Development of a Preliminary Performance Assessment Methodology for Design and Siting of a LLW Repository in Italy
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Development of a Preliminary Performance Assessment Methodology for Design and Siting of a LLW Repository in Italy
Piero Risoluti 1, Giancarlo Ventura1 and Piercarlo Ciabatti 2 1 ENEA, New Technologies, Energy and Environment National Authority, Rome, Italy 2 Hydrocontrol, Research and Training Centre for Water Systems Control, Cagliari, Italy
ABSTRACT A preliminary performance assessment (PA) analysis for the LLW Repository in Italy is described in this paper. In particular, the PA analysis of the so called SA site is reported. The AMBER code has been used for the setting up of radionuclides transport simulation model both in the near-field and geosphere. The performance assessment analysis preliminarily showed that the SA site was likely to be suitable, in geological and hydrogeological terms, for hosting a LLW Repository. Total dose to the critical group for both a normal evolution scenario and cover degradation scenario was 4.2 × 10-3 mSv/year, approximately one order of magnitude lower than the 10-2 mSv/year dose constraint adopted in this study. INTRODUCTION A preliminary performance assessment (PA) analysis for the LLW Repository in Italy is described in this paper. In particular, the PA analysis of the so called SA site is reported. The near surface disposal option has been chosen for the LLW Repository design in Italy (Figure 1). Wastes will be placed in a concrete structure whose containment capacity will be assured by an engineered barriers system (EBS). The near surface disposal option was considered the most suitable for assuring: • • •
effective isolation of the waste for the first few hundred years; gradual releases of the long-lived isotopes in the surrounding environment; reduction of likelihood or consequence of inadvertent human intrusion.
Figure 1 – Suggested Repository design for the SA site. JJ7.1.1
The PA analysis described in this paper must be considered as a very preliminary approach for defining a standard procedure for the evaluation of candidate sites that will be identified by means of the GIS-based site selection process underway now in Italy. This activity, managed by the ENEA – Task Force Sito Research Group, will lead to the definition of a short list of 20 candidate sites, that will be characterized and evaluated only using literature derived data and professional experts on site visits. DOSE STANDARDS FOR INDIVIDUALS Radiological protection objectives used for the PA analysis described in this paper refer to recommendations made by the Italian Environment Protection Agency (ANPA) that established a limit of 10 -2 mSv/y for individual dose to members of a hypothetical critical group for the normal evolution scenario. SCENARIO DEFINITION Two very simplified descriptions of possible future evolution of the Repository have been defined for the PA analysis of the SA site: a normal evolution scenario and a cover degradation scenario. In the normal evolution scenario, the Repository EBS is assumed to remain intact for a post-closure institutional control period of 300 years, during
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