ML19263B242

LER 78-037/03L-0 on 781209:on 3 Occasions,The Core Average Outlet Temp Was 1200 F or More While Total Primary Coolant Oxidants Exceeded 10.0 Ppm.Caused Twice by Personnel Error & Once by Mgt Decision After Oxidant Introduction

ML19263B242
Person / Time
Site:	Fort Saint Vrain
Issue date:	01/08/1979
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19263B240	List: ML19263B239 ML19263B242
References
LER-78-037-03L, LER-78-37-3L, NUDOCS 7901150065
Download: ML19263B242 (4)

Text

U. S. NUCLE AR REGULATORY COMMISSION h [ LICENSEE EVENT REPORT CONTROL BLOCK: l t

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EVENT DESCRIPTION AND PROBABLE CONSECUENCES o 2 lOn three separate occasions on December 9,1978, throuch December 12, 1978, the core I a 3 l average outlet temperr.ture was greater than or equal to 1,200 F while total primarv l o 4 lccolant oxidants were greater than 10.0 parts per million by volume. This constitutes I o s l operation in a degrz ded mode of LCO 4.2.10, and is reportable per Fort St. Vrain Tech-l 0 e lnical Specification AC 7.5.2(b)2. I

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. o l A four minute event on December 9, 1978. and a 1. 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> event on December 10, 1978,  !

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4 REPORT DATE: January 8, 1979 REPORTABLE OCCURRENCE 78-37 ISSUE O OCCURRENCE DATE: December 9,19 78 Page 1 of 3

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FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-26 7/ 78-37/03-L-0 Final IDENTIFICATION OF O CCURRENCE :

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 LCO 4.2.10, and is reportable per Fort 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 outlet temperature was about 1,20l*F while total primary coolant oxidante were 10.6 vpm. Both of these events occurred while the reactor was critical at about 40% power during mois ture 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 DES CRIPTION:

On November 29, 1978, a "B" recirculator service water leak caused a buf fer helium upset, which resulted in moisture being introduced into the primary coolant via the upper journal bearing seals of the helium circulators. At that time the reactor was shutdown.

Repairs were completed on "B" recirculator, and the reactor was taken criti-cal on December 3,1978, and operated at up to 13% power to remove as much moisture as possible from the primary coolant for those plant conditions.

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REPORTABLE OCCURRENCE 78-37 ISS UE O Page 2 of 3

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CAUS E DES CRIPTION (continue d) :

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 from the PCRV insulation. The total oxidant con-centration decreased as anticipated for the neu 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. Normally the LTA is cooled by liquid nitrogen to remove carbon monoxide (CO) and other gas eous impuri-ti es . Apparently a gaseous nitrogen " bubble" formed and decreased 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 vp.', respectively, and the core average outlet temperature was less than 1,200*F.

Shortly af ter the LTA heated up, the liquid nitrogen storage dewar pressure was increased to re-establish liquid nitrogen cooling flow. The carbon monoxide concentration immediately began to decrease at a rate of about four vpm/ hour.

This decrease continued throughout the morning of December 11,19 78, and no further problems with the LTA were experienced. For these reasons it was decided to increase reactor power to about 507;. Censequently, 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 temperatura exceeded 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.

CORRECTIVE ACTION:

The corrective action for the inadvertent four minute event of December 9, 19 78, 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 cere average outlet temperature below 1,200 F. Personnel involved were admonished.

The Low Temperature Adsorber problem was corrected by increasing the liquid nitrogen dewar pressure. No further difficulties with formation o f a gaseous nitrogen " bubble" have been experienced to date.

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J REPORTABLE OCCURRENCE 78-37 ISSUE O Page 3 of 3

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Prepared by: ,9^

Charles H. Fuller Technical Services Technician

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Reviewed by: (. . // 4t.

,J,. W . Gahm

' Technical Services Supervisor Reviewed by: [ D'M Frank M. Ma thie Operations Manager Approved by: MM 4, Don Warenbourg /

bbnager, Nuclear Production