Abstract
Metallurgical tests on irradiated natural uranium fuels of the JAPCO's Tokai reactor were carried out at the Hot Laboratory, JAERI. During cutting the fuel, fission products in the fuel were dispersed inside the cave in the form of airborne material, and were released to the stack. The concentration of airborne fission products in the cave, in the exhaust ducts and in the stack were assessed by the air sampling. Dispersion factor, removal efficiency of the exhaust air filtering system and release fraction from the stack for fission products were obtained from the result of air sampling. Dispersion factor depends on the volatility of each fission product, for example, 4.4×10-3 and 2.0×10-3 for I-131 and Cs-137 respectively, and varies with cutting procedures. Removal efficiency of the exhaust air filtering system was found to be 80% for I-131 and about 97% for other fission products. Distribution of airborne fission products collected in three types of sampling medium i. e. cellulose-asbestos filter paper (HE-40), charcoal-impregnated filter paper (CP-20B) and charcoal cartridge are also described.
