ML20135C741

Special Rept:On 970125,failure of 2A Edg.Caused by Train B Starting Air Control Valve Failed to Stroke & EDG Did Not Get Any Starting Air.Removed Plugs from All Other Sacvs

ML20135C741
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	02/24/1997
From:	Lacey W COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9703040254
Download: ML20135C741 (3)

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\ Commonwealth Edium Compan)

, Zion Generating Station 101 Shiloh Doulevard Zion.11. NM)99-2797 i Tel H 17 7 M 208 i i

1 February 24,1997 1

l U. S. Nuclear Regulatory Commission l

Document Control Desk  ;

Washington, DC 20555 1

Subject:

Valid Failure of the 2A Emergency Diesel Generator Zion Nuclear Power Station Unit 2 d

NRC Docket No. 50-304 '

l The enclosed Special Report from Zion Generating Station is being transmitted to you to report the valid failure of the 2A Emergency Diesel Generator (EDG) that occurred on l January 25,1997. Zion Station's Technical Specifications Surveillance Section 4.15.B.5 requires submittal of a special report within thirty days whenever a valid or invalid failure of l

an EDG occurs.

The following commitments are identified in this report:

1. The root cause of the SACV failures has been determined and the necessary corrective actions have been taken prior to returning the 2A EDG to service.

2. The applicable Station Maintenance procedures will be revised to ensure the plugs are j removed from the SACV's when they are installed. 1 Sincerely,

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/ Wm.fS. Lacey

,gG& /

1 i Station hian Zion Station WSL/jz /

Enclosure cc: NRC - Region III Administrator NRC - Zion Senior Resident Inspector Illinois Department of Nuclear Safety IDNS Resident Inspector ng,_ . Inpo Record Centeg  ;

9703040254 970224 PDR ADOCK 05000304 S PDR ZCoRRRA/sr97-Ol(3) . .

A t:nicom Lompany

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, l Enclosure Zion Station Special Report Zion Station Special Report No. 304-200-96-SCAQ-0415 This Special Report is submitted in accordance with Zion Technical Specifications Surveillance 4.15.B.5.

This Special Report describes a failure which has been determined to be valid per Regulatory Guide 1.108 section C.2.e.(2).

On January 25,1997, an attempt was made to start the 2A EDG to perform the full load rejection and hot restart surveillance tests (PT-11RI-DG2A). The start was perfonned with Train "A" of the starting air system out of sersice (completely vented) for corrective maintenance. The EDG failed to start. Investigation revealed that the Train "B" starting air control valve (SACV)

(2AOV-DG0136) failed to stroke and the EDG did not get any starting air, and therefore, did not rotate. The failure was determined to be a valid failure per Regulatory Guide 1.108 section C.2.e.(2).

After the failure, the equipment was quarantined and a troubleshooting plan developed.While conducting the troubleshooting plan, Engineering became concemed with e plug installed in the vent port of the S ACV. This vent port would allow the bottom chamber of th valve's piston to be vented (vendor drawing Z23-1-1, item #22). The instructions in all of the diuel documents do not disposition the proper configuration of the vent. Discussion with Cooper Energy Services has verified that this plug was for shipping purposes only and should be removed prior to use.

The concern about the vent plugs was substantiated by testing performed on the SACV in the shop. A regulated supply of air was provided to the top of the actuator piston. It was demonstrated that the rate of supply was more critical than pressure. Specifically, with the vent plug installed, if the pressure was supplied slowly, the valve would not stroke, even if the pressure were raised to 250 psig. With the vent plug removed, the valve stroked every time, regardless of how slowly pressure was supplied.

Field testing was performed in an attempt to duplicate the failure. The testing did verify that if a non-typical condition existed then the valve would fail with the plug installed but would pass if the plug was removed. A non-typical condition was simulated by installing a needle valve in the pilot air line to the SACV downstream of the starting air solenoid shuttle valve. When this valve was opened 1/8 turn, the restriction of the flow resulted in a failure of the SACV when the plug was installed; the valve operated successfully when the plug was removed. This test was repeated several times, each with the same results.

The plugs were removed or verified removed from all other SACVs.

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. Continued 5

l Root Cause Analysis:

l l Failure modes and effects analysis was used to guide and track a methodical review of all 1- credible failure modes.

1 l The cause of the valve failure was identified as an improper installation due to the lack of

removal of a shipping plug. This plug was in a vent path for the SACV. The root cause of the event was failure to remove the vent plugs.

1 Corrective Actions: l l

j 1. Removed the plugs from the vent ports of similar valws installed in the plant.

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i 2. Revise EDG maintenance procedures to require verification that this vent is free. '

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3. Zion Station netito the Cooper-Bessemer Owners Group about the need tt amove j the vent plug fron. installed SACVs.

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4. Cooper-Bessemer has revised the vendor drawing for the SACV to remove the vent plug.

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1 The 2A EDG was unavailable from 25 January,1997 at 1332 hours0.0154 days <br />0.37 hours <br />0.0022 weeks <br />5.06826e-4 months <br /> until February 20,1997 at j 0004 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. This was the sixth valid failure of the 2A EDG in the last 100 valid demands. The current 2A EDG surveillance test frequency will be in accordance with Zion Station Technical Specifications.

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