GO2-89-144, Part 21 Rept Re Defect in Fault Tripping Design for Class 1E safety-related 480 Volt Divs 1 & 2 Ac Power Distribution Sys for Motor Control Ctrs.Caused by Improperly Designed Volt Electrical Distribution Sys.Circuit Breakers Replaced

Part 21 Rept Re Defect in Fault Tripping Design for Class 1E safety-related 480 Volt Divs 1 & 2 Ac Power Distribution Sys for Motor Control Ctrs.Caused by Improperly Designed Volt Electrical Distribution Sys.Circuit Breakers Replaced

ML20246F042
Person / Time
Site:	Columbia
Issue date:	08/21/1989
From:	Bouchey G WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	Murley T Office of Nuclear Reactor Regulation
References
REF-PT21-89, REF-PT21-89-132-000 GO2-89-144, PT21-89-132, PT21-89-132-000, NUDOCS 8908300133
Download: ML20246F042 (3)

Text

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n, WASHINGTON'PUBLIC POWER SUPPLY SYSTEM ^

P.0,' Box 968

• 3000 George 11'eshington \t'ay

• Richland,1%'ashington 99352 I'

August 21, 1989

'G02-89-144.

Dock'et No.~50-397 Mr. T. E. Murley,. Director .

Office of Nuclear ' Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. ~20555 Gentlemen: .

Subject:

.-NUCLEAR PLANT NO. 2 LICENSE NO. NPF-21 10CFR PART 21 REPORT lThis is a'10CFR Part'21 report submitted in accordance with the requirements of 10CFR Part 21 by' Mr. G. D. Bouchey, Director, Licensing & Assurance. The.

address of the Washington Public Power Supply System is:

~

Washington Public Power Supply System PO Box 968 3000 George Washington Way Richland,s Washington 99352 Que'stions ' concerning this report should be referred to ' Mr. W. S. Davison, Compliance Engineer, (509).377-2501 extension 2726. The verbal _ notification of Lthis.10CFR Part 21 was made on August 17, 1989 by Mr. C. M. Powers, WNP-2 Plant Manager. . . to - the office of Mr. Phil ' Johnson, Chief, . Reactor Projects, NRC Region V.

The basic component which contained the defect is .the fault tripping design for the' Class 1E Safety.Related 480 volt Division.1 and Division 2 AC Power Distri-bution System for Motor Control Centers MC-7A-A, MC-78-B, MC-78-A, MC-BA-A, and MC-8B-A. The specific portion of the design evaluated as deficient is the failur? to extend the depth of the coordination for the. WNP-2 AC. Electrical System protective tripping past the major 480 volt distribution centers- down to the subfed Motor Control Center level.

The ' power supply circuit breakers that feed the above listed 480 Volt Motor Control Centers do not have instantaneous overcurrent protection devices of sufficient range that they can be adjusted high enough to prevent the breakers from tripping as a result of a fault in a subfed branch circuit. The design would allow a fault in an individual load to cause the loss of the entire Motor Control Center. The lack of fault tripping coordination to prevent loss of an entire Motor Control Center from a single downstream fault is a defect.

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V L~ - Past Tw1 10CF.R PART 21 REPORT .l f b i

During a design basis accident, as a result of occurrences such as high energy line breaks or seismic activity, some or all of these Motor Control Centers l could be deenergized as a result of damage sustained to non-Class IE loads which they feed. This would present a common. mode failure mechanism which i

could allow multiple electrical equipment faults to potentially affect the operability of the following:

o Division 1 Emergency Diesel Generator o Division 2 Emergency Diesel Generator ,

o Standby Gas Treatment Fan 1A-1 o Standby Gas Treatment Fan IB-2 o Hydrogen Recombiner 1A o Low Pressure Coolant Injection Loop A o Low Pressure Coolant Injection Loop B o Low Pressure Coolant Injection Loop C o Low Pressure Core Spray System o Reactor Water Cleanup Containment Isolation o Reactor Closed Cooling Water Containment Isolation o Main Steam Leakage Control System o Residual Heat Removal Containment Spray System o Fuel Pool Cooling System The loss of some or all of the above components / systems could create a safety hazard in that failure to achieve safe shutdown of the reactor during accident conditions could result.

This 10CFR Part 21 reportable defect was discovered during the investigation of an equipment failure event which occurred on August 8, 1989. MT-H01-25, a permanently installed motor operated hoist located in the Rad Waste Building, shorted to ground. Simultaneous with blowing the load fuses, the entire Motor Control Center (MC-8A/2C) was automatically deenergized by the instantaneous overcurrent trip of the upstream power supply circuit breaker.

On August 9,1989 a cause investigation was initiated to evaluate the event.

This investigation resulted in the conclusion on August 11, 1989, that major portions of the safety related 480 volt electrical distribution system were not properly designed and that the above listed Class 1E Motor Control Centers were inoperable due to incorrect fault trip sequence coordination.

On August 15,1989, a 10CFR Part 21 deportability evaluation was completed and presented to the Plant Operating Committee (POC). Following the P0C recommen-dation, the Plant Manager concluded that this failure of a basic component was reportable per the requirements of 10 CFR Part 21.

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.% "',PagsThreeL H, 110CFR PART-21 REPORT.

The following corrective actions- have been or will. be taken as. indicated:

-1.. By E August 14, 1989, ~each; of the power.' supply circuit breakers -listed..

above had been ~ removed ' and: replaced. by jumper cables. of . equal . current :

carrying capacity with ' the exception of MC-88-A. The power supply.

circuit breaker-for this Motor Control Center.was, replaced with a fused disconnect in order to comply with the requirements of NRC Reg. Guide 1.63 for containment penetration.overcurrent protection.

2.. An engineering evaluation 'of the WNP-2 Class 1E 480' Volt Power Distri-

.bution' System will be performed to determine the necessity for further .

modifications to the . system . design. This evaluation will be completed

.by February: 28, 1990.

. Burns and Roe Company of 700 Kinderkamack Road, Oradell, New Jersey 07649, will' be informed by mail with a copy ~.of ~ this report and cover letter by August 30, 1989.

Very truly yours,

/

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G. D..Bouchey, Director Licensing & Assurance WSD/bk

-cc: JB Martin - NRC RV RB Samworth - NRC NS Reynolds - BCP&R DL Williams - BPA/399

~NRC Site Inspector - 901A