Compressibility of gas mixtures pertaining to nuclear fuel rods

Gas pressure inside an irradiated nuclear fuel rod impacts its performance and safety. To accurately assess the pressure inside a rod, the temperature, composition, quantity, volume, and compressibility of a gas must be determined. The compressibility of a pure gas, Ar, and gas mixtures; 98%Ar:2%H-2, 50%Xe:50%He, and 11.3%He:12.9%Xe:75.8%Kr, were experimentally derived in the pressure range of 65 to 10,400 kPa at 293.7 +/- 1.5 K isotherm. The Analytical Research Laboratory at Idaho National Laboratory has been performing gas compressibility experiments to improve plenum-pressure determination of fuel rods. For each gas mixture, the compressibility was calculated for a series of pressure measurements. A second-order polynomial function was fit to the data set, allowing for the determination of the first-, second-, and third-order virial coefficients and their uncertainties. This method for determining virial coefficients and their application for determining plenum-gas pressures refines previous methods.