[Federal Register: September 13, 1999 (Volume 64, Number 176)]
[Notices]               
[Page 49529-49530]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr13se99-122]                         

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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]
BILLING CODE 7590-01-P