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Abstract
Months after the accident unfolded at the Fukushima Daiichi Nuclear Power Station, the nuclear crisis continues. Though the worst, it seems, has passed, many technical, social, legal, and economic hurdles must be overcome. Major short-term challenges include stabilizing the reactors and managing more than 100,000 tons of contaminated water, as well as cleaning up the site, which still contains a large amount of contaminated debris from the accident. Long-term challenges include dealing with spent fuel in the storage pools and damaged fuel in the reactors, as well as decommissioning the reactors. In a 670-page report to the International Atomic Energy Agency, the Japanese government explored its next steps in managing the crisis. In this article, the author revisits the tragedy at the nuclear station and highlights a few of the most pressing—and most challenging—of the government’s plans. The author writes that Fukushima should contain lessons not just for Japan but for all 31 countries with nuclear power.
At 2:46 p.m. on March 11, in the Tohoku district of Japan, a 9.0 earthquake triggered a massive tsunami that struck the Fukushima Daiichi and Fukushima Daini nuclear power stations operated by the Tokyo Electric Power Company (Tepco). The day became one of historic proportions, forever to be remembered for a nuclear accident unprecedented in both scale and time frame.1 Within hours of this disaster came the painful realization that the nuclear infrastructure—from technical matters, like backup generators, to more administrative concerns, like which agency is responsible for injecting coolant into a reactor—was flawed and devastatingly complex.
Though months have passed, the situation at Fukushima Daiichi is not yet under control; it seems that the worst has happened, however, with no additional discharge of radioactive materials and the unlikely development of this in the future. The Japanese government has expressed the lessons it has learned from this event and, so far, has reacted accordingly: It has demanded that stronger tools and systems be put in place to prevent—and respond to—a severe accident, that a national response to a nuclear emergency be established, and that a safety regulatory infrastructure be developed. These plans are laid out in the 670-page report that the Japanese government submitted to the International Atomic Energy Agency (IAEA) in June (Nuclear Energy Response Headquarters, 2011). Its suggestions are a glimpse of the working handbook of Japan’s nuclear future, a future that is being recast and reshaped to prevent another Chernobyl, another Three Mile Island, and, of course, another Fukushima.
But Japan shouldn’t be the only country reviewing and distilling the lessons from Fukushima. There are 436 nuclear plants operating in 31 countries. It is critical for the world’s nuclear community and policy makers to learn from the information available so far and to continue to push for even more information in the months and years ahead. They must draw on Fukushima’s lessons to ensure that the existing nuclear facilities are safe and to explore the possible implications for future nuclear energy policy.2
Prevention of a severe accident
The Fukushima Daiichi accident was unique in that it was caused by a massive earthquake and a devastating tsunami. Both the earthquake and tsunami were beyond safety-design basis—that is, at the conception of design, the accidents were considered possible but unlikely. Currently, there is no evidence that the earthquake caused the malfunction of the reactors’ cooling capability or the power blackout, but it is still necessary to verify this speculation. The tsunami, however, is a different story. It is clear that the height of the tsunami—more than 10 meters—was underestimated by both the Nuclear and Industry Safety Agency (NISA), Japan’s regulator, and Tepco.
In June 2009, when a working group met to discuss earthquake and tsunami risks, Yukinobu Okamura, a government researcher, said, “I cannot accept this report because it does not mention it [Jogan earthquake and tsunami] at all, [even though] it hit the Tohoku area in 869 with huge impact” (Joint Working Group on Earthquake/Tsunami, 2009, emphasis added). The researcher was complaining that the new report by the advisory committee—of which he was a member—did not thoroughly consider the Jogan tsunami. Further, Katsuhiko Ishibashi, a former member of an advisory committee for the Nuclear Safety Commission—which advises the prime minister, oversees NISA’s activities, and establishes basic safety guidelines—also expressed similar warnings in a paper published in Science in 1997: “For nuclear power plants, a disaster caused by an earthquake can be especially dangerous because it could cause multiple failures at the same time, unlike a normal accident” (Ishibashi, 1997: 723, emphasis added).
