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- Author or Editor: T. Imanaka x
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Abstract
Radiocesium concentrations in cow's milk from two producing districts in Japan were measured monthly for three years following the Chernobyl accident. The Chernobyl contribution in137Cs concentration was evaluated from the134Cs concentration and the137Cs/134Cs ratio. The highest137Cs concentration of 0.6 Bq l–1 was observed in May 1986 and the Chernobyl contribution has decreased during three years to levels corresponding to the contribution from past nuclear weapons fallout. Annual values of child internal dose through milk consumption were estimated at 0.6, 0.3 and 0.1 
Sv for the first, the second and the third year following the accident, respectively.
Abstract
Field measurements of radioactivity were performed in highly contaminated areas around Chernobyl in the summer of 1990. Six radionuclides including the most dominant137Cs have been identified in soil samples through 
-ray spectrometry. The relation between the -ray dose rate above the ground and the radioactivity density in soils has been investigated. The external dose from deposited radiocesium for the period of 70 years after the deposition has been evaluated to be about 5 mSv per 1 and 0.5 Ci km–2 of137Cs and134Cs deposition, respectively.
Abstract
To estimate fast neutron fluence released by the JCO criticality accident in Tokai-mura, 54Mn, which is produced by the 54Fe(n,p)54Mn reaction, was determined in soil samples by ultra low background g-ray spectrometry after radiochemical separation. Activities of 54Mn, using 30-200 g soil samples were detected in soil samples from 13 points in all directions within a 20 m zone from the precipitation vessel we have used. The levels of 54Mn ranged from 0.015 to 2.12 mBq/g soil. By using these data and MCNP, the fast neutron fluences were estimated.
Abstract
To estimate the dietary intakes of 210Pb and 210Po for the Japanese adults and their annual effective doses, 210Pb and 210Po were measured for 240 daily diet samples collected at two locations of Ishikawa Prefecture in Japan over three years by duplicate portion studies. No appreciable differences in intake rates of 210Pb and 210Po and their 210Po/210Pb ratios were seen among the years in each district, and between the two districts. The intake rates evaluated using 240 diet samples were 0.20 Bq/d/p for 210Pb and 0.61 Bq/d/p for 210Po as a median, respectively. Annual effective doses of 210Pb and 210Po for Japanese adults were estimated to be 0.050 and 0.053 mSv/y, respectively.
Abstract
Long-lived chlorine, 36Cl (T1/2 = 301,000 y) in environmental samples has been measured by the AMS system installed in Tandem Accelerator Center, University of Tsukuba. A tri-carbon-molecular 12C3 - pilot beam method is used to stabilize the terminal voltage of the tandem. A small amount of pure carbon graphite is well mixed into a AgCl target material for creating Cl- and 12C3 - in the ion source. A 36S isobaric interference in the system is eliminated to determine 36Cl in environmental samples by chemical procedure. Some samples containing chlorine such as soil, chemical reagents and table salt have been collected in the JCO criticality accident site and analyzed to detect neutron-induced 36Cl. The experimental result has been compared with a theoretical calculation.
