The system reactivity begins at its lowest value and increases with increasing moderator density. This trend highlights the neutronics of the system. Initially, no moderator, other than the polyethylene packing material surrounding the fuel rods, is present to thermalize neutrons that enter the IC. In Figure 6-8, the IC is at full moderator density and the moderator density in the OC is varied. In Figure 6-9, the moderator density is varied uniformly in the IC and OC.

Figures 6-8 and 6-9 confirm that void in the OC and full moderator density in the IC and pellet-cladding gap region is the most reactive configuration.


Page 49 of 70

[[

]]

Figure 6-7. IC Moderation Density Study for Evaluation 40


Page 50 of 70

[[

]]

Figure 6-8. OC Moderation Density Study for Evaluation 40


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[[

]]

Figure 6-9. IC and OC Moderation Density Study for Evaluation 40

6.6.2.2.2 Removal of Most Limiting Hypothetically Failed GNF FeCrAl LTR (2N=4)

6.6.2.2.2.1 Configuration

An evaluation was conducted to determine the effect on criticality safety of fuel removal from the hypothetically failed GNF FeCrAl fuel segments. The failed fuel segments [[ ]] from the primary and secondary LTR locations in Section 6.6.2.2.1 were removed from the RAJ-II system (less UO2 mass) and evaluated at optimal moderation.

6.6.2.2.2.2 Results

The results of removing the hypothetically failed GNF FeCrAl fuel segments at optimal moderation are presented in Table 6-10. Figure 6-10 uniformly varies moderation density in the IC and pellet-cladding gap region with no moderator in the OC of the most limiting configuration from Table 6-10 (Evaluation 78). In Figure 6-11, the IC is at full moderator density and the moderator density in the OC is varied. In Figure 6-12, the moderator density is varied uniformly in the IC and OC.

Figures 6-11 and 6-12 confirm that void in the OC and full moderator density in the IC and pellet-cladding gap region is the most reactive configuration.


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Table 6-10. Results of Removing the 8 Hypothetical Failed GNF FeCrAl Fuel Segments from the LTA (2N=4)

Evaluation #

Fuel Segment Removed

LTR Bundle Location (Primary/Secondary)

keff σ keff + 2*σ

73 [[ 0.88833 0.00025 0.88883

74 0.89914 0.00028 0.89970

75 0.90588 0.00026 0.90640

76 0.90264 0.00025 0.90314

77 0.90248 0.00030 0.90308

78 ]] 0.90605 0.00026 0.90657

[[

]]

Figure 6-10. IC Moderation Density Study for Evaluation 78


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[[

]]

Figure 6-11. OC Moderation Density Study for Evaluation 78


Page 54 of 70

[[

]]

Figure 6-12. IC and OC Moderation Density Study for Evaluation 78

6.6.2.2.3 Hypothetical GNF FeCrAl LTR Fuel Movement into Water Rod Locations (2N=4)

[[ ]]

6.7 Fuel Rod Transport in the RAJ-II

There is no intention to ship loose GNF FeCrAl LTRs, and it is not part of the requested content of this letter authorization. Therefore, Section 6.7 (and applicable subsections) of the RAJ-II SAR (Reference 6-2) is not applicable.

6.8 Fissile Material Packages for Air Transport

This package is not intended for air transport of fissile material.

6.9 Conclusion

[[


Page 55 of 70

]] Therefore, failure of up to (≤) 8 GNF FeCrAl LTRs [[ ]] in a GNF2 bundle is acceptable for shipping within an RAJ-II container.

Based on the calculations that have been documented within this letter authorization request, the RAJ-II package is qualified to transport GNF2 UO2 fuel assemblies with up to (≤) 8 GNF FeCrAl LTRs [[ ]] in accordance with the criticality safety requirements set forth in 10 CFR 71.

The following conclusions are drawn from this CSA:

(1) GNF2 fuel assemblies can be shipped with ≤ 8 GNF FeCrAl LTRs (combined shipments of GNF2 and GNF FeCrAl LTAs are allowed).

(2) The fuel assemblies may be channeled or un-channeled.

(3) GNF FeCrAl LTRs may be segmented, uniform or any combination thereof.

