ML20196B647

Summary of 880531 Meeting W/Licensee in Rockville,Md Re Auxiliary Feedwater Pump Degradation Events.Viewgraphs Encl

ML20196B647
Person / Time
Site:	Palo Verde
Issue date:	06/17/1988
From:	Marlone Davis Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8806300326
Download: ML20196B647 (23)

Text

. . -. _ - . .-.. . . - _ .-

DISTRIBUTION-

, ,'.. June 17, 1983 Docket : File ; ' JPartlow

, s ["NRC & c Lo' al PDRs ACRS (10)

PD5 Reading NRC Parti-DOCKET N0S: 50-528, 50-529 and 50-530 GNKnighton pants MJDavis

' LICENSEE: ARIZONA PUBLIC SERVICE COMPANY OGC EJordan FACILITY: PALO VERDE NUCLEAR GENERATING STATION UNITS 1, 2 AND 3

SUMMARY

OF MEETING ON PALO VEP.DE UNIT 1 AFW PUMP DEGRADATION EVENTS A meeting was held in Rockville, Maryland on May 31, 1988, with representatives of.the licensee to discuss the evaluation of the recent failure of the auxiliary feedwater pump at Palo Verde Unit 1 and the planned actions to correct the root cause of the failure. Enclosure 1 is a copy of the briefing slides used by the licensee. Enclosure 2 is a list of meeting attendees.

SUMMARY

The licensee provided a detailed discussion of two surveillance test failures of auxiliary feedwater pumps on Unit 1 that occurred on June 1,1987, and March 25, 1988. In both cases the pumps were unable to devclop the required minimum pressure differential due to the fourth stage impeller becoming free  ;

of the shaft.

The root cause of the events was determined to be hydrogen embrittlement crack-ing in an axial direction along the keyway of the center shaft. sleeve. Galling resulted in shearing of the shaft key which allowed the center shaft sleeve to  !

rotate freely. The center shaft sleeve then bored into the fourth stage impeller i hub, reducing the shaft key material still holding the fourth stage impeller. '

Subsequently, impeller torque sheared the shaft key freeing the fourth stage impeller from the shaft causing the reduction in pump output. l The licensee then presented a corrective action plan of material replacements to minimize the potential for hydrogen embrittlement cracking and to reduce susceptibility to galling. The corrective actions are shown in enclosure 1.

The staff recommended performing the corrective maintenance on the pumps as soon as feasible, rather than deferring the maintenance until the next outage.

Subsequent to the meeting the licensee informed the staff that the corrective maintenance would be performed one pump at a time within the Technical Speci-fication time limits when all replacement parts are received from-the pump manufacturer.

original signed by Michael Davis Michael J. Davis, Project Manager Project Directorate Y Division of Reactor Projects - III, IV, V and Special Projects

Enclosure:

stated DRSP/PDV N' DR p PDV MJDavis:dr GW i'ghton 6/;f/88 6/ /88 8806300306 000617 PDR ADOCK 05000520 P PDR

Mr. E. E. Van Brunt, Jr.

Arizona Nuclear Power Project Palo Verde cc:

Arthur C. Gehr, Esq. Ms. Lynn Bernabei Snell & Wilmer Government Accountability Project 3100 Valley Center of the Institute for Policy Studies Phoenix, Arizona 85073 1901 Que Street, NW Washington, DC 20009 Mr. James M. Flenner, Chief Counsel Arizona Corporation Commission Mr. Charles B. Brinkman,. Manager 1200 West Washington Washington Nuclear Operations Phoenix, Arizona 85007 '

Combustion Engineering, Inc.

7910 Woodmont Avenue Suite 1310 Charles R. Kocher, Esq. Assistant Bethesda, Maryland 20814 Council James A. Boeletto, Esq.

