01-6981. Exelon Generation Company; Limerick Generating Station, Unit 2 Environmental Assessment and Finding of No Significant Impact

The U.S. Nuclear Regulatory Commission (NRC) is considering issuance of an exemption from certain requirements of Appendix G to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR Part 50) for Facility Operating License No. NPF-85, issued to Exelon Generation Company (Exelon or the licensee) for operation of the Limerick Generating Station, Unit 2 (Limerick Unit 2), located in Montgomery and Chester Counties in Pennsylvania.

Environmental Assessment

Identification of the Proposed Action

Appendix G to 10 CFR part 50, 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, Section IV.A.2.a, states, “The appropriate requirements on both the pressure-temperature limits and the minimum permissible temperature must be met for all conditions.” Appendix G of 10 CFR Part 50 specifies that the requirements for these limits are the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section XI, Appendix G, limits.

To address provisions of amendments to the technical specifications' P-T limits, the licensee requested in its submittal dated November 20, 2000, as supplemented December 20, 2000, that the Nuclear Regulatory Commission (NRC) staff exempt Limerick Unit 2 from application of specific requirements of Appendix G to 10 CFR part 50, and substitute use of ASME Code Case N-640. Code Case N-640 permits the use of an alternate reference fracture toughness (K_IC fracture toughness curve instead of K_ia fracture toughness curve) for reactor vessel materials in determining the P-T limits. Since the K_IC fracture toughness curve shown in ASME Code, Section XI, Appendix A, Figure A-2200-1 (the K_IC fracture toughness curve) provides greater allowable fracture toughness than the corresponding K_ia fracture toughness curve of ASME Code, Section XI, Appendix G, Figure G-2210-01 (the K_ia fracture toughness curve), using Code Case N-640 for establishing the P-T limits would be less conservative than the methodology currently endorsed by 10 CFR Part 50, Appendix G, and therefore, an exemption to Appendix G to apply the Code Case would be required.

The Need for the Proposed Action

ASME Code Case N-640 is needed to revise the method used to determine the reactor coolant system (RCS) P-T limits, since continued use of the present curves unnecessarily restricts the P-T operating window. Since the RCS P-T operating window is defined by the P-T operating and test limit curves developed in accordance with the ASME Code, Section XI, Appendix G, procedure, continued operation of Limerick Unit 2 with these P-T curves without the relief provided by ASME Code Case N-640 would unnecessarily require the licensee to maintain the RPV at a temperature exceeding 212 °F in a limited operating window during the pressure test. Consequently, steam vapor hazards would continue to be one of the safety concerns for personnel conducting inspections in primary containment. Implementation of the proposed P-T curves, as allowed by ASME Code Case N-640, would eliminate steam vapor hazards by allowing inspections in primary containment to be conducted at a lower coolant temperature.

Environmental Impacts of the Proposed Action

The proposed action would maintain an adequate margin of safety against brittle failure of the Limerick Unit 2 RPV.

The proposed action will not significantly 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 impacts, the proposed action does not involve any historic sites. It does not affect nonradiological plant effluents and has no other environmental impact. Therefore, there are no significant nonradiological impacts associated with the proposed action.

Accordingly, the NRC 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 any resources not previously considered in the Final Environmental Statement for the Limerick Generating Station, Unit 2, dated April 1984.

Agencies and Persons Consulted

In accordance with its stated policy, on January 19, 2001, the staff consulted with the Pennsylvania State official, David Ney of the Pennsylvania Department of Environmental Protection, regarding the environmental impact of the proposed action. The State official had no comments.

Findings of No Significant Impact

On the basis of the environmental assessment, the NRC concludes that the proposed action will not have a significant effect on the quality of the human environment. Accordingly, the NRC 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 November 20, 2000, as supplemented December 20, 2000. Documents may be examined, and/or copied for a fee, at the NRC's Public Document Room, located at One White Flint North, 11555 Rockville Pike (first floor) Rockville, Maryland. Publicly available records will be accessible electronically from the ADAMS Public Library component on the NRC Web site, http: // www.nrc.gov (the Electronic Reading Room).

Dated at Rockville, Maryland, this 15th day of March 2001.

For the Nuclear Regulatory Commission.

Christopher Gratton, Sr.,

Project Manager, Section 2, Project Directorate I, Division of Licensing Project Management, Office of Nuclear Reactor Regulation.