ML17201M203

Forwards SERs Accepting Proposed Mods to LPCI Swing Bus Automatic Transfer Scheme at Plants,Per 880219 Submittal. Util Requested to Provide Revised LOCA Analyses That Also Assumes Passive Failure of Electrical Power Supply

ML17201M203
Person / Time
Site:	Dresden, Quad Cities, 05000000
Issue date:	10/13/1988
From:	Ross T Office of Nuclear Reactor Regulation
To:	Bliss H COMMONWEALTH EDISON CO.
Shared Package
ML17201M204	List: ML17201M203 ML17201M205 ML17201M206
References
TAC-67046, TAC-67047, TAC-67048, TAC-67049, NUDOCS 8810260488
Download: ML17201M203 (7)

Text

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I UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 October 13, 1988 Docket Nos:

50-237, 249, 254 and 265 Mr. Henry E. Bliss Nuclear Licensing Manager CoRlllonwealth Edison Company P.O. Box 767 Chicago, IL 60609

SUBJECT:

EFFECT OF POSTULATED DC POWER FAILURE ON ECCS FUNCTIONALITY (TAC NOS. 67046, 67047, 67048, AND 67049)

Re:

Dresden Nuclear Power Station, Units 2 and 3, Quad Cities Nuclear Power Station, Units 1 and 2 By letter dated February 19, 1988 from J. A. Siladay to T. E. Murley, Convnonwealth Edison Company (CECo) provided detailed descriptions of, and implementation schedules for, a design mod1f1cat1on to the Low Pressure Coolant Injection (LPCI) swing bus automatic transfer scheme installed at Dresden (Units 2&3) and Quad Cities (Units 1&2).

CECo had detennined that both stations were vulnerable to a DC control power failure scenario similar to an event first identified and reported by the Enrico Fenn1 2 plant.

NRC staff reviewed the design *modifications and implementation schedules proposed by CECo for the LPCI swing bus.

We concluded that the proposed modifications will correct existing design deficiencies and are, therefore, acceptable.

Furthennore, we detennined that the proposed implementation dates are also acceptable. Our Safety Evaluation Report (SER) 1s provided in Enclosure 1.

In addition to correcting design deficiencies of the LPCI swing bus, CECo conducted several studies to confinn the design modifications. These studies involved the following:

1) breaker fault coordination of tne swing.bus,

2) impact of battery system (24/48V, and 125V, and 250V DC) failures on Emergency Core Cooling System (ECCS) availability, 3) failure modes and effects analysis of the modified swing bus automatic transfer design, and 4) comparison of the Enrico Fenni 2 swing bus design to Quad Cities and Dresden.

CECo documented their commitments for conducting these additional studies in Appendix D of the February 19, 1988 letter. These studies have been submitted in letters dated May 13, 1988, June 21, 1988 and July 8, 1988 and are under review.. by the staff.* Acceptance of the design modifications is not contingent upon completion of this review.

However, we do expect to receive further infonnation from CECo that will correlate the findfngs and conclusions of the battery system failure/ECCS availability study (of Quad Cities Unit 1) with the plant specific configurations of Quad Cities Unit 2 and Dresden Units 2&3.

This correlation should be provided on a timely basis, but no later than the implementation schedule for modification of each unit.

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Henry As a separate, but inter-related issue, the NRC staff also completed an evaluation regarding the applicability of passive electrical failures (especially DC power supply failures) upon required analyses of ECCS performance during a Design Basis Accident (OBA).

From this evaluation, we determined that the loss of any one DC power supply must be included as one of the possible single failures in the analyses for the design basis Loss of Coolant Accident {LOCA) in order to establish compliance with the requirements of 10 CFR Part 50.46. Such an analysis had been provided for Quad Cities Unit 1 in the Cycle 10 Reload Report, and approved by NRC SER dated December 15, 1987.

