Active Faults and Nuclear Power Plants

The aim of this review was to summarize the lessons learned from the experience in protecting the health of workers engaged in operations following the accident at the Fukushima Daiichi Nuclear Power Plant (NPP). We reviewed all types of scientific papers examining workers' health found in Medline and Web of Sciences as well as some official reports published by the Ministry of Health, Labour and Welfare of Japan and other governmental institutes. The papers and reports were classified into those investigating workers at the Fukushima Daiichi and Daini NPPs, workers engaged in decontamination operations in designated areas, and other workers. Regarding workers at the NPPs, many efforts were made to establish an emergency-care and occupational health system. Risk management efforts were undertaken for radiation exposure, heat stress, psychological stress, outbreak of infectious diseases, and fitness for work. Only a few reports dealt with decontamination workers and others; however, the health management of these workers was clearly weaker than that for workers at the NPPs. Many lessons can be learned from what occurred. That knowledge can be applied to ongoing decommissioning work and to future disasters. In addition, it is necessary to study the long-term health effects of radiation exposure and to accumulate data about the health of workers engaged in decontamination work and other areas.

Japan was hit by the Great East Japan Earthquake and by the resultant big “tsunami” (big tidal waves) on March 11, 2011. For researchers and engineers in the field of electric power or nuclear engineering in countries other than Japan, the memory of the disaster that occurred in the Fukushima Daiichi (= First) Nuclear Power Plant might have still been more vivid and memorized more strongly than the tsunami. Figure 1 is a map of Japan showing the locations of the area hit by the tsunami and the Fukushima Daiichi nuclear power plant. As of December 2019, the death toll by tsunami exceeds 18,400. Although the Fukushima Daiichi disaster itself caused no deaths, at least directly, several areas surrounding the nuclear power plant are still off-limits to the public. For supporting the restoration of Fukushima, many sectors and organizations affiliated to the Japanese Government have been conducting lots of projects. One such project is called the Fukushima FORWARD project [1]. Here, FORWARD is an abbreviation of “Floating Offshore Wind Farm Demonstration”. The project was conducted by the Fukushima offshore wind consortium, composed of eight companies such as Mitsubishi Heavy Industries, Ltd., Hitachi, Ltd., Furukawa Electric Co., and the University of Tokyo. It was first funded and entrusted by the Ministry of Economy, Trade, and Industry in the years from 2011 to 2015. It was then extended to 2020 as a second project.

Fuel debris in the Fukushima Daiichi nuclear power plant is thought to contain borides that are generated from B4C control material. In order to successfully devise methods to effectively remove the debris material, characterization of the properties of the fuel debris is essential. This paper presents some of the thermophysical and mechanical properties of two types of borides, FeB and CrB, and compares them with those of Fe2B and ZrB2. These are the representative borides that might have been generated in the Fukushima Daiichi (1F) nuclear power plant accident. We observed that the thermal conductivity values of both CrB and FeB are much lower than that of ZrB2, and are similar to that of Fe2B. Moreover, the Vickers hardness and fracture toughness of FeB and CrB are almost identical to each other, and similar to those of ZrB2 and Fe2B.

Distribution of oceanic 137Cs from the Fukushima Dai-ichi Nuclear Power Plant simulated numerically by a regional ocean model

A huge earthquake struck the northeast coast of the main island of Japan on 11 March 2011, triggering a tsunami with more than 10-m-high waves hitting the area. The earthquake was followed by numerous sustained aftershocks. The earthquake and aftershocks left almost 16,000 people dead and more than 2,800 missing (as of 11 March 2014). The earthquake affected the Fukushima Daiichi Nuclear Power Plant (NPP) of Tokyo Electric Power Company (TEPCO), causing serious damage to the NPP and resulting in large amounts of radioactive materials being released into not only controlled areas but also the environment. Damage was caused to the cooling systems of the NPP, although they automatically shut down after the earthquake. The trouble with the cooling systems led to hydrogen explosions and core meltdown. The major nuclides released on land were ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs. The release of these radioactive materials resulted in contamination of first responders and workers and also a high ambient dose of radiation around the NPP. The local hospital system, including that for radiation emergency medicine, was dysfunctional. Hospitals that had been designated as radiation emergency facilities were not able to function because the earthquake and tsunami had caused damage to their facilities; some of these were located within a 20-km radius of the NPP and in the evacuation areas. Local fire department personnel were also ordered to evacuate. Fukushima prefecture changed the screening level required for decontamination from 13,000 to 100,000 cpm, with decontamination by wiping being performed for over 13,000 cpm. However, as hospitals and fire departments had to abide by lower levels than that of the prefecture for receiving or transporting contaminated patients, these personnel could not accept or transport contaminated people from the NPPs. In addition, hospitals not designated as radiation emergency facilities would not receive patients from the NPPs because of concerns about the health effects of radiation. From this disaster, it was learned that basic knowledge of radiation and its effects is extremely important for health care providers.

