Estimation and sensitivity analysis of operational intervention levels for the early phase of radiological emergencies involving radioactive releases

Abstract

Radiological emergencies involving any likely atmospheric release of radioactive material in the public domain are quite a challenge to respond to and manage. Such conditions require a quick and confident response. One such response involves using pre-planned operational intervention levels (OILs) to trigger certain protective actions or groups of actions. OILs are typically derived for nuclear emergencies, whose values cannot always be directly used in a radiological incident. Therefore, in this study, OILs were derived for the early phase of a radiological emergency involving ground- and skin-deposition exposure scenarios. The methodology is an adaptation of an internationally recommended method for nuclear emergencies, with modifications to suit radiological incidents. The derived OILs for the radiological emergency were compared against the internationally recommended values to attest their adaptability. Nominal range sensitivity analysis was performed over 14 factors used in the methodology, which provided broad insights into their influence. Moreover, exhaustive sampling of the extreme values of these factors helped to derive operational margins for the OILs to cover all possible scenario variations. Based on this analysis, generic OILs for the early phase of a radiological emergency are proposed, such that the projected doses are well below the respective generic criteria, ensuring justification on radiological grounds.