6.26. According to Ref. [3], safety significance will usually be the most important criterion to be taken into consideration. The performance of the facility should be considered in terms of releases of radioactive material in normal operation, from anticipated operational occurrences and from reasonably foreseeable disturbing events, and the potential significance of low probability events with potentially high consequences. This criterion can be applied directly at the operational stage of a disposal facility and should also be applied in the post-closure stage. It should be based upon assessed releases of radioactive material during the normal evolution and alternate evolution scenarios, including consideration of the effects of disturbing processes and events. Relatively less effort should be expended on issues that appear to be significant to safety only on the basis of results from assessment calculations (doses and probabilities) for ‘what if’ scenarios (see para. 5.39).