ML17252A537
| ML17252A537 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/12/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| BBS Ltr. #421-74 | |
| Download: ML17252A537 (2) | |
Text
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, REPORT
- OF ABNORMAL OCCURRENCE PER SECTION 6.6.B. l.a OF THE TECHNICAL.*
SPECIFICATIONS.
HPCI LOW PRESSURE ISOLATION INSTRUMENT DRIFT.
References:
- 1) Notification of Region III of ABC 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 Te.legra'm: 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
Dear Mr. O'Leary:
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 (BPCI) 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.C.l of the Technical Specifications which requires that HPCI be operable whenever.reactor pressure.is equal to or greater than 90 psig.
PROBLEM At the time of the occurrence, Unit 3 was in the refuel mode, with normal refuel surveillarice in progress. During routine surveillance of PS2389 A through D, all four switches were found with setpoints above the Technical Specification of.~ 90 psig. *The switches were immediately reealibrated to comply with the Technical Specifications. The "as found" and "as left" 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 23898 118 psi 25 psi 93 psi 109 psi 2389C 125 psi 25 psi 100 psi 110 psi 2389D 121 psi 25 psi 96 psi 107 psi 5401
- i
- e Mr. J. F. O'Leary
\\,_ *~
June 12, 1974
________ ------------The-pressure-switchea--in*-que*st*ionare-BarlisclSleModel B2T-Al2SS with bourdon tube operators. The function of the switches is to trip the HPCI turbine when reactor pressure drops-below the pressure range at which the HPCI turbine is operable. To comply with the Technical Specifica.tions, the switches nnast res?t. below* 90 psi ~creasing -pressure.*
INVESTIGATION f...... -* :;' *~
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I ' ~'
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- .-r The Barksdale'Model-B2T~Al~SS tuJs* had a history of set~oint: drift.
The prob.em has been* defined by the vendor as a lack of pre-cycling prior to installation. The setpoint on the 2389 A through D switches drifts in both the increasing and decreasing direction. This is symptomatic of an unstable switch. The pre-cycling process stai(!*lizes all inecha~ical compon-ents in the switch, and thus decreases drift. A program is presently under~
~ay to return all Barksdale switches to the factory for pre-cycling*
OORRECTIVE ACTION The switches were immediately reset to comply with the Technical Specifications.* The switches will be r~turned to the factory for pre-cycling
- as soon as practicable.
EVALUATION.@
The electrical_ arrangement of the 23S9 A. through D 'witches is such _that the HPCI turbine would have* been operable at 96 psig. Previous testing of the switches was performed on February 9, 1974, when they were fo\\,ltid to be within specifications. At the time of the occurrence,. the
. reactor 'was in the refuel mode _and HPCI operability was riot required. It *
- is therefore concluded that the safety of the general public* or plant personnel was not jeopardized as a result of this occurrence.
The cumulative experience to date indicates that pre-cycling is the.proper course of action to limit setpoint drift on Barksdale switches.
Switch setpoint history will be. observed after the. switches are pre-cycled to assure the corrective action is adequate.
BBS:WEH:do Sincerely,
~/JJ~.
B*. B. Stephens~
Superintendent