[en] Electron spin resonance (ESR) studies have been made of lithium metatitanate (Li₂TiO₃) ceramics irradiated by γ-rays of ⁶⁰Co source at ambient and liquid nitrogen temperatures (LNT). The ESR spectra have been found strongly dependent on irradiation dose and temperature. The radiation defects induced by γ-irradiation at LNT were found to disappear almost completely by heating up to 225 K. In contrast to this, the radiation defects produced by irradiation at ambient temperature showed tolerance of elevated temperatures recovering at about 600 K

[en] The heat capacity of Li₂O₂ was measured by adiabatic scanning calorimetry from 301 to 566 K resulting in Csub(p)=59.665+52.123 x10^-3 T+5.0848 x 10⁵ T^-2(J/K.mol). The thermal decomposition of Li₂O₂ was studied by continuous calorimetric measurements. An endothermic decomposition was observed above 570 K. The enthalpy of the thermal decomposition was determined to be 25.8 kJ/mol. The effects of atmosphere and heating rate of the decomposition were also studied for the powder and the compact specimens. (Auth.)

[en] The release of tritium from neutron-irradiated Li₂O single crystal particles with sizes of 150 to 840 μm was measured by isothermal annealings. Time dependence of the release rate of tritium for various sizes of particles was well analyzed by a model of classical diffusion in a solid sphere. The diffusivity of tritium obtained was expressed in the temperature range from 573 to 950 K by (D_T/cm².s^-1) = 0.116 exp(-(101 ± 2) x 10³ J/RT). (orig.)

[en] Lithium oxide (Li₂O) pellets with various bulk densities (71, 80, 85 and 88% T.D.) were used as specimens. After the irradiation up to 2 x 10¹⁷-2 x 10¹⁹ n cm^-2 with thermal neutrons in JRR-4 and JRR-2, helium release from the Li₂O specimens during a constant heating rate was continuously measured by a quadruple mass spectrometer. In the helium release curves during a constant heating of 2 K min^-1, four kinds of peaks were observed. They are divided into two groups. One group was relatively wide peaks, of which the peak temperature range is 850-1100 K, appeared for all specimens. Another was a narrow and a very wide peaks, of which the peak temperature is around 1330 K, was remarkably observed only for the specimens with bulk density higher than 85% T.D. From the activation energy of the peaks and the neutron fluence dependencies of the temperatures of the peaks, the former group is considered to be attributed to the helium released through the processes of bulk diffusion, grain boundary diffusion without trapping at closed pores in the grains. On the other hand, from the bulk density dependence of the appearance of the peaks, the latter is considered to be attributed to the helium release with trapping at closed pores in the grains. (orig.)

[en] The Vickers microhardness of Li₂O pellets was measured at room temperature before and after neutron irradiation. The hardness number increases from 180-190 for the specimen irradiated to 1x10¹⁵ neutrons/cm² and to 220 for that irradiated to 5x10¹⁷ neutrons/cm². The recovery of the hardness was studied for the specimens irradiated to 1x10¹⁸ and 1x10¹⁹ neutrons/cm² in the temperature range 200-600⁰ C by the post irradiation annealing method. No change in the microstructure of Li₂O pellets was observed after irradiation. (Auth.)

[en] Based on the constant rate heating method, a study of tritium release from neutron irradiated Li₂O has been performed for sintered pellets and single crystals. About 8% of the tritiated species were released in gaseous forms and the other was the release of condensible forms, both from sintered pellets (86% TD) and from single crystals. The rate limiting process of the released in condensible species from the sintered pellets was inferred to be due to the desorption mechanism. The apparent activation energies of the tritium release were determined from the maximum release temperatures of the release curves. The neutron fluence and flux effects on the tritium release were also examined. (orig.)

[en] Lithium oxide (Li₂O) has been selected as a solid state blanket breeding material in a conceptional design of a controlled thermonuclear reactor (CTR) in JAERI. In this connection, reliable thermodynamic data for Li₂O would be helpful for the prediction of the blanket performance in CTR. In this light, the heat capacity of Li₂O was measured over the temperature range of 306 to 1073 K. Although two previous determinations of the heat capacity of Li₂O above room temperature have been reported, based on the drop calorimeteric method, the data presented here are to add further support to the reliability of Li₂O heat capacity data. (Auth.)

[en] Lithium oxide (Li₂O) single crystals with various sizes (0.15-5 mm) were used as specimens. After the irradiation in JRR-4 and JRR-2 (thermal neutron fluence: 2 x 10¹⁷-2 x 10¹⁹ n/cm²), and fast neutrons in FFTF (fast neutron fluence: 4 x 10²² n/cm²), helium release from the Li₂O specimens during the heating at a constant heating rate was continuously measured with a quadrupole mass spectrometer. The helium release curves from JRR-4 and JRR-2 specimens have only one broad peak each. From the dependence of the peak temperature on the neutron fluence and the crystal diameter, and the comparison with the results of sintered pellets, it is concluded that the helium generated in the crystal is released through the processes of bulk diffusion with trapping by irradiation defects such as some defect clusters. For the helium release from FFTF specimens, two broad peaks were observed in the release curves. It is considered that two different migration paths exist for helium migration in the specimen, that is, bulk diffusion and diffusion through the microcracks formed due to the heavy irradiation. (orig.)

[en] In situ electrical conductivity measurements under reactor and gamma-ray irradiation were carried out for Al₂O₃ and MgO specimens using JRR-3 and a ⁶⁰Co gamma-ray irradiation facility at JAERI. The specimens were irradiated in the temperature range 573 to 723 K for two cycles (about 0.2 dpa) with an applied DC electric field of 100 V/mm. The conductivity level evaluated after the shutdown of the reactor was substantially smaller than those during the reactor operation. Thus, it was considered that radiation induced electrical degradation (RIED) did not occur or was a negligibly small level, up to 0.2 dpa for Al₂O₃ and MgO specimens. The conductivity of the Al₂O₃ specimen evaluated at various reactor powers in JRR-3 was consistent with that measured under the ⁶⁰Co gamma-ray irradiation and was in fairly good agreement with the other radiation induced conductivity (RIC) data of high-purity Al₂O₃. (orig.)

[en] An experimental program was conducted in collaboration with the staff at the Japan Atomic Energy Research Institute for the purpose of generating fusion pertinent thermophysical and chemical data on two ternary lithium oxides that have potential as tritium breeder materials, Li²ZrO³ and Li²TiO³. The four areas studied were: (1) fabrication, (2) thermal diffusivity/thermal conductivity, (3) compatibility with candidate structural alloys (HT-9, 316 SS, and Ni-plated 316 SS), and (4) tritium release behavior after irradiation. Where possible, the behavior of these materials was compared with lithium oxide