ML20212D177

Exemption from Certain Requirements of 10CFR50,App A,General Design Criterion 57 Re Isolation of Main Steam Branch Lines Penetrating Containment

ML20212D177
Person / Time
Site:	Mcguire, McGuire
Issue date:	09/20/1999
From:	Zwolinski J NRC (Affiliation Not Assigned)
To:	DUKE POWER CO.
Shared Package
ML20212D171	List: ML20212D167 ML20212D177 ML20212D191
References
NUDOCS 9909230026
Download: ML20212D177 (5)

Text

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l 7590-01-P l

, 1 UNITED STATES OF AMERICA j NUCLEAR REGULATORY COMMISSION in the Matter of )

)

DUKE ENERGY CORPORATION ) Docket Nos. 50-369 and 50-370

)

(McGuire Nuclear Station, )

Units 1 and 2) )

EXEMPTION 1.

Duke Energy Corporation et al. (the licensee)is the holder of Facility Operating License Nos. NPF-9 and NPF-17, for the McGuire Nuclear Station (MNS), Units 1 and 2. The licenses provide, among other things, that the licensee is subject to all rules, regulations, and orders of the Commission now or hereafter in effect.

l I l These facilities consist of two pressurized water reactors located at the licensee'c site in )

i Mecklenberg County, North Carolina. ]

II. l l

Title 10 of the Code of Federal Reaulations (10 CFR) Part 50, Appendix A, specifies general design criteria for nuclear power plants. General Design Criterion (GDC) 57, regarding closed system isolation valves, states:

Each line that penetrates primary reactor containment and is neither part of the reactor coolant oressure bounriary nor connected directly to the containment atmosphere shall have at least one containment isolation valve which shall be either automatic, or locked closed, or capable of remote manual operation. This valve shall be outside containment and located as close to the containment as practical. A simple check valve may not be used as the automatic isolation valve. l 9909230026 990920 PDR ADOCK 05000369 P PDR a

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I 2-I The Commission may grant an exemption from the requirements of the regulations l

pursuant to 10 CFR 50.12 if the exemption is authorized by law, will not present an undue risk to the public health and safety, and is consistent with the common defense and security. The Commission will not consider granting an exemption unless special circumstances are present.

l Special circumstances are considered to be present under 10 CFR 50.12(a)(2) where f application of the regulation in the particular circumstances conflicts with other rules or requirements of the Commiss;cn or where application of the regulation would not serve the underlying puroose of the rule or is not necessary to achieve the underlying purpose of the rule. ,

Ill.

By letter dated April 20,1999, the licensee requested an exemption from GDC-57 for Containment Penetrations M261 and M393, which are main steam penetrations. These lines i

penetrate the containment and are not part of the reactor coolant pressure boundary, nor are they connected directly to the containment atmosphere. Outside of the conta!nment, these 1

j. lines branch into various separate, individual lines before reaching the respective main steam l isolation valves. From each of these main steam lines, one branch supplies main steam to the turbine-driven auxiliary feedwater (TDCA, using the licensee's abbreviation) pump.

Valves SA-1, SA 2, SA-77, and SA-78 are manual gate valves located in the interior l

Doghouse immediately downstream of the respective main steam piping,in the branch lines that supply main steam to the TDCA. These valves are locked open and can only be operated l

f by local manual operation. These valves are required to be open by the Technical Strar,ifications (TS) in order to supply steam to the TDCA, which is part of the engineered safety features. From a probabilistic risk assessment (PRA) perspective, the TDCA is one of the most risk-significant safety system components. Adding motor operators to valves SA-1, SA-2, SA-77, and SA-78, so that they become automatic or capable of remote operation (i.e., meeting

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_, GDC-57) would degrade the reliability of the TDCA to mitigate an accident because the motor operators would introduce a new failure mode. Keeping SA-1, SA-2. SA-77, and SA-78 closed (i.e., meeting GDC-57) during plant operation would violate a TS rer,Jirement.

