The Office for Nuclear Regulation (ONR) has required immediate safety changes to be made at the UK’s nuclear warhead assembly facility and has said that even with the changes operations at the site can only continue for a limited period of time. If sufficient progress is not made on reducing risk at the facility ONR have said that operations may need to stop altogether.
The UK’s nuclear warheads are assembled in the Assembly Technology Centre at the Atomic Weapons Establishment (AWE), Burghfield, using components manufactured at nearby AWE Aldermaston. The work is carried out in buildings known as ‘Gravel Gerties’ which are designed to collapse inwards and trap radioactive material if there is a partial explosion during the assembly process. Burghfield’s Gravel Gerties are thought to have been built in the 1950s. In May the National Audit Office revealed that a replacement building is six years late and is expected to cost £1.8 billion, an increase of 146% over the £734 million approved for the project in 2011.
There have been a series of announcements related to safety concerns at AWE. The news about the Assembly Technology Centre was released in ONR's annual report where it was also announced they will keep AWE Aldermaston and AWE Burghfield in ‘Special Measures’. This is the 6th consecutive year that Aldermaston has been in Special Measures, (formally known as ‘Enhanced Regulatory Attention’), and the 3rd consecutive year for Burghfield.
On the 25th July ONR announced that they will prosecute AWE for an electrical arcing incident in June 2017 when an employee was injured. ONR have also been forced to use enforcement action 5 times at AWE since 2016 over safety documentation problems and the failure to produce a plan to deal with 5,000 drums of nuclear waste stored at Aldermaston, though ONR says these safety issues have now been satisfactorily closed.
The threat over continued operations at the Assembly Technology Centre comes at a time when AWE are part-way through an upgrading to the UK’s stock of warheads. The Mark 4A warhead includes a number of updated components purchased from the USA including an arming, fuzing and firing system that increases its accuracy. The same system is being fitted to US nuclear weapons and some analysts have raised concerns that this increase in accuracy could have a destabilising effect.
The AWE sites are obliged to carry out a Periodic Review of Safety every 10 years. Approval by the regulator gives permission for operations to carry on at the facility until the next review is due. The review that ONR have rejected was submitted in September 2016 and if approved it would have permitted operations until 2026. ONR were originally due to give a decision by September 2017 but AWE’s failure to submit key documentation on time meant that the response was delayed and AWE were obliged to supply ONR with a statement to demonstrate that the facility would operate safely until the end of March 2018.
In 2008 it was revealed that safety concerns had meant warhead assembly/disassembly work in Burghfield had to be halted for the first time in AWE’s history due to safety concerns centred around the Gravel Gerties. At the time it was reported that more than 1000 safety defects had been discovered during safety inspections and deadlines for 300 improvements had been missed, including engineering failures in the Gravel Gerties. The decision to build a replacement facility appears to have been made around this time.
ONR decides on whether to give a site enhanced regulatory attention based on a judgement of overall hazard and risk. Sites in Special Measures are subject to more detailed inspections by the regulators, including visits focussing on specific issues. AWE has adopted a Strategic Improvement Plan with the aim of getting out of Special Measures by 2020. Among the issues covered by the plan are the management of safety cases, streamlining of documentation and key issue resolution.
ONR cited the continued use of aging facilities, delays in undertaking periodic reviews of safety, use of ageing production facilities and the fact that AWE is behind schedule in building new facilities and implementing upgrades when justifying the decision to keep AWE in Special Measures.