[Federal Register Volume 60, Number 103 (Tuesday, May 30, 1995)]
[Notices]
[Pages 28178-28180]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-13103]



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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-424 and 50-425]


Georgia Power Company, et al; Vogtle Electric Generating Plant, 
Units 1 and 2; Environmental Assessment and Finding of No Significant 
Impact

    The U.S. Nuclear Regulatory Commission (the Commission) is 
considering issuance of an exemption from certain requirements of its 
regulations to Facility Operating License Nos. NPF-68 and NPF-84, 
issued to Georgia Power Company, et al. (the licensee) for operation of 
the Vogtle Electric Generating Plant (Vogtle), Units 1 and 2, located 
at the licensee's site in Burke County, Georgia.

Environmental Assessment

Identification of Proposed Action

    The proposed action would grant an exemption from certain 
requirements of 10 CFR 50.60, ``Acceptance Criteria for Fracture 
Prevention Measures for Light-Water Nuclear Power Reactors for Normal 
Operation,'' to allow application of an alternate methodology to 
determine the low temperature overpressure protection (LTOP) setpoint 
for Vogtle. The proposed alternate methodology is consistent with 
guidelines developed by the American Society of Mechanical Engineers 
(ASME) Working Group on Operating Plant Criteria (WGOPC) to define 
pressure limits during LTOP events that avoid certain unnecessary 
operational restrictions, provide adequate margins against failure of 
the reactor pressure vessel, and reduce the potential for unnecessary 
activation of pressure-relieving devices used for LTOP. These 
guidelines have been incorporated into Code Case N-514, ``Low 
Temperature Overpressure Protection,'' that has been approved by the 
ASME Code Committee. The content of this Code case has been 
incorporated into Appendix G of Section XI of the ASME Code and 
published in the 1993 Addenda to Section XI. The NRC staff is revising 
10 CFR 50.55a that will [[Page 28179]] endorse the 1993 Addenda and 
Appendix G of Section XI into the regulations.
    The philosophy used to develop Code Case N-514 guidelines is to 
ensure that the LTOP limits are still below the pressure/temperature 
(P/T) limits for normal operation, but allow the pressure that may 
occur with activation of pressure-relieving devices to exceed the P/T 
limits, provided acceptable margins are maintained during these events. 
This philosophy protects the pressure vessel from LTOP events, and 
still maintains the Technical Specification P/T limits applicable for 
normal heatup and cooldown in accordance with Appendix G to 10 CFR Part 
50 and Sections III and XI of the ASME Code.
    The proposed action is in accordance with the licensee's 
application for an exemption to 10 CFR 50.60 dated October 3, 1994, as 
supplemented by letter dated March 1, 1995.

The Need for the Proposed Action

    Section 50.60 states that all light-water nuclear power reactors 
must meet the fracture toughness and material surveillance program 
requirements for the reactor coolant pressure boundary as set forth in 
Appendices G and H to 10 CFR part 50. Appendix G to 10 CFR Part 50 
defines P/T limits during any condition of normal operation, including 
anticipated operational occurrences and system hydrostatic tests, to 
which the pressure boundary may be subjected over its service lifetime. 
Section 50.60(b) specifies that alternatives to the described 
requirements in Appendices G and H to 10 CFR part 50 may be used when 
an exemption is granted by the Commission under 10 CFR 50.12.
    To prevent transients that would produce pressure excursions 
exceeding the Appendix G P/T limits while the reactor is operating at 
low temperatures, the licensee installed an LTOP system. The LTOP 
system includes pressure relieving devices in the form of Power-
Operated Relief Valves (PORVs) that are set at a pressure low enough 
that if a transient occurred while the coolant temperature is below the 
LTOP enabling temperature, they would prevent the pressure in the 
reactor vessel from exceeding the Appendix G P/T limits. To prevent 
these PORVs from lifting as a result of normal operating pressure 
surges (e.g., reactor coolant pump starting, and shifting operating 
charging pumps) with the reactor coolant system in a water solid 
condition, the operating pressure must be maintained below the PORV 
setpoint.
    In addition, in order to prevent cavitation of a reactor coolant 
pump, the operator must maintain a differential pressure across the 
reactor coolant pump seals. Therefore, the licensee must operate the 
plant in a pressure window that is defined as the difference between 
the minimum required pressure to start a reactor coolant pump and the 
operating margin to prevent lifting of the PORVs due to normal 
operating pressure surges. The licensee's proposed LTOP analysis 
includes changes to account for the non-conservatism identified in 
Westinghouse Nuclear Safety Advisory Letter 93005A and Information 
Notice 93-58. The new analysis accounts for the static head due to 
elevation differences and the dynamic head effect of four reactor 
coolant pumps (RCP) operation. By including these factors and using the 
Appendix G safety margins, the licensee determined that the operating 
margin to the PORV setpoint would be depleted at approximately 
120 deg.F for Unit 1 and 145 deg.F for Unit 2. Therefore, operating 
with these limits could result in the lifting of the PORVs and 
cavitation of the RCPs during normal operation.
    The licensee proposed that in determining the PORV setpoint for 
LTOP events for Vogtle Units 1 and 2, the allowable pressure be 
determined using the safety margins developed in an alternate 
methodology, in lieu of the safety margins required by Appendix G to 10 
CFR Part 50. Designated Code Case N-514, the proposed alternate 
methodology is consistent with guidelines developed by the American 
Society of Mechanical Engineers (ASME) Working Group on Operating Plant 
Criteria to define pressure limits during LTOP events that avoid 
certain unnecessary operational restrictions, provide adequate margins 
against failure of the reactor pressure vessel, and reduce the 
potential for unnecessary activation of pressure-relieving devices used 
for LTOP. Code Case N-514, ``Low Temperature Overpressure Protection,'' 
has been approved by the ASME Code Committee. The content of his Code 
case has been incorporated into Appendix G of Section XI of the ASME 
Code and published in the 1993 Addenda to Section XI. The NRC staff is 
revising 10 CFR 50.55a, which will endorse the 1993 Addenda and 
Appendix G of Section XI into the regulations.
    An exemption from 10 CFR 50.60 is required to use the alternate 
methodology for calculating the maximum allowable pressure for the LTOP 
setpoint. By letter dated October 3, 1994, as supplemented by letter 
dated March 1, 1995, the licensee requested an exemption from 10 CFR 
50.60 for this purpose.
    In addition to requesting the exemption from 10 CFR 50.60, the 
licensee proposed an amendment to the Technical Specifications revising 
the LTOP analysis. The new analysis removes the non-conservatism as 
described previously. The amendment will be evaluated separate from 
this exemption request.
Environmental Impacts of the Proposed Action

