Ternary fission of neutron induced uranium fissioning isomers

Abstract Spontaneously fissioning isomers (SFI) of uranium were produced in 236, 238 U(n,n') reactions at 4.5 MeV mean neutron energy. A pulsed beam electrostatic accelerator was used and a time analysis of fission events was applied. Fission fragments were detected by a scintillation method, and long-range fission particles were detected by an ionization technique. Relative fission probabilities through the SFI state for both the nuclei were determined as (1.30 ±.01).10 −4 in 236 U and (1.48 ± 02) . 10 −4 in 238 U case. The SFI half-lives were determined as 121 ± 2 ns and 267 ± 13 ns respectively. As a result of uranium SFI ternary fission study it was observed that one ternary per 163 ± 44 binary fissions of 236mfu and one ternary per 49 ± 14 binary fissions of 238mf U took place. These figures seem to be rather high as compared with nonisomeric ternary fission probability data, and tentative effect of a particular nucleon configuration in the uranium SFI is supposed.