(4) GNF FeCrAl LTRs are conservatively limited to Type A material.

(5) GNF FeCrAl LTRs can [[ ]]

(6) Hypothetical relocation of fuel from 8 GNF FeCrAl LTRs has a minimal impact on system reactivity.

6.10 Benchmark Evaluations

6.10.1 SCALE 4.4a and GEMER

SCALE 4.4a and GEMER were not used for this CSA; thus, Section 6.10.1 of the RAJ-II SAR (Reference 6-2) is not applicable.

6.10.2 KENO-VI

The results reported in this letter authorization were performed using KENO-VI (part of the SCALE 6.1 analysis package (Reference 6-3)) with continuous-energy ENDF/B-VII cross-section library. Critical experiments were selected to represent the materials and geometry of the package. There are no changes to this section; thus, Section 6.10.2 of the RAJ-II SAR (Reference 6-2) remains applicable.

6.11 KENO-VI Inputs

Representative KENO-VI inputs are provided in Section 6.11 of the RAJ-II SAR (Reference 6-2).

6.12 References

6-1 “RAJ-II Certificate of Compliance No. 9309,” Docket Number 71-9309, Revision 11, Package Identification No. USA/9309/B(U)F-96.



Page 56 of 70

6-3 Oak Ridge National Laboratory, “Scale: A Comprehensive Modeling and Simulation Suite for Nuclear Safety Analysis and Design,” ORNL/TM-2005/39 Version 6.1, 2011.

6.13 Limiting Parameter Studies

6.13.1 Fuel Assembly Gadolinia-Urania Rod Study for 2N=49 HAC Arrays

The limiting fuel enrichment zone used in the analyses contained within Sections 6.13 and 6.14 is 3.6 wt% with 4 Gd2O3-UO2 rods (for 2N=49 RAJ-II HAC arrays). This fuel enrichment zone conservatively contains one less Gd2O3-UO2 rod for this CSA than what is required in Table 6-1 of the RAJ-II SAR (Reference 6-2). The fuel enrichment zones from Table 6-1 of the RAJ-II SAR (Reference 6-2) are required for any GNF 10x10 fuel assembly to ship within the RAJ-II package. This CSA does not modify the Gd2O3-UO2 loading requirements but uses one (1) less Gd2O3-UO2 rod for the 3.6 wt% U-235 fuel enrichment zone for additional conservatism in the sensitivity studies in Sections 6.13 and 6.14. See Section 6.13.7 for a comparison of assemblies with 3.6 wt% U-235 with 4 Gd2O3-UO2 rods to assemblies with 5.0 wt% U-235 with 12 Gd2O3-UO2 rods.

Both fuel designs use the limiting fuel rod pitch described in Table 6-1 of the RAJ-II SAR (Reference 6-2).

6.13.2 Fuel Assembly Channel Study (2N=49)

A calculation was performed to determine if the presence of channels around the fuel assembly increases system reactivity for the limiting letter authorization HAC assembly described in Section 6.13.1. The channel thickness was varied from [[ ]] and compared to the base case without a channel. The results in Table 6-11 show there is a slight decrease in reactivity due to the channel. All other evaluations within the letter authorization do not include a channel around the fuel assembly.

Table 6-11. Results from RAJ-II HAC Channel Study (2N=49)

Channel Thickness (cm) keff σ keff + 2σ ∆keff

No Channel (Base) 0.91722 0.00034 0.91790 -

[[ 0.91711 0.00028 0.91767 -0.00023

]] 0.91593 0.00025 0.91643 -0.00147

6.13.3 Fuel Pellet Diameter Sensitivity Study (2N=100)

For the pellet diameter sensitivity study, the package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) was used. The most reactive lattice enrichment zone was used for the pellet diameter evaluation (Section 6.13.1). The IC fuel compartment is maintained at optimum moderator density, an alumina silicate thermal insulator envelopes the IC fuel compartment, and there is no moderator in the OC or between packages in the array. The cladding material chosen for the pellet diameter evaluation is zirconium. This study is repeated later in Section 6.13.5 for cladding material comparison. The cladding thickness and fuel rod OD are held constant while the pellet diameter is varied. See Section 6.13.4 for additional discussion about cladding thickness.

