ML17252B008
| ML17252B008 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/08/1972 |
| From: | Worden W Commonwealth Edison Co |
| To: | Anthony Giambusso US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17252B008 (2) | |
Text
'
~:..-.
. 1
.Be~-~~~~l; L~~~...,g!i Commonwealth Edison Company 72 WEST ADAMS.STREET
- CHICAGO, ILLINOIS -
-~-
67 *CHICAGO, ILLINOIS 60690 Mr. A. Giambusso.
DOCKETED USAEC Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission Washington, D. c.
20545 Dresden Nuclear Power Station R. R. 411 Morris, Illinois December 8, 1972
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6.6.C.l OF THE TECHNICAL SPECIFICATIONS.
Dear Mr. Giambusso:
This ~s to report a condition relating to the operation of the unit in which, on November 8, 1972, one electromatic relief valve failed to operate as required by Section 3. 5.D. L PROBLEM AND INVESTIGATION On November 8, 1972, the unit was operating in.a steady state condition at 738 MWe.
Prior to taking the High Pressure Coolant Injection (HPCI) System out of service for repairs, surveillance tests:.;iwere conducted on the Automatic Pressure Relief System, Core Spray System and the Isola-tion Condenser as required by the Technical Specifications (4.5.C.2).
During surveillance testing of the five electromatic relief valves, it was found that one valve "3A (serial no. BK 7051) would not operate.
Temper-atures downstream of the pilot valve in4icated that it was opening, but steam flow to the turbine indicated the main valve was not opening.
When it was found that the HPCI system and one electromatic relief valve were inoperable, an orderly shutdown was initiated.
As the unit was coming down, repa_irs were made to the HPCI system. After repairs were-made~ the system was satisfactorily tested.
The unit was subsequently brought back up in power and continued operation.
The weekly surveillance tests of the HPCI system were conducted while operating with the one inoperable valve.
This is required by the Technical Specifications (4.5.D.2).
Mr. A. Giambusso. ~~*
..:"-,:*~~
- December 8, 1972 On November 18, 1972, the unit was shutdown to_ investigate the
__ electromatic relief valve problem and perform other maintenance.
Disman-tling of the valve showed badly scored disc rings that were stuck in the valve guide.
The stuck rings in the guide caused the valve to malfunction.
The electromatic relief valve system is designed with one redundant valve.
Therefore, when one yalve.is inoperable the designed system capacity is still available.
Consequently, one inoperable valve presents no unrey_i~~d safety questions, and operation under those conditions is within the limitations of the Technical Specifications.
CORRECTIVE ACTION The disc wa~* ma~h~i~d and 'the seat and di..~c* l~pped., The valve guide and rings were replaced. - Pilo.t-valve" repairs included replacing the disc and stem and lapping the disc and.seat.
The valve was C>pera-tionally tested satisfactorily at 500 psig reactor pressure on November 22 while the reactor was heating up.
The remaining four valves will be inspected as soon as practical, and no later than the next refueling outage.
Sincerely,
~
W. P. Worden
- Superintendent WPW:do
"