Delayed neutron precursors—I: Antimony and arsenic precursors separated by electrolysis

Abstract

Using an improved electrolytic separation technique, further studies are reported of delayed neutron emission from Sb and As fission product isotopes. Previous results have been confirmed and a difference in half-life between the two short-lived delayed neutron precursors has been established. Least-squares fits of the data gave the following half-lives: 135Sb 1·59 ± 0·09 sec; 85,86As 2·03 ± 0·03 sec. In the thermal neutron fission of 235U, the absolute delayed neutron yields of these nuclides (neutrons/10 4 fissions) are: 135Sb 3·6 ± 0·5, 85,86As 9·4 ± 1·3. The longlived delayed neutron precursor detected previously ( t 1 2 14 ± 4 sec) has been shown to be due to one of the elements Sb, As, Sn, Ge, Se or Te, and not to halogen contamination. It appears to consist of two components, one with a half-life of 9–12 sec and the other much longer lived.