The results are presented in Figure 6-13. The results in Figure 6-13 demonstrate that reactivity increases as pellet diameter is increased, and the trend is linear.


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[[

]]

Figure 6-13. RAJ-II HAC Array Pellet Diameter Sensitivity Study

6.13.4 Fuel Rod Cladding Thickness Study (2N=100)

For the fuel rod thickness sensitivity study, the package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) was used. The most reactive lattice enrichment zone was used for the fuel rod thickness evaluation (Section 6.13.1). The IC fuel compartment is maintained at optimum moderator density, an alumina silicate thermal insulator envelopes the IC fuel compartment, and there is no moderator in the OC or between packages in the array. The cladding material chosen for the fuel rod thickness evaluation is zirconium.

This study is repeated later in Section 6.13.5 for cladding material comparison. The cladding thickness and fuel rod OD are held constant while the pellet diameter is varied. The fuel rod OD is based on the bounding GNF 10x10 rod OD (Table 6-1 and the sensitivity study in Section 6.3.4.7 of the RAJ-II SAR (Reference 6-2)). The three (3) cladding thicknesses were chosen to bound the maximum and minimum thicknesses that are allowed by GNF FeCrAl LTRs and Table 6-1 of the RAJ-II SAR (Reference 6-2).

The fuel rod OD from the RAJ-II SAR (Reference 6-2) and a nominal GNF FeCrAl and GNF2 rod OD were then compared using the limiting cladding thickness from the study described above.


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The results are presented in Figure 6-13 and Table 6-12.

Table 6-12. Comparison of Fuel Rod OD and Cladding Thickness for GNF Letter Authorization Bundle

Cladding Thickness

(cm)

Fuel Rod OD

(cm)

Pellet OD (cm)

keff σ keff + 2σ ∆keff

0.038

(Base) 1.010 (Base)

0.895 (Base)

0.93994 0.00025 0.94044 -

0.038

(Base) [[ ]]

0.895 (Base)

0.93667 0.00026 0.93719 -0.00325

[[ ]] 1.010 (Base)

[[ ]] 0.94138 0.00031 0.94200 0.00156

[[ ]] 1.010

(Base) [[ ]] 0.95210 0.00026 0.95262 -

[[ ]] 0.94979 0.00031 0.95041 -0.00221

6.13.5 Limiting Cladding Material (2N=100)

For the limiting cladding material sensitivity study, the package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) and the most reactive lattice enrichment zone was used (Section 6.13.1). The limiting cladding material sensitivity study is conducted by comparing two variations of the GNF FeCrAl alloys against zirconium cladding material. The cladding for all the fuel rods in the assembly are changed to the cladding material of interest for this study. The limiting cladding thickness [[ ]] and fuel rod OD (1.01 cm) from Section 6.13.4 are used for this analysis. The pellet OD is varied for the three (3) cladding materials chosen for this study. The GNF FeCrAl alloys represent the upper (GNF FeCrAl Alloy-1) and lower (GNF FeCrAl Alloy-2) bounds of iron content of the FeCrAl material presented in Section 2.2.

The results for the liming cladding material study are presented in Figure 6-14. As shown in Figure 6-14, zirconium cladding bounds GNF FeCrAl cladding. Zirconium cladding is also shown to bound fuel assemblies containing a limited number of fuel rods with GNF FeCrAl cladding material (see Section 6.13.6).


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[[

]]

Figure 6-14. Limiting Cladding Material Study for Bounding GNF Letter Authorization Bundle

6.13.6 Impact of Segmented GNF FeCrAl LTRs (2N=49)

All the previous sensitivity studies have been with uniform fuel rods. To support shipments of segmented fuel rods, an evaluation was conducted. The segmented rod design is described in Chapter 1.0. The segmented sensitivity study used the 7x1x7 HAC array and the limiting assembly parameters presented in Section 6.13.1. The segmented rods have GNF FeCrAl Alloy-1 cladding (bounding GNF FeCrAl cladding material from Section 6.13.5), whereas all other fuel rods have zirconium cladding.

