ML20024G491
| ML20024G491 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/25/1972 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102120558 | |
| Download: ML20024G491 (4) | |
Text
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Washington 25, D. C.
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Dear Dr. Lb r r i s-
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LOfCICELLO f0 CLEAR GEfERATI fG PLAfR Docket fjo. 50-263 License fjo. IFR-22 Reporting of Occurrences Three conditions have occurred recently at the Lbnticello fjueleer Generating Plant which we are reporting to your office in accordance wi th Section 6.6.C of the Technical Speci fi cat ions.
The Region lli Corpliance Of fice has been noti fied of these occurrences, l.
Imorecer Functioning of R4R Service Water Renulating Valve Cont rol On March 28, 1972, the B Loop of the RHR Service Water System was started for a test.
The service water regulating valve (CV-1729) was observed to be fully open while the shell to tube differential pressure controller was calling for the valve to be fully closed.
This valve and control system is designed to maintain the service water pressure in the heat exchanger tubes above the pressure of the water in the shell of the heat exchanger.
This dif ferential prevents primary water from leaking into the service water in the event of a tube leak.
T he electronic to pneumatic transducer (E/P) was found to have been recalibrated on March 18, 1972, as a direct instead of a reverse acting instrument.
Adrrinistrative procedures which require functional testing of systems or components prior to their return to service after maintenance were not followed.
The cause of the miscalibration was traced to incorrect calibration records which l
indicated that the E/P was a direct acting instrurysnt.
I li should be noted that the ability of the B Loop of the RHR system to perform its requi red containment cooling function was not affected by the error.
The following corrective action has been taken:
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a) The E/P was recalibrated and proper performance was verified by a functional test.
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b) T he req;irerents for functional testinc followine maintenance work have been reviewed wi th the appropriate personnel.
- Also, a core has been issued to remind the of t he necessi f y for, and reans for irpleronting these reg >irerents.
c) The calibration records have been corre:ted.
2.
f.%1 (u nc t i on o f rentai nrent I selat ion Valve hhile conductire a routine surveillance test on April 3,1972, it was found that the High Pressurc Coolant in jection System outboard steam isolation valve, f.0-2035, would not close. 1 he retor was operating, but, the Cears were not er. gaged.
The last tire the valve had beer opened was on f/ arch 18. 1972.
At that iire ii had been nanually backseated to prevent steam leakage, f3anual operation of the valve operator will disengage tho motor pears, benever, the notor tears should automatically engage when the motor is energized.
An operator was sent to the valve and manually ini tiated i ts closure usine the local handuheel. As the valve started to close the notor gears engaged and the valve could then be opereted fully open and closed in normal f ashion.
During a convenient plant outace the valve operator will be tested to see i f the mal function can be duplicated and the operating rechanism will be inspected.
Instructions have been issued to prohibit manual backseating.
3.
WC I Stea-line Hich Area Temerature Swi tch On April 3,1972, the setpoints of sixteen temperature switches used in the HPCI Steam Line-High Area Temperature isolation loc c i
were tested prior to installation.
One tenperature switch did not trip with terperature raised to the boiling point c' water.
The Technical Specifications requi re that they be set to irip at $_200 f.
The switch setpoint was adjusted and it then repeatably tripped at the desired setting, however, i t was decided to irctall a spare swiich.
To allow temperature switch iesting to be carefully performed i n t he s hop, rather than in-plaa, and to minimize the tire that the HPCI steam line is isolated while calibration test work is in progress, two sets of 16 temperature swi tches are used.
E ve r y three months, when calibration is due, a set of switches is calibrated, installed as replacements, and functionally tested.
The swi tches removed f rom service are stored until the next calibration is due, at which tire they are calibrated, installed as replacerents, and functionally tested.
Because of this procedure it is not possible to determine for certain if the switch was actually out of calibration during the tire i t was in service, or whether it becare out of calibration as a result of handling and storage.
It should be noted that the failure of a single tempera-ture switch would not defeat the hi since the redundan' switch in the (gh temperature isolation function 1 of 2) twice logic would be available.
The 16 ' witches removed from service on April 3rd were shop tested ar.J all were found to trip within the allowable 1imit.
3-lhe terporaturc swi tch test piecedures have been revised t o i nc l u de an ".re found" s alibrat ion the k i t raidi atel y upon reroval f rom servi ce, lhe noginal swi tch setpoints will be reduced to the rance of 14r>-190 F to accorndate poscible C nally f ailed to trip i
setpoint drift.
T he swi tch which ori on April 3rd has been returned to the factory for analysis.
Sienificant Operating Event Eeports for these occurrences will be available at the plant f or review by the Region t il Compliance inspec4or.
Yours very truly, L. O. '/.a y e r Di rector c' Nuclear Support Services LOW'.H0/k i k ec:
B 11 Grier
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AEC DISTRIDlTTION FOR PART_,50..
DCWW PATERIAL f,TaiPORAhT F0101 )
CONTROL NO: 2376
~~hChi Northern States Power Co.
F DATE OF DOC:
DATE REC'D LTR MEMO RPI OTHER Minneapolis, liinn.
55401 4-25-72 5-2-72 X
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C.i t G CC UIRER SENT AEC PDR k
Dr. Peter A. Morris 1 signed 39 SENT IhCAL PDR-Y CLASS: Q PT.0'c 1;u 0 lia'vT KO CYb REC'D DOCKL'r NO:
40 50-263 DESC RIP'nON : Ltr rpt three occurrences vnw L:iCLC$lird ;
occurred at the Monticello Plant involving th<
improper funcitioning of RHR service water regulating valve control on 3-28-72, the malf onction of containment isolation valve on 4-3-72 & th" M Mna' gr,r..p HPCI steamline-hiph area temperature sulten..
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