JPDR is a natural circulation and direct cycle boiling water type reactor. This report covers the distinctive consideration in design and progress of construction of the JPDR Project.
Some of the topics described in this report were happened because of this project is the first nuclear power plant in Japan.
The project was started from September 1, 1960 and the final 100 hr test was successfully completed on December 9, 1963.

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Operation experience in JPDR was discussed. Stepwise sequences of plant start-up, shut-down and scram recovery were briefly stated.
Problem area in water treatment, which is important in direct cycle boiling water reactor, were pointed out. Method of routine check and maintenance of equipment were reviewed.

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JPDR start up test started Aug. 1963 and ended Dec. 1963 is explained. It is divided into Phase 0 thru V. Phase 0 is for zero power physics test, including initial critical approach, uniformity test, reactivity coefficients test, safety margin test and preparation for power up. Phase I thru V is for power up test, including nuclear calibration, optimization of rod pattern and auto. control system, test to study plant performance and capability for normal operation such as mechanical equipment test, radiation survey etc., and test to study plant performance and capability against abnormal operation such as emergency condenser operation, generator trip test, etc.
Consequently JPDR was found to operate safety and stably and its operation was fairely good and just as designed. Noted was that JPDR could be used to conduct various special tests as its nature of experimental purpose.

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Health physics coverage for JPDR was begun ior to the initial loading of the core. Radiation rveys were made over 150 points during power eration test.
Radiation levels in all warranted locations were der expected value, but in few additional locations ere exceeded.

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The Tokai Atomic Power Station is the first nuclear power station in Japan for practical use with the maximum electrical power output of 166 MW imported from the General Electric Power Co. of U.K., and is now under construction by the Japan Atomic Power Co. at Tokai-mura, Ibaraki Prefecture, with its commercial operation scheduled for commencement in April 1965. The Station is the one what is called “Advanced Calder Hall Type”, with hollow-type fuel composed of natural uranium, graphite moderated and CO₂ gas cooled reactor.

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Evidence on the high temperature and high burnup behavior of metal fuels and uranium dioxide fuel have been accumulating over the past several years. Current problems on fuel materials, cladding materials and fuel designs for proven type reactors are described and also non-metallic fuels for future power reactors are discussed.

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Safety review is made on the recent power reactor in this paper outlining about recent views of the USA and U.K. government and main safeguard devices provided for reactors in practice, together with picking up important points to be consid ered for safety.

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Pointing out the importance of standardization of plant equipment and scaling up of plant unit output, regarding to nuclear power cost potentiality, explanations are made on other details for cost reduction in the field of engineering development. Recent cost trends are also shown through illustrating published construction and power costs of large scale power reactors under operation, construction and consideration both in the United States and in the United Kingdom. Finally discussed are several problems to be involved in evaluating nuclear power costs in Japan.

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In June 1963, the Atomic Energy Commison in Japan decided and announced that nuclear power generation in this country should depends, to a significant extent, on heavy warter power reactors built with Japanese technology.
An outline of the development program and of the initial efforts spent so far is described in this short note. The reasons why the heavy water reactor has been chosen are also given.
The choice of the coolant system to be adopted will be made within a few months and an opinion on this question is briefly presented.

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A research and development project for the proposed JPDR-II is described, the main purpose of the project being the study of the high power density of a boiling water reactor. The works of the above project are being carried out by using a forced circulation system, the modified version of the present JPDR (a natural circulation, boiling water reactor).
The main items described here are high power density fuel design, physics calculations, heat transfer and fluid flow and fluid stability, and computer scheduling of the control. The average power density aimed at is about 45kW/l, and the total thermal output will be twice that of the JPDR.

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The author points out recent world trends in fast breeder development and problems raised in this connection, and in the light of these trends, states his opinion of the direction which should be taken in Japan in our own plans for developing fast breeders.

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Studies on a high temperature gas cooled reactor with semi-homogeneous fuel were started in JAERI in 1958, when this reactor concept was taken up.
Liquid bismuth as well as helium were considered as coolant. The main items of study under the JAERI program are described. An aqueous homogeneous reactor program in past several years is also reviewed. The main activities were critical experiments and analyses of a homogeneous heavy-water system, studies on behavior of a thorium oxide slurry and preliminary mock-up experiment for a boiling slurry reactor concept.

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The progress of marine reactor development is reviewed from the technical point of view, and the main features of recently developed marine reactors are outlined.
The program for developing the first nuclear ship in Japan is described, and the specifications are given of the reactor whose preliminary design has been prepared by the Japan Nuclear Ship Development Agency. It has been decided that the reactor to be installed should be the indirect cycle light water type. The basic policy is to assure safety in operation, and due consideration for incorporating domestic technology in design and construction.

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In view of an international standpoint, it could be said that development of nuclear power has so far experienced the three developmental stages; “boom”, “slow-down” and recent “gradual upward” period.
This third period may represent a so-called “dry” feature as is seen in the late world topics such as struggle between nuclear energy and coal, an unexpected lower estimate on power cost announced by the Jersey Central Electric Co. in U.S.A., or selection of a desirable reactor type in the second nuclear power program in the United Kingdom.
The author hereby tries to introduce the outline of the recent developments on nuclear power upon above-mentioned standpoint and to express his expectation for the forthcoming Third Geneva Conference.

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