8.9. As the facility moves into the operational period, monitoring and surveillance should be continued in order to provide information about operating performance, which can be used to update the safety case. The operational safety case is developed prior to the granting of a licence for construction and operation. Residual uncertainties are often managed using conservative estimates of system functions with respect to their implications for safety. Available monitoring information prior to construction, which may be sufficient to develop the safety case, should continue to be updated throughout the operational period, as part of a monitoring programme for confirming performance of the disposal facility. This programme should lead to progressive improvement in understanding of the disposal system, which in turn should be used to improve operating approaches, definition of safety functions, facility design, and design of the monitoring programme. For example, monitoring data on the corrosion rate of a material collected as part of a monitoring programme for confirming performance may lead to a modification in the acceptable inventory limits in the disposal facility. Ideally, if the operational safety case is based on conservative estimates, then changes or improvements in understanding will lead to less restrictive and less costly operating approaches.