New Results on Helium and Tritium Gas Production From Ternary Fission

Ternary fission constitutes an important source of helium and tritium gas production in nuclear reactors and in used fuel elements. Data related to this production are therefore requested by nuclear industry. In the present paper, we report results from measurements of the ⁴He and ³H emission probabilities (denoted LRA/B and t/B, respectively). These measurements concern both thermal neutron‐induced fission reactions as well as spontaneous fission decays. For spontaneous fission, data are reported for nuclides ranging from ²³⁸Pu up to ²⁵²Cf. For thermal neutron‐induced fission, results cover target nuclei between ²²⁹Th and ²⁵¹Cf. Based on these and other results, semi‐empirical relations are proposed. These correlations are only valid if spontaneous fission data and neutron‐induced fission data are considered separately, which shows the impact of the fissioning nucleus‐excitation energy on the ternary particle‐emission process. In this way, t/B and LRA/B values could be evaluated for fissioning systems not investigated so far. These results could be used for the ternary fission‐yield evaluation of the JEFF3.1 library.