[Federal Register Volume 60, Number 27 (Thursday, February 9, 1995)]
[Notices]
[Pages 7804-7805]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-3366]
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NUCLEAR REGULATORY COMMISSION
Public Service Electric and Gas Company; Environmental Assessment
and Finding of No Significant Impact
[Docket Nos. 50-272 and 50-311]
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-70 and DPR-75,
issued to the Public Service Electric and Gas Company, PECO Energy
Company, Delmarva Power and Light Company, and Atlantic City Electric
Company, licensees for the Salem Nuclear Generating Station, Units 1
and 2. The plants are located at the licensee's site in Salem County,
New Jersey. The exemption was requested by the licensee by letter dated
December 22, 1994.
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 overpressure protection (LTOP) setpoint for the Salem
Nuclear Generating 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 Specifications 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.
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's current LTOP analysis, which
removes the non-conservatism in a previous analysis by assuming one
reactor coolant pump in operation, indicates that using the Appendix G
safety margin to determine the PORV setpoint would result in a new
pressure setpoint within the current operating window of Salem 1 and a
new setpoint just outside the current operating window of Salem 2. In
both cases, there would be no margin for normal operating pressure
surges. 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 Salem, 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 December 22, 1994, 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 Salem
reactor vessel material.
In determining the PORV setpoint for LTOP events, the licensee
proposed to [[Page 7805]] 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.
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 occupation radiation exposure.
Accordingly, the Commission concludes that this proposed action
would result in no significant radiological environmental impact.
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 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.
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 to 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
equivalent.
Alternative Use of Resources
This action did not involve the use of any resources not previously
considered in the Final Environmental Statements related to operation
of the Salem Nuclear Generating Station, dated April 1973.
Agencies and Persons Consulted
The NRC staff consulted with the state of Pennsylvania regarding
the environmental impact of the proposed action. The state official had
no comments.
Finding of No Significant Impact
The Commission has determined not to prepare an environmental
impact statement for the proposed exemption.
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.
For further details with respect to this action, see the request
for exemption dated December 22, 1994, 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 Salem Free Public Library, 112 West Broadway, Salem, New Jersey
08079.
Dated at Rockville, Maryland, this 7th day of February 1995.
For The Nuclear Regulatory Commission.
Chester Poslusny,
Acting Director, Project Directorate I-2, Division of Reactor
Projects--I/II, Office of Nuclear Reactor Regulation.
[FR Doc. 95-3366 Filed 2-8-95; 8:45 am]
BILLING CODE 7590-01-M
