Technischer Bericht NTB 16-08

In a deep geological repository, the access structures function as the link between the surface and the installations and structures at the disposal level. In the planned implementa­tion sce­na­rios, at least two access structures will be in operation up to the time of closure of the repo­si­tory. The radioactive waste will be transported via the main access from the surface to the disposal level during emplacement operations. For the construction and operation of a deep geo­lo­gical repository, additional access structures are required. These auxiliary accesses and the associated surface infrastructure (e.g. shaft head installations) form the subject of this report. To provide as broad and compre­hen­sive a description as possible, seven types of auxiliary access facilities are defined; these are characterised in line with the current status of planning and their functions and impacts are described.

During construction, operation and dismantling of auxiliary access facilities, the usual con­ventio­nal safety measures (inter alia) have to be observed (e.g. groundwater protection, fire pre­vention, facility security, accident prevention). Regarding the "Ordinance on Protection against Major Accidents" no large quantities of hazardous materials, i.e. above the correspon­ding threshold quantities, are to be expected in the auxiliary access facilities. Proper handling and compliance with applicable regulations in all phases will ensure no hazard to humans and the environment.

As no handling of radioactive materials is foreseen in the auxiliary access facilities, and because exhaust air and waste water from the controlled zones of a repository will, in principle, be removed via the main access and not the auxiliary accesses, a safety-relevant emission of radio­active substances and transport of contaminated material can be ruled out for the auxiliary access facilities during both normal operation and also in the case of an accident.

Based on the information presented in this report, Nagra assumes that the auxiliary access facilities of a deep geological repository can be realised in compliance with prescribed norms and standards and operated safely. The actual locations of these facilities will be concretised in a later project phase, with the concerns and wishes of the affected region being taken into con­si­de­ration within certain boundary conditions.