Safety watchdog: Atomic Weapons Establishment 'exposed people to risk'

An investigation by the government's nuclear safety watchdog has found “clear evidence” that the structure of a nuclear processing facility at the Atomic Weapons Establishment (AWE) has degraded to the extent that "normal operations can no longer be justified".

The Office for Nuclear Regulation (ONR) concluded that “people were exposed to risk” by AWE’s failure to adequately inspect and maintain the structure of the building at its main processing site at Aldermaston.

ONR has issued AWE plc, the company responsible for operating the UK's nuclear weapons factories, with a formal Improvement Notice requiring the company to complete a programme of remedial actions to tackle the problems by the end of 2013.

ONR's thirteen page report into the case concluded that an inspection of structural steelwork on one of the older manufacturing facilities at Aldermaston during August 2012 found an “unexpected area of corrosion at the base of one of the steel columns”.  Normal operations in the facility were suspended and further inspections revealed the presence of corrosion on a “significant number” of the building's steel support columns.

The building is described as a 'Class 1' structure, the "highest and most important classification for a nuclear structure” and “the most important to safety".  Although the building is not identified in the ONR report, it is widely believed to be the A45 facility, which conducts uranium manufacturing operations at Aldermaston and is currently working on a production programme for highly enriched uranium fuel for the nuclear reactors which will power the Royal Navy's future Astute class submarines.   

Structural surveys revealed that the presence of corrosion did not render the building unsafe under normal circumstances, but that the ability of the structure to withstand seismic events or extreme weather - particularly high winds, snow, or storms - had been reduced.   ONR's report concluded that normal operations in the facility “could no longer be justified".  Radioactive materials were removed from affected areas of the building and work was limited to operations deemed necessary in the interests of safety, including repair work.

AWE has initiated a programme of inspections for buildings of similar design and age across their estate, and the findings and implications of this work will be considered separately by ONR.

Although the ONR investigation found that AWE did not act recklessly or ignore safety standards, the regulator concluded that “people were exposed to risk by AWE’s failure to adequately maintain the class 1 structure”. The investigation found “clear evidence” that AWE had failed to comply with the conditions of its nuclear site operating licence because arrangements for the inspection and maintenance of a nuclear structure were not adequate to prevent its degradation, resulting in risks to nuclear safety.  

In accordance with the Health and Safety Executive's Enforcement Policy Statement, inspectors judged that prosecution of AWE would be “inappropriate” although enforcement action was deemed necessary to ensure that the necessary improvements were made.

The regulator has issued a formal Improvement Notice requiring AWE to complete inspections of the building and develop a credible programme to repair the building.  AWE must also conduct a review to learn lessons from the incident, and review its plant maintenance schedule.  A deadline of 31 December 2013 has been set for completion of the work.

Although there is no previous history of this type of structural degradation at AWE, ONR wrote to the company in 2011 raising concerns following the discovery of degradation in concrete structures in the warhead assembly / disassembly at AWE Burghfield.

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