ML20213F313

Backfit Regulatory Analysis

ML20213F313
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	11/07/1986
From:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20213F307	List: IR 05000155/1986004 ML20213F313
References
NUDOCS 8611140149
Download: ML20213F313 (5)

Text

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t BIG ROCK POINT BACKFIT REGULATORY ANALYSIS OBJECTIVE The objective of this backfit is to provide a reliable and maintainable redundant emergency core cooling system core spray function.

BACKFIT DESCRIPTION The diesel engine for the diesel engine driven fire pump (DFP) will be replaced. The DFP is redundant to the electric motor driven fire pump (EFP) in providing cooling supply to the core spray system.

CORE SPRAY SYSTEM DESCRIPTION Big Rock Point was designed and constructed in an era when multiple systems and trains of systems designed to inject water into the vessel under all plant conditions were not the norm. Big Rock Point does not have available dedicated high and low pressure core spray / safety injection systems, reactor core isolation cooling systems, or residual heat removal systems with multiple configurations representative of newer plant designs. The DFP discharges at rated 1000 gpm and 110 psi no-head discharge pressure into a circular piping header surrounding the containment sphere for fire water supply to hydrants and sprinklers, fulfilling the fire protection purpose of the system. From the circular header, piping enters the containment sphere via two routes to provide the plant's only source of post LOCA reactor water level control, core spray, and containment pressure control, containment spray (See Figure). Other lines from the header provide (1) water to a heat exchanger used in conjunction with post-incident pumps that remove water from the containment sphere following a LOCA and return it to the reactor vessel, and (2) water to regular core spray lines provided as a backup through post-incident system piping.

The significance of the DFP is emphasized should the EFP be rendered unavailable. The EFP is powered by Bus 2B supplied by the Emergency Diesel Generator (EDG) on loss of station power. The DFP is the only pump available to provide core cooling under plant electrical single failure conditions.

Also, during alternate safe shutdown under fire conditions, Bus 2B is disconnected from the EDG and the EDG is realigned to power components necessary for alternate shutdown. In that configuration, the DFP is the only available source of fire water.

BACKGROUND During the last quarter of 1985 the DFP began showing evidence of erratic behavior during regular weekly surveillance testing. Operators familiar with the operating characteristics of the engine described its behavior as

" sluggish", particularly during engine start, and noted variable engine h

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i speed while operating. In January 1986, the DFP failed to meet acceptance criteria for starting time, 20.4 seconds from first crank to full dead head pressure. Corrective action involving cleaning of the injection pump delivery valve and transfer pump discharge relief valve resulted in satisfactory start times in the seven second range typical of the engine's long term performance history.

During February 1986, erratic behavior and extended start times again became evident during weekly surveillance performance and, on February 4, the DFP was declared inoperable based on excessively long start times. Big Rock Point Technical Specification 11.3.1.4 requires both the DFP and EFP to be operable during power operation and the declaration of DFP inoperability placed the plant in a Limiting Condition for Operation (LCO) requiring initiation of shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The licensee avoided shutdown not by restoring the DFP to an operational condition representative of its previous long history of successful performance, but rather by implementing a change to the surveillance procedure that increased the allowable start time by 25 seconds.

The engineering justification for the increase was contained in a revised Loss of Coolant Accident (LOCA) analysis approved by NRR and incorporated into Amendment No. 44 to the Units Operating License issued June 9, 1981.

Due to the age of the engine, maintenance was hampered by unavailability of replacement parts, diagnostic instruments, and repair expertise. The engine was adjusted, cleaned, and tightened to produce satisfactory start time and pump capacity performance during testing on February 15.

With the exception of difficulty with governor adjustments which placed the engine speed outside specifications during May 1986, the performance analysis of the DFP during recent surveillances indicates it is likely to fulfill its safety function until the next scheduled refueling outage when the engine is scheduled for replacement.

REGULATORY CONCERNS Given the significance of the DFP's role in keeping the core covered, the licensee was advised of the following concerns by the Senior Resident Inspector:

1) The root cause of the erratic behavior of the DFP, including long start times and oscillating engine speed, has never been positively identified and corrected.

, 2) Increasing the allowable start time by 25 seconds maintains the licensee within the limits of the safety analysis, but fails to address the engine's reliability which is suspect.

3) The advanced age of this piece of original plant equipment makes parts l procurement difficult, degrading the licensee's ability to maintain the engine in a condition of operational readiness.

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4) Repair attempts in 1985 and 1986 pointed out the difficulty in obtaining i

vendor assistance and diagnostic instruments appropriate for an engine of this vintage, further degrading the licensee's ability to maintain the engine.

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5) Recommendations and detenninations to replace the driver which were originally approved by Consumers Power Company and were then reversed due to financial considerations should be reevaluated.

The licensee was informed by the Senior Resident Inspector that, based on the safety significance of the DFP, the recommendations of the plant engineering and maintenance staffs to replace the engine due to further anticipated problems with DFP reliability should be met without regard to financial priorities. The NRR Project Manager concurred with the inspector's concerns during a telephone review of the safety considerations involved. The licensee subsequently informed the inspector of their commitments to replace the engine during the next refueling outage. This commitment is documented in Inspection Report No. 50-155/86004(DRP), Paragraph 2.b.

COST / BENEFIT ANALYSIS The driver replacement is a like for like replacement that does not constitute a major plant design change or system modification. No changes in the operational complexity of the reactor are expected as this project merely involves replacement of a component with a newer model of the same general type and description. The licensee has further determined that the replacement engine chosen is a common model in wide usage with parts and vendor expertise readily available. The DFP modification consists of replacement of the existing driver with a six cylinder,123 horsepower Caterpillar diesel engine. The pump assembly is separate from the driver and, while it will be overhauled, it will not be replaced on the basis of a satisfactory history of pump capacity tests.

Replacement cost for the diesel engine is estimated by the licensee at

$12,000. Total cost of the project is estimated at $60,000. Modifications to the engine foundation and labor costs compromise the bulk of the expense.

Continued cost of the DFP replacement will be lower than maintenance of the existing engine due to decreased corrective maintenance and increased parts availability. The replacement and continued cost is offset by the incalculable cost of the loss of the only componei t capable of providing core cooling on a total loss of on-site and off-site electrical power. The loss due to aged equipment of this core cooling system under that postulated single failure condition could result in core damage and would constitute a threat to public health and safety.

RADIOLOGICAL EXPOSURE OF FACILITY EMPLOYEES AS A RESULT OF THIS MODIFICATION There is no radiological exposure associated with this modification. The locations and equipment included are not in radiation or contamination areas.

ESTIMATED RESOURCE BURDEN ON NRC Inspector coverage for replacement of the DFP driver would be provided by the Big Rock Point Senior Resident Inspector during normal inspection activities.

This will occur during the next refueling outage scheduled for January 1987.

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1 Some review of engine procurement activities has already been performed by the inspector. Remaining inspection of actual installation would involve an estimated twenty hours of inspection effort under I&E Inspection Procedure No.

37700, " Design Changes and Modifications".

IMPACT OF DFP REPLACEMENT ON OTHER SAFETY RELATED ACTIVITIES:

Because the licensee's February 1986 commitment to replace the DFP came well in advance of the outage during a period the outage work list was being defined, it is not possible to determine what work, if any, will not be performed because of financial and manpower commitments for the DFP replacement. The project was not ranked by the Technical Review Group for relative benefit and priority determination. The relatively small cost and small scope of the replacement would not, however, be expected to impact significantly on the refueling outage.

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