siemens - Public Service Commission

stainless steel inner casing construction, PPL selected the hybrid inner casing design
which included upgraded materials in the high velocity areas. The dark shaded areas on
Figure I represent the use and placement of erosion resistant materials.
Maintenance IntervalsNalve Testing
PPL stipulated in its specification that the retrofit turbine components have at a minimum a 10-
year inspection interval. SWPC LP turbines of such design as selected for Susquehanna, have
been approved by the NRC for 10-year inspection intervals. It is worth noting that from a
turbine design standpoint, the SWPC LP design could justify maintenance intervals up to
100,000 operating hours, which is typically over 12 calendar years.
Also, reducing the frequency of control valve testing often results in operating cost savings. A
majority of turbine vendors can offer turbine equipment that requires only quarterly valve
testing. SWPC’s full arc admission design HP turbines support such a testing regimen, while
requiring less power reduction due to the fill arc all reaction design, as compared to partial arc
and impulse designs.
The main points of an LP casing retrofit that contribute to the reliability and extended
maintenance intervals are:
1.
2.
3.
4.
5.
Entire steam path is replaced which minimizes/eliminates the need for repairs in the
future.
Existing original SSES LP casings represented 20+ year old technology where issues are
increasing, e.g. steam wash, erosion, etc.
Entire turbine is ready for 40+ years service life that fits into license extension plans.
Proactive approach to eliminate future concerns, which are a real possibility with reuse of
existing LPT components.
Design is for 100,000 equivalent operating hour (EOH) inspection intervals/lO year
approval from the NRC.
Advanced Disc Type LP Rotors in Service
Thirty-three (33) nuclear units are in service worldwide, which use the Siemens Advanced disc
technology LP rotors introduced since 1972. Siemens has not experienced the extensive stress
corrosion cracking of disc-type rotor as other suppliers and no Siemens-design LP rotor required
replacement due to SCC concerns.6 In fact, recent replacement of Siemens disc design LP rotors
have been solely for performance improvement reasons due to the availability and application of
i m proved b I ade technology .
Oeynhausen, H., Roettger, G., Meade, W., Termuehlen, H. “Replacement of Nuclear LP Turbine Rotors and Inner
Casings”, American Power Conference Proceedings, April 1-3, 1997, p. 1.
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