The recovery of highly radioactive leakage resulting from a leak discovered April 18 within the fuel clarification cell of the Thorp reprocessing facility at the UKs Sellafield site began late last week, and will take around four weeks to recover a British Nuclear Group official told Bellona Web.
On April 18, a camera-based investigation of the clarification cell revealed that a pipe leading from one of the reprocessing facilitys so-called Accountability Tank had ruptured and caused a leak of some 20 tonnes of uranium and plutonium dissolved in nitric acid onto the for of the clarification cell. The clean up operation began May 19. There are as yet no cost estimates as to how much the clean up effort will cost
The BNG official sad that the incidentwhich ranked a 3corresponding to a serious incident on the International Nuclear Event Scale (INES)that conditions within the cell remain stable and safe. The 3 rating on the INES sale is one step short of a nuclear accident without significant off-site risk.
Thorps fuel clarification cell comprises a stainless steel-lined space 60 metres long, 20 metres wide and 20 metres high and its concrete walls are 2 to 3 metres thick to absorb radiation. Another BNG official, Sellafields spokesman Nigel Monckton, said the cell was designed to withstand the possibility of a leak and, because stainless steel does not dissolve in nitric acid, the leak has been contained.
Thorps raw materials are the used fuel rods from nuclear power stations. After receipt at Thorp, they are stored for several months to allow the radioactivity of short-lived fission products to decay to safer levels. The 1-metre long, 1-centimetre diameter tubular rods are then cut up into small chunks and lowered in baskets into strong nitric acid.
The uranium, plutonium and fission products dissolve and the remnants of the steel rods are removed. But the fluid remaining from the process, called liquor, still contains small shards of steel, or tailings, from burrs created as the rods were chopped up. So the liquor must be centrifuged to get rid of the steel contaminants, a process called clarification. It is at this clarification stage that the leak occurred.