Self-limiting power excursion characteristics of light water reactor, (5)

The Doppler effect and its influence on the shape of the power burst are studied by analyzing the experimental data from self-limiting power excursion tests on the HTR (Hitachi Training Reactor)-P core (UO2 ceramic fuel, water moderated, enriched to 10% in 235U). Uniform temperature distribution in the fuel element has usually been assumed hitherto for evaluating the Doppler reactivity feedback during a power excursion. In the HTR experiment, however some discrepancy is found in the power transient curve between the experimental results and the calculation with uniform temperature model. It is shown that most of this discrepancy can be explained as being due to the influence of the transient variation of the non-uniform temperature distribution in the fuel element, and also to the large contribution of the surface term of the effective resonance integral.