Читать книгу Industrial and Medical Nuclear Accidents - Jean-Claude Amiard - Страница 46

The Sellafield site is the main complex of the British nuclear power sector. Originally named Windscale, it was renamed Sellafield following the serious accident at battery 1 involving plutonium for military use in 1957 [AMI 19]. The site borders the Irish Sea in the county of Cumbria in north-west England, near the town of Seascale. It now includes 400 buildings spread over 10 km² and employs about 10,000 people. Among the facilities is a fuel processing and high-level waste storage plant called THORP (Thermal Oxide Reprocessing Plant). It is designed to process both British and foreign fuels using a different process than the one used at La Hague (PUREX).

A first level 3 incident occurred in 1992 with the release of nitrated plutonium into a containment cell in the fuel reprocessing facility.

On April 19, 2005, 83,000 liters of radioactive material were discovered in a reinforced concrete enclosure at this plant, which followed a pipeline rupture that had not been detected for several months. About 200 kg of plutonium in nitric acid solution had flowed along a tank and accumulated in a drip pan (large collection tank for flow fluids) with a risk of criticality accident. The investigation concluded that the uranium and plutonium had flowed for about 9 months on the ground and then into a sump. The British Safety Council (HSE/ND4) has published a 28-page report [HSE 05]. The company, prosecuted for non-compliance with three authorizations concerning “safety, mechanisms, devices and circuits”, “operating instructions” and “leaks and losses of radioactive materials or radioactive waste”, had to pay £500,000 in fines plus approximately £68,000 in procedural costs. About 19 tons of uranium and 160 kg of plutonium (out of 200 kg according to the IRSN [IRS 12a]) dissolved in nitric acid were recovered by pumping into the reservoir’s sump outside the plant. According to the IRSN ([IRS 12a]), these failures were caused by “excessive confidence in the plant design” and “an insufficient safety culture”. The accident was classified as a level 3 accident on the INES. A similar plant in La Hague has modified its procedures to prevent this type of accident.

As a result of this accident, the THORP was closed from April 2005 to July 2007 and will be finally closed in 2018 after the completion of contracts, and then dismantled.