New hazard assessments published by the Atomic Weapons Establishment (AWE) for the Aldermaston and Burghfield nuclear sites suggest that the impacts of a radiation emergency at either site would extend over smaller areas than currently defined in emergency plans, raising fears that emergency planning areas may be reduced in size.
AWE plc has published new hazard assessment and risk evaluation reports for each site in accordance with the requirements of the Radiation Emergency Preparedness and Public Information Regulations 2001 (REPPIR), which will be used to define the size of 'offsite emergency planning areas' within which precautions may be necessary to protect members of the public from the effects of radiation.
The size of the emergency planning areas are decided by the Office for Nuclear Regulation (ONR) in consultation with West Berkshire Council, which is responsible for preparing an off-site emergency plan for the areas surrounding AWE sites. Currently the areas extend three kilometres from the centre of AWE Aldermaston and one and a half kilometres from the centre of AWE Burghfield.
The assessment for AWE Aldermaston concludes that a radiation emergency is “reasonably foreseeable” at the site. The maximum best estimate radiation dose to a member of the public from a reasonably foreseeable radiation emergency at AWE Aldermaston has been estimated to be 16.9 milliSieverts. Should a radiation emergency occur, AWE estimates that the impact would extend to 1.925 kilometres from the centre of the zone.
A radiation emergency is also reasonably foreseeable at AWE Burghfield, where the maximum best estimate radiation dose to a member of the public from a reasonably foreseeable radiation emergency has been estimated as 424 milliSieverts. A radiation emergency at Burghfield would have an impact extending to a distance of 976m from the centre of the site.
The newly calculated areas of impact are both well within the limit of the emergency planning zones currently set by ONR. However, the assessment reports published by AWE do not explain why they are smaller than the current limits or give details of the calculations or assumptions used to derive the new figures. Requests for the publication of such information have been refused on security grounds on previous occasions.
In 2013 the regulator considered that a technical case had been made to reduce the size of the emergency planning zone at AWE Aldermaston but following consultation with West Berkshire Council it was agreed that the zone should continue to extend 3 km from the centre of the site and be kept under review in the future.
ONR is expected to publish its decision on determination of the site of offsite emergency planning areas for the two AWE sites in the New Year.