Influence of Thermo-mechanical Cycling on Pre-hydrogenated Zircaloy-4 … · 2019-06-26 ·...

IRS

N/F

RM

-29

6 in

d 5

Influence of

Thermo-mechanical Cycling

on

Pre-hydrogenated Zircaloy-4 Embrittlement

by

Radial hydrides

Jean Desquines*, Manfred Puls**, Stéphane Charbaut*

and Marc Philippe*

*IRSN

**MPP Consulting

2 19TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY

Context & Objectives▌ Situations where thermo-mechanical cycling of fuel rods is expected:

- Dry cask storage,

- Spent fuel transportation from one spent fuel pool to another one

▌ Expected influence of cycling based on literature data

o No clear trend (Kearns, Mishima, Chu, Sakamoto, Billone,...)

o Possibly more radial hydrides and rather stronger embrittlement

▌ Main Goals of the study: clarify the expected influence of cycling on radial

hydride precipitation:

- Relying on a large data set on single cycle test results using « C »-shaped samples,

- Then cycle samples and evaluate the radial hydride precipitation and cladding

embrittlement.


1- Experimental protocol


“C”-Shaped Compression Tests in the Elastic Range

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6

fqq= 0.0

X: location within the cladding thickness

(0: Outer Diameter, 1: Inner diameter)

fqq= 0.0

s:

cu

rvil

ine

ar

dis

tan

ce

to

A(m

m)

𝜎𝑡 𝑥, 𝑠 = 𝜎𝑡 𝐴 . 𝑓𝜃𝜃 𝑥, 𝑠

𝜎𝑡 𝐴 =𝐹 𝑁

0.013 𝐿 𝑚𝑚

Stress free area

Stress free area

A q

r

CCT sample

Load

Load

x

1s

0

A

F

𝐿

Equator


Radial Hydride Heat Treatments (RHT) considered

0

100

200

300

350

0 4 8 12 16 20

Com

pre

ssio

n load

Tem

pera

ture

(°C

)

Time (h)

5 N

315°C

FRHT

20°C/h

2h1h

Tem

pera

ture

(°C

)Time (h)

5 N

365°C

FRHT

20°C/h

0

100

200

300

400

0 4 8 12 16 20

2h1h

Com

pre

ssio

n load

350°C Max temperature RHT 400°C Max temperature RHT

• The load is applied as late as possible to limit the sample creep but

significantly before hydride precipitation

• The creep is expected to increase linearly with cycle number

F[H] contents – 50 to 236 wppm


Equator

Post-test metallography

Using CCT to study radial hydride precipitation

Hydrided sampleF

RHT, 1 to 30 cycles

(Constant Load)

F.d

at RT

Failure test: CCT


Experimental device

500 N load cellFan cooling

the load cell

FurnaceElectromechanical tension-

compression machine

L1

L2

F.d

2.Re

Furnace

Simple model of the test


𝑊𝑒𝑙𝑙 𝑘𝑛𝑜𝑤𝑛𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑝𝑟𝑜𝑝𝑒𝑟𝑡𝑦𝐹𝐸 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑖𝑜𝑛

Interpretation of the RHT load displacement record

F.d

Furnace

𝛿 = 𝛿𝑜𝑓𝑓𝑠𝑒𝑡 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑒𝑙 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒

𝑡ℎ𝑒𝑟𝑚𝑎𝑙 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑐𝑟𝑒𝑒𝑝

+ 𝛿𝑟𝑜𝑑𝑠𝑡ℎ𝑒𝑟𝑚𝑎𝑙

Reasonably good agreement is obtained between calculations and

measurement assuming 0 creep

RE

OR

-103 –

firs

t cycle

𝑎𝑑𝑗𝑢𝑠𝑡𝑒𝑑



𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑐𝑟𝑒𝑒𝑝

= 𝛿 − 𝛿𝑚𝑜𝑑𝑒𝑙

Creep deformation remains below ~1% diameter change after 30 cycles

F.d

Furnace

time (h)-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

0 100 200 300 400 500

𝛿 − 𝛿𝑚𝑜𝑑𝑒𝑙(𝑚𝑚)

REOR-103 –30 RHT cycles

Creep displacement (temperature stabilized)


RHT & CCT Test matrix

350 & 400°C Max temperature – 1 to 30 cycles – [H] content below 240 wppm

Maximum stress at equatorial location: between 190 and 220 MPa

RHT

parameters

REOR-XXX ([H](wppm)) – Test ID and associated hydrogen content

Italic: the hydrogen content of tested conditions in past programs.

