[in Japanese]

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[in Japanese]

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[in Japanese]

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In order to investigate the present status of oral presentation, follow-up study was conducted. Questionnaires were sent to 503 authors who had oral presentation at the 1984 Annual Meeting of the Atomic Energy Society of Japan. Since another study was conducted in 1969, comparing the results of the studies, characteristics of publication of oral presentation were summarized.
About 70% of oral presentations were published. This is similar to that of the previous study. The variety of journals has increased. Also the authors who contributed overseas has increased by twice as much.

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A heating, ventilating and air conditioning (HVAC) system is installed on the operation floor of a BWR reactor building for temperature control and dust protection in work areas. In the current HVAC system, it is necessary to ensure that its exhaust ducts do not interfere with other structures and pipes, since pipings are buried under the floor.
In this study, air velocity and temperature distributions and heat removal rate were analytically and experimentally investigated, and duct arrangements without the buried exhaust ducts were evaluated. In the analysis, a three-dimensional thermal hydraulic analysis computer program for incompressible viscous fluid was applied, and a laminar flow model and slip condition on the wall surface were used, based on a comparison of calculated results with measured ones. In the experiments, a one-twentieth scale model was used, and the temperature distribution was measured by thermocouples. Furthermore an airflow distribution was visualized and three-dimensional flow path lines were obtained by computer-aided image processing. The proposed HVAC system uses a rising current of air on the hotter surface of the reactor refueling pool and spent fuel pool, and exhausts air through exhaust ducts on the ceiling. Consequently, it is confirmed that the new HVAC system can be realized, which increases the removal heat capability on condition of the same ventilation rate as the current system.

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An automatic analysis system with high sensitivity has been developed to monitor radioactive strontium in nuclear power plants and their environs.
Strontium is separated from samples by forming a complex with ethylenediaminetetraacetic acid (EDTA), and then using liquid chromatography. The separated species are fed into a flow cell for measurement of β-rays by plastic scintillator slabs for which the design was optimized in terms of sensitivity. The lowest analysis limit of this system is 10^-3 pCi/ml of strontium (⁸⁹Sr, ⁹⁰Sr).
Performance tests with practical samples of reactor coolant water, off gas filter, cereals and raw milk show that this system is applicable to current analysis of radioactive strontium.

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The velocity and temperature distributions are measured for natural convection in a horizontal concentric annulus at high Rayleigh numbers with using a hot-wire anemometer and a thermocouple. Dealing with these data statistically, the average velocity and temperature profiles as well as their turbulence quantities are obtained. By carrying out the spectrum analysis of these velocity fluctuations, a transition from the laminar natural convection to the turbulent one is clarified. With increasing Rayleigh number, the stable flow pattern becomes unstable to a periodic one. The periodicity diminishes when the Rayleigh number is further increased. A comparison of these experimental data with the time-dependent three-dimensional numerical results, which were reported in our previous paper, shows a good agreement.

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Low cycle fatigue tests of isotropic fine-grained graphite IG-11 were performed at the stress combination of pull-pull, pull-push and push-push. The best fit S-N curves obtained by several statistic analysis methods, were compared and the effect of stress ratio and specimen size on fatigue strength were discussed. Following conclusions were obtained:
(1) The best fit S-N curves obtained by Price's method showed comparatively better in data fitting than the other methods.
(2) The fatigue strength decreased as decrease of stress ratio R. The drastic decrease of fatigue strength was observed in the case of R=-3.5. This is because that the effect of pre-compressive stress in first fatigue cycle induced the decrease of tensile strength.
(3) The effect of specimen size on fatigue strength in the case of R=+∞ and compressive strength were observed.
(4) The mechanism of fatigue in graphite was well understood assuming that fatigue fracture were occurred when the stress intensity reach to the fracture toughness value in the process of crack extension.

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