PLA-5565, Replacement of Main Turbine Rotors

Replacement of Main Turbine Rotors

ML030300358
Person / Time
Site:	Susquehanna
Issue date:	01/22/2003
From:	Shriver B Susquehanna
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-5565
Download: ML030300358 (5)

Text

Bryce L. Shriver PPL Susquehanna, LLC  % iA Senior Vice President and 769 Salem Boulevard  % a a a Berwick, PA 18603 ' 14 Chief Nuclear Officer Tel. 570.542 3120 Fax 570.542.1504 blshriver@pplweb comr TM JAN 2 2 2003 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Mail Stop OPI-17 Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION REPLACEMENT OF MAIN TURBINE ROTORS UNITS 1 AND 2 Docket Nos. 50-387 PLA-5565 and 50-388 The purpose of this letter is to notify the NRC that PPL Susquehanna, LLC has updated the SSES Main Turbine Missile Probability Analysis.

Siemens Power Corporation (SPC) will design, manufacture and install new Siemens LP turbine rotors in the Susquehanna Units Nos. 1 & 2 in the Spring 2003 and 2004. Each Susquehanna unit consists of a High Pressure (HP) and three double flow Low Pressure (LP) turbines, which are tandem, compounded with a rated speed of 1800 RPM. Each LP turbine consists of a total of six shrunk-on disks (three per flow).

SPC has prepared an updated missile probability analysis, "Missile Probability Analysis Methodology For PPL Susquehanna, Units 1 & 2 With Siemens Retrofit Turbines, Revision No. 2", in support of this turbine modification work. This analysis accounts for the retrofitted turbine design in conjunction with an interface to the existing GE turbine overspeed controls, which are not being modified. The basic principles of the missile probability analysis methodology are the same as those used by SPC in previous studies and installations involving replacement of GE turbines with SPC turbines (e.g. Limerick, Grand Gulf, Comanche Peak, and Connecticut Yankee). This methodology has been reviewed and accepted by the NRC.

Document Control Desk PLA-5565 For steam turbines at nuclear power plants, the NRC requires the equipment manufacturer to perform a probability study to confirm that the likelihood of producing an external missile, P1, remains below the value of 1 E-5 per year for a turbine with an unfavorable orientation with respect to the reactor containment. Susquehanna 1 & 2 both have this unfavorable orientation. Turbine inspection intervals and overspeed protection system test intervals are set to insure that the external missile probabilities remain below the NRC's required limits.

The SPC updated turbine missile probability analysis supports the existing main turbine inspection and valve testing program outlined in FSAR section 10.2.3.6, Inservice Inspection. This inspection program reflects that:

"* A thorough volumetric ultrasonic examination is conducted on all rotors (both the high pressure and the three low pressure). In addition, all accessible rotor surfaces are inspected visually and by magnetic particle testing. These inspections are conducted at intervals of 10 years.

" A test interval for the main stop, control, and combined intermediate valves is established which is not greater than three months, i.e. Quarterly/Quarterly/Quarterly.

This current test interval reflects GE TIL 969, Revision 1 and GET-8039.1, "Probability of Missile Generation in General Electric Nuclear Turbines Supplementary report: Steam Valve Surveillance Test Interval Extension, September 1993". Inspection at this frequency limits the probability of excessive overspeed due to a main turbine valve fail-to-close event.

The SPC updated turbine missile probability analysis has been reviewed and approved by PPL. The analysis concludes that the probability of generating a missile, P1, is within the NRC accepted limit of 1 E-5 per unit per year for the PPL 10-year turbine inspection and Quarterly/Quarterly/Quarterly valve test frequency. The overall probability for unacceptable damage due to turbine missiles, P4, is less than 1 E-7. This meets the requirements of Regulatory Guide 1.115 and Standard Review Plan sections 3.5.1.3 and 2.2.3, as outlined in NUREG-0776, "Safety Evaluation Report Related to the Operation of Susquehanna Steam Electric Station Unit 1 & 2."

Attachment 1, "Comparison of External Missile Probabilities Inducing Overspeed with NRC Limit" is a copy of the curve of missile probability, P1, versus service time (inspection interval) for the PPL main turbine retrofit by SPC. This curve reflects the main turbine inspection and valve testing requirements outlined above.

Document Control Desk PLA-5565 Any questions regarding this additional information should be directed to Mr. Duane L. Filchner at (610) 774-7819.

Sincerely, B. L. Shriver Attachments: Attachment 1 - Comparison of External Missile Probabilities including Overspeed with NRC Limit copy: NRC Region I Mr. D. J. Allard, PA DEP Mr. T. G. Colburn, NRC Sr. Project Manager Mr. S. Hansell, NRC Sr. Resident Inspector Mr. R. Janati, DEP/BRP

Attachment 1 to PLA-5565 Comparison of External Missile Probabilities Including Overspeed with NRC Limit

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FIGURE 1 COMPARISON OF EXTERNAL MISSILE PROBABILITIES INCLUDING OVERSPEED WITH NRC LIMIT PROBABILITYOF AN EXTERNAL MISSILE(Pi) 1.005,03 1.00E-04 0

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1.00E-05 1.00E-06 0 20000 40000 60000 80000 100000 120000 140000 160000 INSPBMTION INTERVALP HOURS SIEMENS WESTINGHOUSE 20 OF 34 CT-27321