Nuclear safety event reported every fortnight at Atomic Weapons Establishment

An official record of nuclear incidents has revealed that over the last three years over eighty safety-related events were reported to government safety inspectors by the factory where Britain's nuclear weapons are designed and built – an average of more than two every month.

A detailed new report published by the Office for Nuclear Regulation (ONR), the government agency responsible for overseeing the safety of the nuclear industry, has for the first time published comprehensive information about the numbers of nuclear safety events at atomic sites across the country.

The ONR report lists 3,866 'unintended events' which occurred at UK nuclear sites between 1 April 2001 and 31 March 2015.  The majority of these events took place at civil nuclear sites, but 311 took place at sites involved in the Ministry of Defence's nuclear weapons and submarine programme.  Of these by far the largest number – 137 – took place at the Atomic Weapons Establishment (AWE) Aldermaston, where the UK's nuclear weapons are manufactured.

In addition to the occurrences at Aldermaston a further 29 nuclear safety events at the nearby AWE Burghfield site, where warheads are assembled and disassembled for maintenance, were reported to the regulator over the same fourteen year period.

In April 2012 ONR introduced improvements to its event reporting and recording arrangements, and a more detailed data set is available over the three year period from 1 April 2012 to 31 March 2015.  During this period 82 events at AWE Aldermaston were reported to ONR – on average more than two occurrences every month.  Among these were 22 cases where plant operating rules, limits or conditions were breached, three cases where personnel received an intake or suspected intake of radioactive material, and two fires.

Other events reported at Aldermaston over the three years included site-wide loss of power supplies, alarm failures, situations where waste items were not stored in accordance with arrangements, and a case where a member of staff took on duties which they were not authorised to undertake.  The most serious incident at Aldermaston – and  the most serious safety problem recorded at any UK nuclear site since 2009 – occurred in 2012, when the discovery of corrosion in structural steelwork resulted in the closure of the secret A45 building which makes enriched uranium components for nuclear warheads and fuel for nuclear submarines.  

The event was rated as 'Level 2' on the INES international scale for recording the seriousness of nuclear events, corresponding to an 'incident' where 'significant failures' in safety provisions occurred, but with no actual consequences.

Over the latest three year period covered in the report, AWE's nuclear safety performance has remained static, rather than improved.  28 events were reported in 2012-13, 25 in 2013-14, and 29 in 2014-15.   Because of the failure to improve performance AWE is currently under regulatory 'special measures' for the third year running, requiring “an enhanced level of regulatory attention” from ONR.

The number of unintended nuclear safety events reported to regulators by AWE far exceeded those at other defence nuclear sites.  Over the 14 years from 2001 to 2015 137 events were recorded at AWE Aldermaston, with a further 16 at AWE Burghfield.  77 events were recorded at the Devonport Royal Dockyard, where the Royal Navy's nuclear powered submarines are maintained; 43 at the BAe Systems shipyard at Barrow-in-Furness where submarines are built; and 29 at the Rolls-Royce nuclear plant in Derby where submarine reactor components are manufactured.  

This is the first time that information about many of the events described in the ONR report has been released to the public.  ONR's quarterly site reports do not routinely record information about safety events reported to the regulator, and members of Local Liaison Committees at nuclear sites are only informed of events at the discretion of site operators.

The report does not give comprehensive figures for safety events at the Clyde and Rosyth naval bases, nor for the Vulcan submarine nuclear reactor test establishment at Dounreay, as these sites are regulated by the Ministry of Defence, not ONR.  Neither are figures for breaches of nuclear security nor safeguards related events (measures to verify that the UK is in compliance with its international obligations not to use civil nuclear materials for nuclear weapons purposes) included in the report.

The majority of the events recorded in the ONR report are minor in nature, but nine incidents which took place between 2001 and 2015 are judged to have been of greater significance by ONR.  None of these more significant events had any detrimental effect on public safety or the environment.

See also this related article on the Ferret news website.

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