standard Addressing the risks of nuclear power: a lesson from Fukushima

The Fukushima nuclear disaster is indeed one of the greatest nuclear accidents in history.  Nuclear power is a complicated technology.   On the one hand it promises a relatively ‘safe’ and ‘cheap’ source of energy, on the other it carries a number of risks including nuclear waste disposal, threat of radioactive contamination and the proliferation of nuclear weapons.  Whether nuclear power is genuinely safe, cheap or clean has been debatable since government initiatives throughout the world first pushed for nuclear as the answer to the world’s energy problems.  There are clearly a number of questions that arise including what deems a nuclear power plant to be safe?  What are the risks involved in the life cycle of a nuclear reactor?  And how should nuclear technologies be governed by society?

The ‘Three Mile Island’ and ‘Chernobyl’ nuclear disasters are both iconic in terms of humanity’s use of nuclear energy, not to mention its role in warfare during the infamous bombings of Hiroshima and Nagasaki in World War II by the US government.  Indeed, while nuclear power has been utilised in countries throughout the world with little to no major problems, or at least none that have been publicised, it is when things go wrong that nuclear receives the most attention.  Despite numerous attempts from governments, scientists, engineers and the nuclear industry to convince the public that nuclear power is a safe and reliable source of energy, the potential dangers posed by nuclear power often appear too great to comprehend.  It seems that what proponents of nuclear energy have failed to do in the past and present is communicate honestly and effectively the risks associated with nuclear power.  Are the risks sometimes simply ignored due to the seeming unlikelihood of the worst possible scenario occurring?  In the case of the recent disaster in Japan, possibly.

More than a decade before the earthquake in Japan, in 1990 the US Nuclear Regulatory Commission actually identified likely risks due to seismic activity (earthquake) including loss of onsite and offsite power and failure of coolant pumps.  Here are some excerpts from that report:

Chapter 3, p. 6

Seismic Accident Frequency Analysis

The relative contribution of classes of seismically and fire-initiated accidents to the total mean frequency of externally initiated core damage accidents is provided in Figure 3.4.  As may be seen, seismically initiated loss of offsite power plant transients and transients that (through cooling system failures) lead to reactor coolant pump seal LOCAs [Large and small loss-of-coolant accidents] are the most likely causes of externally caused core damage accidents.

Chapter 3, p. 10

Risk (core damage frequency) reduction importance measure (internal events)

The risk-reduction importance measure is used to assess the change in core damage frequency as a result of setting the probability of an individual event to zero. Using this measure, the following individual events were found to cause the greatest reduction in the estimated core damage frequency if their probabilities were set to zero:

Loss of offsite power initiating eventThe core damage frequency would be reduced by approximately 61 percent.

Failure of diesel generator number one to start. The core damage frequency would be reduced by approximately 25 percent.

Probability of not recovering AC electric power between 3 and 7 hours after loss of offsite power. The core damage frequency would be reduced by approximately 24 percent.

Failure to recover diesel generators. The core damage frequency would be reduced by approximately 18 to 21 percent.

Uncertainty importance measure (internal events)

A second importance measure used to evaluate the core damage frequency results is the uncertainty importance measure. For this measure, the relative contribution of the uncertainty of groups of component failures and basic events to the uncertainty in total core damage frequency is calculated. Using this measure, the following event groups were found to be most important:

Probabilities of diesel generators failing to start when required;

Probabilities of diesel generators failing to run for 6 hours;

Frequency of loss of offsite power; and

– Frequency of interfacing-system LOCA.

It should be noted that many events each contribute a small amount to the uncertainty in core damage frequency; no single event dominates the uncertainty.

Now of course the tsunami was responsible for shutting down the diesel generators that led to the disaster, rather than the earthquake itself.  But nonetheless an understanding of the risk to the generators was disseminated, but whether it was read or taken seriously is another matter.  It doesn’t end there.  TEPCO also has a history of falsifying data.  Last February  TEPCO submitted a report to the government of Japan admitting that the company had made fake inspection and repair reports for many years, which is documented in the bookIn Mortal Hands: A Cautionary History of the Nuclear Age by investigative reporter Stephanie Cooke.  This is clearly a much more complicated case than what has been portrayed.  Fukushima I was commissioned in 1971.  Operating at 4.7 GWe (gigawatts), it is one of the 15 biggest nuclear power plants in the world, or was…  Now it has become one of the biggest topics in the nuclear power controversy, especially in terms of how Japan and other countries generating nuclear power should proceed.

Combine corporate mismanagement, if not corruption, with the risks posed by having not one but six nuclear reactors located near a major fault that was known to expect large magnitude earthquakes at some point in the future, and disaster seems inevitable.  This particular disaster, like many, was not merely caused by unforeseen events alone, but also deliberate negligence.  In some ways this event seems to share similarities with the BP Deep Horizon Oil spill, but maybe it’s too presumptuous to compare them at this stage.  Although, both seem to exemplify how the arrogance of large corporations can actually exacerbate risk through secrecy, denial and idleness.  If companies refuse to act on risks they know to exist, it does not always equal disaster, usually they just go on without notice, but all it takes is one.

This is why risk management today is of the utmost importance.  If a risk is identified to be potentially lethal to the stability of any system (especially one that generates nuclear power!) then it needs to not only be taken seriously, but planned for well in advanced.  There are no guarantees about whether any technological infrastructure will not fail at some point in the future.  The question of who decides what risks should be paid attention to and how needs to be examined more closely because in the case of Fukushima the risks don’t only involve industry, government or even Japan itself, but the rest of the world, as nuclear power has been at the centre of plans for future energy generation for some time.  Researchers could look towards a new pathway in energy research that deals specifically with risk to help design more effective and resilient systems to generate electric power.


Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants — Final Summary Report (NUREG-1150, Volume 1). NRC. 1990

Tokyo Electric Power Company. Wikipedia.


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