ML20059L439

Responds to Addl NRC Verbal Questions Received in Aug 1993 Re plant-specific Applicability of Technical Basis for NRC Approval of Indefinite Channel Bypass for B&W Plants,Per 921113 Application for Amend to License NPF-3

ML20059L439
Person / Time
Site:	Davis Besse
Issue date:	11/10/1993
From:	Storz L CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2183, NUDOCS 9311170070
Download: ML20059L439 (4)

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CENTERDOR l 4 . ENERGY i  :

300 Mod: son Avenue Louis F. Sforz j Toleco, OH 43652-0001 %ce President-Nuclear  !

419-249-2300 Davis-Besse {

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Docket Number 50-346  ;

i l-License Number NPF-3 t l.

j Serial Number 2183 '

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November 10, 1993 ,

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q a United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C. 20555 L

Subject:

License Amendment Request to Increase the Reactor  ;

i i Protection System (RPS) and Anticipatory Reactor Trip System (ARTS) Channel Functional Test Surveillance i

Interval and Channel Bypass Allowed-Out-of-Service Time l f

Gentlemen: ,

Y By letter dated November 13, 1992 (Serial Number 2081) Toledo Edison applied for an amendment to the Davis-Besse Nuclear Power  !

Station, Unit 1 (DBNPS), Operating License Number NPF-3, Appendix A Technical Specifications (TS). The proposed changes involve TS ,

3/4.3.1, " Reactor Protection System (RPS) Instrumentation," and TS j 3/4.3.2.3, " Anticipatory Reactor Trip System (ARTS)

Instrumentation." Additional information relating to this license i amendment request in response to NRC staff verbal questions was submitted by letter dated July 15, 1993 (Serial Number 2140).

The main purpose of the license amendment request is to extend RPS l and ARTS instrumentation TS testing intervals as permitted by tha )

NRC-approved Babcock and Vilcox (B&W) Topical Report, BAV-10167,

" Justification for Increasing the Reactor Trip System On-Line Test Intervals," and its supplements. A related change, also justified by BAV-10167 and its supplements, and approved generically by the NRC for implementation at B&W type plants, vould permit one inoperable RPS channel to be bypassed indefinitely instead of tripped as is currently required.

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Docket Number 50-346 License Number NFP-3 Serial Number 2183 Page 2 The NRC approved BAV-10167 and Supplement 1 to BAV-10167 by letter to the B&V Owners Group (BV0G) dated December 5, 1988. This original NRC staff evaluation did not accept continued operation for an indefinite period with one inoperable channel in bypass and proposed to limit the allovable out-of-service time (A0T) to 48 ,

hours. Because indefinite bypass had always been permitted by Technical Specifications for four of the six currently operating B&V type units, in November, 1989, the BV0G submitted BAV-10167, Supplement ? which provided additional justification for an indefinit 7T. On July 8, 1992, the NRC Staff issued a supplemen ,11 afety Evaluation Report (SER) for BAV-10167 which approved an .adefinite A0T for one inoperable channel in bypass.

NRC approval of indefinite bypass was based on additional information provided in BAV-10167, Supplement 2, information presented during an August 28, 1991 meeting, and information provided in a November 8, 1991 letter to the NRC from the BV0G.

The purpose of this letter is to respond to additional NRC staff verbal questions received in August 1993 regarding the plant specific applicability to the DBNPS of the technical basis for NRC generic approval of indefinite channel bypass for B&W plants.

Specifically, the NRC staff requested Toledo Edison to confirm that the RPS design as implemented at the DBNPS is consistent with the configuration described in the justification for indefinite channel bypass with regards to physical location of components, the capability of RPS to mitigate design basis accidents and transients with one RPS channel in bypass, and configuration of RPS power supplies.

The configuration of the DBNPS RPS conforms with that described in BAV-10167, its supplements and references. Physical and electrical separation and protection of redundant RPS channels and components are described in the Updated Safety Analysis Report (USAR) Sections 7.1.2, Identification of Safety Criteria; 7.2.1.1, Design Bases; 7.2.2.1, Compliance with IEEE Standard 279-1968; 8.3.1.1.7, Channels; 8.3.1.1.8, Physical Arrangement of the AC Electrical System Components; 8.3.1.2.14, Cables and Raceway Functions; 8.3.1.2.20, Routing of Class 1E Circuits; 8.3.1.2.25, Redundant Class IE Instruments; 8.3.1.2.26, Cable Spreading Room; 8.3.1.2.29, Penetrations; 3.6.2.7, Protection Against Dynamic and Environmental Effects outside the containment; 3.10.2.10, seismic Design of the Reactor Protection System; Appendix 3D.1.17, Criterion 21 - Protection System Reliability And Testability; Appendix 3D.1.18, Criterion 22 - Protection System Independence; Appendix 3D.I.19, Criterion 23 - Protection System Failure Modes; Appendix 3D.1.20, Criterion 24 - Separation of Protection and Control Systems; and 3D.1.25, Criterion 29 - Protection Against Anticipated Operational Occurrences.