These warnings now seem almost prescient in light of Fukushima, and it is regrettable that the opinions of these experts, as well as others, were not taken seriously. These examples illustrate that there is a need to restructure the safety regulatory process, but specific recommendations have not yet been made by the government. How to incorporate minority opinions—and how to reflect the most updated information—are key issues that need to be resolved and are instrumental in effectively planning for station-blackout scenarios and securing a reactor’s cooling capability during a severe accident.
Prepare for the worst
The Fukushima Daiichi Nuclear Power Station consists of six units that house multiple emergency diesel generators. With the exception of one emergency diesel generator at Unit 6, all the other emergency diesel generators at the six units were lost to the tsunami. The Fukushima accident became so detrimental because it was impossible to secure the necessary power supply for the cooling of the reactors.
In the Nuclear Safety Commission’s regulatory guide for the safety review process, the clear assumption was that, when all emergency generators were lost at one unit, power could be sent from other units on the same site. The life of the backup batteries—eight hours—was long compared with the time required to restore the alternating current (AC) power supply, which it was assumed would be restored within just a few hours. In fact, this regulatory guide does not even consider a total AC power loss as a design-basis event: “No particular considerations are necessary against a long-term total AC power loss, assuming that the emergency AC power system is reliable enough.”
In Japan, probabilistic safety assessment—or probabilistic risk assessment as it is sometimes referred to—has not always been effectively used in the overall review process at nuclear power plants. And Fukushima is a raw example of this: By not factoring in a rare event like a large-scale tsunami, Japan did not make sufficient efforts to improve the reliability of the assessments.
In the weeks after the disaster, the Japanese government recommended swift utilization of probabilistic safety assessments and the improvement of safety measures (including effective accident management based on the safety assessments). This is necessary to move Japanese safety regulation to something that is more risk-based and more effective—and this would mean a departure from being a “zero-risk” culture.
Secure cooling capability
There were many reasons why the accident at the Fukushima plant spun out of control, including that the reactors lost all cooling capability, threatening a core meltdown. Although the reactors were cooled by actively injecting water, the core damage could not be prevented, because the power supply was lost and the injected water drained. This same type of cooling capability was also applied to the spent-fuel storage pools.
In its June report to the IAEA, the Japanese government recommended that alternative cooling functions of reactors and primary containment vessels should be secured with alternative final heat sinks (heat absorption) until AC power resumes. This will be pursued through such means as diversifying alternative water injection functions, varying and increasing sources for injection water, and introducing an air-cooling system.
Create thorough accident-management measures
Japan’s first commercial nuclear power station went online in 1966. The “severe accident”3 management measures—that is, actions such as venting steam from a containment vessel, preventing a hydrogen explosion, etc.—were not introduced in Japan until 1992. In fact, the guidelines for accident management have not been reviewed since their inception. These measures were not established as a legal requirement but as voluntary efforts by operators.
In its report to the IAEA, the Japanese government recommended that accident-management measures should be changed from voluntary efforts to legal requirements and be developed by using a probabilistic safety-assessment approach. This would mean that the nuclear industry’s measures for accident management would be open and more transparent.
Response to a severe accident
Given the magnitude of the accident and the complicated environment in which agencies responded during the disaster, the efforts made by Tepco’s operating team were probably as good as could be expected under such stressful conditions. The outcome at the nuclear plant, however, was quite the opposite: With three core meltdowns and possible hydrogen explosions at four units, the accident was considered one of the worst nuclear accidents ever.
Very technical lessons must be learned in order to move forward in a safe nuclear energy world: how to prevent a hydrogen explosion, how to enhance the containment and venting systems, and how to enhance the emergency-response capability.