The segmented rods were modeled as varying [[ ]] within a fuel rod with GNF FeCrAl Alloy-1 cladding. [[


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]] System reactivity decreases with an increase in the number of segmented GNF FeCrAl LTRs in a GNF2 assembly.

[[

]]

Figure 6-15. Potential GNF FeCrAl LTR Locations and Axis of Symmetry


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[[

]]

Figure 6-16. Examples of GNF FeCrAl LTRs in Primary (Red) Locations

Table 6-13. Results of Segmented GNF FeCrAl LTRs in Primary Locations [[ ]]

Case Number of GNF

FeCrAl Segmented LTRs


Base 0 0.91595 0.00028 0.91651 -

1 2 0.91397 0.00027 0.91451 -0.00200

2 2 0.91474 0.00025 0.91524 -0.00127

3 2 0.91403 0.00025 0.91453 -0.00198

4 2 0.91386 0.00026 0.91438 -0.00213

5 8 0.90689 0.00031 0.90751 -0.00900


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Table 6-14. Results of Segmented GNF FeCrAl LTRs in Primary Locations [[ ]]

Case Number of GNF



Base 0 0.91595 0.00028 0.91651 -

1 2 0.91143 0.00024 0.91191 -0.00460

2 2 0.91177 0.00029 0.91235 -0.00416

3 2 0.91270 0.00026 0.91322 -0.00329

4 2 0.91269 0.00027 0.91323 -0.00328

5 8 0.89827 0.00024 0.89875 -0.01776

6.13.6.1 Additional GNF FeCrAl Rod Placement Studies (2N=49)

Additional evaluations were conducted to further understand the effect on GNF FeCrAl LTR placement within a GNF2 assembly. The evaluation was conducted in a manner similar to the evaluation in Section 6.13.6. [[ ]] The FeCrAl LTR loading patterns considered for this study are shown in Figure 6-17 (represented as the green rods).

The results for [[ ]] are shown in Table 6-15. As shown in Table 6-15, segmented GNF FeCrAl LTRs decrease reactivity. This sensitivity study also illustrates that location of the segmented GNF FeCrAl LTRs does not have a significant effect on system reactivity. System reactivity decreases with an increase in the number of segmented GNF FeCrAl LTRs in a GNF2 assembly.


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[[

]]

Figure 6-17. Examples of GNF FeCrAl LTRs in Secondary (Green) Locations


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Table 6-15. Results of Segmented GNF FeCrAl LTRs in Secondary Locations [[ ]]

Case Number of GNF



Base 0 0.91595 0.00028 0.91651 -

1 2 0.91350 0.00021 0.91392 -0.00259

2 1 0.91456 0.00024 0.91504 -0.00147

3 2 0.91309 0.00023 0.91355 -0.00296

4 2 0.91325 0.00023 0.91371 -0.00280

5 2 0.91234 0.00026 0.91286 -0.00365

6 1 0.91429 0.00025 0.91479 -0.00172

7 2 0.91249 0.00024 0.91297 -0.00354

8 1 0.91523 0.00024 0.91571 -0.00080

6.13.7 Limiting Fuel Enrichment Zone for Section 6.13 and 6.14 Evaluations (2N=49)

The limiting fuel enrichment zone sensitivity study was conducted with the worst fuel parameters described in Section 6.13.1 and in the 7x1x7 HAC array. This study compares GNF letter authorization assemblies of 3.6 wt% U-235 with 4 Gd2O3-UO2 rods to assemblies with 5.0 wt% U-235 with 12 Gd2O3-UO2 rods. The RAJ-II IC and OC are at optimal moderation.

Table 6-16 summarizes the results provided in Section 6.13.8, where the PCF thicknesses were optimized for each fuel enrichment zone in Table 6-16. As shown in both Table 6-16 and Figure 6-18, the 3.6 wt% U-235 fuel enrichment zone bounds the 5.0 wt% enrichment zone.