Following the Great East Japan Earthquake (GEJE) and the Fukushima Daiichi nuclear power plant accident in 2011, mandatory evacuation orders were issued to residents living near the nuclear power plant in Fukushima prefecture, including some patients receiving home oxygen therapy. Although the vulnerability of patients with home oxygen therapy (one of the population groups most vulnerable to disasters) has been noted, there is little information on the health effects of evacuation in the event of a radiation disaster. A 90-year-old man diagnosed with chronic obstructive pulmonary disease since the age of 70, and lived in a town located approximately 20 km south of the nuclear power plant, died 8 months after the disaster due to worsening health conditions. This case reveals the potential for both physical and psychological burdens experienced by vulnerable groups like patients undergoing home oxygen therapy during evacuations in times of disaster. Although it is only a case report and the information is limited, severe respiratory distress requiring home oxygen therapy may present a significant risk factor for disaster-related deaths, especially in cases where evacuations are prolonged, such as in nuclear disasters. Due to the challenge of obtaining prompt public support immediately after a disaster, home oxygen therapy patients may need to prioritize self-help and mutual assistance in their disaster preparedness efforts.

The access to reliable sources of energy is the key to sustainable development of mankind. The major part of the energy consumed by people is generated with a chemical reaction of fossil fuel burning. This leads to quick depletion of natural resources and progressing environmental pollution. The contribution of the renewable energy sources to the general energy production remains insignificant. A modern 1,000 MW coal-fired thermal power plant (TPP) burns 2.5 million tons of coal per year and produces significant amount of solid and gaseous waste. TPPs are the largest consumers of atmospheric oxygen and sources of carbon dioxide. A nuclear power plant (NPP) of the same power consumes less than 50 tons of fuel per year. Environmentally significant NPP’s waste (liquid, solid and gaseous) is carefully collected, reduced in volume (evaporation, filtering, compaction, incineration, etc.) and securely isolated from the environment at the plant. The annual volume of waste for storage is less than 100 m3. The waste is under the control of a special NPP’s service and regulatory authorities. The energy of fission reaction millions of times exceeding the energy of burning has an enormous potential that mankind can receive. Four hundred and thirty-three nuclear power units with a total capacity of about 400 GW exist in the world. The accident at the Fukushima Daiichi NPP in Japan in March 2011 caused anxiety about nuclear safety throughout the world and raised questions about the future of nuclear power. Now, it is clear that the use of nuclear power will continue to grow in the coming decades, although the growth will be slower than was anticipated before the accident. Many countries with existing nuclear power programmes plan to expand them. Many new countries, both developed and developing, plan to introduce nuclear power. Some countries, such as Germany, plan to abandon nuclear energy. The IAEA’s latest projections show a steady rise in the number of NPPs in the world in the next 20 years. They project a growth in nuclear power capacity by 23% by 2030 in the low projection and by 100% in the high projection [1,2]. The basis of modern nuclear power comprises water-cooled nuclear reactors which use the energy potential of natural uranium inefficiently (thermal reactors). The thermal reactors use isotope U-235 in which the content of natural uranium is <1%. Breeder reactors are capable of using the significant part of energy potential, which is unavailable to thermal light water reactors. As a result, the same starting quantity of uranium can produce 50 times more energy. These reactors can transform U-238 into fissile Pu-239 in larger amounts than they consume fissile material. This feature is called ‘breeding’ [3]. The key problem of using the basic benefitsv of nuclear power is to ensure the safety of its use, as well as decommissioning and reliable isolation of process waste from the biosphere. The long-term large-scale nuclear power should possess guaranteed safety, economic stability and competitiveness, absence of the raw material base restrictions for a long period of time and environmental sustainability (low waste). The nuclear power systems with fast neutron reactors and liquid metal coolant can satisfy these conditions. More than 40 years of Russian experience in the field of construction and operation of sodium fast reactors makes it possible to summarize and analyze the ecological features of reactors of this type, the possibility of their use for sustainable energy supply of mankind and solving environmental problems.

The magnitude-9.0 Great East Japan Earthquake, which struck at 14:46 JST on March 11, 2011, was the largest ever recorded in Japan. Strong quakes were felt not only in Tohoku, the closest region to the epicenter, but also nationwide from Hokkaido to Kyushu. This exceptional event was followed by huge tsunami waves that severely damaged the Fukushima Daiichi nuclear power plant, which consequently developed into an unprecedented crisis. A huge amount of infrastructure and innumerable buildings were damaged in more than 17 prefectures, over 19,000 people died or went missing in 12 prefectures, and more than 5000 people were injured in 20 prefectures.1 Successive failures or shutdowns of nuclear and non-nuclear power plants brought a sustained shortage of electricity across a wide area of Japan, a situation that seriously affected our university and hospital as well as our daily lives and living environment. In response to the crisis, in addition to national and local governmental initiatives, numerous voluntary organizations, companies, schools, and individuals from all over Japan and worldwide headed toward the disaster-stricken area to help rescue victims, deliver subsistence goods, remove rubble, and restore infrastructure. Thanks to the strenuous activities of the Japan Self-Defense Forces, United States (U.S.) Forces, and devoted civilians, major items of infrastructure, including highways, shinkansen (bullet train) tracks, airports, and harbors were restored quite quickly. The damaged nuclear plants were finally stabilized with the best possible efforts, although it will likely be more than three decades before they are finally decommissioned.2

