[Federal Register Volume 64, Number 84 (Monday, May 3, 1999)]
[Notices]
[Pages 23688-23689]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-11117]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-275 and 50-323]


Pacific Gas and Electric Company; Diablo Canyon Power Plant, 
Units 1 and 2; Environmental Assessment and Finding of No Significant 
Impact

    The U.S. Nuclear Regulatory Commission (the Commission) is 
considering the issuance of an exemption from certain requirements of 
its regulations for Facility Operating License Nos. DPR-80 and DPR-82 
that were issued to Pacific Gas and Electric Company (the licensee) for 
operation of the Diablo Canyon Power Plant (DCPP) Units 1 and 2, 
located in San Luis Obispo County, California.

Environmental Assessment

Identification of the Proposed Action

    The proposed action would exempt Pacific Gas and Electric Company 
(PG&E) from the requirements of 10 CFR 50.60 and 10 CFR Part 50, 
Appendix G, to allow use of the American Society of Mechanical 
Engineers (ASME) Code Case N-514 as an alternate method for 
establishing the setpoints for the low temperature overpressure 
protection (LTOP) systems that have been installed for overpressure 
protection of the DCPP reactor coolant pressure boundary.
    The proposed action is in accordance with the licensee's 
application for exemption dated September 3, 1998, as supplemented by 
letters dated January 22, February 5, and March 17, 1999.

The Need for the Proposed Action

    The provisions of 10 CFR 50.60 and 10 CFR Part 50, Appendix G, 
restrict the operating conditions for the DCPP reactor coolant systems 
from exceeding the pressure/temperature (P/T) limits established in 
compliance with Appendix G to Section XI of the ASME Boiler and 
Pressure Vessel Code. The requirements in 10 CFR Part 50 were 
established to protect the integrity of the reactor coolant pressure 
boundary in nuclear power plants. As part of these requirements, 10 CFR 
Part 50, Appendix G, requires that the P/T limits be established for 
reactor pressure vessels during normal and hydrostatic or leak rate 
testing conditions. Specifically, 10 CFR Part 50, Appendix G, states 
that ``The appropriate requirements on . . . the pressure-temperature 
limits and minimum permissible temperature must be met for all 
conditions.'' Pressurized water reactor licensees have installed cold 
overpressure mitigation systems(COMS)/low temperature overpressure 
protection systems (LTOP) in order to protect the reactor coolant 
pressure boundaries from being operated outside of the boundaries 
established by the P/T limit curves and to provide pressure relief of 
the reactor coolant pressure boundaries during low temperature 
overpressurization events. DCPP technical specifications require them 
to update and submit the changes to its LTOP setpoints whenever PG&E is 
requesting approval for amendments to the P/T limit curves. The use of 
Code Case N-514 would provide an acceptable level of safety against 
overpressurization events of the DCPP reactor pressure vessels. Based 
on the conservatism that is incorporated into the methods of Appendix G 
of the Section XI to the ASME Code for calculating P/T limit curves, it 
is concluded that permitting the LTOP setpoints to be established in 
accordance with the Code Case (e.g., at a level 110 percent 
of the limit defined by the P/T limit curves) would provide an adequate 
margin of safety against brittle fracture failure of the reactor 
pressure vessels. Therefore, the requirements of 10 CFR Part 50, 
Appendix G and Appendix G to Section XI of the ASME Code, are not 
necessary

[[Page 23689]]

to prevent brittle fracture of the reactor pressure vessel from 
occurring during low temperature operation.

Environmental Impacts of the Proposed Action

    The Commission has completed its evaluation of the proposed action 
and concludes that the use of Code Case N-514 as an alternative method 
for establishing the setpoints for the LTOP systems at DCPP Units 1 and 
2 would provide an adequate margin of safety against brittle fracture 
of the DCPP reactor vessels.
    The proposed action will not increase the probability or 
consequences of accidents, no changes are being made in the types of 
any effluents that may be released off site, and there is no 
significant increase in occupational or public radiation exposure. 
Therefore, there are no significant radiological environmental impacts 
associated with the proposed action.
    With regard to potential non-radiological impacts, the proposed 
action does not involve any historic sites. It does not affect non-
radiological plant effluents and has no other environmental impact. 
Therefore, there are no significant non-radiological environmental 
impacts associated with the proposed action.
    Accordingly, the Commission concludes that there are no significant 
environmental impacts associated with the proposed action.

Alternatives to the Proposed Action

    As an alternative to the proposed action, the staff considered 
denial of the proposed action (i.e., the ``no-action'' alternative). 
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 Diablo 
Canyon Power Plant dated May 1973, and the Addendum dated May 1976.

Agencies and Persons Consulted

    In accordance with its stated policy, on April 22, 1999, the staff 
consulted with the California State official, Mr. Steve Hsu of the 
Radiologic Health Branch of the State Department of Health Services, 
regarding the environmental impact of the proposed amendments. The 
State official had no comments.

Finding of No Significant Impact

    On the basis of the environmental assessment, the Commission 
concludes that the proposed amendments 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 application dated September 3, 1998, as supplemented dated 
January 22, February 5, and March 17, 1999, which are 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 California Polytechnic State University, 
Robert E. Kennedy Library, Government Documents and Maps Department, 
San Luis Obispo, California 93407.

    Dated at Rockville, Maryland, this 28th day of April 1999.

For the Nuclear Regulatory Commission.
Steven D. Bloom,
Project Manager, Section 2, Project Directorate IV & Decommissioning, 
Division of Licensing Project Management, Office of Nuclear Reactor 
Regulation.
[FR Doc. 99-11117 Filed 4-30-99; 8:45 am]
BILLING CODE 7590-01-P