05000267/LER-1979-045, Forwards LER 79-045/03L-0

Forwards LER 79-045/03L-0

ML19210C428
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/07/1979
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19210C429	List: 05000267/LER-1979-045, Forwards LER 79-045/03L-0 05000267/LER-1979-045-03, /03L-0:on 791008,primary Coolant Oxidants Exceeded 10 Parts Per Million W/Average Core Outlet Temp Greater than 1,200 F.Caused by Residual Moisture Outgasing Due to Dryer Bypass.Load Decreased & No Corrective Action Required
References
P-79266, NUDOCS 7911140240
Download: ML19210C428 (1)

LER-1979-045, Forwards LER 79-045/03L-0

Event date:
Report date:
2671979045R00 - NRC Website

text

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- N' pubne service companylatteville, Colorado oe cenomde 16805 Weld County Road 191/2, 80651

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November 7,1979 Fort St. Vrain Unit No. 1 P-79266 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Cor: mission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012 REF:

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

Dear Mr. Seyfrit:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/79-45/03-L-0, Final, submitted per the requirements of Technical Specification AC 7.5.2(b)2.

Also, please find ' inclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-26 7/79-45/0} L-0.

Very truly yours, bW Don Warembourg Manager, Nuclear roduction DW/alk cc: Director, MIPC

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REPORT DATE:

November 7,1979 REPORTABLE OCCURRENCE 79-45 I

ISSUE O OCCURRENCE DATE:

October 8,1979 Page 1 of 5 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/2 PLAITEVILLE, COLORADO 80651 REPORT No. 50-267/ 79-45/03-L-0 Final IDENTIFICATION OF OCCURRENCE:

On four occasions between October 8,1979, and October 15, 1979, total primary coolant oxidants (the sum of water, carbon monoxide, and carbon dioxide) ex-ceeded 10 parts per million with average core outlet temperature greater than 1,200*F.

These occurrences constitute operation in a degraded mode permitted by LCO 4.2.10, and are reportable per Fort S t. Vrain Technical Specification AC 7.5.2(b)2.

EVENT

DESCRIPTION

At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on October 8,1979, the plant was operating at approximately 38* ther=al power and 120 MWe with an average core outlet temperature less than 1,200*F and total primary coolant oxidants greater than 10 ppm. A de-cision was made to increase reactor power in an attempt to facilitate mois-ture removal and between October 8,1979, and October 15, 1979, degraded mode operations allowed by LCO 4.2.10 occurred on four occasions, as described be-low.

1.

At approximately 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on October 8,1979, average core outlet tem-perature exceeded 1,200*F for the first time sin e return to power on September 15, 1979. Reference Figure 1, point 1 At that time, the total primary coolant oxidant level was approximately 15.7 ppm. As reac-ter power and core outlet temperature were increased to facilitate mois-ture removal, primary coolant oxidant levels increased as moisture was allowed to outgas from the graphite in the core. A maximum primary coolant oxidant level of 24.0 ppm was reached at 0000 hourt on October 9,1979, with corres onding core outlet temperature of 1,320*F (reference Figure 1, point

).

Total oxidant levels began a decreasing trend, with aver-age core let temperature holding steady.

At 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on October 9,1979, it was decided to decrease reactor power to hold average core outlet temperature below 1,200*F until oxidant levels reachedavaluelessthan10 ppm (referenceFigure1, point (3)).

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REPORTABLE OCCURRENCE 79-45 ISSUE O Page 2 of 5 EVENT DESCRIPTION (continued):

2.

Because total oxidants had been less than 10 ppm since approximately 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br /> October 9,1979, reactor power was increased at 1340 hours0.0155 days <br />0.372 hours <br />0.00222 weeks <br />5.0987e-4 months <br /> on Octo-b er 10, 19 79. By 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, average core outlet temperature was greater than 1,200*F.

As core outlet temperature was increased, the small amount of moisture remaining in the core was allowed to react with the graphite, resulting in increased primary coolant oxidant levels. At approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on October 10, 1979, the plant again entered o ration under a degraded mode of LCO 4.2.10 (reference Figure 1, point 4 ).

Following an initial increase due to the rise in core outlet temperature, oxidant levels decreased to less th 10 ppm at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> on October 11, 1979 (reference Figure 1, point

).

3.

A small increase in moisture resulted in total primary coolant oxidants again exceeding 10 ppe at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on October 11, 1979, (reference Figure 1, point (})).

Af ter degraded mode operation of approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, sufficient mois-ture cleanup occurred that total pr mary coolant oxidants dropped below 10 ppm (reference Figure 1, point 7 ).

4 Total primary coolant oxidants remained at less than 10 ppm until 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on October 13, 1979. Beginning at 0000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> on October 13, 1979, carbon monoxide began increasing, and this eventually brought the total of primary coolant oxidants to greater than 10 ppm. Followin short period of degraded mode operation (reference Figure 1, point S

), total oxidants dropped below 10 ppm and no further degraded mode operation was observed.

CAUSE

DESCRIPTION:

'leasons for the LCO 4.2.10 degraded mode operation referenced in this report are as follows:

1.

At approximately 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on October 8,1979, a temporary loss of liquid nitrogen to the low temperature absorber resulted in an increase in total oxidants due primarily to carbon monoxide.

Following a peak at approxi-mately 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> carbon monoxide levels decreased. At 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />, a de-cision was made to increase reactor power to facilitate removal of mois-ture remaining in the core following a dryer bypass due to cross tower leakage on October 5,1979. This increase in temperature resulted in increased oxidant levels.

2.

The degraded mode operation referenced in item 2 of the event description was the result of an increase in core outlet temperature which allowed moisture to react with the core graphite, resulting in increased carbon monoxide and carbon dioxide values.

3.

Degraded mode operation described in item nu=ber 3 was a result of a small increase in moisture level.

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REPORTABLE OCCURRENCE 79-45 I

ISSUE O Page 3 of 5

CAUSE

DESCRIPTION (continued):

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4.

The degraded mode operation noted in item 4 of the event description was due to a small, gradual increase in carbon monoxide. Ne explanation trace-able to plant operation is available for this brief period of degraded mode op era tion.

CORRECTIVE ACTION:

Corrective action for the occurrences noted in this report is as follows:

1.

Reactor power was reduced on October 9,1979, to achieve an average core outlet temperature less than 1,200*F until pri=ary coolant oxidants were brought within the limits of LCO 4.2.10.

2, 3, and 4.

No specific corrective action was taken for the degraded mode operation referenced in itecs 2, 3, and 4.

Sufficient pri=ary coolant cleanup occurred in each case to return pri=ary coolant oxidants to less

. than 10 ppm.

No further corrective action is anticipated or required.

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lu. YUK 1ABLt ULGUKKENCE /9-4)

FIGURE 1 ISSUE O Page 4 ef 5 AVERAGE CORE OUILET TEMPERATURE VERSUS PRIFARY COOLANT OXIDANTS 1350 -

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REPORTABLE OCCURRENCE 79-45 I

ISStE o Page 5 of 5

, b]No>d Prepared by:

o-Cathy C./ Collard Technical Services Technician Reviewed by:

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p a Services Supervisor g

Reviewed by:

Frank M. Mathie Operations Manager Approved by:

Md Manager, Nuclear Product [ ion Don Warembourg

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