Nuclear Power Station In Japan Research Articles

Comprehensive analysis of a decade of cumulative radiocesium testing data for foodstuffs throughout Japan after the 2011 Fukushima Daiichi Nuclear Power Plant accident.

The unexpected accident at the Fukushima Daiichi Nuclear Power Station in Japan, which occurred on March 11th, 2011, after the Great East Japan Earthquake and tsunami struck the north-eastern coast of Japan, released radionuclides into the environment. Today, because of the amounts of radionuclides released and their relatively long half-life, the levels of radiocesium contaminating foodstuffs remain a significant food safety concern. Foodstuffs in Japan have been sampled and monitored for 134,137Cs since the accident. More than 2.5 million samples of foodstuffs have been examined with the results reported monthly during each Japanese fiscal year (FY, from April 1st to March 31st) from 2012 to 2021. A total of 5,695 samples of foodstuffs within the “general foodstuffs” category collected during this whole period and 13 foodstuffs within the “drinking water including soft drinks containing tea as a raw material” category sampled in FY 2012 were found to exceed the Japanese maximum permitted level (JML) set at 100 and 10 Bq/kg, respectively. No samples from the “milk and infant foodstuffs” category exceeded the JML (50 Bq/kg). The annual proportions of foodstuffs exceeding the JML in the “general foodstuffs” category varied between 0.37% and 2.57%, and were highest in FY 2012. The 134,137Cs concentration for more than 99% of the foodstuffs monitored and reported has been low and not exceeding the JML in recent years, except for those foodstuffs that are difficult to cultivate, feed or manage, such as wild mushrooms, plants, animals and fish. The monitoring data for foodstuffs show the current status of food safety risks from 134,137Cs contamination, particularly for cultured and aquaculture foodstuffs on the market in Japan.

Hardware/Software Solution for Low Power Evaluation of Tsunami Danger

Carbon footprint reduction issues have been drawing more and more attention these days. Reducing the energy consumption is among the basic directions along this line. In the paper, a low-energy approach to tsunami danger evaluation is concerned. After several disaster tsunamis of the XXIst century, the question arises whether is it possible to evaluate in a couple of minutes the tsunami wave parameters, expected at the particular geo location. The point is that it takes around 20 min for the wave to approach the nearest coast after a seismic event offshore of Japan. Currently, the main tool for studying tsunamis is computer modeling. In particular, the expected tsunami height near the coastline, when a major underwater earthquake is detected, can be estimated by a series of numerical experiments of various scenarios of generation and the following wave propagation. Reducing the calculation time of such scenarios and the necessary energy consumption for this is the scope of this study. Moreover, in case of the major earthquake, the electric power shutdown is possible (e.g., the accident at the Fukushima nuclear power station in Japan on 11 May 2011), so the solution should be of low energy-consuming, preferably based at regular personal computers (PCs) or laptops. The way to achieve the requested performance of numerical modeling at the PC platform is a combination of efficient algorithms and their hardware acceleration. Following this strategy, a solution for the fast numerical simulation of tsunami wave propagation has been proposed. Most of tsunami researchers use the shallow-water approximation to simulate tsunami wave propagation at deep water areas. For software implementation, the MacCormack finite-difference scheme has been chosen, as it is suitable for pipelining. For hardware code acceleration, a special processor, that is, the calculator, has been designed at a field-programmable gate array (FPGA) platform. This combination was tested in terms of precision by comparison with the reference code and with the exact solutions (known for some special cases of the bottom profile). The achieved performance made it possible to calculate the wave propagation over a 1000 × 500 km water area in 1 min (the mesh size was compared to 250 m). It was nearly 300 times faster compared to that of a regular PC and 10 times faster compared to the use of a central processing unit (CPU). This result, being implemented into tsunami warning systems, will make it possible to reduce human casualties and economy losses for the so-called near-field tsunamis. The presented paper discussed the new aspect of such implementation, namely low energy consumption. The corresponding measurements for three platforms (PC and two types of FPGA) have been performed, and a comparison of the obtained results of energy consumption was given. As the numerical simulation of numerous tsunami propagation scenarios from different sources are needed for the purpose of coastal tsunami zoning, the integrated amount of the saving energy is expected to be really valuable. For the time being, tsunami researchers have not used the FPGA-based acceleration of computer code execution. Perhaps, the energy-saving aspect is able to promote the use of FPGAs in tsunami researches. The approach to designing special FPGA-based processors for the fast solution of various engineering problems using a PC could be extended to other areas, such as bioinformatics (motif search in DNA sequences and other algorithms of genome analysis and molecular dynamics) and seismic data processing (three-dimensional (3D) wave package decomposition, data compression, noise suppression, etc.).

