Japanese Nuclear Power Plants Research Articles

Oxidation of nickel-base welds 182 and 82 in simulated primary water of pressurised water reactors

To date, nickel-base welds 182 and 82 used in pressurised water reactors have shown a higher susceptibility to stress corrosion cracking (SCC) during laboratory tests than in power plants. However, the increasing number of cracks reported in American, Swedish and Japanese nuclear power plants on Alloys 182/82 enlightens the need for a predictive initiation model of SCC. Initiation of SCC involves several variables interacting together such as material microstructure and composition, primary water chemistry and loading history. Building such a model requires studying each contribution of individual phenomenon, in order to have a better understanding of the mechanisms involved at a local scale in crack initiation. Before SCC initiation, some grain boundaries exposed to primary water present intergranular oxidation reaching several hundreds of nanometres. The oxide penetration kinetics could be modified by several parameters such as local metallurgy, dissolved hydrogen content of the primary water and mechanical history before oxidation. The grain boundaries affected by oxidation during a tensile test demonstrate a lower resistance to failure compared to ‘healthy’ grain boundaries. The main objective of this study is to determine key local parameters controlling grain boundary oxidation in order to calibrate an oxidation model which will be integrated to SCC initiation modelling.

Антология катастрофы на японской атомной станции Фукусима-1

Антология катастрофы на японской атомной станции Фукусима-1

A123 再処理設備に対する民間規格策定の活動について(OS2 保全・設備診断技術(1))

We have both the national technical standards and the open standards, that is, JSME codes for power generation facilities are available for the Japanese nuclear power plants in terms of the rules on design and construction, welding and fitness-for-service. They are already established, systematized and incorporated in Japanese regulations, so that they could be referred when the design or the inspections are taken place at the stage of plant construction and the inspections, evaluations and maintenance have been carried out properly during the operations. In the meanwhile, although we have the national technical standards for the nuclear fuels reprocessing facilities, the JSME codes are not available with us yet. So Japan Society of Mechanical Engineers (JSME) who had once drawn out the codes for the Japanese nuclear power plants has started to prepare the codes for nuclear fuels reprocessing facilities with those for Rules on design and construction, welding and fitness-for-service. This report deals with the current status of the codes preparations by JSME.

Anthology of disaster at Japanese nuclear power plant Fukushima-1

Anthology of disaster at Japanese nuclear power plant Fukushima-1

A1-26 原発の新規制基準の「火山評価ガイド」と適合性審査の問題点(防災と噴火史・年代,口頭発表)

A1-26 原発の新規制基準の「火山評価ガイド」と適合性審査の問題点(防災と噴火史・年代,口頭発表)

B233 フィルタベント設備の島根原子力発電所2号機への適用について(OS3 軽水炉・新型炉・原子力安全(6))

Urgent safety measures which secure power supply and cooling function and prevent flood are being implemented promptly in Shimane nuclear power station to prevent damage of nuclear reactors and the spent fuel based on Fukushima Daiichi nuclear power plant accident from tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake on March 11, 2011.In order to improve the safety of the power station furthermore, various safety measures such as enhancement of basic design facilities to prevent severe accident from happening and installation of additional facilities to prevent it from expanding are also being implemented earnestly with consideration for multiplicity and diversity of the measures to secure its safety. As for safety measures for Shimane No.2 nuclear power plant, the plan of the safety measures have been submitted to NRA as applications for Establishment Permission, Construction Permission and applications of amendments to be assessed on the basis of the New Regulation effectuated on July, 2013. The validity of the plan is now under review. This paper explains the outline of the safety measures of Shimane No.2 nuclear power plant and the design outline and current status of the installation of Filtered Containment Venting System (FCVS). FCVS is one of the important facilities of all safety measures to prevent severe accident from expanding, and it is applied to Japanese nuclear power plant for the first time.

