ASTM2016 Out-of-Reactor Test of Corrosion and …...Hydrogen Uptake – Fuel Cladding Samples 3 Hydrogen pickup rates for various fuel cladding materials were approximately constant

© 2016 Electric Power Research Institute, Inc. All rights reserved.

Daniel M. Wells (EPRI), Richard Becker (Studsvik), Jiaxin Chen (Studsvik), Clara Anghel

(Westinghouse), Dennis Hussey (EPRI), Jayashri Iyer (Westinghouse), and

Jacqueline Stevens (AREVA)18th International Symposium on Zirconium

in the Nuclear Industry15-19 May 2016

Hilton Head, South Carolina, USA

Out-of-Reactor Test of Corrosion and Hydrogen Pickup in Fuel

Cladding Materials in Contact with Nickel Metal

2© 2016 Electric Power Research Institute, Inc. All rights reserved.

Dissolved Hydrogen and Crack Growth RateThe Primary Pressure Boundary Motivation

Rate of PWSCC Crack Growth Rate for Nickel Based Alloys Reduced By Operating at Higher Primary Water Hydrogen Concentration

0.E+00

1.E-07

2.E-07

3.E-07

4.E-07

5.E-07

6.E-07

7.E-07

8.E-07

1 10 100 1000

H2 Level, cc/kg

CG

R, m

m/s

343C

325C

290C

Based on a mean MRP Growth Rate for Alloy 182 (16X peak vs. H2, = 20.2)

35 c

c/kg

H2

80 c

c/kg

H2

Current band

60 c

c/kg

H2


Zircaloy Corrosion and Hydrogen Pickup

Corrosion and Hydrogen Pickup

Hydrogen pickup causes embrittlement and potentially failures– Dominant source believed to be cladding

oxidation, not RCS H2

Cold handling and accident condition regulation (LOCA, RIA, etc.) main concern

Nickel Window Effect

Nickel in direct contact with the cladding surface can enhance hydriding (window for hydrogen transport into material)– In-reactor and out-of-pile observations

Zr-based Alloy Protective Oxide Water

Zr4++2O 2- ZrO2

2H2O+4e- 2O2-+4He-

O2-

xH

Zr+2H ZrH2

Zr+2H Zr(H)

4H xH +(2-x/2)H2

HPUF (%) = (x/4)(100)

Zr Zr4+ +4e-

Zr-based Alloy Protective Oxide Water

Zr4++2O 2- ZrO2

2H2O+4e- 2O2-+4He-

O2-

xH

Zr+2H ZrH2

Zr+2H Zr(H)

4H xH +(2-x/2)H2

HPUF (%) = (x/4)(100)

Zr Zr4+ +4e-

1Assessment of the Effect of Elevated Reactor Coolant Hydrogen on the Performance of PWR Zirconium-Based Alloys. EPRI, Palo Alto, CA: 2006. 1013522.

Zr-based Guide tubes [1]

Nickel

SS 410

SS 304Copper

Tota

l H2

Pic

kup

(ppm

)

Pressure H2 (MPa) 1


Hydrogen and Corrosion Product TransportThe Fuel Crud Motivation - Based on Thermodynamics3

Ni solubility varies significantly with Ni/Fe ratio due to precipitation of NiFe2O4

Hydrogen impacts the trend in at temperature Ni solubility Fe solubility increases with temperature for all

conditions evaluated ZnFe2O4 solubility increases with increasing

hydrogen

3MULTEQ Version 7.0 (EPRI Product 1025010)

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

260 270 280 290 300 310 320 330 340

Nic

kel S

olub

ility

(ppb

)

Temperature (C)

H2 = 0 cc/kgH2 = 15 cc/kgH2 = 25 cc/kgH2 = 35 cc/kgH2 = 60 cc/kg

0

0.005

0.01

0.015

0.02

0.025

260 270 280 290 300 310 320 330 340

Nic

kel S

olub

ility

(ppb

)

