Fission Product Chain Yield Measurements at NCERC

Fission product chain yields were historically determined by chemical separation and beta counting of fissile samples irradiated in carefully controlled fission chamber experiments$^{1,2}$. These measurements provided the means to extract absolute fission product yields (yield per fission, or $Y_i/f$ for the $i^{th}$ fission product) that are included in the international nuclear data libraries, and ultimately used to model and characterize multiplying systems. However, re-evaluations conducted at Los Alamos National Lab and Lawrence Livermore National Lab in 2005-2009 for neutron-induced fission of $^{235}$U and $^{239}$Pu highlighted disagreement among many of the measurements$^{1,2,3}$. This led to several new, targeted experimental programs to resolve these disagreements. In this presentation we will highlight recent efforts to address these discrepancies using energy-integral measurements at the National Criticality Experiments Research Center (NCERC), and outline our plans to complete the work over the next several years. \\[0.25cm] \noindent $^1$ H.D. Selby, \textit{et al.}, Nucl. Data Sheets 111, 2891 (2010) \\ $^2$ M.B. Chadwick, \textit{et al.}, Nucl. Data Sheets 111, 2923 (2010) \\ $^3$ J. Laurec, \textit{et al.}, Nucl. Data Sheets 111, 2965 (2010)