2129 反応度投入事象模擬試験用の X 線ボイド率計の開発  [in Japanese] Development of X-ray void meter for RIA test  [in Japanese]

During a Reactivity Initiated Accident (RIA) in a boiling water reactor (BWR), rapid power increase might be occurred. In order to evaluate fuel rod integrity properly, it is very important to understand the void fraction behavior under rapid power increase. In this study, test section and X-ray void meter for RIA tests were developed. The test section was composed of 3×3bundle heater, upper and lower electrodes, channel box and pressure vessel. The direct heaters were used for 3×3 bundle in order to simulate rapid power increase during RIA event. Sampling rate for the X-ray void meter was 5 ms. Measuring axial length for the meter was 100mm. The accuracy of the developed void measurement system was verified by acrylic test piece simulating the two-phase flow. As the verification test result, the accuracy of the void meter was about 2%.