The Safety Case

The suitability of the Olkiluoto bedrock for final disposal and the functioning of the technical solution are demonstrated with a so-called safety case. The safety case consists of several complementary reports.

 

Final disposal of spent nuclear fuel has been examined with safety analyses, the latest of which was conducted in 1999. Since then, work has begun to compile the safety case required for the construction licence application for the final disposal facility.

 

The safety case consists of a group of separate reports presenting the starting points of the safety assessment, the models and initial data used, the assessment methods, the assessment results, and related insecurities and conclusions of the safety inspections and their reliability.

 

The safety analyses included in the safety case identify the radiation doses associated both with developments deemed likely and with unlikely events that would compromise long-term safety. Estimates for the radiation doses and radionuclide release speeds presented in the analyses are conservative.

 

The purpose of the analyses is to study the consequences for people or the environment in case that one or several release barriers fail and radioactive substances are released from the repository into the environment.

 

The safety analyses also deal with the uncertainties associated with the assessment of the functioning of the disposal system, various events and processes. When assessing risks, the probability of the events will be taken into account.

 

The reference period for the safety analyses spans some 250,000 years, thus including at least one ice age cycle. After this period, the activity of the disposed fuel is on the same level as that of a large uranium deposit.

 

Even if it is not ever possible to comprehensively review and assess all sequences of events that may take place, the safety analysis proves that disposal of spent nuclear fuel will not harm people or the environment, no matter how pessimistically the consequences are estimated.

 

Complementary Reports of the Safety Case

The safety case consists of several complementary reports. These reports cover topics related to long-term safety, such as developments at the final disposal site and in the repository as well as the changes occurring in the biotic environment for thousands of years from now.

Figure: Main reports of the safety case portfolio (in yellow) and the main input from supporting technical and scientific activities (in blue).

Schedule for Safety Case Reports

The current research and development work aims at defining the final disposal system's performance requirements and proving their feasibility by the end of 2009. At that time, detailed plans will be presented for the safety case to be submitted in 2012 with the construction licence application.