著者
松村 宏 斎藤 究 石岡 純 上蓑 義朋
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.10, no.3, pp.152-162, 2011 (Released:2011-07-29)
被引用数
12 or 0

In Fukushima and neighboring prefectures, the distributions of dose rate and γ-ray count rate of radionuclides from the Fukushima Daiichi Nuclear Power Station were measured on expressways on March 15, 16, 17, and April 8, 2011, using an NaI(Tl) detector and a LaBr3 detector. A radioactive plume that contained 133Xe, 132Te, 132I, 131I, 134Cs, and 136Cs was observed at Koriyama on the afternoon of March 15. The plume arrived in the Nakadori region of Fukushima prefecture, which is surrounded by two mountain ranges, and most of the radioactivity there was deposited by rainfall. Although the distributions of 132Te, 132I, 134Cs, 136Cs, and 137Cs were similar, the distribution of 131I was different from the others. The effective nuclides for the dose rate measurement were 132Te and 132I on March 15-17 and 134Cs and 137Cs on April 8. The initial distribution profile of the dose rate on March 15-17 was retained on April 8 because the deposited radioactive material was not moved from the initial location and there was no additional effective deposition of radioactivity.
著者
古野 朗子 茅野 政道 山澤 弘実
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.5, no.3, pp.229-240, 2006-09-25 (Released:2010-01-21)
被引用数
7 or 0

This paper describes a method of estimating source term, i.e., location, period and amount of atmospheric release of radioactive material in real-time during nuclear emergency. This method consists of: (1) trial simulations of atmospheric dispersions on the possible combinations of these parameters and (2) statistical comparison of model predictions with offsite measurements of air concentrations of radionuclides and/or air dose rates from monitoring stations, to find a set of release condition providing model prediction that fits best to the measurement. A parallel execution method for efficiently processing many possible initial conditions is also developed. The performance of this method is favorably evaluated by a verification study using the dataset from European Tracer Experiment.
著者
中村 隆夫 中田 節也 岩田 吉左 小野 勤 濵﨑 史生
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.13, no.3, pp.75-86, 2014 (Released:2014-08-15)
被引用数
1 or 0

Japan is one of the countries with abundant active volcanoes and has a long history of developing countermeasures to mitigate volcanic disasters. In the field of nuclear energy, it is also necessary to assess safety against volcanic hazards, and in 2009, a voluntary guideline was published as JEAG 4625 in order to set up requirements of site assessments and basic designs of nuclear power plants (NPPs). This guideline has been revised to satisfy the requirements for examining the necessity of considering volcanic phenomena and concrete countermeasures in detailed designs of NPPs. This paper focuses on the background and technical basis of this voluntary guideline and shows the basic policy to ensure the safety of NPPs and the requirements to prevent nuclear hazards due to volcanic phenomena based on the Defense in Depth Concept.
著者
西原 健司 山岸 功 安田 健一郎 石森 健一郎 田中 究 久野 剛彦 稲田 聡 後藤 雄一
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.advpub, pp.1202060058-1202060058, 2012 (Released:2012-02-08)
被引用数
14 or 0

After the severe accident in the Fukushima-1 nuclear power plant, a large amount of contaminated stagnant water has been produced in turbine buildings and surrounding areas. This rapid communication reports the calculation of the radionuclide inventory in the core, the collection of the measured inventory in the stagnant water, and the estimation of the radionuclide release ratios from the core to the stagnant water. The present evaluation is based on data obtained before June 3, 2011. It was revealed that the release ratios of tritium, iodine and cesium were several tens of percent, while those of strontium and barium were smaller by one or two orders of magnitude. These release ratios of the Fukushima accident were equivalent to those of the TMI-2 accident.
著者
西原 健司 山岸 功 安田 健一郎 石森 健一郎 田中 究 久野 剛彦 稲田 聡 後藤 雄一
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.11, no.1, pp.13-19, 2012 (Released:2012-02-15)
被引用数
14 or 0