For the investigation of the characteristics and behavior of fallout deposits of the accident at the Fukushima Daiichi Nuclear Power Plant (NPP) in March 2011, autoradiographic imaging was used to examine tree leaves, branches, and barks from locations at 10–60 km south of the Fukushima Daiichi NPP. The autoradiographs revealed particulate contamination in many old leaf samples; few contaminations were present in current-year leaves. Although no particulate contamination was observed on leaves that had grown after the accident, a relatively small amount of radiocesium had become incorporated in the upper leaves of the sampled branches.

The accident in Fukushima Daiichi nuclear power plants shows the important of developing coping strategies for extended station blackout (SBO) scenarios of the nuclear power plants (NPPs). Many NPPs in United State of America are applying FLEX approach as main coping strategies for extended station blackout (SBO) scenarios. In FLEX strategies, outside water injection to reactor cooling system (RCS) and steam generators (SGs) is considered as an effective method to remove residual heat and maintain the inventory of the systems during the accident. This study presents a pretest calculation using MARS code for the Advanced Thermal-hydraulic Test Loop for Accident Simulation (ATLAS) SBO experiment with RCP seal leakage scenario. In the calculation, the turbinedriven auxiliary feed water pumps (TDAFPs) are firstly used after SBO initiation. Then, the outside cooling water injection method is used for long term cooling. In order to minimize operator actions and satisfy requirements of APR1400 emergency operation procedure (EOP), the SGs Atmospheric Dump Valve (ADV) opening ratio, auxiliary feed water (AFW) and outside cooling water injection flow rates were investigated to have suitable values. The analysis results would be useful for performing the experiment to verify the APR 1400 extended SBO optimum mitigation strategy using outside cooling water injection.

An example of environmental radiation status in and around Tokyo immediately after the TEPCO Fukushima Dai-ichi Nuclear Power Plant (NPP) disaster is introduced. The east part of the Metropolis of Tokyo and northwest of Chiba Prefecture are located about 200–250 km south from the NPP. The local governments in the area have officially surveyed the environmental radiation status after the disaster in response to numerous requests from their citizens. The radiation surveillance by local governments has been conducted and technically guided by the radiation protection specialists. The two main goals of the surveillance are (1) to measure the ambient radiation dose (microsieverts per hour) at all the schoolyards, public parks, and representative measuring points selected by the local government, and (2) to measure the specific radioactivity (becquerels per kilogram) of drinking water and local food items. In parallel with these movements, radiation experts in the University of Tokyo also organized a special correspondence team to survey the environmental radiation status immediately after the nuclear disaster. These activities and related data are introduced in this chapter.KeywordsAmbient radiation doseChibaSpecific radioactivityTokyo

Chapter 2 - Improving nuclear power plant flooding hazard analysis through component performance experiments, fragility model development, and smoothed particle hydrodynamic simulation

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.

Decontamination workers may face a high risk of exposure to internal irradiation through inhalation during decontamination activities; there is, however, little previous research on the levels of internal contamination during decontamination procedures. The authors reviewed the medical records, including whole body counter measurements, of decontamination workers in villages near the crippled Fukushima Daiichi Nuclear Power Plant to assess their levels of internal radiation exposure. In total, 83 decontamination workers were enrolled in this study. They were regularly engaged in decontamination activities in highly contaminated areas where surface 137Cs deposition density was over 100 kBq m-2. The present study showed low levels of internal exposure among the decontamination workers near the Fukushima Daiichi nuclear plant. The cesium burdens of all the decontamination workers were below detection limits. They had reported no acute health problems. The resuspension of radioactive materials may cause minimal internal contamination during decontamination activities.

Mt. Fuji is located approximately 300 km southwest of TEPCO's Fukushima Daiichi Nuclear Power Plant. We performed the radiation survey along two main Mt. Fuji's trails from 04:30 to 18:30 on July 9, 2011. We climbed Yoshida trail from Fuji-Subaru Line fifth station (2,300 m in altitude) to Yoshida-Subashiri top (3,720 m in altitude) and descended Subashiri trail from the Yoshida-Subashiri top to Subashiri new fifth station (2,000 m in altitude) on foot while measuring gamma rays. The dose rate 1 m above ground as measured using a NaI(Tl) scintillation survey meter was within the range from 0.03 to 0.05 μSv/h throughout our measuring trip. We used a NaI(Tl) scintillation spectrometer for gamma-ray pulse height spectra measurement. The gamma-ray pulse height spectra obtained at least 2,500 m in altitude on both Yoshida and Subashiri trails showed the peaks of two radioactive cesium isotopes (134Cs and 137Cs) and natural radioactive nuclides. It was confirmed that a radioactive plume released from the Fukushima Daiichi Nuclear Power Plant had arrived at least 2,500 m above sea level of Mt. Fuji.