Temperature (C)

pH(300C) = 6.9, H2 = 35 cc/kgpH(300C) = 7.3, H2 = 35 cc/kgpH(300C) = 7.5, H2 = 35 cc/kgpH(300C) = 6.9, H2 = 0pH(300C) = 7.3, H2 = 0pH(300C) = 7.5, H2 = 0

Nickel Solubility as a Function of pH300°C and Hydrogen (B = 600 ppm, Ni initial input = 0.1 ppb, Fe initial input = 10 ppb)

Nickel Solubility as a Function of Hydrogen for pH300°C = 7.1

(B = 600 ppm, Ni initial input = 1 ppb, Fe initial input = 10 ppb)

Soluble transport will be impacted by hydrogen


Elevated Reactor Coolant Hydrogen and Zircaloy Materials

Provide a chemical mitigation technique for Primary Water Stress Corrosion Cracking (Alloy 600 weld metals)– Only mitigation technique for Bottom Mounted

Instrument nozzles– FRP, MRP, and Chemistry all collaborating to

support implementation FRP/P-TAC Supported Projects

– Literature Review1

– Autoclave Tests3

– In-reactor tests– Plant Demonstrations

Cladding Spacer Grid Welds

End Plug Welds

1. Analysis of the Effect of Elevated Reactor Coolant Hydrogen on the Performance of PWR Zr-Based Alloys. EPRI, Palo Alto, Ca: 2006. 1013522.

3. Out-of-Reactor Corrosion Tests of Fuel Cladding Materials. EPRI, Palo Alto, CA: 2014. 3002004140.


The AutoclaveParameters Target Values

pH at 300ºC (360°C) using BORIS code ~7.2 (~8.4)

Boron, ppm as boric acid 750

Lithium, ppm as lithium hydroxide 2.67

Dissolved hydrogen, cc H2/kg H2O* 30, 100, 500

Dissolved oxygen, ppb < 1

Exposure temperature, °C 360

Pressure, bar 215-216*Dissolved hydrogen concentration in cc H2/kg H2O is calculated at 1 atm and 25°C.

Exposure Period

Number of Days

1 302 1003 2004 2005a 1005b 100


Long Term Autoclave Exposure

2008 2009 2010 2011 2012 2013

START long term exposure: (as-received and pre-oxidized materials*)

Build up experimental facility for the long term exposure

Ni window effect testing

(nickel platting)

Ni-material contacteffect testing

100d30d 100d 200d 200d 100d

“5” exposure periods

2014 Technical Report

30020041403

Public Report

*Including the full set of AREVA (M5®, Zry-4, Zry-2) and WEC (ZIRLO™ and Opt ZIRLO™) fuel cladding, spacer and end plug materials

3Out-of-Reactor Corrosion Tests of Fuel Cladding Materials: Corrosion as a Function of Hydrogen Overpressure. EPRI, Palo Alto, CA: 2014. 3002004140.


Hydrogen Uptake – Fuel Cladding Samples3

Hydrogen pickup rates for various fuel cladding materials were approximately constant (~ 50 ppm/year–150 ppm/year)

No correlation between hydrogen pickup rate and dissolved hydrogen could be positively identified

Hydrogen Pickup Rate – Fuel Cladding Samples

30 cc/kg 100 cc/kg 500 cc/kg

Hydrogen Pickup – Fuel Cladding Samples730 days exposure, without correction for pre-oxidation


Note: Hydrogen content corrected for pre-oxidation hydrogen. Select data are presented, see report for details.

30 cc/kg


Nickel Metal Plating Experiment3

Targets

pH at 300ºC ~7.2

Boron, ppm 750

Lithium, ppm 2.67

Hydrogen, cc/kg 30, 100, 500

Oxygen, ppb <1

Test temperature, C 360

Ni layer (~1 µm thick) sputtered after the

removal of the native Zr-oxide.

