ML20039C499
| ML20039C499 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/18/1981 |
| From: | Parker W DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8112290410 | |
| Download: ML20039C499 (2) | |
Text
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,i DUKE POWER CbbbhkVEy.
. y r *,'. : 1. i,; j7 g j Powra Unitnixo 402 SocTu Caracu Srazer. CHARwTTE, N. C. 28242 Sl DEC 24 AfD 54 WI L LI AM O. PA R K E R, J R.
/icr Pers.Crmt TEttpwoNC: Anta 704 set. e=oooce December 18, 1981 3 7 3- *c n O hQ r q G[?
Mr. James P. O'Reilly, Director Region II y
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Re: Oconee Nuclear Station
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Docket No. 50-270 x
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Dear Mr. O'Reilly:
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On October 14, 1981, the ocor.ee Unit 2 limitorque operntor on the PORV block.
valve, 2RC-4, was discovered broken. Although this event does not constitute' a reportable occurrence, this report is provided for your information.
i On October 14, 1981, Unit 2 was at cold shutdown when personnel servic'ing the 2B1 Reactor Coolant Pump noticed exposed gearing on the valve 2RC-4 operator. A portion of the operator housing was discovered lying on. top of the pressurizer insulation. The broken component w_is identified as the-limitorque operator on valve 2RC-4 (PORV block valve).
After the valve was repaired, unsuccessful attempts were made to cycle the valve. The valve would go to an intermediate position and stop. Inspection revealed that the operator was broken again.
Since the unit was at cold shutdown, this incident posed no danger to the
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health and safety of the public.
If personnel in the Control Room had tried to close valve 2RC-4 with the operator in the failed position, the operator internals would have been ejected from the opening left by the failed com-pensator spring housing, and the valve would have remained in the open position.
This would have prevented the isolation of valve 2RC-66 had it been necessery.
The RPS trip setpoint is below the setpoint of valve 2RC-66.
It was determined that the initial failure was caused by the improper settings of the limit switches. The second failure was caused by the method of cycling the valve. The valve was cycled from the breaker panel and overrode the 11mit switch settings in doing so, thus permitting the unit to drive the ccmpensator spring housing off of the operator.
Although melted, missing, and brittle wiring insulation was discovered in the operator housing, it was not possible to determine whether this was a cause or a symptom of the failure and subsequent repair attempt. The wiring has been temporarily repaired and the entire cable assembly will be replaced p P t
at the next outage.
l 8112290410 81121g gDRADOCK 05000270 oppKETAL CON'.
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Mr. Ja:aes P>O'Reilly, Director
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J Oecember 18,31981
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Pat,e 2
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y Va1xn 2RC-4 has bcea repaired, adjusted, tested, and is ready for service.
Valye IRC-4 wi1E be checked prior to the end of the current refueling outage.
'J Unit 3's control personnel have been instructed not to cycle valve 3RC-4 until the unit is~down for an outage so that the valve may be inspected to determine if it ds in'warking' order:or if it is in,need of adjustment.
Th14 operator is n'limitorque SB-00' There are only 3 of these operators on-hite. 1This'operaton is on Units.1, 2, and 3 valve RC-4.
m Valve RC-4 is a 3" Wcytinghouse.Model 3GM 88.
Due to an EPRI study done in 7s
}980, Westinghguse recommanded that the operators be modified.
Briefly this modification slowed the operator:aud increased its closing torque; also, the torque sw'itchJuas bypassed and the limit switch was adjusted to stop the valve wncn it was closed. This modification is the only change made to these oper-
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ators since they were originally installed. The investigation of this incident shas shown that the modification was.not a direct cause.
. s The bare wiring: encountered was taped up.
Attempts to successfully cycle the valve faijed. The val've was de-energized, and final adjustments were made to the limit switches for the desired cpening and closing. The valve was then successfully cycled from the Control Room. Valve 2RC-4 was confirmed operable.
Valve 3RC-4 will be 1 J for similar problems during the next available
-E outage. The wiring on
.ie IRC-4 cnd 3RC-4 operators will be inspected for melted, mis' sing, or brittle viring insulation.
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' Very truly yours, l
A) % (O. cw '
William O. Parker, J
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.cc : Director Records Center Office of Management & Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C. 20555 Atlanta, Georgia 30339 Mr. W. T. Orders i
NRC~ Resident Inspector Oconee Nuclear Station
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