Reactor Vessel Cladding

7/26/2019 Reactor Vessel Cladding

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Nuclea r Eng inee r ing and Des ign 98 (1987) 171-193 171

No r t h - Ho l l a n d , Am s t e r d a m

R E A C T O R V E S S E L C L A D D I N G S E P A R A T E E F F E C T S S T U D I E S

W . R . C O R W I N

Me tals and Ce ramic s D ivi sion Oak R idge Nat ional Laboratory Oak R idge TN 37831 USA

Received 21 Apri l 1986

The exis tence of a layer of to ugh weld overlay c ladding on the in ter ior of a l ight-water reactor pressure vessel could mit igate

dam age caused d urin g cer ta in overcooling t ransients . The poten t ia l benefi t of the c ladding is that i t could keep a short surface

f law, wh ich wou ld o therwise become long , f rom g row ing e i the r by imped ing c rack in i t i a t ion o r b y a r re s t ing a runn ing c rack.

Tw o aspects cr i t ical to c ladding behavior wil l be reported: i r radia t ion effects on c ladding toughn ess and the respon se of

mec hanical ly loaded, f lawed s t ructures in the presence of c ladding.

A two-phase i r r ad ia t ion expe r imen t is be ing conduc ted . In the f i rs t phase , Cha rpy impac t a nd t ens i le spec imens f rom a

single wire , subm erged-arc s ta inless s teel weld overlay were i r radia ted to 2 1 23 n e u t r o n s / m2 ( > 1 MeV) a t 288 C. Typ ica l ,

good qu al i ty pressure vessel c ladd ing exhibi ted very l i t t le ir radia t io n-indu ced degrad at ion. How ever , duct i le- to-b r i t t le

t ransi t io n behavior , caused b y tem peratur e-dep enden t fa i lure of the res idual 8-ferr i te , was observed. In co ntrast , specim ens

f rom a h igh ly d ilu t ed , poor qua l i ty we ldm en t were m arked ly embr i t fl ed . In the second phase o f i r r ad ia t ions , now in p rog ress, a

comm erc ia lly p roduced th ree -wi re se ri es a rc we ldm en t wi l l be eva lua ted und e r iden t i ca l i r r ad ia t ion and t e s t ing cond i t ions a s

the f i rs t ser ies . In addi t ion, 0 .5T compact specimens of both weldments and higher f luences wil l be examined.

A two-phase p rog ram i s a lso be ing conduc ted u t i l i z ing r e l a t ive ly l a rge ben d spec imens tha t have been c l ad and f lawed on

the tens ion surface. T he tes t ing ra t iona le is that i f a surface f law is p inn ed by the c lad ding and can not grow longer , i t wi l l a lso

not grow beyond a cer ta in depth, thereby arrest ing the ent i re f law in a s t ress f ie ld in which i t would otherwise propagate

through the specimen. The resul ts of phase one showed that s ingle wire c ladding with low-to-moderate toughness appeared to

have a l imited abi l i ty to mit igate crack propa gat ion. F or the second phase, three-wire c lad ding has been deposi ted on a base

p la t e wi th a ve ry h igh duc t i l e - to -b r i tt l e t rans i t ion t empera tu re a l lowing t e s ting to a sce r t a in the c rack inh ib i t ing capab i l i ty o f

tough u ppe r she l f c l add ing .

1 . I n t r o d u c t i o n

I t h a s b e e n p r o p o s e d t h a t t h e e x i s t e n c e o f a l a y e r o f

t o u g h w e l d o v e r l a y c l a d d i n g o n t h e i n t e r i o r o f a l i g h t -

w a t e r r e a c to r ( L W R ) p r e s su r e v e s se l co u l d m i t ig a t e

d a m a g e c a u s e d d u r i n g c e r t a i n o v e r c o o l i n g t r a n s i e n t s .

T h e p o t e n t i a l b e n e f i t o f t h e c l a d d i n g i s t h a t i t c o u l d

k e e p a s h o r t s u r f a c e f l a w , w h i c h w o u l d o t h e r w i s e b e -

c o m e l o n g , f r o m g r o w i n g e i t h e r b y i m p e d i n g c r a c k

i n i t i a t i o n o r b y a r r e s t i n g a r u n n i n g cr a c k . I f th i s c a n

i n d e e d b e p r o v e n , t h e i m p l i c a t i o n s f o r e x i s t i n g L W R s ,

p a r t i c u l a r l y t h o s e w i t h s u b s t a n t i a l r e a c t o r p r e s s u r e v e s -

s el ( R P V ) e m b r i t t l e m e n t , w o u l d b e s i g n if i ca n t . I t w o u l d

* Resea rch sponso red by the Of f i ce o f Nuc lea r Regu la to ry

Resea rch , U.S . Nuc lea r R egu la to ry Com miss ion , unde r In -

teragency Agreements DOE 40-551-75 and 40-552-75 with

the U.S . Depa r tmen t o f Ene rgy unde r con t rac t DE-AC05-

840R21400 wi th M ar t in M ar ie t t a Ene rgy Sys tems , Inc .

c o n t r i b u t e t o u s e a b l e v e s s e l l i f e t i m e s b e y o n d t h e c u r r e n t

s c r e e n i n g c r i t e r i a i f u s e d i n a p l a n t s p e c if i c a n a l y s is .

M o r e o v e r , i f c o n s i d e r a t i o n o f c l a d d i n g b e n e f i t r e s u l te d

i n r e d u c i n g t h e f l a w s i z e o r d e n s i t y d i s t r i b u t i o n s c u r -

r e n t l y b e i n g a s s u m e d , a r e d u c t i o n w o u l d r e s u lt i n t h e

c u m u l a t i v e f a i l u r e p r o b a b i l i t y c a l c u l a t e d u s i n g p r o b -

a b i l i s t ic r is k a s s e s s m e n t m e t h o d o l o g i e s .

T o a s s e s s t h e p o t e n t i a l b e n e f i t s o f c l a d d i n g , a t l e a s t

t w o a r e a s m u s t b e a d d r e s s e d , ( 1 ) t h e r e s i d u a l t o u g h n e s s

o f c l a d d i n g f o l l o w i n g i r r a d i a t i o n t y p i c a l o f L W R s e r vi c e ,

a n d ( 2 ) th e m e c h a n i c a l e f fe c t c l a d d i n g w o u l d h a v e o n a

s t r u c tu r e w h e n l o a d e d u n d e r c o n d i t i o n s r e le v a n t t o a

p o s t u l a t e d a c c i d e n t . T h e H e a v y S e c t i o n S t e e l T e c h n o l -

o g y ( H S S T ) p r o g r a m h a s e s t a b li s h e d t w o - p h a s e r e s e ar c h

e f f o r t s i n b o t h o f t h e s e a r e a s. T h e f i r s t p h a s e i n b o t h

a r e a s h a s b e e n c o m p l e t e d . A l a b o r a t o r y s u b m e r g e d a r c

o v e r l a y w e l d m e n t h a s b e e n e x a m i n e d f o r b o t h i t s ra d i a -

t i o n r e s p o n s e a n d i t s s t r u c t u r a l e f f e c t s o n a l a b o r a t o r y

e n g i n e e r i n g s tr u c t u r e , a c l a d p l a t e l o a d e d i n b e n d i n g .

0 0 2 9 - 5 4 9 3 / 8 7 / 0 3 . 5 0 E l s e v i e r S c i e n c e P u b l i s h e r s B .V .

( N o r t h - H o l l a n d P h y s ic s P u b l i s h i n g D i v i s i o n )


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14/ R Corw tn / Reac tor vesse l c ladding separate e f fec ts s tudies

T h e s e r e s u l t s h a v e b e e n p r e v i o u s l y r e p o r t e d [ 1,2 ] a n d

w i l l b e s u m m a r i z e d h e r e . I n t h e s e c o n d p h a s e , w h i c h

w i l l a l s o b e d e s c r i b e d , s i m i l a r e x p e r i m e n t s a r e b e i n g

c o n d u c t e d u s i n g a c o m m e r c i a l l y p r o c u r e d t h r e e - w i r e

s e r i e s a r c w e l d o v e r l a y , t y p i c a l o f c l a d d i n g a p p l i c a t i o n s

i n t h e p r o d u c t i o n o f e a r l y R P V s .

2 . T e s t m a t e r i a l s P h a s e o n e

T h e s p e c i m e n s f o r b o t h p r o g r a m s w e r e t a k e n f r o m

l a b o r a t o r y w e l d m e n t s f a b r i c a t ed b y t h e a u t o m a t e d

s i n g le - w i r e o s c i l l a ti n g s u b m e r g e d a r c p r o c e d u r e . T h e

w e l d m e n t s c o n s i s t e d o f a l o w e r l a y e r o f t y p e 3 0 9 s t a i n -

l e s s st e e l d e p o s i t e d o n A 5 3 3 g r a d e B c l a ss 1 p l a t e ,

f o l l o w e d b y o n e o r t w o l a y e r s o f t y p e 3 0 8 s t a i n l e s s s t e e l

c l a d d i n g [ 1]. T h e w e l d m e n t s w e r e p o s t w e l d h e a t t r e a t e d

( P W H T ) a t 6 2 1 C f o r 4 0 h, t yp i c a l o f c o m m e r c i a l

p r a c t ic e . T h r e e l a y e r s o f c l a d d i n g w e r e r e q u i r e d t o

p r o v i d e a d e q u a t e t h i c k n e s s f r o m w h i c h t o r e m o v e

i r r a d i a t i o n t e s t s p e c i m e n s . T h e b e a m s p e c i m e n s r e c e i v e d

o n l y t w o l a y e r s o f c l a d d i n g . T h e m u l t i l a y e r p r o d u c t i o n

o f c l a d d i n g c o n t r a s t s w i t h t y p i c a l c o m m e r c i a l U . S . p r a c -

Tab le 1

Chemica l compos i t ion o f over lay we ldments

E lem ent Con ten t ~ (wt )

F i r s t Second Th i rd

layer laye r laye r

C 0.145 0.081 0.065

Cr 13.46 18.52 20.01

N i 6.90 8.81 9.36

M o 0.47 0.27 0.21

M n 1.47 1.47 1.49

Si 0.56 0.70 0.76

Co 0.066 0.092 0.100

Cu 0.14 0.10 0.09

V 0.02 0.04 0.04

A1 0.014 0.010 0.16

Ti < 0.005 < 0.005 0.006

P 0.018 0.021 0.022

S 0.01 0.01 0.01

a Balance Fe, with Nb , < 0.01; Ta, < 0.01; As, < 0.03: and

B, < 0.001 for all layers.

Fig. 1 . The micro structu re of the third lay er of type 308 stainless steel weld overlay is typical of reactor pressu re vessel cladd ing w ith

8-ferri te in an austenite matrix.


