Published: 1958
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Experiments in the controlled melting of irradiated fuel speciman, particularly of the APPR, STR, and MTR types, have confirmed that prolonged heating in air at temperatures in excess of the melting point results in the release of a large portion of the radioactivity. On the other hand, a moderate amount of heating in air or steam sufficient only to melt a specimen results mainly in the partial volatilization of rare gases, iodine, bromine, cesium, and rubidium. In the presence of air or water vapor, strontium and other fission products are not released. At trace concentration of fission products, slow melting of the APPR plate at 1525 d C in air or steam effected the release of 50% of the rare gases, 33% of the iodine, 9% of ihe cesium, and traces of strontiuun. After 25% burn-up, the cesiuun value increased to about 60%. Aluminum alloy of the MTR type, also at trace concentration, upon melting at 700 d C released up to 2% of the iodine, 10% of the rare gases, and negligible portions of other fission products. Zirconium alloy of the STR type after 15% burn-up, when melted at 1850 d C, released up to 95% of the rare gases, 90% of the cesium, 60% of the iodine, and only a trace of strontiuun. (auth).