The capability of evaluating pipeline accidents is an important ability for a nuclear power plant. The emergency core cooling system (ECCS) is designed based on the loss of cooling water accident (LOCA), rod ejection accident, steam-line break accident, and steam-generator tube rupture, to refill the coolant to the reactor cooling system. A spectrum of the LOCA includes widely range from the largest pipe is completely broken in an instant to a small pipe is broken or pressure relief valves are stuck. The LOCA break sizes related to the peak cladding temperature (PCT) has been found by many researchers. The PCT corresponds to an abounding estimate of the 95h percentile PCT at the 95-percent confidence level. It has been demonstrated that the PCT and maximum cladding oxidation limits are still the Best-Estimate LOCA applications. Based on the multi-redundant and diversity of the safety system, this study is discussed on the break sizes to a LOCA and evaluated the break sizes by the temperature difference of the coolant at inlets. The temperatures were determined by using the realistic evaluation code to simulate the temperature changed at each monitored location when LOCAs occurred at the recirculation loop of BWR.The results showed that the temperature difference has the potential to replace or to alternate the PCT as estimating the break size.Some brief conclusions of this study were obtained as the following:&nbsp;&nbsp;&nbsp;&nbsp;1. The break sizes were related to the PCTs, and they could be well fitted by many mathematic applications; however, the PCT was a derived theoretical value or existing uncertainty.2. The maximum temperature difference was more suitable to evaluate the break size in a conservative manner.&nbsp;Not only the flow-rate, the pressure, and the temperature, etc. but also the temperature difference can help the main decision-maker to make an appropriate decision. As more information becomes available, then more information could be used to modify the models. More uncovering hidden safety margins might be improving the plant operation performances and economics.

The Evaluation of Break Sizes of Loca by Temperature Difference at the Recirculation Inlets of Bwr

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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