[Federal Register Volume 59, Number 21 (Tuesday, February 1, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-2172]
[[Page Unknown]]
[Federal Register: February 1, 1994]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-295 and 50-304]
Commonwealth Edison Co.; Zion Nuclear 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 the requirements of 10 CFR
50.61(b)(2)(i) to Facility Operating License Nos. DPR-39 and DPR-48,
issued to Commonwealth Edison Company (the licensee), for operation of
the Zion Nuclear Power Station Units 1 and 2, located in Lake County,
Illinois.
Environmental Assessment
Identification of the Proposed Action
The proposed action would grant an exemption from the requirement
to determine the unirradiated reference temperature in accordance with
the requirements of 10 CFR 50.61(b)(2)(i). The licensee's request is
for an exemption that will allow it to determine the unirradiated
reference temperature using a method that is an alternative to the one
described in NB-2331 of Section III of the American Society of
Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code).
Without the exemption, the licensee would need to commit a significant
expenditure of resources to justify continued operation or prematurely
retire the units.
The exemption is in response to the licensee's application for
exemption dated December 3, 1993 as supplemented December 14, 1993.
Prior correspondence commenced with a letter from the licensee dated
December 13, 1991, that replied to the amendment to 10 CFR 50.61 which
was published in the Federal Register on May 15, 1991 (56 FR 22300). In
a letter dated March 13, 1992. the licensee provided its flux reduction
program to ensure the intermediate-to-lower shell circumferential weld
for Zion, Unit 1, would remain less than the screening criterion
through 32 EFPY. In a letter dated May 22, 1992, the licensee used data
provided by the Babcock and Wilcox Owner's Group (BAWOG) to address the
initial RTNDT and RTPTS for the Zion, Units 1 and 2, reactor
pressure vessels (RPVs). With this data, the licensee was able to show
that the RPVs will satisfy the pressurized thermal shock (PTS)
screening criteria through 32 EFPY. After reviewing the licensee's
submittals, the staff requested additional information in a letter
dated December 2, 1992. The licensee responded in a letter dated
January 28, 1993. On June 9, 1993, the staff met with the licensee to
discuss the performance of a modified analysis utilizing improved
analytical techniques. In a letter dated September 1, 1993, the
licensee provided a summary report demonstrating that the Zion RPVs
will not exceed the end-of-life PTS screening criteria. In another
letter dated October 5, 1993, the licensee detailed the development of
the methodology utilized in performing the PTS evaluation for the Zion
RPVs.
The Need for the Proposed Action
The proposed exemption is needed because 10 CFR 50.61(b)(2)(i)
requires that the unirradiated reference temperature be determined from
measurements as defined in the ASME Code, Section III, Paragraph 2331.
The PTS rule was amended on May 15, 1991. The amended rule changed the
method of calculating embrittlement to the method recommended in
Regulatory Guide (RG) 1.99, Revision 2, ``Radiation Embrittlement of
Reactor Vessel Materials,'' and required licensees to consider the
effect of reactor vessel operating temperature and surveillance results
on the calculated RTPTS value. Test results produced a wide
variability in unirradiated reference temperature, with a large
standard deviation and a higher than expected mean value. This large
uncertainty in unirradiated reference temperature may be due to the low
upper shelf behavior of the material. Hence, the definition of
unirradiated reference temperature in the ASME Code may not be
applicable for material with low upper shelf behavior such as that
found at Zion. The licensee has proposed to determine the unirradiated
reference temperature from drop weight and fracture toughness tests
instead of the method defined in Section III of the ASME Code. Since
the licensee has not followed the method in Section III of the ASME
Code, its method for determining the unirradiated reference temperature
of the weld material does not meet the requirements of 10 CFR 50.61 and
an exemption is required. If the proposed exemption were not granted,
the RPVs of Zion, Units 1 and 2, would exceed the screening criteria
for pressurized thermal shock prior to expiration of the operating
licenses. This would result in a significant expenditure of resources
to justify continued operation or the premature retirement of the
units.
Environmental Impacts of the Proposed Action
The Commission's staff has determined that granting the proposed
exemption would not significantly increase the potential for failure of
the reactor vessel. Although the licensee would not be determining the
unirradiated reference temperature of the weld material in accordance
with the requirements of 10 CFR 50.61, determining the unirradiated
reference temperature from drop weight and fracture toughness tests
instead of the method defined in Section III of the ASME Code would
meet the intent of the Code to ensure that the RTPTS values for
all beltline materials are below the PTS screening criteria at
expiration of the Zion, Units 1 and 2, licenses. Consequently, the
probability of reactor vessel failure would not be increased, nor would
the post-accident radiological releases be greater than previously
determined. Nor would the proposed exemption otherwise affect
radiological plant effluents. Therefore, the Commission's staff
conclude that there are no significant radiological environmental
impacts associated with the proposed exemption.
With regard to potential non-radiological impacts, the proposed
exemption involves a change to surveillance and testing requirements.
It does not affect non-radiological plant effluents and has no other
environmental impact. Therefore, the Commission's staff concludes that
there are no significant non-radiological environmental impacts
associated with the proposed exemption.
Alternative to the Proposed Action
Since the Commission concluded that there are no significant
environmental impacts associated with the proposed action, any
alternatives would have either no or greater environmental impact.
The principal alternative would be to deny the requested exemption.
This would not reduce the environmental impacts attributed to the
facility and would not meet the intent of the rule to ensure that the
beltline materials of the RPVs of Zion, Units 1 and 2, will be below
the PTS screening criteria at the expiration of their licenses.
Alternative Use of Resources
This action does not involve the use of any resources not
previously considered in connection with the Nuclear Regulatory
Commission's Final Environmental Statement, dated December 1972,
related to the operation of the Zion Nuclear Power Station, Units 1 and
2.
Agencies and Persons Consulted
The staff consulted with the State of Illinois regarding the
environmental impact of the proposed action.
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 3, 1993, as supplemented December 14,
1993, which is available for public inspection at the Commission's
Public Document Room, the Gelman Building, 2120 L Street, NW.,
Washington, DC 20555, and at the Waukegan Public Library, 128 North
County Street, Waukegan, Illinois 60085.
Dated at Rockville, Maryland, this 24th day of January 1994.
For the Nuclear Regulatory Commission.
James E. Dyer,
Project Director, Project Directorate III-2, Division of Reactor
Projects--III/IV/V, Office of Nuclear Reactor Regulation.
[FR Doc. 94-2172 Filed 1-31-94; 8:45 am]
BILLING CODE 7590-01-M
