In-Pile Irradiation Testing for Molten Salt Reactors

A. Abou-Jaoude

NUC Workshop

September 2019

Presentation Overview

1. Background – Need for testing

– Gaps and focus areas

– Licensing and commercialization

2. Past & Current Efforts– Past Experiments: MTR, LITR, ORR

– Current Experiments: LR-0, MITR, OSURR, HFR

3. Ongoing Efforts at INL– The Versatile Experimental Salt Irradiation Loop (VESIL)

2

Large Interest in MSR Concepts

• Molten Salt Concepts garnering a wide range of significant interest from industry.

• Many concepts remain untested. Salt irradiation data will prove key to development and licensing activities.

• INL can leverage its ATR infrastructure and build expertise and capabilities.

3

Company Concept Fuel Type SpectrumPower

(MW)Fuel Coolant

Tin/Tout

(ºC)Country

CAS-SINAP TMSR-LF1 Liquid fuel Thermal 2 Th-U (<20%U-235) LiF-BeF2 600/700 China

ThonCon Powder ThonCon Liquid fuel Thermal 557 U + ThF4 BeF2-NaF 565/704 US

Seaborg Tech. CUBE Liquid fuel Thermal 50 LiF + Th/Pu/MA-Fx LiF-NaF-KF 700/900 Denmark

Japan FUJI Liquid fuel Thermal 450 ThF4 + UF4 LiF-BeF2 Japan

Flibe Energy LFTR Liquid fuel Thermal 600 2LiF-BeF2 +Th BeF2-NaF 500/653 US

Terrestrial Energy IMSR Liquid fuel Thermal 400 5% U-235 NA NA/600 Canada

Transatomic Power MSR Liquid fuel Epithermal 520/1250 LiF + UF4 (5% U-235) LiF + UF4 (5% U-235) NA/650 US

Moltex energy SSR Liquid fuel Fast/Thermal 150-1,000 NaCl/UCl3/PuCl3 ZrF4/KF/NaF 500/1121 UK

AlphaTech Liquid fuel Thermal? Th?FLiBe? US

Yellowstone Energy Liquid fuel Thermal? UO2 Nitrite salt US

Elysium MCSFR Liquid fuel Fast 2,500 UCl3-NaCl + SNF/Pu Chloride salt 500/600 US

Terrapower MCFR Liquid fuel Fast UCl3-NaCl (?) US

PSI SOFT Liquid fuel Fast 3,000 1PuCl3-8UCl3-10NaCl 984 Switzerland

CAS-SINAP TMSR-SF1 TRISO Pebble Thermal 10 LiF-BeF2 600/650 China

UC-Berkeley PB-AHTR TRISO Pebble Thermal 236 LEU(19.75%) LiF-BeF2 600/700 US

Kairos PB-FHR TRISO Pebble Thermal LiF-BeF2 US

ORNL FHR-Demo TRISO Plates Thermal 100 LEU (15.5%) LiF-BeF2 660/700 US

Where are the gaps?Lack of Data in 5 main categories:

A. Neutronics

– Integral cross-section measurements (notably 37Cl)

– Delayed neutron precursor drift

– Validation of neutronics/depletion codes

B. Salt and solute properties evolution under irradiation

– Thermophysical properties

– Formation and destruction of salt compounds (e.g. UCl6) and free radicals

C. Fission product mass transport accountancy

– 3H/P/S production and behavior

– Diffusion rates of different fission products in salt (notably Xe)

– Precipitation and plating of noble metals

– Validation of species transport code

D. Irradiation enhanced corrosion effects

– Structural containment PIE

– Evaluation of samples inside flow area

E. Operational validation

– Demonstrate operation for given conditions (ºC, m/s, Re, W/cc, FP concentration etc.)

– Chemistry control proof of concept (e.g. electrolysis of U/Be)

4

• Unirradiated salt/solute properties

• Materials compatibility (corrosion)

I. Out of pile loop

• Nuclear data measurements

• Limited fission product behavior

II. Static salt irradiation

• Representative salt properties and mass transport under irradiation

• Validation of salt chemistry control process (3T, FPs etc.)

