Year
2009
Abstract
This paper describes the design and operation of a large volume twin cell heat-flow calorimeter intended for the measurement of samples containing either tritium or plutonium. In contrast to isothermal calorimeters, which are optimized for shorter measurement times with adequate measurement precision, this large volume twin cell heat-flow calorimeter is based on updating the design of the traditional twin cell heat-flow calorimeter, which is characterized by long measurement time constants. The advantage of the twin cell heat-flow method is that better measurement precision can be achieved for large volume measurement cells. Through the use of high output voltage thermopile differential temperature sensors and enhanced thermal insulation, a significant sensitivity improvement has been achieved for a large volume measurement cell (typically 50 litres in volume). The transportable calorimeter incorporates a removable electrical calibration heater and a method of controlling the calorimeter peripheral temperature environment without using a liquid coolant. Eliminating the liquid coolant reduces any potential criticality hazard and the possibility of tritium contamination of the coolant. The thermal performance of the calorimeter is considered and measured data for different sample powers is presented. Calorimeter measurement sensitivity is determined using electrical calibration data and results for measurement precision and accuracy are presented.