A description is given on the basic concepts of hot laboratory design and operation, forming part of the results of the work carried out by the Research Committee of Hot Laboratory, Atomic Energy Society of Japan.

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For assessing the performance of power plants, a quantity called "capacity factor" (average power/nominal capacity) has been widely used. In the case of nuclear power plants, however, it is not unusual to have the nominal capacity of the plant revised, either upward or downward, which could give rise to inconvenience and confusion when this traditional method of performance assessment is employed.
It is therefore proposed to adopt for the denominator the weight of the nuclear fuel (MTU). The resulting values of MWh/MTU (annual and cumulative totals) are presented in tabulated and graphic forms for gas-cooled (GCR) and light-water (LWR) reactors, based on actual operating data from nuclear power stations in various parts of the world.
The values of MWh/MTU (annual and cumulative) provide good indicators representing the economy and reliability of a reactor, being closely related to the capacity factor, the linear power density (kW/ft), and core life (cumulative fuel burn-up (MWD/MTU) or fast neutron exposure (nvt) of core structure), and formulae for deriving these values are given.
Some observations are also presented in particular regard to GCR. The relation between output performance (MWh) and fuel weight (MTU) is presented graphically, in which areas are indicated that represent regions pertaining to proven types of reactor and other zones that remain to be covered by future improvements aimed at realizing higher output performance (MWh) with a given amount of nuclear fuel (MTU), even with proven types of GCR and LWR. This form of graphic presentation may be likened to a physiological or athletic chart, in which the distance to be run is plotted against the runner's pace.
The concept of this chart suggested itself to the author, while he was engaged in work related to the safety and start-up of the Tokai GCR in the 1960's, based on the records of corresponding work at Calder Hall and Hunterston, U.K., and the idea was gradually developed into concrete form in the 1970's with further accumulation of corresponding experience on PWR's such as Mihama, San Onofre and Zion.

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In order to analyze gas centrifuge performance, it is essential to know the concentration distribution. In the present paper the basic equation for centrifugal separation is drived from Hirschfelder's expression for binary diffusion. This two-dimensional partial differential equation can be solved very accurately by numerical computation. The velocity profile of the flows being likened to a step function, the concentration distribution and separative performance can be calculated for various types of centrifuges. This permits determination of the relation holding between such factors as cut, feed flow rate, feed point and reflux rate. Furthermore, comparisons are made between concurrent and countercurrent flows, and a discussion is presented on the characteristics of various countercurrent-those embodying circulation, as well as devoid of circulation and of reflux. These results should prove very useful for basic designs of centrifuges.

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