PGE/REWE 2015

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Olkiluoto LP Turbine Exhaust Performance Enhancement Programme (Room G109, Auditorium Centre, First Floor)

Teollisuuden Voima Oy (TVO) awarded Alstom a contract to retrofit the eight low pressure turbines on Units 1 and 2 of their nuclear power station at Olkiluoto, Rauma, Finland in May 2007. The Unit 1 turbines were installed during the 2010 annual outage. The units have been uprated approximately 30% since new, and the feed-water pumps were upgraded at the same time as the turbine retrofit, so that the steam volumetric flow through the diffuser and hood has increased significantly. Following the installation of the Unit 1 turbines it was decided to carry out a further performance enhancement program, as opportunities were identified to reduce the losses in the turbine diffuser/hood system at low condenser pressures. Alstom, working with TVO, conducted an extensive study of the flow conditions in the diffuser, hood and ductwork between the turbine last stage blade and the condenser. The complete geometry was modelled both in CFD calculation domains and a representative model turbine. Several candidate design features were identified with potential to improve the performance. The candidates were evaluated and optimised using advanced CFD tools, and the most promising verified in the model turbine; a total of 27 configurations were tested in a four month test campaign. A number of improvement features were finally selected, mechanically designed and manufactured in time for application on Unit 2 in 2011. The performance tests on the second unit indicate that the enhancement features led to a performance improvement of circa 5 MW (depending on condenser pressure), which was consistent with predictions and the model turbine tests. This paper describes the approach adopted during the performance enhancement program, the selected design features, and some interesting enhancement features that were not finally selected. The results of the verification are also presented.