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Dealing with the ageing process

Nuclear; Decommissioning; Half a century after the nuclear age dawned, ageing reactors are exceeding their life expectancy and becoming uneconomic to run. Controlled decommissioning is a priority.

The UK's first generation of nuclear reactors is facing imminent closure. Three have already been wound down and another eight are soon to follow. It is a picture being reproduced across Europe and the US has been phasing out nuclear energy for well over a decade.

Managing the closure and safe disassembly of obsolete civil nuclear infrastructure is a vast task, offering spectacular long-term business prospects. In the next 20 years, according to nuclear services and generating giant BNFL's most conservative estimates, the UK, western Europe and the US will represent well over £160bn worth of decommissioning work. Green lobby group Friends of the Earth says the market is nearer £200bn.

It is harder to pin a price on decommissioning work needed in the former Soviet Union, largely as it is often unclear who is going to pay for the work. There can be no doubts that the scale is huge.

The European Commission is just about to launch three international decommissioning committees to deal with defunct reactors in Lithuania, Bulgaria and the Slovak Republic. Finance is still to be finalised, but the eight projects will each be worth between £110M and £180M a year. Work could take up to three decades.

Meanwhile, the Ukrainian government has announced it will close the remaining operational reactor at Chernobyl next year. Two other reactors are already closed and awaiting demolition. Combined decommissioning of the three will have an annual value of up to £500M. Work to stabilise the sarcophagus around Chernobyl's stricken No.4 reactor is set to overrun its £480M budget.

Services already provided to the nuclear energy sector by players like BNFL translate well to decommissioning, says BNFL design team leader Ian Massey. Techniques and technologies for handling and reprocessing fuel are crucial for the safe extraction, processing and storage of rods and waste from reactor cores. A good understanding of the issues and processes involved are necessary for even basic civils work in a nuclear environment. In decommissioning, expertise and experience are equally vital.

But civil decommissioning is not limited only to reactors. There is a legacy of waste, old storage facilities, reprocessing and waste vitrification plants, and laboratories to take care of. Led by the UK Atomic Energy Authority, work is going ahead at Dounreay to clear out and make safe a shaft in which waste was stored after its licence was revoked by industry regulator the Nuclear Installations Inspectorate. Dounreay is also the site of decommissioning of a prototype fast breeder reactor and test facilities.

At Dounreay there is 'years of work still to be done', says a spokesman at trade body the British Nuclear Industry Forum. The same is true for the La Hague plant in France, built in the late 1960s to reprocess fuel from fast breeder reactors.

Five decommissioning projects - one of which is La Hague - are being sponsored as pilot studies by the European Union. Three reactor types are represented. These projects are key to providing an industry, hitherto engaged in construction, operation and maintenance of nuclear plant, experience of taking it apart.

There are two routes to decommissioning reactors. As on the UK's Windscale advanced gas reactor decommissioning project, they can be taken apart in their entirety in one concerted, albeit extensive, campaign. An alternative, known as safe storage, leaves the highly radioactive core in place to decay over the course of 50 or 100 years.

But even this hands-off approach can call for extensive engineering to reduce the amount of maintenance necessary. To provide safe store requires removal of all anciliary structures surrounding the core and construction of new shielding around the reactor building to protect it from the elements.

Either way, preparing for safe store poses no mean engineering challenge in its own right.

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