05000267/LER-1979-024, Forwards LER 79-024/03L-0

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Forwards LER 79-024/03L-0
ML19253A576
Person / Time
Site: Fort Saint Vrain Xcel Energy icon.png
Issue date: 08/31/1979
From: Warembourg D
PUBLIC SERVICE CO. OF COLORADO
To: Seyfrit K
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19253A577 List:
References
P-79195, NUDOCS 7909100355
Download: ML19253A576 (7)
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LER-1979-024, Forwards LER 79-024/03L-0
Event date:
Report date:
2671979024R00 - NRC Website
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text

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FT public service company o f c cil e n d e

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P. O. Box 361, Platteville, Colorado 80651 i

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August 31, 1979 Fort S t. Vrain Unit No. 1 P-79195 Mr. Karl V. S eyf rit, Director Nuclear Regulatory Cocmission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012 REF: Facility Operacing License No. DPR-34 Docket No. 50-267

Dear Mr. Seyfrit:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/79-24/03-L-0, Final, submitted per the requirem.nts o f Technical Specification AC 7.5.2(b)2.

Also, please find enclosed one copy or the Licensee Event Report for Reportable Occurrence Report No. 50-267/79-24/03-L-0.

Very truly yours, Wwu Don Warembou&

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Manager, Nuclear Production DW/alk cc:

Director, MIPC Y

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._ 't 7909100 3

REPORT DATE:

August 31, 1979 REPORTABLE OCCURRENCE 79-24 ISSUE O OCCURRENCE DATE:

Augus t 4, 19 79 Page 1 of 6 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLAITEVILLE, COLORADO 80651 REPORT NO. 50-267/ 79-24 /03-L-0 Final Ic2NTIFICATION OF OCCURRENCE :

On three occasions during the period from August 4,1979, through Augus t 16, 1979, total primary coolant oxidants (the sum of water, carbon monoxide, and carbon dioxide) exceeded 10 parts per million with core average outlet tem-perature greater than 1,200*F.

This constitutes operation in a degraded mode permitted by LCO 4.2.10 and is reportable per Technical Specification ~ AC 7.5.2(b)2.

EVENT DESCRIPTION

At about 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br /> on August 4,1979, with the reactor operating at approxi-mately 452' power and total pri=ary coolant oxidants at approxicately 11.8 ppm, core average outlet temperature exceeded 1,200*

for the first time since the refueling shutdown (referenc Figure 1, point 1 ).

Following an initial increase, (Figure 1, point 2 ) oxidant levels appeared to be following a decreasing trend antil approximately 1745 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.639725e-4 months <br /> on August 6,1979. Since as

=uch moisture as possible had been removed at existing plant conditions, reac-tor power was increased to approximately 60% to f acilitate additional " drying out" operations. At that time, it was observed that carbon monoxide indica-tions were on the increase.

At 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on August 7,1979, it was observed that primary coolant carbon dioxide levels were also increasing. At this point, it was determined that 4

the "A" helium purification dryer had apparently broken through. Maximum oxi-dant concentration of 51.5 ppm was reached at approximately 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> ich average core outlet temperature of 1,300*F (reference Figure 1, point

).

Operation continued at approximately 65 power and 1,340*F core outlet tem-perature, and primary coolant oxidant levels followed a generally decreasing trend as the increased temperatures allowed the moisture to outgas f rom the graphite in the core.

REPORTABLE OCCURRENCE 79-24 ISSUF 0 Page 2 of 6 EVENT DESCRIPTION (continued) :

Due to a circulator trip on August 11, 1979, t =peratures were decreased to less than 1,200*F (reference Figure 1, point 4 ).

With the subsequent rise in power later that same day, temperatures were again increased to greater than 1,200*F, while oxidant levels continued their decreasing trend. At 1937 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.370285e-4 months <br /> on August 11, 1979, the reactor scrammed, a d temperatues again decreased to less than 1,200*F (reference Figure 1, Point 5

).

Oxidant levels con-tinued to decrease until a subsequent increase in temperature on August 13, 1979, resulted in LCO 4.2.10 limits again being exceeded at approxi=ately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on August 13,1979 (reference Figure 1, point (f) ).

At 0040 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> on August 16, 1979, a circulator trip occurred.

Reactor power and temperature w re decreased to allow recovery of the circulator (reference Figure 1, point 7

).

Following this occurrence, no further degraded mode operation of LCO 4.2.10 occurred.

CAUSE

DESCRIPTION :

It is assumed that the continued level of oxidants in the primary coolant follcwing regeneration of the purification train was a result of off-gassing due to a previous buf fer helium dryer bypass which resulted in water ingress to the cote.

As temperatures increase, the water reacts with the graphite in the core to form carbon monoxide and carbon dioxide. During the period covered by this report there were no significant changes in the moisture concentrations ob-served in the primary coolant, so the increased oxidant levels are attributed to the reaction b-. ween the water and graphite as a result of efforts to dry out the core following an extended refueling shutdown and the previously men-tioned dryer bypass.

CO RRECTIVE ACTION:

4 "B" purification train was placed in service in an attempt to keep the total primary coolant oxidant levels from increasing, and the "A" purification train which had broken through was regenerated.

Dr"ing out operations were continued with consideration to the limits allowed per LCO 4.2.10.

Decreases in te=perature due to periodic circulator trips and reactor scrams precluded any necessity for planned temperature decreases.

REPORTABLE OCCURRENCE 79-24 ISSUE O Page 3 of 6 CORRECTIVE ACTION (continued) :

Following the return to a core average outlet te=perature greater than 1,200*F on Augus t 16, 1979, no further degraded mode operation per LCO 4.2.10 was ob-served.

No further corrective action is anticipated or required.

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ISSUE 0 Page 4 of 6 E

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    = 4 3 0000 0000 0000 0000 0000 0000 0000 0000 8/10 3/11 S/12 S/13 8/14 3/15 8/16 8/17 DATE/TISE CORE AVERAGE OLTLET TEMPERATCPI AND TOTAL PRIMARY C00LAhi OXIDA'ITS REPORTABLE OCCURRENCE 79-24 ISSUE 0 Page 6 of 6 Prepared by: M, n d Cathy y Collard Technical Services Technician Reviewed by: '/ 'J. W. Gahm Technical Services Supervisor Reviewed by: Frank M. Mathie Operations Manager Approved by: 775u,_ Ls_ Don Ware = bourg g Manager, Nuclear Production 4 (_ , v
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