James M. Acton, Mark Hibbs
CARNEGIE PAPER, MARCH 2012

Public sentiment in many states has turned against nuclear energy following the March 2011 accident at Japan’s Fukushima Daiichi Nuclear Power Station. The large quantity of radioactive material released has caused significant human suffering and rendered large stretches of land uninhabitable. The cleanup operation will take decades and may cost hundreds of billions of dollars.

The Fukushima accident was, however, preventable. 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. The plant would have withstood the tsunami had its design previously been upgraded in accordance with state-of-the-art safety approaches.

The methods used by TEPCO and NISA to assess the risk from tsunamis lagged behind international standards in at least three important respects:

  • Insufficient attention was paid to evidence of large tsunamis inundating the region surrounding the plant about once every thousand years.
  • Computer modeling of the tsunami threat was inadequate. Most importantly, preliminary simulations conducted in 2008 that suggested the tsunami risk to the plant had been seriously underestimated were not followed up and were only reported to NISA on March 7, 2011.
  • NISA failed to review simulations conducted by TEPCO and to foster the development of appropriate computer modeling tools.

At the time of the accident, critical safety systems in nuclear power plants in some countries, especially in European states, were—as a matter of course—much better protected than in Japan. Following a flooding incident at Blayais Nuclear Power Plant in France in 1999, European countries significantly enhanced their plants’ defenses against extreme external events. Japanese operators were aware of this experience, and TEPCO could and should have upgraded Fukushima Daiichi.

 

Steps that could have prevented a major accident in the event that the plant was inundated by a massive tsunami, such as the one that struck the plant in March 2011, include:

  • Protecting emergency power supplies, including diesel generators and batteries, by moving them to higher ground or by placing them in watertight bunkers;
  • Establishing watertight connections between emergency power supplies and key safety systems; and
  • Enhancing the protection of seawater pumps (which were used to transfer heat from the plant to the ocean and to cool diesel generators) and/or constructing a backup means to dissipate heat.

Though there is no single reason for TEPCO and NISA’s failure to follow international best practices and standards, a number of potential underlying causes can be identified. NISA lacked independence from both the government agencies responsible for promoting nuclear power and also from industry. In the Japanese nuclear industry, there has been a focus on seismic safety to the exclusion of other possible risks. Bureaucratic and professional stovepiping made nuclear officials unwilling to take advice from experts outside of the field. Those nuclear professionals also may have failed to effectively utilize local knowledge. And, perhaps most importantly, many believed that a severe accident was simply impossible.

In the final analysis, the Fukushima accident does not reveal a previously unknown fatal flaw associated with nuclear power. Rather, it underscores the importance of periodically reevaluating plant safety in light of dynamic external threats and of evolving best practices, as well as the need for an effective regulator to oversee this process.

 

Read the FULL REPORT below: