ML17252A926
| ML17252A926 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/22/1974 |
| From: | Worden W Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| WPW Ltr. #51-74 | |
| Download: ML17252A926 (2) | |
Text
WPW Ltr.#51-74 iegulatory Docket File-
SUBJECT:
Dresden Nuclear Power Station
- . R.
R~ {Jl*
50-249 Illinois 22, 1974
References:
- 1) Notifieation of Region III of AEC Regulatory Operations Telephone:
Mr. Maura at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on 1/15/74.
Telegra~: Mr. Keppler at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on 1/15/74.
- 2) Dwgs: P & ID M-346
Dear Mr. O'Leary:
This letter. is to report a condition relating to the operation of the unit at about 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on January 14, 1974. At this time condenser low vacuum scram switch PSL 3-S03C was found to operate at 22.35 inches of.Hg.
. This malfunction is contrary to Table 3.1.l of the Technical Specifications* which requires the condenser vacuum switches to be set
~t greater or equal to 23 inches Hg vacuum*
PROBLEM At the time of the occurrence, Unit #3 was operating at a steady load of 620 MWe.
The Instrument Department was conducting rou.tine monthly surveillance testing on condenser low vacuum scram switches.
PSL3-503A, B, C and D.
At this time, PSL3-503C was found to actuate at 22.35 inches Hg vacuum, which is 0.65 inch Hg vacuum below the required setpoint. The switch was immediately reset Q:"][:::,23. 75 inch Hg vacuum.
The function of PSL3-503C is to scram the unit in the event condenser vacuum falls below 23 inch Hg.
This vacuum level is necessary to assure adequate heat sink capability of.the condenser.
1',
.\\ '*'
a Mr. J. F. O'Leary *January 22, 1974 INVESTIGATION PSL3*503C is a Barksdale Model DlT-Hl8SS diaphragm pressure switch with a 0;~4 to 18 psi range.
The switch was found below the Technical Specification limit once in 1973 and in October of 1973 the switch was found set at 25.S inch Hg which wa'.s above the Dresden target band of 23.7.+/- 0.2 inches Hg.
No violations occurred in 1972.
,The performance of the four switches as a group is unreliable_. 'l'hey seem to be susceptible to periodic c;hanges after peri9(is of st~ble repeatability.*
~,
- ~**'
CORRECTIVE ACTION*
somewhat in setpoint At this time~ PSL3-S03A,B~C and D do not appear to have the repeatability necessary to **coniistently comply with the Technical Specifi-cations.
To correct the problem, a different type of switch will be installed on Unit 3 for evaluation.
Vacuum.switches manufactured by the Static-0-Ring Corporation have exhibited ~ery good reliability on similar applications.
The new switches will be installed as soon as Quality Assurance procedures and approvals can be completed, and the new switches received from the vendor.
EVALUATION PSL3*503C and A both provide scram signals to scram channel "A".
Switch "A" was found to comply with the Technical Specification requirement and functioned properly when tested. It is therefore concluded that the redundant circuit system functioned as designed and therefore the safety of the plant personnel or th~ general public was in no way jeopardized as a result of this.occurrence.
WPW:do Sincerely, P w /}.
. w. ~-
- w. P. Worden Superintendent