Evaluation of the neutron self-interrogation approach for assay of plutonium in high-. cap alpha. ,n materials

Abstract

Neutron self-interrogation is a proposed method for assay of plutonium in bulk materials with very high ..cap alpha..,n activity. The simple assay approach assumes that neutron multiplication for the calibration standards is the same as that for the bulk items. Efforts to use bulk properties to determine corrections to the calibration for changing multiplication have been initiated. Self-interrogation assays of bulk pyrochemical residues have been performed. Comparison with tag values obtained by difference gives poor agreement. Comparison with tag values obtained by dissolution and destructive analysis gives agreement at the 10% (1sigma) level with no corrections for changing package dimensions or matrix amounts. The agreement improves by a factor of 2 or more if a bulk correction factor (derived from a packaging/matrix study with standards) is applied