Patent Document ID: 8180013
Application ID: 12147374
Patent Status: 1

Claim One:
1. A method of absolute nuclear material assay of an unknown source comprising: detecting neutrons emitted from the unknown source, and grouped with respect to time; collecting a number of neutrons within a defined time window to derive neutron multiplet count data; measuring the multiplet count as a function of lifetime and neutron number; iteratively solving a plurality of coupled algebraic equations for five unknown parameters of the source using the first three moments of a fission chain distribution, wherein the parameters comprise mass, multiplication, alpha ratio, detector efficiency, and time constant (lambda); fitting the time constant parameter to the actual time dependence of the moments to reduce the unknown parameters to four parameters of mass, multiplication, alpha ratio, and detector efficiency; comparing truncated data moments representing a measured count distribution with untruncated and truncated theoretical moments representing a model count distribution to provide an estimation of the four parameters and to allow for solution of the remaining three parameters using the first three moments; using the estimation of the four parameters to determine the bias caused by finite sampling error; and adjusting the truncated data moments and the untruncated and truncated theoretical moments to reduce the bias in the measured count distribution and the model count distribution.