For proof of existing technical foresight regarding the accident and failure paths at Fukushima Diiachi, please read “The Menace of Atomic Energy” by Nader and Abbott, Outback Press, Victoria, Australia. Copyright 1977. ISBN 0 86888 0515. Also please see https://nuclearhistory.wordpress.com/2014/01/29/the-eccs-controversey-of-the-1960s-and-1970s-usa-in-the-light-of-march-2011/
THE FUKUSHIMA DAIICHI ACCIDENT REPORT BY THE DIRECTOR GENERAL IAEA INTERNATIONAL ATOMIC ENERGY AGENCY GC(59)/14
“A major factor that contributed to the accident was the widespread assumption in Japan that its nuclear power plants were so safe that an accident of this magnitude was simply unthinkable. This assumption was accepted by nuclear power plant operators and was not challenged by regulators or by the Government. As a result, Japan was not sufficiently prepared for a severe nuclear accident in March 2011. The Fukushima Daiichi accident exposed certain weaknesses in Japan’s regulatory framework. Responsibilities were divided among a number of bodies, and it was not always clear where authority lay.
There were also certain weaknesses in plant design, in emergency preparedness and response arrangements and in planning for the management of a severe accident. There was an assumption that there would never be a loss of all electrical power at a nuclear power plant for more than a short period. The possibility of several reactors at the same facility suffering a crisis at the same time was not considered. And insufficient provision was made for the possibility of a nuclear accident occurring at the same time as a major natural disaster….. “
“At the Fukushima Daiichi nuclear power plant, operated by the Tokyo Electric Power Company (TEPCO), the earthquake caused damage to the electric power supply lines to the site, and the tsunami caused substantial destruction of the operational and safety infrastructure on the site. The combined effect led to the loss of off-site and on-site electrical power. This resulted in the loss of the cooling function at the three operating reactor units2 as well as at the spent fuel pools. The four other nuclear power plants3 along the coast were also affected to different degrees by the earthquake and tsunami. However, all operating reactor units at these plants were safely shut down.
Despite the efforts of the operators at the Fukushima Daiichi nuclear power plant to maintain control, the reactor cores in Units 1–3 overheated, the nuclear fuel melted and the three containment vessels were breached. Hydrogen was released from the reactor pressure vessels, leading to explosions inside the reactor buildings in Units 1, 3 and 4 that damaged structures and equipment and injured personnel. Radionuclides were released from the plant to the atmosphere and were deposited on land and on the ocean. There were also direct releases into the sea.
People within a radius of 20 km of the site and in other designated areas were evacuated, and those within a radius of 20–30 km were instructed to shelter before later being advised to voluntarily evacuate. Restrictions were placed on the distribution and consumption of food and the consumption of drinking water. At the time of writing, many people were still living outside the areas from which they were evacuated….. “
“Prior to the earthquake, the Japan Trench was categorized as a subduction zone with a frequent occurrence of magnitude 8 class earthquakes; an earthquake of magnitude 9.0 off the coast of Fukushima Prefecture was not considered to be credible by Japanese scientists. However, similar or higher magnitudes had been registered in different areas in similar tectonic environments in the past few decades.
There were no indications that the main safety features of the plant were affected by the vibratory ground motions generated by the earthquake on 11 March 2011. This was due to the conservative approach to earthquake design and construction of nuclear power plants in Japan, resulting in a plant
that was provided with sufficient safety margins. However, the original design considerations did not provide comparable safety margins for extreme external flooding events, such as tsunamis. …”
“The design of the Fukushima Daiichi nuclear power plant provided equipment and systems for the first three levels of defence in depth: (1) equipment intended to provide reliable normal operation; (2) equipment intended to return the plant to a safe state after an abnormal event; and (3) safety systems intended to manage accident conditions. The design bases were derived using a range of postulated hazards; however, external hazards such as tsunamis were not fully addressed. Consequently, the flooding resulting from the tsunami simultaneously challenged the first three protective levels of defence in depth, resulting in common cause failures of equipment and systems at each of the three levels. ..
The common cause failures of multiple safety systems resulted in plant conditions that were not envisaged in the design. Consequently, the means of protection intended to provide the fourth level of defence in depth, that is, prevention of the progression of severe accidents and mitigation of their consequences, were not available to restore the reactor cooling and to maintain the integrity of the containment. The complete loss of power, the lack of information on relevant safety parameters due to the unavailability of the necessary instruments, the loss of control devices and the insufficiency of operating procedures made it impossible to arrest the progression of the accident and to limit its consequences.
