ML20244D991

Forwards Response to Safety Sys Outage Mod Insp Significant Item 3,per 890403-07 Insp Request.Original Design Basis for Process Control Sys Separation & Isolation for Plant Described in WCAP-7913,per Compliance W/Ieee 279-1971

ML20244D991
Person / Time
Site:	North Anna
Issue date:	04/13/1989
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-206A, NUDOCS 8904240241
Download: ML20244D991 (7)

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4 VIRGINIA 13LECTRIC AND PowuR CourAwy RICIIMOND,YIHOINIA 20261 la ,

April 13, 1989

' W. H.CAMTWRIGHT Vacs Panassauf NectaAn .

U. S. Nuclear Regulatory Commission Serial No. 89-206A-Attn: . Document Control Desk N0/SEC-LIC:cag Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2

-SAFETY SYSTEM OUTAGE MODIFICATION INSPECTION SIGNIFICANT ITEM 3 In your letter of March 17, 1989, you characterized four findings of the Safety System Outage Modification Inspection (SS0MI) as " safety significant matters" which you requested that Virginia Electric and Power Company address in an expeditious manner. We provided our response to these items in our letter of Marc' 31,1989 (Serial No.89-206).

During a follow-up inspection conducted the week of April 3 through 7,1989, you requested further clarification of safety significant item 3. Enclosed as Attachment 1 is information which supplements our original response to this issue.

If your have further questions or require additional information, please contact us immediately.

Very truly yo rs,

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W. R. Cartwright Attachment 8904240241 890413 PDR ADOCK 05000338 PNU

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i cc: U.S. Nuclear Regulatory Commission 101 Marietta Street, N.W.

Suite.2900 Atlanta, GA 30323.

Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station l

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ATTACHMENT l'.

RESPONSE TO SSOMI SAFETY SIGNIFICANT ISSUE NO. 3 l

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Virginia Electric and Power Company 72-WTM-6391-b-1

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ITEM 3

- The inspection team identified that non-Class 1E pressure transmitters for the service water system were powered from a Class 1E vital power source, without proper isolation. Virginia Electric and Power Company was requested to justify or correct the specific service water instrumentation as well as evaluate other possible instances of improper isolation elsewhere in the facility.

RESPONSE

The original design bases for process control system separation and isolation for North Anna are described in WCAP-7913 " Process Instrumentation for Westinghouse Nuclear Steam Supply Systems" which documents North Anna's compliance with IEEE 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Systems." Both IEEE 279 and WCAP-7913 address the isolation requirements of the protection circuitry. No additional requirements were included in these documents to address indication circuits which did not directly or indirectly affect the protection signals. The above principles were inherent in the original design of the process control system and were accepted by the NRC in its Safety Evaluation Report (NUREG-0053) dated June 1976, including Supplements 1 and 4.

Virginia Electric and Power Company approved Specification NAS-1013, " Criteria Specification for Design and Identification of Electrical Cable Systems" on October 15, 1980, to provide an in-house guideline for maintaining the original separation and isolation criteria. Subsequently, on April 9,1987, Specification NAS-3012, " Criteria Specification for Design and Identification of i Electrical Cable Systems for North Anna Power Station Units 1 & 2," was approved

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to replace NAS-1013, to better reflect Virginia Electric and Power Company experience and industry practice. As described in Section A of NAS-3012, its purpose is to define both the past acceptable practices forming the plant's licensing base and to define those practices which have evolved since North Anna received its opt ating license.

One of the differences between NAS-1013 and NAS-3012 relating to isolation is that NAS-3012 introduced the term " Associated circuit." Associated circuits are dafined by NAS-3012 as "Non-Class 1E circuits that share power supplies, signal  !

sources,. enclosures, or raceways with Class 1E circuits and are not physically separated or electrically isolated from Class 1E circuits by acceptable >

separation distance, barriers or isolation devices." Section G of NAS-3012 identifies the separation requirements for associated circuits, which are the same as for safety system circuits, and states, " Associated circuit requirements remain until an associated circuit passes through an isolation device or it is specifically analyzed or tested demonstrating that the associated circuit cannot degrade the Class 1E circuit to an unacceptable level."

i The subject service water pressure transmitters do not perform any safety related function and their only purpose is non-safety related indication.

However, these circuits are powered by a Class 1E power source and therefore i must be considered as associated circuits and must meet the requirements of )

l NAS-3012 as stated above. The design of these new transmitters met the original design basis requirements of WCAP-7913, IEEE 279-1971 and NAS-1013, in that they did not directly interface with the protection system. However, the circuits did not meet the more stringent requirements of NAS-3012 (i.e., isolation devices, analysis or testing), which were applicable at the time.

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V After the NRC identified the discrepancy with the service water pressure l transmitters, Virginia Electric and Power Company initiated an immediate investigation to determine if other process instruments may have been similarly designed. Those designs most susceptible to containing such a discrepancy are the designs initiated after NAS-3012 was approved. Our imediate concerns were those designs being installed during the current 1989 outage, with subsequent close-out this year.

Based upon our initial review of the 1989 outage design changes, Virginia Electric and Power Company considers the failure to adhere to the specification not to be a generic design deficiency, but rather a anique occurrence.

Furthermore, we believe the root cause of this occurrence to be attributable to NAS-3012's inability to properly distinguish between past and present practices relating to circuit isolation and inadequate training. Therefore, to correct this situation and to prevent future occurrences, we intend to ta.ke the following actions to address this issue:

1. Virginia Electric and Power Company will install qualified Class 1E isolators in the circuits of the subject service water pressure transmitters. These will be installed prior to each unit's restart.

l 2. To ensure no other new circuits have been similarly designed, we will review applicable design change packages (DCP's) and engineering work requests (EWR's) implemented since NAS-30'? was issued (April 1987).

This review will verify the proper isolation of these circuits and their adherence to the isolation design requirements of NAS-3012. The review will be conducted in two stages. For the first stage, the DCP's j and EWRs to be implemented during the current outage will be reviewed 72-WTM-6391-b-4

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and any' appropriate changes made prior-to the unit's restart.

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. . Secondly, the DCPs and EWRs implemented prior to this outage but after April' 1987, will be reviewed by November 1.1989.

3. NAS-3012 will:b'e revised to distinguish between the-isolation' requirements, of the original plant design and the ~ isolation requirements of new designs. This revision will'be issued by August 15, 1989.

4. Individuals. responsible' for implementing the requirenients of NAS-3012 will be trained on~the new revision discussed in Item 3 above, per the training requirements' of Section 7.4.3 of Standard EE-011, Rev. 3,

" Electrical Engineering Personnel Indoctrination and Training." This

-training wi_11 be completed by' September 15, 1989.

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