Calibration and Error Reduction in Neutron Coincidence Counting

The accuracy in measuring the plutonium content by means of neutron coincidence counting can be improved by setting up sample categories and analyzing the categories differently. Four categories of materials are defined, and calibration procedures are recommended for each of the categories. Methods are given to identify which category a sample belongs in and techniques are described to reduce the measurement errors. New data arepresented to establish the validity of multiplication corrections, and the application of the correction to induced fissions in uranium as well as plutonium is investigated. Methods are outlined to solve the more general problem of plutonium assay when the (a,n) yield is unknown.