5.10. Radiological impact assessment for the period after closure should be performed using an appropriate selection of approaches that, when used in a complementary manner, can increase confidence in the safety of a disposal facility. The different approaches that can be considered include: probabilistic and deterministic approaches, the use of simple conservative models and the use of complex, more realistic models. If a conservative approach is to be used, it should be realistic, making use of empirical data, as practicable, as well as expert judgement in selection of exposure scenarios, conceptual models, parameters and simplified calculation models.