6.66. The unavoidable tension between the expected duration of active institutional control and the period of time over which long lived waste will remain hazardous has led to disposal strategies in which institutional control plays different roles:@@- In geological disposal and disposal at intermediate depths, institutional control may provide another layer of defence in depth, as long as it lasts, and may contribute to building confidence in the safety of the disposal facility. However, the safety objective should be achieved even in the absence of institutional control.@@- In the disposal of radioactive waste at or near the surface, institutional control is usually required for achieving the safety objective and should remain in place as long as the waste remains potentially hazardous (e.g. a few hundred years). Waste containing appreciable amounts of long lived radionuclides should be disposed of at greater depths. Assumptions concerning the duration of institutional control play a major role in defining waste acceptance criteria, particularly for near surface disposal facilities.