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LER 98-005-00:on 980211,failure of 2A EDG Turbocharger Was Noted.Caused by Failure of Blade on Turbochargers Rotating Turbine Disc.Damaged Turbocharger on 2A EDG Was Replaced W/ Refurbished turbocharger.W/980312 Ltr
	ML18106A374
Person / Time
Site:	Salem
Issue date:	03/12/1998
From:	Bakken A, Knieriem B; Public Service Enterprise Group
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	LER-98-005, LER-98-5, LR-N980114, NUDOCS 9803190383
	Download: ML18106A374 (6)
	v • d • e

e OPS~G P'ublic Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit MAR 12 1998 LR-N980114 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 LER 311/98-005-00 SALEM GENERATING STATION - UNIT 2 FACILITY OPERATING LICENSE NO. DPR-70 DOCKET NO. 50-311 Gentlemen:

This Licensee Event Report entitled Technical Specification Required Shutdown Of Salem Unit 2 Due To The Failure Of The 2A Emergency Diesel Generator Turbocharger is being submitted pursuant to the requirements of the Code of Federal Regulations ****10CFR50.73 (a)(2)(i)(A)****.

Sincerely, A. C. Bakken Ill General Manager Salem Operations Attachment RBK/

c Distribution LER File 3.7 9803190383 980312 PDR ADOCK 05000311 S PDR 85*2168 RFV 0194

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 COMMISSION EXPIRES 04/30/98 (4-95) ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LICENSEE EVENT REPORT {LER) LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (See reverse for required number of (T-6 F33), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-digits/characters for each block) 0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

SALEM UNIT 2 05000311 1 OF 5 TITLE (4)

Technical Specification Required Shutdown Of Salem Unit 2 Due To The Failure Of The 2A Emergency Diesel Generator Turbocharger EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH OAY YEAR YEAR I

SEQUENTIAL NUMBER I REVISION NUMBER MONTH DAY YEAR FACILITY NAME Salem Unit 1 DOCKET NUMBER 05000272 FACILITY NAME DOCKET NUMBER 02 11 98 98 -- 005 -- 00 03 12 98 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) I 11 I MODE (9) 1 20.2201(b) 20.2203(a)(2)(v) x 50. 73(a)(2)(i) 50. 73(a)(2)(viii)

POWER 20.2203(a)(1 I 20.2203(a)(3)(i) 50.73(a)(2)(ii) 50. 73(a)(2)(x)

LEVEL (10) 100 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50. 73(a)(2)(iii) 73.71

20. 2203(a)( 2Hiil 20.2203(a)(4) 50. 73(a)(2)(iv)

OTHER 20.2203(a)(2)(iiil 50.36(c)(1) 50. 73(a)(2)(v) Specify in Abstract below or in NRC Form 366A

20. 2203( a)( 2)(iv) 50.36(c)(2) 50. 73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Brooke Knieriem, Licensing Engineer (609) 339-1782 COMPLETE ONE LINE FOB EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO EPIX I

x EK DG Al52 *-

.y SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION

'YES (If yes, complete EXPECTED SUBMISSION DATE). X 'NO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

This LER documents the controlled shutdown of Salem Unit 2 as required by Technical Specification 3.8.1.1, following the failure of the 2A Emergency Diesel Generator turbocharger. The event is reportable under 10CFR50.73(a} (2) (i) (A) , the completion of any nuclear plant shutdown required by the* plant's Technical Specifications.

At 0300 on February 9, 1998 the 2A Emergency Diesel Generator (EDG) was removed from service for a scheduled maintenance outage. Salem Technical Specifications provide an allowable EDG outage time of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . This maintenance work was completed on February 11, and at 0932 the 2A EDG was started for a surveillance run to verify operability.

About 40 minutes into the loaded run an abnormal noise was heardi followed by decreasing load_ The engine was shutdown and an investigation begun. During the investigation the Operations Superintendent determined that the cause of the abnormal noise and the loss of load could not be identified and corrected prior to the expiration of the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months TS action statement. At 1355 the NRC was notified of the initiation of a controlled shutdown in accordance with 10CFR50. 72 (b) (i) (A) At 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months a reactor shutdown was commenced.

Salem Unit 2 entered Mode 3 (Hot Standby) at 0140 on February 12, and Mode 5 (Cold Shutdown) at 1144 on February 13.

The abnormal noise and the loss of load of the 2A EDG was subsequently determined to have been the result of damage to the EDG's turbocharger caused by the failure of a blade on the turbocharger's rotating turbine disc. The cause of the blade failure was high cycle fatigue. The cause of this fatigue is under investigation.

NRC FORM 366 (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION flA.IPtEER SALEM UNIT2 05000311 98 - 005 - 00 2 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor Emergency Diesel Generator {EK/DG}

Diesel Engine ALCO Model 251, Turbocharger ALCO Model 165 CONDITIONS PRIOR TO OCCURRENCE Mode 1 ioo% Power There were no structures, systems or components that were inoperable at the start of this event that contributed to this event.