    Appendix G of the ASME Code requires that the P/T limits be 
calculated: (a) Using a safety factor of 2 on the principal membrane 
(pressure) stresses, (b) assuming a flaw at the surface with a depth of 
one-quarter (\1/4\) of the vessel wall thickness and a length of six 
(6) times its depth, and (c) using a conservative fracture toughness 
curve that is based on the lower bound of static, dynamic, and crack 
arrest fracture toughness tests on material similar to the McGuire 
reactor vessel material.
    In determining the PORV setpoint for LTOP events, the licensee 
proposed to use safety margins based on an alternative methodology 
consistent with the proposed ASME Code Case N-514 guidelines. The ASME 
Code Case N-514 allows determination of the setpoint for LTOP events 
such that the maximum pressure in the vessel would not exceed 110% of 
the P/T limits of the existing ASME Appendix G requirements. This 
results in a safety factor of 1.8 on the principal membrame stresses. 
All other factors, including assumed flaw size and fracture toughness, 
remain the same. Although this methodology would reduce the safety 
factor on the principal membrane stresses, use of the proposed criteria 
will provide adequate margins of safety to the reactor vessel during 
LTOP transients and will satisfy the underlying purpose of 10 CFR 50.60 
for fracture toughness requirements.
    The change will not increase the probability or consequences of 
accidents, no changes are being made in the type of any effluents that 
may be released offsite, and there is no significant increase in the 
allowable individual or cumulative occupational radiation exposure. 
Accordingly, the Commission concludes that there are no significant 
radiological environmental impacts associated with the proposed action.
    With regard to potential non-radiological impacts, the proposed 
change involves use of more realistic safety margins for determining 
the PORV setpoint during LTOP events. It does not affect non-
radiological plant [[Page 28180]] effluents and has no other 
environmental impact. Therefore, the Commission concludes that there 
are no significant non-radiological environmental impacts associated 
with the proposed exemption.

Alternative to the Proposed Action

    Since the Commission has concluded there is no measurable 
environmental impact associated with the proposed action, any 
alternatives with equal or greater environmental impact need not be 
evaluated. As an alternative to the proposed action, the staff 
considered denial of the proposed action. 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 did not involve the use of any resources not previously 
considered in the Final Environmental Statement related to operation of 
the Vogtle Electric Generating Plant.

Agencies and Persons Consulted

    In accordance with its stated policy, on May 23, 1995, the staff 
consulted with the Georgia State official, Mr. James L. Setser of the 
Georgia Department of Natural Resources, regarding the environmental 
impact of the proposed action. The state official had no comments.

Finding of No Significant Impact

    Based upon 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 this action, see the licensee's 
letter dated October 3, 1994, as supplemented by letter dated March 1, 
1995, which are available for public inspection at the Commission's 
Public Document Room, 2120 L Street, NW., Washington, DC and at the 
local public document room located at the Burke County Library, 412 
Fourth Street, Waynesboro, Georgia 30830.

    Dated at Rockville, Maryland, this 22nd day of May 1995.

     For the Nuclear Regulatory Commission.
Herbert N. Berkow,
Director, Project Directorate II-2, Division of Reactor Projects--I/II 
Office of Nuclear Reactor Regulation.
[FR Doc. 95-13103 Filed 5-26-95; 8:45 am]
BILLING CODE 7590-01-M