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W R Corwin / Reactor vessel cladding separate effects studies 173

r i c e , i n w h i c h a s i ng l e l a ye r o f ove r l a y a pp r ox i m a t e l y 5

m m t h i c k i s a pp l i e d by e i t he r m u l t i p l e w i r e o r s t r i p -

c l a d d i n g s u b m e r g e d a r c p r o c e d u r e s . T h e m a t e r i a l c o m -

pos i t i ons o f e a c h l a ye r o f w e l d m e t a l a r e g i ve n i n t a b l e

1.

M e t a l l o g r a p h i c e x a m i n a t i o n o f t h e c l a d d i n g s h o w e d

t ha t t he t h i r d l a ye r a ppe a r e d t yp i c a l o f LWR s t a i n l e s s

s t e e l ove r l a y , w he r e a s t he f i r s t l a ye r ha d i nc u r r e d e x -

c e s s ive d i l u t i on a s a r e s u l t o f ba s e m e t a l m e l t i ng du r i ng

w e l d i ng . Pho t om i c r og r a phs o f t he t h r e e l a ye r s i l l u s t r a t e

t he r a d i c a l l y d i f f e r e n t m i c r os t r uc t u r e s i n t he f i n i s he d

weldment . The th i rd (upper ) pass ( f ig . 1) shows a d i s t r i -

bu t i on o f 6 - f e r r i t e i n a n a us t e n i t e m a t r i x qu i t e t yp i c a l

o f m i c r o s t r u c t u r e s s e e n i n g o o d p r a c t i c e c o m m e r c i a l

w e l d ove r l a y o f r e a c t o r p r e s s u r e ve s s e ls [ 2 ] . The e f f e c t o f

t he 40 - h PW H T on t he s e m a t e r i a l s is t o pa r t i a l l y

t r a ns f o r m t he 6 - f e r r i t e t o s i gm a pha s e , a s w e l l a s p r e -

c i p i t a te s om e c a r b i de s .

The f i rs t a nd s e c o nd l a ye r s o f c la dd i ng , on t he o t he r

ha nd , f o r m e d a t yp i c a l m i c r os t r uc t u r e s a s a r e s u l t o f t he

e xc e s s ive d i l u t i on ( a pp r ox i m a t e l y 50 ) by t he ba s e m e t a l

a nd f i r s t pa s s w e l dm e n t , r e s pe c t i ve l y . A m oun t s o f d i l u -

t i on i n good p r a c t i c e c l a dd i ng a r e t yp i c a l l y i n t he r a nge

o f 10 t o 25 . The s e c ond l a ye r (f ig . 2 ) c on t a i n s 8 - f e r ri t e

d i s pe r s e d i n a us t e n i t e bu t i n a dd i t i on c on t a i n s l i m i t e d

r e g i ons i n w h i c h m a r t e ns i t e i s a l s o p r e s e n t . Subs e que n t

e x a m i n a t i o n o f t h e f r a c t u r e m e c h a n i s m i n d i c a t e d t h a t

t he m a r t e ns i t e i n t he s e c ond l a ye r d i d no t a pp r e c i a b l y

a f f e c t it s p r ope r ti e s , s uc h t ha t i t be ha ve d ve r y m u c h l i ke

t he t h i r d l a ye r . The f i r s t l a ye r ha d s u f f i c i e n t d i l u t i on t o

m o ve i t e n ti r e l y f r om t he 8 - f e r r i te - f o r m i ng r e g i on o f t he

Sc ha e f f l e r d i a g r a m [ 3 ] a nd i n t o t he a us t e n i t e - p l us -

m a r t e ns i t e r e g i on ( t he s e a r e t he dom i na n t pha s e s a nd

no t a b l y a f f e c t i t s f r a c t u r e p r ope r t i e s ) . Exa m i na t i on o f

i t s micros t ruc ture ( f ig . 3) , however , shows three d i s t inc t

r e g i ons . The us e o f t he f e r r o f l u i d m a gne t i c e t c h i ng

t e c hn i que [ 4 ] a nd s t ud i e s i n t he t r a ns m i s s i on e l e c t r on

m i c r os c ope ve r i f i e d t he t i gh t e s t r e g i ons t o be a us t e n i t e ,

t he l igh t g r a y r eg i ons t e m pe r e d m a r t e ns i t e , a nd t he da r k

r e g i ons 8 - f e r ri t e de c o r a t e d w i t h M23C 6 t ype c a r b i de s .

A l t hough t he i nve s t i ga t i on o f h i gh - d i l u t i on c l a dd i ng

w a s no t t he i n i t i a l a i m o f t he c l a dd i ng s t ud i e s , i t m a y

w e l l be h i gh l y ge r m a ne t o t he que s t i on o f t he e f f e c t s o f

c l a dd i ng on R PV i n t e g r i t y . H i gh ba s e m e t a l d i l u t i on o f

c l a d d i n g , c a u s e d b y i n a d e q u a t e c o n t r o l o f w e l d i n g

p r oc e dur e s , a nd t he r e s u l t i ng m i c r os t r uc t u r e s ha ve be e n

Fig. 2. The secon d layer of the overlay (type 308 stainless steel) includes patches o f martensite (light gray) in add ition to the 8-ferrite

in an austenite matrix.


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174 W.R. Corwin / Reacto r vesse l c ladding separate e f fec ts s tudies

i 4 1 ~ ~ 5 x

Fig. 3. The high base m etal diluti on of the first lowest) layer of cladding, type 309 stainless steel, resulted in a three-phase

microstructure of austenite lightest region), martensite light gray), and 8-ferrite decorated with additi onal carbides black).

d o c u m e n t e d [ 5,6 ] i n c o m m e r c i a l R P V s . T y p i c a l l y , t h e

r e s ul t in g m a t e r i a l h a s p o o r e r m e c h a n i c a l a n d / o r c o r r o-

s i o n p r o p e r t i e s i n t h e u n i r r a d i a t e d c o n d i t i o n ; n o i n f o r -

m a t i o n h a s b e e n p r e v i o u s l y a v a i l a b l e o n t h e i r r a d i a t i o n

d a m a g e o f s u c h m a t e r i a l . I t s i n c l u s i o n h a s p r o v i d e d

i n s i g h t i n t o t h e b e h a v i o r o f s u b s t a n d a r d w e l d o v e r l a y

c l a d d i n g p o s s i b l y r e p r e s e n t a t i v e o f i r r a d i a t e d m a t e r i a l

a c tu a l ly in th e f i e ld .

3 E f f e c t s o f i rr a d i a t io n

3 .1 . E x p e r i m e n t a l d e t a i l s P h a s e o n e

T o e x a m i n e t h e e f f e c ts o f i r r a d i a t i o n o n t h e d i f f e r e n t

m i c r o s t r u c t u r e s , t w o s e t s o f t e n s il e a n d C h a r p y V - n o t c h

s p e c i m e n s w e r e c a r e f u l l y f a b r i c a t e d t o b e c o n t a i n e d a s

f u l l y a s p o s s i b l e w i t h i n e i t h e r t h e u p p e r t w o l a y e r s

n o m i n a l l y t y p e 3 0 8 s p e c i m e n s ) o r t h e l o w e r l a y e r

n o m in a l ly ty p e 3 09 s p e c ime n s ) f ig . 4 ) . A l l s p e c ime n s

w e r e f a b r i c a t e d w i t h t h e s p e c i m e n a x i s p a r a l l e l t o t h e

w e l d i n g d i r e c t io n . T h e C h a r p y s p e c i m e n s w e r e n o t c h e d

o n t h e s u r f a c e p a r a l l e l t o a n d n e a r e r t h e b a s e m e t a l i n

a l l cases .

T h e n o m i n a l l y t y p e 3 08 s p e c i m e n s c o n s i s t e n t l y h a d

f e r r i t e n u m b e r s o f 2 t o 6 c o r r e s p o n d i n g r o u g h l y t o

p e r c e n t a g e s o f f e r r i t e ) , a s d i d t h e p o r t i o n o f n o m i n a l l y

t y p e 3 0 9 s p e c i m e n s c o m p o s e d o f u p p e r w e l d p a s s l a y e rs .

T h e n o t c h e d s i d e o f t h e n o m i n a l l y t y p e 3 0 9 s p e c i m e n s

c l o s es t o t h e b a s e m e t a l i n t e r f a c e e x h i b i t e d f e r r i te n u m -

b e r s u p to a n d in e x c e s s o f 3 0 o f f sc a l e ) . O p t i c a l

e x a m i n a t i o n o f t h e m i c r o s t r u c t u r e o f t h e t y p e 30 9 l a y e r

TYPE

3 8

S P E C IM E N -~ T Y P E 3 0 9

- ~ _ S PE CIM EN

T Y P E ~ W E L D M E T A L

T Y P E 3 0 9 W E L D M E T A L

~ / / / / / / / / / / / / / / / / / / / / / / ~ / / / / / / ~ . ~ - - A 5 3 3 G r. B C L 1

B A S E P L A T E

W E L D I N G D I R E C T I O N

Fig. 4. Location of the Cha rpy specimens nomi nally called

types 308 and 309.


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W . R . C orwi n / R e ac t o r v e s se l c l add i ng s e para t e e f fe c t s s t ud i e s 175

i n d i c a t e s t h e a m o u n t s o f m a r t e n s i t e a n d f e r r i t e to b e 3 0

t o 4 5 a n d 1 0 t o 1 5 , r e s p e c t i v e l y .

i r r a d ia t i o n , w h e n m e a s u r e m e n t s a s lo w a s 2 6 3 C w e r e

r e c o r d e d .

