The devastating earthquake and subsequent tsunami which wrought much destruction to north east Japan on March 11th 2011 triggered a nuclear emergency at Fukushima which has had consequences on nuclear policy much further afield: Germany has announced that it will abandon plans to use nuclear power in the future.
Fukishima was directly struck by a 14m tsunami wave which breached the 9m sea defences and the region was also at the epicentre of aftershocks. The plant survived a worse natural disaster than it was designed to withstand and the only recorded fatalities were as a result of drowning rather than a nuclear incident. Whilst the nuclear reactors failed safe, in the aftermath of the disaster, cooling to the reactor and fuel storage ponds was lost, resulting in partial meltdown of some fuel rods and explosions which ruptured the environmental containment of some reactors.
In the current issue of the Bulletin of The Atomic Scientists, July 2011, Associate Professor of Environmental Science And Policy at George Mason University, Allison Macfarlane argues that the storage solutions for long-term nuclear waste produced by a nuclear power plant is often a last minute decision. It must not be. If a sceptical public is to be convinced of the merits of nuclear energy as a low carbon power source, the issue of long-term storage of waste must be decided from the outset.
Macfarlane points out that it is surprisingly common for the nuclear facilities to become overburdened with spent fuel for their reactors in intermediate storage facilities (cooling ponds). For instance, such storage facilities at South Korea's four nuclear power plants will be exhausted within the next decade. New capacity in the United Arab Emirates will bring four reactors on-line, but according to Hans Blix, UAE's International Advisory Board chairman and a former Director General at the IAEA, "The question of a final disposal plan is open and more attention should be spent on deciding what to do."
In a light water reactor, the typical lifetime of a fuel element bundle is between four and six years. The spent fuel must be cooled in a storage pond before unused fissile uranium can be recycled. A storage pond is about 10m deep and filled with borated water (which absorbs neutrons released by the fuel, preventing a chain reaction from occurring) which also serves to absorb thermal energy produced in the fuel rods. Water from the pond re-circulates through a cooling facility.
It has become politically and economically difficult to recycle spent uranium (only a small proportion of the fissile uranium is actually burned-up during the fuel's stay in the reactor) and this has led to intermediate storage ponds being used to store fuel for longer than originally envisaged - consequently, storage capacity is approaching limits in many places. Some US cooling ponds hold four times the amount of fuel originally envisaged for them. Around the world, there is more fuel in cooling ponds than loaded into reactors.
Cooling ponds were never intended to be long-term storage facilities. Fukushima reminded the world of the danger that could be caused by a failure of the cooling systems - either to a storage pond or a shutdown reactor.
Macfarlane explains that: "countries with nuclear power programs need a medium-term strategy for spent-fuel storage prior to the long-term plan for spent or high level waste disposal. Though difficult, the disposal of high level nuclear waste is possible and a clear strategy to develop a repository combines both technical and societal criteria in a phased approach."
When one looks at footage of the destruction caused by the Japanese earthquake and tsunami, it is remarkable that Fukishima survived nature's destructive power. If badly shaken public (and political) confidence in nuclear power as part of the energy basket is to be restored, resolution of the problems of storage of high level waste must be addressed and lessons must be learned from the failure of the cooling system at Fukushima.
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