A New Apparatus for Determination of the Free Volume of a Fuel Rod Using the Double Expansion Method

A new method is proposed to measure the free volume and the gas content of a pressurized water reactor fuel rod using two expansions of the gas, one at high pressure and the other at low pressure. The gas flow corresponding to these expansions is characterized and modeled. The modeling is then used to prove that this new method is faster and more accurate than the ones usually adopted in hot cells, especially for high-burnup fuel rods.