3 .2 . I r r a d i a t i o n h i s t o r y P h a s e o n e

T h e s p e c i m e n s w e r e i r r a d i a t e d i n t h e c o r e o f t h e

2 - M W p o o l r e a c t o r a t t h e N u c l e a r S c i en c e a n d T e c h n o l -

o g y F a c i l i t y , B u f f a l o , N e w Y o r k . T w o s e p a r a t e c a p s u l e s

w e r e u s e d , o n e e a c h f o r t h e t y p e s 3 0 8 a n d 3 0 9 s t a i n l e s s

s t e e l s p e c i m e n s . T h e c a p s u l e s w e r e i n s t r u m e n t e d w i t h

t h e r m o c o u p l e s a n d d o s i m e t e r s a n d w e r e r o t a t e d 1 8 0

o n c e d u r i n g t h e i r r a d i a t i o n f o r f l u e n c e b a l a n c i n g . T h e

c a p s u l e s c o n t a i n i n g t h e t y p e s 3 0 8 a n d 3 0 9 s p e c i m e n s

r e a c h e d a v e r a g e f l u e n c e s o f 2 . 0 9 x 1 0 23 n e u t r o n s / m 2

( > 1 M e V ) + 1 0 d u r i n g 6 7 9 h o f i r r a d i a t i o n a n d 2 . 0 2

1 0 23 n e u t r o n s / m 2 ( > 1 M E V ) + 5 i n 5 0 8 h , r e sp e c

t i v e l y . T h e f l u e n c e s a r e f o r a c a l c u l a t e d s p e c t r u m b a s e d

o n F e , N i , a n d C o d o s i m e t r y w i r e s . T e m p e r a t u r e s w e r e

m a i n t a i n e d a t 2 8 8 _+ 1 4 C e x c e p t f o r t h e i n i t i a l w e e k o f

3 . 3. R e s u l t s a n d d i s c u s s i o n s P h a s e o n e

T e n s i l e t es t i n g w a s c o n d u c t e d a t r o o m t e m p e r a t u r e ,

1 4 9 C , a n d 2 8 8 C . I r r a d i a t i o n in c r e a s ed t h e y ie l d

s t r e n g t h o f t h e t y p e 3 0 9 s p e c i m e n s b y 3 0 t o 4 0 ,

w h e r e a s t h e i n c r e a s e o f t h e t y p e 3 0 8 s p e c i m e n s w a s o n l y

5 t o 2 5 . S u r p r i s in g l y , t h e to t a l e l o n g a t i o n a n d r e d u c -

t i o n o f a r e a o f b o t h m a t e r i a l s i n c r e a s e d d u r i n g i r r a d i a -

t i o n ( t a b l e 2 ) .

T h e e f f e c t o f i rr a d i a t i o n o n t h e C h a r p y i m p a c t p r o p -

e r t i e s o f t h e t y p e 3 0 8 w e l d m e t a l r e p r e s e n t a t i v e o f

t y p i c a l w e l d o v e r l a y c l a d d i n g w a s r e l a t i v e l y s m a l l ( f i g .

5 ). O n l y a v e r y s l i g h t u p w a r d s h i f t i n t r a n s i t i o n t e m p e r -

a t u r e ( 1 5 C ) a n d d r o p i n u p p e r s h e l f ( < 10 ) w er e

o b s e r v e d . B o t h t h e c o n t r o l a n d i r r a d i a t e d C h a r p y s p e c i -

m e n s e x h i b i t e d c u r v e s m o r e t y p i c a l o f f e r r i t i c m a t e r i a l s

t h a n o f a u s t e n i t i c s t a i n l es s s t ee l w i t h r e s p e c t t o t h e

T a b l e 2

Te ns i l e pro pe r t i e s o f s t a in le s s s t e e l c la ddin g be fore a nd a f t e r i r r a d ia t ion a t 288 +_ 14 C

S p e c i m e n M a t e r i a l F l u e n c e , T e s t S t r e n g t h ( M P a )

t y p e a > 1 M e V t e m p e r a t u r e Y i e l d U l t i m a t e

( n e u t r o n s / m 2 ) ( C)

T o t a l

e l o n g a t i o n b

( )

R e d u c t i o n

o f a r e a

( )

CPL -80 309 0 27 299 593

CPL-83 309 0 27 273 586

CPC -72 308 0 27 268 589

CPC-73 308 0 27 276 568

CPL -81 309 2.0 )< 1023 29 388 606

CPL-85 309 2 .0 29 364 624

CPC -70 308 2 .1 29 289 605

CPC-75 308 2 .1 29 300 589

CPL -86 309 0 149 213 448

CPL -89 309 0 149 236 450

CPC -77 308 0 149 221 445

CPC -78 308 0 149 213 444

CP L-82 309 2.0 149 297 508

CP L-87 309 2.0 149 345 526

CPC -71 308 2.1 149 290 501

CP C-7 6 308 2.1 149 262 485

CPL -90 309 0 288 195 429

CPL -91 309 0 288 207 423

CPC -79 308 0 288 205 393

CPC -80 308 0 288 205 402

CPL -84 309 2 .0 288 277 475

CPL -88 309 2 .0 288 290 501

CPC -74 308 2 .1 288 198 422

CPC-81 308 2 .1 288 232 427

28.4

49.5

40.0

42.4

39.4

45.4

51.5

60.1

31.9

30.4

31.3

32.4

57.2

48.6

56.3

53.8

31.7

32.4

28.5

27.6

52.9

56.3

51.9

49.5

30.6

55.5

55.0

58.0

48.0

58.0

62.3

67.1

55.5

63.4

44.0

52.0

57.9

60.4

59.3

58.1

51.5

52.2

51.4

53.3

56.6

59.3

55.0

59.8

a Type 309 c ons i s t s pr im a r i ly of the f i r s t m e ta l pa s s , type 308 pr im a r i ly the th i rd ( l a s t pa s s ) .

b G a g e l e n g t h / d i a m e t e r = 7 .


6/23

1 7 6

V~R Cor wm / Reac tor resse l c ladding separate


7/23


100

90 B

80 --

70 --

30

20

6O

>-

~= o

U

Z

ku

4O

10

-150

w

I:

/ L

i

H ~

l

/ H

H HIGH-ENERGY

/ / POPULATION --

~ J

H ~ H j

i L i

1O0 -5 0 0 50 100 150 200 250

TEMPERATURE (C)

300

Fig. 6. Charpy impact energy of the unirradiated nominally type 309 stainless steel cladding divided into low-and high-energy

populations based on the fraction of type 308 weld metal in the specimen ligament.

8 0

70

6 0

50

>-

(3 40

n,-

t.u

Z

LLI

3O

20

1 0

o

--200 --150

H . . . . . . . .

H H I G H E N E R G Y P O P U L A T I O N

L . . .

L L O W E N E R G Y P O P U L A T I O N

H

. .H . . . . . ' ' ' '

. H

L

L~

7

H

H Lj

L L

L

I I I I I I I 1

100 -- 50 0 50 1O0 150 200 250 300

TEMPERATURE (C)

Fig. 7. Charpy impact energy of the irradiated nominally type 309 stainless steel cladding divided into low- and high-energy

populations based on the fraction of type 308 weld metal in the specimen ligament.


8/23

178 14/. R . C o r w t n / R e a c t o r t ~ es s el c l a d d i n g s e p a r a t e e f J e c t s st u dl e .~

1 o o , , , I I ' I

L O W - E N E R G Y H I G H -- E N E R G Y

P O P U L A T I O N P O P U L A T I O N

9 0 U N I R R A D I A T E D - -

. . . . . . . . . . . . I R R A D I A T E D / * ' ' ~ '=

8 0 - -

70

/ . . . . / . . .. . .. . .. . .

40 ~ / . / ~ ~ ~ , . ~ ...m

/ . / . . - - _

I /

~o / / /

10 ~

0 . I . . I 1 l 1 1 l . I I

- 2 0 0 - 1 5 0 - 1 0 0 - 5 0 0 5 0 1 00 1 50 2 0 0 25 0 3 0 0

T E M P E R A T U R E ( C )

F i g . 8 . E f f e ct o f i r r a d i a ti o n o n t h e C h a r p y i m p a c t e n e r g y o f h i g h a n d l o w e n e r gy p o p u l a t i o n s o f t h e s p e c i m e n s o f n o m i n a l l y t y p e 3 09

c la dding .

IOOOX

Fig. 9 . The low te m pe ra ture f r a c ture pa th in type 309 c la dding sho wn fo l lowing pa tc he s of f e r r i te .


9/23


z O p m

OOOX

Fig. 10 . The low te m p e ra ture f r a c ture pa t h of type 308 c la dd ing show n fo l lowing 8- fe r r i t e i s l a nds .

t 2 0 p m I O 0 0 X

Fig . 11 . The prof i l e of the f r a c ture pa th of type 309 s ta in le s s s t e e l shows tha t the f r a c ture doe s not pre fe re nt i a l ly fo l low the f e r r i t e

g r a y p a t ch e s ) , a s o p p o s e d t o t h e m a t r i x o f t h e a u s t e n i t e a t h i g h e r t e m p e r a t u r e s .


10/23

180 W.R. ( orwin / Reactor vessel cladding separate ef/e( ts studie~

i

i . . ~ . I .

2 ~ m j IO X

Fig. 12. The profile of the fracture path of type 308 stainless steel shows that the fracture does not preferentially follow the 8-ferrite

gray patches) at higher temperature.

stainless steel weldments since the ferritic phases con-

trolling the fracture are i nherentl y rate, as well as tem-

perature, sensitive. If the cladding on the interior of a

reactor pressure vessel is to be considered structural in

nature, then the potent ial for its rate sensitivity should

also be considered.

3 .4 . C o n c l u si o n s f r o m P h a s e o n e a n d p l a n s f o r P h a s e t w o

Based on a single irradiation experiment, very little

degradation of the notch-impact toughness of good

quality cladding would be expected. In fact, both the

tensile strength a nd the fracture ductilit y were improved

slightly by irradiation. It mus t be stressed, however, that

this is only a single case and that no conclusions,

positive or negative, can be drawn regarding welding

procedures or c ompositions leading to material different

from that studied here.

Results from the highly diluted type 309 weld metal

show appreciable radiation-induced degradation of

notch-impact toughness, even though both the tensile

strength and the tensile fracture ductilit y were improved

slightly by irradiation. In the few documented cases

where welding has produced abnormal cladding with

excessive dilution in ope rating reactors, the radiation

effects on notch-impact toughness may be cause for

concern.

By and large, the results obtained in phase one were

more encouraging than some of the indications of

irradiat ion-indu ced degradation reported in a recent

litera ture review [11]. Therefore, to c orrobora te the re-

suits of phase one and to obtain additional data for

materials and irradiation conditions specifically of in-

terest in LWRs phase two was initiated.

The irradiations for phase two are currently in pro-

gress and should be completed early in 1986. Two

capsules containing tensile, impact, and 0.5T compact

specimens will be irradiated to 2 x 1023 ne ut ro ns /m2

> 1 MeV) with an additional capsule of tensile and

impact specimens reaching 5 10 23 neu tr on s/ m2 > 1

MeV). The material being examined is primarily taken

from a commercially produced overlay weldment fabri-

cated using the three-wire series arc procedure. The

commercial weldment is also composed of three layers

but with extreme care taken to assure the metallurgical,

chemical, and mechanical properties of all layers are


11/23

W.R. Corwin / Reactor vessel cladding separate effects studies

181

s i m i l a r . P r e l i m i n a r y r e s u l t s h a v e s h o w n t h a t t h e u n -

i r r a d i a t e d p r o p e r t i e s o f t h e t h r e e - w i r e s e r i e s a r c c l a d - .

d i n g a n d t h e g o o d q u a l i t y t y p e 3 0 8 c l a d d i n g f r o m t h e

f i r s t s e r i e s e x h i b i t v e r y s i m i l a r u n i r r a d i a t e d f r a c t u r e

b e h a v i o r .

