[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