Nuclear safety officials have increased the emergency planning area for the Sizewell power station complex, but say the risk of a radiation leak from the coastal site has decreased.

After lengthy consultation, the Office for Nuclear Regulation (ONR) has decided to dispense with its circular 2.4 kilometre zone and to replace it with one based largely on postcodes.

This will mean that parts of the emergency plan zone will stretch up to around 3km from the power stations and both Leiston and the majority of nearby Aldringham will in future be included in it.

Plans will now have to be drawn up to evacuate both communities should an incident occur.

The ONR said the increase in the overall planning area does not reflect an increased risk to the public from the Sizewell site and “the overall hazard has significantly reduced”.

This is due to stringent safety measures at Sizewell B and also the defueling and decommissioning of Sizewell A, which is largely complete.

Sizewell B station director Jim Crawford said he was pleased that the ONR had responded to information supplied by EDF and Magnox which reflected the changes at Sizewell A and its decreasing risk and recognised there was no increased risk associated with Sizewell B.

He said: “We don’t see any change to our local emergency arrangements that we have in place to support the county council.”

EDF opened a new multi-million pound Emergency Response Centre last year at Sizewell to further enhance safety following the lessons learned from Fukushima, though it is hoped the centre will never be deployed, and was a further commitment to how seriously the company took its safety responsibilities.

ONR deputy chief inspector George Sallit said: “Our technical assessment of the hazards on the Sizewell nuclear sites confirms that the overall risk from the dual site has reduced and I believe that the revised REPPIR emergency planning area is in the best interests of public safety, demonstrating our commitment to continuous improvement.

“In applying our revised principles, ONR inspectors have not only assessed the operators’ technical reports but have also worked with Suffolk County Council and other agencies to ensure that practical considerations, relevant to the Sizewell area, have been taken into account when defining the area requiring an off-site emergency plan.

“This includes avoiding having an emergency planning boundary that unnecessarily cuts through small local communities.”

Suffolk County Council will now revise its off-site emergency plan in consultation with the other partners to ensure that robust arrangements are in place as appropriate.

Suffolk Coastal MP Therese Coffey said: “I welcome the fact the zone has been extended to include Leiston and Aldringham.

“Sizewell B carries a lesser risk than Sizewell A but the Emergency Zone will remain at the wider level and be extended in key areas. Extra protections have also already been brought in post Fukushima”.