I n a d d i t i o n , t w o s e t s o f c o m p a c t s p e c i m e n s f r o m t h e

m a t e r i a l u s e d i n p h a s e o n e h a v e b e e n i n c l u d e d . T h e

s p e c i m e n s w e r e f a b r i c a t e d s u c h t h a t t h e t i p o f t h e

p re c ra c k i s i n th e ty p e 3 0 8 s t a in l e s s fo r o n e s e t a n d in

th e ty p e 3 0 9 fo r t h e o th e r . T h e s e s p e c im e n s w i l l b e u s e d

t o c o n f i r m t h e b e h a v i o r a l t r e n d s s h o w n b y t h e i m p a c t

s p e c i m e n s i n p h a s e o n e .

4 . S t ru c tu ra l e f f e c t s of c l dding

4.1. Testing scheme Phase one

T o e x a m i n e t h e s t r u c t u r a l e f f e c t s o f w e l d o v e r l a y

c l a d d i n g i n a s t r e s s st a t e r e l e v a n t t o a n o v e r c o o l i n g

t r a n s i e n t , a s t u d y w a s u n d e r t a k e n i n w h i c h r e l a t i v e l y

l a rg e p l a t e s 9 1 4 4 0 6 5 1 m m ) w e re c l a d o n o n e s id e

a n d t e s t ed i s o t h e r m a l l y i n f o u r - p o i n t b e n d i n g . T h e c l a d

s u r f a c e w h i c h w a s p l a c e d i n t e n s i o n b y b e n d i n g c o n -

t a i n e d a s u r f a c e f l a w . T h e f l a w w a s a n e l e c t r o n b e a m

w e l d , w h i c h w a s d e s i g n e d t o f r a c t u r e u n d e r s t a t i c l o a d -

i n g w h e n h y d r o g e n c h a r g e d . T h i s w a s t o e n a b l e u s t o

i n i t i a t e f a s t r u n n i n g f r a c t u r e i n t h e s u r f a c e f l a w o n t h e

p l a t e u n d e r a r b i t r a r y i n i t i a l l o a d i n g c o n d i t i o n s .

I t w a s a n t i c i p a t e d t h a t a s m a l l s e m i e l l i p t i ca l f l a w

c o u l d b e s i z e d a n d t h e t e m p e r a t u r e a n d s t r e s s s t a t e s

c h o s e n s o t h a t t h e t e s t w o u l d r e s u l t i n t h e f r a n g i b l e

f a i l u r e o f a n u n c l a d s p e c i m e n , b u t w o u l d p o p - i n a n d

a r r e s t i n a c l a d s p e c i m e n . T h i s w a s e x p e c t e d b e c a u s e o f

t h e p o s t u l a t e d i n t e r a c t i o n b e t w e e n t h e c l a d d i n g a n d t h e

r u n n i n g c r a c k .

4.2. Exper iment al rationale Phase one

T h e r a t i o n a l e f o r t h e e x p e r i m e n t c a n b e u n d e r s t o o d

b y c o n s i d e r i n g t h e v a r i a t i o n o f t h e s t r e ss i n t e n s i t y f a c t o r

S I F ) a t m a x i m u m d e p t h a n d a t t h e s u r f a c e o f a g r o w -

i n g s e m i e l l i p t i c a l p a r t - t h r o u g h f l a w i n a n u n c l a d p l a t e

v s . t h e s a m e v a lu e s fo r a f l a w th a t h a s b e e n a r r e s t e d a t

th e s u r fa c e ; t h a t i s , i n th i s s e r i e s o f t e s t s , b y th e c o n t r i -

b u t io n o f t h e s t a in l e s s s t e e l c l a d d in g . F ig . 1 3 s h o w s a

p lo t o f t h e S I F a s c a l c u la t e d b y th e Me rk le [1 2, 13 ]

m e t h o d f o r c o n s t a n t l e n g t h 5 7 - a n d 7 6 - m m - l o n g p a r t -

t h r o u g h f l a w s as a f u n c t i o n o f a /w u n d e r p u r e m o m e n t

l o a d i n g , w i t h t h e s u r f a c e s t r es s a p p r o a c h i n g t h e m a t e r i a l

y i e ld s s t r e s s . F ro m f ig . 1 3 , n o te th a t a t a v a lu e o f a / w

o f - 0 . 2 4 t h e S I F s a t t h e m a x i m u m d e p t h a n d a t t he

s u r fa c e 0 = 0 a n d ~ r /2 , r e s p e c t iv e ly ) a re e q u a l fo r t h e

5 1 - m m - l o n g f l a w . A s i m i l a r s i t u a t io n e x i s t s f o r t h e

s o m e w h a t l a r g e r 7 6 - r a m f l a w a t a n

a / w

va lu e o f - 0 .3 .

F ig . 1 4 s h o w s a p lo t o f S IF v a lu e s fo r tw o f l a w s i z e s in

a n u n c l a d 5 1 - m m - t h i c k s p e c i m e n u n d e r p u r e b e n d i n g .

F o r a p p r o p r i a t e l y s e l e c t ed t e m p e r a t u r e c o n d i t i o n s s u c h

th a t K ic ~< 5 7 MP a v rm , th e p lo t i n d ic a t e s th a t w i th o u t

c l a d d i n g , a f l a w , o n c e i n i t i a t e d , g r o w s b o t h l o n g e r a n d

d e e p e r . F ig . 1 5 , p lo t t e d f ro m th e v a lu e s g iv e n in f ig . 1 3

s h o w s t h a t f o r a f i x e d f la w l e n g t h o f 76 m m , t h e S I F a t

t h e m a x i m u m d e p t h 0 = 0 ) i n c re a se s a n d t h en d e -

c r e a s e s w i t h d e p t h , w h i l e i t c o n t i n u o u s l y i n c r e a s e s a t

t h e s u r f a c e 0 = ~ r/ 2 ) f o r a d e e p e n i n g f l a w w h e n s u b -

j e c t e d t o p u r e b e n d i n g , w i t h t h e s u r f a c e s t re s s a p p r o a c h -

i n g t h e b a s e m a t e r i a l y i e l d . T h e s e c o n d i t i o n s i m p l y t h a t

fo r K ic - 4 0 MP aV rm in th e b a s e m e ta l , a s e m ie l l ip t i c a l

1 3 - m m - d e e p f l a w , i n i t i a t e d b y t h e h y d r o g e n - c h a r g i n g

p o p - i n p r o c e d u r e , w o u l d g r o w in d e p t h a n d l e n g t h u n t i l

r e a c h in g th e s t a in l e s s c l a d d in g . A t th i s p o in t , i f t h e

c l a d d i n g h a s a n e f f e ct i v e t o u g h n e s s ~< 1 25 M P a f m , t h e

f l a w w o u l d b e s t o p p e d f r o m f u r t h e r i n c r e a s e s i n l e n g t h

o r d e p t h .

4.3. Test specimens and materials Phase one

S p e c i m e n s w e r e d e s i g n e d a s r e c t a n g u l a r p l a t e s w i t h

f o u r - p o i n t l o a d i n g t o a c h i e v e a c o n s t a n t - m o m e n t l o a d -

i n g i n t h e c e n t r a l z o n e o f t h e s p e c i m e n w i t h i n w h i c h a n

E B - w e ld f l a w w a s p l a c e d f ig . 1 6 ). T h e s t a in l e s s s te e l

c l a d d i n g w a s a p p l i e d o v e r t h e c e n t r a l a r e a o f t h e s p e c i -

m e n , a n d a n a r r o w s l o t w i n d o w w a s t h e n m a c h i n e d

t h r o u g h t h e s t a in l e s s c l a d d i n g d o w n t o t h e b a s e m e t a l

p r i o r t o a p p l i c a t i o n o f t h e E B - w e l d f l a w .

T h r e e t y p e s o f s p e c i m e n s w e r e f a b r i c a t e d , u n c l a d

s p e c i m e n s a n d s p e c i m e n s c l a d w i t h e i t h e r a m o d e r a t e

t o u g h n e s s o r a l o w t o u g h n e s s c l a d d i n g . T h e u n c l a d

s p e c i m e n s w e r e t o d e m o n s t r a t e t h e l a c k o f c l a d d i n g

i n d u c e d a r r e s t a n d c o n s e q u e n t c o m p l e t e f a i l u r e o f t h e

p l a t e u n d e r t h e s a m e c o n d i t i o n s u n d e r w h i c h a c l a d

b e a m w o u l d a f f e c t a r r e s t . T h e s p e c i m e n s c l a d w i t h a

m o d e r a t e t o u g h n e s s o v e r l a y , t h e t y p e s 3 0 9 / 3 0 8 w i t h

P W H T d i s c u s se d p r e v i o u s ly , w e r e d e s i g n e d t o s i m u l a t e

c l a d d i n g p r o p e r t i e s t y p i c a l o f b e g i n n i n g o f l i f e i n a n

R P V . T h e l o w t o u g h n e s s c l a d d i n g , a s ig m a p h a s e e m -

b r i t t l e d t y p e 3 1 2 , w a s d e s i g n e d t o s i m u l a t e d p o t e n t i a l

e n d o f l i f e p r o p e r t i e s . B o t h t y p e s o f c l a d d i n g w e r e l e s s

t o u g h t h a n d e s i r e d , t h e t y p e s 3 0 9 / 3 0 8 f o r t h e r e a s o n s

d i s c u s s e d p r e v i o u s l y . T h e b e a m s c l a d w i t h t y p e 3 1 2

c l a d d i n g w e r e s o b r i t t l e l i t t l e u s e f u l i n f o r m a t i o n w a s

g a i n e d f r o m t h e m a n d t h e i r r e s u l t s a r e n o t r e p o r t e d

h e re .

C h a r p y V - n o t c h i m p a c t , t e n s i l e , a n d f r a c t u r e t o u g h -


12/23

] 82 W.B. Corw i n / R e ac t o r e s~e l c / add m g s e para t e e f j e c t s s t ud i e s

_

1 20 - - / - -

110 ~ /

0

100 ~ 2b = 51 cm ---~

90 ~ y

o

~ 2b = 7.6

c m

Q.

6 o w

50

O

I ~.~ ~k

SOLID POINTS: K (~'/2)

4 0 - -

/ / / ~ X

OPEN POINTS: KI 101

30 ~ 2b= 5 lcm-J ~O ~K/ /b=5 1cm / AT0:0

1

K

A T

0 ~/2

o

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

a/w

Fig. 13. KI variations with crack depth for a part-through surface crack of constant surface length in a 51-mm-thick plate under pure

bending.

ness testing was performed on both the cladding and

the base metal. The Charpy impact data of the nominal

type 309 low and high energy populations described

earlier are the most germane to the plates as they

represent composite fracture data of the first and sec-

ond layers of cladding. They are plotted for comparison

with the Charpy da ta for the base plate A 533 grade B

class 1 i n both the LT and LS orientations repre-

S T R E S S

D I S T R I B U T I O N

( M P a )

K I = 5 7 M P a v - m 8 1 4 1 3 . 7

4 1 3 . 7

Fig. 14. Predicted stress intensity for semielliptical flaws in 51-mm-thick unclad plate under pure bending.


