Development of the optimization model for TBM time intervals in maintenance methods combined TBM and CBM

A reduction of the maintenance cost and an improvement of utilization in facilities have been performed by introducing Condition-Based Maintenance (CBM) to nuclear power plants since the 1980s in USA. In Japan, also, maintenance methods combined with TBM (Time-Based Maintenance) and CBM have a tendency to be applied. In the present work, an estimation and optimization model for extending TBM time interval is developed considering spurious diagnosis of measuring devices in the maintenance method combined with TBM and CBM. Using the present model, the life time of applied measuring devices can be estimated in order to prolong the time interval of TBM execution and satisfy the required one. Moreover, TBM time interval can be given for minimizing the maintenance cost under the condition of the target safety. From a sensitivity analysis of the parameters including the present model, it is clarified that leaving the facilities in an abnormal state has the largest effect on the cost of damage for the maintenance.