ML20084J271
| ML20084J271 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 02/26/1973 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084J247 | List: |
| References | |
| BBS-73-31, NUDOCS 8305120302 | |
| Download: ML20084J271 (2) | |
Text
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1 Mr. Angelo Giambusso Deputy Director of Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C. 20545 Re ference:
Quad-Cities uclear Power Station, Unit 1 Docket No. 50-254 License DPR-29, Appendix A, on 1.0.A.2 and 3 2.A.
Dear Mr. Giambusso:
The purpose of this letter is to inform you of the details concerning the setpoint drift of PS-1-261-300.
The setpoint was found to be at 848 psig decreasing during a routine calibration on February 14, 1973 This is contrary to Section 3.2.A. of the Technical Specification which requires the switch to trip at 2850 psig.
The switch is a Barksdale Model B2T-M12SS with a range of 0-1200 psig.
The accuracy of the switch is 1 per cent.
This particular switch is in the "A" logic of the Primary Containment Isolation System and is intended to isolate the pressure vessel to prevent rapid depressurization.
It is one-out-of-two-twice logic and as such, because all three of the other Main Steam Line Low Pressure switches were within limits, the system would have performed its intended function.
Drif t problems have been encountered before with this type of switch.
The previous measures taken to prevent a re-petition were to increase the switch setpoint to 858 psig decreasing and, to increase the frequency of calibration from quarterly to monthly.
As a result of this occurrence
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Mr. Angelo Giambusso 2-February 26, 1973
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A the setpoint has been increase again to 864 psig and monthly, calibrations will continue.
This new setpoint will allow the instrument to drift within the 1 per cent accuracey (12 psig).
Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION dh : bad hit. B. B. Stephenson Superintenden t BBS/zm
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