ML18012A858

LER 96-018-01:on 960903,manual Reactor Trip Occurred Due to Loss of Normal Sw.Caused by Mechanical Failure of B Water Pump & a Normal SW to Remain Running Once Manually Started.Restored a Normal SW Pump to Svc

ML18012A858
Person / Time
Site:	Harris
Issue date:	08/08/1997
From:	Verrilli M CAROLINA POWER & LIGHT CO.
To:
Shared Package
ML18012A857	List: ML18012A856 ML18012A858
References
LER-96-018, LER-96-18, NUDOCS 9708200013
Download: ML18012A858 (4)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150.0104 (4.95) EXPIRES 04/30/96 ESTIMATED BURDEH PER RESPONSE TO COMPLY WITH THIS MANDATORY WFORMATION COllECTION REOUEST: 50JI HRS. REPORTED LESSONS LEARNED ARE WCORPORATEO W'IO THE UCENSING PROCESS AND FEO BACK TO WDUSTRY.

LICENSEE EVENT REPORT (LER) FORWARD COMMENTS REGAROWG BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH IT4I F33L US. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of WASHINGTON. OC 205550001, ANO TO THE PAPERWORK REDUCTION PROJECT (3I50.

digits/characters for each block) OI04l OFFICE OF MANAGEMENT AND BUDGET WASHINGTON. OC 20503.

FAcIUTY NAME III OOCKET NUMBER 12) PAGE 13)

Harris Nuclear Plant Unit-1 50-400 1 OF 3 TITLE 141 Manual reactor trip due to loss of Normal Service Water EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (B)

FACIUTY NAME OOCKET NUMBER SEQUENTIAL REVISION MONTH OAY YEAR MONTH OAY YEAR NUMBER NUMBER 05000 FACILITY NAME DOCKET NUMBER 9 03 96 96 018 01 08 97 05000 OPERATING THIS REPORT IS SUBMITTED PUR SUANT TO THE REQUIREMENTS OF 10 CFR B: (Check one o r moro) l11)

MODE (9) 20.2201(b) 20.2203(a) (2) (v) 50.73(a) (2) (i) 50.73(a) (2)(viii) 20.2203(a) (1) 20.2203(a)(3) li) 50.73(a)(2)(ii) 50.73(a)(2)(x)

POWER 100%

LEVEL (10) 20.2203(a)(2) (i) 20.2203(a) (3)(ii) 50.73(a)(2) liii) 73.71 20.2203(a)(2)(ii) 20.2203(a) (4) 50.73(a) (2) liv) OTHER 20.2203(a) (2) (iii) 5O.36(c)(1) 50.73(a) (2) (v) Specrfy in Abstract belew 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 Ilnerude Area Codei Michael Verrilli Sr. Analyst - Licensing (919) 362-2303 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

REPORTABLE REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER TO NPROS TO NPROS KG P115 se

1 SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH OAY YEAR YES SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE). X NO DATE (15)

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

On September 3, 1996 at approximately 2338 hours0.0271 days <br />0.649 hours <br />0.00387 weeks <br />8.89609e-4 months <br />, with the plant operating in mode 1 at 100% power and the "B" Normal Service Water (NSW) pump in service, operators in the main control room received numerous NSW system alarms and observed indication of zero flow and pressure in the NSW header. The Reactor Operator manually started the standby "A" NSW pump to restore flow, but the pump tripped after running for less than two minutes. When re-start attempts on the "A" NSW pump failed, a manual reactor trip was initiated at approximately 2342 hours0.0271 days <br />0.651 hours <br />0.00387 weeks <br />8.91131e-4 months <br />. Plant systems responded as expected, including an automatic start of the Auxiliary Feedwater System and the unit was stabilized in mode 3 (Hot Standby).

The cause of this event was a mechanical failure of the "B" NSW pump and the failure of the "A" NSW to remain running once manually started. The "B" NSW pump shaft sheared.

Additional investigation was subsequently completed to determine the cause of the "A" NSW pump trip. This investigation revealed that the torque switch on the pump's discharge valve (ISW-289) was actuating and this was preventing the valve from opening to the 10% open position, which is required for pump operation.

Corrective actions included restoring the "A" NSW pump to service, performing a secondary plant walkdown to support plant re-start and evaluating the acceptability of having only one NSW pump available during plant operation while repairs continued on the "B" NSWgpump. Subsequent actions included restoring the "B" NSW pump, completing the failure analysis for tlie "B" NSW pump sheared shaft, and completing the additional investigation into the

'" NSW pump trip that resulted in this LER revision.

This event is reportable per 10CFR50.72 and 10CFR50.73. A 4-hour non-emergency report was made to the NRC at approximately 0207 via the emergency notification s stem.

9708200013 970807 PDR ADOCK 05000400

Q4 U.S. NUCLEAR REGUIATORY COMMISSION NRC FORM 366A (4-95)

LICENSEE EVENT REPORT (LERj TEXT CONTINUATION DOCKET LER NUMBER )6) PAGE I3)

FACILITY NAME (I)

SEOUENHAL REYISION YEAR NUMBER NUMBER Shearon Harris Nuclear Plant Unit )I)1 50400 2 OF 3 96 - 018 - 01 TEXT Pl mort spore r's rer)viK vse oW(kvl sopor ol NRC Form 3664) (17)

EVENT DESCRIPTION:

