6.76. The introduction of measures to facilitate retrievability does not lessen the need for a thorough safety assessment and may introduce the need for additional assurances regarding certain operational aspects (e.g. the long term durability of waste packages under operational conditions before closure of the facility; provisions for facility closure). In particular, retrievability should not be made an nexcuse for an indefinite delay in making decisions concerning the development of the disposal facility and is not a substitute for a well designed and well sited disposal facility for which the basis for closure of the facility at the end of its lifetime can be justified. Clear plans for development of the disposal facility, including its closure, should be prepared even if flexibility is allowed to future decision makers in their implementation of the plans. Safety assessment calculations should be made to determine the consequences of failure to close the disposal facility as originally intended.