Total kinetic energy release in the fast-neutron-induced fission of 237Np

The total kinetic energy (TKE) release in the fast neutron-induced fission of( 237)Np was measured for neutron energies from E-n = 2.6-100 MeV at the Los Alamos Neutron Science Center at the Weapons Neutron Research facility. The post-TKE release decreases nonlinearly with increasing incident neutron energy and can be represented as TKE (MeV) = (174.38 +/- 0.72)-(5.11 +/- 0.5821)log(10)E(n) for E-n > 1 MeV. Analysis of the fragment mass distributions indicates that the decrease in TKE with increasing E-n is a consequence of the fading out of shell effects at high excitation energies (resulting in an increase of symmetric fission) and the decrease of the total kinetic energy associated with asymmetric fission with increasing E-n.