Recommendations on the effectiveness of sheltering as a protective action in the UK.

To mitigate exposure of the public during an accidental atmospheric release of radioactive material, protective actions may be implemented. Sheltering can have a protective effect against both external and inhalation exposure pathways. This paper seeks to quantify the radiological protection offered from sheltering inside the types of buildings where individuals spend most of their time. Findings from other studies by way of a literature review are combined with modelling performed by the authors to assess the radiological protection offered were an individual to shelter inside a residential building. Housing stock and environmental conditions typical of the UK are considered. For the effectiveness of sheltering against external gamma irradiation from deposited material and material in the plume, best estimate location factors of 0.15 are recommended. For the effectiveness of sheltering against exposure from inhalation of the plume, a best estimate dose reduction factor (DRF) of 0.6 is recommended. These recommended values supersede previous recommendations on the effectiveness of sheltering as a protective action in the UK. The quantification of the effectiveness of sheltering, by way of location factors and a DRF, will better inform the process of determining urgent protective actions as part of the emergency planning required under the Radiation (Emergency Preparedness and Public Information) Regulations 2019 and will be of value when undertaking emergency response assessments.