Direct fissile assay of enriched uranium using random self- interrogation and neutron coincidence response

摘要

Apparatus and method for the direct, nondestructive evaluation of the . sup.235 U nuclide content of samples containing UF.sub.6, UF.sub. 4, or UO. sub.2 utilizing the passive neutron self-interrogation of the sample resulting from the intrinsic production of neutrons therein. The ratio of the emitted neutron coincidence count rate to the total emitted neutron count rate is determined and yields a measure of the bulk fissile mass. The accuracy of the method is 6.8% (1&sgr;) for cylinders containing UF. sub.6 with enrichments ranging from 6% to 98% with measurement times varying from 3-6 min. The samples contained from below 1 kg to greater than 16 kg. Since the subject invention relies on fast neutron self- interrogation, complete sampling of the UF.sub.6 takes place, reducing difficulties arising from inhomogeneity of the sample which adversely affects other assay procedures.