[Federal Register Volume 64, Number 185 (Friday, September 24, 1999)]
[Notices]
[Pages 51805-51806]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-24900]


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NUCLEAR REGULATORY COMMISSION


Duke Energy Corporation; (McGuire Nuclear Station, Units 1 and 
2); Exemption

[Docket Nos. 50-369 and 50-370]

I

    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.
    These facilities consist of two pressurized water reactors located 
at the licensee's site in Mecklenberg County, North Carolina.

II

    Title 10 of the Code of Federal Regulations (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 pressure boundary 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.

    The Commission may grant an exemption from the requirements of the 
regulations 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. Special circumstances are considered to be present under 
10 CFR 50.12(a)(2) where application of the regulation in the 
particular circumstances conflicts with other rules or requirements of 
the Commission or where application of the regulation would not serve 
the underlying purpose of the rule or is not necessary to achieve the 
underlying purpose of the rule.

III

    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 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 containment, 
these lines branch into various separate, individual lines before 
reaching the respective main steam 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 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 by local manual 
operation. These valves are required to be open by the Technical 
Specifications (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 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)

[[Page 51806]]

during plant operation would violate a TS requirement.
    Valves SA-1, SA-2, SA-77, and SA-78 can be manually closed, as 
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 time needed by operators to 
manually close SA-1, SA-2, SA-77, and SA-78 or their associated stop 
check valves SA-5 and SA-6, during an accident, has been factored into 
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). 
Specifically, the Commission 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 reliable means exist 
to isolate this type of line when isolation is 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 exemption will have no significant effect on the 
quality of the human environment (64 FR 50839).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 20th day of September 1999.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 99-24900 Filed 9-23-99; 8:45 am]
BILLING CODE 7590-01-P