Neutron-neutron angular and energy-angle correlations of plutonium samples with varying <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e732" altimg="si76.svg"><mml:mi>α</mml:mi></mml:math>-ratio

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 µs. The known slowing down time of the 3 He system is 35-40 µs, 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 µs.

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Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory

Darby,

Hua,

Pakari

et al. 2023

American Journal of Physics

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In this advanced instructional laboratory, students explore complex detection systems and nondestructive assay techniques used in the field of nuclear physics. After setting up and calibrating a neutron detection system, students carry out timing and energy deposition analyses of radiation signals. Through the timing of prompt fission neutron signals, multiplicity counting is used to carry out a special nuclear material (SNM) nondestructive assay. Our experimental setup is comprised of eight trans-stilbene organic scintillation detectors in a well-counter configuration, and measurements are taken on a spontaneous fission source as well as two (α,n) sources. By comparing each source's measured multiplicity distribution, the resulting measurements of the (α,n) sources can be distinguished from that of the spontaneous fission source. Such comparisons prevent the spoofing, i.e., intentional imitation, of a fission source by an (α,n) neutron source. This instructional laboratory is designed for nuclear engineering and physics students interested in organic scintillators, neutron sources, and nonproliferation radiation measurement techniques.

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Neutron-neutron angular and energy-angle correlations of plutonium samples with varying α-ratio

Cited by 3 publications

References 19 publications

Analysis of radiation emission from MYRRHA spent fuel and implications for non-destructive safeguards verification

Analysis of radiation emission from MYRRHA spent fuel and implications for non-destructive safeguards verification

Rossi-alpha measurements of fast plutonium metal assemblies using organic scintillators

Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory

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