高速中性子照射の反跳効果を利用した放射性金属内包フラーレンの生成効率向上

Improvement in production yield of radioactive strontium endohedral fullerene using nuclear recoil

宮下 由香*; 秋山 和彦*; 初川 雄一; 久冨木 志郎*

Miyashita, Yuka*; Akiyama, Kazuhiko*; Hatsukawa, Yuichi; Kubuki, Shiro*

金属内包フラーレンの放射薬品への利用を考えるとき、反跳反応を利用した製造法はほかにない高い比放射能試料が得られるので大きな優位性を有し注目される。しかし従来の研究では放射線損傷などのために低い収率に留まっておりその実用には困難であった。本研究では14MeVの加速器中性子核反応によるSr(n,2n)Sr反応を用いてSr内包金属フラーレンの製造に成功した。この方法によって生成されたSr内包金属フラーレンは全Srに対して6.8%という高い生成収率を得ることができた。この値は一般の金属内包フラーレンの回収率が0.1%以下であることを考慮すると大変高い値を示している。

Considering about the radio pharmaceutical application of metallofullerenes, the production methods using nuclear recoil phenomena is very useful because specific radioactivity of products is higher than that obtained by other methods. Due to these advantages, this production method has been attracted and examined using various nuclear reactions so far. However, reported production yields of radioactive metallofullerenes were not enough because of the radiation damages of a targeted fullerene molecule caused by incident charged particles. One of the promising method to improve the production yield of radioactive metallofullerenes is ion implantation using the nuclear recoil induced by nuclear reaction with fast neutrons. In this study, we will report the synthesis of Sr endohedral fullerene using the nuclear recoil of Sr (n, 2n) Sr reaction with 14 MeV fast neutron produced by DT reaction. As a result, the radioactivity of Sr observed in the aniline solutions derived from Sr endohedral fullerene was estimated to be about 6.8% at the best for those before extraction. Generally, production yield of metallofullerenes by the standard arc discharge method is about 0.1% or less. Therefore, observed production yield of Sr endohedral fullerene in this study is found to be extremely efficient compared to the standard methods.