Ranges and Kinetic Energies of Fragments from Fission ofU238Induced by 14.5-MeV Neutrons

Abstract

The average ranges of eight fission-product recoils in uranium, including both symmetric and asymmetric fragments, have been measured radiochemically from 14.5-MeV-neutron-induced fission of $^{238}\mathrm{U}$, using the thick-target technique. The measured average ranges, corrected for anisotropy, scattering, and edge effects, are, in mg/${\mathrm{cm}}^{2}$ U: $^{91}\mathrm{Sr}$: 10.21\ifmmode\pm\else\textpm\fi{}0.42, $^{99}\mathrm{Mo}$: 11.20\ifmmode\pm\else\textpm\fi{}0.29, $^{113}\mathrm{Ag}$: 9.63\ifmmode\pm\else\textpm\fi{}0.33, $^{115}\mathrm{Cd}$: 9.90\ifmmode\pm\else\textpm\fi{}0.97, $^{117}\mathrm{Cd}$: 9.36\ifmmode\pm\else\textpm\fi{}0.45, $^{121}\mathrm{Sn}$: 9.47\ifmmode\pm\else\textpm\fi{}0.87, $^{139}\mathrm{Ba}$: 7.60\ifmmode\pm\else\textpm\fi{}0.14, and $^{140}\mathrm{Ba}$: 8.14\ifmmode\pm\else\textpm\fi{}0.28. Using Niday's range-velocity relation, these ranges were converted to kinetic energies of the fragments to determine if there exists a deficit in total kinetic energy release at symmetric mass division. A dip was observed in the range-versus-mass curve, but the magnitude of this dip was smaller than what was previously reported in thermal-neutron fission of $^{235}\mathrm{U}$. The maximum total kinetic energy release at mass ratio 1.36 was found to be 176.7\ifmmode\pm\else\textpm\fi{}3.3 MeV, and the deficit in the energy release, corresponding to the observed dip in the range-mass curve, at symmetric fission was estimated to be 17\ifmmode\pm\else\textpm\fi{}5 MeV.