[Federal Register Volume 64, Number 176 (Monday, September 13, 1999)]
[Notices]
[Pages 49529-49530]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-23693]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-361 and 50-362]
Southern California Edison Co., (San Onofre Nuclear Generating
Station, Units 2 and 3); Exemption
I
Southern California Edison Company (SCE, or the licensee) is the
holder of Facility Operating License Nos. NPF-10 and NPF-15, which
authorize operation of the San Onofre Nuclear Generating Station
(SONGS), Units 2 and 3. 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 San Diego County, California.
II
Regulatory requirements for the hydrogen control system are
specified in 10 CFR 50.44 and 10 CFR Part 50, Appendix A, (General
Design Criteria 41, 42, and 43). Different requirements apply to
facilities according to the date of publication of the Notice of
Hearing for the Construction Permit. With regard to hydrogen recombiner
and purge-repressurization system requirements, SONGS Units 2 and 3 are
subject to the requirements of 10 CFR 50.44(e) which states:
For facilities whose notice of hearing on the application for a
construction permit was published on or after November 5, 1970,
purging and/or repressurization shall not be the primary means for
controlling combustible gases following a LOCA [loss-of-coolant
accident]. However, the capability for controlled purging shall be
provided. For these facilities, the primary means for controlling
combustible gases following a LOCA shall consist of a combustible
gas control system, such as recombiners, that does not result in a
significant release from containment.
SONGS Units 2 and 3 are also subject to 10 CFR 50.44(d) which
states:
For facilities that are in compliance with [section] 50.46(b),
the amount of hydrogen contributed by core metal-water reaction
(percentage of fuel cladding that reacts with water), as a result of
degradation, but not total failure, of emergency core cooling
functioning shall be assumed either to be five times the total
amount of hydrogen calculated in demonstrating compliance with
[section] 50.46(b)(3), or to be the amount that would result from
reaction of all the metal in the outside surfaces of the cladding
cylinders surrounding the fuel (excluding the cladding surrounding
the plenum volume) to a depth of 0.00023 inch (0.0058 mm), whichever
amount is greater.
III
The licensee proposed to remove hydrogen control requirements from
the SONGS Units 2 and 3 design basis. The licensee stated that the
hydrogen control requirements in the SONGS design basis are not
required to provide assurance that the containment would not fail due
to combustible gas accumulation and ignition during accidents where
fission products would be present in the containment atmosphere. The
licensee also proposed to modify emergency operating instructions to
remove operator action requirements for monitoring and controlling
hydrogen concentration in containment.
The licensee's proposed removal of the hydrogen control
requirements from the SONGS Units 2 and 3 design basis requires an
exemption from certain requirements of 10 CFR 50.44(d) and (e). By its
letter dated September 10, 1998, as supplemented July 19, 1999, the
licensee submitted its exemption request.
IV
Section 50.12(a) of Title 10 of the Code of Federal Regulations
part 50 states that the Commission may, upon application by any
interested person or upon its own initiative, grant exemptions from the
requirements of the regulations of this part, which are (1) authorized
by law, will not present an undue risk to the public health and safety,
and are consistent with the common defense and security, and (2) the
Commission will not consider granting an exemption unless special
circumstances are present.
Section 50.12(a)(2)(ii) of 10 CFR part 50 states that special
circumstances are present when application of the regulation in the
particular circumstances would not serve the underlying purpose of the
rule or is not necessary to achieve the underlying purpose of the rule.
V
The staff has evaluated the licensee's analysis and documented its
evaluation in the enclosed safety evaluation. The staff's evaluation is
summarized below.
The underlying purpose of 10 CFR 50.44 is to ensure that following
a LOCA, an uncontrolled hydrogen-oxygen recombination would not take
place, or that the plant could withstand the consequences of
uncontrolled hydrogen-oxygen recombination without loss of safety
function. The licensee demonstrated that the plant could withstand the
consequences of uncontrolled hydrogen-oxygen recombination without loss
of safety function without credit for the hydrogen recombiners or the
hydrogen purge system for both the design-basis and the more limiting
severe accident with up to 75 percent metal-water reaction that remains
in-vessel scenario. Several risk studies, such as NUREG-1150, ``Severe
Accident Risk: An Assessment for Five U.S. Nuclear Plants,'' and those
performed by the licensee have shown that the relative importance of
hydrogen combustion for large, dry containments with respect to
containment failure to be quite low. The licensee also demonstrated
that hydrogen recombiners are insignificant from a large, dry
containment integrity perspective and the radiological consequences
remain unchanged with or without recombiners. Therefore, the
requirements for hydrogen recombiners and the backup hydrogen purge
capability for large, dry containments, such as SONGS Units 2 and 3,
are not necessary. Accordingly, the Commission has determined that
special circumstances are present as defined in 10 CFR 50.12(a)(2)(ii).
VI
The Commission has determined that, pursuant to 10 CFR 50.12, 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, and is otherwise in the public interest.
Therefore, the Commission hereby grants Southern California Edison
Company an exemption from the requirements of 10 CFR 50.44(d) and (e)
to remove hydrogen control requirements from the SONGS Units 2 and 3
design basis. The exemption also allows the licensee to modify its
emergency operating instructions to remove operator action requirements
for controlling hydrogen concentration in containment.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will have no significant effect on the
quality of the human environment (64 FR 48211).
[[Page 49530]]
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 3rd day of September 1999.
For The Nuclear Regulatory Commission.
Suzanne C. Black,
Acting Director, Division of Licensing Project Management, Office of
Nuclear Reactor Regulation.
[FR Doc. 99-23693 Filed 9-10-99; 8:45 am]
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