Southern California Edison Company P. 0. Box 800 Rosemead, California 91770 Mr. Mark Ginsberg Energy Director Office of Economic Planning and Development 1700 West Washington - 5th Floor Phoenix, Arizona 85007 Mr. Wayne Shirley Assistant Attorney General Bataan Memorial Building Santa Fe, New Mexico 87503 Mr. Tim Polich U.S. Nuclear Regulatory Commission P. O. Box 97 - Palo Verde Tonopah, Arizona 85354-0097 Regional Administrator, Region Y U. S. Nuclear Regulatory Commission 1450 Maria Lane Suite 210 Walnut Creek, California 94596

, Arizona Nuclear Power Project - 2_- Palo Verde cc:

Chairman Arizona Corporation Commission Post Office Box 6019 Phoenix, Arizona 85003 Arizona Radiation Regulatory Agency ATTil: Ms. Clara Palovic, Librarian 4814 South 40 Street Phoenix, Arizona 85040 Mr. Charles Tedford, Director Arizona Radiation Regulatory Agency 4814 South 40 Street Phoenix, Arizona 85040 Cf.3 i rman Maricopa County Board of Supervisors 111 South Third Avenue Phoenix, Arizona 85003 l

_ . . . . _ _ _ . _ _ _ _ . ~ . _ , _ . . , _ . . _ .

4 BRIEFING 0F NRC STAFF ON PVNGS AUXILIARY FEEDWATER PUMPS l

ROCKVILLE, MD l

MAY 31, 1988 l

O l

AGENDA PVNGS AUXILIARY FEEDWATER PUMPS PRESENTER

~

I. INTRODUCTION A.C. ROGERS II. DESCRIPTION OF AFW PU'!PS M.E. RAD 0CCIA III. ENGINEERING EVALUATION OF B.J. ALBERT AFW PUMP FAILURES IV. METALLURGICAL ANALYSIS RESULTS D.E. SACHS V. CORRECTIVE ACTION PLAN D.E. SACHS/

B.J. ALBERT VI. CONCLUSIONS A.C. R0GERS

l DESCRIPTION OF AFW PUMPS

• EACH PVNGS UNIT HAS THREE AFW PUMPS:

ESSENTIAL, TURBINE-DRIVEN PUMP (A-TRAIN)

ESSENTIAL, MOTOR-DRIVEN PUMP (B-TRAIN)

NON-SEISMIC, MOTOR-DRIVEN PUMP (A-TRAIN)

• AFW PUMPS WERE SUPPLIED BY BINGHAM-WILLAMETTE

• PUMP DESIGN FEATURES:

EIGHT STAGE PUMP

- SINGLE SUCTION

- DOUBLE VOLUTE

- HORIZONTAL, SPLIT CASING

- OPPOSED IMPELLER ARRANGEMENT RATED CAPACITY OF 1010 GPM AT 3280 FEET TDH FOR ESSENTIAL PUMPS

- NON-ESSENTIAL PUMPS HAVE A RATED CAPACITY OF 1010 GPM AT 2960 FEET TDH MER 05/31/88

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AFW PUMP DEGRADATION EVENTS

• TWO SURVEILLANCE TEST FAILURES HAVE BEEN EXPERIENCED AT PVNGS:

- UNIT 1 NON-SEISMIC, M010R-DRIVEN PUMP ON JUNE 1, 1987 ~ - UNIT 1 ESSENTIAL, MOTOR-DRIVEN PUMP ON MARCH 25, 1988

• OBSERVATIONS DURING/F0LLOWING SURVEILLANCE TESTS REDUCED HEAD WHILE OPERATING ON MINI-FLOW RECIRCULATION LOOP

- TWO TROUBLE-SHOOTING RUNS ON ESSENTIAL PUMP. TOTAL RUN TIME OF 30 MINUTES. NO INCREASED VIBRATIONS WERE OBSERVED. - VISUAL INSPECTION OF PUMP INTERNALS: (1) AXIAL CRACK OF CENTER SHAFT SLEEVE (2) SHAFT KEY HAD SHEARED AT SLEEVE AND AT FOURTH STAGE IMPELLER (3) CENTER SHAFT SLEEVE HAD ROTATIONAL FREEDOM (4) FOURTH STAGE IMPELLER HAD ROTATIONAL FREEDOM BJA 05/31/88 ( g l w s. '- ,a {l ! 'N. , .-.=..u. r'+," '.,..")**,,*' d , . C,. u ["!. ' q sy' .,, e , '{; 4.l . o se g * $ f$  ! 8. .. gl if d A. l . . 5th$ h.: . - l l ,.';,[9-. ; .. . g - ... _ O gl' ~ . - , ..l'dQ -lA %- .c.- y p --- -- - .'b. 3 t_ . =.;; t s . ....... - },, g .p f --gt - mV g9 .- eg ,r - gh g.,) g_ - u ... g_ M'M{t--  %% x - -J ,* , :e. e-g

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• AFW PUMP FAILURE SCENARIO (FOR AFN-P01 AND AFB-P01):

(1) CENTER STAGE SHAFa* SLEEVE DEVELOPED AXIAL CRACK (2) GALLING OF SLEEVE TO STAGE PIECE CAUSED SHEARING OF SHAFT KEY (3) CENTER SHAFT SLEEVE HAD ROTATIONAL FREEDOM (4) CENTER SHAFT SLEEVE BORED INTO THE FOURTH STAGE IMPELLER HUB (5) DUE TO METAL LOSS, IMPELLER TORQUE SHEARED THE SHAFT KEY (6) FOURTH STAGE IMPELLER WAS FREED FROM SHAFT (7) REDUCTION IN PUMP PERFORMANCE WAS OBSERVED l i BJA 05/31/88 l A'W PUMP - CENTER STAGE A N ~ FOURTil STAGE IMPELLER R CENTER STAGE PIECE \ PUMP SHAFT  !!!!!!! x i I l SilAFT KEY-V ///////// - e-e-gg g eE1A, _ _ - x PUMP CASING N hl x - a .- 3o .,4 .- - . - u .A 4 4 4 aei. *A. m - I 4 AXIAL CRACK IN SHAFT SLEEVE PUMP SHAFT SHAFT SLEEVE f \' N YN N N N - N NN N -KEY 4 k i - er- .e,.- .-g ..- --.-r y- ,e-r- - ~ , , - .,y-.. ,e .y-.g wy -y ,,,.--,w & w,. ,,.,e m. ,,-..w-., . ,e,..,, +.,.. = ENGINEERING EVALUATION (CONTINUED) l

• GALLING IS NECESSARY TO CAUSE SHAFT KEY TO SHEAR l l

• TWO POTENTIAL CAUSES OF GALLING OF CENTER STAGE SHAFT SLEEVE:

~ (1) CRACKING 0F SLEEVE CRACK ALLOWS SLEEVE TO EXPAND AND l l REDUCE THE DIAMETRAL CLEARANCE - GALLING IS CAUSED BY INCREASED FRICTIONAL FORCES i (2) SLEEVE CRACKING COMBINED WITH SUCTION I TRANSIENTS CRACK DOES NOT REDUCE DIAMETRAL , CLEARANCE ENOUGH TO CAUSE CRACKING BY ITSELF - SUCTION FRANSIENTS (SUCH AS FULL-FLOW STARTS) LEAD TO GALLING BJA l 05/31/88 l 1 i ~~,,--,,,---,,,,,----e-- - - , - , - , - - - - - ENGINEERING EVALUATION (CONTINUED)

• SOUTH TEXAS PROJECT FAILURE SCENARIO:

