ML17193B051
| ML17193B051 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/18/1972 |
| From: | Worden W COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 5203, NUDOCS 8103110077 | |
| Download: ML17193B051 (2) | |
Text
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fJ~tatory:
~tie ~:-
. Common we al th Edison Company ONE FIRST NATIONAL PLAZA
- CHICAGO.
ILLINOIS Addreu Reply to, P 0 ST Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. s. Atomic Energy Conunission Washington, D. C.
20545 ILLINOIS 60690 Dresden Nuclear Power* Station R. R. ifl Morris, Illinois 60450 September 18, 1972
SUBJECT:
LICENSES DPR-19 and DPR-25, DRESDEN NUCLEAR POWER STATION, UNITS 2 and 3,
-SECTION 6.6.B.3. of the TECHNICAL SPECIFICATIONS
Dear Mr. Giambusso:
This' is to report a condition relating to the operation of Units 2 and 3, in which on S~ptetl)ber 8 and 9, 1972,. five of the eight."electrohydraulic cont.rol (EHC). oil low press*ure scram switches" setpoints dr~f ted beyond the setpoints established in Section 3.* 1 of the Technical Specifications.
PROBLEM As reported in our letter of August 23, 1972, it was found that during August's 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 investigative proceedings, all of the EHC switches were calib~ated this month rather than just functionally checked as required by the Technical Specifications (once per month-Technical Specification Table 4.1.1).
As a result of this calibration three switches on Unit #2 and two switches on Unit #3 were found to have drifted below 900 psig.
Switches PS-LS-1,-2, and -3 on Unit #2 had drifted to 881,880, and ~4*6 psig, respectively, and switches PS-LS-1, and -4 on Unit #3 had drifted to 895 and 818 psig, respectively, INVESTIGATION T~ Two of the five switches, PS-LS-3 on Unit #2 and PS-LS-4 on Unit #3, are the new Barksdale model TC-9622-2 with a setpoint range of 250-1500 psig *
. Both switches had drifted more than the Tl% instrtime~t 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
- experienced previous drifts below 900 psig.
The latest readings on the
. set points of these three switches are all within the T 1% instrument scale
'fj/03f/ol'1J'f}icy corresponding tot 30 psi.
144",.
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I seilmber 18,1972
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.),1.r.~* ":Ar. Giam usso CORRECTIVE ACTION All eight switches on Units 2 and~3 were recalibrated to trip 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 Spec.d:fication Table 4.1.2.
In addition, PS-LS-4 on Unit 113 wil.l be calibrated on a weekly basis until the setpoint drift problem can be corrected.
The reason for setpoint dri~t in these switches is under investigation. 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 Mr. Worden dated July 27, 1972 and again in a letter to Mr. Gj,ambusso from Mr. W£lr.den d~.ted August 23, 1972.
Different types of pressure switches with lower tend~ncies to drift are being considered for use in Units 2 and 3.
No recommendations or conclusions have been made to date.
~.
WPW:.mt
~.
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Sincerely, JJLO-cR~. UA~
n'.......t W. P. Worden r -$uperintendent Dresden Nuclear Power Station
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