Go-ahead given for construction of Pegasus uranium store

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The Office for Nuclear Regulation (ONR) has given permission for construction work to start on a radioactive materials store as part of 'Project Pegasus' at the Atomic Weapons Establishment (AWE), but has criticised AWE for “numerous instances” of failing to provide adequate information in the application to commence work.

The store will be used to store enriched uranium, used in the manufacture of warhead components and submarine reactor fuel, as part of Project Pegasus – the £600 million scheme to construct a new uranium components manufacturing facility at AWE Aldermaston.

AWE submitted a request for permission to commence work on construction of the store in December 2012, but was forced to resubmit the application in March 2013 after ONR wrote to AWE expressing concern at the quality of the submission and asked for it to be re-submitted.

ONR has now decided to allow work on the project to commence – but not without qualification.  The Licence Instrument issued by ONR allowing the work to go ahead highlights numerous shortfalls in the information provided by AWE to justify the start of work, and does not permit the use of prefabricated welded cages to reinforce the store's concrete structure – AWE's preferred method of construction.

Proposals to use the welded cages “came latterly to the attention of ONR”, who ruled that safety assessment work conducted to date does not cover the use of prefabricated cages.  AWE will not be allowed to employ the method until a satisfactory safety case has been submitted by AWE and approved by ONR.

ONR's Project Assessment Report outlining the decision to allow construction mentions “numerous instances where further information should have been included” in AWE's request to commence work.

Hazard analysis for the project related only to “fairly generic and static events, without apparent consideration of the occurrence of such events with the most pessimistic operating and environmental conditions”.  “More evidence” was needed to justify values used in calculations of the building's ability to withstand earthquakes.

The assessment report states that “in the main” AWE need to refine their fire modelling methodology, and that “some recommendations need to be addressed to enable future permissioning with regard to internal hazards”.

However, the shortfalls were not considered sufficient to prevent the issue of a Licence Instrument allowing construction work to commence, although “a number of recommendations” have been identified which “will need to be closed-out appropriately and in a timely manner”.

The ONR assessment concludes with a recommendation that AWE will need to “ensure that future safety case submissions include a comprehensive set of underpinning arguments and associated documentation that are clearly signposted within the headline documents”.

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