On the Role of Poison Centers in Radiation Emergency Preparedness and Response Activities: Findings of the “Radiation Emergencies Public Health Roundtable” (Atlanta, GA—August 2012)

After the earthquake and tsunami that struck Japan on 11 March 2011, the ensuing Japanese nuclear power plant emergency renewed concerns among officials and citizens of the USA about contamination with radioactive material and the need for medical countermeasures (MCMs) to protect the public's health. The nation's poison centers (PCs), particularly those on the West Coast, received 400 calls requesting information about protective actions for contamination with radioactive material and exposure to ionizing radiation. Centers for Disease Control and Prevention (CDC) experts analyzed PC call data through the National Poison Data System (NPDS) in order to target communication messages effectively [1]. Poison centers are already used extensively by medical facilities, individual clinicians, and the general public to assess, triage, manage, and monitor known or suspected toxic exposures. Collectively, PCs receive more than four million exposure and information calls annually [2]. All calls are electronically reported to NPDS, a near real-time surveillance system maintained by the American Association of Poison Control Centers (AAPCC) and CDC. As noted by CDC speakers at a March 2010 Public Health Grand Rounds session, there is a lack of sufficient radiation subject matter expertise, as well as a lack of education and training, in this topic within the public health community [3]. These shortcomings also apply to PC staff. Calls about radiation are not as frequent as calls about other topics; therefore, PC staff may lack sufficient knowledge of such topics as ionizing radiation, the health effects of radiation exposure, contamination with radioactive materials, and appropriate MCMs to treat each type of incident. The Health Studies Branch and Radiation Studies Branch are located within CDC's National Center for Environmental Health in Atlanta, Georgia. Staff from these two branches proposed to identify and discuss the existing knowledge gaps in radiation emergency preparedness and response among PC staff by organizing an educational session for PC professionals, followed by a roundtable discussion. Organizers envisioned the roundtable as a means of initiating a continuing dialogue between PCs and other public health entities about the current and potential roles that PCs can play during a radiation public health emergency. This paper briefly summarizes the roundtable and its main findings; a full report is available online at CDC's radiation emergencies Web portal.1

Experimental and Analytical Studies on the Effect of Excessive Loading on Fatigue Crack Propagation in Piping Materials

The seismic design review guide in Japan was revised in September 2006 to address the occurrence of a large earthquake beyond the design basis. In addition, Japanese nuclear power plants (NPPs) experienced multiple large earthquakes, such as Niigata-ken Chuetsu-Oki Earthquake in 2007 and the Great East Japan Earthquake in 2011. Therefore, it is very important to assess the structural integrity of reactor piping under such a large earthquake when a crack exists in the piping. In this work, crack growth behavior after excessive loading during the large-scale earthquake were experimentally and analytically evaluated for carbon steel and austenitic stainless steel. Some cyclic loading patterns with increasing and decreasing load amplitudes and maximum loads were applied to fatigue crack growth test specimens. From the results, the retardation of crack growth rate was clearly observed after excessive loading. In addition, the applicability to the retardation effect of the modified Wheeler model was confirmed. It is also concluded that the retardation effect has little influence on the failure probability due to seismic loading using probabilistic fracture mechanics (PFM) analyses with the modified Wheeler model.

A REVIEW ON DEVELOPING INDUSTRIAL STANDARDS TO INTRODUCE DIGITAL COMPUTER APPLICATION FOR NUCLEAR I&C AND HMIT IN JAPAN

A comprehensive review on the technical standards about human factors (HF) design and software reliability maintenance for digital instrumentation and control (I&C) and human-machine interface technology (HMIT) in Japanese light water reactor nuclear power plants (NPPs) was given in this paper mainly by introducing the relevant activities at the Japan Electric Association to set up many industrial standards within the traditional framework of nuclear safety regulation in Japan. In Japan, the Fukushima Daiichi accident that occurred on March 11, 2011 has great impact on nuclear regulation and nuclear industries where concerns by the general public about safety have heightened significantly. However for the part of HF design and software reliability maintenance of digital I&C and HMIT for NPP, the author believes that the past practice of Japanese activities with the related technical standards can be successfully inherited in the future, by reinforcing the technical preparedness for the prevention and mitigation against any types of severe accident occurrence.

