Speaker
Description
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 in the late 2010s for neutron-induced fission of $^{235}$U and $^{239}$Pu highlighted disagreement between several measurements$^{1,2,3}$. This resulted in new, targeted experimental programs, both in France and in United States, to understand and resolve these disagreements. It has also spark a renewed interest in creating a new fission product yield evaluation that includes energy differential and energy integral fission product data that has been collected over the past 2+ decades, and is still being collected today.
In this presentation we will highlight recent efforts to address discrepancies and data gaps using energy-integral measurements for $^{235}$U and $^{239}$Pu. This work relies on the historical combination of fission chambers and radiochemical analyses of samples irradiated at the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Site. Details will be provided on the design and performance of the fission chambers, along with the results from irradiations on the Flattop and Godiva critical assemblies. We will conclude with an outline our plans to complete the work over the next several years.
This work was funded in part by the Office of Defense Nuclear Nonproliferation Research and Development of the U.S. Department of Energy’s National Nuclear Security Administration.
This work utilized the National Criticality Experiments Research Center supported by the Department of Energy's Nuclear Criticality Safety program with financial support from the National Nuclear Security Administration's Office of the Chief of Defense Nuclear Safety, NA-511.
$^1$ H.D. Selby, \textit{et al.}, Nucl. Data Sheets 111, 2891 (2010)
$^2$ J. Laurec, \textit{et al.}, Nucl. Data Sheets 111, 2965 (2010)
$^3$ M.B. Chadwick, \textit{et al.}, Nucl. Data Sheets 111, 2923 (2010)