13/23


5

m m

J - 7 6 m m

I

/ / / / / / / / / / / / / / / / / / / A 2 2 I I / /

t

K AT 0 = 0 ~ J

( M P a

_1

r

2 2 V / / / / / / / / / / / / / / / / / / Z

K t A T 0 = 7r /2

S T R E S S

D I S T R I B U T I O N

( MPa)

/ j 4 1 3 . 7

4 1 3 . 7

Fig. 15. Predicted stress intensity for 76-mm-long flaws in 51-mm-thick clad plate under pure bending.

senting crack propagation across and into the plates,

respectively fig. 17). For ana lysis purposes, all CVN

energy vs. temperature data were fitted with a hyper-

bolic tangent function. Even though the impact data of

the high and low popul ations diverge at higher tempera-

tures, the impact energy of both sets of cla dding was 12

to 13 J at the plate test tempe rature, only shghtly higher

than that of the base plate, 7 to 10 J. In contrast the

quasi-static initiation toughness of cladding, Kj, was

almost three times that of the base plate table 3).

Whether this is due to rate effects related to the failure

of the 8-ferrite in the cladding or other causes was not

determined. The - 40 C test temperat ure was chosen

to assure a frangible failure in the base plate which had

a drop weight NDT of -18C. Results of tensile test-

ing at -4 0 C are shown in table 4.

To provide baseline values on the material used as

the base plate, crack-arrest testing was also performed.

Crack-arrest specimens were fabricated from broken

halves of the clad-plate specimens in the LT orientation.

P/2

MBASE

E T A L

STAINLESS

C L A D D I N G

P/2

FL

DIMENSIONS IN CENTIMETERS

Fig. 16. Specimen dimensions and load locations.


14/23

184 W . R . C orwi n R e ac t o r t ;e s se l c l add i ng s e para t e e ff e c ts s t ud i e s

2 0 0

1 7 5

1 5 0

1 2 5

i 1 0 0

z s

|

0 . . . . . . . 0

O - - - - C ]

V - - - - I F

I I I

B A S E P L A T E ( LS ) . . . . . . ~ . . . . .

B A S E P L A T E ( L T ) . ~ ' ~ - O - - -

C L A D D I N G o ~

( H I G H E N E R G Y . ~

P O P U L A T I O N ) ) /

C L A D D I N G

( L O W E N E R G Y /

P O P U L A T I O N ) ) .

I ' ' '

s

5 T S T T M PERATURE

3 1 ~ 1 ~ / _ - - - B A S E P L A T E

O T

- 2 0 0 - 1 0 0 0 1 0 0 2 0 0 3 0 0


Fig. 17 . The im p a c t tou ghne ss of the c la dd ing s l igh t ly e xc e e ds tha t of the ba se p la te a t the t e s t t e m p e ra ture of the c la d p la te s .

T h i s o r i e n t a t i o n c o r r e s p o n d e d t o t h e e x t en s i o n o f t h e

f l a w i n t h e c l a d - p l a t e e x p e r i m e n t s a c r o s s t h e w i d t h o f

t h e p l a te . T h e s p e c i m e n s w e r e o f t h e w e l d - e m b r i t t l e d ,

t r a n s v e rs e - l o a d ed , s p - p i n t y p e r e c o m m e n d e d b y t h e

l a te s t d r a f t o f th e p r o p o s e d A S T M s t a n d a r d o n c r a ck -

a r r e s t t e st i n g . T h e y w e r e 2 5 . 4 m m t h i c k w i t h p l a n a r

d i m e n s i o n s o f 1 5 2 . 4 m m a n d 1 4 8 . 2 m m . T h e s e d a t a

a l lo w a d i r e ct c o m p a r i s o n t o b e m a d e b e t w e e n t h e

v a l u e s o f c r a c k a r r e s t c a l c u l a t e d f o r t h e c l a d p l a t e s a n d

T a b l e 3

Fra c ture toughne ss of m a te r ia l s use d in the c la d p la te t e s t s

Ma te r ia l Spe ci - Te m pe ra - Or ie n ta - j a

m e n t u re t i on ( M p a f m )

N o ( C )

A-533 gra de B CPA 100 b - -40 LT 56 .8

c l a ss 1 C P A 1 0 1 b - 4 0 L T 8 0 .4

Ave ra ge 68 .6

308 /30 9 SS CP218 ~ - 40 a 191 .0

w e l d m e t a l C P 2 1 9

c

40 d 193.0

Ave ra ge 192.0

a C a l c u l a t e d f r o m J a t m a x i m u m l o a d u s i n g K f = E J .

b 1T-CT spe c im e n.

c P r e c r a ck e d C h a r p y V - n o t c h s l o w - b e n d s p e ci m e n .

a A s sho wn in f ig . 4 .

t h o s e o f t h e b a s e p l a t e i t s e lf t o d e t e r m i n e i f t h e c l a d d i n g

d i d i n d e e d e n h a n c e t h e s t r u c t u r a l r e s i s t a n c e o f t h e c l a d

s t r u c t u r e .

4 . 4. T e s t i n g e q u i p m e n t a n d s e q u e n c e - P h a s e o n e

A n e x i st i n g 1 - M N s e r v o -h y d r a u l ic t e s t in g m a c h i n e

w a s m o d i f i e d t o i m p o s e f o u r - p o i n t b e n d i n g o n t h e

s p e c i m e n s ( fi g . 1 8 ). I n a d d i t i o n t o a p p l y i n g t h e c o n -

t r o l l e d l o a d i n g , t h e f i x t u r e w a s a l s o d e s i g n e d t o e l i m i n a t e

i n - p l a n e l o a d i n g a s a r e s u lt o f b e a r i n g c o n s t r a i n t c a u s e d

b y t e m p e r a t u r e c h a n g e s d u r i n g t h e l o a d i n g p r o c e s s .

T a b l e 4

Te ns i l e prope r t i e s of m a te r ia l s use d in the c la d-p la te t e s ts

Ma te r ia l Te m p e ra - S t r e ngth Duc t i l i ty

ture (MPa ) (%)

( C ) Y i e ld U h i - E l o n g a - R e d u c t i o n

m a t e t i o n b o f a r e a

A-533 gra de B

c la s s1 -4 0 490.8 685.4 20 .7 61 .7

3 0 8 / 3 0 9 S S

we ld m e ta l -4 0 324.7 874.7 43 .7 47 .0

a Ave ra ge of two spe c im e ns , 4 .52 m m in d ia m e te r .

b Ga g e l e ngth - to-d ia m e te r r a t io = 7 .


15/23


R E A C T I O N

B E A R I N G- . - -

I N s T R o N 2 0 0 - k i p

T E S T I N G M A C H I N E

J C K B O L T S

i

r , q E M

~ ~CROSSHEAD

R E A C T IO N ~ ~ P-- ,l

R E A C T I O N A N C H O R

I I I L ~ - - S H I E L D

JO

E ~

L(3 ~D

C E . L

i

L J

I t A s E

Fig. 18. Section elevation of clad plate task test setup.

O t he r f e a t u r e s i nc o r po r a t e d w i t h t he m od i f i c a t i on i n -

c l ude d a l i qu i d - n i t r oge n c oo l i ng s ys t e m f o r t he t e s t

s p e c im e n , a s y s t e m f o r h y d r o g e n c h a r g i n g o f t h e E B

w e l d t o i n d u c e c r a c k p r o p a g a t i o n u n d e r l o a d , a n d a

p l a s t i c s h i e l d t o p r o t e c t ope r a t i ng pe r s onne l f r om i n j u r y

c a us e d by pos s i b l e m i s s i l e s a nd s p l a s h i ng l i qu i d n i t r o -

ge n o r s u l f u r i c a c i d .

The t e s t p r oc e dur e de ve l ope d f o r t he s pe c i m e ns i n -

c l ude d t he fo l l ow i ng s t e ps : 1 ) i n s t r um e n t a t i on o f s pe d -

m e n ; 2 ) i n s e r t i on a nd a l i gnm e n t o f s pe c i m e n in the t e x t

f i x t u re ; 3 ) a t t a c h m e n t o f s e ns o r s t o r e c o r de r s a nd da t a

a c qu i s i t i on s ys t e m s ; 4 ) c oo l i ng o f t he s pe c i m e n t o t he

p r e s e l e c t e d t e st t e m pe r a t u r e d ; 5 ) l oa d i ng o f t he s pe c i -

m e n t o a t a r ge t l oa d , t yp i c a l l y c o r r e s p ond i ng t o i nc i p i-

e n t y i e l d i ng a t t he su r f a c e s o f the p l a t e ; 6 ) m a i n t e na n c e

o f t he l oa d w i t h t he t e s t i ng m a c h i ne i n d i s p l a c e m e n t

c o n t r o l ; 7 ) h y d r o g e n c h a r g i n g o f th e E B - w e l d f l aw ;

a n d 8 ) c o n t i n u o u s a n d / o r p e r i o d ic m o n i t o r in g o f

s pe c i m e n l oa d , s t r a i n , f l a w c r a c k - ope n i ng d i s p l a c e m e n t

C O D ) , a n d t e m pe r a t u r e un t i l e i the r f a i lu r e o f the s pe c i -

m e n o r p o p - i n a n d a r r es t o f t h e f la w o c c u r re d . I f p o p - i n

a n d a r r e s t o c c u r r e d , t h e s p e c i m e n w a s r e m o v e d f r o m

t h e m a c h i n e , h e a t - t i n t e d , a n d s u b s e q u e n t l y b r o k e n

f r a ng i b l y t o pe r m i t a v i e w o f t he a r r e s t e d f l a w p r o f i l e .

A dd i t i ona l de t a i l s on t e s t m a t e r i a l s , s pe c i m e ns a nd

pr oc e dur e s c a n be ob t a i ne d e l s e w he r e [ 2 ] .


16/23

186 w. R . Corw i n / R e ac t o r ue r se l c l add i ng s e para t e ~ fJ e ct s ~ 't udi es

4 . 5. T e s t re s u l ts a n d d i s c u s s i o n - P h a s e o n e

Efforts were made to use the test procedures de-

scribed above; however, departures occurred during the

experiments. A brief description of each test is given

below with the results.

One unclad plate, CP-1A, was tested. This test pro-

vided a demonstration of the hypothesis that at the

loading conditions chosen, an unclad specimen should

fail. The test procedure was carried out as pl anned, with

the fully instrumented specimen reaching and sustaining

a load of 622.8 kN at - 4 0 C, corresponding to incipi-

ent yielding of the surface fibers. Hydroge n charging

was initiated, and the specimen fractured frangibly into

two halves. The inst rume ntat ion of the plate, which is

typical for all other tests as well, is shown in fig. 19.