Cycles Number 1 2 5 10 30

Max R

HT t

em

pera

ture

(°C

)

350

53 ; 63 ;

69 ; 74 ;

REOR-117 (109)

127 ; 141 ;

177 ; 217 ;

309 ; 322 ;

525 ; 540

REOR-114 (176)

REOR-118 (95)

REOR-115 (101)

REOR-110 (139)

REOR-106 (203)

REOR-119 (86)

REOR-116 (94)

REOR-111 (138)

REOR-112 (209)

REOR-113 (210)

400

REOR-131 (61)

REOR-133 (141)

REOR-134 (187)

217 ; 218 ;

398 ; 478

REOR-126 (62)

REOR-120 (78)

REOR-125 (147)

REOR-123 (236)

REOR-121 (75)

REOR-124 (148)

REOR-135 (177)


2- Analysis of Metallographic data


RHT at 350°C max temperature

• When cycling: higher density but comparable fraction of radial hydrides

• Saturated influence of cycling over 5 cycles

1 5 10 30

130

200

REOR-17 [11]

REOR-14 [11] REOR-110

REOR-106

REOR-111

REOR-112 REOR-113

Cycles

[H]

(wppm)

Meta

llogra

phs

at equ

ato

rial lo

cation


RHT at 400°C max temperatureM

eta

llogra

phs

at equato

rial lo

cation

1 5 10

150

200

REOR-134

REOR-125

REOR-123

REOR-124

Cycles[H]

(wppm)

75

REOR-120

REOR-133

REOR-135

REOR-131 REOR-121

At H~200 wppm: higher density but comparable fraction of radial hydrides

Below H~150 wppm: no influence of cycling


Influence of cycling and stress on incipient radial

hydride precipitation

Slight influence of cycling at 350°C maximum temperature

No clear influence at 400°C

Ta

nge

ntialstr

ess (

MP

a)

[H] (wppm)

Mixed radial & circumferential hydrides

Circumferential hydrides

0

20

40

60

80

100

120

0 100 200 300 400 500 600

Temp.

12

35

0 5

10

30

RHT cycles

400°C RHT350°C RHT


Influence of cycling and stress on radial hydride

precipitation

Limited influence of cycling on radial hydride precipitation stress thresholds

Circumferential hydrides

Ta

ng

en

tia

lstr

ess (

MP

a)

[H] (wppm)

Mixed radial & circumferentialhydrides

Radial hydrides

(Eq.10)

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600R

HT

max

imu

m t

emp

erat

ure

(°C

) 12

35

04

00

45

0

5

10

30

5

10

1

RHT cycles0%

10

0%

1


3- Radial hydride

Embrittlement

F, d


Load displacement records – an illustration

Crack nucleation is associated with the first significant load-drop and

deviation to the elastic-plastic trend

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2 2.5Displacement (mm)

CCT-112 (209wppm)Elasticity

Plasticity

CCT-115 (101wppm)

Cra

ck n

ucle

ation

Brittle

cra

ck p

ropagation

Cra

ck n

ucle

ation


Load displacement records

Surprisingly ductile nucleation was associated with brittle crack

propagation and brittle crack nucleation with ductile crack propagation

Rather high [H] contents

&low fracture toughness

Rather low [H] contents

&high fracture toughness

Elasticity

Plasticity

ducti

le

bri

tlle

bri

tle

ducti

le

Cra

ck

nucle

ati

on

Cra

ck

pro

pagati

on

F/L

(N/m

m)

Displacement (mm)

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2

REO

R-1

10

REO

R-1

06

REO

R-1

11

REO

R-1

12

REO

R-1

13

REO

R-1

14

REO

R-1

15 REOR-116

REO

R-1

17

REO

R-1

18

REO

R-1

19

REOR-120

REOR-121 REO

R-1

23

REO

R-1

24

REO

R-1

25

RC

T-1

26

REOR-131

REO

R 1

33

REO

R-1

34

REO

R-1

35

2.5


Crack nucleation displacement – 1 cycle

Maximum sensitivity to crack nucleation at about [H]= 100 wppm,

No obvious influence of maximum RHT temperature

Cra

ck n

ucle

atio

nd

isp

lace

me

nt

(mm

)

[H] (wppm)

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 100 200 300 400 500 600

350°C

400°C

450°C

Maximum RHT temperature


Crack nucleation displacement – several cycles

[H] (wppm)

0.5

1.0

1.5

2.0

0 100 200 300 400 500 600

Protective influence of RHT cycling

Detrimental influence of RHT cycling

2

350

400

5

10

30

5

10

RHT cyclesTemp.

