Year
1989
Abstract
Calorimetry is an important technique for use in the nondestructive measurement and assay of plutonium bearing materials. The technique has a number of advantages over other measurement methods such as passive neutron coincidence counting and destructive analysis. It does not suffer from neutron multiplication effects and it is not biased by inhomogeneity or the presence of moisture in the sample. Although it has been employed in the past as a method for calibrating other detectors and resolving anomalies, reductions in measurement times make the technique more applicable to bulk sample measurements and measurements of waste material. Recent improvements in gamma-ray isotopic analysis point the way to complete assay systems for field use which could partially replace destructive analysis in international safeguards applications.The calorimeter reported in this paper is a variable power device and may be configured to operate over a range of sample powers from 0 to 100 Watts. Measurements are reported covering the two power ranges of up to 15 Watts and up to 62 Watts. The calorimeter is provided with a sample pre-heater and two sample canisters, with internal dimensions 158.7 mm (6.25 in) internal diameter and 336 mm (13.2 in) internal height. Pre-heating has not been employed in the present measurements although sample equilibrium power prediction is used to reduce measurement times. A measurement of the overall calorimeter error (including heat distribution error) of 0.2% using a 5W sample is reported. Measurements on a range of low powered samples have been obtained with an accuracy of better than 1% for measurement times of about 2 hours with no pre-heating.