In March 2019 the Finnish government officially granted TVO an operating license for its EPR. This followed the positive conclusions from Finish regulatory control authority’s safety assessment that the plant has been constructed to be safe and that TVO is able to operate it safely. Completion of the reactor was originally scheduled for 2009, but the project has suffered various delays and setbacks. Once it enters commercial operation early next year, the 1600 MWe pressurized water reactor will supply some 15% of Finland’s electricity demand.
The OL3 reactor unit has a double-shelled containment building in reinforced concrete and an inner steel liner to fulfill with the extreme requirement on the leak-tightness of the containment building.
TELEMAC conventional monitoring system is dedicated to the containment wall. In total over 500 sensors are installed: vibrating wire strain gauges embedded in concrete, temperature sensors, automatic pendulums in 3 different axes and heavy vibrating wire load cells to monitor the pre-stressing system.
SMARTEC DiTeST distributed fiber optic system is monitoring the strains at containment liner surface. About 1,500 meters of continuous horizontal and vertical sensors are installed, covering also dome part. Detection parameters of DiTeSt fiber optic strain sensor are average strains and average strains threshold detection along with the sensors. A central measurement unit with DiView customized software for the treatment, visualization, and storage of the measurement data is used.
Conventional point-wise sensor assures very good performances in terms of measurement resolution but as a main drawback offers local information toward the distributed information offered by the DiTeSt fiber optic monitoring system.