Thursday, May 17, 2012
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Nuclear accident risks
Post Fukushima, every one is concerned about nuclear accidents. It added a new dimension. Rightly or wrongly more people characterize nuclear power plants as terribly unsafe. Similar perceptions prevailed over fifty years ago when governments attempted to commercialize nuclear power.
The myth of reactors exploding like nuclear bombs clouds the reality. Often, the public tend to be either pronuclear or antinuclear. Most of the operating nuclear power reactors depend on unforgiving technology. It is a complex technology. The complexity is to ensure safety. Nuclear operators must be eternally vigilant
Suppose a chemical plant handling large quantities of a highly toxic gas or a modern nuclear power plant is about to be involved in a serious accident. If you offer this writer a choice, he will remain near the nuclear power plant. It will not be foolhardy. He is confident that the containment will survive. Even if there is a radioactive release, he knows that he will have enough time to get away! The toxic gas release will kill its victims in seconds!
Can we estimate risks from nuclear reactor accidents? Nuclear industry has clocked over 14,000 reactor years of safe operation.
Fifty years ago, our knowledge about nuclear reactor risks was very scanty. Reactor designs were less robust. Can we ignore the gigantic strides in safety improvements taken by the nuclear industry which provides 13.5% of world’s electricity continuously, reliably and exceedingly efficiently?
The US nuclear power industry learnt many lessons from the Three Mile Island accident. These led to making of US nuclear power plants efficient and safe. In 1980, the average capacity factor (the ratio of electricity produced compared with the maximum electric power a plant can produce, operating at full power all the year around) for US nuclear power reactors was 56.3%; it increased steadily and remained consistently above 90% for the past several years
The owners of TMI-1 modified the plant and revamped the training and operating procedures in light of the lessons of TMI-2.
Since then, TMI-1 clocked many creditable records. In October 1998, TMI employees completed three million hours of work without a lost-work day accident. In 2008, it clocked a capacity factor of 106.7%. In 2009, TMI-1 completed the longest operating run of any light- water reactor in the history of nuclear power worldwide — 705 days of uninterrupted operation. NRC renewed the licence to operate TMI-1 till 2034.
In USA, with an average annual capacity factor of 91.5%, nuclear power plants are well ahead of coal (7%), natural gas (42%), wind (31%), hydro (27%) and solar (21%).
It was believed that the record performance of all US nuclear power plants post TMI may gradually remove the stigma attached to them because of the TMI accident. But the Fukushima accident is casting its shadow worldwide.
No one appreciates nuclear accident risks quantitatively. Recently, the Organization for Economic Co-operation and Development Nuclear Energy Agency (OECD NEA) published a report titled “Comparing Nuclear Accident Risks with Those from Other Energy Sources.” The analysis is meant to help policy makers understand how accident risks are managed at nuclear power plants and illustrate that with a comparison of risks from other energy sources (World Nuclear Association Release September 3, 2010).
The agency collected data on every accident causing five or more immediate deaths in the energy industry between 1969 and 2000. During that period, there were 1,870 such severe accidents worldwide resulting in 81,258 deaths. In the nuclear industry, there was only one accident, the one at the Chernobyl nuclear power plant. Thirty one plant and emergency workers died in the accident. At Fukushima, nobody died due to the nuclear accident. Two workers died due to the tsunami and one worker died in a crane accident during the earthquake.
Possible long-term fatalities due to the accident at Chernobyl continue to be controversial. Based on reports by the World Health Organization, European Commission, International Atomic Energy Agency and Russian authorities, OECD estimated that the Chernobyl accident may eventually cause about 9,000-33,000 deaths over the next 70 years. Possible long-term deaths due to Fukushima accident will be much lower.
Specialists arrived at these numbers based on the controversial Linear No Threshold (LNT) concept which states that any radiation dose however small has a finite effect and it varies linearly with dose. The concept has not been proved irrefutably. It was a practical concept accepted to enforce radiation protection.
The report cautioned that if the same logic is applied, the background radiation to which every one is normally exposed will cause 50 million deaths in the same population in 70 years. “There is no way to definitely confirm these figures for Chernobyl,” the report added.
According to OECD, the estimated latent potential death rate for the Chernobyl accident is the same as the immediate deaths resulting from the largest dam failure (the Banquiao/ Simantan failure in China in 1975 claimed 29,924 lives). Many assume potential deaths as real deaths
Premature deaths caused by particulates from fossil fuel generation are thought to be around 288,000 annually worldwide (OECD Environmental outlook).
“Overall, the likelihood of an accident and radiological release is 1,600 times lower than it was when the first reactors were built,” the report concluded. This is primarily because of engineering safety improvements among other factors
The report added that more than 2,500 people are killed annually in energy-related severe accidents. Though nuclear power was perceived to be high risk, it caused far fewer deaths than any other energy source.
Public confidence in nuclear operations will increase if trust in the regulators increases. There is also a direct correlation between public trust and awareness of the technology. “Openness and transparency in government decisions about the use of nuclear power and in the licensing process are vital elements in improving public confidence,” the OECD report concluded. Unfortunately, in public debates including those by lawmakers, no one highlighted the enhanced safety levels achieved in the operation of nuclear power plants after the Chernobyl and TMI accidents.
The writer is a former Secretary, Atomic Energy Regulatory Board, India.