The problem of optimal flux distribution for maximum power, in bare slab reactors with uniform external source and maximum flux constraint, is solved using optimal control for-malism for the case of one group neutron diffusion approximation. A set of optimal solu-tions, which depend on the magnitude of the external source, the upper and lower limit of the control variable and the maximum flux allowable in the reactor, is obtained. The results corresponding to a critical reactor are included here, as a particular case. A numerical example is used to illustrate the parametric dependence of the solutions.

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A simple but realistic method of active feedback control of a self-ignited tokamak reactor by major radius compression-decompression is presented, in which the thermal fusion output power and the ion temperature are envisaged as the variables that could be adopted as object of control. Error inherent in the measuring system for the controlled variable is taken into account in the analysis. Numerical calculations based on a point reactor model are performed, which indicate that the proposed method of control is capable of completely suppressing thermal runaway without involving any significant change in the major radius or in the fusion output power. Matching the reactor output to changes in load is shown also to be possible from a numerical example. The thermal stability of an igniting plasma governed by this feedback control is analyzed without prescribing any particular transport scaling. It is revealed that the control is achievable for a suitably chosen gain even with a response time lag longer than the thermal runaway time. Strong dependence of the stability on the scaling law is indicated.

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An analytical study is made of transverse edge effect on the flow characteristics and performance of a linear induction pump by taking into account both effects of a nonuniform velocity distribution across the duct width and an electrical conductivity of the side-walls installed in a fringing magnetic flux region.
Equation of fluid motion and Maxwell's equations with a thin-plate approximation are simultaneously solved using a method of successive approximation, and the effects of the side-wall's conductivity on the distributions of magnetic field and flow velocity are deter-mined. Pump performances such as mechanical and electrical powers, conversion efficiency and head-flow curves are also obtained.
It is clearly shown that the secondary current in the fluid and hence the pump per-formance are significantly influenced by the side-wall's conductivity. It is also shown that the nonuniformity of the velocity distribution causes a reduction in the equivalent conduc-tivity of the secondary which is significant in the case of low side-wall's conductivity.

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Effects of walls on shedding vortex in developed channel flow were investigated putting a cylinder at the center of channels or on a wall for the value of w/d from 2 to 4. Results were compared with the uniform flow result.
When a cylinder was put at the center of the channels, non-dimensional frequency plotted against Reynolds number agreed with the uniform flow result at low Reynolds number. However, it increased rapidly with Reynolds number, then it lay considerably above the uniform flow results at high Reynolds number. When a cylinder was put on a wall, non-dimensional frequency was considerably lower than the uniform flow result in the cases of w/d=3 and 4. In the case of w/d=2, however, frequency was higher than the uniform flow result at high Reynolds number. In all cases in the present study, the transition Reynolds number increased with decrease in the value of w/d.
These results indicate that the increase in shedding frequency was due to the shift in velocity distribution from Poiseuille parabora in the wake region, which obviously increased with Reynolds number and with decrease in channel width.

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This study was made for clarification of the pyrohydrolysis behaviors of UF₄ and UO₂F₂. The progress of the reaction was measured by titrating the amount of produced hydrogen fluoride. When nitrogen was used as carrier gas of water, the pyrohydrolysis of UF₄ pro-ceeded at the temperatures of 350400°C, and UO_2+x (x ?? 0.3) was formed; the value of x decreased with the decrease of oxygen dissolved in the water. In the case of oxygen car-rier gas, the pyrohydrolysis of UF₄ formed U₃O₈-UO₂F₂ mixture as the reaction product in the above temperature region and the reaction was markedly retarded in the course because of lower rate in the pyrohydrolysis of UO₂F₂. The pyrohydrolysis of UO₂F₂ proceeded at a little higher temperature of 450500°C in both cases of nitrogen and oxygen carrier gas and α-UO₃ was formed.

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In order to measure the hydrogen permeation rate through V with atomically cleaned surface, an Ar ion sputtering apparatus has been installed in the hydrogen permeability measuring system. The permeation rate of the initial specimen was found to be increased by about one order of magnitude after Ar ion sputtering of its upstream side surface. Repeating of such a sputter-cleaning was not so much effective in increasing the steady state permeation rate as the initial sputtering was, but it accelerated the transient response rate by a factor of 2 or 3. The transient response rate was also accelerated by the increase of hydrogen pressure, but this effect tended to be diminished by the sputter-cleaning of specimen surface. The surface impurity layer on the downstream side of specimen was also inferred to act as a diffusion barrier affecting the steady state permeation rate. The present value of activation energy for hydrogen permeation through V at temperatures below 873 K was the smallest one ever obtained, showing that the surface effect was minimized in the present study on account of the surface sputter-cleaning in addition to the ultra high vacuum system.

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The effects of crud diameter on radioactive corrosion product buildup in the primary cooling pipes of boiling water reactors were evaluated and the following conclusions were obtained :
(1) The crud diameter affected the radioactivity buildup through two processes, i.e. deposition of crud on the fuel surfaces and adsorption of ionic cobalt on the fuel deposited crud. The contribution of the adsorption process to the radioactivity buildup for the plant where the average crud diameter was in the range of 110 μm was as large as that of the deposition process.
(2) As the result of numerical calculations by a radioactive corrosion product transport model, it was demonstrated that the shutdown dose rate was reduced by the suppres-sion of crud concentration in the primary coolant when the crud diameter remained constant, and it was reduced by the increase of the average crud diameter when the crud concentration remained constant.

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A dual temperature hydrogen isotopic exchange reaction system between water and hydrogen gas is numerically analyzed. The system has two features; high efficiency of isotope exchange reaction and operation under atmospheric pressure. To achieve them, the low temperature section of the system is composed of water mist and hydrogen gas co-current reactor units. For the high temperature section, a multistage-type reactor, in which a bubble plate, superheater and catalyst bed are alternatively arranged, is applied.
From a material balance between these reactors, enrichment and decontamination factors for the system are expressed as functions of seven parameters : unit number of the low temperature co-current reactor (X) ; stage number of the high temperature section (Y) ; flow ratio of tritium enriched water to decontaminated water (P/W), flow ratio of feed water to hydrogen gas (F/G) ; reaction temperatures of the low and high temperature sec-tions (T_c, T_h) ; and bubble plate temperature (T_b). Numerical calculations show that enrich-ment factor depends remarkably on F/G and T_b as well as X and Y.
In order to understand the separation characteristics visually, the McCabe-Thiele diagrams for the present system are drawn and compared with the results calculated.

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