III. Circulating in-pile loop

• Core-wide proof of concept

IV. Demonstration plant

Specific Needs depending on Salt

5

Identified Phenomena Category

1. Evolution of thermophysical properties

and flow velocity(A)

2. Salt solubility limits and constituent

separation(B)

3. Fission product source term and

transport out of the salt(A) & (C)

4. Material corrosion at high burnup and

flow velocity(D)

5. Precipitate formation and plate out of

fission products + actinides(C)

6. Volatilization of salt compounds

including fission gases(B) & (C)

7. Demonstration of salt processing and

fission product polishing(C) & (E)

8. Management of localized salt

freezing/thawing(E)

9. Evolution of heat transfer correlations

with burnup(B) & (E)

10. Component demonstration (e.g.

resistors, valves, pumps)(E)

11. Chemistry control demonstration(E)

12. Salt solubility limits and constituent

separation(B)

Need to know before Prototype: Depends on salt type:

CLE

AN

FU

ELE

D

FLUORIDE CHLORIDE

FLiBE3H handling and control

Limited testing needs:

validate #3, #6, #7

MgCl, NaCl, KCl

Activation products (notably

S, P) and their transport

Very limited testing needs

asses #3, #6, #7

1. Demonstrated

e.g. LiF-BeF2-ZrF4-UF4

Deployed in MSRE

Limited testing needs:

validate #3, #4, #7, #10

2. Unproven

e.g. Terrestrial concept

Moderate testing needs:

verify #1 to #12

UCl3-NaCl

No data on source term

transport, evolution of

properties or solubility limits

Extensive testing needs:

evaluate #1 to #12

Licensing Priorities

• NRC guidelines based on IAEA SSR-3/1.

• Fulfilment of the following fundamental safety functions for a nuclear power plant shall be ensured for all plant states:

i. control of reactivity;

ii. removal of heat from the reactor and from the fuel store; and

iii. confinement of radioactive material, shielding against radiation and control of planned radioactive releases, as well as limitation of accidental radioactive releases.”

6

Defining Tests Priorities

Separate Effects Test

• An experiment in which the primary focus is on a specific parameter or process

• Data would provide localized information on the behavior of a specific part of the system

• Demonstrate adequacy of physical models to predict physical phenomena in accident scenarios

• Determine uncertainty bounds of individual physical models

Integral Effects Test

• Primary focus on more global behavior and interactions between parameters and processes

• Examination of large-scale systems to determine the performance of various components and their interactions

• Demonstrate that interactions are well identified and predicted correctly

7

(NUREG-0800 Chapter 15.0.2)

• Static vs. Circulating

– (natural vs. forced)

• Controlled vs. “drop-in”

• Off-gas vs. plenum

• In-salt measurement vs. structural sensors

• Low salt volume vs. high salt volume

– larger source term vs. large sample

• Prototypic burnup vs. accelerated burnup

• Thermal neutrons vs. neutron filter

• Chemistry control vs. no control

• Polishing/filter vs. no treatment

• Etc.

Test Type: Test Characteristics:

Chemistry Control and Processing

• Options for fluoride-based systems:

– Salt Processing:

• Salt diversion and external processing (e.g. 233Pa)

• Bubbling (fluorination) to remove some fission products

– Redox Control:

• Gas sparging (bubbling HF/H2 mixture)

• Reducing metal (Be or U)

• Adding soluble salt-redox buffer to solution (injection of U metal)

• Comments for chloride-based systems:

– Chloride MSR control still unproven. Fundamental research needed.

– Complex options (e.g., salt diversion) not feasible in the context of an experiment

– All three redox control options are theoretically applicable. Simplest is likely U-metal rod

Elements TypeProcessing

Time

H, Kr, Xe Volatile fission gases 50 s

Zn, Ga, Ge, As, Se, Nb,

Mo, Tc, Ru, Rh, Pd, Ag,

Cd, In, Sn, Sb, Te

Precipitating/plating noble

metals2.4 h

Br, Rb, Zr, I, Cs, Ba, CeSoluble halogens, alkali metals,

and alkaline earth elements10–15 days

Pr, Nd, Pm, Sm, Gd, Tb,

Dy, Ho, Er Soluble rare-earth elements30 days

Eu 50 days

8

Proposed Processing and Removal

Rates for the MSBR

W. L. Carter and E. L. Nicholson, "Design and Cost Study of a Fulorination - Reductive Extraction - Metal Transfer

Processing Plant for the MSBR," Oak Ridge National Laboratory, ORNL-TM-3579, 1972.