The failure to provide sufficient means of protection at each level of defence in depth resulted in severe reactor damage in Units 1, 2 and 3 and in significant radioactive releases from these units. “
“The operators were not fully prepared for the multi-unit loss of power and the loss of cooling caused by the tsunami. Although TEPCO had developed severe accident management guidelines, they did not cover this unlikely combination of events. Operators had therefore not received appropriate training and had not taken part in relevant severe accident exercises, and the equipment available to them was not adequate in the degraded plant conditions.”
“At the time of the accident, separate arrangements were in place to respond to nuclear emergencies and natural disasters at the national and local levels. There were no coordinated arrangements for responding to a nuclear emergency and a natural disaster occurring simultaneously. “
“The consequences of the earthquake and tsunami, and increased radiation levels, made the on-site response extremely difficult. The loss of AC and DC electrical power, the presence of a huge amount of rubble that hindered on-site response measures, aftershocks, alerts of further tsunamis and increased radiation levels meant that many mitigatory actions could not be carried out in a timely manner. The national Government was involved in decisions concerning mitigatory action on the site.
The activation of the emergency Off-site Centre, located 5 km from the Fukushima Daiichi nuclear power plant, was difficult because of extensive infrastructure damage caused by the earthquake and tsunami. Within a few days, it became necessary to evacuate the Off-site Centre due to adverse radiological conditions. “
“National emergency arrangements at the time of the accident envisaged that decisions on protective actions would be based on estimates of the projected dose to the public that would be calculated when a decision was necessary, using a dose projection model — the System for Prediction of Environmental Emergency Dose Information (SPEEDI). The arrangements did not envisage that
decisions on urgent protective actions for the public would be based on predefined specific plant conditions. However, in response to the accident, the initial decisions on protective actions were made on the basis of plant conditions. Estimates of the source term could not be provided as an input to SPEEDI owing to the loss of on-site power. “
“The evacuation of people from the vicinity of the Fukushima Daiichi nuclear power plant began in the evening of 11 March 2011, with the evacuation zone gradually extended from a radius of 2 km of the plant to 3 km and then to 10 km. By the evening of 12 March, it had been extended to 20 km. Similarly, the area in which people were ordered to shelter was extended from within 3–10 km of the plant shortly after the accident to within 20–30 km by 15 March. In the area within a 20–30 km radius of the nuclear power plant, the public was ordered to shelter until 25 March, when the national Government recommended voluntary evacuation. Administration of stable iodine for iodine thyroid blocking was not implemented uniformly, primarily due to the lack of detailed arrangements.
There were difficulties in evacuation due to the damage caused by the earthquake and tsunami and the resulting communication and transportation problems. There were also significant difficulties encountered when evacuating patients from hospitals and nursing homes within the 20 km evacuation zone.
On 22 April, the existing 20 km evacuation zone was established as a ‘Restricted Area’, with controlled re-entry. A ‘Deliberate Evacuation Area’ was also established beyond the ‘Restricted Area’ in locations where the specific dose criteria for relocation might be exceeded.
Once radionuclides were detected in the environment, arrangements were made regarding protective actions in the agricultural area and restrictions on the consumption and distribution of food and consumption of drinking water. In addition, a certification system for food and other products intended for export was established.
Several channels were used to keep the public informed and to respond to people’s concerns during the emergency, including television, radio, the Internet and telephone hotlines. Feedback from the public received via hotlines and counselling services identified the need for easily understandable information and supporting material. “
“The accident resulted in the release of radionuclides to the environment. Assessments of the releases have been performed by many organizations using different models. Most of the atmospheric releases were blown eastward by the prevailing winds, depositing onto and dispersing within the North Pacific Ocean. Uncertainties in estimations of the amount and composition of the radioactive substances were difficult to resolve for reasons that included the lack of monitored data on the deposition of the atmospheric releases on the ocean.
Changes in the wind direction meant that a relatively small part of the atmospheric releases were deposited on land, mostly in a north-westerly direction from the Fukushima Daiichi nuclear power plant. The presence and activity of radionuclides deposited in the terrestrial environment were monitored and characterized. The measured activity of radionuclides decreases over time due to physical decay, environmental transport processes and cleanup activities.
In addition to radionuclides entering the ocean from the atmospheric deposition, there were liquid releases and discharges from the Fukushima Daiichi nuclear power plant directly into the sea at the site. The precise movement of radionuclides in the ocean is difficult to assess by measurements alone, but a number of oceanic transport models have been used to estimate the oceanic dispersion.