CONCEPT DESIGN FOR A SUEZMAX TANKER POWERED BY A 70 MW SMALL MODULAR REACTOR

The authors are to be congratulated on a well- researched and timely technical paper. I am pleased to express my personal opinion on the subject.
 COSCO was intending to initiate a study in December 2009 on nuclear powered ship design in order to reduce GHG emissions from shipping. However, this plan was aborted three years after, following the catastrophic accident at the Fukushima nuclear power station in Japan during March 2011. This intensified political and public opposition to nuclear power to the extent that Germany has since adopted plans to decommission its entire nuclear infrastructure. However, confidence is beginning to re- emerge - confidence which I share. With increasing attention being given to GHG emissions arising from burning fossil fuels for global aviation and marine transport, together with the excellent safety record of nuclear power in the marine environment and the development of the new generation of SMRs, it is quite conceivable that renewed attention will be given to the application of nuclear power in merchant ship propulsion.
 In producing this paper, the authors have made a significant contribution in the field of innovative ship design development. They have demonstrated the feasibility of applying the latest generation of nuclear reactor to commercial ship propulsion. Whereas nuclear power has been widely used in vessels of a number of navies and icebreakers, it has yet to be adopted for commercial ships other than a small number of research projects. This paper has provided good rationale for accommodating nuclear power in merchant shipping including speed and range requirements, required specific volume on board, environmental considerations etc. The study has also considered the risks associated with design and the arrangement of nuclear systems including location of the SMR, type of propulsion options and other safety- critical issues, not least the radiological risk to persons on board, involved in maintenance and in port.

Risk perception regarding implementation of iodine thyroid blocking during a nuclear disaster of mothers living near a nuclear power station in Japan.

Pre-emptive evacuation orders following the accident at the Fukushima Daiichi Nuclear Power Station (FDNPS) in March 2011 and subsequent regulatory limits regarding contaminated food, milk, and water minimized the external and internal radiation exposure doses of nearby residents. However, with regard to implementation of iodine thyroid blocking (ITB), residents were confused because no information on the matter was released by the central and/or local governments. Based on lessons learned from the FDNPS accident, many countries have revised their guidelines regarding ITB during nuclear disasters. To adequately revise such guidelines and ensure effective ITB implementation during a nuclear disaster, however, residents' perceptions of ITB must be clarified. In this study, the perception of risks associated with ITB was investigated in mothers residing near the Sendai Nuclear Power Plant (SNPP) in Kagoshima Prefecture, Japan. Of the 520 mothers surveyed, 467 (89.8%) expressed anxiety regarding the administration of potassium iodine (KI) to their children. Logistic regression analysis revealed that the mothers' anxiety regarding the administration of KI to their children was positively correlated with their wish to consult an expert about KI and their hesitation to let their children eat foods produced in Fukushima, and negatively correlated with having confidence about administering KI to their children. Careful communication of potential risks to mothers residing near nuclear power plants is thus critical for implementing effective ITB in children.

