ML20029A586
| ML20029A586 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 02/15/1991 |
| From: | Cintula T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | |
| Shared Package | |
| ML20029A574 | List: |
| References | |
| TASK-AE, TASK-T91-02, TASK-T91-2 AEOD-T91-02, AEOD-T91-2, NUDOCS 9102250281 | |
| Download: ML20029A586 (3) | |
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AEOD TECl!NICAL REYlEW REPORT UNIT:
Brunswick Unit 2 TR REPORT NO.: AEODd91-02 DOCKET NO.:
50-324 DATE: Pebruary 15, 1991 LICENSEE:
Carolina Power & Light Co.
CONTACT: T. Cintula i
SUBJECT:
INCORRECT ROTATION OF PDP i
SUMMARY
One positive displacement pump (PDP) at Bnmswick Unit 2 was wired incorrectly. The pump rotated % the reverse direction (backwards) which could cause an internal lubrication problem. _We concluded a PDP operating with reversed rotation would not affect plant safety at either boiling water reactors (BWRs) or pressurized water reactors (PWRs).
i DISCUSSION
- 1. Event Description and Cause After maintenance, the PDP was observed to be rotating in the reverse (backwards) direction.
The PDP, with reverse rotation, was one of two PDPs in the safety related standby liquid control (SLC) system at Brunswick Unit 2. Nothing in the maintenance procedure could have affected the rotational direction of the PDP motor. Subsequent investigation found two electrical power Icads to the pump motor had been interchanged at the motor control center.
After that, the three phase pump motor simply rotated in the reverse direction. Since the motor control center Icads were not part of the PDP maintenance procedure, it was not possible to determine when reverse rotation occurred. Rotational checks of the SLC pumps are routinely conducted following maintenance at Bnmswick. Ilowever, it is possible at some time in the past, this was not correctly performed.
- 2.. Consequence of Reverse Rotation The SLC pumps are positive displacement reciprocating piston pumps. Direction of rctation has no effect on their pumping ability. Therefore, periodic surveillance of pump operation, if only limited to pump output pressure or pump flow rate would not reveal reverse rotation of the pump.
Ilowever, reversed rotational operation does affect internal drive train pump lubrication. The j
pump lubrication system depends on the crankshaft throw to fill an elevated reservoir which i
then drains oil over the drive pistons, thus providing lubrication. The pump vendor, Union l
Pump, informed the licensee, that sufficient short term oiling of the drive pistons would occur 9102250281 910215 PDR ADOCK 05000324.
P PDR
2 during reverse rotation at the relatively slow rotational speed of the SLC pumps at lirunswick.
liigher RPM pumps would not receive sufficient lubrication from oil splash. Also, extended re.*erse operation could cause excessive wear at the pump seal. The wear would be detectabic by oil leakage at the pump seals.
- 3. Observed Effect of Pump Reverse Rotation at Brunswick Although the total duration of SLC pump operation with reverse rotation could not be determined, the licensee estimated the pump operates at a usage rate of 15 minutes per month.
Vibration measurements indicated the effect of reverse rotation was negligible. Also, no wear was evident by oil leakage at the pump seals. The licensee concluded that the indefinite period of reverse operation did not render the pump inoperable. The NRC Inspector (Ref.1) determined that, if called upon to function in an actual event, the pump would have to operate two hours to inject the contents of the SLC storage tank given the single failure of the redundant SLC pump. The inspector concluded that in its current state, pump failure within two hours did not seem likely.
- 4. Safety Concerns with PDPs
- a. Boiling Water Reactors (BWRs)
The SLC system is designed to provide a redundant, independent, backup control mechanism capable of shutting down the reactor and maintaining it in a shutdown condition in the event that the control rod system is totally inoperable. The analyzed accident for the SLC system is an anticipated transient without scram (ATWS). The SLC system at Brunswick is designed to satisfy the ATWS rule by providing the capability of operating both PDPs simultaneously at a flow rate of 82 gpm which will inject highly borated solution from the SLC tank in 29 to 59 minutes, injection with a single PDP would require 58 to 113 minutes of operation,
- b. Pressurized Water Reactors (PWRs)
PDPs may also be used for injection as charging pumps in the chemical and volume control system (CVCS) at pressurized water reactors. Some Westinghouse designs have one PDP and two centrifugal pumps in their charging systems, in these designs, the PDP is always designated as a nonc.fety component and the two centrifugal charging pumps provide the needed plari safety functions.
Many Combustion Engineering plants use three PDPL t.s the only injecting force in the charging system, in this plant design, the PDPs are not part of the emergency core cooling system, but some plants take credit for injection flow from the PDPs in some accidents. For example, the long term cooling analysis for San Onofre Units 2 and 3 assumes that charging (from one of PDPs) is terminated between 1.5 and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after initiation of the LOCA.
PDPs are not used at Babcock & Wilcox Plants.
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- 5. Search for Similar Events of Reversed Pump Rotation The Nucicar Document System-Advanced Design (NUDOCS/AD) was used to search for other events involving reverse rotation of PDPs; none were found. 'Ihc search was then expanded to Ond events of reverse rotation of any pump. There was no record of a pump operating with reverse rotation in the data base.
FINDINGS PDPs are a safety related component for all BWRs, as the injection source of the SLC system and some PWRs take credit for the PDP injecting in the small break LOCA analysis. Reverse pump rotation does not affect the pumping characteristics of a PDP, i.e., actual Dow rate and.
pressure head, but may lead to pump lubrication problems with extended reversed rotation usage..The licensee concluded that the reverse rotating PDP at Brunswick could _ operate for two hours. The safety analyses for both BWRs and PWRs are satisned with two hours of PDP operation, and, in either case, a redundant PDP is available. Reverse rotation of a PDP may be a rare occurrence, with the only documented event occurring at Brunswick 2.
CONCLUSIONS
, Reported c,ents of reversed PDP operation have not occurred. Should reverse operation occur, the PDP will fulnll its safety function in terms of pressure head, Dow rate and duration of operation. Accordingly, plant safety should not be degraded if the PDP is wired to operate with reversed rotation.-
.OTilER CONSIDERATIONS l
Apparently, reverse rotation of a PDP will occur whenever the electrical power leads are -
switched in the electrical supply to the PDP motor. Although safety consequences associated with this error are limited, reverse rotation is not desircable due to long term degradation of
' the PDP, and it.would be appropriate to inform licensecs of the potential for reversal of pump j
operation and consequences, i
REFERENCE-4 1,: NRC Inspection Report Numbers: 50-325/90-11 and 50-324/90-11, dated April 17, 1990, l
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