Application of pattern recognition techniques to location of impact sound sources on pressure vessels

Pattern recognition techniques for loose parts location in nuclear power reactors are investigated. The location method is based on determining a reference impact position closest to the unknown impact from a library in which data for reference impacts are listed. The values of sound amplitude and arrival time as obtained from accelerometers are used for the pattern information which is inherent in impact position. The distance between unknown and reference impact positions is estimated from the similarity of each pattern. The pattern distance between two sound sources is defined as an index of the pattern similarity. Relationships between the pattern distance and the actual distance of the impacts are studied using impact data from a commercial boiling water reactor. It is found that the pattern distance and the actual distance have a very close correlation and the false probability that the zero impact distance is determined to be a distance of more than 0.6 m is 0.15. These results suggest that the pattern recognition techniques can be applied to loose parts detection and location on pressure vessels. (author)