05000267/LER-1982-014, Forwards LER 82-014/03L-0.Detailed Event Analysis Encl

Forwards LER 82-014/03L-0.Detailed Event Analysis Encl

ML20053A369
Person / Time
Site:	Fort Saint Vrain
Issue date:	05/17/1982
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20053A370	List: 05000267/LER-1982-014, Forwards LER 82-014/03L-0.Detailed Event Analysis Encl 05000267/LER-1982-014-03, /03L-0:between 820417 & 26,only One Complete Pcrv Liner Cooling Loop Was Operable.Caused by Isolating Loop 1 Subheaders to Locate Primary Coolant to Pcrv Liner Cooling Sys Leak.Extent & Cause of Tube Failure Unknown
References
P-82149, NUDOCS 8205260028
Download: ML20053A369 (6)

LER-1982-014, Forwards LER 82-014/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2671982014R00 - NRC Website

text

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r public Servlee Company fOdsudD 16805 Road 19 1/2, Platteville, Colorado 80651-9298 May 17, 1982 Fort St. Vrain Unit No. 1 P-82149

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p il MAY 701982 Mr. John T. Collins, Regional Administrator dN Region IV Nuclear Regulatory Commission 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Reference:

Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Collins:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/82-014, Final, submitted per the requirement. of Technical Specification AC 7.5.2(b)2 and AC 7.5.2(b)4.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/82-014

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Very truly yours, 16W r

Don Warembourg Manager, Nuclear Production DW/cis Enclosure cc: Director, MIPC

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REPORT DATE:

May 17, 1922 REPORTABLE OCCURRENCE 82-014 ISSUE O OCCURRENCE DATE:

Aoril 17, 1982 Page 1 of 5 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE CONPANY OF COLORADO 16805 WELO COUNTY ROAD 19 1/2 PLATTEVILLE, COLORADO 80651-9298 REPORT NO. 50-267/82-014/03-L-0 Final IDENTIFICATICN OF 3

OCCURRENCE:

During the period from April 17, 1982, to April 26, 1982, the reactor was operated at power with only one complete prestressed concrete reactor vessel (PCRV) liner cooling loop operating. This condition occurred on several separate occasions, each of which was terminated within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

These occurrences were necessary to determine a.

primary coolant to liner cooling system leakage path.

Since it was necessary to maintain the reactor at power operation with only one complete operating prestressed concrete reactor vessel liner cooling i

loop, these events constituted degraded modes of LCO 4.2.13.

This 4

occurrence is reportable per AC 7.5.2(b)2 and AC 7.5.2(b)4 of the Technical Specifications.

i EVENT CESCRIPTION:

On April 13, 1982, while commencing a normal reactor and plant startup, an alarm was received indicating high pressure within the prestressed concrete reactor vessel liner cooling system, System 46, Loop 1, subheader outlet plenum.

Upon investigation, the outlet pressure of the liner cooling pumps was higher than normal. A sample for radioisotopes was taken from the System 46, Loop 1 cooling system.

The results indicated the presence of several radioactive isotopes, the longest-lived being Xenon-133, with the probable source being primary coolant.

All concentrations were below the maximum permissible concentration (MPC), and the surge tank was ventea via the gas waste release system to relieve pressure. The System 46, i

Loop 1 was sampled daily with the radioactive contamination reaching a maximum on April 16, 1982.

It was determined that a primary coolant leak into the prestressed concrete reactor vessel liner

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cooling system, Loop 1, existed.

The contamination level was dependent on reactor power, temperature, and pressure conditions. Therefore, it was neces sa ry to keep the reactor at power operation, while isolating, draining, and sampling each subheader of Loop 1 to locate the leak.

Although the cooling capability and flow was never totally interrupted in Loop 1, since the subheaders were removed from the system and drained one at a

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REPORTABLE OCCURRENCE 82-014 ISSUE 0 Page 2 of 5 l

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time, it was concluded that Loop I was not considered a " complete" operating loop per LCO 4.2.13.

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Commencing at 0540 hours0.00625 days <br />0.15 hours <br />8.928571e-4 weeks <br />2.0547e-4 months <br /> on April 17, 1982, the process of isolating one subheader at a time of Loop 1 at various reactor power levels (all below 20%) began.

Upon isolating, draining, and sampling 4

f subheader No. 46237, radioactivity above background was detected.

l This subheader was the only one which showed a significant increase above background contamination. Subheader No. 46237 supplies cooling' water to the reactor core support floor within the prestressed 4

concrete reactor vessel. A su vey of individual tubes within the subheader isolated the leakage to within tube #F4T21. After locating this specific tube, the reactor was manually shutdown in order to facilitate repairs.

A repair and modification procedure was developed to isolate the affected tube from the liner cooling system and allow for future detection of possible primary coolant leakage i

from it.

This occurrence is reportable per AC 7.5.2(b)2 of the Technical Specifications as a degraded mode of LCO 4.2.13 due to having only one complete operating loop of the prestressed concrete reactor.

vessel liner cooling system during reactor power operation.

It is also reportable per AC 7.5.2(b)4 due to the abnormal leakage path through the core support floor liner into the prestressed concrete reactor vessel liner cooling system via a defective cooling tube.

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CAUSE

DESCRIPTION:

The cause of the occurrence was leakage of primary coolant into the j

prestressed concrete reactor vessel liner cooling tube (F4T21) within subheader No. 46237 which supplies cooling water to the core support floor.

Leakage via this path requires that a slight defect must exist in both the support floor liner and the cooling tube.

Since the leakage was dependent on reactor power, temperature,- and pressure, it was necessary to isolate the subheaders during reactor power operation to identify the leak.

CORRECTIVE ACTION:

Each subheader of System 46, Loop 1, was isolated, drained, and 1

sampled to identify the leakage path. Each subheader was returned to 1

normal operation well within the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> grace period of LCO 4.2.13.

At 0602 hours0.00697 days <br />0.167 hours <br />9.953704e-4 weeks <br />2.29061e-4 months <br /> on April 26, 1982, the reactor was manually shutdown, 3'

making LCO 4.2.13 no longer applicable.

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REPORTABLE CCCURRENCE 82-014 ISSUE 0 i

Page 3 of 5 The repair procedure which invnived capping both the inlet and outlet ends of tube FAT 21, was completed at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on May 2, 1982.

The associated modification provided an interspace on each end of the caoped tube and the acility to determine any possible future leakage within these interspacts.

(See Figure 1)

No further corrective action is anticipated or required.

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Figure lo Repair and modification to PCRV liner cool;ng tube /ff4T21 Public Service Conpany of Colorado Change flotice

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REPORTABLE CCCURRENCE 82-014 l

ISSUE O Page 5 of 5 4

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Prepared By:

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Owen J. Q)yton G i

Technical Services Technician i

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