Text

Forwards LER 80-011/03L-0
	ML19309C366
Person / Time
Site:	Fort Saint Vrain
Issue date:	04/02/1980
From:	Warembourg D; PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19309C367	List: ML19309C366; ML19309C374;
References
	P-80069, NUDOCS 8004080503
	Download: ML19309C366 (9)
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, 16805 Weld County Road 191/2, Platteville, Colorado 80651 April 2,1980 Fort St. Vrain Unit No. 1 P-80069 Mr. Karl V. Sey f rit, Director Nuclear Regulatory Comission Region IV Of fice of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012

Reference:

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/

80-11, Final, submitted per the requirements of Technical Specification AC 7.5.2(b)2.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/80-11.

Very truly yours, fRA.t Don Warembourg L,

Manager, Nuclear

/

Production DW/cis Enclosure cc: Director, MIPC poo) s

///

800408050 ,

REPORT DATE: April 2, 1980 REPORTABLE OCCURRENCE 80-11 ISSUE O OCCURRENCE DATE: March 6, 1980 Page 1 of 8 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD. COUNTY ROAD 191/2 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/80-11/03-L-0 Final IDENTIFICATION OF OCCURRENCE:

On March 6,1980, at 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months , the reactor dewpoint limits of LCO 4.2.11, Figure 4.2.11-1 were exceeded.

During the period from March 6,1980, to March 21, 1980,- operation in a degraded mode of LCO 4.2.10 occurred on three separate occasions.

These events are reportable per Fort St. Vrain Technical Specification AC 7.5.2(b)2.

EVENT DESCRIPTION: '

At 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months on March 6,1980, reactor dewpoint limits of LCO 4.2.11, Figure 4.2.11-1 were exceeded.

During the period f rom March 6,1980, through March 21, 1980, operation with total primary coolant oxidants in excess of 10 parts per million and core outlet temperature greater than 1200*F (degraded mode of LCO 4.2.10) occurred on three occasions.

Following are descriptions of these occurrences:

Even t #1 (LCO 4.2.11) on March 6,1980, with the plant operating at approximately 35 thermal power and 109 MW electrical, the reactor dewpoint limits of LCO 4.2.11, Figure 4.2.11-1 were exceeded. Primary coolant moisture log readings at 1200 hours0.0139 days 0.333 hours 0.00198 weeks 4.566e-4 months indicated an average core outlet temperature of 1108*F. At that time, reactor dewpoint as corrected from the ME-9307 reading was -16*F, which is within the " limited acceptable" area of Figure 4.2.11-1.

During the following two hours, core outlet temperature increased to 1182*F.

At the 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months primary coolant moisture log reading, the reactor dewpoint was -16'F, which is outside the Figure 4.2.11-1 limit of -18*F. .Although no increase in dewpoint or other indication of a coisture ingress was evident, the temperature increase was sufficient to result in the limits of the LCO being exceeded.

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REPORTABLE OCCURRENCE 80-11 ISSUE O Page 2 of 8 EVENT DESCRIPTION : (Cont' d)

Event #1 (LCO 4.2.11) (Cont' d)

From 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months to 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months , core outlet temperature decreased to 1162*F.

Reactor dewpoint at the 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months primary coolant moisture log reading was -22*F, which is within the acceptable area of the LCO.

Event #2 (LCO 4.2.10)

At approximately 1625 hours0.0188 days 0.451 hours 0.00269 weeks 6.183125e-4 months on March 6,1980, with the plant operating at approximately 35% thermal power and 97 MWe, average core outlet temperature exceeded 1200*F. At this time, the total of pri=ary coolant oxidants (sum of water, carbon monoxide, and carbon dioxide) was approximately 16.2 parts per million. This constitutes operation in a degraded mode of LCO 4.2.10.

The first significant reactor power operation following region constraint device installation occurred in late February and early March,1980. Power was gradually increased, and the turbine generator was placed on line on March 5, 1980. Because of the problems experienced with the helium dryer during the shutdown, elevated moisture and oxidant levels were experienced, and the plant was being operated with average core outlet temperature less than 1200*F to assure compliance with LCO 4.2.10 during primary coolant cleanup.

