Unhappy anniversary | Fukushima Daiichi crisis

Views and reviews

1 June 2012

The one-year anniversary of the Fukushima Daiichi accident prompted analysis and opinion from societies and associations. Will Dalrymple reviews the reviews.

The most interesting analysis comes not from the usual regulators, international associations and utilities who have already published significant reports (available via ), but rather from non-governmental organisations, professional associations and less-well-known bodies. (Other anniversary-related analysis, including the IAEA International Experts Meeting convened in March about the incident, and the US-based Electric Power Research Institute’s report “Fukushima Daiichi Accident—Technical Causal Factor Analysis”, came in too late to be included and will be covered in future months.)

The most commonly-blamed cause of the Fukushima Daiichi accident were the reactors’ inadequate flood protection defences against a major tsunami. Typical was UK chief regulator Mike Weightman’s view, stated in the March 2012 issue of Physics World that “ultimately, it appears that the Japanese authorities underestimated the hazard presented by the tsunami.” (He added that they did show adequate resistance to the seismic ground motion). The American Nuclear Society’s “Fukushima Daiichi: ANS Committee Report” said that the design-basis tsunami was too low. Anti-nuke campaigner Arnie Gunderson of Fairewinds Associates suggests that the utility dragged its feet in implementing tsunami defences in ‘The echo chamber: regulatory capture and the Fukushima Daiichi disaster,’ a section of Greenpeace’s report “Lessons from Fukushima.”

Deputy director of Russian research body the Kurchatov Institute of Atomic Energy Jaroslav Shtrombah blamed not only the wave height flood defence, but also the location of emergency power supplies, in an interview published by the Russian Centre for Energy Expertise.

In an anniversary press conference, the World Nuclear Association’s director-general, John Ritch, was scathing about the poor defences of emergency diesel generators: “They did not do a good job of thinking through threats they might face. The minimum necessary at any power plant is to have reliable back-up cooling. They failed to achieve that. And it looks like a ridiculous oversight in retrospect.” And the problems at Fukushima had nothing to do with the age of the reactors, he emphasised. It was all down to “the fundamental error of not flood-proofing the diesel generators.” He added: “The reactors might have been built yesterday, but with flooded diesel generators they would have had the same problems.”

Also highly critical are the recommendations from the Japanese government’s advisory committee for the prevention of nuclear accidents, whose executive summary’s second point reads: “The overconfidence of the government and the licensee in their safety measures could not prevent [a] severe accident, which cause[d] massive discharge of radioactive materials to the environment and destroy[ed] communities of local citizens.” (See also box, p. 17). The report, published in December, but not seen by NEI magazine until now, is available via www.tinyurl.com/7h56lb7.

Risk-informed regulation

The American Nuclear Society argues that the root of the problem was an inadequate risk-informed process. It writes: “The tsunami design bases for the Fukushima NPPs were not consistent with the level of protection required for NPPs. If the return period for a tsunami of the magnitude experienced in Japan is as short as reported (once every 1000 years), a risk-informed regulatory approach would have identified the existing design bases as inadequate...Although it is very difficult to deal with low-probability events, this is the perspective needed for a risk-informed treatment of natural-phenomenon hazards. Such an approach to regulating hazards from extreme natural phenomena should be undertaken.”

(A 1000-year recurrence interval was predicted in a study of archaeological evidence of three tsunamis in the region, which occurred at approximately 1000-year intervals. However, the ANS authors did not provide a source by press date).

The ANS report says that this risk-informed regulatory process should also be applied in the USA. “The scope of reactor safety design and regulation should be reviewed to consider the adequacy of design bases for natural-phenomenon hazards and the need for extension of the design basis in a graded manner, using risk information, into what have previously been considered beyond design-basis accidents (BDBAs).”

It points out that its support for risk-informed regulation was the first recommendation of the NRC staff’s Fukushima Near-Term Task Force report last year. That internal report complained that the US regulatory approach, particularly of low-probability hazards, so-called ‘beyond design-basis’ issues, has evolved over time in a patchwork way. The internal report concluded that the NRC’s approach was incomplete without a strong programme for dealing with the unexpected, including severe accidents. Although this kind of scrutiny is applied to severe accidents in new plants, it is not for currently-operating plants. The internal report argued that this should be changed. That recommendation was controversial at the time. It has been marked for long-term action, and a proposal for dealing with long-term actions is due in July 2012, but exactly how this issue will play out remains unclear.

