The influence of a transverse magnetic field on the heat transport characteristics of a potassium heat pipe was experimentally studied in the range of field strength 00.6 T. The wick was constituted of a multilayer mesh screen, and the adiabatic section, to which the magnetic field was applied, was made up of a concentric doublewall rectangular tube, with the inner wall completely separating the vapor and liquid flows.
The magnetic field was applied perpendicularly to the heat pipe, upon which the axial temperature distribution of the heat pipe was observed to be affected, and the heat transport rate to be reduced with increasing field strength.
The effect of the magnetic field on the heat transport rate is analyzed in terms of the liquid pumping ability of the wick and of the magnetohydrodynamic (MHD) effect on the liquid flow through the wick. The MHD effect on the flow through wick is shown to be expressible by a formula similar to that for flow between parallel plates.
The heat transport rate measured in magnetic field are compared with values calculated assuming that the wick pumping ability was not influenced by the magnetic field but that it was the MHD effect on the liquid flow through the wick that affected the heat transport. The calculated results well explained the experimental data.

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In the previous paper, the authors pointed out the motion of bubble or gaseous phase in the direction to the both side walls due to the pinch effect caused by the induced magnetic field in the liquid metal two-phase flow under the strong magnetic field. In the present paper, to clarify the existence of the pinch effect experimentally, an experi-mental study was performed.
Firstly the distributions of the void fraction in the cross section perpendicular to the flow were measured at three locations in the flow direction for the various strength of the applied magnetic field. Secondly a magnetic field was superposed on the induced magnetic field by the outer coil to disturb the pinch effect by the cancel of the induced magnetic field with the superposed one, resulting in the evident redistribution of the void-fraction profile obtained above.
From these experiments it is concluded that the pinch effect will play an important role to redistribute the bubble or gaseous phase in the liquid metal two-phase flow under the strong magnetic field and that the effect is more promoted with increasing magnetic interaction number defined as a ratio of the electromagnetic force to the inertia of the fluid.

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To study behaviors of zircaloy-clad fuel during loss-of-coolant accidents in PWR, simulated fuel rods having five pressure levels were heated in steam or vacuum at heating rates between 3 and 47°C/sec. The extent of ballooning of fuel rod is chiefly found within 30 mm from the center of rupture opening. The maximum diametral ex-pansion is mainly related to the burst temperature, as it decreases between about 830°C and about 920°C. The maximum diametral expansions in vacuum are larger than those in steam. The average wall thickness varied with ballooning depends on heating method and atmosphere, and is represented to be about two-third of maximum diametral expan-sion. Oxide thickness on inner surface is apparently thicker than that on outer, when amount of supplied steam to inner surface is less. The porous thicker inner oxide consists of monoclinic and tetragonal zirconia, and higher hydrogen content is closely associated with the occurrence of tetragonal zirconia.

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Uranium redox chromatographies were carried out in order to study uranium isotope separation based on chemical process. Hexavalent uranium ions were first adsorbed in the anion-exchange resin packed in a column, and eluted out by the HCl eluent contain-ing reductant TiCl3, being reduced to tetravalent ions. From the measurements of both uranium concentrations and isotope abundance ratios in the sampled effluent, the isotope separation coefficients (S = 1 + ε) and isotope equilibrium constants (K) were determined : ε = 7.3 X 10^-4, InK=9.7 X 10^-4 at 5 _M HCl and 70°C, and ε = 7.0 X 10^-4, InK = 9.5 X 10^-1 at 4 _M HCl and 87°C. Experimental errors for these values are estimated to be less than 20% of each value. The light isotope ²³⁵U is found to be enriched at the rear boundary of the uranium chromatogram, which indicates that ²³⁵U in the U(VI) state is less easily reduced to the U(VI) state than ²³⁵U.