At 1625 hours0.0188 days 0.451 hours 0.00269 weeks 6.183125e-4 months on March 6,1980, turbine generator load was being adjusted to facilitate surveillance testing. Increased turbine generator load resulted in a slight reactor power increase to follow this demand, along with a corresponding slight increase in average core outlet temperature to greater than - 1200*F. Because LCO 4.2.10 compliance was being so closely monitored, immediate steps were taken to decrease reactor power to a point where core outlet temperature was less than 1200*F. By 1634 hours0.0189 days 0.454 hours 0.0027 weeks 6.21737e-4 months on March 6,1980, nine minutes af ter reactor power increase, core outlet temp-erature had been reduced to less than 1200*F, and no further operation in LCO 4.2.10 degraded mode was observed.

Event #3 (LCO 4.2.10)

On March 9,1980, following several days of operation at less than 1200*F.

core outlet temperature, the total primary coolant oxidant level had dropped below 10 parts per million. At that time, reactor power _ was increased to f acilitate increased electrical generation. As core outlet temperature exceeded 1200*F at 2200 hours0.0255 days 0.611 hours 0.00364 weeks 8.371e-4 months with the plant at 38% thermal power and 112 MR -

electrical, the total primary coolant oxidants increased to a level above 10 parts per million.

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REPORTABLE OCCURRENCE 80-11 ISSUE 0 I Page 3 of 8 a

EVENT .

DESCRIPTION: (Cont' d)

Event #3 (LCO 4.2.10) (Cont'd)

Refer to Figure 1. Operation in a degraded mode of LCO 2.10 commenced at appt .l.mately 2245 hours0.026 days 0.624 hours 0.00371 weeks 8.542225e-4 months on March 9,1980 (see point ). Total p rimary c.'lant oxidants continued to increase during th nerease in reactor .~ver. The maxim oxidant concentration occurred at 0800 hours0.00926 days 0.222 hours 0.00132 weeks 3.044e-4 months on March 10, 1980, (point 2 ) at a core outlet temperature of 1313*F.

At that time, the total of primary coolant oxidants was 57.4 parts per million (37.0 ppm carbon monoxide,17.4 ppm carbon dioxide, and 3.0 ppm wate r) .

Total oxidant levels appeared to have stabilized and begun a slight decreasing trend following the peak at' 0800 hours0.00926 days 0.222 hours 0.00132 weeks 3.044e-4 months . At 1330 hours0.0154 days 0.369 hours 0.0022 weeks 5.06065e-4 months on March 10, 1980, a decrease in reactor power reduced core outlet temperature to less than 12 00

F, hus ending the-period of operation in degraded mode of LCO 4.2.10 (point 3 ).

Event #4 (LCO 4.2.10)

On March 17,1980, at 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months , with the plant operating at- 42% thermal I

power and 133 !M electric, average core outlet temperature was 1277'F.

Total primary coolant oxidant concentration at the. time was 11.1 parts -

per million, which constitutes operation in a degraded mode of LCO 4.2.10.

Reactor power level had been gradually increased during a return to .oper-ation af ter a reactor scram on March 11, 1980. Core outlet temperature had been held to less than 1200*F. At the 1200 hours0.0139 days 0.333 hours 0.00198 weeks 4.566e-4 months primary coolant >

moisture log reading on March 17, 1980, total primary coolant oxidant concentration was less than 10 parts per million. A decision was made to increase reactor power to facilitate increased electrical generation and primary coolant cleanup. At 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months , the sum of carbon monoxide, carbon dioxide, and water was greater than 10 parts- per million, and average core outlet temperature was 1277*F.

Refer to Figure 2. Point 01 indicaces the star = of de8r ded mede oPer-ation. Primary ' coolant oxidant levels followed a generally increasing E,

trend as higher core outlet temperatures resulted in'an increase of ozd-dant off-gassing from the core graphite. A peak oxi at value of 41.0 ppm vas reached at 0000 hours0 days 0 hours 0 weeks 0 months on March 18,1980 (point ).

