[Federal Register Volume 62, Number 48 (Wednesday, March 12, 1997)]
[Notices]
[Pages 11482-11483]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6342]


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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-313]


Entergy Operations, Inc.; Arkansas Nuclear One, Unit 1 
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 No. DPR-51, issued to Entergy 
Operations, Inc. (the licensee), for operation of Arkansas Nuclear One, 
Unit 1 (ANO-1), located in Pope County, Arkansas.

Environmental Assessment

Identification of the Proposed Action

    The proposed action would allow the licensee to utilize American 
Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code 
(Code) Case N-514, ``Low Temperature Overpressure Protection'' to 
determine its low temperature overpressure protection (LTOP) setpoints. 
By application dated November 26, 1996, the licensee requested an 
exemption from certain requirements of 10 CFR 50.60, ``Acceptance 
Criteria for Fracture Prevention Measures for Lightwater Nuclear Power 
Reactors for Normal Operation.'' The exemption would allow application 
of an alternate methodology to determine the LTOP setpoints for ANO-1. 
The proposed alternate methodology is consistent with guidelines 
developed by the 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.'' Code Case N-514 has been 
approved by the ASME Code Committee and incorporated into Appendix G of 
Section XI of the ASME Code and published in the 1993 Addenda to 
Section XI. However, 10 CFR 50.55a, ``Codes and Standards,'' and 
Regulatory Guide 1.147, ``Inservice Inspection Code Case 
Acceptability,'' have not been updated to reflect the acceptability of 
Code Case N-514.

The Need for the Proposed Action

    Pursuant to 10 CFR 50.60, all lightwater nuclear power reactors 
must meet the fracture toughness requirements for the reactor coolant 
pressure boundary as set forth in 10 CFR Part 50, Appendix G. 10 CFR 
Part 50, Appendix G, defines pressure/temperature (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. It is specified in 
10 CFR 50.60(b) that alternatives to the described requirements in 10 
CFR Part 50, Appendix G, may be used when an exemption is granted by 
the Commission under 10 CFR 50.12.
    To prevent transients that would produce excursions exceeding the 
10 CFR Part 50, Appendix G, P/T limits while the reactor is operating 
at low temperatures, the licensee installed the LTOP system. The LTOP 
system includes the electromatic relief valve (ERV) that is set to the 
LTOP mode when reactor pressure and temperature are reduced. The ERV 
prevents the pressure in the reactor vessel from exceeding the P/T 
limits of 10 CFR Part 50, Appendix G. However, to prevent ERV from 
lifting as a result of normal operating pressure surges, some margin is 
needed between the normal operating pressure and the ERV setpoint.
    To meet the 10 CFR Part 50, Appendix G P/T limits, the ERV would be 
set to open at a pressure very close to the normal pressure inside the 
reactor. With the ERV setpoint close to the normal operating pressure, 
minor pressure perturbations that typically occur in the reactor could 
cause the ERV to open periodically. This is undesirable from the safety 
perspective because after every ERV opening there is some concern that 
the ERV may not reclose. A stuck open ERV would continue to discharge 
primary coolant and reduce rector pressure until the discharge pathway 
was closed by operator action.
    Code Case N-514 would permit a slightly higher pressure inside the 
reactor during shutdown conditions. The ability to maintain a higher 
pressure in the reactor would allow a higher ERV setpoint and the 
likelihood for inadvertent opening of the ERV would be reduced.

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 two 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 ANO-1 
reactor vessel material.
    Code Case N-514 guidelines are intended to ensure that the LTOP 
limits are still below the pressure/temperature (P/T) limits for normal 
operation, but to 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 approach 
protects the pressure vessel from LTOP events, and maintains the 
Technical Specifications P/T limits applicable for normal heatup and 
cooldown in accordance with 10 CFR Part 50, Appendix G and Sections III 
and XI of the ASME Code.
    In determining the ERV setpoint for LTOP events, the licensee 
proposed the use of safety margins based on an alternate methodology 
consistent with the proposed ASME Code Case N-514 guidelines. ASME Code 
Case N-514 allows determination of the setpoint for LTOP events such 
that the maximum pressure in the vessel will not exceed 110% of the P/T 
limits of the existing ASME Appendix G. This results in a safety factor 
of 1.8 on the principal membrane 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.
    Use of Code Case N-514 safety margins will reduce operational 
challenges during low-pressure, low-temperature operations. In terms of 
overall safety, the safety benefits desired

[[Page 11483]]

from simplified operations and the reduced potential for undesirable 
opening of ERV will more than offset the reduction of the principal 
membrane safety factor. Reduced operational challenges will reduce the 
potential for undesirable impacts to the environment.
    The change 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 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 nonradiological impacts, the proposed 
action involves features located entirely within the restricted area as 
defined in 10 CFR Part 20. It does not affect nonradiological plant 
effluents and has no other environmental impact. Accordingly, the 
Commission concludes that there are no significant nonradiological 
environmental impacts associated with the proposed action.

Alternatives 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 does not involve the use of any resources not 
previously considered in the Final Environmental Statement for ANO-1.

Agencies and Persons Consulted

    In accordance with its stated policy, on January 28, 1996, the 
staff consulted with the Arkansas State official, Mr. David Snellings, 
Director of the Division of Radiation Control and Emergency Management, 
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 the proposed action, see the 
licensee's letter dated November 26, 1996, which is 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 Tomlinson Library, Arkansas Tech University, 
Russellville, AR 72801.

    Dated at Rockville, Maryland, this 7th day of March 1997.

    For the Nuclear Regulatory Commission.
George Kalman,
Senior Project Manager, Project Directorate VI-1, Division of Reactor 
Projects III/IV, Office of Nuclear Reactor Regulation.
[FR Doc. 97-6342 Filed 3-11-97; 8:45 am]
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