Foil-type strain gages, weldable COD gages, and tack-

welded thermocouples were included. On examination

of the fracture surface, the crack appeared to have

initiated in the brittle EB weld and rapidly propagated

through the entire plate.

Four plates with 308/309 cladding CP-3, CP-5,

CP-8, and CP-9) were tested. These tests were intended

to demonstrate and define the contri butio n that the

stainless steel cladding would make to the composite

structural resistance of the specimen to dynamic failure.

Specimen CP-3 was cooled to -4 0 C, and loading

toward the target incipient yielding load of 594.2 kN

was begun. At a load of 327.8 kN, a pop-in occurred.

Although calculations from the COD gage results indi-

cated a pop-in from a flaw of EB-weld size, the extent

of the event was uncertain, and loading was continued

to the target load. The specimen than was hydrogen-

charged for about 35 h, at which point it was concluded

that no further events would occur. The specimen was

unloaded and heat-tinted. The cladding on the specimen

was then sawed across the specimen) coplanar with the

pop-in down to the bottom of the groove surrounding

the EB weld to facilitate final fracture of the specimen.

The specimen was cooled to about -1 00 C and re-

loaded monoton ically until failure occurred at 364.6

kN.

The pop-in at 327.8 kN fig. 20) appears to have

propagated through the entire EB weld and into the

base metal in the depth direction, but not along the

surface of the cladding where it seems to have been

pinned at the intersection of the EB weld and cladding.

Upon final fracture, which was frangible, the crack did

Fig. 19. Unclad plate CP-1A shown after all instrumentation has been applied.


17/23


Fig. 20. Detail of pop-in area of types 309/308 stainless s teel c lad plate CP-3. Note that crack ran through the EB weld dark smooth

area) into the base metal dark rough area) in the depth direction but n ot along the surface where it was pinned by cladding.

r u n t h r o u g h b o t h t h e f e r r i ti c b a s e m e t a l a n d t h e r e m a i n -

i n g a u s t e n i t i c c l a d d i n g .

S p e c i m e n C P -5 w a s c o o l e d to - 4 0 C a n d l o a d e d t o

i n c i p i e n t y i e l d i n g a t t he b a s e - p l a t e / w e l d - m e t a l i n t e r -

f a c e ) a t 66 7 .2 k N , a n d h y d r o g e n c h a r g i n g w a s b e g u n .

T h e s p e c i m e n f a i l e d f r a n g i b l y i n a b o u t 3 h . T h e f r a c t u r e

s u r f a c e e x h i b i t e d f l a t f r a c t u r e , w h i c h a p p e a r s t o h a v e

o r i g i n a t e d i n t h e E B w e l d a n d r u n t h r o u g h o u t t h e p l a te .

S p e c i m e n C P - 8 w a s c o o le d to - 4 0 C a n d , si m i l a r t o

C P - 3 , p o p - i n o c c u r r e d d u r i n g l o a d i n g a t 29 1 k N . T h e

s p e c i m e n w a s u n l o a d e d , h e a t - t i n t e d , a n d l o a d e d m o n o -

t o n i c a l l y a t - 7 3 C u n t i l f ai l u r e o c c u r r e d a t 3 8 0 k N .

T h e c l a d d i n g w a s n o t s a w e d t o f a c i l i t a t e f r a c t u r e i n t h i s

s p e c i m e n . T h e f l a w h a d p r o p a g a t e d i n t o t h e b a s e m e t a l

d u r i n g t h e t e s t b u t r e m a i n e d p i n n e d a t t h e

c l a d d i n g / E B - w e l d i n te r fa c e .

T o d e f i n e t h e u p p e r l i m i t o f ar r e s t , a l o a d o f 4 1 8 k N

w a s c h o s e n a s t h e t e s t l o a d f o r s p e c i m e n C P - 9 , i n t e r -

m e d i a t e b e t w e e n s p e c i m e n s C P - 5 a n d C P - 8 . P o s t t e s t

m e a s u r e m e n t s o f t h e f l a w g e o m e t r y r e v e a l e d i t t o b e

c o n s i d e r a b l y d i f f e r e n t f r o m t h a t a s s u m e d i n t h e p r e t e s t

c a l c u l a t i o n s s o t h a t t h e a c t u a l s t r e s s i n t e n s i t y f a c t o r a t

a r r e s t w a s c o n s i d e r a b l y lo w e r t h a n e x p e c t e d . S p e c i m e n

C P - 9 w a s c o o l e d t o - 4 0 C , l o a d e d t o 4 18 k N , a n d

h y d r o g e n c h a r g e d . T h e f l a w p o p p e d i n a n d a r r e s t e d .

T h e s p e o m e n w a s u n l o a d e d , h e a t - t i n t e d , a n d l o a d e d

m o n o t o n i c a l l y at - 7 3 C u n t i l f a i l u r e o c c u r r e d a t 3 93 .7

k N . A t t h e p o p - i n , t h e f l a w t u n n e l e d w i t h i n t h e b a s e

m e t a l w i t h o u t c o n t a c t i n g t h e c l a d d i n g . T w o m e t h o d s

w e r e i n i t i a l l y u s e d t o c a l c u l a t e t h e s t r e ss i n t e n s i t y f a c t o r

a t a r r e s t as a f u n c t i o n o f a n g u l a r p o s i t i o n t a b l e 5 ): t h e

m e t h o d d e v e l o p e d b y M e r k l e [ 12 ,1 3] a n d t h e m e t h o d

d e v e l o p e d b y N e w m a n a n d R a j u [ 14 ]. L a t e r t h r e e - d i-

m e n s i o n a l f i n i t e - e l e m e n t c a l c u l a t i o n s w e r e a l s o m a d e

u s i n g th e O R V I R T p r o g r a m [ 15 ] t a b l e 5 ). N o a t t e m p t

w a s m a d e t o e s t i m a t e a n d t h e i n c o r p o r a t e b i - m e t a l l i c

a n d r e s id u a l s t r e s s e s in th e c a l c u la t io n s o r t o a s s e s s th e

e f f e c t o f p l a s t i c f l o w a t t e s t l o a d i n g . A s i n i t i a l l y p l a n n e d ,

t e s t l o a d i n g t o o b t a i n s t r e s s e s a p p r o a c h i n g y i e l d a t t h e

s t a i n l e s s b a s e - m e t a l i n t e r f a c e w o u l d r e s u l t i n p l a s t i c

f l o w o f t h e s t a i n l e s s c l a d d i n g . T h e s t r a i n r e p o r t e d i n

t a b le 5 i s t h e a v e ra g e s t r a in o n th e s t a in l e s s c l a d s u r fa c e

w i t h i n t h e c o n s t a n t m o m e n t z o n e o f t h e f o u r - p o i n t

b e a m l o a d i n g o f t h e s pe c i m e n s . F o r t h e c o n d i t i o n s o f

t h e e x p e r i m e n t s p e r f o r m e d w i t h y i e l d i n g o f t h e c l a d -

d i n g , i t w a s a s s u m e d t h a t f o r a f i r s t a p p r o x i m a t i o n , t h e


18/23

188 14/.R . ( orwm / Reac to r vesse l c ladding separa te ~]fec t~s s tudies

Table 5

Tabulation of calculated stress-intensity factor data

Speci- Flaw ~ Flaw Flaw Plate

men type depth half- depth

No. a length 0 = ~r/2

(cm) b plane w

(cm) (cm)

Load b Stress ~ Straind Tempera- Stress intensity factor,

K~(O)

(kN) (MPa) micro- ture 'j (MPaf m-)

strain ( C)

Method 0= 0 0=~r/6 0=~r/4 0=~r/3 0=~r/2

CP-1A I 1.43 3.35 5.40 622.8 48 1. 0 205 0 - 40 M 72.8 75.9 78.0 78.8 6g.0

RN 67. 8 67.5 67.0 65.8 66.4

CP-3 I 1.57 4.76 4.9 6 327.8 24 6. 6 1413 - 40 M 40.5 42.8 44.5 45.7 34.2

RN 36.9 36.9 36.7 36.4 35.6

CP-3 A 2.18 4 . 7 6 4.9 6 327.8 246 .6 1413 - 40 M 37.5 42.1 45.5 48.3 47.6

RN 30. 2 30.7 31.4 32.9 45.3

O 33.7 36.8 39.1 42.3 34.9

CP-5 I 1.51 2.12 4.81 667.2 478 .9 4473 - 40 M 51.5 55.9 59.6 63.6 77.8

RN 49.2 50.5 52.5 56.1 73.3

O 51.1 40.4 51.0 63.0 32.2

CP-7 I 1.15 3 . 3 3 4.86 413.7 31 8. 2 1353 -- 62 M 46.6 48.2 49.5 50.0 37.3

RN 43. 8 43. 6 43.2 42.3 37.5

CP-8 I 1.14 3. 26 4.89 291.4 23 3. 1 1360 - 40 M 33.9 35.1 36.0 36.4 27.5

CP-8 A 1.47 3 .0 1 4.89 291.4 23 3. 1 1360 40 M 33.7 34.0 35.3 36.1 34.9

O 30.7 31.6 32.4 33.7 21.3

CP-8 IR 1.47 3 .0 1 4.89 380.3 30 4. 2 164 0 73 M 44.0 44.3 46.1 47.2 45.5

CP-9 A 1.95 5.03 4.01 418.1 15 9. 7 1690 - 40 M 15.9 19.3 22.3 25.0 26.0

CP-9 f A 3.06 5.03 5.12 418.1 35 9. 2 1690 -4 0 M 36.3 55.3 62.7 63.0 103.7

CP-9 A 1.95 5.03 4.01 418.1 15 9. 7 1690 - 40 O 30.7 32.4 33.7 36.6 30.3

a I = initiation, A = arrested, and IR = initiated on reloading.

b Measured.

c Calculated at flaw 0 = ~r/2 plane.

d Measured average surface.

c M = Merkle method, RN = Raju-Newman method, and O = ORV1RT method.

f Calculat ion based on gross section.

stress intensity factor could be evaluated by assuming

the deformation of the entire beam was governed by the

elastic behavior of the bas e material.

The initial interpretation of the flaw arrest experi-

enced at the stainless base-metal interface for specimens

CP-3 and CP-8 was that the arrest was a result of the

stainless cladding. However, arrest within the base metal

for specimen CP-9 raised the question of the validity of

the approximate analyses used in light of the actual

specimen geometry prompting the additional ORVIR T

stress intensity factor calculations given in table 5, the

results of which are shown with the simpler method as

functions of the polar angle in fig. 21 for specimen

CP-3, as an example.

