11 - Safe enclosure and entombment strategies in nuclear decommissioning projects

Abstract

Examples are presented of two stragtegies for decommissioning of nuclear facilities: the nuclear power plants (NPPs) dodewaard (Netherlands), Vandellós-1 (Spain), Kozloduy (Bulgaria), lingen (Germany) and Berkeley (UK) for safe enclosure; and facilities at the hanford and idaho National laboratory sites and the P reactor at the Savannah river Site (all USA) for entombment. Reasons are given for selecting the deferred dismantling option (which may be divided into radiological reasons on the one hand and economic, social and technological reasons on the other hand), of the preparatory activities for reaching safe enclosure conditions and of the management of a safe enclosure or entombment period. National approaches in selected countries are compared, showing that countries with a small decontamination and decommissioning (D&D) programme with no repository generally favour safe enclosure, whereas no country with a large D&D programme opts for deferred dismantling as the preferred strategy, and several Western countries have modified D&D programmes in favour of early dismantling. The chapter closes with a discussion of challenges, lessons learnt and future trends, highlighting the decay storage of large components as a quite recent development where segmenting of highly activated or contaminated components is separated from the dismantling of the facility itself by removing the unsegmented components and placing them in a dedicated storage facility for later segmentation, decontamination and possibly clearance. This combines the advantages of both the early and the deferred decommissioning strategy.