[Federal Register Volume 64, Number 59 (Monday, March 29, 1999)]
[Notices]
[Pages 14950-14951]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-7598]


-----------------------------------------------------------------------

NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-269, 50-270, and 50-287]


Duke Energy Corporation; Oconee Nuclear Station, Units 1, 2, and 
3 Environmental Assessment and Finding of No Significant Impact

    The U.S. Nuclear Regulatory Commission (the Commission) is 
considering issuance of an exemption from the requirements of Title 10 
of the Code of Federal Regulations (10 CFR) Part 50, Section 50.60 and 
Appendix G to the Duke Energy Corporation (the licensee) for operation 
of the Oconee Nuclear Station, Units 1, 2, and 3, located in Oconee 
County, South Carolina.

Environmental Assessment

Identification of the Proposed Action

    The proposed action would exempt the licensee from the provisions 
in 10 CFR Part 50, Section 50.60 and Appendix G. The NRC has 
established requirements in 10 CFR Part 50 to protect the integrity of 
the reactor coolant pressure boundary (RCPB) in nuclear power plants. 
As part of these requirements, 10 CFR Part 50, Appendix G requires that 
pressure-temperature (P-T) limits be established for reactor pressure 
vessels (RPVs) during normal operating and hydrostatic, or leak rate, 
testing conditions. Specifically, 10 CFR Part 50, Appendix G states 
that ``[t]he appropriate requirements on * * * the pressure-temperature 
limits and minimum permissible temperature must be met for all 
conditions.'' Pressurized water reactor licensees have installed cold 
overpressure mitigation systems/low temperature overpressure protection 
(LTOP) systems in order to protect the RCPBs from being operated 
outside of the boundaries established by the P-T limit curves and to 
provide pressure relief of the RCPBs during low temperature 
overpressurization events. The licensee is required by the Oconee Units 
1, 2, and 3 Technical Specifications (TSs) to update and submit the 
changes to its LTOP setpoints whenever the licensee is requesting 
approval for amendments to the P-T limit curves in the Oconee Units 1, 
2, and 3 TSs.
    As a result, to approve its amendments to the TS P-T limit curves, 
the licensee requested in its submittal dated October 15, 1998, that 
the staff exempt Oconee Units 1, 2, and 3 from the application of 
specific requirements of 10 CFR Part 50, Section 50.60 and Appendix G 
and substitute use of the American Society of Mechanical Engineers 
(ASME) Code Case N-514, ``Low Temperature Overpressure Protection 
Section XI, Division 1.'' This would permit setting the pressure 
setpoint of the facility's LTOP such that the P-T limits required by 10 
CFR Part 50, Appendix G could be exceeded by 10 percent during a low 
temperature pressure transient. The submittal was supplemented by 
letters dated December 15, 1998, and January 11 and 21, 1999.

The Need for the Proposed Action

    The licensee has noted in its submittal of October 15, 1998, that 
the underlying purpose of the regulations is to establish limits to 
protect the RPVs from brittle failure during low temperature operation 
and that the LTOP provides a physical means of protecting these limits. 
As a means of determining the LTOP enable temperature, the licensee 
proposed to use the ASME Code Case N-514 to permit setting the pressure 
setpoint of the facility's LTOP such that the P-T limits required by 10 
CFR Part 50, Appendix G could be exceeded by 10 percent during a low 
temperature pressure transient. The use of this Code

[[Page 14951]]

