Pools of danger By Charles D. Ferguson -17 April 2011

The Fukushima Daiichi nuclear crisis in Japan has underscored the dangers of storing highly radioactive spent fuel in pools of water that are susceptible to breaches from natural disasters and hydrogen explosions from accidents. The crisis should serve as a wake-up call for governments and industry to take action to reduce the risks of spent-fuel storage.

Unfortunately, spent-fuel storage has been “an afterthought,” as Ernest Moniz, Director of the Energy Initiative at MIT, puts it. In dozens of countries, tens of thousands of tons of highly radioactive material has been kept in buildings that provide little of the usually rigorous protection surrounding radioactive material in reactors’ cores. Pools have become overcrowded in many countries, owing to the lack of permanent repositories for nuclear waste. No country has opened such a repository, although Sweden has made significant progress in doing so. The hazards of pools for spent nuclear fuel have been known for many years, but little action has been taken to alleviate the risks. One notable exception has been Germany. About 25 years ago, the German government began requiring spent fuel to be well protected. The older spent fuel that has cooled for about five years is placed in hardened, dry storage casks, and the younger, more radioactive, and hotter spent fuel is cooled in pools of water surrounded by strong containment structures. These measures cost more money, but they afford much greater protection against accidents, disasters, and terrorist attacks.  Is it worth it?

A 2003 study, led by Robert Alvarez, a former official at the United States Department of Energy, estimated that a worse-case terrorist attack could drain cooling pools, resulting in spent fuel rods heating up and possibly combusting. That, in turn, would cause substantial amounts of radioactive material to be released if containment structures are breached, potentially resulting in an area of contamination greater than that caused by the Chernobyl accident in 1986. Despite this alarming conclusion, the study did not prompt the US Nuclear Regulatory Commission to order utilities to remove spent fuel from overcrowded pools at more than 100 US commercial reactors. It did, however, spur the preparation of a US National Academy of Sciences’ report, which concluded that “successful terrorist attacks on spent fuel pools, though difficult, are possible.” While the report did not recommend placement of older spent fuel into dry storage casks, it did advise the less expensive method of rearranging spent fuel in the pools so that hotter, newly discharged fuel would be surrounded by cooler, older spent fuel. Doing so would likely prevent a fire. The report also called for water-spray systems to fill up draining pools, but made this conditional on a cost-benefit analysis conducted by each plant.

Is reprocessing spent fuel the answer? While China, France, India, Japan, and Russia have favored reprocessing in order to recycle plutonium for new fuel, this has not solved the waste problem, because the resulting spent fuel is usually not further recycled. Instead, it is stored in spent-fuel pools. Recycling proponents want ultimately to build a fleet of fast neutron reactors that could consume the plutonium and other fissionable material. But these reactors have experienced safety problems and are more expensive to operate than current reactors. Use of plutonium fuels also increases the risk of nuclear-weapons proliferation. Several decades from now, reprocessing might offer a safe means of spent-fuel disposal. In the interim, the most promising method is to use dry storage casks, which, according to technical studies, provide up to 100 years of safe and secure storage.

But industry has expressed concern that each storage cask costs more than $1 million, and that a typical plant’s total costs thus could be tens of millions of dollars. The Alvarez study estimated a cost of $3-5 billion for the entire US reactor fleet, which is the largest in the world. This would be the major one-time cost. After that, the costs would be a few hundred million dollars annually. 

To minimise this risk, casks should be developed that can easily be transferred to a secure interim storage facility while permanent repositories receive approval. We should not wait for the next Fukushima Daiichi to act on reducing the risks of spent fuel.

Charles D. Ferguson, a physicist and nuclear engineer, is the president of the Federation of American Scientists and the author of the forthcoming book Nuclear Energy: What Everyone Needs to Know.

© Project Syndicate

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