Research on consequence analysis method for probabilistic safety assessment of nuclear fuel cycle facilities (6). Examination of airborne release fraction for accidental leakage of molten glass

A special committee of 'Research on analysis methods for accident consequence in nuclear fuel facilities' was organized by the Atomic Energy Society of Japan under the entrustment of Japan Atomic Energy Agency (JAEA). The research results were summarized in a series of six reports, which consist of the general report and five technical ones. This is the fifth technical one dealing with airborne release fraction (ARF) in the case of accidental leakage of molten glass from a vitrification melter. In the effective dose assessment of the design basis accident of the molten glass leakage at the Rokkasho Reprocessing Plant, ARFs of 1 for Ru and Cs and of 0.1 for nonvolatile elements, such as Sr and minor actinides, were used. In the present report, more realistic values of 1x10-3 for Cs, 5x10-5 for Ru, and 10-8 for nonvolatile elements, such as Sr and minor actinides, were proposed for risk assessment; these values were obtained by calculation using the measured volatilities of these elements at high temperatures of 800-1,100degC reported in the literature. Although these values depend on the scale and conditions of the leakage, they are given as maximums irrespective of the conditions. (author)