Effect of hydrogen on the low-temperature deformation properties of neutron-irradiated vanadium
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h a s b e e n r e c e n t l y r e a l i z e d that the effect of h y d r o gen on n e u t r o n - i r r a d i a t e d Group Va m e t a l s is of t e c h n o l o g i c a l i m p o r t a n c e f r o m the v i e w p o i n t of m a t e r i a l s d e s i g n in n u c l e a r r e a c t o r a p p l i c a t i o n s . I The v a r i o u s h y d r o g e n i s o t o p e s in c u r r e n t and p r o j e c t e d r e a c t o r d e s i g n s m a y p r o v i d e s o u r c e s of h y d r o g e n and c r e a t e the p r o b l e m of l o w - t e m p e r a t u r e h y d r o g e n e m b r i t t l e m e n t if the r e a c t o r s r e q u i r e s h u t - d o w n a f t e r o p e r a t i n g . In s p i t e of the i m p o r t a n c e of h y d r o g e n p r o b l e m s in nuc l e a r m a t e r i a l s technology, no i n v e s t i g a t i o n s have b e e n u n d e r t a k e n to u n d e r s t a n d the h y d r o g e n effect on the d e f o r m a t i o n p r o c e s s of the n e u t r o n - i r r a d i a t e d Group Va m e t a l s . F u n d a m e n t a l i n v e s t i g a t i o n s of the i n t e r s t i t i a l i m p u r ity e f f e c t s on l o w - t e m p e r a t u r e s t r e n g t h of i r r a d i a t e d b c c m e t a l s h a v e been e x t e n s i v e l y u n d e r t a k e n in r e c e n t y e a r s , z-x6 but the q u e s t i o n s c o n c e r n i n g how the i m p u r ity i n t e r s t i t i a l s affect the n e u t r o n - p r o d u c e d d e f e c t s which c a u s e the i n c r e a s e in e f f e c t i v e s t r e s s (r*) s t i l l r e m a i n . At p r e s e n t two p o s s i b l e e x p l a n a t i o n s have b e e n p r o p o s e d . One i n t e r p r e t a t i o n is b a s e d on the a s s u m p t i o n that the i m p u r i t y i n t e r s t i t i a l s c a n c e l o r n e u t r a l i z e the n e u t r o n - p r o d u c e d d e f e c t s , i.e. a s c a v e n g i n g effect. The s e c o n d e x p l a n a t i o n is b a s e d on the a s s u m p tion that the i m p u r i t y i n t e r s t i t i a l s p r e v e n t the n e u t r o n produced vacancies or interstitials from moving tog e t h e r to f o r m the s h o r t - r a n g e b a r r i e r s to d i s l o c a t i o n motion, s'~'a However, a r e v i e w of the p r e v i o u s s t u d i e s i n d i c a t e s that a l l of the w o r k on the i n t e r s t i t i a l e f f e c t s have b e e n c a r r i e d out on the i n t e r s t i t i a l e l e m e n t s of c a r b o n , n i t r o g e n and oxygen. T h e r e is an e x p e r i m e n t a l d i f f i c u l t y in doping with t h e s e i n t e r s t i t i a l s , e s p e c i a l l y a f t e r the i r r a d i a t i o n , due to the f a c t t h a t the doping C, C. CHEN is associated with Wyman-Gordon Company, Worcester, MA. R. J. ARSENAULT is Professor of Engineering Materials, Engineering Materials Group, and Department of Chemical Engineering, University of Maryland, College Park, MD 20742. Manuscript submitted October 16, 1974. METALLURGICAL TRANSACTIONS A
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