ML20084J255
| ML20084J255 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 03/02/1973 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084J247 | List: |
| References | |
| BBS-73-37, NUDOCS 8305120282 | |
| Download: ML20084J255 (2) | |
Text
, _ _
Com@ wealth E" son
( i Ouad-ms Nuctnt Pow:r St tion V
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Post Offica Box 216 Cordova, tilinois 61242 Telephone 309/654-2241
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BBS-73-37 70,N 5 i
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Mi, & r.Lu:'US #y;n March 2, 1973 i
Mr. Angelo Giambusso i
Deputy Director of Reactor Projects Directorate of Licensing U. S. A tomic Energy Commission Washington, D. C. 20545 Reference :
Quad-Cities Nuclear Power Station Docket Numbers 50-254 and 50-265 License DPR 29 & 30, Appendix A Sections 1.0.A.2 and 3.1
Dear Mr. Giambusso:
The purpose of this letter is to inform you of the details concerning the setpoint. drift of the pressure switches which monitor the condenser vacuum and initiate a reactor scram.
During routine surveillance calibration'of the Unit 1 switches on February 22, 1973 and the Unit 2 switches on February 21, 1973, six switches were found to be set _atyeateg._ thal 2,3"j[g contrary to Technical s
' Specification 3 1.
This abnormaToccurrence was reported to Region III Compliance by telephone on February 23, 1973 The switches involved are all Barksdale Model DTT-H18SS with a specified accuracy of 3" Hg.
The setpoints were
,, f found as follows:
Jv UNIT 1 UNIT 2
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gj PS 1-503B 22.88" PS 2-503A 22.83 7yj PS 1-503C 22.82" PS 2-503B 22.85
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PS 2-503C 22.60
/Q PS 2-503D 22.60 l\\ /
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The safety function of the condenser low vacuum scram is to anticipate the stop valve closure scram.
The stop valve closure occurs at a condenser vacuum of 20" Hg and also
/.g q.g$y includes an anticipatory scram from valve limit p es COPY SENT REGION _b y 2
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Mr. Angelo Giambusso March 2, 1973 b
which was operable at, all times.
With the existing set-points,and logic a scram would have occurred on Unit 1 at > 23" Hg vacuum and on Unit 2 at 22.8" Hg.
The safety significance of this instrument drift is therefore con-sidered to be minor.
Setpoint. drift problems have been experienced before with these switches.
As a result of the review of instrument setpoints described in my letter dated December 1,1972 the calibration setpoint of the low vacuum scram was changed to 23 3" Hg.
Since this change did not provide an adequate margin to prevent a drif t beyond the LCO,
, the setpoint has been increased to 23.6" Hg.
Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIESNUCLEJA POWER STATION l
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V' ~gkq5' B. B. Ste enson Superintendent BBS/zm s
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