It is evident that the fabrication techniques em-

ployed were inadequate. The intent was to machine a

groove precisely down to the interface between the

stainless steel cladding and base metal and apply the

EB weld in the bot tom of the grooves in the base metal.

The grooves for CP-3, CP-5, and CP-8 were machined

too shallow. The groove for CP-9 was controlled in

depth by an etching technique, and while all traces of

the cladding layer were removed, the result was a deep

groove appreciably lower than the mean depth of the

weld interface.


19/23


7 0

6 O

v

z

n 3O

/ }

U J

n-

I -

~

. : _ 2 0

v

1 0

I I I I I I

I 1 - 1 1

~ ~ A ~ & ~

M E R K L E M E T H O D

R A J U - N E W M A N M E T H O D

I I O R V I R T

I I I I I I I

0 1 0 2 0 3 0 4 0 5 0 5 0 7 0 8 0 9 0 1 0 0

P O L A R A N G L E , (d og )

I

Fig. 21. Stress intensity for arrested flaw in specimen CP-3 as function of polar angle as calculated by Merkle, Raju-Newman, and

ORVIRT methods.

The simplified methods of analysis employed as-

sumed a plane surface at the bottom of the groove for

the calculation of the stress intensity factor because the

calculations were based on the intersection of a flaw

with a free surface; that is, the effect of the groove in

the cladding was ignored. In addition, the flaw was

assumed to have a semielliptical shape. On the other

hand, the ORVIRT calculations used the posttest-de-

termined shape of the groove and flaw to calculate the

stress inten sity factor. The resulting improved stress-in-

tensity factor calculation agreed reasonably well with

the simpler methods for specimens CP-3, CP-5, and

CP-8 which contained a shallow groove except for the

zone where the polar angle approache d 90 , near the

intersec tion of the flaw with the botto m of the groove in

the cladding. Here the stress intensity factors were

elevated, presumably due to the stress concentration

effects of the 6.25-mm-wide groove. For s pecimen CP-9,

which contained the deep groove and for which the

simplified methods were inadequate, only the ORVIRT

calculation appeared useful.

To see what effect the cladding had on the crack-ar-

rest properties of the composite clad-plate specimens, it

is useful to compare the maximum values of stress

intens ity factor calculated for the plate specimens at the

arrest of the pop-ins with values for the base metal. For

this purpose it was judged most reasonable to use the

peak values of Kt taken from the ORVIRT calculations

which are listed in table 6. This is because the peak

values reflect the stress conce ntrati on effects of the

Table 6

Maximum near-surface stress intensity factor values calculated

by ORVIRT for plates with 308/309 cladding

Plate Condition Angle K 1

deg) MPa~fm)

CP-3 Arrest 85 67

C P - 5 Initiation 90 101

CP-8 Arrest 80-85 50

CP-9 Arrest 89 57


20/23

190 ~ R. ( or w m / Reac tor t~e.ssel c ladding separa te tJ~bc ts ,s tudies

groove, which appear to be significant near the clad-

din g-b ase metal interface although not elsewhere. The

reason for using the peak values rather than those at

0 = ~r/2 was tha t the steeply falling segments of the

ORV IRT curves between the peaks and 0 = ~r/2 are not

considered accurate, because of finit e-element distortio n

effects which appear to have developed very near the

ends of the flaws. The results for the crack arrest

specimens and the clad-plate specimens shown in fig. 22

indicate that two of the values of arrest toughness

calculated for the clad-plate experiments CP-8 and -9)

coincide closely with those obtained using crack-arrest

specimens ; the third CP-3), however, is slightly higher.

The stress inten sity factor for clad-plate specimen CP-5,

which did not arrest, was calculated for the flaw geome-

try and loading conditions at initiation and, because of

the load reached, was well in excess of the values

obtained with the crack arrest specimens. Overall the

comparisons made between the crack-arrest specimens

and the clad-plate experiments show that there may be

limited ability of the moderate toughness cladding ex-

amined to enhance structural resistance to crack exten-

sion. However, the present da ta are not entirely conclu-

sive because only a modest increase, if any, in the

calculated arrest toughness of the clad-plate specimens

beyon d the base material scatter band was observed.

To provide a more definitive answer regarding if and

indeed how much structural enhancement the cladding

could yield in this geometry would require additional

testing. Initial loading conditions need to be reached

that would produce a level of stress inten sity factor in

the dynamic ally moving flaw in between those obta ined

in CP-3, -8, and -9 which arrested more or less within

the scatter band for the base plate), and that obtained

in CP-5 which did not arrest at all). However, such

tests were not performed in this series of experiments. It

was not possible to reach a level of load that was high

enough to produce the required initial conditions as a

result of premature pop-ins during loading, such as

occurred in CP-3 and CP-8. This was caused by not

removing all the stainless steel weld metal prior to EB

welding. Mixing of the stainless steel with the low alloy

2

1 8 0

1 6 0

140

or 120

I.-

100

>-

F--

Z

Id J

I---

7

0 3

0 3

t .~

ee-

l---

8

6

4

2

- 5 0 - 4 0

I I I I I I I I 1 I I

P L A T E H S ST 0 7 O V A L I D 1 T C A S P E C I M E N

L T O R I E N T A T I O N I N V A L I D 1 T C A S P EC I M EN

N D T = - 1 8 o c 0 O F) B E A M S P E C I M E N

T / 6 8 J = 2 0 o c 6 8 F ) F L A W A R R ES T E D

R T N D T = _ 1 3 o c 8 OF )

B E A M S P E C I M E N

F L A W D I D N O T A R R E S T

c e - 5 ~

C P - 3 O

c _ o

C P - 8 , ~

C L A D B E A M

T E S T T E M P E R A T U R E , R E L A T I V E T O R T N D T O F B AS E M E T A L

t z J i J J J

- 3 0 - 2 0 - 1 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

T - R T N D T o c )

Fig. 22. Comparing the crack-arrest values calculated for clad-plate specimens that arrested with those obtained from crack-arrest

specimens indicates only a possibility that the cladding enhanced the toughness of the structure.


21/23

W.R. Corwin / Reactor vesse l c ladding separate e f fec ts s tudies 191

ba s e p l a t e r e s u l t e d i n c r a c ks w i t h i n t he w e l d nugge t ,

w h i c h i n i t i a t e d t he l ow l oa d pop - i n s . Spe c i m e n C P- 5 ,

w h i c h d i d r e a c h t he t a r ge t l oa d o f i nc i p i e n t s u r f a c e

y i e l d i n g a n d d e m o n s t r a t e d t h a t r a p i d f r a c t u r e i n t h e

p r e s e n c e o f m o d e r a t e l y t o u g h c l a d d i n g c o u l d o c c u r ,

p r o d u c e d a v a l u a b l e u p p e r l i m i t a t w h i c h a r re s t d i d n o t

h a p p e n .

R e m ov i ng a l l t r a c e s o f t he c l a dd i ng p r i o r t o EB

w e l d i ng , a s i n s pe c i m e n C P- 9 , s o l ve d t he p r ob l e m o f

p r e m a t u r e pop - i n s . H ow e ve r , t he r e s u l t i ng de e p g r oove

g e o m e t r y in t r o d u c e d s u f fi c ie n t e x p e ri m e n t a l a n d a n a -

l y r i c a l a m b i gu i t i e s t ha t no i m pr ove m e n t i n de f i n i ng t he

s t r uc t u r a l e f f e c t o f t he c l a dd i ng on c om pos i t e c r a c k - a r -

r e s t p r ope r t i e s o f t he c l a d - p l a t e s pe c i m e ns w a s ob -

ta ined.

f l a w o n t h e s u r f a c e a n d k e e p a s h o r t f l a w f r o m b e c o m -

i ng l ong . O ne s pe c i m e n a r r e s t e d a t a c a l c u l a t e d s t r e s s

i n t e ns i t y f a c t o r i n e xc e s s o f t he obs e r ve d s c a t t e r ba nd

f o r c r a c k a r r e s t da t a w i t h i n t he ba s e p l a t e ; m or e ove r ,

none o f t he f l a w s t ha t a r r e s t e d s hou l d ha ve done s o i n

t he e x i s t i ng s t r e s s f i e l d un l e s s t he r e ha d be e n s om e

d e g r e e o f p i n n i n g o f t h e e n d s o f t h e f l a w b y a t o u g h

s u r f a c e l a ye r . I t i s i m por t a n t t o s t r e s s , how e ve r , t ha n

a n y s t r u c t u r a l t o u g h n e s s e n h a n c e m e n t b y t h e c l a d d i n g

i n t h i s s t udy w a s l i m i t e d . The f a c t t ha t p l a t e C P- 5

f r a c t u r e d c om pl e t e l y w i t h no i nd i c a t i on o f c l a dd i ng - i n -

duc e d a r r e s t i s a c l e a r de m ons t r a t i on o f t he m ode r a t e l y

t oug h c l a dd i ng s l i m i ta t i on .

4 . 7 . P l a n s f o r c l a d p l a t e e x p e r i m e n t s P h a s e tw o

4 .6 . C o n c l u s i o n s P h a s e o n e

B y c o m p a r i n g t h e b e h a v i o r o f t y p e s 3 0 8 / 3 0 9 s t a i n -

l e s s s t e e l c l a d p l a t e s C P- 3 , C P- 5 , C P- 8 , a nd C P- 9 w i t h

t ha t o f t he unc l a d p l a t e a nd t he ba s e p l a t e c r a c k - a r r e s t

da t a , i t a ppe a r s t ha t m ode r a t e l y l ow - t oughne s s s t a i n l e s s

s t e e l c l a dd i ng ha s a l i m i t e d c a pa c i t y t o a r r e s t a r unn i ng

Pha s e t w o o f t he c l a d p l a t e e xpe r i m e n t s w i l l be t t e r

de f i ne t he s t r uc t u r a l e f f e c ts o f c l a dd i ng , u s i ng bo t h

e n h a n c e d e x p e r im e n t a l t e c h n i q u e a n d h i g h q u a l i ty c o m -

m e r c i a l l y p r oduc e d c l a d ove r l a y w e l dm e n t .

To e l i m i na t e t he c om pl i c a t i ons o f t he g r oove - i n -

duc e d s t r e s s c onc e n t r a t i on a nd o f ha v i ng t he f l a w i n a

p r e v i ous l y w e l de d r e g i on , a ne w s pe c i m e n d e s i gn ( fi g.

P 2

P 2

P 2

I M E N S I O N S I N

CENTIMETERS

Fig. 23. Specim en dimension s and load locations of optimized specim en to be used in phase two of clad plate investigations.


