Updating of the public dose assessment approach for decommissioning related releases from the Ignalina NPP

Abstract

The methodology used at the Ignalina NPP for the assessment of the public exposure from radioactive releases to the environment is based on the use of so called “release-to-dose calculation factors” (RDFs). Application of RDFs is straightforward and in practice is used both to assess impacts from measured releases and to assess impacts from planned activities. The set of radionuclides and RDF values corresponding to them for operational releases were approved by the regulatory authorities.The decommissioning-related radiological characterization of the plant components and wastes revealed that the available set of RDFs is not sufficient for the decommissioning needs. To overcome this, a simplified approach has been proposed for the estimation of the missing RDF values. However, estimations using the simplified approach might be very inaccurate and not necessary conservative.This paper addresses the current practice of the dose assessment for releases from the Ignalina NPP and the necessity of extension of the available set of RDFs. New RDF values for the calculation of radiological impacts due to airborne releases from the power units and waterborne releases into Lake Drūkšiai are proposed for the decommissioning-relevant radionuclides. The significance of individual radionuclides in releases to the environment during decommissioning is discussed.