Automatic data acquisition for visualizing radioactive substances by combining a gamma-ray imager and an autonomous mobile robot

To reduce the exposure doses of workers and to establish decontamination plans, it is important to understand and visualize the distribution of radioactive substances at the Fukushima Daiichi Nuclear Power Station in Japan, where an accident occurred on the 11th of March, 2011. In this decommissioning work environment, radioactive substances adhered to various objects, such as rubble and equipment, and it was necessary to visualize the distribution of these contaminants in all three dimensions. The technology used to automatically and remotely acquire data to visualize the distribution of radioactive substances in three dimensions was useful for reducing the exposure dose of the workers and to shorten the survey time. We constructed an automatic data acquisition system that consisted of a Compton camera and a 3D-light detection and ranging sensor mounted on an autonomously moving robot. We also evaluated the system feasibility using radiation sources and succeeded in automatically acquiring the data required for visualizing the radiation sources. For this data acquisition, the operator did not need to operate the system after the measurements were started. The effects of the imaging parameters of the Compton camera and the accuracy of the self-position estimation of the system on the radiation-imaging accuracy are also discussed.

Photoneutron detection in lightning by gadolinium orthosilicate scintillators

During a winter thunderstorm on November 24, 2017, a downward terrestrial gamma-ray flash took place and triggered photonuclear reactions with atmospheric nitrogen and oxygen nuclei, coincident with a lightning discharge at the Kashiwazaki-Kariwa nuclear power station in Japan. We directly detected neutrons produced by the photonuclear reactions with gadolinium orthosilicate scintillation crystals installed at sea level. Two gadolinium isotopes included in the scintillation crystals, $^{155}$Gd and $^{157}$Gd, have large cross-sections of neutron captures to thermal neutrons such as $^{155}$Gd(n,$\gamma$)$^{156}$Gd and $^{157}$Gd(n,$\gamma$)$^{158}$Gd. De-excitation gamma rays from $^{156}$Gd and $^{158}$Gd are self-absorbed in the scintillation crystals, and make spectral-line features which can be distinguished from other non-neutron signals. The neutron burst lasted for $\sim$100~ms, and neutron fluences are estimated to be $>$52 and $>$31~neutrons~cm$^{-2}$ at two observation points inside the power plant. Gadolinium orthosilicate scintillators work as valid detectors for thermal neutrons in lightning.

Preventing risk and promoting resilience in radiation health.

Because risk assessment is fundamentally deficient in the face of unknown or unforeseeable events and disasters such as occurred in 2011 at the Fukushima Daiichi Nuclear Power Station in Japan, resilience thinking, which focuses on the ability of both natural and human-made systems to prepare for, absorb, and recover from an adverse event and to adapt to new conditions is an important additional consideration in decision making. Radiation contamination is an impediment to most critical functions of a community; resilience planning considers how those critical functions will be maintained in the event that radiation contamination does occur. Therefore, planning should begin with resilience-based thinking and should be complemented with risk assessment-based tools. Integr Environ Assess Manag 2016;12:677-679. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Fukushima: The Geo-trauma of a Futural Wave

The enduring effects of the March 2011 tsunami and nuclear meltdown at the Fukushima Dai-ichi Nuclear Power Station in Japan are explored in this paper through the notions of “geo-trauma” in the authors’ work and geophilosophy in Deleuze and Guattari’s philosophy. At the fulcrum of the 2011 global disaster was the nuclear meltdown and the emittance of radioactive material such as Caesium-137 and Strontium-90. This event mattered and matters, dispersing and deterritorializing organic, non-organic, and anorganic life in all of its articulations. In the wake of the singularity of Fukushima and the Anthropocene epoch more generally, it is timely to ruminate upon in what way this event as a futural wave makes “us” as the present generation both responsible for and part of the ongoing Fukushima meltdown. The questions that Fukushima provokes are not about the specific clean-up operation and environmental impacts around the plant, but more about how we can understand Fukushima as an event in nuclear history, or a singularity of “geo-trauma.” The folly of Fukushima and its aftermath, points to something fundamental about the Anthropocene, in the sense that the interconnected patterning that one may derive from the site of the disaster, gives new life to understanding the darker/non-human sides of ecology, the media, the unconscious, contamination, and space. The posthumanism of Deleuze and Guattari combined with the extinctional impetus of the Anthropocene will drive this analysis forward in terms of uncovering new forms of understanding about the Earth, World, territory, land, and Nature.

