An integrated safety approach and consideration of some basic criteria for the disposal of radioactive waste

According to Swedish regulations the nuclear power plant owner is responsible for the safe management and disposal of radioactive waste. Criteria for protection of health and environment are set by the Swedish Radiation Protection Institute (SSI). The Swedish Nuclear Power Inspectorate (SKI) sets corresponding safety criteria and is responsible for review and supervision of the safety of facilities for management of nuclear waste, the nuclear industries R and D programme and the funding system for future costs for nuclear waste disposal. All of these tasks of SKI include assessments of safety. An assessment of the safety of final disposal of radioactive waste should cover the total disposal system (all barriers of the repository system; operational phase as well as post-closure phase of the repository). Each step in a handling sequence must consider earlier as well as subsequent steps, so that a waste product resulting from one step is suitable for all subsequent steps. The safety of a repository for high level waste and spent nuclear fuel should rely on a robust system of multiple barriers. The application of this principle means that the function of one of the barriers might be lost without seriously jeopardizing the safety. Deep geological disposal seems to be the only option available today which complies with this requirement. Even if the assessment relies on an assessment of the total system and not on technical subsystems, technical requirements on the individual barriers must be defined. The safety case is defined by a set of scenarios. Also possible human actions that could affect the integrity of the repository system should be included. A safety assessment includes an uncertainty analysis of models, scenarios and data. The need for verification/validation of models and the reliance on expert judgement is pointed out as well as the need to accept 'reasonable assurance' as the realistic attitude in the demonstration of safety. (author)