ML19270F674

Documents 790220 Conversation in Atlanta,Ga.Forwards Responses to Questions & Requests Changes in Draft Natl Pollution Discharge Elimination Sys Permit TN0024450 Prior to Public Notice

ML19270F674
Person / Time
Site:	Sequoyah
Issue date:	02/28/1979
From:	Moore H TENNESSEE VALLEY AUTHORITY
To:	Kaplan C ENVIRONMENTAL PROTECTION AGENCY
References
NUDOCS 7903070356
Download: ML19270F674 (4)

Text

NRC F ORM 366 U. S. NUCLE AR REGULATORY COMMISSivN (7 77)' '

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i

o l The cause of the initial event was mechanical failure of the air motor oilot solenoid Thb li l: J l valve. During subsequent testing, the air startinq valve was found to be_sti.ckinn i 7 l air motor pilot solenoid valve was replaced and the air startina valve was rebuilt. l l , l 3 l l The diesel was proved operable and work requests have been wri tten to perform lil4l lthe same maintenance on Unit 1 and Unit 2 diesel generators. I 80 7 8 9 ST S  % POWER OTHER ST ATUS dis O ' F DISCOVERY DESCRIPTION l1 l s l [H JQ l0 0l0j@lNA l p l@l Routine Test l ACTIVITY CONTENT RE L E ASE D OF HE LE ASE AMOUNT OF ACTIVITY LOCATION OF RELEASE l116l 8 9

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10 NA I 68 69 11Illlilll1112 80 5 J. Hoeller 309-654-2241, ext. 248 o NAME OF PREPARER PHONE:

1. LER NUMBER: LER/R0 79-05/03L-0

11. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit One IV. DOCKET NUMBER: 50-254 V. EVENT DESCRIPTION:

At 1:10 AM on January 23, 1979, while testing the Unit 1/2 Diesel Generator, the pilot solenoid valve to the air starting motors failed to operate. This prevented the air starting motors from disengaging; therefore, the diesel generator was immediately shutdown. Unit One was in the REFUEL mode, and Unit Two was operating in the RUN mode at 2240 MWt and 725 MWe. Work request 411-79 was written to replace the solenoid valve. By 3:50 AM that mar 71 9, th solenoid valve was replaced and the Unit 1/2 Diesel Generatar was test started satisfactorily.

At 10:00 AM the same day, the 'Jnit 1/2 Diesel Generator was taken out of service to perform a monthly inspection. A test start was attempted without success and resulted in a fail-to-start alarm. The fail-to-start relay was reset, and at 10:54 AM the Unit 1/2 Diesel Generator started properly. As a result of the fall-to-start, a program was initiated to increase the surveillance frequency rate of the Unit 1/2 Diesel Generator with personnel in attendance. The Unit 1/2 Diesel Generator was started successfully twice on January 24, and once each day through Jer,uary 29 No attempt was made to start the diesel on January 30. On January 31, while starting the Unit 1/2 Diesel Generator, it appeared that the air starting valve was not operating properly. The valve was manually tapped with subsequent air valve actuation and starting of the diesel.

With the diesel in operation and loaded to the bus, the air starting system was taken out of service to repair the valve.

With the valve replaced and the air starting system returned to service, a successful start was performed. On February 1, with the control switch in Auto, the Unit 1/2 Diesel Generator started satisfactorily upon loss of transformers 12 and 81.

Again on February 2, transformer 12 tripped initiating a successful auto start of the diesel.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

When the Unit 1/2 Diesel Generator air starting motors would not disengage from the diesel generator, the Unit 2 Diesel-Generator was started and operated until the Unit 1/2 Diesel Generator was returned to service and demonstrated to be ope ra b l e. Normal off-site power was available at the time.

At 10:16 AM, when the Unit 1/2 Diesel Generator failed to s ta rt , the Unit 2 Diesel Generator was already being run for an operators check. Normal off-site power was also available.

Since Unit 1/2 Diesel Generator was returned to service and

tested at 10: 54 AM, safe operation of the plant was not h i nde red. On January 31, when the air starting valve was found to be sticking, the air starting system was taken out of service while the diesel was still running and loaded to the bus. Thus, had it been necessary, the diesel generator would have supplied its designed loads as required. After the air starting system was placed back in service, proper starting of the Unit 1/2 Diesel Generator was demonstrated buy one immediate manual start and two auto starts as a result of two trips of transformer 12, one on February 1 and again on February 2, 1979 Vll. CAUSE:

The apparent cause of the initial event was mechanical failure of the air motor pilot solenoid valve. The problem is believed to have been leakage through the dump vent. This inhibited the air starting valve from actuating, thus preventing the air starting motors from disengaging from the diesel generator.

On January 31, the difficulty was due to a sticking air starting valve.

The air motor pilot solenoid valve is a Salem model number 812-6, globe type valve, and the air starting valve is a Salem model number 853-3 valve. Both valves were manufactured by the Graham White Sales Corporation.

Vill. CORRECTIVE ACTION:

Upon failure of the air motor pilot solenoid valve, the valve was replaced like for like and the diesel generator tested for correct operation. When the fail-to-start relay trip occurred, the relay was reset and the diesel successfully started. Each day after that up until January 30, the Unit 1/2 Diesel Generator was test started without any recurrent trips. On January 31, with the diesel in operation and loaded to the bus, the air starting valve was dismantled, cleaned, lubricated and reassembled with new 0-rings. A successful start of the diesel was made af ter reinstallation of the valve. Work requests were written to perform identical maintenance on the Unit 1 and Unit 2 Diesel Generator air starting valves.