242Pu absolute neutron-capture cross section measurement

M.Q Buckner,S Mosby,A Chyzh,R.A Henderson,J.L Ullmann,B Bucher,M Jandel,A Couture,B Baramsai,T.A Bredeweg,J.M O’Donnell,C.Y Wu

doi:10.1051/epjconf/201714611011

Abstract

The absolute neutron-capture cross section of 242 Pu was measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. During target fabrication, a small amount of 239 Pu was added to the active target so that the absolute scale of the 242 Pu(n,γ) cross section could be set according to the known 239 Pu(n,f) resonance at En,R = 7.83 eV. The relative scale of the 242 Pu(n,γ) cross section covers four orders of magnitude for incident neutron energies from thermal to ≈ 40 keV. The cross section reported in ENDF/B-VII.1 for the 242 Pu(n,γ) En,R = 2.68 eV resonance was found to be 2.4% lower than the new absolute 242 Pu(n,γ) cross section.

Highlights

The 242Pu(n,γ ) reaction is important because precision (n,f), (n,γ ), and (n,2n) cross sections are key input to network calculations of the radiochemical diagnostic chain
New reactor concepts rely on network calculations like the Pu-Am diagnostic chain and catalyzed interest in improved cross section measurements for neutron-induced reactions on actinides [1, 2]
The incident neutron energy, ranging from thermal to several hundred keV, is determined from the time-of-flight difference between the beam pulse and event detection. This experiment was performed over a period of 17 days with a 242Pu target installed within a parallel-plate avalanche counter (PPAC)

Summary

Introduction

The 242Pu(n,γ ) reaction is important because precision (n,f), (n,γ ), and (n,2n) cross sections are key input to network calculations of the radiochemical diagnostic chain. These calculations are a priority for the United States Department of Energy’s Stockpile Stewardship program and related initiatives. New reactor concepts rely on network calculations like the Pu-Am diagnostic chain and catalyzed interest in improved cross section measurements for neutron-induced reactions on actinides [1, 2]. Improved cross sections for neutron capture by 242Pu may impact calculations relevant to the development of next-generation reactors [2]

Experiment

Analysis

Results