Office for Nuclear Regulation

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Thermal Oxide Reprocessing Plant (THORP) leak investigation and consent to restart

NII issued a Consent on 09 January 2007 to allow THORP to reopen because it is satisfied that the licensee, British Nuclear Group Sellafield (BNGSL) has done all the work necessary to ensure it can be restarted safely. The actual date on which reprocessing of fuel at THORP recommences is a matter for BNGSL. HSE/NII will continue to regulate BNGSL to ensure safety is maintained across the Sellafield site and elsewhere.

Background

In April 2005, a camera inspection of the THORP Feed Clarification Cell identified the failure of a nozzle on an accountancy tank. This inspection also identified a quantity of liquor had leaked on the cell floor. Production operations in the cell ceased on the discovery of the liquor and have since remained embargoed across the whole of THORP, with the exception of work carried out to return the liquor to primary containment and to understand the reasons for the failure.

NII issued a notification on 09 January 2006 under Licence Condition 21(8) notifying the licensee to submit the safety case for the modified THORP and not to commence movement of fuel from the Feed Pond to the Shear Cave without its Consent. BNGSL applied for a Consent to commence movement of fuel from the Feed Pond to the Shear Cave in THORP, on 14 December 2006.

Reports

HSE has published a report on its invesigation into the leak which describes in detail how the leak occurred, how it was discovered and why it was not detected earlier, together with background information on the plant. It outlines 55 recommendations and actions arising from the investigation and discusses lessons for BNGSL and the wider nuclear industry.

NII has also produced a report describing NII's assessment of BNGSL's application for consent to restart THORP, which includes consideration of BNGSL's response to the 55 recommendations.

Press releases: