[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