A simulation experiment of the results of fission product gas release due to fuel cladding failure using water circulation system

Abstract To examine the effects of fission product gas release into the coolant channel due to fuel cladding failure, two preliminary simulation experiments were undertaken using an electrical heater pin set in a system for water circulation. The first experiment represented a continuous release of gas from a small hole in the cladding, and the second a sudden burst of gas into the system due to plenum rupture. The first experiment revealed that the cladding surface temperature registered a sharp dip at the stagnation point of the water flow created immediately upstream of the gas releasing hole and that the temperature at the bottom of the dip was very sensitive to the ratio between the gas release rate and water flow rate. In the second experiment, representing plenum rupture, a pressure pulse of about 8 kg/cm2 was registered on the wrapper tube, and the cladding surface temperature was found to rise by about 10°C within 0.1 sec (with heating at 100 W/cm), due to gas blanketing. The magnitude of the deformation and the transient strain on the cladding surface were also measured.