Hydrogen Absorption Mechanism of Zirconium Alloys Based on

16th ASTM Zr Symposium, Chengdu, May 9-13, 2010 1

K. Une*1, K. Sakamoto1, M. Aomi1, J. Matsunaga1 , Y. Etoh1

I. Takagi2, S. Miyamura2, T. Kobayashi2, K. Ito3

1 Nippon Nuclear Fuel Development Co., Ltd.2 Kyoto University, Dept. Nuclear Eng.3 Global Nuclear Fuel Japan Co., Ltd.

Hydrogen Absorption Mechanismof Zirconium Alloys

Based on Characterization of Oxide Layer


●● SampleSample

●● Corrosion testCorrosion test- Steam at 400 °C- 1M LiOH aqueous solution at 290-350 °C

●● Characterization of oxide layerCharacterization of oxide layer- Microcrack（SEM/BSE）- Microstructure (TEM/STEM)- Alloy element precipitation/dissolution (SIMS mapping/EPMA)- Crystal structure/stress state （Raman spectroscopy）- In-situ hydrogen diffusivity (NRA)- Alloy element chemical state (XANES)

Alloy Sn Fe Cr NiZry-2 1.36 0.18 0.11 0.07GNF-Ziron 1.46 0.26 0.10 0.05VB 0.5 0.5 1.0 -

wt%

Experimental


10

100

1000

0.1 1.0 10.0 100.0t (d)

Hyd

roge

n (p

pm)

Zry-2GNF-ZironVB

m=1

1 10 10010

100

1000

1 10 100 1000t (d)

Hyd

roge

n (p

pm)

Zry-2GNF-ZironVB

m=1/2

Hydrogen Absorption Ratein Out-of-pile Corrosion Tests

Hydrogen absorption rate- LiOH water test (linear law) >> Steam test (paraboric law)- Zry-2 > Ziron > VB

Steam test (400Steam test (400 °°CC )) LiOH test (290LiOH test (290 °°CC ))


0

20

40

60

80

100

0 5 10 15t (d)

Hyd

roge

n pi

ckup

frac

tion

(%)

Zry-2GNF-ZironVB

0

20

40

60

80

100

0 20 40 60 80 100 120t (d)

Hyd

roge

n pi

ckup

frac

tion

(%) Zry-2

GNF-ZironVB

Zry-2＞GNF-Ziron＞VB

Hydrogen Pickup Fractionin Out-of-pile Corrosion Tests

Steam test (400Steam test (400 °°CC )) LiOH test (290LiOH test (290 °°CC ))


Cross Sectional BSE Images of Oxide LayersZry-2 GNF-Ziron VB

1 mm

3 mm

1 mm 1 mm

1 mm 1 mm 1 mm

3 mm 3 mm

(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

Steam oxideSteam oxide(Pre(Pre--transition)transition)

Steam oxideSteam oxide(Post(Post--transition)transition)

LiOH waterLiOH wateroxideoxide


ZryZry--2 (1.62 (1.6 mmm)m) VB (1.1VB (1.1 mmm)m)

Cross Sectional TEM Imagesof LiOH-water Oxide at Metal/Oxide Interface

Oxide

Metal

Degraded grain boundaries

50 nm

(a) Oxide

Metal


50 nm

(b)


-12

-10

-8

-6

-4

-2

0

0.0001 0.001 0.01 0.1 1

LiOH濃度 (mol/l)Log

[X]

(mol

/l)

[OH-]

[H+]

[HZrO3-]

[Li+]

FT-IR Results and Thermodynamicsof ZrO2-LiOH-H2O System

Ion concentration in solution at 290Ion concentration in solution at 290 °°CC

LiOH concentration (mol/l)

Higher HZrO3- concentration

at higher LiOH solution(ZrO2 + OH- = HZrO3

-)

O-H bonds detected only in LiOH oxide

0.00

0.05

0.10

0.15

0.20

0.25

5001000150020002500300035004000

Wavenumber (cm-1)

Reflection (-)

H2O Oxide

LiOH Oxide

Zr-O

Zr-O

CO2

OH

Steam oxide

LiOH oxide

FTFT--IR spectra in oxide layerIR spectra in oxide layer


Zry-2 (1.4 mm) VB (1.4 mm)

Cross Sectional TEM Images of Pre-transitionSteam Oxide at Metal/Oxide Interface

酸化膜

金属部

Oxide

Metal 200 nm

Precipitate

(a)

m/t-ZrO2

hcp-Zr

sub-oxideSub-oxide

A

B

C

A

B

C

酸化膜

金属部

Oxide

Metal 200 nm

Precipitate

(b)