Radionuclides such as iodine-131, caesium-134 and caesium-137 were released and found in drinking water, food and some non-edible items. Restrictions to prevent the consumption of these products were established by the Japanese authorities in response to the accident.”
“Following the accident, the Japanese authorities applied conservative reference levels of dose included in the recent ICRP recommendations9. The application of some of the protective measures and actions proved to be difficult for the implementing authorities and very demanding for the people affected.
There were some differences between the national and international criteria and guidance for controlling drinking water, food and non-edible consumer products in the longer term aftermath of the accident, once the emergency phase had passed. “
“ . In the short term, the most significant contributors to the exposure of the public were: (1) external exposure from radionuclides in the plume and deposited on the ground; and (2) internal exposure of the thyroid gland, due to the intake of iodine-131, and internal exposure of other organs and tissues, mainly due to the intake of caesium-134 and caesium-137. In the long term, the most important contributor to the exposure of the public will be external radiation from the deposited caesium-137.
The early assessments of radiation doses used environmental monitoring and dose estimation models, resulting in some overestimations. For the estimates in this report, personal monitoring data provided by the local authorities were also included to provide more robust information on the actual individual doses incurred and their distribution. These estimates indicate that the effective doses incurred by members of the public were low and generally comparable with the range of effective doses incurred due to global levels of natural background radiation.
In the aftermath of a nuclear accident involving releases of iodine-131 and its intake by children, the uptake and subsequent doses to their thyroid glands are a particular concern. Following the Fukushima Daiichi accident, the reported thyroid equivalent doses of children were low because their intake of iodine-131 was limited, partly due to restrictions placed on drinking water and food, including leafy vegetables and fresh milk. There are uncertainties concerning the iodine intakes immediately following the accident due to the scarcity of reliable personal radiation monitoring data for this period.
By December 2011, around 23 000 emergency workers had been involved in the emergency operations. The effective doses incurred by most of them were below the occupational dose limits in Japan. Of this number, 174 exceeded the original criterion for emergency workers and 6 emergency workers exceeded the temporarily revised effective dose criterion in an emergency established by the Japanese authority. Some shortcomings occurred in the implementation of occupational radiation protection requirements, including during the early monitoring and recording of radiation doses of emergency workers, in the availability and use of some protective equipment and in associated training. “
“ . No early radiation induced health effects were observed among workers or members of the public that could be attributed to the accident.
The latency time for late radiation health effects can be decades, and therefore it is not possible to discount the potential occurrence of such effects among an exposed population by observations a few years after exposure. However, given the low levels of doses reported among members of the public, the conclusions of this report are in agreement with those of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) to the United Nations General Assembly.10 UNSCEAR found that “no discernible increased incidence of radiation-related health effects are expected among exposed members of the public and their descendants” (which was reported within the context of the health implications related to “levels and effects of radiation exposure due to the nuclear accident after the 2011 great east-Japan earthquake and tsunami”).11 Among the group of workers who received effective doses of 100 mSv or more, UNSCEAR concluded that “an increased risk of cancer would be expected in the future. However, any increased incidence of cancer in this group is expected to be indiscernible because of the difficulty of confirming such a small incidence against the normal statistical fluctuations in cancer incidence.”12 “
“The long term goal of post-accident recovery16 is to re-establish an acceptable basis for a fully functioning society in the affected areas. Consideration needs to be given to remediation17 of the areas affected by the accident in order to reduce radiation doses, consistent with adopted reference levels. In preparing for the return of evacuees, factors such as the restoration of infrastructure and the viability and sustainable economic activity of the community need to be considered. “
“Japanese authorities have estimated that the timescale for completing decommissioning activities is likely to be in the range of 30–40 years. Decisions regarding the final conditions of the plant and site will be the subject of further analysis and discussions. “
“Following the Fukushima Daiichi accident, there were difficulties in establishing locations to store the large amounts of contaminated material arising from off-site remediation activities. At the time of writing, several hundred temporary storage facilities had been established in local communities and efforts to establish an interim storage facility were continuing. “
“The nuclear accident and radiation protection measures introduced in both the emergency and post- accident recovery phases have had significant consequences for the way of life of the affected population. Evacuation and relocation measures and restrictions on food involved hardships for the people affected. The revitalization and reconstruction projects introduced in Fukushima Prefecture were developed from an understanding of the socioeconomic consequences of the accident. These projects address issues such as reconstruction of infrastructure, community revitalization and support and compensation.
Communication with the public on recovery activities is essential to build trust. ….”