ML20005E080

LER 89-032-00:on 891205,RHR Pumps Determined to Have Deadheading Problem,Per NRC Bulletin 88-004,resulting in Plant Operation Outside Design Basis.On 891128,RHR Pump Exceeded Head Criteria.Pumps started.W/891222 Ltr

ML20005E080
Person / Time
Site:	Sequoyah
Issue date:	12/22/1989
From:	Bynum J, Proffitt J TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-004, IEB-88-4, LER-89-032, LER-89-32, NUDOCS 9001030221
Download: ML20005E080 (5)

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, . TENNESSEE VALLEY AUTHORITY l - ': .

I 6N 38A Lookout Place December 22, 1989 i:

U.S. Nuclear Regulatory Commission 1

ATTN: Document Control Desk Washington, D.C. 20555 ,

Gentlemen: 1 TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.

50-327 - FACILITY OPERATING LTCENSE DPR LICENSEE EVENT REPORT (LER) 50-327/89031 J

The enclosed LER provides details concerning an inadequate program developed in response to NRC Bulletin 88-04 that allowed a deadheading condition to '

develop for the residual heat removal pumps. This condition resulted in the plant being in a condition that was outside its design basis. This event is ,

being reported in accordance with 10 CFR 50.73, paragraph a.2.ii.B.

Very truly yours.

TENNESSEE VALLEY AUTHORITY  ;

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. R. Bynum, ce President Nuclear Power Production Enclosure cc (Enclosure):

Regional Administration ,

U.S. Nuclear Regulatory Commission '

Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 .,

INPO Records Center '

Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500

. Atlanta, Georgia 30339 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 l

9001030221 891222 ' l PDR ADOCK 050003'27 S PDC An Equal Opportunity Employer

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On December 5, 1989, at 1912 Eastern standard time (EST) with Unit 1 in Mode 1 (66 percent power, 2,235 pounds per square inch gauge (psig} and 561 degrees Fahrenheit

[F)) and Unit 2 in Mode 1 (100 percent power, 2,235 psig and $78 degrees F), the Unit i residual heat removal (RHR) pumps were determined to have the deadheading problem identified by NRC IE Bulletin 88-04. Operations personnel entered Limiting Condition for Operation (LCO) 3.5.2 at this time.

Operation of both pumps confirmed that during parallel pump operation, the IB-B RHR pump would seat the 1A-A RHR pump's discharge check valve, located between the pump and the ciniflow line. As a result, the IA-A RHR pump will be running " deadheaded," i.e., with no flow through the pump. Analysis showed that operation in this configuration for periods longer than 11 minutes would cause pump damage. Operations personnel placed the Unit 1 B train RiiR pump in the pull-to-lock position resulting in the pump being inoperable. However, this configuration eliminated the potential for simultaneous pump cperation and allowed time to initiate procedure revisions as short-term corrective cetion. TVA revised the emergency operating procedures to resolve the immediate cperability concern and exited LCO 3.5.2 at 1825 on December 8, 1989. Other associated plant procedures will N revised to ensure that if the pump-to-pump differential pressure exceeds 11 pounds per square inch differential, appropriate corrective actions l will be taken. Additionally TVA will re-evaluate NRC Bulletin 88-04 and will revise

the response based on the evaluation results. The cause of this event was an inadequate

! program / review of the data in preparing the response to the NRC Bulletin.

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0l0 0l2 0F 0l4 l e onw.m..anewnec w man un De,'eription of Event On December 5, 1989, at 1912 Eastern standard time (EST) with Unit 1 in Mode 1 (66 percent power, 2,235 pounds per square inch gauge (psig) and 561 degrees Fahrenheit

[F]) and Unit 2 in Mode 1 (100 percent power, 2,235 psig and 578 degrees F), the Unit 1 RER pumps were determined to have the deadheading problem identified in NRC Bulletin 88-04. As an immediate corrective action to prevent simultaneous pump cperation. Operations personnel placed residual heat removal QHR) pump 1B-B in the pull-to-lock position resulting in the pump being inoperable M11S Code BP). Operations p3rsonnel entered Limiting Condition for Operation (LCO) 3.5.2.

On November 28, 1989, during the performance of Surveillance Instruction (SI) 128.4, .i

" Residual Heat Removal Pump 2A-A Quarterly Operability Test," RHR pump 2A-A exceeded its d;veloped head criteria as specified in the SI. Additional testing was performed, and the pump was still exceeding the delta pressure requirements. This results in the Unit 2 RHR pumps exceeding the pump delta pressure requirements of eight pounds per square inch differential (psid) indicating a potential for deadheading of the Unit 2 RHR pumps. The pumps were determined to be acceptable / operable in accordance with American Scciety of Mechanical Engineers,Section XI, pump testing requirements. TVA performed  ;

en engineering evaluation that demonstrated the differential pressure between A and B ,

train pumps did not exceed the 11.1 psid limit associated with pump deadheading concerns.