Zry-4 substrate

Etching by Arion sputtering

before Ni coating

Ni/Zry-4

Zircaloy-4 with natural oxide

Zry-4 substrate

Naturally formed (native) ZrO2 oxide

Zr-oxide with embedded Ni layer (~1 µm thick).

Zry-4 substrate

No etching before Ni coating

Ni/ZrO2/Zry-4

Reference sample

Zry-4 substrate

No coating

ZrO2/Zry-4

Exposure time: 100 days exposure

Exposure conditions:

100% Ni directly in contact with Zry-4 or

with the ZrO2.

Five of each type in each autoclave = 45

samples.



Visual/SEM results – Ni/Zry-4 samples3

Increasing H2 level

30 cc H2 100 cc H2 500 cc H2

Uncoated

Ni-coated



More Representative Ni-Window Effect TestingWill an increased hydrogen uptake (corrosion) be observed with a more realistic contact with nickel metal?

P

Crud powder

Zry-4tube section

Step 1 Step 2 Step 3

P

Crud composition (weight fraction %):

Type 1 (Ref.) Type 2 Type 3

Ni (m) 0 15 60

NiO 50 40 25

NiFe2O4 50 45 15

Nickel Alloy 718

Average 120 ± 13N of force used to insert

the rod into the holderDimple for smearing

and contact point

Zry-4

Smeared line

Zry-4/Nickel alloy 718 coupling specimens3

Zry-4/Crud contact samples (Subject of Paper)



Zry-4/Crud contact samples – XRD of Crud

The ratio between Ni(m)-peaks and NiO/NiFe2O4-

peaks changes at different DH levels.

The ratio between Ni(m)-peaks and

NiO/NiFe2O4-peaks changes at different DH

levels.

Peaks for Ni(m) have appeared for the

specimens exposed at 100 and 500 cc

60 wt% Ni15 wt% Ni0 wt% Ni

Conversion of NiO/NiFe2O4 to Ni metal at higher DH is observed


Zry-4/Crud Contact SamplesCladding Hydrogen Pickup Results

Incr

easi

ng D

H

Increasing Ni

Hydrides

The

CR

UD

has

bee

n po

sitio

ned

tow

ards

the

low

er p

art o

f eac

h of

the

figur

es

Zry-4/Crud Contact SamplesCross-sectional SEM of Hydrides Zry-4/Crud Contact Samples

Hydrogen Pickup

Zry-4/Crud Samples: accelerated hydrogen pickup above 100 cc/kg and 60 weight% nickel metal crud Zry-4/Nickel Alloy 718 Samples: no visually

(including microscopic) or profilometriclyobservable impact

Baseline HPU at 30 cc H2/kg


?

Is this the same Ni window effect?

At 100 cc H2/kg H2O converts NiO / NiFe2O4 to Ni metalAt 100 cc H2/kg H2O and a high

Ni content (60 wt%) increases the HPU

30 100DH (cc/kg)

HP

U w

ith h

igh

Ni C

RU

D c

onte

nt (a

rb. u

nit)

Primary concern is where the onset of increase HPU occurs


Dissolved Hydrogen and HPU Risk Most PWRs operate with dissolved hydrogen

closer to 40 cc H2/ kg H2O– EPRI guidance is 25-50 cc H2/ kg H2O4

– Regulatory concern related to operation at elevated DH without benchmarking data for corrosion / hydrogen pickup models5

Most concern for cores with highly cruddedreload fuel where crud can redistribute to fresh cladding surfaces at restart– Crud from highly boiling plants is known to

contain more nickel

PWR Cycle Average Hydrogen6

4 FRN 2014-05562, Proposed Rules, Performance-Based Emergency Core Cooling System Cladding Acceptance Criteria, March 24, 2014.5Pressurized Water Reactor Primary Water Chemistry Guideline, Revision 7. EPRI, Palo Alto, CA: 2014. 3002000505.6 EPRI Fuel REliability Database (FRED) - EPRI


