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Multiplication and Presence of Shielding Material from Time-Correlated Pulse-Height Measurements of Subcritical Plutonium Assemblies

Journal Article · · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
 [1];  [2];  [1];  [1];  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
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Here, we present the results from the first measurements of the Time-Correlated Pulse-Height (TCPH) distributions from 4.5 kg sphere of α-phase weapons-grade plutonium metal in five configurations: bare, reflected by 1.27 cm and 2.54 cm of tungsten, and 2.54 cm and 7.62 cm of polyethylene. A new method for characterizing source multiplication and shielding configuration is also demonstrated. The method relies on solving for the underlying fission chain timing distribution that drives the spreading of the measured TCPH distribution. We found that a gamma distribution fits the fission chain timing distribution well and that the fit parameters correlate with both multiplication (rate parameter) and shielding material types (shape parameter). The source-to-detector distance was another free parameter that we were able to optimize, and proved to be the most well constrained parameter. MCNPX-PoliMi simulations were used to complement the measurements and help illustrate trends in these parameters and their relation to multiplication and the amount and type of material coupled to the subcritical assembly.
Research Organization:
Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE National Nuclear Security Administration (NNSA), Office of Nonproliferation and Verification Research and Development (NA-22)
Grant/Contract Number:
AC04-94AL85000; NA0002534
OSTI ID:
1340272
Alternate ID(s):
OSTI ID: 1416598
OSTI ID: 1366710
Report Number(s):
SAND--2017-0183J; 650258
Journal Information:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment Journal Issue: C Vol. 851; ISSN 0168-9002
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (3)

Characterizing Subcritical Assemblies with Time of Flight Fixed by Energy Estimation Distributions text January 2018
Results of Three Neutron Diagnosed Subcritical Experiments journal December 2018
A Note on the Nomenclature in Neutron Multiplicity Mathematics journal January 2019

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Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Fission chain
Liquid scintillator
Subcritical assembly
Non-linear Inverse Problem
fission chain
liquid scintillator
non-linear inverse problem
subcritical assembly