By March 18, 1980,- reactor power had been stabilized at approximately--

67%, and core outlet temperatures were no longer-increasing significantly. ,

- Primary coolant oxidants began'a generally decreasing trend 'as drying

out operations resulted in smaller amounts of oxidant off-gassing.

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REPORTABLE OCCURRENCE 80-11 ISSUE O Page 4 of 8 EVENT DESCRIPTION: (Cont'd)

Event #4 (LCO 4.2.10) (Con t' d)

Total primary coolant oxidants had not yet dropped below 10 parts per million when a reactor scram occurred at approximately 1445 hours0.0167 days 0.401 hours 0.00239 weeks 5.498225e-4 months on March 21,1980. At t at time, average core outlet temperature dropped below 1200*F (point 3 ), and no further operation in a degraded mode of LCO 4.2.10 was observed.

CAUSE DESCRIPTION:

For event number 1, an increase in core outlet temperature resulted in the limits of LCO 4.2.11, Figure 4.2.11-1 being exceeded. Reactor dew-point levels had been at the same value or slightly lower for some time prior to the event, and primary coolant moisture concentration was decreasing.

However, the increase in core outlet temperature (even though the reactor dewpoint remained essentially unchanged) resulted in the limits of LCO 4.2.11, Figure 4.2.11-1 being exceeded.

High primary coolant oxidant levels observed during events 2, 3, and 4 are attributable to problems experienced with the buffer helium system and corresponding high moisture in the primary coolant during a recent extended plant shutdown, as well as an unexplained increase in primary coolant moisture in late December,1979, which is probably attributable to a previous helium circulator upset which occurred early in December.

Although no dewpoint limits of LC0 4.2.11 were exceeded during the above-mentioned occurrences, increased core outlet temperatures at higher power levels resulted in off-gassing of. carbon monoxide and carbon dioxide, and increased primary coolant oxidant concentrations.

It should be noted that internal maintenance for replacement of a helium circulator was performed during the recent extended shutdown. At any time such maintenance is performed, the possibility exists that air ingress will contaminate the primary coolant system to the extent that subsequent startups will result in exceeding LCO 4.2.10 limits.

CORRECTIVE ACTION:

Event #1 (LCO 4.2.11)

A decrease in core outlet temperature resulted in the reactor dewpoint being within the limits of LCO 4.2.11, Figure 4.2.11-1. No further oper-ation outside the limits of Figure 4.2.11-1 was observed.

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REPORTABLE OCCURRENCE 80-11 ISSUE 0 Page 5 of 8 CORRECTIVE ACTION: (Con t' d)

Event #2 (LCO 4.2.10)

- When core outlet temperature exceeded 1200*F, immediate steps were taken to lower reactor power to reduce the temperature to less than 1200*F, thus ending the March 6,1980, operation in degraded mode of LCO 4.2.10.

Event #3 (LCO 4.2.10)

Power was reduced, which decreased average core outlet temperature to less than 1200*F, and operation in a degraded mode of LCO 4.2.10 terminated at approximately 1330 hours0.0154 days 0.369 hours 0.0022 weeks 5.06065e-4 months on March 10, 1980.

Event #4 (LCO 4.2.10)

A reactor scram at approximately 1445 hours0.0167 days 0.401 hours 0.00239 weeks 5.498225e-4 months on March 21, 1980, resulted in a decrease in core outlet temperature to less than-1200*F. At core outlet temperature less than 1200*F, LCO 4.2.10 is not applicable.

! No further corrective action is anticipated or required.

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REPORTABLE OCCURRENCE 80-11 ISSUE O Page 6 of 8 1350 __ ._

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, REPORTABI.E OCCURRENCE 80-11 ISSUE O Page 8 of 8

/

Prepared By: ( <*: C ;- , d : : c Cathy C. Ifirsch Technical Services Technician Reviewed By: 2 @

ahm j J. W.(ical Services Supervisor Techn I-Revic?ad By: '3' h Trr.r.h M. Mathie Operations Manager i

Approved By: $ 79'$e.<w_/b.-1 Don Warembourg /

Manager, Nuclear Production w -%

ML19309C366

Text

Reference:

Dear Mr. Seyfrit:

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