ML19296A176

LER 78-037/03X-1 on 781209:core Average Outlet Temp Greater than 1,200 F;Primary Coolant Accidents Greater than 10.0 Parts Per Million by Vol.Updates Rept to Correct B Recirculator to B Recovery Compressor.

ML19296A176
Person / Time
Site:	Fort Saint Vrain
Issue date:	02/01/1979
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19296A175	List: ML19296A174 ML19296A176
References
LER-78-037-03X, LER-78-37-3X, NUDOCS 7902090332
Download: ML19296A176 (1)

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REPORT LATE: Feb ruary 1, 1979 REPORTABLE OCCURRENCE 78-37 ISSUE 1 OCCURRENCE DATE: December 9,19 78 Page 1 of 3 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/ 78-37/0 3-X-1 Final Supplement - Previous Report Date 1/8/79 IDENTIFICATION OF OCCURRENCE:

On three separate occasions from December 9,1978, to December 12, 1978, the core average outlet temperature was greater than or equal to 1,200 F while total primary coolant oxidants were greater than 10.0 parts per million by volume (10.0 vpm) .

This constitutes operation under a degraded mode permitted by LC0 4.2.10, and is reportable per Fo rt S t. Vrain Technical Specification AC 7.5.2(b)2.

EVENT DES CRIPTION:

From 2221 hours0.0257 days <br />0.617 hours <br />0.00367 weeks <br />8.450905e-4 months <br /> to 2225 hours0.0258 days <br />0.618 hours <br />0.00368 weeks <br />8.466125e-4 months <br /> on December 9,1978, the core average outlet temperature was 1,200*F while total primary coolant oxidants were 10.8 vpm.

From about 0000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> to 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br /> on December 10, 1978, the core average outle t temperature was about 1,201"F while total primary coolant oxidants were 10.6 vpm. Both of these events occurred while the reactor was critical at about 40% power during moisture removal operations.

From about 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> on December 11, 1978, to 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on December 12, 1978, operations in a degraded mode of LCO 4.2.10 again occurred as a result of a reactor power increase following recovery from a purification system upset.

CAUSE DESCRIPTION:

On November 29, 1978, a "B" Helium Recovery Compressor service water leak caused a buffer helium upset, which resulted in moisture being introduced into the primary coolant via the upper journal bearing seals of the helium circula to rs . At that time the reactor was shutdown.

Repairs were completed on "B" Helium Recovery Compressor, and the reactor was taken critical on December 3,1978, and operated at up to 12% power to remove as much moisture as possible from the primary coolant for those plant co nditions .

REPORTABLE OCCURRENCE 78-37 ISSUE 1 Page 2 of 3 CAUSE DESCRIPTION (continued) :

On December 9,1978, reactor power was increased to about 40% with the inten-tion of maintaining the core outlet temperature at about 1,190*F to aid in removing residual moisture f rom the PCRV insulation. The total oxidant con-centration decreased as anticipated for the new plant conditions. However, for about four minutes on December 9,1978, and 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on December 10, 1978, the core outlet temperature was inadvertently allowed to equal or ex-ceed 1,200*F while the oxidant concentration was greater than 10.0 vpm.

At about 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br /> on December 10, 1978, the on-service purification train Low Temperature Adsorber (LTA) began to heat up. No rmally the LTA is cooled by liquid nitrogen to remove carbon monoxide (CO) and other gaseous impuri-ties. Apparently a gaseous nitrogen " bubble" formed and decrcased the liquid nitrogen cooling flow to the LIA. This allowed the LTA to release the carbon monoxide it had collected. The carbon monoxide concentration rapidly increased to about 77 vpm. The water and carbon dioxide concentrations at the time of the event were 1.2 vpm and 1.6 vpm, respectively, and the core average outlet temperature was less than 1,200*F.

Shortly af ter the LIA heated up, the liquid nitrogen storage dewar pressure was increased to re-establish liquid nitrogen cooling flow. The carbon mon-oxide concentration immediately began to decrease at a rate of about four vpm/ hour. This decrease continued throughout the morning of December 11, 1978, and no further problems with the LTA were experienced. For these rea-sons it was decided to increase reactor power to about 40%. Consequently, at 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> on December 11, 1978, the core average outlet temperature ex-ceeded 1,200* F. Operations in a degraded mode of LCO 4.2.10 continued until 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on December 12, 1978, when the oxidant concentration decreased below 10.0 vpm.

CORREC flVE ACTION:

The corrective action for the inadvertent four minute event of December 9, 1978, and the 1.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> event of December 10, 1978, was to reduce the core average outlet temperature below 1,200*F. Personnel involved were admonished.

The Low Temperature Adsorber problem was corrected by increasing the liquid ni _rogen dewar p ressure. No further difficulties with formation of a gasecus r.itrogen " bubble" have been experienced to date.

REPORTABLE OCCURRENCE 78-37 ISSUE 1 Page 3 of 3 Prepared by: / 9d z![1 _

Charles H. Fuller Technical Services Technician Reviewed by: [. .

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J./ W. 9dF u 15chnical Services Supervisor Reviewed by: N Frank M. Mathie Operations Manager Approved by: 77EmM Don Warembourg #

Manager, Nuclear Production