ML20101R369

Final Part 21 Rept Re Failure of Byron Jackson River Water Pump Couplings.Initially Reported on 911121.Couplings Failed in Svc Due to Lack of Toughness.Couplings Examined & Suspect Matl Removed from Svc

ML20101R369
Person / Time
Site:	Beaver Valley
Issue date:	07/07/1992
From:	Noonan T DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-92 ND3MNO:3295, NUDOCS 9207150335
Download: ML20101R369 (6)

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, [ 6, nkP Tempnone (412, W,-6000 Nudear Group P O Box 4 Shippngpoet PA iS07/4J004 July 7, 1992 ND3MNO:3295 Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 10 CFR 21; Byron Jackson River Water Pump Couplings Supplemental Information United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attn: Director, Office of Nuclear Reactor Regulations

-Gentlemen:

On November 21, 1991, Duquesne Light C mpany submitted a 10 CFR Part 21 report concerning the Beaver Valley Unit #1 River Water Pump couplings supplied by Byron Jackson. Attached is the final report on this issue, based on supplemental information.

Should you have any further questions regarding this matter, we will be pleased to discuss them with you.

Very truly.yours,

, 47 &

T. P. Noonan General Manager Nuclear Operations JJM/s1 Attachment

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9207150335 920707 Il R ADOCK 03000334 '

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' July =. 7, 1992' ND3MHO:3295-

, _ Pape two-cc:1Mr. T. .T. Martin, Regional Administrator United. States Nuclear Regulatory Commission

. Region 1 475 Allendale Road King of Prussia, PA 19406 C. A. Roteck,Johio Edison 76 S.= Main. Street Akron, OH 44308 Mr. A. DeAgazio, BVPS Licensing Project. Manager United States Nuclear Regulatory Commission Washington, DC 20555 Larry Rossbach, Nuclear Regulatory Commission, BVPS Senior. Resident Inspector Larry Beck Centerior Energy 6200 Oak Tree Blvd.

Independence, Ohio 44101-4661 INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta,-GA 30339 G.-E. Muckle, p Factory Mutual Engineering 680 Anderson' Drive #3LD10 i: Pittsburgh, l'A 15220-2773 1 Mr. Richard Janati.

L Department of1 Environmental Resources P. O. Box.2063 li '16th.Flocr, Fulton Building Harrisburg, PA 17120 h

L Director,. Safety-Evaluation & Control Vligi.nia Electric & Power Co.

P.O. Box 2666:

One James River Plaza Richnond, VA 23261' W. Hartley.

1 Virginia Pcwer Company 2SW G e n A e Vk23060

-J. M. Riddle Halliburton NUS Foster Plaza 7 661 Anderson. Drive Pittsburgh, PA 15220 w n e t

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July 7, 1992 ND3MNO:3295

, Pacie three Bill Wegner, Consultant 23 Woodlawn Terrace Fredricksburg, VA 22404 S

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Attachment 1 Page 1 10 CFR Part 21 BVPS Unit 1 - Byron Jackson River Water Punp Couplings Supplemental Information Final IKport on the Failure of Dytui Jackson River Water Punp Cotplings INITY1XJCTIN The conditions which caused the failure of the river water pump (WR-P-1A) coupling and the degradation of a second coupling from the 1B river water pump (WR-P-1B) at Unit 1 are summarized in this report. Also included are the conclusions of the investigation. The cause of failure was the lack of material toughness. Operating conditions combined with low toughness may have hastened the initial failure, but the degraded coupling found in "1B" pump confirmed the cause to be material related.

DLNW During a startup of the 1A River Water Pump (WR-P-1A) on June 20, 1991, the pump failed to produce flow. An investigation was initiated and revealed a mechanical failure of the shaft coupling. A failure analysis was initiated to determine the root cause.

The analysis report (Reference No. 1] contains the results of the failure analysis, the material characterization of the failed coupling and the test results from the five additional couplings taken from service on "1A" pump. Three of these additional couplings were from the same heat and routing slip number - as the failed coupling, Heat #821336, R/S 164340-10. The report establishes thut all the couplings of that lot, Heat

1. 821336, R/S 16430, had been embrittled. The measured energy absorption from Charpy V Notch (CVN) testing was 8ft-lbs maximum for this heat of material. Other heats of coupling material exhibited energy absorption of 10ft-lbs minimum. Lack of toughness, consequently, caused the failure of the coupling fabricated from the embrittled heat.

Examination of the purchasing records revealed that other couplings from the suspect lot were received and installed. The couplings of all three river water pumps were examined and suspect material was removed from service. One additional coupling was identified as Heat #821336, R/S 164340-11, from pump WR-P-18. After removal, a circumferential crack was found mid-length on the coupling approximately 2 inches long.

Additional testing was done to confirm the cause of failure and attempt to establish the temper sensitivity of the material.

The analysis (Reference No. 2] concluded that the material was embrittled and the failure mode was similar to that of the coupling from WR-P-1A.

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Attachment 1 page 2 Charpy impact test specimens, taken from the second failed coupling, were re-heat treated to simulate the typical processing given the couplings. A series of additional impact specimens were re-heat treated and tempered at various temperatures between 500 F and 1200 0 F. The results of the testing confirmed that the coupling material, ASTM A-276 Type 410, responded to the heat treatment as predicted by published data [ Reference No. 3].

Hardness tests were also plotted for the reheat treated samples to correlate anticipated toughness with the hardness in laboratory treated material. Compared to this correlation, the toughness seen in the failed couplings corresponds to the top of the vendor specified hardness range of 26 Rc to 34 Rc. The recorded hardness of 29 Rc, which is at the middle of the specification range, predict a slightly high toughness.

However, given the inaccuracy for the low number of samples tested, the slope of the impact energy versus temper temperature curve in tnis region, and the slower cooling rates expected for actual processing, the results of the embri*.tled material are consistent with the laboratory results.

CCNCUEICNS

'Ihe evaluations support the conclusions that:

1. The couplings failed in service due to a lack of toughness, i Both failures occurred in material witi. a measured energy absorption of 8ft-lbs or less using a 7mm X 10mm CVN specimen. Toughness is independent of hardness and could vary significantly with uniform hardness, depending on the material processing and chemistry.

2. Couplings fabricated from heats other than 821336 exhibited toughness values in excess of 10ft-lbs. No failures have

!- occurred with these other heats, thus providing a benchmark for acceptable minimum toughness requirements to meet service conditiors.

3. The coupling material met the vendor specifications and responded to heat treatment as expected when compared to l published industry data. However, a material which meets

! ASTM A-276, heat treated to 26 Rc to 34 Rc, and does not l possess the required toughness could fail in the river water pLmp application.

Attachment 1 Page 3 BIM T&N OS:

(1) " Metallurgical Analysis of Shaft Couplings from Beaver Valley Power Station", J. N. DuPont and A. O.

Benscoter, Lehigh University, Energy Research Center, September 25, 1991.

(2) ." Analysis of- a Cracked Shaft Coupling from the Be*-er Valley Power Station, Part 2-Failure Analysis- and

-Verification of Heat Treatment", J. N. DuPont and A. O.

Benscoter, Lehigh University, Energy Research Ccnter_.

March 38, 1992.

(3) " Aerospace Structural Metals Handbook", 1980 Edition, Vol. 2, Battelle's Columbus Laboratories, Columbus, Ohio,-Code 1401, p26.