7/26/2019 Reactor Vessel Cladding
1/23
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 )
7/26/2019 Reactor Vessel Cladding
2/23
172
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.
7/26/2019 Reactor Vessel Cladding
3/23
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.
7/26/2019 Reactor Vessel Cladding
4/23
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.
7/26/2019 Reactor Vessel Cladding
5/23
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 .
7/26/2019 Reactor Vessel Cladding
6/23
1 7 6
V~R Cor wm / Reac tor resse l c ladding separate
7/26/2019 Reactor Vessel Cladding
7/23
W R Corwin / Reactor vessel cladding separate effects studies 177
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.
7/26/2019 Reactor Vessel Cladding
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 .
7/26/2019 Reactor Vessel Cladding
9/23
W R Corwin / Reactor vessel cladding separate effects studies 179
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 .
7/26/2019 Reactor Vessel Cladding
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
7/26/2019 Reactor Vessel Cladding
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 -
7/26/2019 Reactor Vessel Cladding
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.
7/26/2019 Reactor Vessel Cladding
13/23
W R Corwin / Reactor vessel cladding separate effects studies 183
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.
7/26/2019 Reactor Vessel Cladding
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
T E M P E R A T U R E ( C )
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 .
7/26/2019 Reactor Vessel Cladding
15/23
W R Corwin / Reactor vessel cladding separate effects studies 8
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 ] .
7/26/2019 Reactor Vessel Cladding
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.
7/26/2019 Reactor Vessel Cladding
17/23
W R Corwin / Reactor vessel cladding separate effects studies 187
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
7/26/2019 Reactor Vessel Cladding
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.
7/26/2019 Reactor Vessel Cladding
19/23
W R Corwin / Reactor vessel cladding separate effects studies 189
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
7/26/2019 Reactor Vessel Cladding
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.
7/26/2019 Reactor Vessel Cladding
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.
7/26/2019 Reactor Vessel Cladding
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
T E M P E R A T U R E ( C )
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.
7/26/2019 Reactor Vessel 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).
Top Related