低放射化フェライト鋼F82Hの低放射化性能および課題

Radiological assessment of the limits and potential of reduced activation ferritic/martensitic steel F82H

谷川 博康; 染谷 洋二; 酒瀬川 英雄   ; 廣瀬 貴規; 落合 謙太郎

Tanigawa, Hiroyasu; Someya, Yoji; Sakasegawa, Hideo; Hirose, Takanori; Ochiai, Kentaro

構造材料の低放射化性能は、原型炉規模での製造技術ではCo, Cu, Ni等の不純物除去には現実的な限界があることが危惧されている。これまでの溶解および実規模技術相当となる20トン電気炉溶解で製作されたF82Hについて、代表的使用箇所毎の低放射化性能の評価を実施した。その結果、第一壁位置でNiおよびMo汚染除去が重要であり、かつ、製造工程の清浄化により達成可能であること、大型溶解で100ppmレベルの混入が避けられないN由来のCの除去が課題であること、脱酸元素のAlの影響は想定される濃度では問題にならないことが明らかになった。

The practical implementation of F82H pertaining to the element control and mechanical properties was reviewed, and the reduced activation level was discussed based on the data. It is found that Ni is the element that should be removed to reduce the activation levels, while preventing contamination during the melting process is essential for reducing Ni concentrations. Another element discussed is N. The amount of C transmuted from N must be reduced to achieve the shallow land burial limit. However, N plays an important role in the realization of high-temperature properties. Furthermore, at least 100 ppm of N will remain in the steel when large-scale melting by electric arc furnace is employed. Using Al for deoxidation of the RAFM steel has no significant impact on the activation levels, and the impact of the minor elements such as Ag is negligible compared to that of Ni and N. There is no way to reduce the decay heat by an order of magnitude because the main source elements of the decay heat are the key elements of RAFM, which cannot be reduced.