Twenty Years’ Operation of Low-Level Radioactive Waste Disposal and Challenges for the Next Project

Twenty Years’ Operation of Low-Level Radioactive Waste Disposal and Challenges for the Next Project Rokkasho Low-level Radioactive Waste Disposal Center (the Center) has been operating as the only commercial waste disposal site in Japan for 20 years. It receives low level radioactive waste (LLW) generated at Japanese nuclear power plants (NPPs). The planned capacity is up to 600,000 m3 (3,000,000 drums) and the Center has been already approved for 80,000 m3 (400,000 drums). The Center has been receiving more than 260,000 drums (about 52,000 m3) of waste at the end of December, 2013.

D213 配管減肉管理法の改良・実用化に向けた調査研究(3) : 予測評価の有効性と管理方法の改善(OS6 保全・設備診断技術(5))

The rule of pipe wall thinning management in Japanese nuclear power plant is decided based on the result of past pipe wall thinning behaviors and measurement data in nuclear power plants. Therefore, there are some problems to achieve more safe and reasonable pipe wall thinning management. In this paper, the effect and improvement of prediction evaluation which is one of countermeasure against such problems on pipe wall thinning management is considered.

방사능 오염식품과 방사선조사 식품에 관한 유치원 부모의 인식 - 2011년 일본 원전사고의 영향력을 중심으로 -

The purpose of this study was to examine the impact of the Fukushima nuclear power plant accident of Japan in 2011 on kindergarten parents` perception about irradiated foods and radioactive-contaminated foods. This study analysed the 178 questionnaire forms out of 205 parents of `K` and `M` kindergarten in the region of `J` city. The findings of the study indicated that the Japanese nuclear power plant accident exerted an influence on anxious of kindergarten parents about irradiated foods and radioactive-contaminated foods. In conclusion, The full-fledged publicity and parent education are required to improve the perception and understanding of kindergarten parents about irradiated foods and the differences between it and radioactive-contaminated foods.

Appropriate Responsibilities and Actions of Radiologists in Radiologic Accidents and Crises

m m m t ( t a t P m u BACKGROUND The 9/11 World Trade Center terrorist attack increased our sensitivity to potential future terrorist attacks. There are more than 100,000 abandoned radioactive sources in the world, approximately 1,000 of which are strong enough to cause harm [1]. The International Atomic Energy Agency reported that in the past decade, there have been about 300 incidents of attempted radioactive material smuggling worldwide [1], suggesting that potential terrorists will likely plan future radiologic attacks such as “dirty bombs.” Furthermore, several large-scale radiation accidents, such as the Chernobyl and Japanese nuclear power plant disasters, have had powerful immediate and long-term effects on the environment and detrimental yet uncertain long-term consequences to human health. The recent earthquake and tsunami in March 2011, and the resultant radiation leakage from the Fukushima Daiichi nuclear power plant, resulted in human cost as well as billions of dollars in the evacuation effort and abandonment of the devastated local farm industry. These current events serve as a continual reminder to the medical community of possibilities that would require a coordinated, sophisticated response. Members of the radiology community, including radiologists, nuclear medicine physicians, and technologists, have training and ongoing experience with the routine handling of radioactive materials, use of survey instruments, the appropriate containment and

D226 弁装置の不具合発生傾向の分析 : 福島原発事故の前兆を探る(OS6 保全・設備診断技術)

D226 弁装置の不具合発生傾向の分析 : 福島原発事故の前兆を探る(OS6 保全・設備診断技術)

Effect of Excessive Compressive Loading on Crack Growth Behavior

In recent years, Japanese nuclear power plants experienced multiple large earthquakes, such as Niigata-ken Chuetsu-Oki Earthquake in 2007 and the Tohoku District - off the Pacific Ocean Earthquake in 2011. Therefore, it is very important to assess the structural integrity of reactor piping under such a large earthquake when a crack exists in the piping. In this study, an effect of excessive compressive loading on the crack growth behavior of piping materials has been evaluated through cracked plate testing. It was observed that excessive compressive loading had an acceleration effect on crack growth rate. The evaluation method using J-integral to evaluate the crack growth behavior under the condition beyond small-scale yielding has been proposed for the acceleration effect of excessive compressive loading on crack growth rate. It was indicated that the acceleration effect by excessive compressive loading simulating a large earthquake could be evaluated using the proposed method.

