Turbine Oil Degradation and Its Effects on Performance of a Terry Turbine in Nuclear Applications

Abstract

In 2011, during the Fukushima Daiichi Nuclear Power Plant accident, a steam turbine driven safety system, Reactor Core Isolation Cooling (RCIC), operated under conditions it was previously expected to fail during, surpassing its expected run time by approximately sixty hours. This opened for questions such as why the expected run time was so short, whether the system could be relied on for longer run times during beyond design conditions, and why the turbine failed when it did. This specific steam turbine is a Terry designed turbine, used in both Boiling Water Reactors and Pressurized Water Reactors, but there are little data available on the performance of the turbine and even less data available on why its operating conditions are set the way they are. In order to address the previous questions of the turbine behavior at beyond-design-basis conditions and turbine failure modes, the focus was placed on hypothesized reasons for turbine failure. Specifically, the failure mode regarding beyond-design-basis conditions for the oil lubrication system during extended periods was to be observed. The focus of this research is looking at the changes of turbine oil while exposed to heat and the turbine’s bearing degradation due to noted changes of the turbine oil. A new facility needed to be designed in order to test degradation at a variety of temperatures and other conditions for a prototype RCIC turbine and smaller sized Terry turbines. A new facility was designed in the Nuclear Heat Transfer Systems Laboratory at Texas A&M University to carry out these studies. In this thesis research, the facility was constructed and operated gathering initial data successfully to show proper performance for acquiring new data which will be used to improve the reliability of the Terry turbine driven systems in nuclear applications. A 72-hour heated oil test was conducted. Data on the change of oil color (the oil darkened considerably), particulate/residue in the oil after sampling (as measured in a high-accuracy scale), and bearing performance on a Model ZS-1 Terry turbine were acquired.