Legacy work

Decommissioning essentially starts after fuel rods and other concentrated sources of radiation have been removed from the site. This reduces the amount of residual radiation to less than one per cent of that during operation in the case of a nuclear power station.

In fact, much of the decommissioning process uses well-established demolition techniques. There is of course one major added complication to take into account with nuclear decommissioning: the hazard of radiation release.

With this in mind, there are three main recognised decommissioning strategies currently in use: immediate decontamination and dismantling (DECON); safe storage (SAFESTOR); and entombment (ENTOMB). Since the last is an emergency measure to encase the whole structure in concrete, it can be discounted for the UK.

Under DECON, everything is decontaminated to a level that permits the removal of regulatory control shortly after the shutdown of operations. The advantage is that the site is freed quicker and at least some of the previous workforce can be retrained for decommissioning. However, more waste is produced and workers are exposed to a greater radiation hazard.