ML20151C769

Ro:Change of Commitment Submitted Re Diesel Generator Turbocharger Rotor Assembly Replacement.Turbocharger Inlet Casings Replaced on All Four Engines W/New Design.Dye Penetrant Testing Will Continue to Be Performed

ML20151C769
Person / Time
Site:	Mcguire, McGuire
Issue date:	04/04/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
NUDOCS 8804130168
Download: ML20151C769 (2)

Text

e DuxE POWEn GOMPANY P.O. HOX 33189 CHAMLOTTE. N.O. 28249 HALH. TUCKER tutzenows varie essessert (704) 07& 4631 m m aanroom -

April 4, 1988 J

4 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station Docket Nos. 50-369, -370 Change of Commitamt Regarding Diesel Generator Turbocharger Rotor Assembly Replacement Centlement By letter dated September 9, 1986 Duke Power Company reported the valid failure

• of Diesel Generator (D/G) 2B that occurred during routine operability testing on July 25, 1986 due to a failed turbocharger. Among the corrective actions that Duke stated would be taken was: '

The turbocharger rotor assembly will be replaced once every five refueling  !

outages starting with the last replacement, said dye penetrant inspection of '

all diffuser blades and repair or replace them as necessary. If two re-placements occur in the same outage, the replacement and inspection of the l

! lenst operated of the two may be deferred until the sixth outage.

j l The investigation into the cause of the fatigue failure of the turbocharger com- 6 pressor impeller blades is continuing. Having been constructed of aluminum, the i impeller blades have a finite life. While Brown Boveri (BBC) turbochargers are  !

known for their reliability, it is not fully known what effect frequent fast starts and the uprating of the engine by 500kw has had on them. Replacing the  !

rotor assembly at a may.1 mum of six outages (six years) should limit the engine to about 2000 hears and 2000 starts. This is well within the 5600 hours0.0648 days <br />1.556 hours <br />0.00926 weeks <br />0.00213 months <br /> that the 2B turbocharger had at failure and the 8000 hour0.0926 days <br />2.222 hours <br />0.0132 weeks <br />0.00304 months <br /> hearing limit recommended by BBC. I The practice of replacing the rotors periodichily will continue until more data is

, obtained on compressor impeller life.

i Without information from the manufacturer Duke conservatively assumed the impel-1er (inducer) had a limited fatigue life due to its composition. Subsequently, [

1 Duke has obtained data from the manufacturer, Brown Boveri. Metallurgical photos i 1 were sont to Brown Boveri for review of the tracture surfaces and to answer ques-i tions about the physical properties of the impeller. Brown Boveri agreed that j fatigue failure had occurred. In reply to the question. "Is the replacement of 1

compressor impellers after a given number of hours, fast starts, or thermal cycles i J recommended?" Their reply was, 1 890413D168 880404 l PDR ADOCK OJOOO369 /

s DcD  ;

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, Document Control Desk April 4, 1988 Page 2 "THE INDUCER FAILED BY HIGH FREQUENCY VIBRATION. THEREFORE WE DO NOT RECOM-

!!END TO REPLACE THEM PERIODICALLY. WE WOULD RATHER SUGGEST TO REPLACE THE AIR INLET CASINGS BY (with) THE NEWLY DESIGNED EXECUTION WHICH HAS BEEN IN-TRODUCED IN ORDER TO REDUCE THE EXCITATION OF THE INDUCER BLADES OF VTR.1 SERIES TURBOCHARGERS. THIS COULD WITHOUT DOUBT ALSO INCREASE THE RELIABILITY OF THE VTR 500 TC'S IN THE CASE OF THE McGUIRE POWER STATION" Duke has replaced the turbocharger inlet casings on all four engines at McGuire witit this new design and have had no further problems. Therefore Duke considers the commitment to be completed. Dye penetrant testing will continue to be per-formed on a five year (five outage cycle) basis. Duke feels this change provides a conservative solution to our turbocharger compressor impeller problem and is in keeping with the intent of the original commitment.

Should you have any questions concerning this matter, contact S.E. LeRoy at (704) 373-6233 of Duke's Nuclear Production Department Licensing staf f.

Very truly yours, f#

N' ,,

Hal B. Tucker SEL/254/jgc xc: Dr. J. Nelson Grace, Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta St., NW, Suite 2900 Atlanta, Georgia 30323 Mr. Darl Hood Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washingtcn, D.C. 20555 Mr. W.T. Orders NRC Resident Inspector McGuire Nuclear Station i

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