05000267/LER-1981-048, Forwards LER 81-048/03L-0.Detailed Event Analysis Encl

Forwards LER 81-048/03L-0.Detailed Event Analysis Encl

ML20010H872
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/04/1981
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20010H873	List: 05000267/LER-1981-048, Forwards LER 81-048/03L-0.Detailed Event Analysis Encl 05000267/LER-1981-048-03, /03L-0:on 810808 & 25 Loop 1 Prestressed Concrete Reactor Vessel Cooling Water Outlet Temp Exceeded 120 F Due to Failure of Temp Controller.Caused by Cold Solder Joint & Failure of Transistor in Output Circuit,Respectively
References
P-81220, NUDOCS 8109290373
Download: ML20010H872 (4)

LER-1981-048, Forwards LER 81-048/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2671981048R00 - NRC Website

text

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i public servlee company ce Odemde September 4, 1981 v&

Fort St. Vrain Unit No. 1 P-81220 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Commission l

Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 i

Arlitigton, 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. 50-267/81-048, Final, submitted per the requirements of Technical Specification AC 7.5.2(b)2.

Also, please nd enclosed one copy of the Licensee Event Report for Reportable Occurrc:.ce Report No. 50-267/81-048.

Very truly yours, i

W412d'}

Don Warembourg Manager, Nuclear Production DW/cis gP' '

• cy Enclosure

/ f! ?3 S{p[g' cc:

Director, MIPC Ids)

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v 8109290373 810904 PDR ADOCK 05000267 jQ@

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REPORT DATE:

Seotember 4, 1981 REPORTABLE OCCURRENCE 81-048-ISSUE 0 OCCURRENCE DATE:

Aucust 8, 1981 Page 1 of 3 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/2 PLATTEVILLE, COLORACG 80651 REPORT NO. 50-267/31-048/03-L-0 Final IDENTIFICATION OF OCCURRENCE:

On two occasions, Loop 1 prestressed concrete reactor vessel cooling water outlet temperature exceeded 120 cegrees fahrenheit. This is a degraded mode of LCO 4.2.15 and is reportable per Fort St. Vrain Technical Specification Aq 7.5.2(b)2.

EVENT

DESCRIPTION

On August 8, 1981, and-again on August 25, 1981, failure of a temperature controller resulted in Loco 1 prestressed concrete reactor vessel cooling water outlet temperature exceeding the LC0 limit of 120 degrees fahrenheit.

The. prestressed concrete reactor vessel cooling water circuit consists of two identical clcsed loops, each of which can supply 100%

of the flow necessary to maintain prestressed concrete reactor vessel liner temperatures within design limits. Each loop consists of two 100% capacity pumps and two 50% cap. city heat exchangars where the l

tr aperature of liner cooling water is controlled.

The temperature l

control scheme for each loop is as follows: An averaging temperature device receives the inlet and outlet temperatures across the l

prestressed concrete reactor vessel and transmits a signal proportional to this average temperature to a temperature controller.

j L

This controller is then used to control the outlet water temperature l

of the cooling water heat exchangers by throttling-service water out of the heat exchangers.

i i

On August 8, 1981, with the plant ' operating at 69.7% power and l

235 MWe,-

the Loop 1 liner cooling water temoerature. controller

(

failed, resulting in Loop 1 temperature control valve closure and an j

increase in cooling water outlet temperature.

Loop 1 liner cooling water -temperature increased to a maximum of_137 degrees fahrenheit when the Reactor Operator observed the malfunction and switched to a bypass controller to regain temperature control.

The outlet-r I

temperature was restored to acceptable levels within one hour.

The

[

faulty controller.was repaired and returned to service.

I l

t -----

REPORTABLE OCCURRENCE S1-048 ISSUE O Page 2 of 3 On August 25, 1981, with the plant operating at 70P. power and 240 MWe, the same temperature controller again failed. Loop 1 liner cooling water temperature increased to a maximum of 127 degrees fahrenheit before operator action was taken to bypass the controller.

Loop 1 liner cooling water outlet temperature was restored below LCO limits within 15 minutes.

1 In both instances, Loop 2 prestressed concrete reactor vessel cooling circuit was fully operational and was, by itstif, capable of removing the entire prestressed concrete reactor vessel heat load.

CAUSE

DESCRIPTION:

The cause for the first occurrence was found to be a cold solder joint in the temperature contrailer.

The cause for the second occurrence was cue to a failed transistor in the controller output circuit.

CORRECTIVE ACTION:

In the first event, the faulty controller was removed from service and inspected.

The faulty solder jetnt in the controller was repaired and the cratenller was returned to service.

In the second

..ne faulty controller was removed from service and inspected. Tne failed transistor Q-7 in the controller output circuit was replaced and the controller was returned to service.

No further corrective action is anticipated or required.

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.i REPORTABli 9CCURRENCE 81-048 ISSUE O 4

Page 3 of 3 1

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Prepared By:

/d /"

Paul Moore Technical Services Technician 1

Reviewed By:

d'77/dd Silt McBride Technical Services Manager

/

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Reviewed By:

Edwin U.l Hill Station Manager i

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Approved By:

[h" 6'

Don Waremoourg Manager, Nuclear Production 1

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