Geoscientific programme for investigation and evaluation of sites for the deep repository

SKB's goal is to be able to commence site investigations in 2002. Extensive preparations are now being made for this transition to the next phase in the siting process for the deep repository. This report describes the investigation and evaluation programme, which is focused on a deep repository in accordance with the KBS-3 method for spent nuclear fuel. When areas for site investigations have been chosen, the programmes will be adapted to the site-specific conditions. The geoscientific work during the site investigation phase is supposed to provide the broad knowledge base that is required to evaluate the suitability of investigated sites for a deep repository. The material must be comprehensive enough to: show whether the selected site satisfies fundamental safety requirements; permit comparisons with other investigated sites; and serve as a basis for adaptation of the deep repository to the properties and characteristics of the site with an acceptable impact on society and the environment. The work is being carried out in consultation with municipalities, regulatory authorities and nearby residents. The main product of the investigations is a site description, which presents collected data and interpreted parameters that are of importance both for the overall scientific understanding of the site and for the analyses and assessments that are made of design and safety assessment with respect to the deep repository's layout and construction as well as its long-term performance and radiological safety. The site description should furthermore present an integrated description of the site (geosphere and biosphere) and its regional environs with respect to current state and naturally ongoing processes. A technical risk evaluation is carried out, by which is meant a description of uncertainties in calculations and the environmental impact of the civil engineering work. The main product of the safety assessment is a safety report, which analyzes whether long-term safety is ensured for the planned deep repository based on reported investigation results and the proposed repository layout. The safety assessment includes analyses of technical, hydraulic, mechanical and chemical processes around a deep repository as well as calculations of radionuclide transport. Data after completed site investigation should serve as a basis for an assessment of at least the same scope as the SR 97 safety assessment. The methodology in SR 97 hereby comprises a basis for the methodology to be used in future safety assessments. The need for data is the primary factor that will guide field activities during the site investigations. What is possible and suitable to do is, however, also determined to a great extent by environmental conditions on the site. Measurements will be made from the air, from the ground and in boreholes. To enable the measurements to be performed quickly and conveniently, some small roads may have to be built and power lines run up to the drilling sites. Drilling is the 'heaviest' activity during the site investigations. Protected areas will be avoided wherever possible. The same applies to other areas that may be sensitive to disturbances, such as breeding areas for unusual bird species and localities with rare plants. With good knowledge concerning the study site's flora and fauna, the field activities can be adapted so that any disturbances will be limited. The initial site investigations are estimated to take around 2 years. The time required is projected to be different for the different sites because the conditions and level of knowledge are different. To enable the resources to be utilized efficiently, the timetables for the investigations at the different sites will be somewhat staggered. The complete site investigations include several drilling stages, where 3-4 deep core boreholes are drilled simultaneously. This is followed by measurements and evaluation of the results. Each drilling stage is estimated to take around one year. After the last drilling stage, a summarizing and comparative evaluation of the different sites is carried out and a permit application with underlying documentation is prepared. This means that the duration of the complete site investigations can be estimated at 3-4 years. An application for siting and construction of the deep repository on one of the investigated sites will be submitted to the Government under the Nuclear Activities Act and the Environmental Court under the Environmental Code. The supporting documentation will then be examined by the authorities and the application reviewed by the Environmental Court. The time required for this is difficult to predict, but is estimated at about two years, which means that the site investigation phase in its entirety is projected to last about 7-8 years