The goal of the thesis is to design a measuring routine for performance monitoring for the OL3 nuclear power plant water-steam cycle, before and after outage. A measuring routine will be done using built-in measuring equipment. The purpose of the measuring is to find deviations in the process and performance before and after the outage but not to analyze uncertainty of the measurements or to try to achieve as low uncertainty as possible.

The thesis includes the evaluation of the measuring routine in the OL1- and OL2- nuclear power plants, performance tests during the commissioning of the OL3- nuclear power plant and the guarantee test procedure of OL3. This thesis also evaluates the experiences and lessons learned in real world performance monitoring and application of methods to OL3. Also discussed is the usage of a digital model in support of the performance monitoring. The benefits of a digital twin in performance monitoring are highlighted in the thesis.

This thesis highlights how the measurements before and after outage are connected to performance monitoring during normal operation and how important the on-line monitoring is. The thesis brings out the procedures for organization, measurement and indicators for performance monitoring. The validation for the measuring routine will be done in the future after the commissioning of the plant, however the method used in performance testing during the commissioning will support the evaluation of the method that will be used later during the operation of OL3.