Modeling Response Variation for Radiometric Calorimeters

Radiometric calorimeters are widely used in the DoE complex for accountability measurements of plutonium and tritium. Proper characterization of response variation for these instruments in. therefore, vital for accurate assessment of measurement control 8S well as for propagation of error calculations. This is not difficult for instruments used to measure items within a narrow range of power values, however, when a single instrument is used to measure items over a wide range of power values, improper estimates of uncertainty can result pi nee traditional error models for radioraetric calorimeters assume that uncertainty is not a function of sample power. This paper describes methods which can be used to accurately estimate random response variation for calorimeters used to measure items over a wide range of sample powers. The model is applicable to the two most common modes of calorimeter operation; heater replacement, and servo control.