[Federal Register Volume 67, Number 44 (Wednesday, March 6, 2002)]
[Notices]
[Pages 10235-10236]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-5273]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-285]


Omaha Public Power District Fort Calhoun Station Exemption

1.0 Background

    The Omaha Public Power District (OPPD/the licensee) is the holder 
of Facility Operating License No. DPR-40 which authorizes operation of 
the Fort Calhoun Station. The license provides, among other things, 
that the facility is subject to all rules, regulations, and orders of 
the U.S. Nuclear Regulatory Commission (NRC, the Commission) now or 
hereafter in effect.
    The facility consists of a pressurized-water reactor located in 
Washington County, Nebraska.

2.0 Purpose

    Title 10 of the Code of Federal Regulations (10 CFR) part 50, 
Appendix G, requires that pressure-temperature (P-T) limits be 
established for reactor pressure vessels (RPVs) during normal operating 
and hydrostatic or leak-rate testing conditions. Specifically, 10 CFR 
part 50, Appendix G, states that, ``The appropriate requirements on 
both the pressure-temperature limits and the minimum permissible 
temperature must be met for all conditions.'' In addition, 10 CFR part 
50, Appendix G, specifies that the requirements for these limits ``must 
be at least as conservative as the limits obtained by following the 
methods of analysis and the margins of safety of Appendix G of Section 
XI of the American Society of Mechanical Engineers Boiler and Pressure 
Vessel Code (ASME Code).'' The approved methods of analysis in Appendix 
G of Section XI require the use of KIa fracture toughness 
curve in the determination of the P-T limits.
    By letter dated December 14, 2001, OPPD submitted a license 
amendment request to update the P-T limit curves for the Fort Calhoun 
Station. By letter dated December 14, 2001, OPPD requested NRC approval 
for an exemption to use Code Case N-640 as an alternative method for 
complying with the fracture toughness requirements in 10 CFR part 50, 
Appendix G, for generating the P-T limit curves. Requests for such 
exemptions may be submitted pursuant to 10 CFR 50.60(b), which allows 
licensees to use alternatives to the requirements of 10 CFR part 50, 
Appendices G and H, if the Commission grants an exemption pursuant to 
10 CFR 50.12 to use the alternatives.

Code Case N-640 (formerly Code Case N-626)

    Code Case N-640 permits application of the lower bound static 
initiation fracture toughness value equation (KIc equation) 
as the basis for establishing the curves in lieu of using the lower 
bound crack arrest fracture toughness value equation (i.e., the 
KIa equation, which is based on conditions needed to arrest 
a dynamically propagating crack, and which is the method invoked by 
Appendix G to Section XI of the ASME Code). Use of the KIc 
equation in determining the lower bound fracture toughness in the 
development of the P-T operating limits curve is more technically 
correct than the use of the KIa equation since the rate of 
loading during a heatup or cooldown is slow and is more representative 
of a static condition than a dynamic condition. The KIc 
equation appropriately implements the use of the static initiation 
fracture toughness behavior to evaluate the controlled heatup and 
cooldown process of a reactor vessel. However, since use of Code Case 
N-640 constitutes an alternative to the requirements of Appendix G, 
licensees need staff approval to apply the code case methods to the P-T 
limit calculations.

3.0 Discussion

    Pursuant to 10 CFR 50.12, the Commission may, upon application by 
any interested person or upon its own initiative, grant exemptions from 
the requirements of 10 CFR part 50, when (1) the exemptions are 
authorized by law, will not present an undue risk to public health or 
safety, and are consistent with the common defense and security; and 
(2) when special circumstances are present. Special circumstances are 
present whenever, according to 10 CFR 50.12(a)(2)(ii), ``Application of 
the regulation in the particular circumstances would not serve the 
underlying purpose of the rule

[[Page 10236]]

or is not necessary to achieve the underlying purpose of the rule.''

Code Case N-640 (formerly Code Case N-626)

    OPPD has requested, pursuant to 10 CFR 50.60(b), an exemption to 
use ASME Code Case N-640 (previously designated as Code Case N-626) as 
the basis for establishing the P-T limit curves. Appendix G to 10 CFR 
part 50 has required use of the initial conservatism of the 
KIa equation since 1974 when the equation was codified. This 
initial conservatism was necessary due to the limited knowledge of RPV 
materials. Since 1974, the industry has gained additional knowledge 
about RPV materials, which demonstrates that the lower bound on 
fracture toughness provided by the KIc equation is well 
beyond the margin of safety required to protect the public health and 
safety from potential RPV failure. In addition, the RPV P-T operating 
window is defined by the P-T operating and test limit curves developed 
in accordance with the ASME Code, Section XI, Appendix G, procedure.
    The ASME Working Group on Operating Plant Criteria (WGOPC) has 
concluded that application of Code Case N-640 to plant P-T limits is 
still sufficient to ensure the structural integrity of RPVs during 
plant operations. The staff has concurred with ASME's determination. 
The staff has concluded that application of Code Case N-640 would not 
significantly reduce the safety margins required by 10 CFR part 50, 
Appendix G. The staff had concluded that application of Code Case N-640 
would provide that adequate safety margins are maintained such that the 
underlying purpose of 10 CFR part 50, Appendix G is met, pursuant to 10 
CFR 50.12(a)(2)(ii), for the Fort Calhoun Station RPV and reactor 
coolant pressure boundary (RCPB). Therefore, the staff concludes that 
Code Case N-640 is acceptable for application to the Fort Calhoun 
Station P-T limits.
    The staff has determined that OPPD has provided sufficient 
technical bases for using the methods of Code Case N-640 for the 
calculation of the P-T limits for the Fort Calhoun Station RCPB. The 
staff has also determined that application of Code Case N-640 to the P-
T limit calculations will continue to serve the purpose in 10 CFR part 
50, Appendix G, for protecting the structural integrity of the Fort 
Calhoun RPV and RCPB. In this case, since strict compliance with the 
requirements of 10 CFR part 50, Appendix G, is not necessary to serve 
the underlying purpose of the regulation, the staff concludes that 
application of Code Case N-640 to the P-T limit calculations meets the 
special circumstances provision stated in 10 CFR 50.12(a)(2)(ii), for 
granting this exemption to the regulation.

4.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not endanger life or 
property or common defense and security, and is, otherwise, in the 
public interest. Also, special circumstances are present. Therefore, 
the Commission hereby grants Omaha Public Power District an exemption 
from the requirements of 10 CFR part 50, Appendix G, for the Fort 
Calhoun Station.
    Pursuant to 10 CFR 51.32, the Commission has determined that the 
granting of this exemption will not have a significant effect on the 
quality of the human environment (67 FR 9008).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 28th day of February 2002.
    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 02-5273 Filed 3-5-02; 8:45 am]
BILLING CODE 7590-01-P