22/23

92

W.R. Corwin / Reactor vessel cladding separate fjbcts studies

2 3 ) h a s b e e n u s e d to c o n t in u e th i s w o rk in th e n e x t

s e r i e s o f e x p e r ime n t s . In th i s s p e c ime n , p r io r t o w e ld -

in g , t h e b a s e me ta l w a s r e c e s s e d to a d e p th e q u a l t o th a t

o f t h e c l a d d i n g o n b o t h s i d e s o f t h e m i d d l e r e g i on .

T h e s e r e c e s s e d r e g io n s w e re th e n f i l l e d in w i th w e ld

c la d d in g . T h i s d e s ig n p ro v id e s a f l a t s u r fa c e , f r e e f ro m

d is c o n t in u i t i e s , o th e r t h a n th e f l a w i t s e l f , fo r a n a ly t i c a l

s i m p l i f i c i t y a n d w i l l a ls o p r o v i d e a n a r e a n o t c o n -

t a m i n a t e d w i t h s t a i n l e s s s t e e l w e l d m e t a l i n w h i c h t h e

E B w e l d c a n b e p l a c e d . T h i s s h o u l d a l l o w t he s p e c i m e n

t o r e a c h w h a t e v e r i n i t i a l l o a d i n g c o n d i t i o n s a r e d e s i r e d

to a c c u ra t e ly a s s e s s th e e f f e c ts o f t h e c l a d d in g .

T h e w e l d m e n t s f r o m w h i c h t h e s e s p e c i m e n s h a v e

b e e n f a b r i c a t e d w e r e c o m m e r c i a l l y p r o d u c e d u s i n g t h e

s a m e t h r e e w i r e s e r i e s a r c p r o c e d u r e s e m p l o y e d f o r t h e

s e c o n d p h a s e o f t h e c l a d d i n g i r r a d i a t i o n e x p e r i m e n t s .

O n l y o n e l a y e r o f c l a d d i n g w a s n e c e s s a r y t o m e e t t h e

th i c k n e s s r e q u i re me n t s fo r t h e t e s t p l a t e s , w h e re a s th re e

l a y e r s w e r e a p p l i e d t o p r o d u c e a n a d e q u a t e t h i c k n e s s

f o r t h e c o m p a n i o n c h a r a c t e r i z a t i o n s p e c i m e n s . H o w -

e v e r , d e m a n d i n g c o n t r o l s o n t h e f i n i s h e d w e l d m e n t

i n c l u d i n g s u b s i ze i m p a c t s p e c i m e n t e s t i n g a n d c h e m i c a l

a n d m e t a l l o g r a p h i c a n a l y s i s o f e a c h l a y e r h a s a s s u r e d

u n i f o r m i t y a m o n g l a y e r s o f c l a d d i n g . S p e c i a l i ze d h e at

t r e a t m e n t o f t h e A 5 3 3 g r a d e B c h e m i s t r y b a s e p l a t e

u s e d in f a b r i c a t in g th e p l a t e s w a s u s e d to g re a t ly e l e v a te

i t s d u c t i l e - t o - b r i t t l e tr a n s i t i o n t e m p e r a t u r e . T h e r e s u lt -

i n g s p e c i m e n s , c o m p o s e d o f a h i g h l y u n i f o r m c l a d d i n g ,

ty p ic a l o f o ld e r r e a c to r p re s s u re v e s s e l s , d e p o s i t e d o n a

h i g h t r a n s i t i o n b a s e p l a t e , w i l l a l l o w t h e s t r u c t u r a l

e v a l u a t i o n o f a n a r b i t r a r i l y t o u g h c l a d d i n g . S e l e c ti o n o f

a t e st t e m p e r a t u r e b e t w e e n - 2 5 a n d 2 5 C w i l l r e s u l t

i n a c l a d d i n g w i t h c h a r p y i m p a c t e n e r g y v a r y i n g f r o m

a b o u t 4 0 to 7 0 J , w h i l e ma in ta in in g a f r a n g ib le b a s e

p la te f ig . 24).

I n a d d i t i o n t o e x a m i n i n g t h e e f f e c t s o f c l a d d i n g o n

c ra c k a r r e s t i n th e c o mp o s i t e s t ru c tu re , i n i t i a t io n e f f e c t s

w i l l a l s o b e e x a m i n e d . F o l l o w i n g p o p - i n a n d a r r e s t i n

th e s e s p e c ime n s , t h e y w i l l b e h e a t t i n t e d to ma rk th e

i n i t i a l f r a ct u r e s u r f a c e a n d t h e n m o n o t o n i c a l l y l o a d e d

to f a i lu re a t a p re s e l e c t e d t e mp e ra tu re .

A l l t e s t m a t e r i a l s a n d s p e c i m e n s a r e c u r r e n t l y o n

h a n d a n d m a t e r i a l s c h a r a c t e r i z a t i o n t e s t i n g i s u n d e r -

w a y . P la t e t e s t in g i s e x p e c te d to b e c o mp le te d in 1 9 8 6 .

2 0 0

1 7 5

1 5 0

1 2 5

100

z

w

75

5 0

2 5

I I I

- - - - O - - - - 3 - W I R E S E R I E S - A R C C L A D D I N G

r l A 5 3 3 G R A D E B B A S E P L A T E

O

O J

[ I

O

B A S E P L A T E

N D T

0 i i i J i i i ~ i I . , .

- 1 0 0 0 1 0 0 2 0 0 3 0 0


Fig. 24. A clad plate test temperature can be selected for phase two which will yield a brittle base plate and an arb itrarily tough

cladding.


23/23

W.R. Cor win / Reactor vessel cladding separate effects studies 193

5. Summary

In the two-pronged effort on the potential effects of

cladding relating to the integrity of an RPV during an

over cooling transient, encouraging results were pro-

duced. Good quality weld overlay cladding generally

maintained its inherent toughness following irradiation

exposure and cladding of even only moderate toughness

appeared to slightly enhance the integri ty of a struct ural

member. Additional irradiation and structural data on a

commercial weld overlay being generated in phase two

of these experiments will add greatly to the existing

unde rsta ndin g of cladding effects. On the cau tionar y

side, it is clear that poor quality cladding can exhibit

marked radiation induced embrittlement. Moreover,

there are clearly loading conditions which negate the

limited structural benefit weld overlay can add to a

structure.

Acknowledgments

The author gratefully acknowledges G.C. Robinson,

R.G. Berggren, and R.K. Nanstad for assistance in

designing and executing the experiments; W.J. Stelz-

man, G.M. Goodwin, J.W. Hendrix, and J.D. Hudson

for development of welding and heat-treating proce-

dures and production of the test materials; R.J. Gray

and C.P. Haltom for metallographic studies; J.G.

Merkle, R.H. Bryan and B.R. Bass for fracture-mecha-

nics analysis; P.P. Holz for electron beam welding;

W.F. Jackson and R. Smith for instrume ntati on; R.L.

Swain and T.D. Owings for experimental assistance;

a n d D L .

Northern for revising and preparing the

manuscript. Lastly, the author wishes to acknowledge

M. Vagins and the U.S. Nuclear Regulatory Commis-

sion for the technical and financial backing which made

this work possible.

References

[1] W.R. Corwin, R.G. Berggren, and R.K. Nanstad, Charpy

toughness and tensile properties of a neutron-irradiated

stainless steel submerged arc weld cladding overlay,

NUREG/CR-3927, ORNL/TM-9309, Martin Marietta

Energy Systems, Inc., Oak Ridge National Laboratory

September 1984).

[2] W.R. Corwin et al. , Effect of stainless steel weld overlay

cladding on the structural integrity of flawed steel plates

in bending, Series 1, NUREG/CR-4015,

O R N L / T M

9390, Martin Marietta Energy Systems, Inc., Oak Ridge

National Laboratory April 1985).

[3] A. Schaeffler, A constitution diagram for stainless steel

weld metal, Met. Prog. 56 5) 1949) 680-6g0B.

[4] R.J . Gray, Magnetic etching with ferrofluid, in: Metallo-

graphic Specimen Preparation, pp. 155-77, ed. J .L. Mc-

Call and W.M. Mueller Plenum, New York, 1974).

[5] E.B. Norris, D.R. Ireland, and C.E Lautzenheiser, The

second inspection of the Elk River reactor pressure vessel

after operation, SWRI 1228 P9-13, Southwest Research

Institute, San Antonio, Tex. July 21, 1967).

[6] T. Kondo, H. Nakajima, and R. Nagasaki, Metallographic

investigation on the cladding failure in the pressure vessel

of a BWR, Nucl. Engrg. Des. 16 1971) 205-222.

[7] D.T. Read et al., Metallurgical factors affecting the tough-

ness of 316L SMA weldments at cryogenic temperatures,

Weld J. 59 4) April 1980) 104-113-s.

[8] F.W. Bennett and C .P . Dillon, Impact strength of

austenitic stainless steel welds at -32 0 F - Effects of

composition, ferrite content, and heat treatment, J. Basic

Engrg. 88 March 1966) 33-36.

[9] G.M. Goodwin, Fracture toughness of austenitic stainless

steel weld metal at 4 K, ORNL/TM-9172, Martin Marietta

Energy Systems, Inc., Oak Ridge National Laboratory

August 1984).

[10] J.R. Hawthorne and H.E. Watson, Exploration of the

influence of welding variables on notch ductility of irradi-

ated austenitic stainless steel welds, Proc. Int. Conf. On

Radiation Effects in Breeder Reactor Structural Materials,

pp. 327-36, meeting held in Scottsdale, Ariz., June 1977.

[11] W.R. Corwin, Assessment of radiation effects relating to

reactor pressure vessel cladding, NUREG/CR-3671

ORNL-6047), Martin Marietta Energy Systems, Inc., Oak

Ridge National Laboratory July 1984).

[12] J.G. Merkle, Stress-intensity factor estimates for part-

through surface cracks in plates under combined tension

and bending, pp. 3-22 in: Quarterly Progress Report on

Reactor Safety Programs Sponsored by the Division of

Reactor Safety Research for July-September 1974,

ORNL/TM-4729, Vol. If, Union Carbide Corporation,

Nuclear Division, Oak Ridge National Laboratory.

[13] R.D. Cheverton et al ., Applicability of LEFM to the

analysis of PWR vessels under LOCA-ECC thermal shock

conditions, NUREG/CR-0107 ORNL/NUREG-40),

Union Carbide Corporation, Nuclear Division, Oak Ridge

National Laboratory October 1978).

[14] J.C. Newman, Jr., and I.S. Raju, Analyses of surface

cracks in finite plates under tension or bending loads,

NASA Technical Paper 1578 1979).

[15] B.R. Bass and J.W. Bryson, ORVIRT: a finite element

program for energy release rate calculations for 2-dimen-

sional and 3-dimensional crack models, NUREG/CR -

2997, Vol. 2 ORNL/TM-8527/V2), Union Carbide Cor-

poration, Nuclear Division, Oak Ridge National Labora-

tory February 1983).

Reactor Vessel Cladding

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