In the past few years, great interest has been aroused in the HTGR from the viewpoint of effective use of nuclear energy as well as alleviation of environmental problems in Japan. This article outlines the coated particle fuels for the HTGR, and reviews the current reseach status of the relation between the properties and irradiation behavior of the coated fuel particles.

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The Research Committee on Criticality Safety of Nuclear Fuels (Apr., 1970-Mar., 1972), Atomic Energy Society of Japan, made a survey of the state of development and future prospects of the different processes constituting the nuclear fuel cycle in Japan, and on problems encountered in criticality safety. The Committee investigated the present status and problems concerning criticality safety design and control of (a) low and high-enriched uranium fuel fabrication facilities, (b) the plutonium fuel fabrication facility, and (c) the reprocessing plant. Also, the working groups in the Committee made a calculation on the criticality safety of the UO₂ powder storage facility, the ADU precipitation process, and of the dissolver of the reprocessing plant.
In keeping with the developing industrial scale of the different processes constituting the nuclear fuel cycle in Japan, it is urgently required to consider the organization of basic research in criticality safety, the training of specialists, the establishment of criteria or guide governing criticality safety, and the initiation of a data center and or an experimental facility.

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Many studies undertaken in the past have pointed toward the possibility and advantages of the use of the ground for the ultimate disposal of radioactive wastes, the requirement governing the conditions for the disposal site, and the evaluation of safety factors. This paper deals with a method for selecting systematically the optimum locations for the disposal of radioactive wastes with the aid of a computer, based on certain reasonable assumptions and on the experimental data required in estimating the radiological hazards in the human body caused by the disposed wastes in a nuclear facility along a coast. The calculation was made on a model nuclear facility selected to show the general method of selection of a ground disposal site.
The optimum condition for the ground disposal site is defined as that which causes minimum internal dose caused by the disposed wastes. Four locations, that were estimated to result locally in minimum internal dose to the public, were selected on the assumption of 0.1 Ci/yr leak of ⁹⁰Sr. Among the four locations, that which would expose the public to the smallest internal dose was estimated to be lower than 10^-80 mrem/yr. The method of selection of the optimum locations is concluded to be reasonably promising for the solution of prsent preoblems of the site selection for a ground disposal site.
A point-rating chart is proposed for rapid comparison of the safety of sites by evaluating each location with reference to eighteen factors. The use of this point-rating chart is explained.

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