Implications of the 2011 Great East Japan Tsunami on sea defence design

After the 2004 Boxing Day tsunami, much of the world's effort to defend against tsunami concentrated on tsunami warning and evacuation. The 2011 Great East Japan Earthquake and Tsunami led to direct and indirect losses as well as the deaths of many vulnerable members of Japan's coastal communities. This event has resulted in Japan rethinking and revising its design codes for sea defence structures. The new guidance emerging from this process is a valuable resource for other countries re-evaluating their own current mitigation strategies and this paper presents details of this process. The paper starts with the history of sea defence design standards in Japan and explains the process of revision of design guidelines since 2011. Examples of sea defences that failed and have since been rebuilt, observed during the two Earthquake Engineering Field Investigation Team (EEFIT) missions of 2011 and 2013, are also presented. The paper concludes with a discussion of international approaches and their application to nuclear power stations in Japan and the UK.

A source term estimation method for a nuclear accident using atmospheric dispersion models

The objective of this study is to develop an operational source term estimation (STE) method applicable for a nuclear accident like the incident that occurred at the Fukushima Dai-ichi nuclear power station in 2011. The new STE method presented here is based on data from atmospheric dispersion models and short-range observational data around the nuclear power plants. The accuracy of this method is validated with data from a wind tunnel study that involved a tracer gas release from a scaled model experiment at Tokai Daini nuclear power station in Japan. We then use the methodology developed and validated through the effort described in this manuscript to estimate the release rate of radioactive material from the Fukushima Dai-ichi nuclear power station.

MELCOR Simulations of the Severe Accident at Fukushima Daiichi Unit 3

In response to the accident at the Fukushima Daiichi nuclear power station in Japan, the U.S. Nuclear Regulatory Commission and U.S. Department of Energy agreed to jointly sponsor an accident reconstruction study as a means of assessing the severe accident modeling capability of the MELCOR code. Objectives of the project included reconstruction of the accident progressions using computer models and accident data, and validation of the MELCOR code and the Fukushima models against plant data. A MELCOR 2.1 model of the Fukushima Daiichi Unit 3 reactor is developed using plant-specific information and accident-specific boundary conditions, which involve considerable uncertainty due to the inherent nature of severe accidents. Publicly available thermal-hydraulic data and radioactivity release estimates have evolved significantly since the accidents. Such data are expected to continually change as the reactors are decommissioned and more measurements are performed. The MELCOR simulations in this work primarily use boundary conditions that are based on available plant data as of May 2012.

MELCOR Simulations of the Severe Accident at the Fukushima Daiichi Unit 1 Reactor

In response to the accident at the Fukushima Daiichi nuclear power station in Japan, the U.S. Nuclear Regulatory Commission and U.S. Department of Energy agreed to jointly sponsor an accident reconstruction study as a means of assessing the severe accident modeling capability of the MELCOR code and developing an understanding of the likely accident progression. Objectives of the project included reconstruction of the accident progressions using computer models and accident data, and validation of MELCOR and the Fukushima models against plant data. In this study Sandia National Laboratories developed MELCOR 2.1 models of Fukushima Daiichi Units 1 (1F1), 2, and 3 as well as the Unit 4 spent fuel pool. This paper reports on the analysis of the 1F1 accident. Details are presented on the modeled accident progression, hypothesized mode of failures in the reactor pressure vessel (RPV) and containment pressure boundary, and release of fission products to the environment. The MELCOR-predicted RPV and containment pressure trends compare well with available measured pressures. Conditions leading up to the observed explosion of the reactor building are postulated based on this analysis where drywell head flange leakage is thought to have led to accumulation of flammable gases in the refueling bay. The favorable comparison of the results from the analyses with the data from the plant provides additional confidence in MELCOR to reliably predict real-world accident progression. The modeling effort has also provided insights into future data needs for both model development and validation.