How to measure?

Instrument Measurement PrecedenceR&D

needs

Thermocouples

- Salt freezing/thawing (#8)

- Evolution of thermal properties (#1)

- Heat transfer correlations (#9)

Yes Low

Thermal needle

probes

- Evolution of salt thermal conductivity

(#1)

Limited

(static)Medium

Frequency based

conductivity

- Evolution of salt thermal conductivity

(#1)None Medium

Calorimetric cells - Evolution of salt melting point (#1) Limited Medium

Pressure gauge - Evolution of hydraulic properties (#1) Yes Low

Flowmeter/

Velocimeter- Evolution of hydraulic properties (#1) Very limited Medium

Electro-chemistry- Salt constituent separation (#2)

- Precipitation and plating effects (#5)

Limited

(static)Low

pH meter- Salt acidity and chemical composition

(#2)

Limited

(static)Medium

Fiber optic

spectrometer

- Thermal properties evolution (#1)

- Solubility of elements in salt (#2)None High

Structural

distortions

- Crack growth and corrosion issues (#4)

- Thermal expansion and deformation (#4)Limited (dry) Medium

Off-gas system- Tracking volatile gas activity (#6)

- Monitoring of gaseous source term (#3)

Limited (e.g.

AGR)Medium

Salt sampling

mechanism

- Freeze salt samples at specific intervals

for later PIE studies (#2)None Medium

9

Instrument Measurement PrecedenceR&D

needs

Flowmeter - Salt viscosity at a given burnup (#1) Yes Low

Thermal needle

probes- Thermal conductivity at final burnup (#1) Yes Low

Calorimetric cells - Heat capacity at a final burnup (#1) Yes Low

Ultrasonic testing

- Element plating on structure (#5)

- Material corrosion (#4)

- Localized freezing/thawing (#8)

- Component degradation (#9, #10)

Yes Low

Material

characterization

- Element plating on structure (#5)

- Material corrosion (#4)

- Heat exchanger degradation (#9)

Yes Low

Fiber-optic

methods

- Bulk salt properties (#1)

- Salt constituent characterization (#2, #3)

- Radiative heat transfer properties (#1,

#9)

- Material corrosion (#4)

Yes Medium

In-Situ: Post-Irradiation Examination (PIE):

History of Past Salt Irradiation Experiments

10

Reactor Salt Type Structure Year Tmax Circulation

LITR NaF-ZrF4-UF4 Inconel 1956 870°C forced

MTR NaF-ZrF4-UF4 Inconel + INOR-8 1958 870°C forced

ORR LiF-BeF2-ZrF4-UF4 Hastelloy N 1966 650°C natural

LR-0 LiF-BeF2 Graphite 2017 700°C static

MITR LiF-BeF2 Graphite 2017 700°C static

OSURR KCl-MgCl Molybdenum alloy 2018 800°C static

HFR LiF-ThF4 Graphite 2018 600°C static

• Two main eras of experiments

• 1950s-1960s: large circulating loop, investigating corrosion, salt behavior, component validation, mostly fluorides, fuel-bearing

• 2016 - : static capsules mainly, wide ranger range of salts, mostly non-fuel bearing, narrower goals (e.g. 3T production)

Early Salt Irradiation Experiments

11

MTR fused-salt test loop

ORR natural circulation loop

• MTR achieved peak power density of 250 W/cc at 870°C. Main objective was support of MSRE. Salt driven by a pump at a speed with a Re = 3100-7600. Total of 2,249 h of irradiation. Main challenges include sensor failures, unstable pump speeds, salt leakages, plugging of purging system etc.

