Year
1992
Abstract
Calorimetry is an accurate technique for measuring the thermal power of heat producing samples and has gained wide acceptance as a technique for the measurement of plutonium. Recent improvements in the precision of gamma-ray measurement methods used for the determination of plutonium isotopic ratios have led to an improvement in the overall accuracy of the calorimetry technique applied to plutonium measurement. In order to further optimise calorimeter performance, and in particular to reduce measurement time, a two dimensional heat-transfer computer model of a general isothermal plutonium calorimeter has been developed. The model, which can compute timedependent conduction and radiation heat-transfer in cylindrical geometry, is based on the finite-difference solution to the heat conduction equation. It also contains the temperature control algorithms used in the servo-control of the device. The model, which is applicable to a range of calorimeter types, has an important role in the study of the underlying heat-transfer mechanisms which govern the operation of calorimeters. In the present work the calorimeter model has been used to investigate the behaviour of calorimeter measurement chamber power, axial and radial temperature profiles, the change in temperature profiles due to the presence of a sample and the effects of different sample-calorimeter coupling materials. The results suggest ways of improving calorimeter design and calorimeter performance.