PWR fuel debris filtering performance measurement method and its application

• Test requirements are derived to provide guidelines that could minimize test results deviation between test programs.
• Binomial probability theory was introduced to analyze debris-filtering test results.
• A guide to determine the number of required objects is suggested, considering the constraints such as confidence interval and surrounding geometries.
• Various kinds of wire debris test were performed, and the results are discussed.
• Wire debris diameter tolerance was calculated based on the statistical evaluation.

This paper concerns a nuclear fuel debris-filtering test methodology based on experimental statistics. In nuclear power plants worldwide, one of the main fuel-failure mechanisms is debris-induced fuel failure. Therefore, fuel vendors have introduced several debris-filtering designs in their fuel, and they evaluate the filtering efficiency using in-house test methodologies. However, the debris is not uniform in shape and dimension. In general, an in-house method would not be applicable for a fair evaluation of other vendor's fuels. To provide a more objective-oriented test methodology, debris-filtering test requirements are proposed, and a generalized test method including a reference debris specimen is discussed. The required number of debris specimens is also discussed, considering the statistics, manufacturability, and other constraints. A filtering evaluation method is also provided. Many tests were performed with different wire dimensions to verify the suggested method, and the results are also discussed. The debris-filtering test results show that the suggested requirements could be realized, and the method could be applicable for a fair evaluation of the fuel performance.