Nuclear Power Plant Olkiluoto 3-Containment Leakage Test Under Extreme Conditions

Modern nuclear power plants place high demands on the design and execution of safety checks. TUV SUD supported the containment leakage test for the largestcapacity third generation nuclear power plant in the world - Olkiluoto 3 in Finland. The experts successfully met the challenges presented by exceptional parameters of the project. The containment of Olkiluoto 3 is unique in that the vessel's volume is 80,000 m(3) while measurements were carried out over a period of ten days. To execute the test, 75 temperature and 15 humidity sensors had to be installed and correctly interlinked by more than ten kilometres of cable. These instruments also needed to withstand an absolute pressure of 6 bar, ambient temperatures of 30 degrees C and high levels of humidity. These conditions required comprehensive preparation and a high amount of qualification tests. Parts of the qualifications were carried out at the autoclave system of the Technical University in Munich, Germany, where the project test conditions could be simulated. The software required to determine the tests was developed by TUV SUD and verified by German's national accreditation body DAkkS under ISO 17025. TUV SUD enabled the test schedule to continue without delay by analysing all recorded data continuously on site, including pressure, temperature, humidity and leakage mass flow curves. With the comprehensive preparation, data acquisition, system recording measurements continuously and the on-time result calculation, all components of the leak-tightness assessment were successfully completed in accordance with requirements.