Like any technological production facility all operating nuclear plants will eventually reach the end of their working lifetime. When nuclear plants are retired they must be safely decommissioned to completely remove and dispose of any radioactive contamination.
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Britain has accumulated a large historic legacy of nuclear decommissioning liabilities from its nuclear development programme over the past six decades. Britain's Atomic Energy Research Establishment, AERE Harwell was set up in February 1946 to launch the civil nuclear power programme. Britain's first experimental nuclear reactor GLEEP was built at Harwell in 1946.
Decommissioning technologies used by workers to clean up plants such as robotics, scabbling and plasma cutting equipment are perhaps becoming standardised and commoditised. But there is relatively little agreed standardisation of decommissioning management models today. In an important sense each nuclear plant is somewhat unique, so each facility is tackled as a unique technical challenge.
Nuclear decommissioning involves the dismantling of radioactive plant and equipment followed by treating, packaging, storing and then eventually disposing of the radioactive waste produced. These processes are radiologically hazardous, technically complex and therefore expensive. Britain's intensive nuclear development programme undertaken rapidly after World War II has left a large civil nuclear clean-up bill, presently estimated by the Nuclear Decommissioning Authority to be £85 billion as of July 2009.
The bill is particularly large because many nuclear plants have only recently retired within the past decade while some older shut-down plants have been mothballed rather than fully decommissioned. Reactor decommissioning is normally carried out in three separate stages. Stage one decommissioning, reactor defuelling involves the complete removal of spent nuclear fuel from the reactor core and draining reactor coolant. Stage two decommissioning, reactor dismantlement involves the removal of internal plant and equipment and dismantling the reactor core and fuel handling equipment. Stage three decommissioning, demolition involves the complete dismantlement and removal of the reactor containment vessel and concrete bioshield back to its previous greenfield or brownfield condition.
In practice British energy utilities have opted to mothball reactors for about 80 years rather than fully decommission them, a strategy known as safestore.
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