The Nuclear Decommissioning Authority

 

When Berkeley Power Station stopped generating electricity in 1989, work began on the decades-long, painstaking process of removing the remaining radioactivity and demolishing the buildings.

The first step was defuelling, which removes 99% of the radioactivity, and this had taken place by 1992. For the remainder, the target date for completion is towards the end of this century, a similar timeframe for all the Magnox plants that heralded the start of the UK's nuclear age.

Plans for decommissioning were already being prepared in the 1970s, just a few years after operations started in 1962. As the first nuclear plant to be built solely for commercial purposes and one of the first to close, Berkeley has led the way in many areas.

Its two concrete-lined ponds, which provided temporary cooling for the hot used fuel and associated radioactive debris, are the first in the UK to be completely drained and demolished. Approximately the size of an Olympic swimming pool, 25 foot deep and housed in a low-level building, the ponds were highly radioactive and presented a major challenge. Over a period of almost 10 years, contaminants were cleaned, the water drained down, surface concrete removed by ultra-high pressure water jets followed by planing, scabbling and the removal of ancillary equipment. Much of the work was carried out remotely to minimise risks to the workforce.

Finally, a huge tent, the largest scaffolded structure in Europe at the time, was erected to contain any airborne material while the buildings inside were demolished. Now, stone chippings mark the place where the ponds used to stand and signal the completion of the environmental restoration.

Another significant milestone will be reached later in the year when the twin reactor buildings are scheduled to be the UK's first to enter the final 'Care and Maintenance' Safestore state. After being sealed up, they will be left alone and monitored for around 70 years until the entire site is fully decommissioned in Final Site Clearance where it will be levelled and landscaped.

Before then, a more immediate source of excitement is the possibility of being able to use the pioneering MiniStores for storage of the intermediate-level waste that is held on-site in four subterranean vaults.

The original plan was to construct a £40 million specially shielded store to hold boxes containing the concrete-encapsulated material, but the advent of MiniStores raises the prospect of a more flexible and much cheaper option.

Site Director Sean Sargent told a recent meeting of local stakeholders that a two-year exploratory work programme had been approved by the NDA, which would assess the MiniStores' suitability for the specific conditions at Berkeley. He stressed that there were no foregone conclusions and that the original solution would still be available should the MiniStores ultimately fail to deliver.

"We're increasingly excited about this," he added. "But we do need to work out whether this is the best option."

The local community is due to be consulted over the next few months while data is collected and extensive environmental studies carried out. Meanwhile, piling work for the foundations of the ILW storage facility will continue as the MiniStores would also require a weather-proof building, though with less heavy shielding.