ML20203N290

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Discusses Current Plant DHR Capability.Corrections Include Exam of Affected Pipes,Sealing of Leaks,Seismic Analysis of Casing Drain Line,Review of Pumps for Similar Configuration Problems & Development of Mod Package
ML20203N290
Person / Time
Site: Rancho Seco
Issue date: 09/09/1986
From: Julie Ward
SACRAMENTO MUNICIPAL UTILITY DISTRICT
To: Martin J
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
JEW-86-412, NUDOCS 8609230288
Download: ML20203N290 (2)


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l.s Osuun SACRAMENTO MUMCIPAL UTIUTY DISTRICT C 62o1 S Street. P.O. Box 15830. Sacramento CA 95852-1830.(916) 452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA JEW 86-412 September 9.1%6 N

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J B MARTIN REGIONAL ADMINISTRATOR W

REGION YOFFICE0FINSPECTION ANDENTORCEMENT h

U S NUCLEAR REGULATORY COMMISSION 1450 MARIA LANE. SUITE 210 WALNUTCREEK.CA 945%

DOCKETNO.50-312 LICENSE NO. DPR-54 DESCRIPTION OF CURRENT R ANCHO SECO DECAY HEAT REMOVAL CAPABILITY In order to clarify recent events relative to the Decay Heat removal capability at Rancho Seco, the District hereby provides a succiaet description of: (1) the current Decay Heat removal capability at Rancho Seco: (2) how the Decay Heat System Trains became degraded:(3) the actions that were and will be taken to correct the identified degradation. and: (4) the schedule for formally declaring the Decay Heat System Trains operable pursuant to Technical Specification 1.3 r

There are a variety of methods available to remove the minimal amount of core decay heat at Rancho Seco. These systems include two reactor coolant loops; the two 100% decay heat system tr. ins: reactor coolant injection by the two remaining make-up pumps, and: gravity draining of the Borated Water Storage Tank to the core.

Of the methods described above, the two decay heat trains are functional, though not currently

" Operable" as defined in the Technical Specifications. Also. the make-up pump injection method and draining the Barated Water Storage Tank to the core method are available for core decay heat removal.

The degraded condition of the decay heat system was described in Licensee Event Report (LER) 86-02. That LER described the one-inch diameter decay heat pump casing drain lines which have experienced high velocity erosion as a result of undesirable recirculation flow. LER 86-14 reported a leak which was attributed to the same erosion methodology, immediate corrective actions for the decay heat system were:(1) radiographic examination of t

the affected pipe:(2) sealing the discovered leaks:(3) seismically analyzing the repaired casing drain line:(4) performing of a review of other pumps in the plant to determine if there were others with similar configuration problems, and: (5) developing a modification package which l

corrects the piping configuration. These activities were done consistent with prudent engineerir.g practice in the power industry, and within the context of the "immediate corrective action" requirement of Technica1 Specification 3.1.1.5. This immediate action was considered to be an interim response, until at least one Reactor Ccolant System (RCS) loop could j

be made cperable for decay heat removal.

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J. B. MARTIN September 9.1956 The ultimate corrective action will be to implement the design modification package (ECN R-0495) to reconfigure the decay heat pump casing drain lines. Implementation of the design modification requires the draining of the affected decay heat loop. It is considered prudent to have at least one RCS loop available for decay heat removal prior to initiating the design modification package.

The current schedule shows the aforementioned prerequisite vill be achieved by late-October 1956. which will then permit the removal of a single decay heat train from service to implement the system modifications. Immediately following the completion of the modifications on one decay heat train. the companion train willbe removed from service for implementation of the system modifications.

Both trains of the Decay Heat System are currently scheduled to be operable by December 29.

1956 If there are any questions concerning this issue please contactMr.Ron W. Colombo at the Rancho Seco Nuclear Generating Station.

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J0lIN E WARD DEPUTY GENERAL MANAGER.

NUCLEAR Attachment cc: Region V(2)

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