Feasibility Study on Power Ramp Test Under Atmospheric Pressure and Ordinary Temperature

Pellet-to-cladding mechanical interaction is an important physical phenomenon during reactor power change as well as a multi-phenomenal fuel rod failure mechanism involving stress, strain and material irradiation properties. In order to avoid the failure caused by PCMI, a large number of power ramp tests have been carried out by international organizations over the past decades. The typical way of power ramp test in a high temperature and pressure loop requires stringent test capabilities and high test costs. The key parameters of the PCMI phenomena are stress and strain of cladding, which are generally chosen as the evaluation indicators of PCMI. If it is possible to simulate the pellet-to-cladding contact state, i.e. the gap between pellet and cladding under basic irradiation power level in atmospheric pressure and ordinary temperature environment, then the high stress and strain state of the cladding during the subsequent power ramp test could also be simulated in the same environment, which means lower test costs and test loop requirements. Therefore, a sensitivity analysis using the fuel rod performance analysis code RoPE, was carried out on factors such as initial pellet-to-cladding gap and fuel densification in the power ramp test rod design. By adapting the manufacturing parameters of the test rod and coolant conditions, the high stress and strain state of the cladding could be simulated in the test environment at normal temperature and pressure. The sensitivity analysis provides a theoretical basis for conducting power ramp tests in an atmospheric pressure and ordinary temperature loop.