Cra

ck n

ucle

atio

nd

isp

lace

me

nt

(mm

)

350°C RHT cycling trend

• Regions associated with higher density of radial hydrides have a lower

sensitivity to crack nucleation

• Protective influence of RHT cycling on crack nucleation


Conclusion▌ The thermo-mechanical cycling was studied relying on CCT tests

▌ Analysis of metallographs

- At 350°C for H contents between 75 and 230 wppm, and at 400°C for H contents

close to 200 wppm: shorter and denser hydrides observed,

- A 400°C below 200 wppm, no influence of cycling is observed

- The denser and short hydrides were associated with slightly easier radial hydride

precipitation

▌ A protective influence of cycling was observed on radial hydride

embrittlement.

▌ Extrapolation of these results to irradiated claddings:

If there is any location containing 100 wppm, then no influence of cycling is

expected



Stress at crack nucleation– several cycles

Brittle crack nucleation region remains at [H] contents of about 100 wppm

and no influence of cycling is observed in this region

Cra

ck n

ucle

atio

nta

ng

en

tia

lstr

ess

(MP

a)

[H] (wppm)

Plasticity

Elasticity

500

700

900

1 100

1 300

1 500

0 100 200 300 400 500 600

2

350

400

5

10

30

5

10

RHT cyclesTemp.

350°C RHT cycling trend


-3.0

-2.0

-1.0

0.0

0.5

0 2 4 6 8 10 12 14 16 18

ModelRecord

d(mm)

50 N loading

Cooling @ 20°C/h

2h dwell @ 350°C

heating

Time (h)


𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑒𝑙 =

𝐹 1 − 𝜈2

2.6410−3𝐸. 𝐿𝑒

𝑅𝑒 − 𝑒

2.7644


L1

L2

F.d

2.Re

Furnace

𝛿 = 𝛿𝑜𝑓𝑓𝑠𝑒𝑡 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑒𝑙 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒

𝑡ℎ𝑒𝑟𝑚𝑎𝑙 + 𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑐𝑟𝑒𝑒𝑝

+ 𝛿𝑟𝑜𝑑𝑠𝑡ℎ𝑒𝑟𝑚𝑎𝑙

𝛿𝑟𝑜𝑑𝑠𝑡ℎ𝑒𝑟𝑚𝑎𝑙

= −15.510−6 𝑇 − 𝑇0 . 𝐿1 + 𝐿2

𝛿𝑠𝑎𝑚𝑝𝑙𝑒𝑡ℎ𝑒𝑟𝑚𝑎𝑙

= −5.610−6 𝑇 − 𝑇0 · 2𝑅𝑒

Reasonably good agreement is obtained between calculations and

measurement assuming 0 creep

RE

OR

-103 –

firs

t cycle


Load displacement records

Surprisingly ductile nucleation was associated with brittle crack

propagation and brittle crack nucleation with ductile crack propagation

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2 2.5Displacement (mm)

CCT-112 (209wppm)

𝐹 𝐿𝑁/𝑚

𝑚

Elasticity

Plasticity

CCT-115 (101wppm)

Cra

ck n

ucle

ation

Brittle

cra

ck p

ropagation

Cra

ck n

ucle

ation


Elasticity

Plasticity

ducti

le

bri

ttle

bri

ttle

ducti

le

Cra

ck

nucle

ati

on

Cra

ck

pro

pagati

on

F/L

(N/m

m)

Displacement (mm)

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2

REO

R-1

10

REO

R-1

06

REO

R-1

11

REO

R-1

12

REO

R-1

13

REO

R-1

14

REO

R-1

15 REOR-116

REO

R-1

17

REO

R-1

18

REO

R-1

19

REOR-120

REOR-121 REO

R-1

23

REO

R-1

24

REO

R-1

25

RC

T-1

26

REOR-131

REO

R 1

33

REO

R-1

34

REO

R-1

35

2.5

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Influence of Thermo-mechanical Cycling on Pre-hydrogenated Zircaloy-4 … · 2019-06-26 ·...

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