ML17252B024
| ML17252B024 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/18/1972 |
| From: | Worden W Commonwealth Edison Co |
| To: | Anthony Giambusso US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17252B024 (2) | |
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Commonwealth Edison Company 0 N E F I R S T N A T I 0 N A L p* L A Z A C H I C A G 0, I L L I N 0 I S
- CHICAGO, ILLINOIS 60690 Dresden Nuclear Power Station R. R. 1fl
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.Morris, Illinois 60450 September 18, 1972
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Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C.
20545
SUBJECT:
LICENSES DPR-19 and DPR-25, DRESDEN NUCLEAR POWER STATION, UNITS 2 and 3,
--SECTION 6.6~B.3. of the TECHNICAL SPECIFICATIONS I
. i
Dear Mr. Giambusso:
Thi.s is to report.a *.condition.r:elating to the operation of Units 2
... and. 3,.in. whJch. qn_ Se.pt~l!ll:>e,r. -~ -~~~~-92. ~?7_2,; ;ive o_f t.he eight. "electrohydraulic control (EHC) oil low pressure scram swt'tches. "setpoints dr{ft:e'a beyond* * * *
- the setpo.ints.e-stablished.in Sect-ion 3.1 oCthe. Technical SpE;_cifi~a.tt9ns.
PROBLEM As ~eported i~ our letter of August 23, 1972, it was found that during August 1s calibration of the EHC switches (required every three months by Technical Specification Table 4.1.2) two of the eight subject switches' setpoints were found to have drifted beyound the setpoint of
.900 psig decreasing.
As part of the investigativa proceedings, all of the EHC switches were calibrated this month rather than just functionally checked as required by the Technical Specifications (once per month-
.Technical Speci~ication Table 4.1.1).
As a result of this calibration three switches on Unit #2 and two switches on U~it #3 were found to have drifted below 900 psig.
Switches PS-LS-1,-2, and -3 on Unit #2 had drifted to ~81,880, and 846 psig, respectively, and switches ps:..Ls-1, and -4 on Unit 113 had drifted to 895 and 818 psig, respectively.
. INVESTIGATION Two of the five *switches, PS-LS-3 on u*nit' 1f2 and PS-LS-4 on Unit #3, are the new Barksdale model TC-9622-2 with a setpoiht range of 250-1500 psig.
Both switches had drifted more than the +/-1% instrl.UTient scale accuracy corresponding to t 15 psi. No previous data is available on these two switches, since this was their first month of operation.
The other three switches have all I
experienced previous drifts below 900 psig.
The latest readings on the
. set points of. these three switches are all within the t 1% instrument scal.e
. tJJ accuracy corresponding to +/- 30 psi.
F
Mr. A~ Giambusso September 18,1972 CORRECTIVE ACTION All eight switches on Units 2 and 3 were recalibrated to tri~
at 935 psig, +/- 5 psig, decreasing, to allow for drifts within the tl% instrument scale* accuracy.
All switches.will continue to be calibrated monthly, as opposed to the once every three month re-quirement of Technical Specification Table 4.1.2.
In addition, PS-LS-4 on Unit #3 will be calibrated on a weekly basis until the set~oint drift* problem can be corrected.
The reason for setpoiht drift in these t
switches is under tnvestigation. This is a continuing problem.
Similar
- occurrences happened on July 15, 1972 and August 12, 1972.
These anomalies are.described in a letter to Mr. Block *from M-r. Worden da*ted July 27, 1972 and again in a letter to Mr. Giambusso from Mr. Worden dated August 23, 1972.
Different types of pressure switches with lower tendencies to drift
.are being considered for use in Units 2 and 3.
No recommendations or conclusions have been made to date.
Sincerely, Q_ -;. '.
-j/ :._cc -~. l L ( ~-\\iv.. -L-
{,z~ W. P. Worden f~ Superintendent.
Dresden Nuclear Power Station*
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