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Report No.

Impact of N-isotope composition control of ferritic steel on classification of radioactive materials from fusion reactor

Hayashi, Takao; Kasada, Ryuta*; Tobita, Kenji; Nishio, Satoshi; Sawai, Tomotsugu; Tanigawa, Hiroyasu; Jitsukawa, Shiro

The impact of increasing the enrichment of $$^{15}$$N in low activation ferritic steel, F82H, of a fusion reactor has been investigated in order to increase the fraction of low level material (LLM), which can be disposed by shallow land burial. Carbon-14, mainly produced from nitrogen, is one of the most critical nuclei for qualifying as a LLM. The concentration of nitrogen in F82H is 200 ppm in the calculations. The enrichment of $$^{15}$$N was varied from natural abundance of 0.37% to 95%. The concentration of $$^{14}$$C at the outboard first wall decreased from 7.8 $$times$$ 10$$^{4}$$ to 3.2 $$times$$ 10$$^{4}$$ Bq/g by enriching $$^{15}$$N, which is lower than the $$^{14}$$C regulation (3.7 $$times$$ 10$$^{4}$$ Bq/g) for LLM in Japan. In the permanent blanket, the highest $$^{14}$$C concentration with 95% $$^{15}$$N enriched nitrogen was 1.0 $$times$$ 10$$^{4}$$ Bq/g. The $$^{14}$$C concentration on the inboard side was lower than the outboard side. Therefore, with regard to the $$^{14}$$C concentration, the F82H used in the inboard and outboard blankets can qualify as a LLM by enriching $$^{15}$$N.



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Category:Nuclear Science & Technology



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