ML17252A543
| ML17252A543 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/10/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| BBS Ltr. #418-74 | |
| Download: ML17252A543 (2) | |
Text
BBS Ltr./1418-74 Regulatory Docket File Mr. J. F. O'Leary, Director
- Directorate of Licensing U. s. Atomic Energy Commission Washington, D. C.
20545
-~**
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, REPORT OF ABNORMAL OCCURRENCB PER SECTION 6.6.B.l OF THE TECHNICAL SPECIFICATIONS.
FAILURE OF M0-3-2301-3 TO OPEN.
Reference:
Notification of Region III of AEC Regulatory Operations Telephone~ Mr. J. Maura, 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />. on June 6, 1974 Telegram: Mr. J. Keppler, 1330 hour:s on June 6, 1974
Dear Mr. O'Leary:
This letter is to report a condition relating to the operation of the unit at about 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on June 5, 1974. At that time HPCI valve 3-2301-3 failed to open.
Thi.& malfunction is cont*rary to section 3.5.C.l 50-249 of the Technical Specifications which requires the HPCI system to be operable when reactor pressure is 90 psi or greater and irradiated fuel is in the core.
PROBLEM On Jµne 5, 1974 at about 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, Unit 3 HPCI valve 3-2301-3 failed to open. At the time of the failure, BPCI surveillance was in progress for the unit startup. During the valve operability tests, the
- valve was operated satisfactorily. However, during the sequence valve operations for HPCI pump operability test, the valve failed to open *.
At the time of the failure the unit was in startup and thermal power was 180 megawatts.
Reactor pressure at the time of the failure was 196 psi.
INVESTIGATION An investigation into the problem revealed that the main contactor in the supply *breaker for the valve failed to pick up.
The cause of the
- problem was determined to be due to a lack of clearance between the aux contact operating bar and the main contact armature roller. A lack of B455
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June 10, 1974
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c:le_a_r.!l~~e_wil l_.cause-a-greater*-open-pressure* t*o-blf appTi-ed*-To-tlie--ma in contactor armature.
The greater pressure is due to the fact that on initial pick up of the main contactor, armature open pressure will include the a\\lx contact spring pressure.
With clearance available the aux contact spring pressure will not be applied to the main contactor armature until it has I
. partially closed.
The failure of a main contactor to pick up can be due to two related causes.
In this case a lack of *ciearance between* the *in -c*o,nt~ct()r
- armature roller and the *aux '~onta'ct operating bar ~used t~e-<failure. How-.
ever, the same type of failure coul~ occur* if th~' ~i~. "8M> _betw~e.n, "th~ main contactor armature and the main contactor coil were tc;O'igreat.
Both *failures are related because any adjustment made to correct one condition could result in an incorrect adjustment on the other.
CORRECTIVE ACTION Since this type of.failure can be due to two causes, two correct~
ive actions were made. First, the air gap between the main contactor
- armature and the main contactor coil was adjusted.
Secondly, the clearing between the aux contact operating bar and the main contactor armature roller was adjusted.
Following both adjustments, the valve was cycled twice to verify proper operation.
In addition, the maintenance inspection procedure was changed to
. include a detailed instruction as to bow to make the required adjustments.
All the Unit 2 and 3 D.C. breakers will have the adjustments checked as soon as practical. Also, following the failure the required surveillance was performed.
EVALUATION This failure did not put the safety of the plant or public in jeopardy. At the time of the faUure all other safety systems were operational and would have insured a safe unit shutdown if necessary.
In light of cumulative experience, the corrective action taken is sa~is*
factory at this time.
BBS: TEL: do