ML17252A985
| ML17252A985 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/19/1973 |
| From: | Worden W Commonwealth Edison Co |
| To: | Anthony Giambusso US Atomic Energy Commission (AEC) |
| References | |
| WPW Ltr.#320-73 | |
| Download: ML17252A985 (2) | |
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Commonwealth Edison Company 0 NE FIR 5 T NAT I 0 NA L PLAZA
POST OFFICE BOX 767 *CHICAGO, ILLINOIS 60690 so-249 WPW Ltr.f/320-73 Dresden Nuclear Power Station Mr *. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U.
S~ Atomic.Energy Commission Washington, D~ C.
20545 R. R. ill Morris, Illinois April 19, 1973
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6.6.B.3 OF 'l'HE TECHNICAL SPECIFICATIONS,
Dear Mr. Giambusso:
This is to report a condition relating to the operation of the unit in which, on April 13, 1973, two of four sustained high reactor pressure switches were found tripping at 1075 and *1gf~'I:;psig during sur-veillance testing.
This is above the Technical Specification limit of
~ 1070 psig for 15 seconds, as. described in Table 3.2.2.
PROBLEM AND INVESTIGATION During a surveillance inspection of the sustained high reactor pressure switches, the setpoints for Meletron switches 3-263-53B and 53D were found to have drifted to 1075 and 1073 psig, respectively.
The switches had previously been set at 1056 and 1058 psig, respectively.
The purpose of these switches is to initiate use of the isolation condenser as a heat sink in the event that. reactor pressure reaches 1070 psig or greater for at least 15 secon.ds.
- The isolation condenser was not required at the time the surveillance i~spectiOU*W8S performed, since the reactor was being refueled.
Had the isolation condenser been required prior to shutdown for refueling, it would have operated at *a sustained reactor pressure of 1073 psig, only slightly above *the Technical Specificati,()~S limit o*f ~ 1070. psig.
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- i<"i~. A. Giambusso
.;.2-e April 19, 1973.
The pressure switches are connected-into a logic sequence, of one out of two taken. twice, so that overpressure trips on 263-S3A or C, and 263-53B or
- D place 'the system in operation.
Switches 53A and 53C were found set within Technical Specification limits, and 53B would have tripped at 1073 psig.
- Thus, the failure of switches 3-263-53B and 53D did not present a hazard to the public safety.
CORRECTIVE ACTION
- The inl:nediate corrective action was to reset the pressure switch trip points to 1052 psig for 53B and 1056 **for 53D.
The Meletron model 372 pressure switch bas.. shown a histocy of drift in both the upward and downward direction. (Reference our letters dated Aug\\Jst 1, 1972 and September 18', 1972). A spare switch of this type is presently being investigated under actual operating conditions by.the Station. Instrument Department to determine the cause of setpoint drift.
Findings of the investigation will dictate future corrective actions.
In addition, for the next 3 months, these pressure switches. will be calibrated on a monthly basis. At that time, an evaluation will be made
. to determine. frequency of *future calibrations.
WPW:do cc:
- WPW Lt~. File Sincerely,
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W*. P. Worden
- Superintendent
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