• LITR was mainly intended to support ARE. Focus on transient analysis and pump demonstration.

• ORR was natural circulating loop within test reactor beamline. Accrued 3,439 h of irradiation. Maximum power density reached was 165 W/cc.

D. B. Trauger and J. A. Colin,

"Circulating Fused-Salt Fuel

Irradiation Test Loop,"

Nuclear Science and

Engineering, vol. 9, pp. 346-

356, 1961.

H. C. Savage, E. Campere, J. M. Baker and E. G.

Bohlmann, "Operation of Molten-Salt Convection Loops

in the ORR," Oak Ridge Naitonal Laboratory, 1960.

Recent Salt Irradiation Experiments

12

MITR 3H production capsule

• LR-0 used to validate cross-sections associated with clean FLiBe system.

• MITR mainly intended for 3H production and management plus some corrosion studies. Different graphite capture media were tested to evaluate ability to capture 3H.

• OSURR first irradiation of chloride salts (700-800°C). Main purpose is to analyze effect of neutron bombardment on salt radiolysis and corrosion rates.

• HFR only recent test to include fueled-salt (~600°C and P max of ~35 W/g). Main objective is to conduct PIE, study FP effect on Hastelloy N and monitor fission-gas release.

C. W. Forsberg, et

al. "Integrated

FHR Technology

Development:

Trititum

Management,

Materials Testing,

Salt Chemistry

Control, Thermal

Hydraulics and

Neutronics,

Associated

Benchmarking and

Commercial

Basis," NEUP

Report, MIT-ANP-

TR-180, 2018.

FHR SALIENT-01

P. R. Hania, “MSR Irradiation Program

at NRG Petten”, MSR Workshop 2018,

Oak Ridge, Tennessee, October 2018

OSURR KCl-MgCl2irradiation

J. McDuffee, N. Ezell, K. Smith, S.

Raiman, N. Taylor, L. Qualls, “Design

and Irradiation of a Molten Salt

Corrosion Experiment in The Ohio

State University Research Reactor”,

Oak Ridge National Laboratory,

ORNL/TM-2018/1005, 2018.

Ongoing Efforts at INL: Versatile Experimental Salt Irradiation Loop (VESIL)

13

Number of cycles required in ATR

ElementMSBR

equilibrium B-position I-position

O-position

I 4.57 × 10-6 g/cm3 0.22 cycles 1.22 cycles 16.32 cycles

La 3.50 × 10-5 g/cm3 0.50 cycles 2.05 cycles 21.90 cycles

Ce 9.68 × 10-5 g/cm3 0.49 cycles 2.04 cycles 25.81 cycles

Nd 1.11 × 10-4 g/cm3 0.66 cycles 2.32 cycles 22.76 cycles

Pm 1.19 × 10-5 g/cm3 0.70 cycles 2.30 cycles >30 cycles

Sm 1.18 × 10-5 g/cm3 0.57 cycles 2.17 cycles 18.89 cycles

Eu 2.47 × 10-6 g/cm3 1.07 cycles 3.34 cycles >30 cycles

233U 2.57 × 10-2 g/cm3 4.70 cycles >30 cycles >30 cycles

• Evaluate feasibility of irradiation inside Advance Test Reactor (ATR). Analyzed B, I, and O-positions.

• Considering a natural circulating loop to fully assess corrosion, plating, and bubbling effects

• Wide variety of salts evaluated to show assess FP quantity produced

• For fast systems: assuming salt chemistry mainly driven by fission reactions (and products) rather than by fast neutrons)

Parametric Evaluation Inside Three ATR Positions

14

mass generated per volume of irradiated salt (mg/cm3-salt)BOC power

(W/ cm3)

Activity

(kCi/cm3)

