The Use of High-Resolution Gamma-Ray Spectrometry for Detecting Failure of Cladding in Encapsulated Fast Reactor Fuel Pins

摘要

A nondestructive technique utilizing precision gamma-ray scanning has been developed for detecting fuel cladding failure in doubly encapsulated fast reactor fuel elements. Detection of fission products, in particular 137Cs, outside the fuel pin envelope was used to indicate the failure. The method was tested by examining eleven mixed uranium-plutónium carbide and two mixed uranium-plutónium oxide fuel elements. Gamma-ray scanning indicated that six of the thirteen fuel elements had failed. These results were confirmed by mass spectrometric analysis of the gases in the outer encapsulation which were found to contain 11. 7 to 65. 0％ xenon and 1. 76 to 9. 31％ krypton. The cover gas from a seventh pin contained only 0. 016％ xenon and < 0. 003％ krypton, and the presence of 137Cs outside the cladding was not conclusively detected by gamma-ray scanning. Cesium-137 was not found in the outer encapsulation of the six other fuel elements by gamma-ray scanning, and mass spectrometric analyses confirmed that the cladding had not failed.