ML20085L652
| ML20085L652 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/14/1975 |
| From: | Brey H PUBLIC SERVICE CO. OF COLORADO |
| To: | Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| RO-50-267-75-4, NUDOCS 8311020218 | |
| Download: ML20085L652 (4) | |
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Q public service company of cdondo P. O. Box 361, Platteville, Colorado 80651 March 14, 1975 g
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Mr. E. Morris Howard, Director
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Nucicar Regulatory Commission Region IV a;.
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611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012
Dear Mr. Howard:
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No. DPR Docket No. 50-267 Enclosed please find a copy of Unusual Event Report No. 50-267/75//.,
preliminary, submitted per the requirements of the Technical Specifications.
Very truly yours, (J
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s II. Larry Brey Superintendent-Operations Fort St. Vrain Nulcear Generating Station' IILB:11 cc:
Mr. Angelo Giambusso' 1
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3001' 8311020218 750314 PDR ADOCK 05000267 i
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REPORT DATr:
March 12, 1975 UNUSUAL EVENT OCCURRENCE DATE:
February 13, 1975 FORT ST. VRAIN NUCLEAR GENERATIMG STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT ?;0. 50-267/75/4 Prel iminary IDENTIFICATION OF OCCURRENCE:
As the result of having very high moisture levcis in the primary coolant circuit, we have experienced sone erratic operation of control rod and failure of the orifice position indicators and in a few instances, pot en t iotie te rs. This is defined as an Unusual Event per Technical Specification A.C. 7.6, Non-Routine Reports, c) 2.
- CONDITIONS PRIOR Routine Shutdown TO OCCURRENCE:
Steady Siate Power Hor Shutdown Routit.e Load Change
- Conditions at time of Reactor Cold Shutdown X
Other (specify)
Shutdown c1 1/23/75.
Refueling Shutdown Reactor critical a g gproxi-__
Routine Startup nately 10-5 % of Rated Thernal
, Power for trainA g urr;oses.
The major plant parameters at the time of the event were as follows:
Power RTR 0
MWth Elect.
O NWe Secondary Coolant Pressure 1250 psig Temperature 182
- F Flow
~349,000
- /hr.
Primary Coolant Prensure 234
_ psi r.
Temperature 332
- F Core Inlet 193
- F Core Outlet Flow 2 x 10
_ f/hr.
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Page 2 DESCRIPTION OF OCCURRENCE:
On February 13, 1975, on the 8-4 shift, preparations were being made to take the reactor critical to further study the reactor cot e-reactivity anomoly (see Abnormal Occurrence 50-267/75/7) when it was noted that the control rod analog position indication from Region 7 was not indicating properly.
A check of all control rod and orifice position indications indicated potential problems with ten (10) potentiometers out of a total of one hundred eleven (111).
APPARENT CAUSE OF OCCURRENCE:
Design X
Unusual Service Cond.
Including Environ.
Manufacture
_ Component Failure Installation /Const.
Other (specify)
Operator Procedure Eccause of the location of the control rod drive assembly in the upper head 4
or the vessel, it la capveed iv G.c suvicat scrticr. cf th cystem.
P-r nllf, a continuous purge of dry helium bathes the upper portion of the control i
i rod drive assembly to prevent migration of priuary coolant into the mechanism.
j Because of the high moisture levels experienced in the primary coolant system, see Abnormal Occurrence 50-267/75/3, we, at times, had both Helium Purification Trains expended and found ourselves regenerating one train with the other train needing regeneration.
During these periods of time it was necessary to shut the purification system down and by so doing, the dry helium purge uas lost.
Because of the high moisture levels in the primary coolant and lack of penetration purge flow, moisture apparently condensed in the subject potentiometers.
ANALYSIS OF OCCURRENCE:
As discussed under cause, the presence of moisture in the potentiometer uith voltage potential applied, produced a condition that caused some corrosion of the slide wire.
To be assured that only those potentiometers that read open or very low were affected by the moisture, a special test was developed by the manufacturer and run here at the plant on all the installed potentiometers.
The test was composed of two parts:
1.
With an absolute pressure of < 10 mm lig. In the primary system, dissipate 5.5 watts of power for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> in each potentiometer to dry.it out and fall any unit which may have a particularly corroded through slide wire.
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Page 3 2.
Measure resistance of each potentiometer at the end of the eight (8) hour dry out period.
Acceptance Criteria 1000 1 50 H.
3.
Stroke potentiometer to determine electrical noise Icvel from brush.
4.
Meggar the potentiometers to ground.
Step 3 and 4 have not yet been completed.
CORRECTIVE ACTION:
Those potentiometers that fail the test will be r'placed.
e FAILURE DATA /
SIMTLIAR REPORTED OCCURRENCES:
None.
For associated information see Abnormal Occurrences 50-267/75/3 and 50-267/75/7.
PROGRAMMATIC IMPACT:
None CODE IMPACT:
unna 4
Recommended:
Approved:
hN Y
s.
-a t_.-_, s F. M. Mathie Frederic E.
Swart Superintendent-Maintenance Superintendent Nuclear Production Fort St. Vrain Nuclear Public Service Company Generating Station of Colorado O
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