Passive assay of plutonium metal plates using a fast-neutron multiplicity counter

A. Di Fulvio, T. H. Shin, T. Jordan, C. Sosa, M. L. Ruch, S. D. Clarke, D. L. Chichester, S. A. Pozzi

Research output: Contribution to journalArticlepeer-review


We developed a fast-neutron multiplicity counter based on organic scintillators (EJ-309 liquid and stilbene). The system detects correlated photon and neutron multiplets emitted by fission reactions, within a gate time of tens of nanoseconds. The system was used at Idaho National Laboratory to assay a variety of plutonium metal plates. A coincidence counting strategy was used to quantify the 240Pu effective mass of the samples. Coincident neutrons, detected within a 40-ns coincidence window, show a monotonic trend, increasing with the 240Pu-effective mass (in this work, we tested the 0.005–0.5 kg range). After calibration, the system estimated the 240Pu effective mass of an unknown sample (240Pueff>50 g) with an uncertainty lower than 1% in a 4-min assay time.

Original languageEnglish (US)
Pages (from-to)92-101
Number of pages10
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
StatePublished - May 21 2017
Externally publishedYes


  • Fast-neutron multiplicity counter
  • Organic scintillators
  • Plutonium metal
  • Safeguards

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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