Decay Heat

(W/cm3) Burnup

(MWd/kg)3H Te Mo Cs Xe 233U Pu All volatile All precipitate at EOC at EOC

FLiBe

B 3.67 - - - - - - 8.57 - 145 0.04 0.22 -

I 1.61 - - - - - - 3.75 - 55 0.02 0.07 -

O 0.15 - - - - - - 0.36 - 5 - 0.01 -

ARE

B - 0.11 5.48 0.48 1.09 - 4.80 1.17 1.47 108 0.68 7.30 14.97

I - 0.03 1.92 0.18 0.37 - 0.54 0.41 0.47 40 0.20 2.47 5.21

O - - 0.18 0.02 0.03 - 0.03 0.03 0.04 4 0.02 0.24 0.48

MSRE

B 3.27 0.03 1.46 0.13 0.29 - 1.28 7.96 0.39 158 0.21 2.02 67.15

I 1.43 0.01 0.51 0.05 0.10 - 0.14 3.46 0.13 59 0.06 0.68 28.03

O 0.14 - 0.05 0.01 0.01 - 0.01 0.33 0.01 5 0.01 0.06 2.67

MSBR

B 3.48 0.03 1.04 0.10 0.22 5.17 0.55 8.37 0.26 155 0.51 3.05 5.35

I 1.52 0.01 0.25 0.02 0.05 1.23 0.06 3.62 0.06 57 0.11 0.61 2.11

O 0.15 - 0.02 - - 0.10 - 0.35 - 5 0.01 0.05 0.20

LFTR1

B 1.88 0.18 9.02 0.81 1.82 - 8.05 6.37 2.44 254 1.12 11.54 19.64

I 0.82 0.06 3.21 0.30 0.63 - 0.91 2.61 1.13 94 0.32 3.89 7.26

O 0.08 0.01 0.30 0.03 0.05 - 0.05 0.24 0.07 8 0.03 0.37 0.67

LFTR2

B 3.41 0.03 0.84 0.08 0.19 10.09 - 8.19 0.19 144 0.80 4.24 2.83

I 1.49 - 0.07 0.01 0.02 2.40 - 3.51 0.02 53 0.16 0.60 1.05

O 0.14 - - - - 0.20 - 0.34 - 5 0.01 0.03 0.10

TAP

B 3.19 0.75 38.25 3.45 7.74 - 34.16 15.79 10.37 887 4.70 48.61 17.03

I 1.40 0.25 13.63 1.28 2.65 - 3.85 6.15 3.36 329 1.34 16.41 6.01

O 0.13 0.02 1.26 0.15 0.21 - 0.20 0.55 0.31 29 0.12 1.58 0.55

REBUS

B - 0.47 24.18 2.18 4.89 - 21.60 5.28 6.55 541 2.98 31.01 16.68

I - 0.16 8.61 0.81 1.68 - 2.43 1.83 2.13 201 0.85 10.48 5.86

O - 0.01 0.79 0.09 0.13 - 0.13 0.15 0.19 18 0.08 1.01 0.54

Thermal Analysis

• Conducted preliminary design/thermal analysis using STAR-CCM+ and SAM (MOOSE code)

• Natural circulation induced by changing the heat conduction to the ATR coolant at two axial regions of the loop via fins.

• Preliminary assessment shows that flow rates of the order of 0.2 m/s are feasible with a representative ΔT of 100°C

15

Parameter Example Case

Maximum Temperature (K) 994.423

Minimum Temperature (K) 893.39

ΔT (K) 101.033

Salt Velocity (m/s) 0.225

Total height (cm) 78

Radius of VESIL (cm) 3.1

Total heat (kW) 95.03

Salt Mass (kg) 6.54

Fin Gas-Gap Design

Summary and Future Work

• Wide range of different concepts in industry. Very positive momentum, but challenge for irradiation campaign

• Salt irradiation testing will be case-dependent. However tests can leverage similar experimental setup.

• Main priority from a licensing standpoint will be to understand and quantify barriers for source term release from salt. Also important: evolution of thermophysical properties and controllability

• Bold and ambitious salt irradiation testing in the past. Why not again?

• R&D in instrumentation will likely be crucial for irradiation campaign

• Ongoing studies at INL to assess feasibility of a salt loop in ATR and in support of Terrapower/Southern Company Services collaboration.

16

17

Points of Discussion

• What single phenomena should be a priority for salt irradiation testing?

• Is an irradiated salt loop needed for untested salts? Or can it be avoided?

18