The operability of the Unit 1 RHR pumps were subsequently evaluated. The differential pressure between the Unit 1 pumps was approximately 17 psid. To resolve the deadheading ccncern, both Unit 1 RHR pumps were started and run simultaneously in the normal system clignment. The 1B-B pump indicated a flow of approximately 1.150 gallons per minute (gpm) while the 1A-A pump indicated no flow. This confirmed that during parallel pump operation, the IA-A RHR pump was running deadheaded, i.e., with no flow through the pump. Engineering calculations showed that operation in this configuration for periods longer than 11 minutes would cause pump damage. The emergency procedures were revised to stop both RHR pumps if the RCS pressure was greater than 180 psig. After discussions b3 tween 'IVA and NRC, the emergency procedures were subsequently revised to check if one of the RHR pumps should be stopped. Thus, ensuring operability of the system.

LCO 3.5.2 was exited at 1825 on December 8, 1989.

The Unit 2 RHR pumps were also started to ensure that the deadhead problem did not exist on Unit 2. Both pumps achieved expected flow rates, thereby ensuring an unacceptable pump-to-pump interaction did not exist on Unit 2.

Ctuse of Event The root cause of this event was an inadequate program / review of the data in preparing the response to NRC Bulletin 88-04, " Potential Safety-Related Pump Loss." The ovaluation of the RHR pump-to-pump interaction was based on an average of the pump-to-pump differential pressure data. The averaging of the data was performed to eliminate statistical variations associated with the data. Testing with both pumps running was not performed at the time because it appeared that the differential pressure limits were met. The pump monitoring program was not sufficient to identify adverse trends or immediate operability problems. This event occurred as a result of an error in judgement and inadequate review of the problem identified by the bulletin.

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Organisational changes in Nuclear Engineering and Technical Support have been made since the problem was initially evaluated. These changes are intended to improve crganizational accountability and to ensure that the proper standards, policies, and cdministrative controls are enforced.

- Analysis of Event This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.ii, as a etndition that resulted in the nuclear power plant being in a condition that was outside the design basis of the plant.

During accident conditions, the RHR pumps provide automatic low-head safety injection flow to the RCS following a safety injection signal (SIS) and also, provide suction flow

, to the centrifugal charging pumps (CCPs), and the safety injection pumps (SIPS) after i

changeover to the containment sump from the refueling water storage tank (RWST).

Specifically, at least one train of low-head safety injection flow (assuming a single cctive failure of the redundant train) is required to mitigate a large-break loss of crolant accident (LOCA). The RER low-head safety injection flow is assumed to be d311vered to'all four cold legs. During a LOCA, three of these flow paths deliver flow

.to the RCS with the fourth assumed to be spilling from the faulted leg.

If a safety injection signal had been initiated due to a small-break LOCA, both RHR pumps would have started resulting in deadheading of the lower head pump. If not shut dtwn within approximately 11 minutes, this pump may have sustained damage and could therefore not be relied on to perform its intended function. Such a f ailure is a comon cause failure which must be assumed concurrent with a single failure. If the single failure is assumed to be on the other train of RHR, RHR would have been unavailable and the plant would be outside of its design basis.

Corrective Actions Immediate corrective actions included placing the IB-B RER pump in the pull-to-lock position to ensure one train of ECCS was operable. Subsequent corrective actions included revising Emergency Instruction E-0, " Reactor Trip or Safety Injection " to ,

check if one RHR pump should be stopped. If the reactor coolant system (RCS) pressure  !

is greater than 180 psig and both RHR pumps are running, then one RHR pump shall be stopped and placed in standby. System Operating Instruction (SOI) 74.1 will be revised by January 5, 1990, to ensure that the RHR pumps are not run in parallel on miniflow for greater than 10 minutes. SI-754.1, " Residual Heat Removal Pump 1A-A and 1B-B Comparison Calculation," and SI-754.2, " Residual Heat Removal Pump 2A-A and 2B-B AP Comparison Calculation," will be revised to indicate that if the pump-to-pump differential pressure exceeds 11 psid, then appropriate corrective actions will be taken. The pump-to-pump differential pressure will continue to be monitored and evaluated by the system engineer.

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Additionally, TVA will review its response to NRC Bulletin 88-04 and determine the Itng-term corrective action for the pump-to-pump interaction. TVA will issue a revised rcsponse to NRC Bulletin by March 1, 1990. The response will include the long-term ctrrective actions to resolve this issue. TVA also reviewed the responses to all other cpplicable NRC Bulletins from 1986 to present and has identified no problems with the current responses.

Additional Information There has been one similar reported occurrence where testing associated with the RHR pumps resulted in the plant being outside the design basis (SQR0 50-327/89011).

Commitments

1. TVA will revise its response to NRC Bulletin 88-04 by March 1, 1990.

2. SI-754.1 and SI-754.2 acceptance criteria will be revised such that if the pump-to-pump differential pressure exceeds 11 paid, the appropriate corrective actions are taken. These sis will be revised prior to the next performance currently scheduled for each of its Cycle 4 refueling outage.

3. TVA will revise SOI-74.1 to ensure that the RHR pumps are not run in parallel on miniflow for greater than 10 minutes. This action will be completed by January 5, 1990.

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