But th1s report was subsequently withdrawn and replaced by CECo, in the aforementional February 19, 1988 letter, with an analysis that did not recognize passive electrical failures. Since then, we've determined that the replacement SAFER/GESTR LOCA Analysis Report, Revision 1 {dated January 1988), submitted for Quad Cities, Unit 1, does not acceptably address the consequences of single failures on the capability of ECCS during a OBA

{this determination also applies to the previous LOCA analyses for Quad Cities Unit 2 and Dresden 2&3).

Our SER 1s included as Enclosure 2 to th1s letter.

In conclu~ion, we request CECo to provide revised LOCA analyses that also assume a single passive failure of any electrical power supply {e.g. DC batteries) for the Dresden and Quad C1t1es stations. These revised analyses for each of the Dresden and Quad Cities units shall be submitted to us prior to startup from the next scheduled refueling outage for each respective unit.

Enclosure:

As stated cc: See next page

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Sincerely, A*~-£~*

Thierry ~

Project Manager Project Directorate III-2 Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation

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lrlenry E. Bliss October 18, 1988 As a separate, but inter-related issue, the NRC staff also completed an evaluation regarding the applicability of passive electrical failures (especially DC power supply failures) upon required analyses of ECCS performance during a Design Basis Accident (OBA).

From this evaluation, we determined that the loss of any one DC power supply must be included as one of the possibl~ s1ngle failures fn the analyses for the design basis Loss of Coolant Ac~~a~nt (LOCA) in order to establish compliance with the requirements of 10 CFR P~rt 50.46. Such an analysis had been provided for Quad Cities Unit 1 in the Cycle 10 Reload Report, and approved by NRC SER dated December 15, 1987.

But this report was subsequently withdrawn and replaced by CECo, in the ~forementional February 19, 1988 letter, with.an analysis that did not recognize passive ele~trfcal failures. Since then, *we've determined that

, the replacement SAFER/GESTR LOCA Analysis Report, Rev-1s1on

• 1 (dated January 19B8), submitted for Quad Cities, Un1t 1, does not acceptably address the consequences of single failures on the capability of ECCS during a DBA (this determination also-applies to the previous LOCA analyses for Quad Cities Unit 2 and Dresden 2&3).

Our SER is included as Enclosure 2 to this letter.

In conclusion, we request CECo to provide revised LOCA analyses that also assume a single passive failure of any electrical power supply (e.g. DC batteries) for the Dresden and Quad Cities stations. _These revised analyses for each of the Dresden and Quad Cities units shall be submitted to us prior to startup from the next scheduled refueling outage for each respective unit.

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Enclosure:

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hlenry The NRC staff has also completed an evaluation of the applicability.of DC power supply failures upon ECCS performance. Our SER is included as Enclosure 2.to this letter. In this SER, we detennined that the loss of a DC power supply must be included as one of the possible single failures in the analyses for design basis Loss of Coolant Accident (LOCA) in order to establish complia

• e with the requirements of 10 CFR Part 50.46. Such an analysis had been pr ided for Quad Cities Unit 1 in the Cycle 10 Reload Report, but was subsequent y withdrawn and replaced by CECo with an analysis that did not recognize assive electrical failures. Since then, we've detennined that the replaceme SAFER/GESTR LOCA Analysis Report, Revision 1 (dated January 1988), s mitted by the February 19, 1988 letter, for Quad Cities, Unit 1, does not ac ptably address the consequences of single failures on the capabi-11ty of CS during a design basis accident (this detennination also applies to the pr vious LOCA analyses for Quad Cities Unit 2 and Dresden 2&3).

In conclusion, we request CECo to provide revised LOCA analy es also that assume a single passive failure of any electrical power supply (e ** DC batteries) for the Dresden and Quad Cities stations. These revised alyses for each of the Dresden and Quad Cities units shall be submitted to prior to startup from the next scheduled refueling outage for each respe iVe unit.

Enclosure:

As stated cc:

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/88 Sincerely, Thierry oss, Project Manager Project Directorate III-2 Divisi n of Reactor Projects - III, IV V and Special Projects Offi e of Nuclear Reactor*Regulat1on

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Henry The NRC staff has also completed an evaluation of the appli bility of DC power supply failures upon analyses used to confirm the adequacy of ECCS cooling performance.

