Radioactive sludge has been transferred out of the Pile Fuel Storage Pond (PFSP) at the UK’s Sellafield site, the Nuclear Decommissioning Authority (NDA) and Sellafield Ltd announced on 20 December. The project is ten years ahead of schedule and well under budget at half the expected cost of GBP200m ($246m), they said in a joint statement. The sludge was formed from decaying nuclear fuel, natural growing algae and other debris, which has accumulated in the water of the 65-year-old PFSP. It must be removed so the facility can be safely decommissioned. The PFSP is one of the four ageing facilities at Sellafield which the NDA has prioritised for clean-up. The 100-metre long pond was originally used to store nuclear fuel used to make atomic weapons. All the bulk stocks of fuel have now been removed, leaving sludge as the biggest remaining radioactive hazard.
The project is being delivered for half the predicted cost. A ten-year project to dewater the pond will start in 2019, while sludge is still being removed. NDA CEO John Clarke said: "This pond was not designed with decommissioning in mind, and therefore we welcome this work by Sellafield Ltd to begin safe removal of sludge, which is a key step in making the site safer. The removal of the sludge contributes to achieving our overall goal of risk reduction by placing radioactive material and substances under more modern storage arrangements until it is ultimately moved to a Geological Disposal Facility." He added that sludge accounts for a third of the pond's remaining radioactive content, after 70% was removed earlier this year with the completion of fuel exports.
The first 500-litre drum containing the mud-like substance has been moved to an encapsulation plant where it will be grouted, rendering the waste passively safe, before being processed into a storage state, ready for final disposal in a geological disposal facility. The initial sludge removal involves pumping the material into a purpose-built treatment plant next to the pond, before its transfer to the drum filling plant. It will take several years to remove all of the sludge in the pond, the statement said.