"B" On September 3, 1996 at approximately 2338 hours0.0271 days <br />0.649 hours <br />0.00387 weeks <br />8.89609e-4 months <br />, with the plant operating in mode 1 at 100% power and the Normal Service Water pump (NSW, EIIS Code: KG-P) in service, operators in the main control room received numerous NSW system alarms and observed indication of zero flow and 'pressure in the NSW header. The Reactor Operator manually started the standby "A" NSW pump to restore service water flow..After observing closed indication for the "A" NSW pump breaker and indication that the "A" NSW pump discharge valve was opening, the "B" NSW pump was secured to allow the "B" discharge valve to shut. At this time, the Reactor Operator noticed that the "A" NSW pump had tripped. Following two unsuccessful re-start attempts on the "A" NSW pump, the Unit-Senior Control Operator directed a manual reactor and turbine trip at approximately 2342 hours0.0271 days <br />0.651 hours <br />0.00387 weeks <br />8.91131e-4 months <br />. Prior to the reactor trip, the "A" Emergency Service Water (ESW) pump automatically started due to low header pressure. Plant systems responded to the reactor trip signal as expected, including an automatic start of the Auxiliary Feedwater System (EIIS Code: BA) on steam generator low-low level due to Reactor Coolant System (RCS, EIIS Code: AB) shrink following the reactor trip. The unit was stabilized in mode 3 with RCS temperature at 557 degrees and pressure at 2235 psig.

Following investigation and repairs, the plant was restarted on September 9, 1996 and returned to the grid at approximately 0342 on September 10, 1996. Delays were encountered in plant re-start due to the passage of Hurricane Fran (reference LER 96-019). Since the forced outage exceeded 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, hot rod drop testing was performed prior to reactor startup in accordance with Harris Plant's response to NRC Bulletin 96-01. Reference Attachment 1 for hot rod drop testing results.

I This event is reportable per 10CFR50.72 and 10CFR50.73 as a Reactor Protection System actuation. A 4-hour non-emergency report was made to the NRC at approximately 0207 via the emergency notification system.

CAUSE:

The cause of this event was a mechanical failure in the "B" NSW pump and a malfunction resulting in the "A" NSW pump tripping after being manually started. The "B" NSW pump experienced a sheared pump shaft. A metallurgical analysis determined the most probable cause to be a bent pump shaft due to alignment problems, which caused the bronze bearings to heat up and fail resulting in the sheared pump shaft.

Additional investigation was subsequently completed to determine the cause of the "A" NSW pump trip. This investigation revealed that the torque switch on the pump's discharge valve (1SW-289) was actuating when high D/P conditions exist across the valve and this was preventing the valve from opening to the 10% open position, which is required for pump operation. These high D/P conditions are present when the standby NSW pump starts with the other NSW pump not running, as in the case of the "B" NSW pump trip.

SAFETY SIGNIFICANCE:

There were no safety consequences as a result of this event. The manual reactor/turbine trip was initiated per plant operating procedures to protect secondary plant components following the loss of Normal Service Water. Plant systems responded as expected following the initiation of the manual reactor/turbine trip.

A )4- )

4, NRC FORM 36BA U.S. NUClEAR REGUIATORY COMMISSION (495)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACIEITY NAME (I) OOCKET lER NUMBER (6) PAGE (3)

SEQUENTIAl REVISION FEAR NUMBER NUMBER Shearon Harris Nuclear Plant - Unit /Il 50400 3 OF 3 96 - 018 01 TEXT illmoro spsco r's rcrprisrl oso orrrpsotrol coper ol llRC Form 3SQI I) T)

PREVIOUS SIMILAR EVENTS:

Previous similar problems with the NSW pumps and discharge valves were experienced during the reactor/turbine trip that occurred on April 25, 1996, which was reported in LER 96-008. Corrective actions for that event included adjusting the mechanical latch mechanism on the "A" NSW pump discharge valve control relay (CR1/2189) to ensure that it "latched in" properly and replacing two of the "B" NSW pump discharge valve control relays (CR4/2190 &

CR1/2190) that experienced intermittent failures. Based on indications observed during the September 3, 1996 loss of NSW event, these corrective actions were effective since their associated functions performed as required.

LER 96-008 also contained a corrective action to perform additional NSW testing during the next refueling outage (RFO-7). This testing was performed and the results will be included in a revision to LER 96-008.

CORRECTIVE ACTIONS COMPLETED:

1. Trouble shooting was performed which determined that a common-mode failure mechanism did not exist with the NSW pumps.

2. The "A" NSW pump was returned to service on September 7, 1996.

3. A safety analysis was performed on September 5, 1996, which determined the acceptability of returning the plant to service with only one NSW pump available while repairs continued on the "B" NSW pump. This analysis, combined with the results of an engineering evaluation, concluded that repairs to the "B" NSW pump could be made on-line with the "A" NSW pump in service.

4. A secondary plant walkdown to assess potential damage related to the loss of NSW transient was completed on September 4, 1996. Discrepancies identified during the walkdown that would prevent plant re-start were repaired on September 4, 1996.

Repairs were completed and the "B" NSW pump was returned to service on October 29, 1996.

Additional analysis was performed to determine the failure mechanism involved in the "B" NSW pump sheared shaft and the results are provided above in the cause section. This analysis was completed on November 15, 1996.

Additional testing and evaluation was performed to determine the cause of the "A" NSW pump trip after being manually started on September 3, 1996. The results are described above in the cause section. Follow-up actions to address the torque switch issue include; (1) A new discharge valve (1SW-289) was installed to improve the disc seating area and require less torque to open the valve, (2) The orientation of the valve was changed, which will result in less torque required to open the valve during high D/P conditions, (3) The stop limit switches were re-set such that the valve actuator does not drive the disc as far into the valve seat. This will also result in the need for less torque to open the valve. These actions were completed on May 7, 1997.

Training on the lessons learned from the loss of NSW event was incorporated into the operator training program and was covered during Licensed Operator Re-qualification session //6. This was completed on November 14, 1996.

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