ML20153B525
| ML20153B525 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 07/07/1988 |
| From: | Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-88-004, IEB-88-4, NUDOCS 8807130104 | |
| Download: ML20153B525 (6) | |
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Consumers Power-Kenneth W Berry gyg Director Nuclear L2 censing General Offces: 1945 Wsst Pernall Road, Jackson, MI 49201. (517) 788-1636 July 7, 1988 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT -
RESPONSE TO NRC BULLETIN 88 POTENTIAL SAFETY-RELATED PUMP LOSS NRC Bulletin 88-04, Potential Safety-Related Pump Loss, dated May 5, 1988 requires Consumers Power Company to determine if pump-to-pump interactions resulting in dead-heading of the pumps occurr and, if so, to perform an evaluation of the dead-heading impact on safe plant operations.
It also requires an evaluation of the adequacy of the minimum flow requirements for safety-related pumps and a written response to be submitted within 60 days of receipt of the bulletin. Our response to the concerns of the bulletin are provided herein.
With respect to-the two concerns regarding pump performance during minimum flow conditions, all safety-related pumps in the ASME pump inspection program, and their piping configuration were reviewed (reference Table 1).
The inspection program monitors both core spray pumps (P-2A and B), the electric fire pump (P-6) and the diesel driven fire pump (P-7).
An evaluation of the system configuration and operation requirements for the above pumps has determined that the stronger versus weaker pump concern does not exist. All pumps, when required to operate during non-testing events are full flow pumps. The operating procedures specify only one core spray pump is operated at a time. Although both pumps share a common header, this i
operational requirement precludes parallel pump operation. Subsequently, the conditions for one pump to dominate the other are not established.
The operational requirements of the Fire Protection System differ from those of the Post Incident System which includes che core spray pumps.
Parallel operation of both fire pumps is possible during non-testing activities depend-ing on the initiating event. Decreasing fire header pressure will start the electric fire pump at 70 psig and then the diesel driven fire pump when 60 psig is reached. This would occur only when the flow requirements exceed the capacity of the electric fire pump. The Reactor Depressurization System (RDS) also starts both pumps upon reaching a decreasing steam drum level of pd OC0788-0061-NLO4
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Nuclair Rsgulatory Commission 2
Big Rock Point Plant Response to Bulletin 88-04 July 7, 1988 17 inches below steam drum center line. Both pumps are additionally capable of manual initiation. As stated earlier, these pumps are full flow pumps in either a single or parallel operating configuration.
Should a system demand be placed upon the fire pumps, and should they be required to pump in parallel, they would be operating in a high flow condition which precludes a strong versus weak pump confrontation. A review of the minimum flow configuration of both fire pumps during an RDS or Core Spray System start demand was conducted, This is the only occasion that parallel operation of both fire pumps is required because of system logic. The worst case casualty scenario for parallel fire pump operation is during a small leak LOCA. At 17 inches below steam drum center line level and decreasing, both pumps start and a two minute timer in the RDS system actuation circuitry begins. At the end of the two minute period the remaining RDS actuation logic is expected to be setisfied, with subsequent primary system blowdown. During the two minute delay tha fire pumps are running in a minimum flow configuration. Both fire pumps utilize independent relief valves during this interval to achieve minimt.m flow. The relief valves are set at 19 gpm which is approximately 2%
of rated flow. Once the RDS system actuation logic has been satisfied, it takes 30 seconds of primary system blow down to reach a pressure which allows full flow from the fire pumps. The total time elapsed with the fire pumps running in a minimum flow configuration approaches 150 seconds. Operating both pumps in parallel for this duration is not considered a threat to component integrity or performance. Subsequently, it can be concluded that system demands and operational requirements placed on the core spray pumps and the fire pumps do not establish a pump-to-pump interaction which could result l
in one pump overwhelming the other. Nor is the adequacy of minimum flow a concern during these non-testing demands. No further action is considered necessary at this time.
The system configurations required for routine testing of these pumps were evaluated for pump-to-pump interaction as well as recirculating flow adequacy.
Surveillance testing associated with the core spray pumps was researched (reference Table 2).
Only one test that required core spray pump operation was found. One purpose of that test is to verify correct core spray pump flow at rated conditions. The pumps are operated separately and at full flow which precludes the concerns identified in the bulletin. No further action regarding the core spray pumps and minimum flow concerns are considered necessary at this time.
Lastly, the routine surveillance testing involving either fire pump was researched (referenced Table 2).
