Progress and current status of research and development on the reprocessing technology of fast breeder reactor spent fuel in Power Reactor and Nuclear Fuel Development Corp. are reviewed in this report, involving the basic principle, target and arrangement of R & D, the present situation of R & D of individual subject and the plan of reprocessing facility.

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Outline and status of development of RF plasma heating system is reviewed. Plasma heating experiments in tokamaks have been presented, in particular, progresses in Japan have been introduced in relation to world wide progresses. Technical problems in application to coming fusion reactors as well as competitivity and compatibility with neutral beam heating have been referred.

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Stainless-steel-sheathed and inconel-sheathed cables with the outer diamete of 1.0mmφ were welded to nipples of stainless steel or inconel by two methods with an electron-beam and a microplasma-arc. The performance of the welds was examined through electrical insulation, autoclave, tensile and bending tests as well as metallographical examinations.
The electrical insulation and autoclave tests showed that the welded parts by both methods have the capability of excellent sealing in a high-temperature and high-pressure water environment such as in the in-core of LWR. The metallographical examinations, however, showed that the grain growth and structure change in the vicinity of the welded part were comparatively marked in the case of micro-plasma-arc welding. The tensile strengths were about 20-30kg in both cases, and the bending strength, i.e. the repetition number of bending between +45° and -45°, exceeded 40 times until the cable broke. The welds are considered to have strengths enough for actual applications.
Also, it was shown that the above tests and examinations were very effective to find out the faulty weld.

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In case that the nuclear power station is surrounded by the complicated terrain (e.g. mountains), the diffusion condition of effluent gas emitted from the stack is influenced by it. In order to estimate this influence, making a wind tunnel experiment with a terrain model and comparing the results with those under a flatland condition, we evaluate the effective stack height to calculate the exposure dose.
This report presents a summary of the wind tunnel experiment on stack gas diffusion for Shimane Nuclear Power Station, the estimation of exposure dose with the results, and its utilization for the emergency planning.

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The measured γ-exposure rate around nuclear power plants is due mainly to natural causes and radioactive clouds emitted from the plants. An exposure calculation method based on puff model has been already proposed to identify the plant contributions and to estimate values in response to short-term fluctuations of meteorological condition and the release rate. However, the calculation method by this model consumes a lot of computer time, since the calculation requires a three-dimen-sional integration of the distribution of the concentration from each puff. Hence, we propose a simplified method using approximate polynominal equations and interpolations. The computer time needed for the calculation with the simplified method is reduced to 1/30 of that required by the previous method. The calculation results by simplified method are compared with those by the previous method and with the measured exposure rate less natural background. The results of two different methods are in good agreement. The calculated exposure rate is within the range from half to twice as much as the measured exposure rate less background.

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