STEM/EDS Images of Pre-transition Steam Oxide

Sub-oxide layer

Sub-oxide layer

(a) (b) (c)

(d) (e) (f)

STEM Fe Cr

ZryZry--22

VBVB


187

188

189

190

191

192

193

0.0 0.5 1.0 1.5 2.0Distance from M/O boundary (mm)

Wav

enum

ber (

cm-1

)

Zry-2GNF-ZironVBPowder sample

0.0

0.2

0.4

0.6

0.8

1.0


Tetra

gona

lZrO

2 fra

ctio

n

Zry-2GNF-ZironVB

Tetragonal ZrO2 Fraction and Raman Shiftin Steam Corroded Oxides

Tetragonal ZrO2 fraction near M/O boundaryVB > Ziron » Zry-2

Tetragonal ZrOTetragonal ZrO22 fractionfraction Raman shift of monoclinic ZrORaman shift of monoclinic ZrO22 peakpeak


-2.0

-1.6

-1.2

-0.8

-0.4

0.0


Stre

ss (G

Pa)

Zry-2GNF-ZironVB

Compressive Stress in Steam Corroded Oxides

Compressive stress distributionCompressive stress distribution

Pressure dependencePressure dependenceof monoclinic ZrOof monoclinic ZrO22 peakpeak

J. Godlewski, et al., ASTM STP 1354, 2000, pp.877-900

Gruneisen coeff.Gruneisen coeff.2.5 cm2.5 cm--11/GPa/GPa

Compressive stress in inside oxide layerVB > Ziron > Zry-2


Nuclear Reaction Analysis for DeuteriumDistribution in Oxide Layer

NRA: D(3He,p)4He

T/C

Deuteriumplasma

3He+ (1.7MeV)p

Zr alloy specimen

D2 gas

Oxide layer

SSD

W heater(Max. 400℃)


0

5E+20

1E+21

1.5E+21

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0

Distance from oxide surface (mm)

Deu

teriu

m c

onc.

(cm

-3)

Zry-2GNF-ZironVB

Oxide layer(Zry-2)

(Ziron)(VB)

LiOD-water oxide (290°°C xC x 40h)) D2O-steam oxide (400 °C x 15d)

0

1E+20

2E+20

3E+20

4E+20

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0Distance from oxide surface (mm）

Deu

teriu

m c

onc.

(cm

-3)

Zry-2GNF-ZironVB

Non-protectivelayer

Barrier layer1at%

Deuterium Profiles in LiOD-waterand D2O-steam Oxides

・Double layer structureOutside: non-protective layer (0.8 mm)Inside: barrier layer (0.8-0.9 mm)

・Barrier layer widthAlmost no difference among the alloys

・Almost flat deuterium profile⇒Rate-controlling step: M/O boundary reaction

・Deuterium concentration in oxide layerZry-2 > Ziron > VB


0

2E+20

4E+20

6E+20

8E+20

1E+21

-0.5 0.0 0.5 1.0 1.5 2.0Distance from oxide surface (mm)

Deu

teriu

m c

onc.

(cm

-3)

5700s11700s22500s26100s

Barrier layerNon-protectivelayer

0

2E+20

4E+20

6E+20

8E+20

1E+21

-0.5 0.0 0.5 1.0 1.5 2.0Distance from oxide surface (mm)

Deu

teriu

m c

onc.

(cm

-3)

4500s15300s29700s44100s

Barrier layerNon-protectivelayer

In-situ Deuterium Diffusion Profilesin H2O-Steam Oxide at 300 °C

VB oxide (1.4VB oxide (1.4 mm))

Diffusion coefficient in barrier oxide layerGNF-Ziron: D=3.8E-14cm2/s at 26100 sVB : D=1.7E-14cm2/s at 29700 s

GNFGNF--Ziron oxide (1.7Ziron oxide (1.7 mm))


SIMS Mapping of Zry-2 LiOH-water Oxide

(d)

(c)

2mｍ

1

0.1

0.01

(b)

Metal

Oxide


SIMS Mapping of Zry-2 Steam Oxide

2mｍ

Metal Oxide1

0.1

0.01


SIMS Mapping of VB Steam Oxide

2mｍ

1

0.1

0.01

MetalOxide


0

0.5

1

1.5

2

Zry-2 GNF-Ziron VB

X-ra

y in

tens

ity ra

tio

Fe Sn Cr

0

0.5

1

1.5

2

Zry-2 GNF-Ziron VBX-

ray

inte

nsity

ratio

Fe Sn Cr

LiOHLiOH--water corroded specimenwater corroded specimen Steam corroded specimenSteam corroded specimen

