Downcomer effective water head during reflood in postulated PWR LOCA.

概要

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A study was conducted of the downcomer effective water head which is the only driving force to supply emergency core coolant into core during reflood phase in a PWR loss-of-coolant accident.<BR>With a full height downcomer simulator, effective water head experiments were carried out under 1 atm to investigate the applicability of the correlation for void fraction for evaluating the effective water head as well as to investigate the effect of the scale factor.<BR>As the results, the effect of the scale factor (the gap of the downcomer) was revealed to be significant, that is, the smaller gap gives the smaller effective water head. From the comparison of predictions based on the correlation for void fraction with the experimental results, it was revealed that (1) for a slow effective water head change expected in the reflood phase, the used correlation gives a good prediction for the experi-mental results and that (2) for a rapid change of effective water head, however, more elaborate investigation is needed. It was revealed that for a rapid change of effective water head, the change of the saturation temperature due to the pressure change with time should be taken into account for evaluating the steam generation which is a key variable in the correlation.
一般社団法人日本原子力学会の論文