An analytical method is proposed for polarographic determination of uranium (VI) in uranium dioxide samples.
A sample weighing 100 to 400mg is dissolved in 2ml of the strong phosphoric acid by heating at 200°C for 10 min. After cooling, the solution is diluted to 10ml with water and subjected to polarography.
The maximum wave of uranium (VI) is suppressed by the presence of uranium (IV). The latter does not interfere with the determination of the, former. The wave height of uranium (VI) is affected by the concentration of the strong phosphoric acid, dissolved oxygen, and temperature. Precipitation of uranium (IV) phosphate depends on the concentration of the strong phosphoric acid in final solution.
By this method, as small as 0.025% of uranium (VI) in uranium dioxide can be determined.

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Uranium rods fabricated by rolling mill having gothic passes with finish rolling at 300° and 600°C respectively, are heat treated at the temperature and for the time shown in Table 2. These rods are thermal cycled 1, 000 times between room temperature and 550°C using the thermal cycling equipment (TCE-1) described in the previous report. The cycling growth coefficient G_tN=(l-l₀)×10⁶/l/N are given in Table 3. Microphotographs of these 14 rod specimens before and after thermal cycling are shown in Plates 2 and 3, respectively. Specific gravity and Vickers hardness values of these specimens before and after thermal cycling are also shown, as well as the dilatation curves obtained.
From these cold test data alone, it is still difficult to conclude which heat treatment of uranium rod will produce the most suitable properties to be used for fuel element, and the reasons for this are also discussed.

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The ways of converting atwo-region aqueous homogeneous reactor fueled with 20% ²³⁵U enriched uranium into a ²³³U-breeder are discussed. Numerical solutions are obtained for the burn-up equations combined with a one-group criticality condition and constant total power out-put. “Batch method” and “Continuous method” are compared. In each case, time-dependent changes in the concentrations of individual isotopes, the number of uranium isotopes supplied to the core and removed from the blanket, chemical processing rate and the ratio of the power produced in the blanket to that in the core, as well as the effect of ²³³U concentration in the blanket on these quantities are discussed.
We define “breeding efficiency” in this paper, which is believed to be a more accurate measure of whether a reactor is a breeder or not than the conventional breeding ratio.

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The aseismic design of the improved Calder Hall type power reactor has been engineered jointly by the General Electric Co., Ltd. of United Kingdom and the Japan Atomic Power Co. on the basis of various design conditions and requirements described in Part 1. Every conceivable factor has been considered in the study of the solidly compact shaping of the reactor building, of the provision of firm grips by means of biological shield, and of the core and its ducts and heat exchangers, to observe the design policy upheld by the Japanese side. Sufficient safeguard against the problem of foundation sinking is embodied in the design by adopting the pneumatic caisson method for the construction of reactor building foundation.
The graphite bricks which constitute the reactor core have been geometrically modified to retain a hexagonal cross section in each. Keys and keyways are to be provided for each brick by machining, such that the bricks can be engaged with one another in a highly ingenious manner to form a circular core, which is to be sided by a steel cylinder for core reinforcement.
Thermal deformation is allowed for also in biological shield and skirt at the top of the pressure vessel; and to contend with the possible deformation arising from an earthquake, however, diaphragm plates are to be provided for the purpose of restraining such deformation. For similar purposes damper arrangements are to be provided on the gas ducts where they pass through the biological shields.
Safety-wise, an emergency shutdown mechanism, employing earthquake detectors and boron steel pellets, is going to be installed as a backup to the normal safety devices of the reactor.

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昨年12月1日開催の, IAEAアイソトープ局担当のHenry Seligman博士を囲む講演・討論会は70余名の出席者をえて盛会であった。(世話人 木村健二郎氏,山崎文男氏,座長 藤岡由夫氏)
本稿は当日通訳をつとめられた斎藤一夫氏(東大・核研)によって当日の要旨を抄訳されたものである。なお,質問事項をテキストとして当日用意したので,末尾に添えることにした。

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