Guest contribution by Martin Forwood
The recent finding of the U.K. Nuclear Installations Inspectorate (NII) reminded of the poor safety record at the Sellafield plutonium facilities. On 22 January 2010 NII found out that critical supply of cooling water to the high-level waste (HLW) storage tanks was disrupted in an incident similar to the one that took place in April 2009, when the cooling supply was disrupted for several hours by workers operating the wrong valves. The severity of the consequences, had the duration of cooling water disruption been extended, are such that the scenario is deemed 'the worst credible accident' for Sellafield and features as such in the area's Emergency Plans. After the April 2009 incident, the NII imposed new procedures to prevent it re-occurrence, but it occurred again just nine months later. The latest event is now under full NII and internal investigation.
In January 2009 a leak of radioactive condensation, via a ventilation duct in the Magnox reprocessing plant was reported. Incidentally, the leak was reported on the same day that Prime Minster Gordon Brown was visiting the site to promote nuclear power and congratulate the workforce on its expertise. Investigation of that incident, rated at Level 3 on the International Nuclear Event Scale (INES), discovered that the leak had been ongoing and un-noticed for 12 months. In another incident in April 2009, two thermos-sized canisters of 'legacy wastes' were mysteriously lost from a storage cave where human entry is forbidden because of high radiation levels. The canisters were traced weeks later and their disappearance was attributed to mistaken accounting.
Whilst many of the recent incidents and events have been, for Sellafield, routine occurrences - equipment failures, electrical fires, spillages and worker injuries - others have posed significant risk of worker contamination. In late 2008 a Board of Investigation was launched into the uncontrolled movement of two shielded trap doors in the site's vitrification plant where the liquid HLW is converted into glass form. Within the operating cells, radiation levels are such that, had workers been inadvertently exposed whilst the shielding doors were incorrectly set, they would have received fatal doses within minutes. In a separate incident twelve months previously, two contract workers were contaminated internally whilst drilling a section of contaminated floor concrete in the Product and Finishing Store where Plutonium Contaminated Wastes (PCM) are drummed up. In the ensuing legal case brought by the Health & Safety Executive, Sellafield Ltd was convicted and fined £75,000 in 2009 for breaching safety laws - the Judge commenting on the Company's significant failings to adequately assess the hazards and risks involved by the drilling operation, and the failure to provide proper training for the contract workers.
Constantly in the news for just such accidents, nuclear industry supporters will take equally little comfort from Sellafield's overall commercial operations performance. The THORP plant, once the flagship of the site but now running some six years behind schedule, lurches from one stoppage to another and is currently limited to reprocessing 200-300 tonnes of spent fuel annually - around a quarter of its original design throughput. The threat of closure still hangs over the troubled Sellafield MOX Plant (SMP) as it struggled to produce just eight MOX fuel assemblies (some 4 tonnes) between 2007 and 2009 - against a design production rate of 120 tonnes per year.