Development of a quantitative resilience model for nuclear power plants

Prolonged impact of the Fukushima Nuclear Power Plant Accident on health and society Naomi Ito, Research Assistant at the Fukushima Medical University, tells us how the 2011 Fukushima Daiichi Nuclear Power Plant Accident impacted and continues to impact local residents. The health effects on local residents following a nuclear power plant accident are diverse, not only because of radiation exposure but also because of changes in lifestyle and social environment. It has also been indicated that various environmental changes that could emerge during the restoration process may affect residents in various ways over a long time. On March 11, 2011, the Great East Japan Earthquake struck Japan with a magnitude of 9.0. Within an hour, a tsunami hit the shore. Three reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP, operated by Tokyo Electric Power Company) lost power. The reactors could not be cooled, and core meltdowns occurred, which resulted in an explosion due to hydrogen being generated at high temperatures. As a result, radioactive materials were released and scattered northwest from the power plant.

Emergency evacuation time model of nuclear power plant pedestrians

Divided fates of victims after the Fukushima nuclear power plant accident

Karimunjawa islands are located in the middle of the Java Sea, approximately 83 km northwest of Jepara city. These islands have become an Indonesian marine tourism destination and since 2001 had been designated as a national park. The Indonesian government has chosen Muria peninsula in the district of Jepara, Indonesia as a site for a potential nuclear power plant (NPP). The purpose of this study was to determine the current level of radiocesium (137Cs) activity and forecast its spread if an NPP is operated at Jepara. To determine the distribution of 137Cs in Karimunjawa waters, a sampling of water was done in six stations. Simulation modeling was used to map the distribution of 137Cs should an NPP be constructed in Jepara. The results showed that 137Cs activity in Karimunjawa waters ranges from 0.12 to 0.39 mBq.L-1 with an average of 0.24 mBq.L-1. This value is slightly higher than previous studies in the coastal waters of Gresik, which had an average activity of 0.200 mBq.L-1 because the waters around Karimunjawa have a lower dilution rate than the coastal waters of Gresik. However, these values were considerably lower than those in the waters of Northeast Japan before the Fukushima nuclear power plant accident which registered 137Cs activity at 2-3 mBq.L-1.This indicates that 137Cs in Karimunjawa is not entirely from Fukushima rather from the global fallout. The 137Cs distribution model suggests that after 15 days, a leakage in the Muria Peninsula nuclear plant will not contaminate Karimunjawa waters because the current in the Java Sea is relatively weak and dominant in the westward direction. Thus, when an NPP leak only runs for 15 days, Karimunjawa waters remain safe.Keyword: 137Cs, Karimunjawa, NPP, modeling, Muria Peninsula

Korea has been achieving the world best safety and economic performance of nuclear power plants through continuous technology development and asset management optimization since its first nuclear power reactor was introduced in the late 1970s. While most countries have stopped building new nuclear power plants since the severe accident in TMI nuclear plant in 1979, Korea has been steadily developing its own reactor models and constructing new nuclear plants. In addition, Korea won recent new nuclear plant project of United Arab Emirates (UAE) as a result of these efforts. A nuclear power plant consists of a great variety of complex equipment having state-of-the-art technologies, and the highest nuclear safety and equipment reliability are required. Therefore, the most sophisticated systematic engineering asset management is essential to the nuclear power plant. As a responsible company of operating and constructing all nuclear power plants in Korea, Korea Hydro and Nuclear Power Co. (KHNP) has developed its own asset management model for the nuclear power plants in operation and expanded the model into the new plants under construction. Since the asset management model was developed for the various equipment types in the nuclear power plant, it can be easily utilized in other industries as a highly effective asset management model. This paper presents new and innovative methods to refine and improve existing asset management practices in general plants by diagnosing KHNP’s physical asset management model. It contributes to the development and improvement of an advanced asset management model for general plant industries and utilities to meet the objectives of securing a clean environment, improved public health and safety, and general community well being.

We thank Sani Rachman Soleman et al. for three specific points of criticism concerning our investigation of the ecological association between low birth weight (LBW) and radioactive contamination in Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accidents:Ecological variables are not justified enough to adjust potential confounding.The spatiotemporal regression model does not consider temporal reduction in radiation dose rate.Dose-response plot between dose rates and odds ratios overestimates R2and underestimates p-value.This criticism is a good starting point to explain some of the technical backgrounds of our approach in more detail.

A combination of Convolutional Neural Network (CNN), Long-Short Term Memory (LSTM), and Convolutional LSTM (ConvLSTM) is constructed in this work for the fault diagnosis and post-accident prediction for Loss of Coolant Accidents (LOCAs) in Nuclear Power Plants (NPPs). The advantages of ConvLSTM, such as effective feature determination and extraction, are applied to the classification of LOCA cases. The prediction accuracy is enhanced via the collaborative work of CNN and LSTM. Such a hybrid model is proved to be functional, accurate, and adaptive, offering quick accident judgment and a reliable decision basis for the emergency response purpose. It then allows NPPs to have an Artificial Intelligence (AI)-based solution for fault diagnosis and post-accident prediction.

