Authors:H. Kimura, K. Fukuta, N. Satoh, H. Tanabe, and O. Yoshikawa
Aomori Prefectural Govemment and Japan Nuclear Fuel Limited started environmental radiation monitoring around Nuclear Fuel Cycle Facilities in April 1989. External radiation is measured by NaI(TI) scintillator and Themoluminescence dosimeter. The level of external radiation is relatively low in the winter due to snow. We have collected terrestrial samples of drinking water, soil, agricultural products and marine samples of seawater, sea sediment, seafood, etc. periodically. We have measured many radionuclides and fluoride in these samples. In soil sample,239+240Pu ratio to137Cs was almost constant at all sampling points. A correlation was observed between salinity and concentration of tritium, uranium and fluoride in lake water of Lake Obuchinuma. The correlation between137Cs and239+240Pu in lake sediment was observed in each lake.
Authors:H. Tanabe, O. Yoshikawa, H. Nakagawa, K. Fukuta, and H. Kimura
Three commercial nuclear fuel cycle facilities, a reprocessing plant, an uranium enrichment plant and a low level radioactive waste disposal center, have been constructed or are in partial operation at Rokkasho-mura in Aomori prefecture, about 700 km north of Tokyo. A monitoring program has been settled on the modulation between Japan Nuclear Fuel Ltd. (JNFL) and Aomori Prefectural Govemment. The basic goal of environmental monitoring is to make sure that the dose equivalent received by the public, living around the facilities, is much lower than the annual dose equivalent limit. The target is as follows: (1) to estimate the dose equivalent received by the public, (2) to understand the accumulation of radioactive materials in the environment and (3) to estimate the influence on the environment due to unexpected release from the nuclear facilities and to make judgement for the enforcement of routine monitoring or not. This paper describes the contents of the monitoring program such as the object of nuclides, measuring/sampling point, kinds of samples etc.
Authors:M. Tsukada, H. Yoshikawa, M. Yanaga, K. Endo, and H. Nakahara
Use of an enriched156Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the156Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added156Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.
Authors:M. Tsukada, D. Yamamoto, H. Yoshikawa, K. Endo, and H. Nakahara
Use of an enriched isotope as an activable tracer is proposed for the preconcentration of trace elements in neutron activation analysis. As a test of this method, contents of cadmium in various biological standard samples were determined by addition of an enriched116Cd tracer in the preconcentration step followed by neutron irradiation and -ray spectrometry. The principle, advantage, and limitations of the method are also discussed.
Authors:M. Imamura, H. Nagai, M. Honda, K. Kobayashi, K. Yoshida, H. Yoshikawa, and T. Kobayashi
We present a brief description of the status of our accelerator mass spectrometry system at the tandem accelerator facility of the University of Tokyo and some examples of measurements in environmental samples which have been recently performed. Fallout10Be activities have been measured, from rain samples collected monthly in Tokyo from 1975 to 1977 and from 1984 to 1986, and compared with those of7Be and137Cs. A preliminary experiment on14C measurement in volcanic gas samples is also reported.
Authors:M. Oyaidzu, A. Yoshikawa, Y. Nishikawa, K. Munakata, M. Nishikawa, and K. Okuno
The annihilation behavior of irradiation defects induced in neutron-irradiated Li2TiO3 and Li2ZrO3 were investigated with the tritium release behavior. It was revealed that the common characteristics in both samples were
that the annihilation process of irradiation defects consisted of two first-order processes and E’-center could act as tritium
trapping site, and otherwise was the way how the E’-center annihilated. The difference was suggested to attribute to the mobility
of M as M4+ (or M3+, etc.).
Authors:S. Watanabe, N. Ishioka, T. Sekine, A. Osa, M. Koizumi, H. Shimomura, K. Yoshikawa, and H. Muramatsu
Ion implantation was applied to the production of endohedral 133Xe-fullerene. Using an isotope separator, 133Xe ions were implanted into a fullerene target of C60 and C70 produced by vacuum evaporation on a Ni backing. An HPLC analysis following dissolution of the fullerene targets in o-dichlorobenzene corroborated the formation of 133Xe@C60 and 133Xe@C70, showing a strong correlation between C60/C70 and 133Xe. The observed tailing following 133Xe peaks in the elution curves suggests a possibility of the isolation of endohedral 133Xe-fullerene from empty fullerene.
Authors:Y. Saito-Kokubu, K. Yasuda, M. Magara, Y. Miyamoto, S. Sakurai, S. Usuda, H. Yamazaki, and S. Yoshikawa
In order to know the distribution of plutonium derived from the Nagasaki atomic bomb, soil samples were measured to determine
the 240Pu/239Pu isotope ratio of and concentrations of 239+240Pu and 137Cs. The 239+240Pu concentrations in soils, except for Nishiyama area, were close to the average concentration of soil collected in Japan.
In soils collected at the Nishiyama area and at the eastern area of Nagasaki Prefecture and at part of northern area in Kumamoto
Prefecture, the 240Pu/239Pu ratios were lower than the global fallout values. This suggests that plutonium from the atomic bomb was deposited in the
eastern area from the hypocenter reaching up to 100 km eastwards.