GB law places a legal duty on the relevant local authority to produce plans to deal with off-site emergencies at nuclear sites, working with the site operator and other agencies including ONR. This requirement is captured in the Radiation (Emergency Preparedness and Public Information) Regulations 2019 (REPPIR). ONR formally assesses the adequacy of these arrangements which must include a test of the off-site emergency plans every three years.
Should a radiation emergency be declared, the local authority will activate its off-site emergency plan to protect the public within a pre-determined area known as the Detailed Emergency Planning Zone (DEPZ). These local arrangements are well established and publicised to any residents within the DEPZ. REPPIR19 also requires Outline Planning Zones (OPZs) for some sites which require strategic level planning beyond the DEPZ for extremely unlikely but more severe events.