Radiation situation in Kamchatka after the Fukushima nuclear power station accident

The chronology of events in Kamchatka related to the threat of radioactive contamination of the territory as a result of the Fukushima-1 nuclear power station (NPS) accident in Japan is briefly reviewed based on the published data. The accident happened on March 11, 2011, after a strong earthquake near the coast of Japan and the giant tsunami followed by the earthquake. The power supply was damaged and, as a result, the cooling system of NPS reactors was destroyed. Although the reactors did not explode, radioactive emissions from the damaged NPS discharged into the atmosphere and spread over large areas by the air flows. Information about the radiation situation in Kamchatka is controversial. Therefore, the author carried out regular monitoring of the radiation background during a hiking trip in Kamchatka in August 2011. The data are presented in this paper. It was concluded that the radiation background along the route of the trip was consistent (within the accuracy of measurement methods) with the normal values of a natural background. A thorough analysis of air, soil, food samples, etc., is required for a more detailed study to identify the presence of radionuclides in the atmospheric emissions from the damaged NPS in Japan.

A Hydrogen Ignition Mechanism for Explosions in Nuclear Facility Piping Systems

Hydrogen explosions may occur simultaneously with fluid transients' accidents in nuclear facilities, and a theoretical mechanism to relate fluid transients to hydrogen deflagrations and explosions is presented herein. Hydrogen and oxygen generation due to the radiolysis of water is a recognized hazard in piping systems used in the nuclear industry, where the accumulation of hydrogen and oxygen at high points in the piping system is expected, and explosive conditions may occur. Pipe ruptures in nuclear reactor cooling systems were attributed to hydrogen explosions inside pipelines, i.e., Hamaoka, Nuclear Power Station in Japan, and Brunsbuettel in Germany (Fig. 1Fig. 1Hydrogen explosion damage in nuclear facilities Antaki, et al. [9,10–12] (ASME, Task Group on Impulsively Loaded Vessels, 2009, Bob Nickell)). Prior to these accidents, an ignition source for hydrogen was not clearly demonstrated, but these accidents demonstrated that a mechanism was, in fact, available to initiate combustion and explosion. A new theory to identify an ignition source and explosion cause is presented here, and further research is recommended to fully understand this explosion mechanism. In fact, this explosion mechanism may be pertinent to explosions in major nuclear accidents, and a similar explosion mechanism is also possible in oil pipelines during off-shore drilling.

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Introduction to the special issue ‘Tracer Applications in Sediment Research’

The legalities of a nuclear shutdown

In July 2002, Germany amended its Atomic Energy Act so no new nuclear power plants could be built and existing power plants would continue running only for a limited time. In 2009, however, a coalition led by Chancellor Angela Merkel took control of the German government and reversed the country’s nuclear phase-out policy, extending nuclear plant operating lives and announcing that risks associated with nuclear energy were insignificant. Three months later, just days after the nuclear disaster at the Fukushima Daiichi Nuclear Power Station in Japan, the German government abruptly reversed course again, closing eight older nuclear power plants and eventually ordering the nine remaining plants to cease operations by 2022, at the latest. Three out of the four operators of German nuclear power plants have since taken legal action, seeking compensation for profits supposedly lost as a result of the nuclear policy change. But due to a number of factors—including the German constitution, which places a duty on the government to protect citizens, and the nuclear operators’ participation in the original 2002 agreement to phase out nuclear power—most legal observers believe these legal challenges to Germany’s nuclear exit are destined to fail. The German nuclear exit includes financial compromises that allow nuclear operators to recoup investments in their nuclear power plants, and the legal protection these compromises provide to the government may be the part of the German initiative that is of most interest to other countries considering nuclear exits.