After the severe accident in the Fukushima-1 nuclear power plant, a large amount of contaminated stagnant water has been produced in turbine buildings and surrounding areas. This rapid communication reports the calculation of the radionuclide inventory in the core, the collection of the measured inventory in the stagnant water, and the estimation of the radionuclide release ratios from the core to the stagnant water. The present evaluation is based on data obtained before June 3, 2011. It was revealed that the release ratios of tritium, iodine and cesium were several tens of percent, while those of strontium and barium were smaller by one or two orders of magnitude. These release ratios of the Fukushima accident were equivalent to those of the TMI-2 accident.
著者
北田 淳子
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.12, no.3, pp.177-196, 2013 (Released:2013-08-15)
被引用数
3 or 0

In this study, the results of surveys conducted over the past 30 years were analyzed. The surveys include continuous opinion polls conducted by seven organizations, those conducted by eight news media one year after the Fukushima Daiichi accident, and those conducted by INSS fourteen times from 1993 to December 2011. The results were as follows: (1) Negative opinions toward nuclear power generation (NPG) suggesting “abolition or reduction”, which used to be 20-30% over the past 30 years, increased to 70% from four to six months after the accident, when there was also much news about renewable energy. (2) Even after the accident, 60% regarded NPG as “inevitable”, but many opposed future replacement or new construction of NPG facilities. (3) After the accident, recognition of the usefulness of NPG and concerns about electric power shortages in the near future remained unchanged, while anxiety and distrust toward NPG increased significantly. When considering power generation options, people now tend to focus on accident risks. (4) Nevertheless, people are neither aware of various possible problems caused by reducing NPG nor willing to accept a significant increase in electricity rate caused by the shift to renewable energy.
著者
平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.14, no.1, pp.1-11, 2015 (Released:2015-02-15)

Time histories of the I-131 concentration in air at monitoring posts in Fukushima prefecture in March 2011 were estimated using the pulse height distribution of a NaI(Tl) detector, which was opened to the public. Several corrections to the pulse height distribution were necessary owing to high count rates. The contribution to the count rates from I-131 accumulated around the monitoring post was estimated on the basis of the time history of the peak count rate by the method proposed by the authors. The concentrations of I-131 in air were converted from the peak count rates using the calculated response of the NaI(Tl) detector with egs5 for a model of a plume containing I-131 uniformly. The obtained time histories of the I-131 concentration in air at a fixed point in March 2011 were the first ones for Fukushima prefecture. The results at 3 monitoring posts, Naraha Town Shoukan, Hirono Town Futatunuma and Fukushima City Momijiyama, which can be analyzed during almost all of March, show that a plume including I-131 arrived after March 15. The results at other monitoring posts near Fukushima Daiichi Nuclear Power Station are used to characterize plume diffusion at the early period of the accident before March 15. The I-131 time-integrated concentrations in air at several monitoring posts were compared with those given in UNSCEAR 2013 ANNEX A, which were obtained using estimated time-dependent rates of release to the atmosphere. The agreement between the two results varies depending on the places compared, owing to the large uncertainties in the estimated release rate used in UNSCEAR. The results obtained in this study can be used to increase the accuracy of the time-dependent release rate estimation.
著者
大橋 弘史 佐藤 博之 國富 一彦 小川 益郎
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.13, no.1, pp.17-26, 2014 (Released:2014-02-15)
被引用数
1 or 0

A new safety concept in a high-temperature gas-cooled reactor (HTGR) was proposed to provide the most advanced nuclear reactor that exerts no harmful consequences on the people and the environment even if multiple failures in all safety systems occur. The proposed safety concept is that the consequence of the accidents is mitigated by the confinement of fission products employing not multiple physical barriers as in light water reactors, but only the cladding of fuel (i.e., the coating layers of the coated fuel particle). The progression of the events that lead to the loss or degradation of the confinement function of the coating layers (i.e., core heat up, oxidation of the coating layers, and explosion of carbon monoxide) is suppressed by only physical phenomena (i.e., the Doppler effect, thermal radiation and natural convection, formation of a protective oxide layer for coating layers of fuel, oxidation of carbon monoxide) that emerge deterministically as a cause of the events. The feasibility studies for severe events and related information revealed that the HTGR design based on this safety concept is technically feasible. This concept indicates the direction in which nuclear reactor research should be headed in terms of safety after the accident at the Fukushima Daiichi Nuclear Power Plant.
著者
土田 辰郎 木村 浩
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.10, no.2, pp.132-143, 2011 (Released:2012-03-17)