Gunderson at Greenpeace argues that industry perceptions of risk are out of touch with society. “For decades, the nuclear industry and its regulators have convinced themselves that the low probability of component failures somehow means that the nuclear technology is a low-risk industry...the majority of nuclear risk studies calculate the frequency or probability of events while avoiding true risk assessment that incorporates serious consequences. Such convoluted modelling distorts the public and the institutional understanding of the risk posed by nuclear power stations and encourages risky behaviour.”

In a speech to the Platts Nuclear Energy Conference in February, NRC chairman Gregory Jaczko unconsciously echoed the same theme while pondering where risk-informed regulation, which he admits is a very young activity in the USA, could take the industry in 20 years. He pointed out that current concepts of radiation exposure risk deal only with biology: prompt and latent radiation health effects. By that token, Fukushima was not a significant incident, and its occurrence was acceptable, because few people, if any, were harmed by radiation. Obviously most people today would say that Fukushima was more significant than this. So the existing risk criteria are too basic, Jaczko argues, and miss out societal factors. The evacuation of large populations for an extended relocation leaves its marks, psychologically in individuals, and socially in groups of individuals. He concludes that maybe there are better risk metrics than current ones such as core damage frequency or large early release frequency. He proposes that a better future risk metric might be the risk of an accident that requires an evacuation.

The US industry body the Nuclear Energy Institute has launched a programme to respond to post-Fukushima regulatory issues (profiled p.19), and published a short document and infographic outlining its approach for the general public.

Social factors

Social factors in Japan come under criticism by many analysts. A World Energy Council report (‘Nuclear energy one year after Fukushima’) published results of a 2011 survey that suggested that although respondents were confident that their own national nuclear authority is independent, resourced, transparent, and able to enforce standards, they all showed a high degree of uncertainty about the state of nuclear governance in other countries.

That attitude appears elsewhere. The Kurchatov Institute official criticises the efficacy of the Japanese nuclear regulator. Both the ANS and Gunderson from Greenpeace cite the Japanese culture of ‘amakudari’ as a form of regulatory weakness. According to this traditional Japanese practice, government officials retire to comfortable positions at supposedly private-sector utilities.

However, the reports diverge in their conclusions, according to their attitude toward nuclear energy. Gunderson argues that the lack of independence of the regulator is a typical example of an institutional failing. When the IAEA’s own review processes praise Japan’s regulatory structure, as it did in a 2007 Integrated Regulatory Review Service report, he questions the IAEA’s own independence from larger political forces. He concludes that this is the sort of failure that lies behind most nuclear accidents, and which is systematically underrepresented in models of accident risk.

He writes: “[Probabilistic safety assessments] cannot provide meaningful estimates for accident frequencies (probabilities), since they cannot take into account all relevant factors (for example, they cannot cover inadequate regulatory oversight) and the factors that are included are beset with huge uncertainties (for example, regarding earthquakes).”

It is interesting that the latter half of his point agrees with the position of the ANS on risk-informed regulation quoted above; both state that risk assessment of low-probability events is difficult.

The ANS report does criticise social factors in Japan: for example, it says that confusion about chain of command within TEPCO contributed to the worsening of the accident. But it does not share Gunderson’s confidence in criticising the Japanese regulator. Instead, it pleads that cultural differences between East and West should be respected:

“By U.S. standards, this system of shared regulatory authority and economic benefit would be viewed as flawed. Yet, this system allowed the Japanese to develop 58 reactors at 18 sites in a country whose national psyche is still affected by the atomic bomb. The Japanese created a system that promoted and enforced the safe and peaceful use of nuclear energy, and the Japanese had an enviable safety record. Unlike the United States, where states are independent governments, the Japanese prefectures are jurisdictions of the central government with sub-prefectural structures down to districts, townships, and villages. The hierarchical distribution of authority suits the Japanese culture, and the effectiveness of this governance structure was demonstrated during the evacuations around the Fukushima Daiichi NPS and in response to the earthquake/tsunami.”