Reliable evaluations of the radiological consequences of hypothetical severe accidents in nuclear power plants (NPPs) play a key role in supporting the emergency and preparedness plans during such abnormal events. Also triggered by the growing requests of the national regulators, one of the milestones of the Nuclear Safety Research program (NUSAFE) of the Karlsruhe Institute of Technology (KIT) is the improvement of the performance of the codes employed for such evaluations in the current and innovative NPPs, which are in operation and going to be built in EU and worldwide. Having this in mind, a calculation platform of state-of-art codes has been assessed at KIT to evaluate the accident progression, the radiological source term, and the behavior of the fission product dispersion to the environment by also taking into account the corresponding uncertainties. In particular, the CASMO5 lattice physics code, developed by Studsvik Scandpower, is used for a proper evaluation of the fuel inventory loaded in the reactor core. The European reference Accident Source Term Evaluation Code (ASTEC), developed by IRSN (France), is employed to evaluate the accident progression from the initiation to the fission produced release to the environment. The use of the KArlsruhe Tool for Uncertainty and Sensitivity Analysis (KATUSA), developed by KIT, aims at performing the uncertainty quantification of the source term. Finally, the Java Real-time On-line DecisiOn Support (JRODOS) is employed for analyzing the radiological consequences of the accident. The KIT platform has been employing since some years in the frame of the KIT participation to different European projects, i.e., MUSA, SASPAM-SA on SMRs, SANE. In the paper, an overall view of the KIT strategy on severe accident analyses will be provided, and examples of the application of the above-mentioned platform to generic NPPs will be provided, i.e., PWR Konvoi.

Unit-1 of the Bushehr nuclear power plant (BNPP-1) is a VVER-type reactor with 1,000-MWe power constructed near Bushehr city at the coast of the Persian Gulf, Iran. The reactor has been recently operational to near its full power. The radiological impact of nuclear power plant (NPP) accidents is of public concern, and the assessment of radiological consequences of any hypothetical nuclear accident on public exposure is vital. The hypothetical accident scenario considered in this paper is a design-basis accident, that is, a primary coolant leakage to the secondary circuit. This scenario was selected in order to compare and verify the results obtained in the present paper with those reported in the Final Safety Analysis Report (FSAR 2007) of the BNPP-1 and to develop a well-proven methodology that can be used to study other and more severe hypothetical accident scenarios for this reactor. In the present study, the version 2.01 of the PC COSYMA code was applied. In the early phase of the accidental releases, effective doses (from external and internal exposures) as well as individual and collective doses (due to the late phase of accidental releases) were evaluated. The surrounding area of the BNPP-1 within a radius of 80 km was subdivided into seven concentric rings and 16 sectors, and distribution of population and agricultural products was calculated for this grid. The results show that during the first year following the modeled hypothetical accident, the effective doses do not exceed the limit of 5 mSv, for the considered distances from the BNPP-1. The results obtained in this study are in good agreement with those in the FSAR-2007 report. The agreement obtained is in light of many inherent uncertainties and variables existing in the two modeling procedures applied and proves that the methodology applied here can also be used to model other severe hypothetical accident scenarios of the BNPP-1 such as a small and large break in the reactor coolant system as well as beyond design-basis accidents. Such scenarios are planned to be studied in the near future, for this reactor.

External impacts of the hydrometeorological origin have a significant influence on the safety level of objects of use of atomic energy (OUAE), including nuclear power plants (NPP). Therefore, the existing NPP-related safety regulations demand to consider such impacts at all stages of the NPP life cycle. It is important to make decisions on considering or ignoring certain external impacts while designing NPP buildings and structures. The main criterion for such decisions is the probability of a non-project accident associated with the release of radionuclides into the environment when an extreme phenomena occurs. The aim of this study is to develop a concept for refinement regulatory requirements, considering hydrometeorological factors in organization of NPP engineering protection. Criteria for consideration of hazardous and especially hazardous hydrometeorological impacts for design of NPP buildings and structures were analyzed, and recommendations for refinement of regulatory requirements, considering hydrometeorological factors in organization of NPP engineering protection, were developed.

