The large hardware international collaboration for fusion power has been carried out and successfully completed. The collaboration has been named as Large Coil Task (LCT) for superconducting toroidal coil under auspices of the International Energy Agency. This paper describes the overview of the task and the experimental results.
A superconducting coil system is indispensable for fusion power generation in order to confine and control plasma. However, it is technically difficult to construct such large coil system with one step. The evaluation on conductor types and materials, and the scaling-up are requested to construct a practical reactor. In order to have efficient developments, an international collaboration was undertaken in 1977.
The participants are the United States, EURATOM (represented by West Germany), Switzerland and Japan, of which US acted as the operating agent. The major part of the project has been devoted to six coils (5.5 m height, 40 t/coil) fabrication and facility (helium refrigerator etc.) construction. As the final stage of the project, the experiment have been continuously performed from January 1986 until September 1987 in the United States. All six coils, which brought from the participants, satisfied the oringinal target, 8 T field generation. In the extended condition, finally 9 T was simultaneously obtained with all the coils.

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A new principle is proposed for calculating the radiation dose rate distribution in a ship loading multiple casks containing spent nuclear fuel.
The radiation dose rate distribution around each cask is derived by means of a simple analytical expression, and the shadowing effect due to the presence of neighboring casks is taken into account by a "shadow distribution function", which gives the spatial dependence of radiation dose rate.
The method permits derivation of the dose rate distribution in much finer detail and in much shorter time than by conventional QAD code ; and this advantage is accentuated with increasing number of casks.
Trial calculation using the MANYCASK code embodying the proposed principle has proved to provide good agreement with measured values. The method promises to be usefully applicable to practical problems such as optimization of cask loading arrangement on a ship, through repeated calculations on alternative arrangements throughout the ship.

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The electrolytic regeneration of Ce⁴⁺ from Ce³⁺, which is required to achieve a high decontamination factor (DF) in this process, has been investigated. A calculating model was derived for the regenerating current required during the decontamination as a function of dissolution rate of crud, corrosion rate (R_c), current efficiency (η_e) and characteristics of decontamination loop. From the above calculation, it was found that the current was mainly governed by R_c and η_e. A condition to obtain a high DF at low R_c and high η_e has been found experimentally by use of a mixture of Ce³⁺ and Ce⁴⁺ at the ratio of Ce⁴⁺/Ce³⁺=0.10.2. The desired values to be η_e ?? 80% at above 50 A/m² was obtained under the flow rate above 300 cm/min and Ce³⁺ concentration above 10×10^-3 M at 60°C using the dual-cylindrical type cell. The current efficiency was also investigated with cells of various geometries. The present decontamination process has been proposed as a system decontamination process, which is essentially a single-step decontamination process for Cr-rich oxides.

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A batch distillation of tritiated water (10 nCi/cm³) has been performed in a packed column 1, 6 cm inner diameter × 100 cm high. Packings were Dixon rings made of SUS. Time variations of tritium activity were measured by changing vapor flow rate within the column, and then the separative performances, such as the separation factors and the separative power per unit charge, were obtained. The maximum values of the total separation factor and the separative power per unit charge were 1.45 and 2.0×10^-2, respectively. The vapor flow rate from the reboiler decreases as the batch operation proceeds, so that a simulation with a fixed stage-number, the usual case, could not sufficiently predict the experimental values. We have therefore developed a simulation procedure where the number of hypothetical stages can be changed during the batch operation in order to predict the dynamic column behavior obtained from the experiments. The simulation result with the variable stage-number agreed with the experimental one.

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In order to study the migration behavior of ¹³⁷Cs adsorbed on fine soil particles, distilled water was introduced into the unsaturated sandy soil column which filtrated the fine soil particles. From the concentrations of ¹³⁷Cs in the effluent and in the soil column, it was found that fine soil particles filtrated by the soil layer were re-suspensible at the surface of soil layer and the amount of re-suspension per unit time was in proportion to the amount of filtrated fine soil particles. Considering the filtration of fine soil particles by soil layer, the reaction between soil layer and fine soil particles on which ¹³⁷Cs is adsorbed is described by the formula ∂Q/∂t= K₁C-K₂Q at the surface of soil layer. Good agreement was obtained between the observed ¹³⁷Cs concentration in the effluent and the predicted one employing ∂Q/∂t=K₁C-K₂Q and ∂Q/∂t=K₁C as a reaction formula at the surface of soil layer and in the subsurface part of the soil layer, respectively.

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