Measurement of Fission and Capture Cross Sections for Design of Transmutation Systems

The fission cross section for 237NP from a b o u t 1 eV to about 5 keV r e l a t i v e t o t h a t for 235U was measured with back–to–back type double fission chambers using an elec– tron linear accelerator (linac) driven lead slowing–down neutron spectrometer (lead spectrometer) . Although the shape of the present energy dependent cross section agrees with those of JENDL–3 (below 120 eV) and ENDF/B–VI, their absolute values are from 3 to 4 times smaller than the present data. The thermal neut ron capture and resonance n e u t r o n c a p t u r e i n t e g r a l f o r ‘37Np were measured by the ac t iva t ion method in a s tandard thermal neut ron f ie ld and in a s t a n d a r d l / E n e u t r o n f i e l d , r e s p e c t i v e l y . T h e p r e s e n t r e s u l t f o r t h e f o r m e r , 154.7f 2.9 b , i s about 17% smal ler than those in JENDL–3 and ENDF/B–VI, but the preliminary d a t a f o r t h e l a t t e r , 6 4 6 b r e a s o n a b l y a g r e e s w i t h t h o s e i n b o t h f i l e s .