ML17252A533
| ML17252A533 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/19/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| BBS Ltr. #441-74 | |
| Download: ML17252A533 (2) | |
Text
.
Commonwealth Edi.
One First National Plaza, Chicago, Illinois Address R~ply 10:-fost Office Box 767 Chicago, Illinois 6u690 Mr. J. F. O'Leary. Directo~
Directorate of Licensing U. s. Atomic Energy Commission Washington, D. C.
20545 50-249 SUBJ!Cl:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT f}J~ REPORT OF ABNORMAL OCCURRENCE PER SECTION 6.6.B.l.a OF THE TECHNICAL SPECIFICATIONS.
REACTOR HIGH PRESSURE.
References:
- 1) Notification of Region III of AEC Regulatory o_.__,,,,..,..,
Telephone: Mr. F. Maura, 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on 6/12/7 Telegram: Mr. J. Keppler. 1358 hours0.0157 days <br />0.377 hours <br />0.00225 weeks <br />5.16719e-4 months <br /> on 6/12
- 2) Dwgs: P & ID M-26 S & L 12E2464
Dear Mr. O'Leary:
This letter is to report a condition relating to the of the unit at about 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on June 11,- 1974.
At this tbbe, t~o of the reactor high pressure scram switches were found with *setpointlP*of 1064 psi and 1066 psi. This malfunction is contrary to Table 3.1.1 which requires a setpoint of ~ 1060 psig.
PROBLEM At the time of the occurrence, Unit 3 was operating at a steady load of 460 MWe.
During routine monthly surveillance of reactor high pressure switches PSJ-263-55 A,B,C and D, switches A and C were. *found with setpoints of 1064 psi f and 1066 psi ~ respectively. These setpoinls are above the Technical Specification limit _s_ 1060 psi. The switches were immediately reset to 1048 psi and 1044 psi. The normal function of these switches is to p'novtdeJ,a reactor scram if pressure reaches a value of 1060 psi.
INVESTIGATION This violation of setpoint limit is attributed to instrument drift. The switches are Meletron Model 372 pressure sensors with bourdon tube operators.
The switches are very similar to the Barksdale Model 132T-AlSS which bas an 4nherent drift tendency.
The vendor recomnended
. REGULATORY DOCKET FILE,COPY; 5785
r
- r.
- e Mr. J. F. O'Leary.. " \\..
- June 19, 1974 fix for the Barksdale switch is to__ret~rn_it-to-tbe-factory--f~n*-pre;;;cycfiiiS.
_______ ----=A:.::lo.::l=_,m.@.~ufacturing--in1d -servfC:e-fOr Meletron switches is now performed by the Barksdale Company.
Therefore, the Meletron switches will be sent to Barksdale, Inc. for pre-conditioning *
. CORRECTIVE ACTION A program.is presently in progress to pre*c6ndition all Barksdale and Meletron bourdon tube type switches. The reactor high pressure switches will be pre-conditioned as soon as practicable. At this *time, Unit 2 bas 8 pre-cycled switches installed and Unit 3 bas 4 pre-eye.led switches installed.
Eight more switches are now at the factory for pre-cycling.
EVALUATION The switches tn question are 'two.. of four which are connected in a "one out of two twice" logic configuration. This would have provided a scram at 1064 psi, which is.. only slightly above the 1060 psi,Te<?hnical Specification value~. 'it is *therefore conclu4ed ~bat the s4fety ;,~f.. the, plant personnel or the ge~eral public was. riot jeopardized as' a result of. thiS occurrence.
The cumulative experience with these switches does not indicate that more frequent calibration of them would be of;:;*any help.
The cumulative experience of pressure switch drift is inconclusive at this time because of lack of history, however, the vendor indicates that lack of pre-cycling is the cause of the persistent drift problem at Dresden Station.
t£ B. B.
BBS:WEH:do