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Docket Number 50-346 License Number NFP-3

' Serial Number 2183 Page 3 As discussed in these USAR sections, the RPS consists of four independent channels from sensor through trip actuating device.

Interchannel communications are minimized, except where necessary for coincidence logic. Where interchannel connections are necessary, isolation devices preclude propagation of failures between channels.

Reactor Protection System (RPS) components are seismically qualified and the RPS is protected from natural phenomena as described in the USAR. The RPS components are environmentally qualified to the extent necessary to perform their functions during events for which a RPS generated reactor trip is required. ,

i The RPS logic is housed in separate instrument cabinets for each channel in the control room. Outside the control room,  !

i channelized cabling to sensors in the field are routed in separate cable trays for each channel. Separate containment penetrations are provided for each channel. All sensors and sensing lines are independent for each channel with the exception of the reactor coolant flow sensing lines. However, the reactor coolant flow sensing lines and location of the associated differential pressure transmitters were required to be modified to meet the single failure criterion during the DBNPS first refueling outage by License Condition 2.C.(3).e. The modifications are described in Toledo Edison's letters to the NRC dated July 21, August 4, and August 25, 1980 (Serial Numbers 633, 640, and 646, respectively).

Nuclear Regulatory Commission acceptance of the modified design as i meeting the single failure criterion is documented in the NRC l Safety Evaluation for Amendment Number 33 to the DBNPS Operating License, NPF-3, dated October 1, 1980 (Log Number 615).

Each of the four RPS channels are povered from independent essential 120 VAC instrument busses. The four essential instrument busses are each povered from separate battery backed inverters and transformers. There are no power supply failure modes which can affect more than one RPS channel. The RPS is a j deenergize to actuate system. Lose of the essential 120 VAC 1 instrument bus supplying power to any RPS channel vill result in a channel trip regardless of whether the channel is bypassed or not.

Because the RPS is povered from battery-backed 120 VAC essential busses, the RPS does not rely on offsite power or on the emergency diesel generators (EDG) for power for any event for which a RPS trip is required. (Note that a loss of offsite power vould result in a reactor trip because of the loss of power for the reactor coolant pumps.) Thus, there is no relationship betveen the status of offsite power or the EDGs and whether an RPS channel is in bypass.

l Docket Number 50-346 i License Number NFP-3 I

' Serial Number 2183 i

Page 4 As summarized in USAR Sections 3D.1.17, 3D.1.18, and 3D.1.25, the channel independence provided in the RPS design results in there being no single failures, or events where a RPS trip is required, .

that can affect more than one RPS channel. Consequently, with one ('

channel in bypass, the remaining three RPS channels operating as a two-out-of-three system provide a reactor trip when required and tolerate a postulated single failure.

The BV0G November 8, 1991 submittal to the NRC and the NRC July 8, 1992 evaluation of indefinite bypass for B&V type plants, discussed the effect on the accident analysis of having one channel in bypass and single failure of a second channel. This condition could result in a loss of symmetry of process sensors.

The information presented by the BV0G described the primary and backup RPS trips for the events postulated for B&W type plants, and assessed the effect of loss of symmetry for these events. The information presented is directly applicable to the DBNPS. Based on this information, the NRC staff concluded that while the level of protection (including backup trips) might be somewhat degraded with a channel in bypass and a single failure of another channel, the conclusions of the accident analyses remain valid.

Based on the foregoing, Toledo Edison concludes the configuration of the DBNPS RPS conforms with that described in BAV-10167, its supplements and references. Therefore, generic acceptance by the NRC of an indefinite A0T with one RPS channel in bypass, is directly applicable to the DBNPS. Accordingly, Toledo Edison requests timely approval of the subject amendment request.

If you have any questions regarding these revisions, please contac. Mr. V. T. O'Connor, Jr., Manager - Regulatory Affairs at (419) 249-2366.

Very truly yours, c-

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/ l: lC: I

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PVS/amb cc: J. B. Hopkins, NRC/NRR DB-1 Senior Project Manager  ;

J. B. Martin, Regional Administrator, NRC Region III

- S. Stasek, NRC Region III, DB-1 Senior Resident Inspector J. R. Villiams, Chief of Staff, Ohio Emergency Management

! Agency, State of Ohio (NRC Liaison)

Utility Radiological Safety Board i

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