ML20033E095
| ML20033E095 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 02/27/1990 |
| From: | Cockfield D PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-004, IEB-88-4, NUDOCS 9003080498 | |
| Download: ML20033E095 (5) | |
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David W. Cockfield Vice PresWent, Nuclear February 27, 1990 Trojan Nuclear Plant Docket 50-344 License WPF-1 U.S. Nuclear Regulatory Commission Attnt Document Control Desk Washington DC' 20555 b
Dear Si.'s:
'WRC Bulletin 88-04. Potential Safetv-Related Pumo Loss By letter dated September 28, 1989, Portland General Riectric Company (PCE) connitted to providing a final closnout of Bulletin 88-04 by January 15, 1990. The initial response to Bulletin 88-04, dated July 18, 1988, did not.
completely address all of the Bulletin items because pump vendor information had not been received. The initial response committed to provide an updated response following receipt and evaluation of pung minimum flow reconnendations.
i:
On January 16, 1990 (January 15 being a federal holiday), your staff was notified by telephone that the pump vendor information was still not available and it was verbally agreed that PCE would provide a new schedule once one was finalized.
The attachment to this letter provides an update to the initial Bulletin p
88-04 response, in accordance with the schedule verbally provided to the Trojan Project Manager and Region V personnel on February 6,1990.
h Sincerely.
p Attaciunent '
c Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. David Stewart-Smith State of Oregen Department of Rnergy Mr. R. C. Barr NRC Resident Inspector Trojan Nuclear Plant 9003080498 900227
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PDR ADOCK 05000344 PNV g
121 S.W. Salmon Street, Portland, Oregon 97204,503/464 8897 b
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Trojan Nuclear plant Document Control Desk l
Docket 50-344 February 27, 1990 i
License NPF-1 Attachment l
l page 1 of 4 l
u UPDATED SUNKARY OF EVALUATION OF NUCLEAR REGULATORY CONNISSION (NRC) BULLETIN 88-04 t
i The following response presents an updated assessment of the actions requested by NRC Bulletin 88-04, " Potential Safety-Related Pump Loss",
i Each of the " Actions Requested" items will be completely addressed when information from all pump vendors has been received and evaluated.
The schedule for receipt and evaluation of pump minimum flow recommendations is provided in Section C below.
I A.
AFFECTED SYSTEMS AND ISSURS
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I Safety-related centrifugal pumps with minimum flow recirculation paths were evaluated for minimum flow operation and pump-to-pune interaction.
Because updated pump vendor recommendations were not i
available to incorporate into the initial response it could not be i
concluded that the existing vendor-specified minimum flow rates were i
acceptable. This situation is being reevaluated in accordance with the actions and schedules delineated in Section C below. Conclusions to date-regarding the potential for pump-to-pump interaction under minimum flow conditions are discussed below.
1.
Auxiliary Feedwater Pumps, t
The auxiliary feedwater pumps have separate discharge headers and miniflow paths that are protected against backflow by check valves, thus the minimum flow paths remain independent to the common return line to the Condensate Storage Tank, i
2.
Safety Injection Pumps. Centrifugal Charalna Pumps.
The centrifugal charging pumps and safety injection pumps miniflow design has flow paths that are train-independent with a check valve separating the pump discharges, and separate high-pressure drop orifices in each line, prior to a common miniflow discharge line.
Given the high-discharge pressure of these pumps, the high-pressure drop orifices mitigate backpressure effects which could cause pump-to-pump interactions which would affect the minimum flow. The pump vendor has confirmed the existing minimum flow recommendations for these pumps.
3.
Containment Spray Pumps.
The Containment spray pumps have separate headers and no miniflow under accident conditions, and are tested only under minimum flow conditions. Thus, the minimum flow considerations do not apply for accident conditions for these pumps.
1 Trojan Nuclear Plant Document Control Desk Docket 50-344 February 27, 1990 License NPF-1 Attachnent page 2 of 4 4.
Residual Heat Removal (RNR) Pumps.
The RHR pumps have a miniflow design with individual flow paths for each pump which open automatically on a low-flow signal (less than 800 spa).
The miniflow valves automatically close on a high-flow signal with flow greater than 1,375 spm. However, the RHR pump discharge and miniflow paths share a coumon header such that pump-to-pune interaction during miniflow operation is not precluded. This situation is further discussed in Section B below.
5.
Boric Acid Transfer Pumps.
The boric acid transfer pumps are operated and tested with a recirculation flow path that is manually aligned. A potential common header flow path is not aligned.
