The Safety Case
of the Olkiluoto bedrock for final disposal and the functioning of the
technical solution are demonstrated with a so-called safety case. In the safety
case, long-term evolution of the final disposal site and the performance of the engineered barrier system are examined beyond 100 000 years.
Posiva submitted the safety case for the review of the Radiation and Nuclear Safety Authority in December 2012.
Safety case is a portfolio of reports
The safety case consists of a group of separate
reports where the evolution of the final disposal site and the repository as well as the biosphere are examined for thousands of years ahead.
The safety case comprise
- the starting points of the safety assessment
- the models and initial data used
- the assessment methods
- the assessment results and related insecurities
- conclusions of the safety inspections and their reliability.
What happens if the the engineered barrier system fails?
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 rates presented in the analyses
The purpose of the safety case 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 case 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 case proves that disposal of spent nuclear fuel will not harm people or the environment, no matter how pessimistically the consequences are estimated.