Statistical estimation of the performance of a fast-neutron multiplicity system for nuclear material accountancy

David L. Chichester, Scott J. Thompson, Mathew T. Kinlaw, James T. Johnson, Jennifer L. Dolan, Marek Flaska, Sara A. Pozzi

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Statistical analyses have been performed to develop bounding estimates of the expected performance of a conceptual fast-neutron multiplicity system (FNMS) for assaying plutonium. The conceptual FNMS design includes 32 cubic liquid scintillator detectors, measuring 7.62 cm per side, configured into 4 stacked rings of 8 detectors each. Expected response characteristics for the individual FNMS detectors, as well as the response characteristics of the entire FNMS, were determined using Monte Carlo simulations based on prior validation experiments. The results from these simulations were then used to estimate the Pu assay capabilities of the FNMS in terms of counting time, assay mass, and assay mass variance, using assay mass variance as a figure of merit. The analysis results are compared against a commonly used thermal-neutron coincidence counter. The advantages of using a fast-neutron counting system versus a thermal-neutron counting system are significant. Most notably, the time required to perform an assay to an equivalent assay mass variance is greatly reduced with a fast-neutron system, by more than an order of magnitude compared with that of the thermal-neutron system, due to the reduced probability of random summing with the fast system. The improved FNMS performance is especially relevant for assays involving Pu masses of 10 g or more.

Original languageEnglish (US)
Pages (from-to)448-454
Number of pages7
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
StatePublished - Jun 1 2015

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Instrumentation


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