Our SER is included as Enclosure 2 to this etter. In this.SER,

.we determined that the loss of a DC power supply must be included as one of the possible single failures in the analyses for the desig basis Loss of Coolant Accident (LOCA).

Furthermore, these analyses must al take into consideration existing LPCI swing bus design deficiencies, until s h time as proposed modifications are implemented to correct identified esign flaws.

Since such analyses have not been submitted to us, the staff c ncludes that Quad Cities and Dresden stations may not be in full compliance with the requirements of 10 CFR 50.46. Similarly we've concluded that the SAFER/GESTR LOCA Analysis Report, Revision 1 (dated January 1988), submitt d by the February 19, 1988 letter, for Quad Cities, Unit 1, does not accep bly address the consequences associated with single failures of DC power su lies upon availability of ECCS (this conclusion also applies to comparable L A analyses for other Dresden and Quad Cities units). Consequently, CECo must stablish compliance with JO CFR 50.46 for both stations by performing documenting, and submitting to the NRC staff additional LOCA analyses t at address single failure of any DC battery with and without the LPCI swing bu design flaw, as applicable.

However, because the time period prior to completion of planned modifications is limited, CECo may choose to request a exemption from conducting those LOCA analyses of ECCS cooling performance wh* h include consideration of the LPCI swing bus design deficiency.

Within thirty days after receipt of t is letter, CECo is requested to submit a schedule for providing us with revis d LOCA analyses that assume single failure of any DC power supply for the Dres en and Quad Cities stations. These revised analyses will also account for the PC! swing bus design flaw, unless:

1) Corrective modifications are c plete (e.g. Quad Cities, Unit 2), or 2) CECo requests an exemption fr.om 10 CF 50.46 for analyzing ECCS performance capability without assuming the swing bus sign flaw exists.

Enclosure:

As stated cc:

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I t I 3/88 Sincerely, Thierry Ross, Project Manager Project Director III-2 Division of Reactor Projects -

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Mr. Henry E. Bliss ColTlllonwealth Edison Company cc:

Mr. Stephen E. Shelton Vice President Iowa-Illinois Gas and Electric Company P. 0. Box 4350 Davenport, Iowa 52808 Michael I. Miller, Esq.

Sidley and Austin One First National Plaza Chicago, Illinois 60603 Mr. Richard Bax Station Manager Quad Cities Nuclear Power Station 22710 206th Avenue North Cordova, Illinois 61242 Resident Inspector U. S. Nuclear Regulatory Commission 22712 206th Avenue North Cordova, Illinois 61242 Chainnan Rock Island County Board of Supervisors 1504 3rd Avenue Rock Island County Offfice Bldg.

Rock Isldnd, Illinois 61201 Mr. Michael E. Parker, Chief Division of Engineering Illinois Department of Nuclear Safety 1035 Outer Park Drive, Springfield, Illinois 62704 Regional Administrator, Region III U. S. Nuclear Regulatory Co1T111ission 799 Roosevelt Road, Bldg. #4 Glen Ellyn, Illinois 60137 Quad Cities Nuclear Power Station Units 1 and 2

' Mr. Henry E. Bliss C011111onwealth Edison Company cc:

Michael J. Miller, Esq.

Sidley and Austin One First National Plaza Chicago, Illinois 60603 Mr. J. Eenigenburg Plant Superintendent Dresden Nuclear Power Station Rural Route 11 Morris, Illinois 60450 U. S. Nuclear Regulatory ColTlllission Resident Inspectors Office Dresden Station Rura 1 Route #1 Morris, Illinois 60450 Chainnan

• soard of Supervisors of Grundy County Grundy County Courthouse Morris, Illinois 60450.

Regional Administrator Nuclear Regulatory Corrrnission, Region III 799 Roosevelt Road, Bldg. 14 Glen Ellyn, Illinois 60137 Mr. Michael E. Parker, Chief Division of Engineering Illinois Department of Nuclear Safety 1035 Outer Park Drive, 5th Floor Spri~gfield, Illinois 62704

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Dresden Nuclear Power Station Units 2 and 3

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