Distinguishing Pu metal from Pu oxide and determining α-ratio using fast neutron counting

We describe a new method for determining the ratio of the rate of (α,n) source neutrons to the rate of spontaneous fission neutrons, the so-called α-ratio. This method is made possible by fast neutron counting with liquid scintillator detectors, which can determine the shape of the fast neutron spectrum. The method utilizes the spectral difference between fission spectrum neutrons from Pu metal and the spectrum of (α,n) neutrons from PuO2. Our method is a generalization of the Cifarelli-Hage method for determining keff for fissile assemblies, and also simultaneously determines keff along with the α-ratio.