Ramp behaviour of fuel elements

The results of an investigation into fuel pin behaviour during power ramps are reported. Following postirradiation studies of power and research reactor fuel pins, a relevant model was developed to cover both fuel pin chemistry and also fuel pin mechanics which necessitates a correct description of the initial state of the fuel pin (a function of the previous power history), the burnup level and fuel pin design. The interference between fuel pellet and clad is regarded as an easily determinable parameter, which has been used as a criterion for a systematic arrangement of the results which indicate that a good fuel element behaviour can be expected for all KWU light water reactors under all operating conditions. (UK)