Case in lieu of 10 CFR Part 50, Appendix G requires approval of an 
exemption.
    The Reactor Coolant System P-T operating window at low temperatures 
is defined by the LTOP setpoint. Implementation of an LTOP setpoint 
without the additional margin of 10 percent allowed by ASME Code Case 
N-514 would restrict the P-T operating window and would potentially 
result in undesired actuation of the LTOP system. This constitutes an 
unnecessary burden that can be alleviated by the application of the 
Code Case and reduce the potential for an undesired lift of the LTOP 
valve.
    The licensee proposed that establishing the LTOP pressure setpoints 
in accordance with the provisions in Code Case N-514 would provide an 
acceptable level of safety against overpressurization events of the 
Oconee RPVs and that reactor vessel pressure would not exceed 110 
percent of the P-T limit allowables, which would still provide an 
acceptable level of safety and mitigate the potential for an 
inadvertent actuation of the LTOP. The Code Case dictates that when the 
LTOP system is enabled, the peak pressure resulting from an LTOP 
design-basis transient will not exceed 110 percent of the pressure 
limits established by the P-T limit curves for the plant, as required 
by 10 CFR Part 50, Appendix G, and by Appendix G to the Code. The Code 
Case also requires that the LTOP system be enabled at a temperature of 
200  deg.F, or at a temperature value equivalent to the sum of the 
limiting adjusted reference temperature (ART) + 50  deg.F, whichever is 
greater.
    The staff has previously found for several other nuclear power 
plants that Code Case N-514 provides an ``acceptable level of safety'' 
based on the amount of conservatism that has been explicitly 
incorporated into the methodologies for generating P-T limit curves, as 
prescribed in 10 CFR Part 50, Appendix G; Appendix G to the Code; and 
Regulatory Guide (RG) 1.99, Rev. 2. The conservatism includes: (1) a 
safety factor of 2 on the pressure stresses; (2) a margin factor 
applied to the calculation of ART values in accordance with the 
methodology of RG 1.99, Rev. 2; (3) an assumed 1/4 thickness flaw with 
a 6:1 aspect ratio; and (4) a limiting material toughness based on 
dynamic crack arrest data.
    The staff agrees that an exemption would be required to approve the 
use of Code Case N-514 in lieu of 10 CFR Part 50, Appendix G. The staff 
examined the licensee's rationale to support the exemption request and 
agrees that the use of Code Case N-514 would also meet the underlying 
intent of these regulations. Based upon a consideration of the 
conservatism that is explicitly incorporated into the methodologies of 
10 CFR Part 50, Appendix G; Appendix G of the Code; and RG 1.99, Rev. 
2, the staff concluded that permitting the LTOP setpoints to be 
established at the level specified in the Code Case (e.g., less than or 
equal to 110 percent of the limit defined by the P-T limit curves) 
would provide an adequate margin of safety against brittle failure of 
the RPVs. This is also consistent with the determination that the staff 
has reached for other licensees under similar conditions based on the 
same considerations.
    Therefore, the staff concludes that requesting the exemption under 
the special circumstances of 10 CFR 50.12(a)(2)(ii) is appropriate and 
that the methodology of Code Case N-514 may be used to establish the 
LTOP setpoints for the Oconee Units 1, 2, and 3 reactor coolant system.

Environmental Impacts of the Proposed Action

    The Commission has completed its evaluation of the proposed action 
and concludes that exemption from the requirements of 10 CFR Part 50, 
Section 50.60 and Appendix G, to permit the LTOP setpoints to be 
established in accordance with the Code Case (e.g., at a level less 
than or equal to 110 percent of the limit defined by the P-T limit 
curves), would provide an adequate margin of safety against brittle 
failure of the Oconee Units 1, 2, and 3 reactor vessels. The proposed 
action will not increase the probability or consequences of accidents, 
no changes are being made in the types of any effluents that may be 
released offsite, and there is no significant increase in occupational 
or public radiation exposure. Therefore, there are no significant 
radiological environmental impacts associated with the proposed action.
    With regard to potential nonradiological environmental impacts, the 
proposed action does not involve any historic sites. It does not affect 
nonradiological plant effluents and has no other environmental impacts. 
Therefore, there are no significant nonradiological impacts associated 
with the proposed action.
    Accordingly, the Commission concludes that there are no significant 
environmental impacts associated with the proposed action.

Alternatives to the Proposed Action

    As an alternative to the proposed action, the staff considered 
denial of the proposed action (i.e., the ``no-action'' alternative). 
Denial of the application would result in no change in current 
environmental impacts. The environmental impacts of the proposed action 
and the alternative action are similar.

Alternative Use of Resources

    This action does not involve the use of resources not previously 
considered in the ``Final Environmental Statement Related to the 
Operation of the Oconee Nuclear Station, Units 1, 2, and 3,'' dated 
March 1972.

Agencies and Persons Consulted

    In accordance with its stated policy, on February 24, 1999, the 
staff consulted with the South Carolina State official, Henry Porter of 
the Division of Radioactive Waste Management, Bureau of Land and Waste 
Management, Department of Health and Environmental Control, regarding 
the environmental impact of the proposed action. The State official had 
no comments.

Finding of No Significant Impact

    On the basis of the environmental assessment, the Commission 
concludes that the proposed action will not have a significant effect 
on the quality of the human environment. Accordingly, the Commission 
has determined not to prepare an environmental impact statement for the 
proposed action.
    For further details with respect to the proposed action, see the 
licensee's letter dated October 15, 1998, as supplemented December 15, 
1998, and January 11 and 21, 1999, which are available for public 
inspection at the Commission's Public Document Room, The Gelman 
Building, 2120 L Street, NW., Washington, DC, and at the local public 
document room located at the Oconee County Library, 501 West South 
Broad Street, Walhalla, South Carolina.

    Dated at Rockville, Maryland, this 24th day of March 1999.

    For the Nuclear Regulatory Commission.
Herbert N. Berkow,
Director, Project Directorate II-2, Division of Licensing Project 
Management, Office of Nuclear Reactor Regulation.
[FR Doc. 99-7598 Filed 3-26-99; 8:45 am]
BILLING CODE 7590-01-P