Environmental contamination with radioactive materials caused by the Fukushima Dai-ichi Nuclear Power Plant (NPP) accident in 2011 raised a serious health concern among residents in Japan, and the demand for radiation experts who can handle the radiation-associated problems has increased. The Human Resources Development Center (HRDC) of the National Institute of for Quantum and Radiological Science and Technology in Japan has offered a variety of training programs covering a wide range of technologies associated with radiation since 1959. In this study, the time-course change in the number and age of the applicants for training programs regularly scheduled at HRDC were analyzed to characterize the demand after the NPP accident. The results suggested that the demand for the training of industrial radiation experts elevated sharply after the NPP accident followed by a prompt decrease, and that young people were likely stimulated to learn the basics of radiation. The demand for the training of medical radiation experts was kept high regardless of the NPP accident. The demand for the training of radiation emergency experts fluctuated apparently with three components: a terminating demand after the criticality accident that occurred in 1999, an urgent demand for handling of the NPP accident, and a sustained demand from local governments that undertook reinforcement of their nuclear disaster prevention program. The demand for the training of school students appeared to be increasing after the NPP accident. It could be foreseen that the demand for training programs targeting young people and medical radiation experts would be elevated in future.

Accident management support tools in nuclear power plants: A post-Fukushima review

Application and experience of a two-dosimeter algorithm for better estimation of effective dose during maintenance periods at Korea nuclear power plants

The demand for nuclear energy has increased in recent years mainly in the developing countries of the Asia-Pacific. Despite the Japanese (Fukushima) nuclear power plant accident in 2011, the nuclear power industry is expected to inflate exponentially in the coming decade to maintain the delicate balance between sustainable socioeconomic development and environmental fortification. Therefore, an overwhelming majority of states are inclined to add nuclear power plants to their national grids. India and Pakistan, neither party to the Nuclear Non-Proliferation treaty (NPT) nor members of the Nuclear Supplier Group (NSG), are included in the list of new contenders. These two institutional arrangements forbid nuclear cooperation with states that have unsafeguarded facilities and are not party states to the NPT. Besides, India has been mainstreamed in international nuclear commerce whereas Pakistan is deprived of similar rights despite the fact that energy deficiency plagues its socioeconomic developments. The study finds that the existing, ambiguous construct that promotes peaceful uses of nuclear technology and simultaneously opposes nuclear proliferation is not consistent with 21st century's realities. Therefore, the non-proliferation construct necessitates revisions in order to meet the contemporary demands to address developing states' energy needs based on a renewed framework.

In the situation of nuclear accidents of nuclear power plants(NPP), the protective actions should be taken by the public are ascertained by Generic Intervention Level(GIL) and the controls should be placed in food are ascertained by Generic Action Level(GAL). GIL and GAL were not designed to be used during an emergency; they cannot be promptly measured in the field and do not address facility conditions. Operational Intervention Level(OIL) which can easily be measured during an emergency, and on which the need for protective action can be rapidly ascertained, was introduced and described in detail by International Atomic Energy Agency(IAEA). According to the approach of calculation and revision proposed by IAEA, the adaptive OILs are studied and given in each nuclear power plant in China. Further, software system for calculation and revision of OILs and determining protective actions have been also established and applied in these NPPs. After Fukushima nuclear accident, emergency response preparedness for multi-reactor accidents is taken seriously. As the generic assessment procedures for determining protective actions during a reactor accident based on OILs mentioned above are not fully applicable to the situation of multi-reactor accident, it is necessary to optimize the approach of calculation of OILs and determining protective actions for multi-reactor accident. The paper first introduces and summarizes the basic concept and approach of OIL during a reactor accident. In this approach, environmental data are assessed primarily through the use of OILs which are quantities directly measured by the field instruments. The default OILs which have been calculated in advance on the basis of the characteristics of severe reactor accidents are used to assess environmental data and take protective actions until sufficient environmental samples are taken and analyzed to provide a basis for their revision. This approach allows data to be quickly evaluated, and decisions on protective actions to be promptly made. The paper studies the essence of OILs during single reactor accident and presents the method for OILs calculation during multi-reactor accident. The core idea of the method is to evaluate the environmental radioactive consequence of each single reactor accident which can be overlaid together finally during a multi-reactor accident. Using the final environmental radioactive consequence, the suitable OILs can be calculated in the original calculation formula. As the default assumptions are not related to characteristics of reactor and site, the default OIL5 of IAEA is suitable for multi-reactor accident. The default of other OILs (OIL1$1 \sim$OIL4, OIL6$6 \sim$OIL9) can be calculated in this optimized method. The paper also indicates that the approach of revision of OILs during a single reactor accident is also suitable for multi-reactor accident without optimizing. In this method, the procedures and strategies of determining protective actions are also optimized. Different from sector areas based on distance and direction during a reactor accident, regions based on administrative boundaries and natural boundaries are considered as unified units for taking a determined protective action. On the basic of the optimized method, the corresponding software system is also designed and implemented. Suitable for both single-reactor and multi-reactor accident, the software provides complete process for use of OILs which include the function of data management, environmental data input, calculation, revision and decisions on protective actions. The optimized method and system in this paper have been applied to several NPPs in China, e.g. Qinshan, Ningde, Sanmen, Taishan and Yangjiang. In the application, the method has been verified and the system has also been constantly improved.