DESCRIPTION OF OCCURRENCE At 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months on February 11, 1998 a reactor shutdown was commenced on Salem Unit 2 in accordance with Technical Specifications due to the inoperability of the 2A Emergency Diesel Generator (EDG). Salem Unit 2 TS 3/4.8.1 A.C. Sources, Section 3.8.1.1, requires in Modes 1, 2, 3, and 4 that three separate EDGs be operable. If an EDG is inoperable it must be returned to an operable status within seventy-two hours or the plant must be placed in Mode 3 (Hot Standby) within the next six hours, and in Cold Shutdown (Mode 5) within the following thirty hours.

At 0300 hours0.00347 days 0.0833 hours 4.960317e-4 weeks 1.1415e-4 months , on February 9, 1998 the 2A EDG was removed from service in preparation for a scheduled maintenance outage. The scheduled work for the outage was completed and on February 11,, 1998 Salem Operations began a post maintenance surveillance test prior to restoring the 2A EDG to an operable status.

At about 0932 the 2A EDG was started and loaded in accordance with procedure S2.0P-ST.DG-0001(Q), "2A Diesel Generator Surveillance Test". At approximately 40 minutes into the run, the local ope;ator heard a loud banging noise followed by a rumbling noise. No abnormal alarms were observed at the EDG Control Panel but the operator noted that generator lea~ had lowered from 2600 KW to 800 KW and was continuing to decrease. The Control Room was informed of this condition. The operator returned to the Engine Room and observed black smoke blowing from the exhaust expansion bellows and a piece of gasket material on the floor in the vicinity of the diesel turbocharger. The operator again contacted the control room to report that condition and to report that generator load had lowered to 500 KW. The Control Room then *ordered the operator to open the 2A EDG output breaker and to shutdown the engine.

At the time the 2A EDG surveillance was terminated, the EDG had been inoperable for 56 hours6.481481e-4 days 0.0156 hours 9.259259e-5 weeks 2.1308e-5 months of the 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months allowed by TS. Attempts to immediately identify the cause of the loud noise and the subsequent loss of EDG load were unsuccessful. Since it did not appear that the 2A EDG would be restored to operability within the time allowed by TS, the Operations Supertinendent decided that Unit 2 would be shutdown. At 1355 the NRC was notified of the initiation of a contr9lled shutdown in accordance with 10CFRS0.72(b)

i) '.A). ::.t ::.4CC :::>..:.::::s .. :'."":=>.:"::-:::::: 3r.c:c.:J.cw" "::ts ::::IT'm""r:::eC: . .:2.:e:-- -:r..:i.t:::: -:::r..tered i-!ode 3 :'1ct Standby) at 0140 on February 12, and Mode 5 (Cold Shutdown) at 1144 on February 13.

CAUSE OF OCCURRENCE The cause of this event was determined to be the failure of the 2A EDG turbocharger.

Specifically, the failure of a blade on the turbocharger rotating turbine disc due to high cycle fatigue. The exact cause of that fatigue has not yet been identified.

Under normal operating conditions, the turbocharger rotates at 18,000 RPM with a gas inlet temperature ranging from 400F to lOOOF. This turbocharger had accumulated 194 NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER IREVISION NUMBER SALEM UNIT2 05000311 98 - 005 - 00 3 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CAUSE OF OCCURRENCE (cont.)

hours of service with 114 start-ups at the time of failure. Prior to this failure, there was no evidence of unusual operation nor obvious evidence of damage. -;

Initial inspection and troubleshooting determined that the turbocharger rotor was seized.

An unknown piece of metallic debris was found during removal of the gas casing drain.

Metallurgical analysis determined the metal to be Inconel 713. This material is consistent with the material used to manufacture the turbocharger moving blades.

PSE&G maintenance personnel removed the turbocharger and moved it to a maintenance shop for inspection. At.that time it was verified that a turbine blade(s) failure had occurred. The turbocharger was then sent to PSE&G's Central Maintenance Shop (CMS) for disassembly.

Causal factor determination activities included boroscopic inspection of the exhaust/intake piping, exhaust silencer, and engine cylinders; including pistons, heads, valves, valve seats and valve guides. No degraded or missing parts were identified during the boroscopic inspections, with the exception of turbine blade material carry-over to the exhaust silencer. Valve backlash was verified to be satisfactory. Lube oil and jacket water samples were taken with satisfactory analysis results.

Visual examination of the turbocharger bearings revealed localized damage to one side of the shaft. This suggests that the shaft sustained a momentary imbalance which caused the shaft to interfere with the bearing. The driving force for such an*. imbalance appears to have been blade separation. Therefore, the turbine end bearing appeared to have functioned properly up to the moment when the blade fractured.

Examination of the stationary bla.des revealed that the stationary blade inlets were in good condition with no evidence of foreign object damage at the leading edge or at the concave side of the airfoil. The convex side of the stationary blades showed numerous impingement dents and sporadic localized areas of metal thinning. Further, the convex side of the stationary blades showed numerous scrapes, rubs, and mechanical deformation as a result of secondary damage from the rotating blades.