Media coverage plays an important role in delivering information to the public in a rapid and easy-to-understand manner in terms of the subjects of nuclear energy. The mass media has so far covered nuclear accidents that occurred in nuclear facilities. The media coverage usually gains the attention of the public through the news media, such as TV and newspapers. In this study, three main cases of nuclear accidents were quantitatively examined by using the database of a newspaper. In addition, various comments of journalists whom the author interviewed were added for the evaluation of the three cases. As a result, it was revealed that the amount of media reporting commonly reached a maximum just after the nuclear accidents occurred. It became also clear that the smoothness of the information flow from the nuclear industry to the mass media affected the trend of the media coverage from the viewpoints of the duration and number of news reports. Most of the journalists considered that it was significant for the nuclear industry to strengthen the initial reaction on the occasion of nuclear accidents. The nuclear industry should understand the characteristics that are typical of the media coverage on nuclear accidents in the future.
著者
平山 英夫 近藤 健次郎 海野 泰裕 松村 宏 岩瀬 広 柚木 彰 佐々木 慎一
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.advpub, 2015 (Released:2015-06-30)

A rapid and simple method to measure the concentration of 90Sr in water by measuring β-rays from 90Y was presented. Under the situation that 90Sr/90Y, 134Cs and 137Cs are the main radionuclides included in the water sample, only β-rays from 90Y can transmit through 1.5-mm-thick polyethylene. From this fact, it is possible to measure β-rays from 90Y using a β-ray detector, such as the GM-counter, set beneath the 1.5-mm-thick bottom of the water bottle containing the sample with 90Sr/90Y. The acrylic resin collimator having 0 cm, 1.00 cm, 1.50 cm or 3.00 cm diameter was made to detect β-rays at the fixed region of the GM-counter used. Contributions from bremsstrahlung produced by β-rays and γ-rays from radionuclides such as 134Cs and 137Cs/137mBa are removed by subtracting the count rate measured with a 1.00 cm acrylic resin collimator without a hole as the background count rate. The developed method was studied using the bottle routinely used at the Fukushima Daiichi Nuclear Power Station. It was confirmed that the developed method can be applied to measure the 90Sr concentration in water to the order of several Bq/cm3 if 134Cs and 137Cs concentrations are less than or equal to the 90Sr/90Y concentration.
著者
坂本 文徳 大貫 敏彦 香西 直文 五十嵐 翔祐 山崎 信哉 吉田 善行 田中 俊一
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.11, no.1, pp.1-7, 2012 (Released:2012-02-15)
被引用数
4 or 0

The environmental behavior of radioactive Cs in the fallout from the accident of the Fukushima Daiichi Nuclear Power Plant has been studied by measuring its spatial distribution on/in trees, plants, and surface soil beneath the plants using autoradiography analysis. The results of autoradiography analysis showed that radioactive Cs was distributed on the branches and leaves of trees that were present during the accident and that only a small fraction of radioactive Cs was transported to new branches and leaves grown after the accident. Radioactive Cs was present on the grass and rice stubble on the soils, but not in the soils beneath the grass and rice stubble, indicating that the radioactive Cs was deposited on the grass and the rice plant. In addition, the ratio of the radioactive Cs that penetrated into the soil layer by weathering was very small two months after the accident. These results indicate that trees and other plants are the reservoir of the fallout Cs and function to retard the fallout Cs migration with rain water.
著者
近藤 健次郎 平山 英夫 平 雅文 松村 宏 岩瀬 広 佐々木 慎一
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.advpub, 2015 (Released:2015-06-30)

