Hungarian Academy of Sciences KFKI Atomic Energy Research Institute Behaviour of irradiated RPV cladding F. Gillemot, M. Horváth, G. Úri, H-W. Viehrig,

Hungarian Academy of Sciences Hungarian Academy of Sciences KFKI Atomic Energy Research InstituteKFKI Atomic Energy Research Institute

Behaviour of irradiated RPV Behaviour of irradiated RPV cladding cladding

F. Gillemot, M. Horváth, G. Úri, F. Gillemot, M. Horváth, G. Úri, H-W. Viehrig, L. H-W. Viehrig, L. Debarberis, T. Fekete, Debarberis, T. Fekete, E. HoundeffoE. Houndeffo

1 th Hungarian-Ukrain Joint Conference1 th Hungarian-Ukrain Joint Conference

11-12 April 2oo6 Miskolc11-12 April 2oo6 Miskolc

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Why Clad is important?Why Clad is important?In European reactors: crack can propagate from clad –mostly no crack arrest curve!

The highest stress peak during PTS: at clad-base material interface

After some mm-es much less stress

Without the knowing of irradiated clad properties, no elastic-plastic analysis!!

The best mitigation is to reduce unnecessary conservatives

Dave-Bessy event. Clad as structural material saved the unit



33


WWER 440 weld with claddingWWER 440 weld with claddingSurface or underclad crackSurface or underclad crack??

WeldWeld

Base materialBase material140 mm140 mm



44


Stresses in cladding at a PTSStresses in cladding at a PTS



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Crack tip in claddingCrack tip in cladding



66


Difference between elastic and elastic Difference between elastic and elastic plastic analysisplastic analysis

0 25 50 75 100 125 150

-200

0

200

400

600

800

1000

Time: 100 [s]t [Mpa]

Le-1 Le-2 Le-3 Ep

Wall thickness [mm]



77


What is cladding?What is cladding?

Austenitic steel (ductile, corrosion Austenitic steel (ductile, corrosion resistant, tough)resistant, tough)

However it has :However it has :

Welded structureWelded structure

With 3-10% delta ferrit content to With 3-10% delta ferrit content to avoid hot crackingavoid hot cracking



88


What is cladding?What is cladding?

Austenitic steel (ductile, corrosion Austenitic steel (ductile, corrosion resistant, tough)resistant, tough)

However it has :However it has :

Welded structureWelded structure

With 3-10% delta ferrit content to With 3-10% delta ferrit content to avoid hot crackingavoid hot cracking



99


Template from Greifswald unit 8Template from Greifswald unit 8



1010


UT test resultsUT test results

Size 10 Size 10 is is about 2 about 2 mm mm gas gas bubblebubble

1blokk

0

50

100

150

200

250

300

350

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950

[mm]

size=4

size=5

size=6

size=7

size=8

size=9

size=10



1111


The Ni content in clad and base material The Ni content in clad and base material (sharp transition)(sharp transition)

0 2 4 6 8 10 12 14

0

2

4

6

8

10

12

A Ni tartalom változása a plattirozásban és az átmeneti rétegben

Ni [

%]

Távolság a felszintõl [mm]1 th Hungarian-Ukrain Joint Conference1 th Hungarian-Ukrain Joint Conference


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Big grain sizes, annealing further increases Big grain sizes, annealing further increases themthem



1313


Typical defect in SA strip cladding weldTypical defect in SA strip cladding weld



1414


Brittle and ductile fracture surface in Brittle and ductile fracture surface in cladclad



1515


FZR Charpy testingFZR Charpy testing

0

10

20

30

40

50

60

70

-100 -50 0 50 100 150 200

temperature in °C

impa

ct e

nerg

y in

J

Cladding Greifswald Unit 8

Poly. (Cladding GreifswaldUnit 8)



1616


Charpy results (note the reduction of upper shelf energy)

-100 -50 0 50 100 150 200 250 3000

25

50

75

100

125

150

41 J

Irradiated

Thermal agedAs received

Abs

orbe

d en

ergy

[J]

Temperature [°C]



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Thermal ageing

0 2000 4000 6000 8000 100000

25

50

75

100

125

150

175

200

225

250

Thermal ageing of SZV08H19N10G2B type claddingRussian literature

Clad1réteg Clad2.réteg HAZ

Ab

sorb

ed e

ner

gy

[J]

Thermal ageing at 350°C [hours]



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FZR J integral measurementFZR J integral measurement

0

50

100

150

200

250

300

350

0.0 0.5 1.0 1.5 2.0 2.5a in mm

J in

kN

/m

specimen 177; T = -50°Cspecimen 178; T= 21°Cspecimen 179; T = 150°C



1919


Toughness of clad Toughness of clad Y. Nikolaev (Kurchatov Institute)Y. Nikolaev (Kurchatov Institute)

The highest values are in the PTS relevant temperature range



2020




2121


Tensile resultsTensile resultsTensile test on cladding

0

100

200

300

400

500

600

700

800

1 2 3 4Irradiation state

MP

a

Rp02 at 20°C

Rm at 20°C

Rp02 at 300°C

Rm at 300 °C

.

Elongation of cladding

0

5

10

15

20

25

30

35

1 2 3 4

Irradiation state

A5

[%

] Elongation at20°C

Elongation at300°C

1.1. Cladding layer 1 as receivedCladding layer 1 as received

2.2. Irradiated 0.8*10Irradiated 0.8*102020 n/cm n/cm22 E>1MeV E>1MeV

3.3. Irradiated 2*10Irradiated 2*1020 20 n/cmn/cm2 2 E>1MeVE>1MeV

4.4. Annealed 475°C 100 hours and reirradiated 2*10Annealed 475°C 100 hours and reirradiated 2*102020 n/cm n/cm2 2 E>1MeVE>1MeV1 th Hungarian-Ukrain Joint Conference1 th Hungarian-Ukrain Joint Conference


2222


Future questionsFuture questionsThe unknown unknown!The unknown unknown!

1. Methodology for integrity assessment considering cladding?

2. Which properties are necessary for PTS assesment

3. What properties the regulators will accept: trend curve of:

yield stress

fracture toughness

elongation1 th Hungarian-Ukrain Joint Conference1 th Hungarian-Ukrain Joint Conference


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Thank you Thank you for your attentionfor your attention!!



Documents

Hungarian Academy of Sciences KFKI Atomic Energy Research Institute Behaviour of irradiated RPV cladding F. Gillemot, M. Horváth, G. Úri, H-W. Viehrig,