Prevent a hydrogen explosion
Most likely caused by hydrogen combustion, four explosions occurred within days of the earthquake and tsunami: the first at Unit 1 at 3:36 p.m. local time on March 12 and the second at Unit 3 at 11:01 a.m. on March 14. The next day, March 15, an explosive sound, as well as the detection of increased radioactivity at the suppression pool of Unit 2, led authorities to believe there had been another explosion—this has yet to be confirmed, but the speculation is that it may have caused a large release of radioactive materials (gas, aerosol, and contaminated water) into the environment. That same day, another unexpected blast occurred at Unit 4 and damaged the reactor building, destroying its walls. The cause of this explosion is not known yet, but it is speculated that hydrogen generated in Unit 3 may have escaped into the reactor building of Unit 4 through venting pipes etc. A flammability control system, which functions to keep the concentration of flammable gas below the explosive limit, was introduced in Japan in 1992; however, the system was not designed to prevent hydrogen combustion inside a reactor building.
In its report to the IAEA, the Japanese government expressed plans to enhance measures to prevent a hydrogen explosion inside a reactor building. Based on this recommendation, as an emergency-response protocol, NISA announced that measures must be created to release hydrogen gas from the reactor building, such as creating a vent hole to release pressure. During the accident, the operators discovered that there were problems in operating the containment venting system in the face of a severe accident. Specifically, the system was not designed to be operated without power, that is, manually. In addition, the removal of radioactive material from released (vented) air into the environment was found to be insufficient. Thus, the emergency venting system must be more readily operable and more efficient.
Enhance emergency response
Immediately after the accident, the atmosphere at the Fukushima plant was anything but smooth and calm: The radiation dosage increased in the main control room, and the operators were temporarily prohibited from entering; no electricity meant no lighting, and computer and telephone lines were also down; instrumentation to measure water levels, pressure, and temperature did not function well. And even logistical support, like transporting extra batteries and power sources from off-site locations, was not sufficient due to road and vehicle damage caused by the earthquake and tsunami. It was very difficult to mobilize rescue teams to help with emergency supplies and equipment. In short, there was an ineffective response to a severe accident.
It is unsurprising, then, that the Japanese government has recommended improvements in response efforts, specifically better training and equipment for staff, including better instrumentation, better radiation protection, and a better logistical support system; however, it hasn’t specified exactly how to achieve this goal.
National response to a nuclear emergency
The Japanese government has some previous experience with revising its nuclear policies following an accident. In 1999, when the Tokaimura nuclear accident (known as the JCO criticality accident) happened, it was the first nuclear energy accident in Japan that forced local residents to evacuate. After this incident, in an attempt to establish basic organizational structures, areas of responsibility, and a streamlined process, the government created the Act on Special Measures Concerning Nuclear Emergency Preparedness. Under this act, when a serious nuclear accident happens, a national nuclear emergency-response headquarters is temporarily established at the prime minister’s office, and local emergency-response centers at designated off-site facilities near each of the country’s affected nuclear plants spring into action.
In March, due to power outages and earthquake damage, the off-site center near the Fukushima plant was not functional; thus, the center was moved to the Fukushima prefectural government office. There was sufficient direct communication between Tepco’s headquarters and the Fukushima nuclear power plant. There were, however, incredible difficulties in other communications; for example, data was transmitted by fax and handwritten letters, only exacerbating delays and confusion in the national response efforts.
Since March, the Japanese government has suggested the need to revise the act to include measures to identify less accident-prone locations for the emergency-response headquarters and local centers, as well as improvements to logistical and communications support among related organizations. The government has also suggested re-evaluating its system to respond to a combined emergency, such as the coincidence of a nuclear accident and a massive natural disaster. This will require appropriate communication tools, devices, and channels to obtain supplies and equipment needed during such an emergency, making a significant difference in prompt and effective responses. But in addition to these steps, there are several more that demand attention, including communications among nuclear organizations, information dissemination to the public, international assistance, and environmental monitoring and forecasting.
Divide labor, encourage communication
Within days of the Fukushima accident, it was apparent that responsibilities had not been clearly defined between the national and local nuclear emergency-response offices, between the national government and Tepco, or among the relevant agencies within the Japanese government. With no such system locked in place, when the earthquake and tsunami devastated the Fukushima plant and environs, there was incredible confusion and misunderstanding. Even something as critical as injecting seawater to cool the reactors was misperceived: Tepco understood that the national emergency-response headquarters had misgivings about injecting seawater due to criticality concerns, while the headquarters denied ever expressing such reservations. In the end, emergency-response employees injected the seawater without awaiting approval.