Fukushima's reactor cores still too hot to open

Six months after the disaster that caused three meltdowns, efforts to stabilize the Japanese nuclear power plant continue.

Transport of MOX fuel: continuous challenge

Abstract For 45 years TN International has been involved in the radioactive materials transportation field. Since the beginning the spent nuclear fuel transportation has been its core business. During all these years TN International, now part of AREVA, has been able to anticipate and fulfil the needs for new transport or storage casks design to fit the nuclear industry evolutions. A whole fleet of casks able to transport all the materials of the nuclear fuel cycle has been developed. This paper focuses on the casks used to transport the fresh and used mix oxide (MOX) fuel. To transport the fresh MOX boiling water reactor and pressurised water reactors fuel, TN International has developed two designs of casks: the MX 6 and the MX 8. These casks are and have been used to transport MOX fuel for French, German, Swiss and in a near future Japanese nuclear power plants. A complete set of baskets have been developed to optimise the loading in terms of integrated dose and also of course capacity. Mixed oxide use...

Analysis of Elemental Composition of Main Construction Materials in the Nuclear Power Plant “Fugen”

Elemental data for construction materials used in nuclear power plants are necessary for the prediction of radioactivity induced by neutron irradiation. To evaluate radioactivity in retired Japanese nuclear power plants, it is preferable to use elemental data of the structural materials actually used in each plant. However, since there is no such domestic database, NUREG elemental data are commonly used for this type of evaluation. It is, therefore, required to establish a domestic elemental database of the structural materials actually used in power plants. In order to obtain elemental data, more than 130 specimens were collected from the structural materials of the Fugen Nuclear Power Plant, which was constructed in the 1970s and whose operation was stopped in 2003. Seventy-six compositional elements in the specimens were analyzed using appropriate chemical analyses and measurement techniques, such as glow discharge mass spectroscopy and inductively coupled plasma mass spectroscopy. These obtained data were compared with NUREG elemental data and other standard or reference data. As a result, it was determined that the concentrations of major elements were not so different from NUREG elemental data and other standard or reference data. On the other hand, a slight difference was seen among the concentrations and their standard deviation in the analytical data of impurities, such as cobalt. These data are expected to become a reference in the establishment of domestic standard data, and they are also expected to be applied to the evaluation of irradiation-induced radioactivity in the structural materials of reactors that are subject to decommissioning in the future.

2 原子力の現状と技術的課題

This paper describes present status of nuclear power and current technical issues based on the activities of the Japan Nuclear Energy Safety Organization (JNES) which was established on October 1 of 2003. Currently one of the major issues in Japanese nuclear power plants is seismic issue covering Niigata-Chuetsu-oki earthquake two years' ago and re-evaluation of the operating plants in compliance with the new guideline established by Nuclear Safety Commission in 2006. New inspection system has been introduced from this year. Many issues regarding safety regulation have been addressed or under investigation such as ageing, risk application, safety culture, plant uprating, sump clogging, severe accident. Present status of nuclear fuel cycle facilities such as MONJU and the reprocessing plant at Rokkasho is also explained. International activities have been promoted by the globalization and the Multinational Design Evaluation Program (MDEP) is one of them. Role of the technical support organizations (TSO) for regulatory body is attracting more importance.

ベイズ統計に基づくＢＷＲ安全系電動弁の分解点検間隔の最適化

When the maintenance program for components in a nuclear power plant is drawn up, it is important to evaluate and optimize the overhaul interval of components based on operation and maintenance experiences. Motor-operated valve (MOV) data in safety systems for BWRs are selected from the operation and maintenance database for Japanese nuclear power plants called NUClear Information Archives (NUCIA). The time dependence of the failure occurrence rate of MOV is analyzed by Baysian inference using a log-linear and regression model of nonhomogeneous Poisson process. Then, its optimal overhaul interval of MOV is evaluated based on the time-dependent failure occurrence rate as determined by Bayes analysis. This Bayes analysis is found to be effective for estimating the optimal decision for the overhaul interval of MOV in an actual nuclear plant. This analysis will also contribute to optimizing the overhaul interval of any components in a nuclear power plant by using the data in NUCIA.