The rotating turbine disc was examined and revealed one missing blade with secondary mechanical damage to other rotating blades. The missing blade had fractured at the top steeple in the fir tree area. The blade section was missing. A comprehensive inspection of the exhaust ductwork did not find any other large chunks of metal but rather small pebble like material. Some blade tips showed severe secondary impact damage while other blade tips showed-minimal tip damage. Had general tip damage occurred due to a steady-state mechanism, -such as long term bearing wear, then all of the blade tips would have been severely damaged. This was found to not be the case.

A detailed metallurgical evaluation of the failed blade determined the nature of the failure to be high cycle fatigue, originating at the trailing edge side of the fir tree at the top steeple. The crack progressed through the blade from the trailing edge toward the leading edge in a mixed mode until final fracture occurred,.

Visual examination of the turbine disc revealed two additional blades with cracks at the leading edge in the fir tree at the top steeple. A follow-up fluorescent dye penetrant examination of the turbine disc revealed an additional five cracks at the trailing edge fir tree in five blades, one crack per blade, at a similar location to the failed blade.

One of the visually observed leading edge cracks and one of the fluorescent dye penetrant identified trailing edge cracks were opened and examined at the laboratory. Both cracks showed evidence of fatigue. The trailing edge crack had propagated about a.a inches in a manner similar to the original failure.

NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER IREVISION NUMBER SALEM UNIT 2 05000311 98 - 005 - 00 4 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CAUSE OF OCCURRENCE (cont.)

There was no evidence of corrosion at the surface of the rotating blades, no evidence of stress corrosion cracking, and no evidence of erosion/corrosion attack of the rotating blades.

Chemical analysis of the rotating and stationary blades identified the rotating blades to be similar to INCONEL 713 and the stationary blades to be similar to 309 stainless steel.

The "metallic nugget" found in the turbo gas casing has .a chemistry similar to the rotating blade material and therefore was most likely from the original blade fracture and part of the missing blade.

The chemical analyses were submitted to the Original Equipment Manufacturer (OEM) for review. The EDG vendor concurred that the blade m?Lterials were in agreement with OEM specifications.

Due to the nature of th~s failure, continued analysis will be req\iired to determine if a cyclic damaging force exists. Analysis would include but not be limited to modeling and testing for unanticipated resonance or flow induced vibration.

Based upon metallurgical analysis of the failed components, the failure mode has been determined to be high cycle fatigue failure and not the result of impingement damage caused by material ingestion. PSE&G is continuing to investigate the root cause of the blade failure. The services of a consultant with expertise in dynamic analysis and failure investigation of rotating systems and components will be retained to assist in the investigation. Should a root cause for this event be identified, reporting will be made via a supplement to this LER.

A survey of the industry identified one other similar failure of rotating turbine blades on an ALCO Model 165 turbo charger. This failure occurred on the station black out diesel at Indian Point No. 3 in 1995. The failure was* attributed to foreign object impact damage at the trailing edge of one blade, leading to a fatigue failure. The laboratory that performed the analysis for this failure was contacted. Based on.this contact it was learned that there were no other cracks found as a result of visual and non--destructive examination. This differs from the failure of the Salem 2A EDG in that other cracking was found on the Salem tur~ocharger.

PRIOR SIMILAR OCCURRENCES A review of LERs for Salem Units 1 and 2 issued in the last two years identified no other similar occurrences. However, Salem Generating Station Reportable Occurrence Report 272 77-80/03L, dated January* 5, 1978 reported a failure of the lB Emergency Diesel Generator turbocharger. The failure occurred in December 1977 and was a fatigue failure of a turbocharger turbine blade. This failure was the basis for a design change to the rotating blades.

SAFETY CONSEQUENCES AND IMPLICATIONS This event did not impact the health and safety of the general public.

At the time of the failure the 2A EDG was out of service for a scheduled maintenance outage and was being tested to verify its operability prior to returning it to service.

The other two Unit 2 EDGs were operable. With one diesel inoperable the two remaining diesels are capable of providing power to the minimum safeguards equipment required for analyzed accident and transient conditions.

NRC FORM 366A (4*95)

.. ~

t*RC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER IREVISION NUMBER SALEM UNIT2 05000311 98 - 005 - 00 5 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

SAFETY CONSEQUENCES AND IMPLICATIONS (Cont.)

The turbochargers for the other five Salem EDGs were evaluated to determine their susceptibility to a similar failure. This evaluation included a review of operating hours, number of starts, and past maintenance history for each EDG turbocharger. Of the six Salem EDGs, the 2A EDG turbocharger had the fewest starts and operating hours. Also considered in this evaluation was a review of industry operating experience which identified one similar failure. Based upon this evaluation, it was concluded that this failure was not indicative of a generic issue affecting the reliability of the other Salem EDGs.

CORRECTIVE ACTIONS

1. The damaged turbocharger on the 2A EDG was replaced with a refurbished turbocharger.

2. Further investigation will be performed to determine the cause of the fatigue that caused the blade failure. Should a cause be identified, reporting will be made via a supplement to this LER.

3. Additional monitoring and optimization of the preventive maintenance program for EDG turbochargers are in progress to determine the actions that may be necessary to prevent recurrence of a similar failure.

NRC FORM 366A (4*95)

ML18106A374

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