Exploratory study of fission product yields of neutron-induced fission ofU235, U238, andPu239at 8.9 MeV

Abstract

Using dual-fission chambers each loaded with a thick $(200--400\ensuremath{-}\mathrm{mg}/\mathrm{c}{\mathrm{m}}^{2})$ actinide target of ${}^{235,238}\mathrm{U}$ or $^{239}\mathrm{Pu}$ and two thin $(\ensuremath{\sim}10--100\ensuremath{-}\ensuremath{\mu}\mathrm{g}/\mathrm{c}{\mathrm{m}}^{2})$ reference foils of the same actinide, the cumulative yields of fission products ranging from $^{92}\mathrm{Sr}$ to $^{147}\mathrm{Nd}$ have been measured at ${E}_{n}=8.9\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. The $^{2}\mathrm{H}(d,n)\phantom{\rule{0.28em}{0ex}}^{3}\mathrm{He}$ reaction provided the quasimonoenergetic neutron beam. The experimental setup and methods used to determine the fission product yield (FPY) are described, and results for typically eight high-yield fission products are presented. Our FPYs for $^{235}\mathrm{U}(n,f), ^{238}\mathrm{U}(n,f)$, and $^{239}\mathrm{Pu}(n,f)$ at 8.9 MeV are compared with the existing data below 8 MeV from Glendenin et al. [Phys. Rev. C 24, 2600 (1981)], Nagy et al. [Phys. Rev. C 17, 163 (1978)], Gindler et al. [Phys. Rev. C 27, 2058 (1983)], and those of Mac Innes et al. [Nucl. Data Sheets 112, 3135 (2011)] and Laurec et al. [Nucl. Data Sheets 111, 2965 (2010)] at 14.5 and 14.7 MeV, respectively. This comparison indicates a negative slope for the energy dependence of most fission product yields obtained from $^{235}\mathrm{U}$ and $^{239}\mathrm{Pu}$, whereas for $^{238}\mathrm{U}$ the slope issue remains unsettled.