Within three months after Fukushima, the Japanese government announced its commitment to review and clearly define the roles and responsibilities of the relevant organizations, specifying tools to improve inter- and intra-agency communication and information-sharing.
Ensure public communication
For the residents outside the Fukushima prefecture, weak communication by the government and Tepco was a major concern—important information was not always provided in a timely manner. For example, the health impact of radioactive materials—specifically, the radiological protection guidelines established by the International Commission for Radiological Protection (ICRP)—is the most important information residents and citizens need; and these were not sufficiently explained during the disaster. At the press conferences, the government often stated that “there are no immediate health effects,” only creating public confusion, as it was unclear what kind of effects might be in store for the long term.
The Japanese government has noted that this was unacceptable and, in its report to the IAEA, recommended reinforcing rules to provide information on the accident status and response, as well as to present an appropriate explanation about the radiation effect to residents and citizens.
Prepare for international response
Immediately after the earthquake and tsunami hit Japan, the international community responded, offering disaster relief, nuclear expertise, and nuclear reactor equipment, among other things. The problem was that Japan could not appropriately respond, because it lacked a specific office to accommodate such assistance. Communication with the international community was not always sufficient, as was evident when discharging water with low-level radioactivity into the sea without promptly and adequately informing neighboring countries. The government has suggested it will work with the international community to improve the international notification system in order to provide faster and more accurate information.
Improve environmental monitoring
Because there was such scant information on the radioactive release source, it was felt that even the System for Prediction of Environmental Emergency Dose Information (SPEEDI)—which is intended to make immediate radiation dose projections after a release, as well as to provide evacuation advice—could not reliably predict the likely radioactive doses. The results generated by SPEEDI are now being disclosed, and it turns out to have predicted the dose rate well enough to have met the objective of helping with decisions about evacuation. In hindsight, therefore, the results could have been published at the onset of the disaster.4
As the accident extended into something more and more severe, the residents were evacuated or were advised to stay indoors for a long period. Finally, the government elected to lean on ICRP and IAEA guidelines, which set permissible dose limits during an emergency; these guidelines also established evacuation- and emergency-preparation areas. In the end, the size of the protection area set by the guidelines—a 20–30 kilometer radius from a nuclear power station—was considerably larger than that which was enshrined in Japanese law: a 3–10 kilometer radius.
The Japanese government has expressed plans to develop a way to effectively use SPEEDI and other systems, disclosing data, plans, etc. at the beginning of a severe accident; to establish a structure in which it will implement emergency environmental monitoring in a reliable and well-planned manner; and to create more efforts to define the evacuation areas and establish clear guidelines of radiological protection in a nuclear emergency.
Safety regulatory infrastructure
It should be noted that there wasn’t intentional disregard for citizens’ safety during the emergency but that a confusing, overly bureaucratic system clouded understanding as to whose responsibility it was to communicate messages. For example, NISA—which is part of the Ministry of Economy, Trade, and Industry (METI)—is responsible for safety regulation; however, METI is also responsible for developing the energy policy that promotes nuclear energy. The Nuclear Safety Commission, which is included in the Cabinet Office, is an advisory organ responsible for auditing (double-checking) the activities of NISA; and local governments and ministries are in charge of emergency environmental monitoring. Confusing? Yes.
The Japanese government has recommended streamlining the system and separating NISA from METI; it has begun reviewing what agency or ministry will be the central administration for nuclear safety and environmental monitoring. This may lead to a revision of the nuclear safety regulation, which, since the accident, has been deemed too complex and ineffective. In its report to the IAEA, the Japanese government recommended improving its nuclear safety culture using principles set out by the IAEA and returning to the basics of pursuing defense-in-depth as essential to ensuring nuclear safety.5
Though the infrastructure of the entire system is one that demands immediate attention, there are also serious issues that will need to be addressed once that new system is in place: the strengthening of legal structures and guidelines and the improvement of the nuclear energy workforce.
