Sellafield’s THORP reprocessing plant, closed in April last year following a major accident involving the spillage of 18,000 litres of highly radioactive nitric acid, is unlikely to be in a position to re-start until the back end of this year at the earliest. Despite the ongoing assessment since last May of a number of repair options by British Nuclear Group (BNG) who operate THORP on behalf of the Nuclear Decommissioning Authority (NDA), no preferred option has yet been officially submitted by BNG to the Nuclear Installations Inspectorate (NII) for approval.
NII approval is required before the plan can be submitted by BNG to the NDA. As owners of the plant, the NDA has confirmed that the next opportunity to consider any re-start proposal will not be until its Board meeting in March. Even if approval is then granted by the Board, the repair option currently understood to be favoured by BNG will take many months to effect and will be subject to continuous scrutiny from NII inspectors at every stage. Repairs are unlikely therefore to be completed before the Autumn at the earliest, and a re-start by the end of the year or early 2007.
The NII’s formal investigation into the THORP accident, which could see BNG face a number of prosecutions, is now complete but still has to undergo further vetting from the Health & Safety Executive (HSE). Publication of the findings is not expected for some time. At Government level, THORP’s future is already subject of discussions between NDA and Ministers.
CORE’s spokesman Martin Forwood said today “ THORP’s repair options are clearly a self-inflicted headache for BNG . With many technical, regulatory and cost hurdles ahead, the plant is miles away from any re-start. The longer it remains closed, the more of a liability it becomes on the NDA’s books and to the UK, – and the weaker the case for re-opening it. We believe the interests of the British taxpayer are best served by putting THORP out of its misery now”
Already some three years behind its original reprocessing schedule, and now set to fall 4 -5 years behind because of the accident, THORP still had around 1250 tonnes of Baseload (first ten years of operation), fuel to reprocess when it was forced to close in April last year. This consists of around 700 tonnes of LWR fuel from European customers and around 500 tonnes of British Energy’s (BE) AGR fuel. A further volume of fuel, mostly sourced from BE, is already contracted for the follow-on period (post- Baseload).
The options for repairing THORP consist of variations on repairing the fractured pipe work where it joined one of two accountancy tanks located in the Feed Clarification Cell, or by-passing the pipe work and affected tank/s altogether. Much will depend on the extent of damage inflicted by the nitric acid on the steel framework which supports both accountancy tanks, and also the level of faith that can be placed on the robustness of the remaining pipe work within the cell. BNG’s preferred option until now has been to bypass the damaged pipe work/tank, though the delay in submitting the option officially to the NII suggests that either a complete re-think or major revisions have been necessary. An engineering assessment of all repair options, commissioned by the NDA last year from the Washington Group, concluded that the one favoured by BNG presented risks which, if unresolved, would ‘result in significant delays in resuming THORP operations’.