[Federal Register Volume 60, Number 38 (Monday, February 27, 1995)]
[Notices]
[Pages 10615-10617]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-4730]



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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-255]


Consumers Power Co. Palisades Plant; 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-20, issued to the 
Consumers Power Company, the licensee, for operation of the Palisades 
Nuclear Plant. The plant is located at the licensee's site in Van Buren 
County, Michigan.

Environmental Assessment

Identification of Proposed Action

    The proposed action requests 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 over-pressure protection (LTOP) setpoint for the Palisades 
Plant. 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,'' which 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 [[Page 10616]] Code and published in the 1993 
Addenda to Section XI.
    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 allows 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 request 
for exemption dated February 10, 1995.

The Need for the Proposed Action

    10 CFR 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. 
10 CFR 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 valves 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. Hence, 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 LTOP analysis indicates that 
using the Appendix G safety margins to determine the PORV setpoint 
would result in a pressure setpoing within its operating window, but 
there would be no margin for normal operating pressure surges. 
Therefore, operating with these limits could result in the lifting of 
the PORVs and cavitation of the reactor coolant pumps during normal 
operation. Therefore, the licensee proposed that in determining the 
PORV setpoint for LTOP events for Palisades, 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. The alternate methodology is consistent with ASME Code 
Case N-514. 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.
    An exemption from 10 CFR 50.60 is required to use the alternate 
methodology for calculating the maximum allowable pressure for LTOP 
considerations.

Environmental Impacts of the Proposed Action

    The Commission has completed its evaluation of the licensee's 
application. 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 of the vessel wall thickness and a length of 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 Palisades reactor vessel 
material.
    In determining the PORV setpoint for LTOP events, the licensee 
proposed to use safety margins based on an alternate 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. 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.
    Because adequate safety margins will be maintained, 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 this proposed action would result in no 
significant radiological environmental impact.
    With regard to potential nonradiological impacts, the proposed 
action involves use of more realistic safety margins for determining 
the PORV setpoint during LTOP events. 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 
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. The principal alternative would be to deny the proposed 
action. Denial of the exemption would not reduce environmental impacts 
associated with the facility.

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 Palisades Plant, dated June 1972, and its addendum dated February 
1978.

Agencies and Persons Consulted

    In accordance with its stated policy, the staff consulted with the 
Michigan State official regarding the environmental impact of the 
proposed action. The State official had no comments.

Finding of No Significant Impact

    Based upon the foregoing 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 [[Page 10617]] prepare an environmental impact 
statement for the proposed action.
    For further details with respect to this action, see the request 
for exemption dated February 10, 1995, which is 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 Van Wylen Library, Hope College, Holland, 
MI 49423.

    Dated at Rockville, Maryland, this 21st day of February, 1995.

    For the Nuclear Regulatory Commission.
John N. Hannon,
Director, Project Directorate III-1, Division of Reactor Projects--III/
IV, Office of Nuclear Reactor Regulation.
[FR Doc. 95-4730 Filed 2-24-95; 8:45 am]
BILLING CODE 7590-01-M