Establish and reinforce legal structures and guidelines
The Japanese government must re-evaluate measures against age-related degradation of the existing facilities to ensure structural reliability; it also must incorporate new knowledge and expertise (such as warnings presented by seismic and tsunami experts). The government has announced it will clarify technical requirements based on new laws and regulations, probably including “retrofitting” (i.e. applying new regulations to existing plants); it also plans to improve IAEA safety standards and guidelines by providing related data.
Maintain and strengthen human resources
It is now evident that, regardless of the future of nuclear energy in Japan, the country needs to maintain a skilled nuclear workforce for the foreseeable future, as safety must be ensured at the existing facilities, as well as off-site stations, at not only Fukushima but throughout the country. These industry-development measures should also work to ensure environmental clean-up efforts and residents’ safety. The government plans to create development measures for both nuclear operators and regulatory organizations, but it has not expressed what tactics it will use to execute this plan.
Looking ahead
Although the long-term impact of the Fukushima accident is not yet known, its short-term effects on Japanese nuclear programs are already quite significant. Sensing the likelihood of these effects on the public, within a month of the accident, the Japan Atomic Energy Commission (JAEC), an advisory organ responsible for overall nuclear energy policy (except nuclear safety), issued a public statement: “We are gravely concerned about this accident which can fundamentally undermine public trust in safety measures, not only in Japan but also in other countries” (JAEC, 2011a; see also JAEC, 2005, 2010, 2011b).
Recent public opinion surveys conducted by national media companies show that, since the accident, 74 percent of the Japanese population are in favor of “phase out” and “immediate shutdown” (Asahi Shimbun, 2011).
While there are 54 commercial nuclear power plants currently licensed in Japan, only 18 reactors are operating (14 units are shut down due to the earthquake, and 22 units are currently not in operation due to maintenance or other technical reasons). On May 6, 2011, Prime Minister Naoto Kan requested Chubu Electric Power to shut down the Hamaoka nuclear power station until new tsunami measures are in place. Since then, it has become more difficult to restart the plants that are currently shut down. The national government introduced “stress tests” similar to those introduced in the European Union, hoping to inspire public trust in nuclear safety.
And so the Fukushima Daiichi nuclear crisis continues. Many technical, social, legal, and economic hurdles must be overcome. Technically speaking, stabilizing the reactors and managing a large amount of contaminated water—more than 100,000 tons—are still grave challenges. Cleanup of the site, including a large amount of contaminated debris from the accident, is yet another immense challenge. And then there are the long-term challenges of decommissioning and dealing with the spent fuel in the storage pools and the damaged fuel in the reactors.
As is worth repeating, this crisis isn’t solely a lesson for Japan, but for all countries that have invested in nuclear power. The crisis need not be one of exasperation; it can be one of opportunity. Fukushima became a victim of nuclear disaster, but it can become a symbol of recovery.
Acknowledgements
This article is part of a special issue on the disaster that occurred at the Fukushima Daiichi Nuclear Power Station in March 2011. Additional editorial and translation services for this issue were made possible by a grant from Rockefeller Financial Services.
1
I would like to express my sincere appreciation for the generous assistance provided by many governments and the advice given by respected experts from around the world.
2
This article contains my personal observations based on the Japanese government’s report and other public information.
3
“Severe accident” is a type of accident that goes beyond design basis and creates extreme challenges to controlling the reactor, possibly resulting in core damage or core meltdown.
4
Following the Fukushima accident, local governments are now tasked with monitoring the environment in their areas; because equipment and facilities were damaged due to the earthquake and tsunami, appropriate environmental monitoring was impossible immediately after the accident.
5
The government has set up the “Investigation Committee on the Accidents at the Fukushima NPSs of Tokyo Electric Power Company,” chaired by Yotaro Hatamura, with three basic principles: independence, transparency, and comprehensiveness. The committee is expected to issue interim findings by the end of the year. Available at: http://icanps.go.jp/eng/.
References
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