Independent fission yields of Rb and Cs from thermal-neutron-induced fission ofPu239

Abstract

The relative independent fission yields of Rb and Cs from thermal-neutron-induced fission of $^{239}\mathrm{Pu}$ have been measured on line using a mass spectrograph and thermalized neutrons from a burst reactor. Independent yields were derived by normalizing the measurements to products of chain yields and fractional independent yields, estimating the latter from measured cumulative yields of Kr and Xe. Comparing the independent yields with those from $^{238}\mathrm{U}$ fission, the $^{239}\mathrm{Pu}$ results show shifts in isotopic yield distribution toward lower mass for both Rb and Cs and also toward the production of more Cs and less Rb when $^{239}\mathrm{Pu}$ is fissioned.NUCLEAR REACTIONS $^{209}\mathrm{Pu}(n, f)$, $E=\mathrm{thermal}$; measured relative abundances; deduced independent fission yields. Mass spectrograph, burst reactor.