The pumps do not receive an automatic start signal and are under manual control with one pump on recirculation and the other pump in standby.
This precludes pump interaction under miniflow conditions.
Therefore, no further evaluation of these pumps is necessary.
B.
SHORT-AND LONC-TERN CORRECTIVE ACTIONS Minimum Recirculation Flow.
To address short-term considerations about the adequacy-of pump minimum flow rates, the above-described pumps were reviewed and found-to be in conformance with pump vendor recommendations. As part of 6he long-term corrective actions, updated recommendations from manufacturers of the affected pumps will be evaluated for the minimum flow requirements in accordance with the schedule provided in Section C below.
Pump Interaction.
In the initial response to Bulletin 88-04, Portland General Electric Company (PCE) concluded that strong pump / weak pump interactions were not significant for Trojan RHR pumps primarily because of the small difference in pump developed head While on miniflow.
Subsequent quarterly testing indicates that the initial conclusions may not be correct. PCE's corrective actions for this include a' procedure revision, additional testing, and further evaluation of the mininum flow requirements. Final resolution will be determined consistent with the schedule provided in Section C below. Since pump wear occurs slowly under normal operating conditions, degradation in pump operating characteristics will be detected by the quarterly tests before it becomes significant.
k.* 4 Document Control Desk l
Trojan Nuclear plant Docket 50-344 February 27,'1990
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License NpF-1 Attachment page 3 of 4 q
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C.
SCHEDULE FOR LONG-TERN RESOLUTION 1
Long-term resolution of this issue will be in accordance with the j
following actions and schedules 1.
Auw111ery Feedwater pumps.
a.
Receive minimum flow information from pump vendor - June 30, i
1990 (estimated).
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b.
Evaluate minimum flow information against available test i
data and operating conditions - within 60 days of completion of Item a.
2.
Containment Sprav Pumps.
a.
Receive minimum flow information from pump vendor - June 30, 1990 (estimated),
b.
Evaluate minimum flow information against available test data and operating conditions - within 60 days of completion of Item a.
3.
Residual Heat Removal Pumps.
a.
Receive minimum flow information from pump vendor -
April 15, 1990 (estimated).
b.
Evaluate minimum flow information against available test data and operating conditions - within 60 days of completion of Item a.
c.
perform test and evaluate two RHR pumps running with miniflow valves open - July 30, 1990.
d.
Evaluate test results and make procedure changes as necessary - September 30, 1990.
D.
JUSTIFICATION FOR CONTINUTED OPERATION Continued operation with the potential for strong pump / weak pump interaction in the RHR System has been evaluated. The probability of a strong pump / weak pump interaction is low, primarily because (1) planned pump operation under miniflow conditions is in conformance with the manufacturer's recommended miniflow criteria, (2) the degradation of one of the pumps leading to strong pump / weak l
pump interaction is expected to occur over a sufficiently long period of time to allow its identification during periodic testing, and ll
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is Trojan Nuclear Plant Document Control Desk Docket 50-344 February 27, 1990 License NPF-1 Attachment-page 4 of 4 (3) the pumps-are tested quarterly and past data have not indicated any significant changes in pump characteristics when instrument and calibration changes are taken into account. The type of event where the minimum flow interaction could take place is limited to small-break Loss-of-Coolant Accidents (LOCAs) where the RHR pumps are needed for long-term recirculation cooling of the core. Quality materials, construction, inspection, and lesk-testing of the Reactor i
Coolant' System provide reasonable assurance that a small-break LOCA is a low probability event. Operating procedure changes ensure that RHR pumps will not operate in a mode.that could degrade a pump over a prolonged period at low flow.
The nature of the pump-to-pump interaction is such that the degraded i
pump would not suddenly lose all minimum flow capability. Rather, the minimum flow would decrease below the 500 spm recommended value.
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Evaluation of the Turkey point RHR pumps with no flow showed 10 minutes of operation was permissible.
The Trojan RHR pumps are similar;(Ingersoll-Rand 8x20WD) to the Turkey point RHR pumps (Intersoll-Rand 8K20W) and thus, pump deadheading is not expected to cause prompt pump damage, rurthermore, a small amount of minimum flow extends the period before pump damage occurs.
Procedural changes limit.the period of operation with reduced minimum flow so that pump damage does not occur.
overall, it is judged that continued operation is acceptable based on the assessment of minimum flow criteria and procedure changes to preclude pump interaction.
RMN/DRS/GRA/bsh 4321W.0290 F
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