ML19210E325

LER 79-053/03L-0:on 791024,total Primary Coolant Oxidants Exceeded 10 Parts Per Million.Caused by off-gassing of Oxidants Due to Reaction of Moisture W/Core Graphite.Power Decreased to Initiate Maint Shutdown

ML19210E325
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/19/1979
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19210E323	List: ML19210E322 ML19210E325
References
LER-79-053-03L, LER-79-53-3L, NUDOCS 7912040335
Download: ML19210E325 (1)

Text

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REPORT DATE: November 1% 1979 _ REPORTABLE OCCURRENCE 79-53 ISSUE O OCCURRENCE DAIE: Octob er 24, 1979 Page 1 of 4 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMEANY OF COLORADO 16805 WELD COUNTY ROAD 191/2 PLATTEVILLE, COLCRADO 80651 REPORT NO. 50-267/ 79-5 3/03-L-0 Final IDENTIFICATON OF OCCURRENCE:

At approximately 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> on October 24, 1979, with average core outlet temperature greater than 1,200*F, total primary coolant oxidants (the sum of water, carbon dioxide, and carbon conoxide) exceeded ten parts per million. This constitutes operation in a degraded mode of LCO 4.2.10 and is reportable per Fort St. Vrain Technical Specification AC 7.5.2(b)2.

EVENT DESCRIPTION:

On October 24, 1979, with total orimary coolant oxidants at less than 10 parts per million reactor power was being increased in preparation for approved fluctu-ation testing. At approximately 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> average core outlet temperature exceeded 1,200*F. The total of primary coolant oxidants at that time was approxi-mately 7.5 parts per million. Following the reactor power increase to approxi-mately 60%, primary coolant oxidants began to follow an upward trend. At approxi-mately 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br />, primary coolant oxidant levels exceeded ten parts per million (reference Figure 1, point 1) . During the period of fluctuation testing, average core outlet temperature remained above 1,200*F and total oxidants continued to increase.

Fluctuation testing was completed at 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br /> on October 25, 1979, and an orderly shutdewn was initiated for plant =sintenance. Core outlet temperature was less than 1,200*F by 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> on October 26, 1979, (reference Figure 1, point 2) and to further LCO 4.2.10 degraded mode operation occurred.

CAUSE DESCRIPTION:

The increase in total oxidants is due in part to off-gassing of carbon =enoxide and carbon dioxide as residual primary coolant moisture reacted with the core graphie.e at increased temperatures.

1A72 246 f

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REPORTABLE OCCURRENCE 79-53 ISSUE O Page 2 of 4 CORRECIIVE ACTION:

Following completion of fluctuation testing at approximately 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br /> on Octo-ber 25,1979, orderly reactor shutdown was initiated. Core outlet temperature was less than 1,200

• F. by approximately 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> on October 26, 1979, and no further degr'aded mode operation was observed.

No further corrective action is anticipated or required.

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FIGURE 1: AVERAGE CORE OUTLET TEMPERATURE VERSUS PRIMARY COOLANT OXIDANTS 1350- 40

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. REPORTABLE OCCURRENCE 79-53 ISSUE O Page 4 of 4 Prepared by: 'r 4-2M Cathy (C[ H1'rsch T Techni'chl Services TechniciXn

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Reviewed by:

7. W. gahm'

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/; su kechnical Services Supervisor Reviewed by:

Frank M. Mathie Operations Manager ,

Approved by: 7}7m _

Don Warembourg /

Manager, Nuclear Production 1472

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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSIUN (7*77 T LICENSEE EVENT REPORT CONTROL BLOCK: l 1

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80 EVENT OESCRIPTION AND PROSABLE CONSEQUENCES h o 2 l At approximatelv 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> on October 24. 1979. with averace core outlet temperature 1 o a j greater than 1,200*F, total primary coolant oxidants exceeded 10 parts per million. l o 4 l This is operation in a degraded mode of LCO 4.2.10 and is reportable per Technical o s l Specification AC 7.5.2(b) 2. No affect on public health and safety. Similar occur- l o e l rences reported in RO's 77-36, 78-12, 78-18, 78-37, 78-39, 79-01, 79-02, 79-24, 79-30,1 oi7 land 79-45. I l

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W graphite. When power was decreased to initiate maintenance shutdown _, no further de- ,

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