ML20085J870
| ML20085J870 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/12/1974 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085J874 | List: |
| References | |
| 421-74, NUDOCS 8310190153 | |
| Download: ML20085J870 (2) | |
Text
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One Fir:.
nonal Plaza Chicago. Ilknois Address Rep!y to: Pcat Office Box 767 Chicago, ll!inois 6C690 J
BBS Ltr.#421-74 Dresden Nuclear Power Station 2
R. R. #1 y'
n.3 Morris, Illinois 60450 N
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^ 4 (,,'., M June 12, 1974
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%f& Q Mr. J. F. O' Leary, Director
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Directorate of Licensing U ;'
A U. S. Atomic Energy Conmission N
Washington, D. C.
20545 fu
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, REPORT OF arf!ORMAL OCCURRENCE PER SECTION 6.6.B.1.a OF THE TECIINICAL
_ SPECIFICATIONS.
HPCI LOW PRESSURE ISOLATION INSTRUMENT DRIFT.
References:
- 1) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura, 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on June 4, 1974 Telegram: Mr. J. Keppler,1425 hours0.0165 days <br />0.396 hours <br />0.00236 weeks <br />5.422125e-4 months <br /> on June 4,1974
- 2) Dwgs: P & ID M-51 S&L 12E2528 8
Dear Mr.
0 I.ameve This letter is to report a condition relating to the operation of the unit at about 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on June 3,1974. At this time, high pressure coolant injection (HPCI) low pressure trip switches PS2389 A, B, C and D were found with setting above 90 psig. This malfunction is contrary to section 3.5,0.1 of the Technical Specifications which requires that HPCI be operable whenever reactor pressure is equal to or greater than 90 pa y.
PROBLEM At the time of the occurrence, Unit 3 was in the refuel mode, with normal refuel surveillance in progress. During routine surveillance of PS2389 A through D, all four switches were found with setpoints above the Technical Specification of f,90 psig. The switches were immediately recalibrated to comply with the Technical Specifications. The "as found" and "as lef t" settings were as follows:
PS "As Found" Less Head Equivalent "As Left" at switch Correction Rx Pressure at switch 2389A 125' psi 25 psi 100 psi-109 psi 23895 118 psi 25 psi 93 psi 109 psi 2389C 125 psi 25 psi 100 poi 110 psi 1
2389D 121 poi 25 psi
- 96 psi 107 psi t
pi
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' Mt. J. F. O'Lenry Junn 12, 1974 The pressure switches in question are Barksdale Model B2T-Al2SS with bourdon tube operators. The function of the switches is to trip the RPCI turbine when reactor pressure dropa below the pressure range at which the RPCI turbine is operable. To comply with the Technical Specifications, the switches must reset below 90 psi increasing pressure.
INVESTIGATION The Barksdale Model B2T-A12SS has had a history of setpoint drif t.
The problem has been defined by the vendor as a lack of pre-cycling prior to installation. The setpoint on the 2389 A through D switches drif ts in both the increasing and decreasing direction. This is symptomatic of an unstable suitch. The pre-cycling process stabilizes all mechanical compon-ents in the switch, and thus decreases drift. A program is presently under-way to return all Barksdale switches to the factory for pre-cycling.
_ CORRECTIVE ACTION The switches were immediately reset to comply with the Technical Specifications. The switches will be returned to the factory for pre-cycling as soon as practicable.
FVAT,UATIOM The electrical arrangement of the 2389 A through D switches is such that the HPCI turbine would have been operable at 96 pais. Previous testing of the switches was performed on February 9, 1974, when they were found to be within specifications. At the time of the occurrence, the reactor was in the refuel mode and HPCI operability was not required.
It is therefore concluded that the safety of the general public or plant personnel was not jecpardized as a result of this occurrence.
The cumulative experience to date indicates that pre-cycling is the proper course of action to limit setpoint drif t on Barksdale switches.
Switch setpoint history will be observed after the switches are pre-cycled to assure the corrective action is adequate.
Sincerely,
). hAttk)^ kA B. B. Stephenson Superintendent BBS:WEH:do l
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