The review determined that system configurations in two of the tests allowed minimum flow of a fire pump for 30 minutes. Minimum flows for these pumps is provided via the independent relief valves discussed earlier. The 19 gpm, or approximately 2% of rated flow, is less than the minimum flow capacities suggested in the bulletin.
However, no degradation in pump performance has been noted to date as a result of operating under these conditions. Both fire pumps are included in the ASME pump inspection program which is based on component performance in accordance vith system design criteria.
This program not only monitors flow capacity, but also trends other indicators of pump performance such as differential OC0788-0061-NLO4
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Big Rock Point Plant Response to Bulletin 88-04 July 7, 1988 pressure, vibration, RPM, etc.
In addition, the surveillance testing program serves as a continuing demonstration of system and component reliability.
Based upon these established and ongoing indicators of pump performance, failure of either fire pump is not anticipated.
Although no degradation in either fire pump behavior has been observed, the comparative value of maintaining or improving performance of these components is deemed prudent. The following long tarm actions are intended to insure that current vendor recommendations regarding minimum flow conditions are considered and incorporated into system operations and testing practices as appropriate. The proposed completion date for these actions is by the end of second quarter, 1989.
- 1) Contact pump vendor and obtain minimum flow recommendations and their basis for both fire pucps in their present applications.
- 2) Evaluate existing fire pump surveillance testing relative to the vendor recommendations and either revise procedures to incorporate the recommendations or propose system modifications which will satisfy the vendor recommendations.
- 3) Evaluate the necessity of a pump impeller inspection for both fire pumps, and schedule if necessary.
In conclusion, the concerns identified within the bulletin are not perceived to jeopardize existing pump reliability. The only potential exception to this occurs during routine testing of the fire pumps. Certain current testing configurations for these pumps establishes a minimum flow condition for short periods of time, ie, 30 minutes per week for the diesel driven fire pump and 30 minutes per month for the electric fire pump. These periods of minimum flow have been incurred over the last twenty-six years of plant operating history and have not appeared to degrade pump performance.
Past, present and continuing surveillance testing results, as well as the ASME pump inspection program emphasizes this observation. Therefore, the above discussion is considered to provide and support justification for continued operation until completion of the long-term actions.
In the interim, the need for short-term action is determined unnecessary in the interim.
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L # va-y Kenneth W Berry l
Director, Nuclear Licensing CC Administrator, Region III, NRC NRC Resident Inspector - B.g Rock Point OC0788-0061-NLO4 b
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CONSUMERS POWER COMPANY Big Rock Point Plant Docket 50-155 License DPR-6 NRC Bulletin 88-04 At the request of the Commission and pursuant to the Atomic Energy Act of 1554 and the Energy Reorganization Act of 1974, as amended, and the Commission's Rules and Regulations thereunder, Consumers Power. Company submits our response to NRC. Bulletin 88-04 dated May 5, 1988, entitled, "Potential Safety-Related Pump Loss."
Consumers Power Company's response is dated July 7, 1988.
CONSUMERS POWER COMPANY By' -l DavidPHoffman,Vice\\(fp()yent Nuclear Operations Sworn and subscribed to before me this 7th day of July 1988.
Elaine E Buehrer, Notary Public Jackson County,' Michigan-
-My commission expires October 31, 1989 5
OC0788-0061-NLO4
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.s i-TABLE 1 Safety Related Pumps Evaulation Equipment.
Pump Number System Rating
- 1 Core Spray Pump P-2A Post Incident Sys. tem 400 gpm @ 120 psig
- 2 Core Spray Pump P-23 Post Incident System 400 gpm @ 120 psig Electric Fire Pump P-6 Fire Protection System 1000 gpm 0 110 psig Diesel Fire Pump P-7 Fire Protection System 1000.gpm 0 110 psig
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TABLE 2
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. Surveillance Tests Test Pumps Number Title Utilized T7-20 Diesel Fire Pump Auto Start P-7 T7-28 Emergency Diesel Generator Auto P-6 Test Start T30-14 Monthly Core Spray Heat Exchanger P-6 or P-7 Leak Test T365-11 Post-Winter' Hydrant Check P-6 or P-7 T365-12 Pre-Winter Hydrant Check P-6 or P TR-09 Core Spray Haat Exchanger Shell P-6 Side Flow TSD-01 Fire Pump Operating Characteristics P-6 and P-7 TSD-04 Full Flow Testing of the Core Spray P-6 or P-7 System Inlet TSD-07 Core Spray Pump Run and Tes,t Loop P-2A and 2B Operation TV-23 Fire Water System Flow Test P-6 and P-7 i
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