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FAST ROSSI-ALPHA MEASUREMENTS OF PLUTONIUM USING ORGANIC SCINTILLATORS

2021; EDP Sciences; Volume: 247; Linguagem: Inglês

10.1051/epjconf/202124709025

2101-6275

Michael Y. Hua, Caiser A. Bravo, Aaron T. MacDonald, Jesson Hutchinson, George McKenzie, Travis Grove, Joetta Goda, Alexander McSpaden, Shaun D. Clarke, Sara A. Pozzi,

Nuclear Physics and Applications

In this work, Rossi-alpha measurements were simultaneously performed with a 3 He-based detection system and an organic scintillator-based detection system. The assembly is 15 kg of plutonium (93 wt% 239 Pu) reflected by copper and moderated by lead. The goal of Rossi-alpha measurements is to estimate the prompt neutron decay constant, alpha. Simulations estimate k eff = 0:624 and α = 52:3 ± 2:5 ns for the measured assembly. The organic scintillator system estimated α = 47:4 ± 2:0 ns, having a 9.37% error (though the 1.09 standard deviation confidence intervals overlapped). The 3 He system estimated α = 37 μ s. The known slowing down time of the 3 He system is 35-40 μ s, which means the slowing down time dominates and obscures the prompt neutron decay constant. Subsequently, the organic scintillator system should be used for assemblies with alpha much less than 35 μ s.