System and Method for Analysis of Fissionable Materials by Neutron Energy Discrimination

Patent metadata

Field	Value
Publication number	US-2016334536-A1
Application number	US-201515111920-A
Country	US
Kind code	A1
Filing date	Jan 16, 2015
Priority date	Jan 16, 2014
Publication date	Nov 17, 2016
Grant date	—

Abstract

The detection and assay of fissionable material is carried out on a container known or suspected to have a material with at least one fissionable isotope. The material is irradiated with neutrons from two or more different neutron sources. The fission rates inducted at each irradiation energy are acquired with at least one neutron detector. A multispectral active neutron interrogation analysis (MANIA) is carried out to compare the detected fission rates of the neutron spectra with calculated fission rates where an iterative algorithm is carried out on a system of linear equations to solve for the isotopic composition of one or more isotopes to determine the presence, identity, and quantities of fissionable isotopes in said container.

First claim

We claim:

1 . A method of assaying fissionable material, comprising:
providing a material comprising at least one fissionable isotope sequentially irradiating said material with a plurality of incident neutron energies from a plurality of different neutron sources; acquiring a fission rate induced in said material at said plurality of incident neutron energies using at least one detector; performing a multispectral active neutron interrogation analysis (MANIA), where detected fission rates determined from said neutron spectra are compared to calculated fission rates for isotopic compositions of at least one isotope by an iterative algorithm using a system of linear equations, wherein identities and quantities of said fissionable isotopes in said material are determined.

2 . The method of claim 1 , wherein said neutron sources are selected from a D,D generator, a D,T generator, a radioisotope source, and a nuclear reactor.

3 . The method of claim 1 , wherein said neutron detector is a 4 He gas scintillation detector.

4 . The method of claim 1 , wherein said MANIA comprises:
inputting a geometry of irradiation of said material; inputting said detected fission rates; and carrying an iterative calculation and comparison comprising:
a) inputting an anticipated fissionable isotope composition as a test fissionable isotope composition;
b) calculating expected fission rates for said test fissionable isotope composition;
c) checking for convergence of said expected fission rates and said detected fission rates;
d) if said expected fission rates and said detected fission rates are not effectively equal, proceeding to step e), or if said expected fission rates and said detected fission rates are effectively equal, proceeding to step h);
e) calculating effective cross-sections;
f) updating said test fissionable isotope composition from said calculated cross-sections;
g) proceeding to step b);
h) outputting said identities and quantities of fissionable isotopes in said material.

5 . The method of claim 1 , wherein said geometry of irradiation can be constructed for use with a cargo container, a rail car, a nuclear waste stream container, a spent fuel cell, or a nuclear material enrichment sample container.

6 . A system for assessment of fissionable material, comprising a plurality of different neutron sources, a plurality of neutron detectors; and a processor configured to accept input from said neutron detectors and a user; and software for a multispectral active neutron interrogation analysis (MANIA), wherein a container expected to contain a fissionable material proximal to said neutron sources and said neutron detectors is irradiated from said neutron sources and identities and quantities of fissionable isotopes in said container are determined.

Assignees

• Univ Florida

Inventors

• Jordan Kelly A
• Lewis Jason M

Classifications

• G01V5/0091 Primary

  Physics · mapped topic

• G01V5/281 Primary

  detecting special nuclear material [SNM], e.g. Uranium-235, Uranium-233 or Plutonium-239 · CPC title