Year
1991
Abstract
The non-destructive measurement of Plutonium by calorimetry has advantages over both destructive and other nondestructive techniques such as passive neutron coincidence counting. Despite longer measurement times, the insensitivity of calorimetry to sample inhomogeneity, neutron multiplication effects and the presence of moisture makes the technique more reliable and more accurate. The applicability of the method has increased with the advent of isothermal calorimetry and the consequent reduction in measurement times without a loss of measurement accuracy. The present paper describes recent enhancements to both the hardware and software of the \"air bath\" isothermal calorimeter system which have been incorporated into the most recent production instrument. These include software control of measurement chamber operating power and temperature and an expert system software module to control the measurement process. The results of a measurement chamber power and temperature calibration are presented as are results from recent measurements of plutonium samples. In the case of preheated samples, measured sample power results with an accuracy of about 0.5 % are available in under an hour and often in less than 30 minutes. For samples which have not been preheated results are generally obtained in less than 2 hours with an accuracy of better than 0.5 %.