Table 6-16. Comparison of Limiting Fuel Enrichment Zones

Letter Authorization

Evaluation Section

U-235 Enrichment (wt%) and Number of Gd2O3-UO2 Rods

Peak keff σ Peak

keff + 2σ ∆keff

6.13.8

3.6 wt% U-235 4 Gd2O3-UO2 Rods

0.91722 0.00034 0.91790 -

5.0 wt% U-235 12 Gd2O3-UO2 Rods

0.91723 0.00023 0.91769 -0.00021

6.13.8 Material Distribution Reactivity Sensitivity Study for Sections 6.13 and 6.14 Evaluations (2N=49)

Similar to the evaluation presented in Section 6.3.4.11, the limiting HAC 7x1x7 array and GNF letter authorization assembly parameters from Section 6.13.1 are used in this study. Two (2) lattice enrichment zones (3.6 wt% U-235 with four (4) Gd2O3-UO2 rods, and 5.0 wt% U-235 with 12 Gd2O3-UO2 rods) are used in this evaluation because each enrichment zone will have a different optimal PCF thickness. The RAJ-II IC and OC are at optimal moderation (confirmed in Section 6.6.2).


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The results are presented in Figure 6-18 and summarized in Table 6-16. Optimal PCF thickness for the 3.6% U-235 enrichment zone was 1.1 cm and 1.0 cm for the 5.0 wt% U-235 enrichment zone. An optimal PCF thickness of 1.1 cm is used with the 3.6 wt% U-235 and 4 Gd2O3-UO2 rods as the bounding GNF letter authorization assembly throughout the rest of the CSA.

[[

]]

Figure 6-18. PCF Thickness Sensitivity Study for 2N=49 HAC Array


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6.14 Package Arrays Under Hypothetical Accident Conditions (2N=49)

6.14.1 Configuration (2N=49)

The package array HAC model described in Section 6.3.1.2.2 of the RAJ-II SAR (Reference 6-2) is used to demonstrate criticality safety of a 7x1x7 array (2N=49) of RAJ-II packages using the GNF letter authorization worst case fuel design at an average enrichment of 3.6 wt% U-235 with four (4) 2.0 wt% Gd2O3-UO2 fuel rods (see Section 6.13.1). The calculation using the HAC model involves a moderator density sensitivity study and optimal PCF thickness study. No moderator is present in the OC while the moderator density inside the IC and pellet-cladding gap region is varied uniformly to account for confinement of fissile material (loss of containment).

6.14.2 Results (2N=49)

The results of the RAJ-II package array (2N=7x1x7=49) HAC model calculations are shown in Figure 6-19 for the reactivity change with the uniform change in moderator density in the IC and pellet-cladding gap region. The system reactivity begins at its lowest value and increases with increasing moderator density. This trend is similar to the moderation study results in Section 6.3.4.10.

Figure 6-20 shows the results of the optimal PCF thickness study with full density moderator in the IC and pellet-cladding gap region.

The studies contained within Section 6.14 show that the RAJ-II configurations used for the demonstrations in Section 6.13 were conducted at optimal moderation (void in the OC and full moderator density in the IC).


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[[

]]

Figure 6-19. IC Moderator Density Sensitivity Study for Type A GNF Letter Authorization Fuel Assembly Shipments


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[[

]]

Figure 6-20. PCF Thickness Sensitivity Study for Type A GNF Letter Authorization Fuel Assembly Shipments


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7.0 PACKAGE OPERATIONS

The existing package operations described in Chapter 7.0 of the RAJ-II SAR (Reference 7-1) apply to shipping under this letter authorization request. The evaluations presented in Reference 7-1 describe the package loading, the package unloading, and the preparation for empty package transport. There are no changes to Chapter 7.0 resulting from the introduction of a limited number of GNF FeCrAl LTRs.

7.1 References



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8.0 ACCEPTANCE TESTS AND MAINTENANCE PROGRAM

The existing maintenance program for the RAJ-II package described in Chapter 8.0 of the RAJ-II SAR (Reference 8-1) applies to this letter authorization request. The evaluations presented in Reference 8-1 describe the acceptance testing of new packages and the maintenance program of existing packages. All fuel rods (zirconium alloy and GNF FeCrAl alloy) shall be leak tested to the same leak tight criteria per the methods of Section 8.2.2 of Reference 8-1. All sections of Chapter 8.0 remain applicable to the GNF FeCrAl Letter Authorization request.

8.1 References


Documents

GNF - FeCrAl Lead Test Assemblies, RAJ-II Letter