Valves SA-1, SA-2, SA-77, and SA-78 can be manually closed, os needed during certain accidents, to isolate the steam lines they serve. if SA 1, SA-2, SA-77, and SA-78 are inaccessible due to post-accident environmental conditions, the associated stop check valves

. can be used to isolate these steam lines. The licensee stated that the amount of time needed by operators to isolate steam using SA-1, SA-2, SA 77, and SA-78, or their associated stop

! check valves SA-5 and SA-6, has been factored into the accident analyses and resultant dose calculations in the Updated Final Safety Analysis Report.

Thus, as stated in the staff's safety evaluation, modifying valves SA-1, SA-2, SA-77, and

SA-78 so that they can meet the operational requirement specified by GDC-57 would reduce the reliability of the TDCA and violate an existing TS. The une needed by operators to l manually close SA-1, SA-2, SA-77, and SA-78 or their associated stop check valves SA-5 and l

SA-6, during an accident, has been factored *nto . accident analyses. The applicable design-basis accident scenarios and consequences continue to be bounding. On such bases, the staff concludes that literal compliance with the operational aspect of GDC-57 is not desirable and the proposed exemption is acceptable.

IV.

Accordingly, the Commission has determined that special circumstances are present as defined in 10 CFR 50.12(a)(2)(ii). Specif:ca" 'ba Cere! *n finds that application of GDC-57 with respect to valves SA-1, SA-2, SA-77, and SA-78 conflicts with existing TS and is not necessary to achieve the underlying purpose of the rule. The underlying purpose of , -

GDC-57 is to ensure that reliaoie means exist to isolate this type of line when isolation is I

I a

r needed. As discustJ above, valves SA-1, SA-2, SA-77, and SA-78, or SA-5 and SA-6, can be manually closed to isolate their respective steam lines. Thus, the design of these valves and the existence of appropriate procedures for manually closing these valvea provide a reliable method of isolating the steam lines when needed. The Commission hereby grants the licensee an exemption from the requirement of 10 CFR Part 50, Appendix A, GDC-57. Specifically, this exempts the licensee from having to lock close valves SA-1, SA-2, SA-77, and SA-78 against TS requirements, or having to so modify them that they become automatic, or are capable of j l

remote manual operation.

Pursuant to 10 CFR 51.32, the Commission has determined that granting of this exemption will have no significant efit,ct on the quality of the human environment ( 64 FR 50839 ). )

i This exemption is effective upon issuance.

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FOR THE NUCLEAR REGULATORY COMMISSION Original signed by: I John A. Zwolinski, Director Division of Licensing Project Management Office of Nuclear Reactor Regulation Dated at Rockville, Maryland, this 20th day of September 1999.

To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" = Copy with attachment / enclosure "N" = No copy OFFICE PDil-1:PM _ lE LA:PDil-1 l6 SC:PDil-1 _ BC:SPLB _ _ _ _ lE D:PQil-A}? l NAME FRinaldi:cnW CHawes ('1014 REmch M d" JHannon&Tf"~~ HB'erkM)

DATE T / / /99 / 9/ l /99 7 / 2/99 7 /.L/99 M P4/99 __

OFFICE OGC gGA3 D:DLPM ,$fl NAME g Sa s <fy; 4 (JZwolinskih DATE 9 / f'/ 9'/ \,MM/ts /999 / / / / / /

F OFFICIAL RECORD COPY

+ .

needed. - As discussed above, valves SA-1, SA-2, SA-77, and SA-78, or SA-5 and SA-6, can be manually closed to isolate their respective steam lines. Thus, the design of these valves and the existence of appropriate procedures for manually closing these valves provide a reliable method of isolating the steam lines when needed. The Commission hereby grants the licensee an exemption from the requirement of 10 CFR Part 50, Appendix A, GDC-57. Specifically, this exempts the licensee from having to lock close valves SA-1, SA-2, SA-77, and SA-78 against TS requirements, or having to so modify them that they become automatic, or are capable of remote manual operation.

Pursuant to 10 CFR 51.32, the Commission has determined that granting of this l l l exemption will have no significant effect on the quality of the human environment (64 FR 50839 ).

! This exemption is effective upon issuance.

FOR THE NUCLEAR REGULAT RY COMMISSION i

4 John . Zwolinski, Director Divisio of Licensing Project Management Office Nuclear Reactor Regulation Dated at Rockville, Maryland, this 20th day of September 1999.

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