Strontium-90/Y-90 are major radionuclides observed in the water samples tested recently at the site of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. A simple method of evaluating Sr-90 concentration in these water samples by measuring β rays from Y-90 with a GM-detector setup was developed. By applying the precipitation method, Sr-90 and Y-90 were separated and quantitatively collected with a filter. β rays from Y-90 in the filter were measured two times at appropriate intervals by inserting a polyethylene plate of 2 mm thickness as a β-ray absorber. The contribution of γ rays from Cs-134 and Cs-137 to the Y-90 count rates was quantitatively evaluated using a 10-mm-thick acrylic resin plate. From the parent-daughter relationship between Sr-90 and Y-90, the Sr-90 concentration was evaluated using the conversion coefficient of Y-90 count rate (cps) to Sr-90 concentration (Bq/cm3). It was verified that Sr-90 concentration of below 0.01 Bq/cm3 in water samples can be correctly measured by this simple method.
著者
渡邉 憲夫 与能本 泰介 玉置 等史 中村 武彦 丸山 結
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.12, no.2, pp.113-127, 2013 (Released:2013-05-15)
被引用数
1 or 0

On March 11, 2011, the Tohoku District-off the Pacific Ocean Earthquake and the subsequent tsunami resulted in the severe core damage at TEPCO's Fukushima Dai-ichi Nuclear Power Station Units 1-3, involving hydrogen explosions at Units 1, 3, and 4 and the large release of radioactive materials to the environment. Four independent committees were established by the Japanese government, the Diet of Japan, the Rebuild Japan Initiative Foundation, and TEPCO to investigate the accident and published their respective reports. Also, the Nuclear and Industrial Safety Agency carried out an analysis of accident causes to obtain the lessons learned from the accident and made its report public. This article reviews the reports and clarifies the differences in their positions, from the technological point of view, focusing on the accident progression and causes. Moreover, the undiscussed issues are identified to provide insights useful for the near-term regulatory activities including accident investigation by the Nuclear Regulation Authority.
著者
玉井 秀定 秋本 肇 高瀬 和之
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.11, no.1, pp.8-12, 2012 (Released:2012-02-15)
被引用数
1 or 0

The Fukushima Daiichi Nuclear Plant Unit 1 accident was investigated with the TRAC-BF1 code in order to confirm the effect of an isolation condenser (IC) on core cooling analytically. The analysis shows that the formation of two-phase natural-circulation flow is a key phenomenon for core cooling. Therefore, it is too late to cool fuel rods, once the core is heated up because of the lack of coolant. It also shows that the early start-up of the IC is essential for avoiding the core meltdown under station blackout conditions.
著者
武井 正信 小杉山 真一 毛利 智聡 片西 昌司 國富 一彦
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.5, no.2, pp.109-117, 2006 (Released:2010-01-21)
被引用数
8 or 0

Japan Atomic Energy Research Institute (JAERI) has been developing a graphite moderate and helium cooled High Temperature Gas-cooled Reactor (HTGR) with gas turbine, the GTHTR300 based on experience gained in development and operations of the High Temperature Engineering Test Reactor (HTTR) in JAERI. The GTHTR300 is a simplified and economical power plant with a high level of safety characteristics and a high plant efficiency of approximately 46%. Cost evaluation for plant construction and power generation is studied in order to clarify the economical feasibility of the GTHTR300. The construction cost is estimated to be about 200 thousands Yen/kWe. The power generation cost is estimated to be about 3.8Yen/kWh by the conditions of 90% load factor and 3% discount rate. The economical feasibility of the GTHTR300 is certified. The present study is entrusted from Ministry of Education, Culture, Sports, Science and Technology of Japan.
著者
木村 謙仁
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.12, no.2, pp.138-148, 2013 (Released:2013-05-15)

The French history of nuclear development clearly shows the inseparability of its civilian use from military use. In France, Commissariat à l'Énergie Atomique (CEA) and Électricité de France (EDF) have played an important role in research and development of nuclear technology since the postwar period. At first, the two organizations had kept great autonomy, but the government reinforced its control on them because France needed nuclear deterrence against the Soviet Union. France began using plutonium in 1952, and the Suez crisis in 1956 showed the need for nuclear force to ensure its independence. After this event, France managed the first nuclear test using plutonium in 1960. As for enriched uranium, they have long had great difficulty in securing it. The uranium enrichment technology became crucial also in civilian use in this period. EDF proposed the pressurized water reactor (PWR), which requires enriched uranium, as the future reactor type because of its economic advantage, but CEA wanted to continue developing the gas-cooled reactor (GCR) because of its independence in nuclear fuel supply. Finally, they chose PWR because a French enrichment facility was built in 1967. From such French history, we can say that the civilian and military use of nuclear technology are inseparable.
著者
三枝 博光 舟木 泰智 操上 広志 坂本 義昭 時澤 孝之
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.12, no.1, pp.1-12, 2013 (Released:2013-02-15)