After this praise, however, the ANS report then goes on to heavily criticise the Japanese government about what it saw as poor communication during the crisis.

Emergency response

Several anniversary reports describe the trauma of the tsunami and the relocation, and discuss the nature of the Japanese emergency response. The first two sections of the Greenpeace report, for example, cover emergency management issues such as evacuation, potassium iodide, and compensation. The personal stories of survivors are recounted in another book, written by anti-nuclear Tokyo university professor emeritus Shunji Murai, and published in the Netherlands as Higher Ground: Learning from the East Japan Tsunami and Meltdown at Fukushima NPS (Geomares, ISBN 978-90-806205-0-6). He takes a strong antinuclear tone (for example, ‘Any ruler who loves their [sic] people and land will put a stop to nuclear power generation’) and argues that the Japanese government’s 28 suggestions about how to prevent a similar accident, in its 2011 report to the IAEA, were ‘excellent in principle’, but ‘neither feasible nor practical.’ I feel that some of his conclusions were dated and insufficiently technical.

On the Fukushima Daiichi anniversary, Laurent Stricker, chairman of World Association of Nuclear Operators, commented that its organization has changed its focus from accident prevention to accident prevention and mitigation. WANO also announced plans to work with the IAEA on utility station peer-review missions.

A Physicians for Social Responsibility report says that emergency evacuation plans in the USA do not consider station blackout, nor does the US have an adequate real-time information system to direct emergency responders and the public. The PSR report is entitled “Nuclear power and public health: lessons from Fukushima, still dangerously unprepared.”

The issue of openness and communication comes up in the anniversary-inspired remarks of the chairman of the Japan Atomic Industrial Forum, Takashi Imai, who tacitly acknowledges its importance in rebuilding the Japanese industry’s reputation: “...We in the industry must take to heart the results of accident investigations and ask for wisdom both inside and outside the country to further enhance safety and support the recovery of Fukushima. We also have to disclose information as much as possible, contributing to discussions in society. This is the only way to regain trust.”

Author Info:

This article was first published in the May 2012 issue of Nuclear Engineering International

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ANS argues that Fukushima workers should have prioritised depressurisation

Only a few paragraphs of the ANS report cover analyse what TEPCO workers should have done, given the benefit of hindsight. First, the report praised the dedication and stoicism of site staff who carried out their duties and more whilst facing great adversity. It went on to argue that the site's emergency management strategy was misguided.

"In Unit 1, loss of DC power for both motive force and instrumentation due to flooding substantially increased the difficulty of controlling the accident. It is unfortunate that in addition to the design-basis tsunami being too low, additional flood protection for the batteries was not provided. Only the isolation condenser system was available as a makeup system, and because of lack of instrumentation, it was not clear how well it was working. Priority was given to venting the containment when it should have been given to assuring core cooling, such as by restoring the isolation condenser system at reactor pressure or by lining up alternative water sources into the RPV and depressurizing the reactor system so that low-pressure pumps could be used. At the time of this writing, there is no record of any attempt to depressurize the RPV throughout the event.

"The containment vent design, with valves that need DC power and compressed air or nitrogen to operate, plus an in-line rupture disk (with a setpoint greater than the containment design pressure) that cannot be bypassed, led to containment pressures well in excess of the design pressure because of delays. Most likely, the source of the hydrogen in the reactor building was leaks in the containment due to the high pressure, and perhaps also high containment temperatures that could have led to deterioration of the major seals (drywell head cover, and equipment and personnel airlocks). Another possible source could also have been leakage past containment isolation valves.

"In Units 2 and 3, the operators should be commended for keeping the RCIC and the HPCI systems operating as long as they did. We note that many probabilistic risk assessments performed on BWRs have shown the dominant core melt scenario to be SBO with eventual failure of the RCIC/HPCI systems, thought to be in ~8 hours because of a number of potential failure mechanisms. However, in that time period, no attempt was made to prepare for depressurization of the RPV until these systems failed, and because of DC power failures and issues with providing alternative compressed nitrogen, depressurization to allow alternative water sources was delayed. Such accident management strategies need to be thought out in advance given the evolution of an accident."

Greenpeace report Greenpeace report
ANS report ANS report
Book on Fukushima Book on Fukushima
World Energy Council World Energy Council

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