A Method for Estimation of Fissile Mass by a Measurement of the Number of Neutron Signals in Time Intervals

The purpose of this paper is to present a new method for the estimation ofs- sile mass by a measurement of the number of neutron signals in time intervals. The method uses the stochastic transport equation to express therst three central mo- ments (mean, variance and skewness) of the number of neutron detections in a time interval in terms of thessile mass, the (,n) rate and the multiplicity factor. Solving the three equations allows estimation of thessile mass. Therst to use the stochas- tic transport equation to characterize nuclear systems was Feynmann in his work in 1946. The two main advantages of the proposed method, compared to the multiplicity method, are the simplicity of implementation and the higher eciency thus requires relatively shorter measurement time. The method was implemented for severalssile mass measurements, which were conducted by the Nuclear Security Unit of the JRC in Italy and by the Institute of Isotopes, Hungar