Since the Fukushima Daiichi nuclear power plant accident caused by the Tohoku Region Pacific Coast Earthquake on March 11, 2011, decontamination work has been conducted in the surrounding environment within the Fukushima prefecture. Removed contaminants including soil, grass and trees are to be stored safely at temporary storage facilities for up to three years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Fourteen temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land use. In order to support the design, construction and monitoring of temporary storage facilities for removed contaminants during the full-scale decontamination within the prefecture of Fukushima, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.
著者
石川 奈緒 田上 恵子 内田 滋夫
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.8, no.4, pp.313-319, 2009 (Released:2012-02-22)

Soil-to-plant transfer factor (TF) is one of the important parameters in radiation dose assessment models for the environmental transfer of radionuclides. Since TFs are affected by several factors, including radionuclides, plant species and soil properties, development of a method for estimation of TF using some soil and plant properties would be useful. In this study, we took a statistical approach to estimating the TF of stable strontium (TFSr) from selected soil properties and element concentrations in plants, which was used as an analogue of 90Sr. We collected the plant and soil samples used for the study from 142 agricultural fields throughout Japan. We applied a multiple linear regression analysis in order to get an empirical equation to estimate TFSr. TFSr could be estimated from the Sr concentration in soil (CSrsoil) and Ca concentration in crop (CCacrop) using the following equation: log TFSr=−0.88·log CSrsoil+0.93·log CCacrop −2.53. Then, we replaced our data with Ca concentrations in crops from a food composition database compiled by the Japanese government. Finally, we predicted TFSr using Sr concentration in soil from our data and Ca concentration in crops from the database of food composition.
著者
川村 慎一 大木 俊 奈良林 直
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.advpub, 2016 (Released:2016-03-15)

Significant leakage of the primary containment vessel (PCV) occurred on March 15, 2011 at Unit 2 of Fukushima Dai-ichi Nuclear Power Station, causing land contamination over a large area. From the radiation dose rate map of Unit 2 and the temperature trend of the PCV, degradation of the PCV top head flange gasket was identified as the cause of the leakage. The design set point of the rapture disc and operability of the valves in the hardened containment venting system were further identified as factors contributing to the leakage. Based on the lessons from the leakage, the gasket material was improved to have greater heat resistance in a steam environment, the PCV cooling system was diversified to improve reliability, and the operability and operation methods of the PCV venting were improved for greater robustness of the PCV in severe accidents.
著者
藤原 了 橋本 紀彦 是永 眞理子 田宮 貴洋
出版者
一般社団法人 日本原子力学会
雑誌
日本原子力学会和文論文誌 (ISSN:13472879)
巻号頁・発行日
vol.advpub, 2015 (Released:2015-12-17)
被引用数
1 or 0

Since the 2011 Tohoku-Oki Earthquake, evaluations based on a tsunami simulation approach have had a very important role in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes. When considering tsunami disaster prevention measures based on the knowledge obtained from tsunami simulations, it is important to carefully examine the type of tsunami source model. In current tsunami simulations, there are various ways to set the tsunami source model, and a considerable difference in tsunami behavior can be expected among the tsunami source models. In this study, we carry out a tsunami simulation of the 2011 Tohoku-Oki Earthquake around Fukushima Daiichi (I) Nuclear Power Plant and Fukushima Daini (II) Nuclear Power Plant in Fukushima Prefecture, Japan, using several tsunami source models, and evaluate the difference in the tsunami behavior in the tsunami inundation process. The results show that for an incoming tsunami inundating an inland region, there are considerable relative differences in the maximum tsunami height and wave pressure. This suggests that there could be false information used in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes, depending on the tsunami source model.