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Removal of radioactive ions was studied from low and medium level radioactive waste solutions by electrodialysis using ion exchange membranes. The test solutions contained ¹³⁷Cs⁺, ⁹⁰Srz²⁺, ¹⁰⁶Ru³⁺ or fission products (F.P.) as active ions and NaCl, Na₂SO₄ or Ca(NO₃)₂ as inactive coexisting salts. The decontamination factor of the active ions was in the order : ¹³⁷Cs⁺ (greater than 99%) > ⁹⁰Sr²⁺ > F.P. > ¹⁰⁶Ru³⁺. The dialysis time required to attain the saturation was the shortest for monovalent cations K⁺, Cs⁺ and Na⁺, intermediate for divalent cation Sr²⁺, and the longest for trivalent cation Ru³⁺. The ratio of the decontamination factor of an active ion η_A to the desalination factor of an inactive ion η_B was nearly equal to unity for ²⁴Na, ⁴²K, ¹³⁷Cs and ⁹⁰Sr. On the other hand, the apparent selective permeability of an active ion (A⁺) against Na⁺ ion, T^A_Na++ was higher than unity for all the active ions tested, and was in the order of ¹³⁷Cs > ⁹⁰Sr > ⁴²K > ²⁴Na, where T^A_Na+ is defined by the ratio of γ_A to γ_Na+ with γ_A being the ratio of dilution of A in the diluate and γ_Na+ being that of Na⁺ in the same diluate. The decontamination factor of the active ions did not depend significantly on the species and concentrations of the coexistent salts or on the concentration of the active ions.

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High-level liquid waste (HLW) from nuclear fuel reprocessing containing platinum group elements could be denitrated effectively with formic acid, and the solution indi-cated neutral even after the addition of excess formic acid. Platinum group elements, rhodium above all, were found to decompose formic acid and the action was more effective in the decomposition of excess formic acid in HLW. When HLW did not contain platinum group elements, both of unaltered nitric and formic acids remained after addition of stoichiometric amount of formic acid, leaving the solution slightly acidic. Excess formic acid in HLW not containing platinum metals was decomposed almost completely by irradiation with ⁶⁰Co γ-rays up to 2 x 10⁸ R.

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The vapor pressure of strontium in the temperature range of 494-660°K has been determined by the mass spectrometric Knudsen effusion method. The temperature dependence of the vapor pressure in Pa is given by the equation : logP = 10.750±0.122 - (8, 427±69)/T. From the values of vapor pressure, heats of vaporization of strontium were obtained to be ΔH°_{υ, 298} = 163.8±1.6 kJ/mol by the second law treatment and ΔH°_{υ, 298} = 161.9±0.5 kJ/mol by the third law treatment.

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Two experiments were performed, which confirmed that the lithium particles pro-duced by the ¹⁰B(n, α)⁷Li reactions form etchable latent tracks in cellulose nitrate resin. The first experiment was made on a pair of resin detector plates sandwiching between them a boron-bearing layer. Upon irradiation and etching, the tracks appearing on the two plates were found to constitute matching pairs, some of which appeared to be shorter than others, suggesting their correspondence respectively to the ⁷Li and a particles generated by the ¹⁰B(n, α)⁷Li reaction. This surmise was further confirmed by a second experiment, in which the pairing of etch-pits was examined between the two faces of a film detector of thickness below the range of a but above that of ⁷Li particles. The ratio between paired and single etch-pits counted in a unit area of the two faces of film after irradiation and etching proved to be quite close to the value derived by calculation based on the assumption that 'Li as well as a particles leave etchable tracks on the resin with 100% efficiency, whereas the observed ratio distinctly differed from the correspond-ing calculation undertaken assuming that a particles alone contributed to the track for-mation.
This finding is consistent with the estimations of etchable track formability obtained by applying criteria given in three independent theoretical studies found in published literature.

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In an attempt to obtain information on survival temperature limit for TRISO parti-cles, out-of-pile heating experiment was carried out on unirradiated, unbonded particles. Catastrophic failure resulting in the formation of a hole like a volcano crater occurred during heating at 2, 2502, 300°C for 2035 min. Although the failure temperatures were lower than the melting point of the kernel material (UO₂), visual and microscopic observations of failed particles suggests kernel melting. Failure of SiC layer was detected after heating at temperatures as low as 2, 130°C. At 2, 560°C, SiC layer disappeared completely. A similar heating experiment on particles embedded in graphite matrix was carried out for the purpose of comparison. The embedded particles survived higher temperature excursion than in the case of the unbonded particles. Effects of heating on OPTAF of PyC and on crushing strength of particles are also reported.

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A method is introduced to evaluate the degree of nuclear technology transfer ; that is, the output powers of Japanese nuclear reactors constructed in these 20 years are chronologically plotted in a semi-log figure. All reactors plotted are classified into im-ported and domestic ones according to a value of domestication factor. A space between two historical trajectories of reactor construction may be interpreted as one of the meas-ures indicating the degree of nuclear technology transfer. In connection with this method, historical change of educational and training courses in Nuclear Engineering School of Japan Atomic Energy Research Institute is reviewed in this report.

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