The spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Limited (JNFL) located in Rokkasho, Japan, discharged small amounts of (85)Kr into the atmosphere during final tests of the plant with ...actual spent fuel from 31 March 2006 to October 2008. During this period, the gamma-ray dose rates due to discharged (85)Kr were higher than the background rates measured at the Institute for Environmental Sciences and at seven monitoring stations of the Aomori prefectural government and JNFL. The dispersion of (85)Kr was simulated by means of the fifth-generation Penn State/NCAR Mesoscale Model and the CG-MATHEW/ADPIC models (ver. 5.0) with a vertical terrain-following height coordinate. Although the simulated gamma-ray dose rates due to discharged (85)Kr agreed fairly well with measured rates, the agreement between the estimated monthly mean (85)Kr concentrations and the observed concentrations was poor. Improvement of the vertical flow of air may lead to better estimation of (85)Kr dispersion.
Greenhouses are possible places with high
222Rn concentrations, since soil, the source of
222Rn, is directly exposed inside them. To examine this point,
222Rn concentrations in 28 greenhouses at five ...locations in Aomori Prefecture were measured for approximately 1 year with passive Rn detectors. For 1 week, measurements of
222Rn concentration and working level were also carried out with active detectors to get equilibrium factors and the ratio of
222Rn concentration in working time to non-working time in selected greenhouses. The geometric mean of annual
222Rn concentrations in greenhouses was 13 Bq m
−3, and the same as that in dwellings and lower than that in indoor workplaces in the prefecture. However, variation of the
222Rn concentrations was far larger than in other environments, and ranged from the lowest level in outdoor workplaces to the highest level in indoor workplaces. Significant seasonal variation was also observed in
222Rn concentrations. The mean effective dose from
222Rn and its progenies was estimated to be 0.047 mSv year
−1 for a farmer working in a greenhouse.
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The
222Rn concentrations in indoor workplaces were measured in Aomori Prefecture, Japan, and the results are reported here. This survey was part of a program to measure background natural radiation ...dose rate in the prefecture where the first Japanese nuclear fuel cycling facilities are now under construction.
The survey of the
222Rn concentrations in indoor workplaces was carried out at 107 locations from 1996 to 1998. The
222Rn concentrations were measured for approximately one year at each site with passive Rn detectors, which used a polycarbonate film for counting α-rays and could separate concentrations of
222Rn from
220Rn. Weeklong measurements of
222Rn concentration and working level were carried out with active detectors to get the ratio of
222Rn concentration during working hours to non-working hours as well as equilibrium factors in selected locations.
Diurnal variation of
222Rn concentration depended on building structure, air-conditioning, time of day and day of the week (week days or weekend). The
222Rn concentration during working hours was generally lower than that in non-working hours. Although the annual average
222Rn concentration in indoor occupational environments was higher than that in dwellings, radiation dose for Aomori Prefecture residents from Rn in the former was 14% of the total indoor dose by Rn because of the lower concentration in working hours and lower occupancy factor.
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Seasonal radiation dose rates were measured with glass dosemeters housed in watertight cases at various depths in the water of Lake Obuchi, a brackish lake in Aomori Prefecture, Japan, during fiscal ...years 2011-2013 to assess the background external radiation dose to aquatic biota in the lake. The mean radiation dose in the surface water of the lake was found to be 27 nGy h(-1), which is almost the same as the absorption dose rate due to cosmic ray reported in the literature. Radiation dose rates decreased exponentially with water depth down to a depth of 1 m above the bottom sediment. In the water near the sediment, the dose rate increased with depth owing to the emission of γ-rays from natural radionuclides in the sediment.
The spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Limited (JNFL) located in Rokkasho, Japan, discharged small amounts of super(85)Kr into the atmosphere during final tests of the plant ...with actual spent fuel from 31 March 2006 to October 2008. During this period, the gamma-ray dose rates due to discharged super(85)Kr were higher than the background rates measured at the Institute for Environmental Sciences and at seven monitoring stations of the Aomori prefectural government and JNFL. The dispersion of super(85)Kr was simulated by means of the fifth-generation Penn State/NCAR Mesoscale Model and the CG-MATHEW/ADPIC models (ver. 5.0) with a vertical terrain-following height coordinate. Although the simulated gamma-ray dose rates due to discharged super(85)Kr agreed fairly well with measured rates, the agreement between the estimated monthly mean super(85)Kr concentrations and the observed concentrations was poor. Improvement of the vertical flow of air may lead to better estimation of super(85)Kr dispersion.
The physicochemical form of uranium ( super(238)U) in the sediment of brackish Lake Obuchi was investigated using the standard procedures of sequential extraction. Approximately 60% to 70% of ...super(238)U was composed of the form bound to carbonates and iron (Fe)-manganese (Mn) oxides in silty sediments, whereas more than 50% of super(238)U existed in the minerals of sandy sediments. The proportions of super(238)U bound to carbonates in the sediments of brackish Lake Obuchi were larger than those in fresh-water lake sediments. Most of the uranium in the brackish lake sediment was considered to be mainly influenced by UO sub(2)(CO sub(3)) sub(3) super(4-) in seawater, judging from the fact that the super(234)U/ super(238)U activity ratios (1.13 to 1.16) of silty sediments were very close to that of seawater (1.14). The high correlation found between the super(238)U concentration in the sediment and the amount of organic matter demonstrated that organic matter acts as a scavenger for super(238)U accumulation on the lake bottom.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The concentrations of super(222)Rn in greenhouses in Aomori Prefecture, Japan, were measured. The geometric mean of annual super(222)Rn concentrations in greenhouse was 13 Bq m super(-3) and the same ...as that in dwellings and lower than that in indoor workplaces in the prefecture. The arithmetic and geometric mean super(222)Rn concentrations in the greenhouses were 18 plus or minus 16 Bq m super(-3) and 13/2.3, respectively. The variation of the super(222)Rn concentrations was larger than in other environments, and ranged from the lowest level in outdoor workplaces to the highest level in indoor workplaces. It was found that the mean effective dose from super(222)Rn and its progenies was estimated to be 0.047 mSv year super(-1) for a farmer working in a greenhouse.
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Temperature dependency of radiophotoluminescence glass dosimeter sensitivity was examined by irradiation of the dosimeter elements in an artificial climate experiment chamber. Two laboratories (A and ...B) independently measured the radiation dose of the elements irradiated simultaneously. The dosimeter elements were irradiated by y-rays from a combined source of
137
Cs (3.3 MBq) and
60
Co (1.9 MBq) at four different temperature levels; -10°C, 0°C, 20°C and 30°C. Statistically significant decrease of the sensitivity at low temperature was observed by both laboratories, however, declining rates of the sensitivity with temperature were different for each. Average decrease rates were 0.047±0.025% deg"
1
and 0.091±0.033% deg"
1
for laboratories A and B, respectively. The maximum declining rate of 0.052% deg"
1
and 0.17% deg"
1
were observed by A and B, respectively. The reason for this discrepancy between the two laboratories was unknown, and further study is required to elucidate this problem.
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