A study on the effect of PWR debris-filtering devices on filtering efficiency

The debris-filtering efficiency tests for debris-filtering devices used in the domestic PWRs, which are located at the bottom of PWR fuel assembly, were performed. The effect of debris flow paths on the debris-filtering efficiency were evaluated with the use of the 3-D Solidworks code model and the debris-filtering efficiency test results. Based on the debris-filtering efficiency and fabrication cost of the debris-filtering devices, a development guideline for an optimized debris-filtering device is proposed. In this study, two types of debris-filtering device were taken into account. The first type (A type) has a short debris-filtering grid closely attached to a small-hole bottom nozzle, while the second type (B type) a tall debris-filtering and rod-supporting grid located above a large-hole bottom nozzle. According to the debris-filtering tests results, both types of debris-filtering devices showed debris-filtering efficiency of greater than 90%. However, the type B generated better filtering efficiency especially for wire-type debris since its flow channels between a fuel rod and a grid cell is narrower and its debris-filtering dimple size is longer than those of the type A. In addition, the fuel fabrication cost for the type B is evaluated to be relatively low because the fabrication cost of the large-hole bottom nozzle is relatively cheap and the lowest bottom grid is not necessary as well