ML20084F255
| ML20084F255 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/31/1973 |
| From: | Worden W COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20073L568 | List: |
| References | |
| 84-73, 870, NUDOCS 8304210060 | |
| Download: ML20084F255 (2) | |
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50-237 Commonwealth Edison Company 72 WEST ADAMS STRdET
- C H I C A G O.
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- C M I C A G O, IL LIN OIS 4049 0 Dresden Nuclear Power Station R. R. #1
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WPW Ltr. #84-73 January 31, 1973 i
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Mr. A. GiAmbusso c)
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Deputy Director for Reactor Projects g'
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Directortte of Licensing
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U.S. Atomic Encrey Commission Washington, D.C.
20545 1
SUBJECT:
LICFNSE DPR-19. DRESDEN NUCLEAR POWER STATION. UNIT #2. SECTION 6.6.B.3 OF THE TECHNICAL SPECIFICATIONS.
Dear Mr. Giambusso:
This is to report a condition relating to the operation of the unit in which, on January 23, 1973, the setroint of one of the condenser low vacuum scram switches was found below the limit defined in Table 3.1.1 of the Technical Specifications.
PROBLFF AND INVESTIGATION On January 23, 1973, during a routine quarterly calibration, one of the four condenser low vacuum scram switches was found tripping below the Tech. Spec.
limit of' > 23 inchos of mercury. This is the first time the subject switch has drifted below this limit.
The~cubject switch, PS-2-503; was previously set at 23.31 inches of mercury on October 16, 1972. Cn the above date, this switch was found tripping at 22.45 inches of mercury. This slight drift would have little or no effect on the safe shutdown of the reactor.
The switch is a vacuum operated Barksdale model DlT-H18SS, with an adjustable range of.4 - 18 psig and a setpoint accuracy cf i 15. (t.37 inches ofmercury) 9?"jf pq UNE88t*d88sasy 870 PDR
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, CORRECTIVE ACTION s'
The switch was immediately recalibrated and lef t at 23.25 inches of mercury.
Af ter reviewing Barksdales spec'ifications, it was found that this model switch has a setpoint accuracy of i.37 inches of mercury, almost twice the tolerance that the station is now allowing. Dresden's setpoint limits are currently 23.3 i.2 inches of mercury for all eight condenser low vacuum switches on both units 2 and 3.
As a temporary step to correct this problem, the station limits 1
for condenser low vacuum scram switches on both Unit 2 and Unit 3 will be changed to 23.7 i.2 inches of mercury, allowing for nominal drif t wtthin the accuracy of the instrument.
The investigation of switch setpoint drift will continue until the problem has been resolved.
Sincerely,
'%au W. P. Worden Station Superintendent l
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WPW Ltr. File 1
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