トカマク型核融合炉を定常化するためには,プラズマ電流駆動技術の開発が必須である。中性粒子入射による電流駆動・加熱の物理は古典的であり確実性が高い。FER級の次期装置で有効な電流駆動を行うためには,500keV以上のエネルギーを必要とするが,正イオン源を用いた入射装置でこのエネルギーの中性粒子を高効率で得ることは不可能に近く,従来有望視されなかった。しかしながら,最近負イオン源の開発が急速に進展し,これを用いた入射装置が電流駆動技術としても脚光を浴びるようになってきた。本稿では,負イオン源が必要とされる理由,および現在までの開発状況等を概説する。

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MeV領域の重イオンが高密度媒質である固体(薄綾)との衝突で行5電荷交換と薄膜通過後に星する電荷分布について概観する。まず,データの実鶏盤という観点から,薄膜を通過した重イオンの平衡電荷分布や平均電荷の,衝突エネルギーやイオンおよび薄腰の種類に対する系統性を述べ,次に薄膜内で電荷平衡に達する深さについて言及する。さらに電荷分布の散乱角依存や殻効果に触れた後,X線の測定による薄膜内でのイオン励起および電荷状態の診断の可能性について述べる。

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宇宙用原子炉の研究開発は米国において30年の慶史を有するが,最近に至り,スペースシャトルに積載可能な100kWe級の原子炉に関心が集まっている。そこで,その背景,提案されている原子炉の概要,実現に至るまでに解決すべき技術課題などについて解説を行う。

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Activities of Research Committee on Thorium in Nuclear Power Reactors were summarized and prospects and problems in the utilization of thorium fuels were reviewed. The present status and problems of thorium resources, thorium fuels of high-temperature gas-cooled reactors, reprocessing of thorium fuels were reviewed, and summaries of the several papers presented at the Japan-US Seminar on Thorium Fuel Reactors, October 1982, which discussed especially on the strategy of thorium fuel utilization and the design of thorium fuel reactors, were also given.

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Opinions of students of Tokyo Gakugei University concerning the energy problems are investigated. Comparison is made between the natural science group (231 students) and the non-natural science group (162 students: about 1/4 mathematics, about 3/4 literature, art etc.).
The majority choose nuclear fission, nuclear fusion and solar energy as future energy. About half of them are in favour of development of nuclear fission, but about 1/3 wants keeping nuclear fission at the present level or abolishing it. The science group is more favourable to nuclear fission. Oil depletion is the strongest reason for development of nuclear fission, while the problem of radioactive wastes is the strongest reason for opposition, major accidents being the second. Most of the students oppose construction of nuclear power plants in their neighbourhood, but the science group is more favourable to the construction than the non-science group. Knowledge about natural radiations is very poor, but about 1/41/5 knows the release of radioactivities from thermal power plants. Knowledge about the greenhouse effect is unexpectedly high. Especially 81% of male students in the science group knows it.
The majority do not understand the energy balance of nuclear energy, but those who answer that the energy balance holds is more than those who answer that it does not. In general the science group and males answer more correctly and are more favourable to nuclear fission. Comparison with other opinion polls is made and it is found that their general tendencies are in agreement.

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1986年ANS年会が6月16～19日にわたって開かれた。筆者は,その一部として開かれた核融合エネルギー技術に関するトビカルミーティングに液体金属MHD関連の論文発表を行なったが,折から上記の特別セッションもあったのでそれにも出席した。セッションは,年会初日の16日の夕刻18時から約2時間開かれ,年会登録者豹1,200名中,半数近くが出席した。日本からも,安全研究専門家である原研・早田室長をはじめ10名ほどが参加し,電力会社の在米駐在員,その他在米邦人もかなり出席した模様である。セッションはIAEA原子力安全部長のMorris ROSEN博士の「チェルノブイリ事故とIAEA」と題する講演を中心に進められた。その内容は,出発前に原研・能澤理事を初め数人の方々からご教示いただいた予備知識に比べ,特に目新しいものではないと思われたが, IAEAが今後採るべき方向をある程度明確にさせているので,以下にローゼン博士の発言を伝える形で講演の主な内容と質疑の概要を参考資料として紹介する。

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JT-60 power tests were carried out from Dec. 10, 1984 to Feb. 20, 1985 to demonstrate, in advance of actual plasma operation, satisfactory performance of tokamak machine, power suppliers and control system in combination. The tests began with low power test of individual coil systems and progressed to full power tests. The coil current was raised step by step, monitoring the mechanical, thermal, electrical and vacuum data.
Power tests were concluded with successful results. All of the coil systems were raised up to full power operation in combination and system performance was verified including the structural integrity of tokamak machine. Measured strain and deflection showed good agreements with those predicted in the design, which was an evidence that electromagnetic forces were supported as expected in the design. A few limitations to machine operation was made clear quantitatively. And it was found that existing detectors were insufficient to monitor machine integrity and two kinds of detector were proposed to be installed.

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The influence of burn-up and design parameters of 17×17 current PWR type fuel rod on pellet-cladding interaction (PCI) under power ramping, was studied with light water loop instrumented in HBWR. The obtained results are as follows:
(1) With increase of bum-up, the PCI became large. With reduction of diametral gap and decrease of fill gas pressure, the PCI became large. The usage of chamfered dish pellet with small L/D instead of non-chamfered dish pellet with large L/D, could reduce the PCI.
(2) At the averaged burn-up of 18 MWdilcgU, a standard PWR rod was subjected power cyclings (power range 30 to 45 kW/m with period 2025 min.) to 620 times without no failure during the course of cycling. The power overshooting was occurred repeatedly, accompanying with the increase of PCI. Fission gas release rate of the cycled rod was almost equal to that of the reference one. It indicated that the enhancement of FP gas release during cycling was little. It was also revealed that FP gas release rate was roughly dependent on square root of time.
(3) At the burn-up of 12 MWd/kgU, one rod failed by PCI. The fuel behavior during failure occurring was pursued on time using in-core. measuring system.

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