Fe：chemical form change from precipitates in metal to dissolved state in oxide,especially in LiOH oxide due to higher oxidative environment

Cr：almost same distribution in metal and oxideSn：almost same distribution in metal and oxide, except for VB

Relative X-ray Intensity Ratioof In-oxide to In-metal by EPMA Analysis


0

20

40

60

80

100

0.0 0.2 0.4 0.6 0.8 1.0Relative dissolved iron （－）

Hyd

roge

n pi

ckup

frac

tion（％）

LiOH specimenSteam specimen

Hydrogen pickup fractionHydrogen pickup fractionvs. relative dissolved ironvs. relative dissolved iron

Increase VO・・

Decrease electron

Suppress H・, OHO・ diffusivity

Suppress H・, OHO・mobility

Decrease electrochemical potential

・Oxygen ion defectsFe2O3→ 2FeZr

’ + VO・・ + 3OO

[VO・・] = 1/2[FeZr

’]n=K[FeZr

’]-1/2PO2-1/4

Suppression Effect of Hydrogen Absorptionby Iron Dissolution

Ionic radii of cations (CN= 7)Zr4+： 0.78nmSn4+： 0.75nmFe3+： 0.72nmCr3+： 0.62nmNi2+： 0.69nm

Soluble

Insoluble


Summary● Hydrogen pickup rate and fraction

- LiOH corroded (linear law) >> Steam corroded (parabolic law)- Decreased with higher iron content in alloys, especially remarkable in LiOH water test

Zry-2>GNF-Ziron>VB

● Oxide layer property- LiOH-water oxide

Degraded grain boundary network seen only in LiOH oxides, except forthin intact layer near metal/oxide boundary Increased hydrogen pickup rates

- Pre-transition steam oxideDouble layer structure of outside mainly m-ZrO2 with faster diffusivity, andinside mainly t-ZrO2 with slower diffusivity (barrier layer of 0.8-0.9 mm )Compressive stress in barrier layer: VB>GNF-Ziron>Zry-2D diffusivity: DH (VB) = 0.5´DH (GNF-Ziron)

- Alloy element behaviorFe: mainly as oxide and metallic precipitates and preferential dissolution into ZrO2Cr: mainly as oxide and metallic precipitatesNi: mainly as metallic precipitates

● Lower hydrogen absorption property in higher Fe and Cr alloys- Higher Fe dissolution into oxide matrix- Higher compressive stress in barrier oxide layer- Ni free effect

Decrease of H diffusivity



Hydrogen Pickup Property in In-pile andOut-of-pile Conditions of BWR Fuel Cladding

Hydrogen solubility at 300 C

Hydrogen pickup of ZryHydrogen pickup of Zry--2 fuel cladding2 fuel claddingHydrogen pickup fraction inHydrogen pickup fraction in

inin--pile and outpile and out--ofof--pile conditionspile conditions

K. Ogata, et al., 2007 LWR Fuel Performance Mtg.,San Francisco, Sep.30 - Oct.3, 2007, Paper 1024.

M. Aomi, et al., Top Fuel 2009, paris, Sep.6-10, 2009,Paper 2077.

Hyd

roge

n pi

ckup

(ppm

)

Irradiation time (d)

InIn--pilepile

OutOut--ofof--pilepile

InIn--pilepile


Ellingham Diagram of Alloy Element Oxides

100 200 300 400 500 600-1100

-1000

-900

-800

-700

-600

-500

-400

-300Delta G (Ellingham)

File:‹C

kJ/mol

Temperature

0.67 Cr2O3

2.00 FeO

0.67 Fe2O3

2.00 NbO

NbO2

0.40 Nb2O5

2.00 NiO

SnO2

ZrO2

NiO > Fe2O3 » SnO2 > Cr2O3 > > ZrO2


Cross Sectional TEM Images ofSteam Oxide at Oxide Surface

40 nm 40 nm

Precipitate

Zry-2 (1.4 mm) VB (1.4 mm)


Cross Sectional TEM Imagesof LiOH-water Oxide at Middle Location

20 nm


(a)

20 nm


(b)

ZryZry--2 (1.62 (1.6 mmm)m) VB (1.1VB (1.1 mmm)m)


Fraction of Oxidation State of Fe, Cr and Niin Oxide Layer Evaluated from XANES Spectra

Documents

Hydrogen Absorption Mechanism of Zirconium Alloys Based on