05000312/LER-1986-014, Updates Re Correction of Degraded DHR Capability Reported in LERs 86-02 & 86-14.Decay Heat Sys a Pump Casing Drain Lines Replaced Per Design Mod Package ECN R-0498. LER 86-14 Will Be Revised by 861208 to Reflect Mod

Updates Re Correction of Degraded DHR Capability Reported in LERs 86-02 & 86-14.Decay Heat Sys a Pump Casing Drain Lines Replaced Per Design Mod Package ECN R-0498. LER 86-14 Will Be Revised by 861208 to Reflect Mod

ML20215L121
Person / Time
Site:	Rancho Seco
Issue date:	10/15/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
JEW-86-647, NUDOCS 8610280480
Download: ML20215L121 (2)

LER-2086-014, Updates Re Correction of Degraded DHR Capability Reported in LERs 86-02 & 86-14.Decay Heat Sys a Pump Casing Drain Lines Replaced Per Design Mod Package ECN R-0498. LER 86-14 Will Be Revised by 861208 to Reflect Mod

Event date:
Report date:
3122086014R00 - NRC Website

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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT E. 6201 S Street. P.O. Box 1583o. Sacramento CA

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J B MARTIN REGIONAL ADMINISTRATOR REGION V OFFICE OF INSPECTION AND ENFORCEMENT U S NUCLEAR REGULATORY COMMISSION 1450 MARIA LANE, SUITE 210 WALNUT CREEK, CA 94596 DOCKET NO. 50-312 LICENSE NO. DPR-54 UPDATE OF THE RANCHO 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 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. This letter updates the letter from J. E. Ward to J. B. Martin dated September 9,1986 on the same subject.

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 trains; reactor coolant injection by the two remaining make-up pumps, and; gravity draining of the Borated Water Storage Tank to the core.

Both of the decay heat trains are functional, though not currently " Operable" as defined in the Technical Specifications. Also, the make-up pump injection and draining the Borated Water Storage Tank to the core methods are available for core decay heat removal.

ed The degraded condition of the decay heat system was described in Licensee Event M$ Report (LER) 86-02. That LER described the one-inch diameter decay heat pump 580- casing drain lines 'which have experienced high velocity erosion as a result of

-o undesirable recirculation flow. LER 86-14 reported a leak which was attributed to

$$ the same erosion methodology.

O$ Immediate corrective actions for the decay heat s

$8 radiographic examination of the affected pipe; (2)ystem sealing (DHS) were:

the discovered leaks on (1)the 7

o "B" Train; (3) seismically analyzing the temporarily repaired casing drain line; (4) performing a review of other pumps in the plant to determine if there were others 25 with similar configuration problems, and; (5) developing a modification package ma.m which corrects the piping cor. figuration. Sealing activities were done consistent with prudent engineering practice in the power industry, and within the context of the "immediate corrective action" requirement of Technical Specification 3.1.1.5.

This immediate action was considered to be only an interim response. until the DHS loops could be returned to operable status by the installation of the modification to correct the piping configuration problem.

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J. B. MARTIN October 15, 1986 During the week of September 29,1986 the status of the DHS "A" pump casing drain line deteriorated sufficiently to cause a small leak. Recognizing that the DHS "A" pump casing drains appeared to be deteriorating more rapidly than expected, plant management took aggressive steps to begin replacing the drain lines in accordance with the design modification package (ECN R-0498) prior to the scheduled Decay Heat Outages. The action was taken, under the provisions of "immediate corrective action" for Technical Specification 3.1.1.5, to drain Train "A" (from the various suction isolation valves up to the discharge valve that isolates the Train "A" heat exchanger from the reactor coolant system). When DHS "A" was drained, the

. modification commenced and was completed during the week of October 6,1986.

During the period the DHS "A" loop was drained, the functional DHS "B" pump was capable of providing a seismically qualified means of core cooling. Upon completion of ECN R-0498 on DHS "A," and its return to service, the DHS "B" was taken out-of-service and the pump casing drain was replaced.

At the conclusion of the two modifications, Rancho Seco will have two decay heat loops which are " Operable" in accordance with Technical Specifications. LER 86-14 will be revised to reflect this corrective action by December 8,1986.

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

E. WARD DEPUTY GENERAL MANAGER, NUCLEAR Attachment i

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