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Journal Articles

Development of dose estimation system integrating sediment model for recycling radiocesium-contaminated soil to coastal reclamation

Miwa, Kazuji; Takeda, Seiji; Iimoto, Takeshi*

Radiation Protection Dosimetry, 184(3-4), p.372 - 375, 2019/10

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The Ministry of the Environment has indicated the policy of recycling the contaminated soil generated by decontamination activity after the Fukushima accident. By recycling to coastal reclamation which is one of effective recycling application, dissolved radiocesium and absorbed radiocesium on soil particles will flow out to the ocean by construction, therefore evaluating radiocesium transition in ocean considering the both types of radiocesium is important for safety assessment. In this study, the radiocesium outflow during constructing and after constructing is modeled, and radiocesium transition in ocean is evaluated by Sediment model suggested in OECD/NEA. The adaptability of sediment model is confirmed by reproducing evaluation of the coastal area of Fukushima. We incorporate the sediment model to PASCLR2 code system to evaluate the doses from radiocesium in ocean.

Journal Articles

Development of a short-term emergency assessment system of the marine environmental radioactivity around Japan

Kobayashi, Takuya; Kawamura, Hideyuki; Fujii, Katsuji*; Kamidaira, Yuki

Journal of Nuclear Science and Technology, 54(5), p.609 - 616, 2017/05

 Times Cited Count:7 Percentile:70.7(Nuclear Science & Technology)

The Japan Atomic Energy Agency has, for many years, been developing a radionuclide dispersion model for the ocean, and has validated the model through application in many sea areas using oceanic flow fields calculated by the ocean model. The Fukushima Dai-ichi Nuclear Power Station accident caused marine pollution by artificial radioactive materials to the North Pacific, especially to coastal waters northeast of mainland Japan. In order to investigate the migration of radionuclides in the ocean caused by this severe accident, studies using marine dispersion simulations have been carried out by JAEA. Based on these as well as the previous studies, JAEA has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide concentration around Japan in case of a nuclear accident.

Journal Articles

Numerical simulations of short-term migration processes of dissolved Cesium-137 due to a hypothetical accident of a nuclear submarine in the Japan Sea

Kobayashi, Takuya; Chino, Masamichi; Togawa, Orihiko

Journal of Nuclear Science and Technology, 43(5), p.569 - 575, 2006/05

 Times Cited Count:3 Percentile:25.6(Nuclear Science & Technology)

A dissolved radionuclide migration code system that consists of a ocean circulation model, Princeton Ocean Model, and a particle random-walk model, SEA-GEARN, has been developed. The oceanic migration of $$^{137}$$Cs discharged from a nuclear submarine in a hypothetical accident at the Tsushima Strait was calculated in the southwestern area of the Japan Sea as a model application. The calculations for instantaneous releases every 10 days were carried out for one year to study the seasonal differences of migration process of the dissolved radionuclides. The migration tendencies of dissolved radionuclides were divided into two patterns. For the releases started from January to September, all of the high concentration areas migrated to the northeast along the coastline of the Main Island of Japan from the release point. As for the releases from October to December, some high concentrations areas migrated to the west from the release point and the concentrations of $$^{137}$$Cs along the coastline of the Main Island of Japan were comparatively low.

Journal Articles

Development of ocean pollution prediction system for Shimokita region; Model development and verification

Kobayashi, Takuya; Lee, S.; Chino, Masamichi

Journal of Nuclear Science and Technology, 39(2), p.171 - 179, 2002/02

 Times Cited Count:3 Percentile:24.34(Nuclear Science & Technology)

A three-dimensional model system was developed to predict oceanic dispersions of radionuclides released into the eastern area of Shimokita Peninsula. This system is a combination of the Princeton Ocean Model (POM) for predicting ocean currents and a particle random walk model for oceanic dispersion of radionuclides. The model was verified by using measured currents, temperature and salinity at the coastal area of Shimokita, Aomori-ken, Japan, where a nuclear fuel reprocessing plant is under construction. The results obtained from simulations area as follows; (1) Wind and the Tsugaru Warm Current entering into the objective region through the Tsugaru Strait significantly affect the structure of current over the region. (2) POM can represent seasonal variations of the Tsugaru Warm Current well with hypothetical oceanographic data. The calculation succeeded to reproduce the coastal mode from winter to spring and the gyre mode from summer to autumn.

Oral presentation

Development of an emergency assessment system of the marine environmental radioactivity around Japan and its utilization

Kobayashi, Takuya; Kawamura, Hideyuki; Fujii, Katsuji*; Kamidaira, Yuki

no journal, , 

The Fukushima Dai-ichi Nuclear Power Station (FNPS1) accident in Japan in March 2011 led to the release of large amounts of radionuclides into the atmosphere as well as direct discharges into the ocean. Various environmental assessments have been performed by many research groups using marine dispersion simulations after the FNPS1 accident. It was recognized from these woks that the risk of radionuclide release from nuclear facilities to the environment was very high and the establishment of emergency ocean dispersion forecasting systems was necessary. Then, the Japan Atomic Energy Agency (JAEA) has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide migration for a nuclear accident in ocean around Japan, by integrating previous study results. In this study, structure, performance test results, and utilization of the system are described.

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