ML20245K063

Responds to NRC Bulletin 88-004, Potential Safety-Related Pump Loss. Util Evaluation & Addl Listed Considerations Dictate That Future Component Insp Should Be Performed & Evidence of Pump Degradation Be Continued

ML20245K063
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	06/29/1989
From:	Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-004, IEB-88-4, NUDOCS 8907030281
Download: ML20245K063 (3)

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Consumers Power- Kenneth W Berry j

N or Lkensing nam naaws neanness General Offees: 1945 West PernaH Road. Jackson, MI 49201 e (517) 788-1636 June 29, 1989 )

Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT -

RESPONSE TO NRC BULLETIN 88 STATUS OF COMMITMENTS NRC Bulletin 88-04, Potential Safety-Related Pump Loss, dated May 5, 1988 identified NRC conce ns regarding minimum flow requirements for selected systems configurations. A Consumers Power Company letter dated July 7, 1988 responded to the Bulletin and included several long term actions to insure that all minimum flow concerns were addressed. NRC letter dated November 18, 1988~noted that our requirement for responding to Bulletin 88-04 was consider- f ed fulfilled based on the long term resoltition of actions we had identified in onr July 7, 1988 letter. This letter provides the status and results of those .i actions and revises the commitments for future action.  !

Two pumps, the electric and diesel fire pumps, were determined to be potential-ly affected.by the bulletin concerns. As stated in our July 7, 1988 letter,

[t these two fire pumps fulfill dual functions. One function is to provide water l for fire protection. The second function is to provide flew to the core spray

( system. The core spray system consists of two parallel spray headers which

} provide reactor vessel water make-up and core cooling water during the early L stages of a loss of cooling accident.

The concerns of the bulletin are primarily applicable at Big Rock Point during >

routine resting and fire fighting activities at which time minimum flow conditions are most likely to exist. Plant Technical Specifications were reviewed.for guidance relative to system operation and vendor recommendations.

The Big Rock Point Technical Specifications contain usage and flow restric-tions that limit availability of the fire suppression system for routine test and for -fire fighting purposca. Specifically, the fire suppression system can be used for routine purposes without declaring the core spray system inoper-able provided total flow drawn from the systeni is limited to 400 gallons per minute (40% of a single pumps rated capacity) and provided such routine uses J.o not exceed 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> / year. The Plant Technical Specifications further j specify that the fire suppression system can be used for ' fire fighting or for i tests involving only flow through the fire suppression system relief valves without declaring the core spray system inoperable and without a flow and annual = time restriction.

OC06f4-0143-NLO4 8907030281 890629 I I PDR ADOCK 05000155

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Nociar.r Rrgulctory Commission 2 l

/ Big Rock Point Plant Response to NRC Bulletin 88-04 June 29, 1989 These imposed limitations assure that water flow from the fire suppression system for fire suppression or for normal uses and testing have a negligible effect on the availability of the core spray system. Probabilistic risk assessment and analysis have been performed to validate system response to various scenarios and system configurations resulting from a plant transient.

Particular consideration has been given to core spray system operability with single failure criterion in mind. In addition, thermal-hydraulic analysis has been performed assuming various break sizes and valve failures to insure adequate core spray flow is achieved. Recognizing that the fire pumps are used for two purposes, these analyses have assured that the operability and  !

availability of the core spray system is not jeopardized as a result of fire protection usage, testing or other routine uses. The existing technical specifications and system requirements are derived and based upon the ability of the fire pumps to provide rated core spray concurrent with other system demands or analyzed failures.

Not withstanding technical and licensing requirements, periodic testing assures continued operability of the fire pumps. One of these tests is the annual ASME pump testing which verifies that measured flow falls within acceptable limits of the pump curve. Data collected for each pump in 1988 demonstrated that measured flow was equal to or greater than that indicated on the head curve for shut off head conditions out to rated capacity. In addi- )

tion, vibration monitoring required by the ASME pump program and component performance monitoring are also utilized to assess pump performance. Data required by the ASME program has indicated no change or undesirable trend in vibration for either pump. Likewise, the plant performance monitoring program has not identified any vibration concerns with the electric fire pump.

Consumers Power Company, in our July 7,1988 response, committed to contact the pump vendor to obtain their recommendations regarding minimum flow requirements for both pumps. Service representation for these components has been assumed by Dresser Pump Division, Dresser Industries, Inc. This vendor was supplied with relevant pump information and was apprised of the service and testing conditions that the components are routinely subjected. Addition-ally, the vendor was informed of the fact that we have not experienced any loss in pump performance or increase in vibration as indicated by ASME pump testing and plant monitoring activities. Upon review of our submitted data, the vendor extended the following recommendations: 1) A minimum flow of 60% of rated pump capacity is recommended for a stable continuous flow, 2) A minimum flow of 40% of rated pump capacity is recommended for routine testing prac-tices. The vendor addit!onally stated that they did not believe that either pump had experienced any mechanical damage as evidenced by their operating this long without performance or vibration problems. They did state that some erosion of the impeller and wear rings was probchle due to the pump inservice period.

Based on the above, and in light of system requirements mandated by our plant i technical specifications, we have concluded that it is neither appropriate nor necessary to comply with the vendors recommendation. Based on our operating history demonstrating a lack of substantiated performance problems, we feel that operation of the fire pumps outside of their existing operating envelope j is not warranted. Previous analysis and single failure criteria OC0689-0143-NLO4

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s Vdclear Regulatory Commission 3 Big Rock Point Plant Response to NRC Bulletin 88-04 June 29, 1989 considerations preclude modifying the system or ex1 sting procedures to support these vendor recommendations. However, both fire pumps will be scheduled for inspection within the next two refueling outages. Reconditioning of the pumps will be performed as dictated by their material condition as found during the inspection.

We have evaluated our existing surveillance procedures relative to the vendors recommendations and our commitment to either revise the testing process or j propose modifications to satisfy the suggestions. Revising test procedures or i proposing modifications to accommodate the vendor recommendations are deemed inappropriate. We conclude that our probabilistic risk assessments, system analysis, licensing requirements and the continuing satisfactory performance of both fire pumps negate the need for implementing procedure revisions or system modification.

In response to our commitment to determine whether or not a schedule for impeller inspection is necessary, ve have reviewed applicable surveillance test and vibration data to establish a level of performance for both pumps.

The conclusion drawn from our performance data review and discussions with maintenance department personnel was that there has been no indication of degradation in the performance of either pump. An inspection was therefore not scheduled for the 1989 refueling outage. However, we have scheduled both pumps for inspection in following outages. The diesel driven fire pump will be inspected during the 1990 refueling outage while the electric driven fire pump will be inspected during the refueling outage after that.

The issues raised by the NRC Bulletin are recognized by Consumers Power Company. Future inspections will be performed in the interests of satisfying those concerns. However, we have found no data to justify any further immediate action nor is there a demonstrated degradation of pump performance which would justify revising the operating envelope of the fire pumps as r result of the NRC Bulletin or vendors recommendation. In our opinion, these considerations, as well as the influence of previous analysis and licensing limitations, dictate that a future component inspection should be performed and we will continue to monitor for evidence of NRC Bulletin related pump l degradation. l

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Kenneth W Berry Director, Nuclear Licensing CC Administrator, Region III, USNRC  ;

NRC Resident Inspector - Big Rock Point l \

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