(1) AXIAL CRACK DEVELOPED IN THE THROTTLE SLEEVE (2) SHAFT SLEEVE INCREASED IN DIAMETER DUE ~ TO CRACK (3) FRICTION CAUSED WELDING OF THROTTLE SLEEVE TO BUSHING (4) ANTI-ROTATION PIN FOR BUSHING SHEARED ALLOWING BUSHING TO ROTATE INSIDE OF CASING (5) THROTTLE BUSHING GALLED THE PUMP CASING (6) GRADUAL SPEED REDUCTION WAS OBSERVED (7) PUMP WAS MANUALLY STOPPED

• ADDITIONAL OBSERVATION ON STP FAILURE:

CENTER STAGE SHAFT SLEEVE WAS CRACKED AND HAD PARTIALLY WORN INTO THE FIFTH STAGE IMPELLER HUB BJA 05/31/88 SO(ml TEXAS AFW IUMP SHAFT SLEEVE THROTTLE SHAFT SLEEVE CENTER THROITLE BUSHING STAGE PIECE CENTER [ 0 ~ "' 0 h 00 ec m

• n,-,, ,

REFER TO 5 "STAGE DISCHARGE , hNfN FOR f/' STUFFING BOX ,  ; .  ; DETAILS -f ' / ' ,j I i . ,Ik th 3 MM , , }_. ; ._ . -. -. ..--, _L -. I- - -- s k y i - . e s' STAGE DISCHARGE \ i \ k'""~"'""""""""""""""'"*""[ 'P R E S S R E ll E F L INE - ELEVATION VIEW CENTER SECTION l AUXILIARY FEEDWATER PUMP ENGINEERING EVALUATION (CONTINUED) l

• TWO SEPARATE FAILURE SCENARIOS HAVE BEEN EXPERIENCED l l

IN THE INDUSTRY - l (1) LOSS OF THE FOURTH STAGE IMPELLER (2) WELDING OF THE THROTTLE St.EEVE TO THE THROTTLE BUSHING  ! l

• CONCLUSIONS: I

- BOTH FAILURE SCENARIOS ARE POSSIBLE i AT PVNGS - CORRECTIVE ACTIONS MUST CONSIDER BOTH FAILURE SCENARIOS I - CORRECTIVE ACTIONS MUST CONSIDER BOTH POTENTIAL CAUSES OF SLEEVE GALLING - INITIATING EVENT FOR THE PUMP FAILURES WAS THE SLEEVE CRACK BJA 05/31/88 I - - . - - - - ~ ~ - , - ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ ~ ' - ~ - - - - - ~ ~ ~ - - " METALLURGICAL ANALYSIS RESULTS

• ANPP FAILURE ANALYSIS:

- METL PERFORMED THE FOLLOWING EXAMINATIONS (1) SCANNING ELECTRON MICROSCOPY (SEM) (2) OPTIC,AL MICROSCOPY (3) HARDNESS MEASUREMENTS (4) ENERGY DISPERSIVE SPECTROSCOPY - RESULTS OF EXAMINATIONS l (1) INTERGRANULAR CRACKING CONFIRMED TO BE PRESENT ACROSS THE ENTIRE FRACTURE FACE. FRACTURE INITIATED IN OR NEAR THE KEYWAY CORNER (ID). (2) INTERGRANULAR CRACKING CONFIRMED BY OPTICAL MICROSCOPY. EVIDENCE OF CORROSION WAS NOTED IN THE AREA 0F CRACK INITIATION. (3) MATERIAL HARDNESS IS ROCKWELL C50.5 (480 BHN) (4) MATERIAL CONFIRMED TO BE AISI 420 - CONCLUSION = MATERIAL FAILED DUE TO HYDROGEN EMBRITTLEMENT CRACKING DES 05/31/88 l METALLURGICAL ANALYSIS RESULTS (CONTINUED)

• INDEPENDENT METALLURGICAL ANALYSIS

- TWO LABORATORIES WERE USED (1) BECHTEL MATERIAL AND QUALITY SERVICES (2) OREGON STATE UNIVERSITY - BOTH LABORATORIES CONCLUDED THAT THE SHAFT SLEEVE FAILED DUE TO HYDROSEN EMBRITTLEMENT

