05000369/LER-1981-009, Forwards LER 81-009/03L-0.Detailed Event Analysis Encl

Forwards LER 81-009/03L-0.Detailed Event Analysis Encl

ML20032B573
Person / Time
Site:	McGuire
Issue date:	03/05/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20032B574	List: 05000369/LER-1981-009, Forwards LER 81-009/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-009-03, /03L-0:on 810205,flow to Reactor Coolant Loops Was Momentarily Lost.Caused by Failure of Throttle Valve to Close Due to Loosening of Nut Holding Linkage to Valve Stem. Linkage Repositioned & Nut Tightened
References
NUDOCS 8111050676
Download: ML20032B573 (3)

LER-1981-009, Forwards LER 81-009/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981009R00 - NRC Website

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DUKE l'OWER COMMNYJ I>owEn Duit.nixo 422 SouTit Cucacu STHEET, CuAH1.oTTE, N. C. ana42 I no i p._g g g wi w au o. panaca.sa.

March 5, 1981 VtCE PRESaQtNT IC L E PwCN t; An t a 704 Sitau Paoouction 3 7 3-4c e 3 Mr. James P. O'Reilly, Director N

U. S. Nuclear Regulatory Commission g

D Region II

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$ (*H 101 Marietta Street, Suite 3100 N

Atlanta, Georgia 30303

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NMW Re: McGuire Nuclear Station Unit 1

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Docket No. 50-369 4'b7

Dear Mr. O'Reilly:

PJ ease find attached Reportable Occurrence Report R0-369/81-09. This report concerns the operability of a train of the RHR System due to e valve failure.

This incident was considered to be of no significance with respect to the health and safety of the public.

Very truly yours,

[

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/

William O. Parker, Jr.

RWO:scs l

Attachment cc: Ditector Mr. Bill Lavallee i

Office of Management and Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission P. O. Box 10412 Washington, D. C.

20555 Palo Alto, California 94303 [h5' I

8111050676 810305 PDR ADOCK 05000369 S

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MCGUIRE NUCLEAR STATION INCIDENT REPORT Report Number: R0-369/81-09 Report Date: February 25, 1981 Occurrence Date: February 5, 1981 Facility: McGuire Unit 1, Cornelius, North Carolir.a Identification of Occurrence: Throttle Valve 1-ND-14 Failed to Close, Causing a Loss of Flow to the Reactor Coolant Loops from Train 3 ND Pump.

Condition Prior to Occurrence:

Initial Fuel Loading, Mode 6.

Description of Occurrence:

On February 5, 1981 at 1601 hours0.0185 days <br />0.445 hours <br />0.00265 weeks <br />6.091805e-4 months <br />, throttle valve 1-ND-14 " Failed Closed" causing a momentary loss of flow to the reactor coolant loops.

Computer graphics also showed 1-ND-14 closed. The control room operator immediately positioned 1-ND-14 manual loader to 55% open but flow reading from gauges INDP5190 and 1NDP5191 in the control room remained at zero (0) GPM.

Flow was diverted through 1-ND-34 and 1-NI-173A to establish a 3000 GPM flow to the reactor coolant loops, bypassing heat exchanger 1-B.

This incident caused a degravad mode of operatien and was therefore reportable pursuant to Technical Specification 4.9.8.1.

Apparent Cause of Occurrence:

Valve 1-ND-14 can be placed in any desired position through a manual loader in the control room or from the Auxiliary Shutdown Panel. The amount of supply air allowed into the valve diaphragm is regulated in the " Valve Positioner" by the instrument air (3-15 lbs.).

The instrument air pressure is controlled by the manual loader.

The valve positioner is equipped with linkages attached to the valve stem which will cut off the supply air when the desired position is reached.

Because of excessive vibration during operation, the nut that holds the linkage to the valve stem came loose causing the two (2) parts to move out of their proper position. This in turn, caused the valve to close due to a continuous flow of supply air.

Analysis of Occurrence:

When throttle valve 1-ND-14 " Failed Closed", the Residual Heat Removal Train B loop became inoperable, although flow to the reactor coolant loops was immediately re-established by bypassing heat-exchanger 1-E.

The redundant loop of the RHR System (Train A) was also inoperable at that time (RN Train A was undergoing maintenance), so that there was no means of removing residual heat. However, since j

there is only new fuel in the core and the RHR System was not removing decay heat, there was no danger of overheating the fuel.

There are several means to open the

valve if necessary. This valve would never fail close during an accident because the valve is designed to fail open on loss of supply air.

The supply air to the valve is isolated and vented to the atmosphere where solenoid valve 1-NDSV-0140 is deenergized upon receipt of a Safety Injection (Ss) Sigaal causing the valve to fail open.

This incident did not affect any safe operation of the plant or safety of the public.

Corrective Action

The linkage of the valve positioner was repositioned and the nut that holds it to the valve stem was tightened.

Residual Heat Removal Train B Loop was restored at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> (3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after the incident) upon repairing valve 1-ND-- 14. The vibration effect on the valve positioner was investigated and reported to the manufacturer. Duke will review the manufacturer's recommendation concerning this problem.