MlTEUE YEUQIIIAL IFlJrrnm m NORTHWEST rrcrnc norrrnrrvrsr u a o r u~o~v LEGAL N O T I C E Thh t~t l * pl-f.d 01 an =count of Government rponmmd w d . Nmft)m f i e United Stotnor t b Commisdon, mr ony pwron wing on bblt of the Cwnmiuion; A. Makes ony wutronty w reprmantoth, -pressed or implid, with respect tg the occuray, com. phtmads, or uwfutneu of ~h s Inhrmation tontoind in his rmpwit, w t k t ths u# of ony informah, ~p e o l o t~, method, or procns disclorad h hi6 report may no! infringe

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... wtely owned righh; or 8. Aswmes any labllitisr wfrh respect to h a uwz of. w for damapes tesulting h#n th. me of o y Inforimtion, oppormlus, method, or prora,~ dbcfosed in this rsport. As used In the a b e , 'psnwt acting QR behotf of tha Commission' i~l d n ony -p l o p ol rorHmclor of the Commisdon, or employ-d such contractor, to the e x m t r h d such r m p k p or con-traMr of ttra Cmmkion, w smployw of rush contractor preparm, dimLotes, or provtdssto, my information pursuant to his employment or contmct with the Cammitalon, or hh employment wlth MIdl controclw. PACIFIC NORTH WEST LABORATORY amUbrD, WACHLW~QN by UTrmE MEMORIAL I N S M forth. ABSTRACT Two t u b u l a r f u e l element w i t h i n t e g r a l t a r g e t l a t t i c e s have been i n v e s t i g a t e d i n t h e P h y s i c a l Constants Test Reactor (PCTR). M u l t i p l i c a t i o n c o n s t a n t s , neutron u t i l i z a t i o n r a t i o s , f a s t f i s s i o n f a c t o r s , and i n i t i a l conversion r a t i o s have been i n f e r r e d from n u l l r e a c t i v i t y experiments and measurements of s p a t i a l d i s t r i b u t i o n s of neutron r e a c t i o n r a t e s . Both wet and dry experiments were c a r r i e d o u t i n a three-by-three a r r a y of l a t t i c e c e l l s 37.5" long placed i n t h e c a v i t y of t h e PCTR. I n f e r r e d l a t t i c e c h a r a c t e r i s t i c s and measured s p a t i a l d i s t r i b u t i o n s a r e i n reasonably good agreement w i t h t r a n s p o r t c a l c u l a t i o n s performed w i t h Program S and THERMOS. This r e p o r t i n c l u d e s primary d e s c r i p t i o n s of t h e experiments and r e s u l t s , and some s i g n i f i c a n t comparisons w i t h theory.