Path to Safe Operation of a PWR with Elevated Reactor Coolant Hydrogen Initial Fuels Plan to Reach Demonstration

1. Literature Review2. Autoclave Tests3. In-reactor tests4. Plant Demonstrations

Autoclave testing results– No effect on the oxide growth for clean

materials– No effect on the hydrogen pick up for clean

materials– But, accelerated hydrogen pickup above 100

cc/kg with a high weight% nickel crud

Both AREVA Inc. and Westinghouse have indicated in-reactor tests are not required BUT – Plant demonstrations on hold due to limited interest

– Drivers of elevated hydrogen for mitigation of PWSCC in bottom mounted instrument nozzles unclear

– Peening may be more viable and cost effective


Summary and Conclusions A two year program of autoclave experiments was completed to

evaluate the impact of dissolved hydrogen concentration on zirconium alloy corrosion and hydrogen pickup Long-term testing of many materials found no impact of dissolved

hydrogen on corrosion or hydrogen pickup The nickel-window effect was also tested

– Significant corrosion and hydrogen pickup in all sputter-coated Zry-4 materials and catastrophic failure at highest dissolve hydrogen concentrations (500 cc H2/ kg H2O)

– More representative testing of Zry-4 in contact with nickel based alloy spacers and nickel containing crud found less dramatic results

Increased hydrogen pickup was observed for Zry-4 in contact with synthetic crud containing 60 wt% nickel metal and exposed to 100 cc H2/ kg H2O dissolved hydrogen– Further testing is warranted


Acknowledgments (non-author project contributors)Studsvik EPRIMr. Peter Gillén Dr. Aylin KucukMr. Jimmy Karlsson Mr. Jeff DeshonMs. Johanna Hjorteen Dr. Bo Cheng Mr. Henrik ZakrissonMr. Sören Karlsson WestinghouseMr. Bo Johansson Dr. Rita BaranwalDr. Daniel Jädernäs Mr. Andrew AtwoodMs. Maria Hövling Mr. Joe LongMr. Roger LundströmMr. Henrik Nilsson AREVAMr. Jari Syrjänen Mr. Larry LamannaMr. Timo Jokinen Mr. Damien Kaczorowski Mr. Per Ekberg Mr. John Riddle Mrs. Ann-Sofi Pettersson Ms. Riitta Johansson Other OrganizationsMrs. Anna-Maria Alvarez-Holstein Dr. George SabolDr. Pia Tejland Dr. Fredrik Lindberg and Dr. Lyuba Belova (Swerea Kimab)Mr. Anders Molander Mr. Niklas Pettersson, KTHMs. Charlotta Gustafsson Mr. Sven-Erik Bäckman, Mr. Ingvar Bernhardsson (Degerfors Laboratorium)Mr. Gunnar WikmarkDr. Petter AnderssonMs. Lotta Nystrand


References

1 Assessment of the Effect of Elevated Reactor Coolant Hydrogen on the Performance of PWR Zirconium-Based Alloys. EPRI, Palo Alto, CA: 2006. 1013522. (publicly available) 2 MULTEQ Version 7.0 (EPRI Product 1025010) 3Out-of-Reactor Corrosion Tests of Fuel Cladding Materials.

EPRI, Palo Alto, CA: 2014. 3002004140. (publicly available)4 FRN 2014-05562, Proposed Rules, Performance-Based Emergency Core Cooling System Cladding Acceptance Criteria, March 24, 2014.5Pressurized Water Reactor Primary Water Chemistry Guideline, Revision 7. EPRI, Palo Alto, CA: 2014. 3002000505.6 EPRI Fuel REliability Database (FRED) - EPRI


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ASTM2016 Out-of-Reactor Test of Corrosion and …...Hydrogen Uptake – Fuel Cladding Samples 3 Hydrogen pickup rates for various fuel cladding materials were approximately constant