Risk assessment criteria for radioactive waste disposal

The assessment of radioactive waste disposal options in terms of the annual risk to the critical group can lead to ambiguities, which arise largely in defining what is meant by the critical group. Radically different risk estimates can be obtained, depending on whether statistical averaging is carried out before or after the critical group is located in the time dimension. The merits of two different approaches are discussed through simple thought experiments and mathematical models. A criterion based on lifetime risk to the critical group is suggested, which could be used to supplement the currently accepted annual risk limits. The risks from both stochastic and nonstochastic radiation effects are taken into account