Delayed-neutron yields in the fission of Pu239 and Th232 by 14.5 Mev energy neutrons

Delayed Neutron Yields from 14.8 MeV Neutron Induced Fission of 238U, 232Th and 231Pa

“…In the energy ränge thus defined it is vddely accepted that delayed neutron yields are substantiaUy independent of neutron bombarding energies [1,3]. However, experimental work reported [10][11][12][13][14] before 1965 indicated that neutron yields (not all measured absolutely) were higher (by a factor of about 2) from fission induced by 14 to 15 MeV neutrons than corresponding yields from the lower energy (^ 4 MeV) bombardments [3]. Such observations were contrary to the prediction made by KEEPIN [5,9] who asserted that the change in charge distribution in isobaric fission fragments with increasing excitation energy of the fissioning nucleus should lead to a reduetion rather BROWN, LYLE and MABTIN, 14.8 MeV Neutron Induced Fission of "»U, and "iPa Radiochimica Acta than an increase in delayed neutron ylelds.…”