The March 2011 accident at Japan’s Fukushima Daiichi Nuclear Power Station has shaken confidence in nuclear safety. Carnegie’s James Acton and Mark Hibbs explain why and how the Fukushima accident was, however, preventable.

The Fukushima Accident 

  • Its Effects: The accident at Fukushima Daiichi released large quantities of radioactivity into the environment, causing significant human suffering and rendering large stretches of land uninhabitable. The cleanup operation will take decades and cost tens, if not hundreds, of billions of dollars. 

  • Nuclear Safety: Unsurprisingly, the Fukushima accident has reignited the ever-contentious debate about the safety of nuclear energy. Critics argue nuclear power is too dangerous to be acceptable. In assessing how safe nuclear can be, it is useful to ask whether an accident was preventable. The two major nuclear accidents prior to Fukushima, Chernobyl in 1986 and Three Mile Island in 1979, were both preventable. 

  • Fukushima was Preventable: Acton explained that one year on, there is a growing body of evidence that suggests the accident was the result of failures in hazard assessment and nuclear plant design. Had the plant’s owner, Tokyo Electric Power Company (TEPCO), and Japan’s regulator, the Nuclear and Industrial Safety Agency (NISA), followed international best practices and standards, it is conceivable that they would have predicted the possibility of the plant being struck by a massive tsunami. Even if they had failed to do so, upgrades in plant design in accordance with state-of-the-art safety approaches would have prevented the tsunami from sparking a major accident. The Fukushima accident—like the Chernobyl and Three Mile Island accidents—was therefore preventable.

Hazard Prediction

According to Acton and Hibbs, the methods used by TEPCO and NISA to assess the risk from tsunamis lagged behind international standards in three critical ways:

  • Historical Evidence of Disasters: Acton concluded that TEPCO and NISA did not give sufficient attention to historical evidence of large earthquakes and tsunamis in the region surrounding the plant. Specifically, evidence that the region had been inundated about once every 1,000 years by tsunamis (most recently in 869 AD) was not followed up appropriately.

  • Tsunami Modeling Procedures: There appears to have been deficiencies in the tsunami modeling procedures used by TEPCO, Acton said. Most importantly, TEPCO did not follow up with sufficient alacrity on preliminary 2008 simulations that suggested the tsunami risk to the plant had been seriously underestimated, he added. These simulations were not reported to NISA until March 7, 2011.

  • NISA Inattentiveness:  A fundamental principle of nuclear safety is the existence of an effective and independent regulator to set safety rules and to ensure compliance with them. Japan’s regulators, however, appear to have been inattentive to tsunami risks, Acton said. NISA failed to review simulations conducted by TEPCO and to foster the development of appropriate computer modeling tools. 

How Could the Plant Have Been Protected?

  • Protecting the Plant: Hibbs explained that there were several steps that could have prevented a major accident in the event of massive tsunami. TEPCO, encouraged by Japanese regulators, could have taken some or all of the following actions:

    • Protected emergency power supplies, including diesel generators and batteries, by moving them to higher ground or by placing them in watertight bunkers.

    • Established watertight connections between emergency power supplies and the plant.

    • Enhanced the protection of seawater pumps, which were used to transfer heat from the plant to the ocean and to cool diesel generators, and/or constructed a backup means to dissipate heat.

  • International Best Practices: Hibbs contended that during the four decades that the Fukushima Daiichi was in operation, regulators and nuclear power plant owners elsewhere in the world were establishing requirements and configuring nuclear power plants in ways that could have potentially have saved the Fukushima Daiichi station from disaster. He highlighted standard design features in European plants in particular that would have better protected Fukushima Daiichi against a station blackout, severe flooding, and the loss of the ultimate heat sink.

Underlying Causes

While there is no single reason for TEPCO and NISA’s failure to follow international best practices and standards, Acton and Hibbs outlined a number of potential underlying causes:

  • Regulatory Quality and Independence: NISA’s lack of independence from the government body responsible for promoting nuclear power deterred NISA from asserting its authority to make rules, order safety improvements, and enforce its decisions, Hibbs said.

  • Ignoring Safety Threats: Hibbs contended that NISA and TEPCO neglected the threat of a tsunami and also, more broadly, the possibility that power would be lost at a nuclear power plant for a prolonged period. 

  • Risk Assessment: Hibbs pointed to Japan’s nuclear culture and its attitude towards risk. Japanese authorities exhibited a reluctance to evaluate serious risks, which may reflect a more general Japanese bias against open discussion of worst-case scenarios or contingency preparations, he added.

  • Corporate and Nuclear Culture: Japan’s nuclear energy sector has had a tendency to be insular, elitist, and unwilling to take advice from experts outside the nuclear field, Hibbs explained.