Considerations are presented on the wall protection of inertial confinement fusion reac-tors by means of a falling cylindrical curtain of liquid metal that is intermittently contricted into a string of closed envelopes by the action of a series of cusped fields generated around the falling liquid cylinder. The formation of a liquid metal envelope in free space is dis-cussed and the motion of the liquid curtain during constriction is numerically analyzed under the assumption of infinitesimally small curtain thickness and infinitely large conduc-tivity. The single-turn cusp-field driver coils are assumed to have a circular cross section. The calculations indicate that the energy required for the driving field is quite small com-pared with the thermonuclear energy produced per pulse, and that an adequate electro-magnetic force is generated by the coils for a 1 m radius cylindrical curtain of liquid lithium if it is constricted into closed envelopes within an interval of 30 ms.

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Neutron emission rates for irradiated BWR fuel bundles were measured and compared with calculated results. The axial thermal neutron flux distributions outside the channel box of the fuel bundles were measured by means of Au-foil activation technique and con-verted into neutron emission rate using the calculated conversion factors. The decay of neutron emission rate was also measured and the contribution of ²⁴²Cm to neutron emission was evaluated from the results. Calculations were carried out using the lattice cell burnup calculation code and two-dimensional diffusion code. Spontaneous fission and ¹⁸O(α, n)²¹Ne reaction were considered as the neutron-producing processes, and eight transuranium nuclides essential to neutron emission were taken into account. For the magnitude of neutron emis-sion rate, calculations showed reasonable agreements with measurements in view of the accuracy of nuclear data used. However, some systematic discrepancies between calcula-tions and measurements were found and these discrepancies are considered to have resulted from the biases in the calculated exposure values.

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Iodine removal tests for a BWR containment spray were carried out with large-scale JAERI Model Containment Test Facility under LOCA simulated conditions. The tests con-sisted of two groups : "gas-phase based" tests mainly to obtain the initial iodine removal rate by the spray and "liquid-phase based" tests to obtain the iodine partition coefficient at equilibrium state. It was shown that the degree of iodine removal was largely influenced by pH-value of spray water. The results were discussed with calculated results by a code MIRA-PB using a dose reduction factor for the airborne iodine.

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A correlation of a heat transfer coefficient was derived for the transition flow region between the quench front and the dispersed flow region during the reflood phase. The correlation was compared with data from a small scale reflood experiment with a 4×4 heater-rod bundle and FLECHT experiments and showed fairly good agreement with the experimental data.
The predicted errors were nearly within ±30% for all the data of the referred small scale reflood experiment, ±20% for all data except for the data of high flooding rate cases (higher than 7.5×10^-2 m/s) and the data measured at the location just below the spacer grid, and ±20% for two selected FLECHT tests.

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Local power peaking factors (LPF) in the heavy-water moderated plutonium lattices were measured by a new method of r-scanning of fuel pins using the calculated power correction factor of which accuracy was evaluated with the aid of foil activation method. Accuracy in measurement of the LPF was evaluated to be within 1%.
By this measurement, behaviors of the LPF have been made clear concerning the dif-ferences in fuel materials, coolant materials and arrangement in fuel enrichments. Depres-sion of the thermal power in the fuel cluster makes LPF in the plutonium fuel lattice larger than in the uranium lattice. This tendency is more remarkable in air coolant lattice than in H₂O coolant lattice. The value of LPF for the plutonium fuel cluster of different enrich-ments is smaller than that of a uniformly enriched fuel cluster. The reduction of LPF is smaller in H₂O coolant than in air coolant lattice.
The values of LPF by WIMS-D code based on the transport theory and by METHUSE-LAH-II code based on the diffusion theory are in agreement with the measured ones, within 1.5 and 2.4% respectively.

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Experiments in ⁸⁵Kr irradiation were conducted in a facility devised to oparate on the pressurization-dissolution principle. Unsealed ⁸⁵Kr gas amounting to 300 Ci was dissolved into 600 ml of liquid reactant-water or methanol, and the effects brought by changing the ⁸⁵Kr gas pressure and irradiation temperature on the absorbed dose rate in the liquid re-actant were examined from theoretical considerations as well as from the results of β-ray measurements made with thin plate fluoroglass dosimeter.
In the case of water reactant, the absorbed dose rate was found to be proportional to the ⁸⁵Kr gas pressure, at a general level of 103 rad/h in the range of 0.626.2 atm ⁸⁵Kr gas pressure, and to increase with lowering irradiation temperature. A similar linear relation between absorbed dose rate and ⁸⁵Kr pressure was observed for methanol reactant, but the general level was one order higher-10⁴ rad/h in the pressure range of 0.595.9 atm, whereas differences in irradiation temperature exerted hardly any influence in this case. These measured values of absorbed dose rate agreed well with the calculated values obtained by input charge method. The efficiency of radiation energy utilization was 37% for water, while with methanol it reached 65%.

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Heat flux distribution on the first wall of a fusion reactor due to the thermal radiation from high temperature protection wall placed in front of the first wall was analyzed. With necessary modifications, a three-dimensional Monte Carlo transport code developed for neu-tronics calculation was successfully applied in the analysis. That is, reasonable results with sufficiently small statistical error were obtained with reasonable computational time. The heat flux distribution was found to be insensitive to the reflection characteristic of the radiation at the first wall i. e. diffusive or specular.

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