No abstract available

No abstract available

No abstract available

[en] Evaluation of annual average of radionuclide concentration in surface air obtained from atmospheric dispersion factor is intended to determine a public dose as a primary source for the safety analysis of nuclear facilities in normal operation. Oarai Research and Development Center (ORDC) of the Japan Atomic Energy Agency have used fixed 5-year meteorological statistics for derivation of atmospheric dispersion factors as average conditions. To show that the meteorological statistics for any 5-year period could be used as representative data for evaluation of average conditions, annual average (1-year average) and 5-year average of evaluated radionuclide concentrations derived from the meteorological data observed over a 20-year period (1991-2010) at ORDC were analyzed. Fluctuations of evaluated radionuclide concentrations of any 5-year averages were smaller than those of 1-year averages. Further, any 5-year averages were sufficiently convergent to 20-year average. Because any 5-year averages contained no rejections by the F-test (5% significance level), they were not statistically different to the rest of 20 years data set, instead that some of 1-year averages could be rejected. It means that any 5-year averages of radionuclide concentration evaluations are well representative for the safety analysis of normal operation of the nuclear facilities in ORDC. (author)

[en] The purpose of this study is to develop a quick method for estimation of ¹³¹I concentrations in the air using data measured by monitoring posts. In this method, ¹³¹I concentrations were estimated by multiplying ¹³¹I count rates at the full-energy peak measured with NaI (Tl) detector by concentration conversion factor. The concentration conversion factor for monitoring posts in JAEA Oarai Center was calculated with EGS5 monte Carlo code. As a result, concentration conversion factor for infinite-air-source was 25.7 Bq/m³/cps. (author)

[en] The purpose of this study is to improve a quick method for estimation of "1"3"1I concentrations in the air using data measured by monitoring posts in case that a nuclear disaster occurs. In this method, "1"3"1I concentrations were estimated by multiplying "1"3"1I count rates of cloud-shine measured with Na(Tl) detector by concentration conversion factor. A previous study suggested that it was difficult to determine passing-through time of plume from temporal change of "1"3"1I count rates or dose rate. Our study applies the method for estimating passing-through time of plume from temporal change of noble gas counts. The "1"3"1I concentrations in the air at Oarai center, Japan Atomic Energy Agency resulting from the accident at the Fukushima Daiichi Nuclear Power Station were estimated by proposal technique. The result of comparison of this method with sampling method for "1"3"1I concentrations in the air were within factor 3. (author)

[en] This report presents the results of emergency radiation monitoring, including ambient gamma-ray dose rate, atmospheric radioactivity, meteorological observation and estimation of internal exposure resulting from the accident at the Fukushima daiichi nuclear power plant triggered by the earthquake off the pacific coast of Tohoku on 11th March 2011, conducted by Oarai Research and Development Center (ORDC), Japan Atomic Energy Agency (JAEA) from March to May, 2011. ORDC is located in the central part of Ibaraki prefecture and approximately 130km southwest of the Fukushima daiichi nuclear power plant. From around 15th to 21st March, 2011, the ambient gamma-ray dose rate increased and many radioactive nuclides were detected in the atmosphere. (author)

[en] The Nuclear Fuel Cycle Engineering Laboratories conducts environmental radiation monitoring around the reprocessing plant in accordance with the 'Safety Regulations for Reprocessing Plant of JAEA, Part IV: Environmental Monitoring'. This report summarizes the results of environmental radiation monitoring conducted during the period from April 2022 to March 2023 and the results of dose calculations for the surrounding public due to the release of radioactive materials into the atmosphere and ocean. In the results of the above environmental radiation monitoring, many items were affected by radioactive materials emitted from the accident at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company, Incorporated (changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016), which occurred in March 2011. Also included as appendices are an overview of the environmental monitoring plan, an overview of measurement methods, measurement results and their changes over time, meteorological statistics results, radioactive waste release status, and an evaluation of the data which deviated of the normal range. (author)

[en] New regulatory requirements were developed taking into account the lessons-learnt from the accident at Fukushima Daiichi Nuclear Power Station on March 2011. The new regulatory standards required that monitoring posts should be diversified in transmission systems and equipped with backup power supply equipment for design basis accidents. In this report, we look back on the history of monitoring posts in Oarai Research and Development Institute, explained the application for the permission of reactor installment license, application for approval of the design and construction method, pre-use operator's inspection and improvement design of monitoring posts. This report also includes about inspection based on act on special measures concerning nuclear emergency preparedness and the installation of KURAMA-II, which was carried out in conjunction with the improvement of monitoring post for new regulatory standards. As an appendix, application document for approval of the design and construction method are included. (author)

[en] Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2022. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations. (author)