[Federal Register Volume 60, Number 206 (Wednesday, October 25, 1995)]
[Notices]
[Pages 54710-54711]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-26420]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-280 and 50-281]
Virginia Electric and Power Company; Surry Power Station, 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. DPR-32 and DPR-37,
issued to Virginia Electric and Power Company, (the licensee), for
operation of the Surry Power Station, Units 1 and 2 located in Surry
County, Virginia.
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 the Surry Power Station, Units 1 and 2. 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 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 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 Need for the Proposed Action
Pursuant to 10 CFR 50.60, 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.
It is specified in 10 CFR 50.60(b) 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.
The reactor coolant system pressure/temperature operating window at
low temperatures is defined by the LTOP setpoint. Minimal operating
margin is available between the LTOP setpoint and the pressure
experienced at low temperatures due to the startup of a reactor coolant
pump, or as a result of normal operating pressure surges with the
reactor coolant system in a water solid condition. Implementation of a
LTOP setpoint that is valid from 15 EFPY to the end-of-license without
the additional margin allowed by ASME Code Case N-514 would restrict
the pressure/temperature operating window and would potentially result
in undesired PORV lifts. Therefore, the licensee proposed that in
determining the PORV setpoint for LTOP events for Surry, 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. By application dated June 8, 1995, the licensee
requested an exemption from 10 CFR 50.60.
Environmental Impacts of the Proposed Action
The Commission has completed its evaluation 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 Surry 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.
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 non-radiological impacts, the proposed
change involves use of a lower safety margin on fracture toughness for
[[Page 54711]]
determining the PORV setpoint during LTOP events; but reduces the
potential for activation of pressure relieving devices, thereby
improving plant safety. It does not affect non-radiological plant
effluents and has no other environmental impact. Therefore, the
Commission concludes that there are no significant non-radiological
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 the
Surry Power Station, Units 1 and 2.
Agencies and Persons Consulted
In accordance with its stated policy, on October 13, 1995, the
staff consulted with the Virginia State official, Mr. Foldesi of the
State Health Department, 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 June 8, 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 Swem Library, College of William and Mary,
Williamsburg, Virginia 23185.
Dated at Rockville, Maryland, this 18th day of October 1995.
For the Nuclear Regulatory Commission
David B. Matthews,
Director, Project Directorate II-1, Division of Reactor Projects--I/II,
Office of Nuclear Reactor Regulation.
[FR Doc. 95-26420 Filed 10-24-95; 8:45 am]
BILLING CODE 7590-01-P