• CONCLUSION

- ROOT CAUSE = HYDROGEN EMBRITTLEMENT CRACKING DES 05/31/88 CORRECTIVE ACTION PLAN l

• OBJECTIVES:

- MINIMIZE THE POTENTIAL FOR HYDROGEN EMBRITTLEMENT CRACKING - REDUCE SUSCEPTIBILITY TO GALLING

• MATERIAL REPLACEMENTS:

(1) CHANGE ROTATING PARTS TO TYPE 410 SS WITH A HARDNESS OF ROCKWELL C24-32 (250-300 BHN) (1100 F TEMPER) - CENTER STAGE SHAFT SLEEVE - THROTTLE SHAFT SLEEVE - IMPELLER WEAR RINGS (2) CHANGE STATIONARY PARTS TO NI-RESIST #2 - THROTTLE BUSHING - CENTER STAGE PIECE - CASE RINGS - SERIES STAGE PIECES (3) CHANGE SHAFT KEY MATERIAL FROM 416 TO 410 SS (4) OPTIMIZE KEYWAY DESIGN DES 05/31/88 l BASIS FOR MATERIAL REPLACEMENTS (1) AISI 410 WITH 1100 F TEMPER (250-300 BHN) - NOT AS SUSCEPTIBLE TO HYDROGEN EMBRITTLEMENT: (1) ABILITY TO PLASTICALLY DEFORM TO PREVENT CRACK INITIATION (2) SIGNIFICANT REDUCTION IN RESIDUAL STRESSES / (2) NI-RESIST #2 - HIGH NICKEL CONTENT CAST IRON - PUMP MANUFACTURER HAS EXTENSIVE EXPERIENCE WITH THIS ALLOY - GALL RESISTANT MATERIAL (3) KEY MATERIAL - AISI 410 l l - CHANGE FROM AISI 416 REDUCES POTENTIAL CORROSION SITES BY REDUCING THE NUMBER OF SULFIDE INCLUSIONS (4) OPTIMIZE KEYWAY DESIGN REDUCES STRESS CONCENTRATION IN KEYWAY CORNER - DESIGN PER INDUSTRY STANDARD ANSI B17.1-1967 DES 05/31/88 . - _ _ _ _ - _ - _ _ _ - . - - - . __f REPLACEMENT PLAN

• CURRENTLY EVALUATING IMPLEMENTATION PLAN

- MINIMIZE RISK TO THE UNITS - WORK WITHIN VENDOR CONSTRAINTS - REPLACEMENT PLAN WILL BE COMMUNICATED IN LER/PART 21 REPORT

• MAINTAIN ONE SPARE ROTATING ELEMENT ON-SITE AT  !

ALL TIMES

• CONTINUED OPERATION OF THE PVNGS UNITS IS BASED ON THE FOLLOWING CONSIDERATIONS:

- ONLY FOURTH STAGE IMPELLER FAILURES HAVE BEEN OBSERVED AT PVNGS - SAFETY ANALYSIS CALCULATIONS INDICATE THAT FOURTH STAGE IMPELLER FAILURES CAN BE ACCOMODATED - LOW PROBABILITY OF AN ADDITIONAL FAILURE BETWEEN NOW AND WHEN REPLACEMENTS ARE COMPLETED BJA 05/31/88 . May 31, 1988 NAME ORGANIZATION M. Davis NRC/NRR/PDV G. Knighton NRC/NRR/PDV E.A. Licitra NRC/NRR/PDV J.S, Wermiel NRC/NRR/ DEST /SPLB Y.S.Hcang(John) NRC/NRR/ DEST /EMEB C.D. Sellers NRC/NRR/ DEST /EMTB Dan Sachs ANPP David J. Lurenzi ' ANPP Mike E. Radoccia ANPP Brad Albert ANPP Carter Rocers ANPP Ted Sullivan NRC/NRR/EMED ,