The Fukushima Nuclear Power Station incident and marine pollution

Based on the facts relating to the radioactive wastewater discharged by the Fukushima Nuclear Power Station in Japan, this paper intends to explore the international legal obligations for Japan from three perspectives, namely, the immediate notification, the prevention of transboundary harm and the prevention of dumping. Furthermore, this article defines and compares two types of international legal liabilities, the traditional state responsibility and the responsibility for transboundary harm. Through comparison, the international legal liability of Japan is discussed. After detailed analysis, the conclusion is that Japan should be responsible for the obligation of immediate notification and since Japan unilaterally discharge the wastes without prior specific permits of other contracting countries, it should also be responsible for the violation of prevention of dumping. Since so far, no material injury has emerged and there would appear to be no culpability as regards the prevention of transboundary harm. Finally, this paper stresses the necessity to develop a worldwide agreement concerning the liability for transboundary harm and to establish an institutional framework for the enforcement of a state’s obligations, and also the great significance of international cooperation between nations and organisations in relation to marine environmental protection.

Current status of radiological protection at nuclear power stations in Japan

The radiation dose to workers at nuclear power stations (NPSs) in Japan was drastically reduced between the late-1970s and the early-1990s by continuous dose-reduction programmes. The total collective dose of radiation workers in FY 2008 was 84.04 person Sv, while the average collective dose was 1.5 person Sv per reactor. The average annual individual dose was 1.1 mSv and the maximum annual individual dose was 19.5 mSv. These values are sufficiently lower than the regulatory dose limits. Radioactive effluent released from NPSs is already so trivial that additional protective measures will not be necessary. Experience in radiation protection at NPSs has been accumulated over 40 y and will be very useful in establishing a rational radiation control system in the future.

JAPAN’S NUCLEAR CRISIS CONTINUES

IT WILL TAKE UP TO nine months before the crippled Fukushima Daiichi Nuclear Power Station in Japan is stabilized, facility owner Tokyo Electric Power Co. (TEPCO) said last week. Radiation has been leaking from the complex since a massive earthquake-triggered tsunami inundated Japan’s Pacific coast and knocked out cooling systems at the plant’s six reactors just over a month ago. At an April 17 news conference, TEPCO officials unveiled a phased “road map” to bring the crisis under control. In the first three months of the plan, the company hopes to cool the reactors and gradually reduce the level of leaking radiation. Three to six months after that, the utility expects all of the reactors to achieve “cold shutdowns,” a stable condition in which temperatures drop and radiation leaks substantially decline. “It is a sign of the extraordinary seriousness of the Fukushima nuclear disaster that TEPCO anticipates it may take nine more months ...

Occurrence of asymmetrical flow pattern behind an orifice in a circular pipe

Flow behind an orifice is one of the important topics of interests associated with the maintenance of nuclear power stations, because it is closely related to the pipe-wall thinning phenomenon caused by the flow accelerated corrosion, which often occurs in a pipeline behind an orifice in a nuclear power station (JSME 2005, 2009). A typical example of the pipe-wall thinning phenomenon has been observed in a prototype circular pipeline of Mihama nuclear power station in Japan (2004). This phenomenon occurs in the prototype pipeline behind the orifice and is often asymmetrical in circumferential direction even if the pipe shape is circular (Ministry of Economy, Trade and Industry 2004). However, the reason why the asymmetrical pipe-wall thinning occurred in the prototype pipeline has not yet been fully understood. In order to clarify the mechanism, the influence of allowable orifice biases on the flow field behind the orifice has been studied experimentally in a square pipe (Fujisawa and Yamamoto 2009). The result indicates that the flow reattachment behavior behind the orifice is mainly determined by the orifice bias even if it is smaller than the allowable level of standards. However, this phenomenon may be suffered from the influence of pipe shape and the layout of the pipe upstream of the orifice. The purpose of this short paper is to show the new finding of orifice bias effect on the flow behind the orifice in a circular pipe under the influence of swirling flow.