[Federal Register Volume 67, Number 30 (Wednesday, February 13, 2002)]
[Notices]
[Pages 6757-6758]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-3507]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-387 and 50-388]


PPL Susquehanna, LLC, Allegheny Electric Cooperative, Inc., 
Susquehanna Steam Electric Station, Units 1 and 2; Exemption

1.0  Background

    PPL Susquehanna, LLC (PPL, the licensee), is the holder of Facility 
Operating License Nos. NPF-14 and NPF-22 which authorize operation of 
the Susquehanna Steam Electric Station, Units 1 and 2 (SSES-1 and 2). 
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 two boiling-water reactors located in 
Luzerne County in Pennsylvania.

2.0  Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR), part 50, 
Section 50.60(a), requires nuclear power reactors to meet the fracture 
toughness requirements set forth in 10 CFR part 50, Appendix G. 
Appendix G of 10 CFR part 50 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 ``[t]he 
appropriate requirements on * * * the pressure-temperature limits and 
minimum permissible temperature must be met for all conditions.'' 
Appendix G of 10 CFR part 50 specifies that the requirements for these 
limits are the American Society of Mechanical Engineers (ASME) Code, 
Section XI, Appendix G, limits.
    To address provisions of amendments to the technical specification 
(TS) P-T limits in the submittal dated July 17, 2001, as supplemented 
July 26 and October 15, 2001, the licensee requested, pursuant to 10 
CFR part 50, section 50.60(b), that the NRC staff exempt SSES-1 and 2, 
from application of specific requirements of 10 CFR part 50, section 
50.60(a), and Appendix G, and substitute use of ASME Code Case N-640 as 
the basis for establishing the P-T limit curves. Code Case N-640 
permits the use of an alternate reference fracture toughness 
(Klc fracture toughness curve instead of Kla 
fracture toughness curve) for reactor vessel materials in determining 
the P-T limits. Because use of the Klc fracture toughness 
curve results in the calculation of less conservative P-T limits than 
the methodology currently required by 10 CFR part 50, Appendix G, an 
exemption to apply the Code Case would be required by 10 CFR 50.60.
    The licensee proposed to revise the P-T limits for SSES-1 and 2, 
using the Klc fracture toughness curve, in lieu of the 
Kla fracture toughness curve, as the lower bound for 
fracture toughness.
    Use of the Klc curve in determining the lower bound 
fracture toughness in the development of P-T operating limit curves is 
more technically correct than the Kla curve because the rate 
of loading during a heatup or cooldown is slow and is more 
representative of a static condition than a dynamic condition. The 
Klc curve appropriately implements the use of static 
initiation fracture toughness behavior to evaluate the controlled 
heatup and cooldown process of a reactor vessel. The staff has required 
use of the initial conservatism of the Kla curve since 1974 
when the curve was codified. This initial conservatism was necessary 
due to the limited knowledge of RPV materials. Since 1974, additional 
knowledge has been gained about RPV materials, which demonstrates that 
the lower bound on fracture toughness provided by the Kla 
curve is well beyond the margin of safety required to protect the 
public health and safety from potential RPV failure. Additionally, P-T 
curves based on the Klc curve will enhance overall plant 
safety by opening the operating window, with the greatest safety 
benefit in the region of low-temperature operations.
    In summary, the ASME Section XI, Appendix G, procedure was 
conservatively developed based on the level of knowledge existing in 
1974 concerning RPV materials and the estimated effects of operation. 
Since 1974, the level of knowledge about these topics has been greatly 
expanded. The NRC staff concurs that this increased knowledge permits 
relaxation of the ASME Section XI, Appendix G requirements by applying 
the Klc fracture toughness, as permitted by Code Case N-640, 
while maintaining, pursuant to 10 CFR 50.12(a)(2)(ii), the underlying 
purpose of the ASME Code and the NRC regulations to ensure an 
acceptable margin of safety.

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 
include, but are not limited to, the following case:
     Pursuant to 10 CFR 50.12(a)(2)(ii), the circumstance that 
application of the regulation in the particular circumstances would not 
serve the underlying purpose of the rule or is not necessary to achieve 
the underlying purpose of the rule.
    The NRC staff accepts the licensee's determination that an 
exemption would be required to approve the use of Code Case N-640. The 
staff examined the licensee's rationale to support the exemption 
request and concurred that the use of the Code Case would meet the 
underlying intent of these regulations. Based upon a consideration of 
the conservatism that is explicitly incorporated into the methodologies 
of 10 CFR part 50, Appendix G; Appendix G of the Code; and Regulatory 
Guide 1.99, Revision 2, the staff concluded that application of Code 
Case N-640 as described would provide an adequate margin of safety 
against brittle failure of the RPV. Since strict compliance with the 
requirements of 10 CFR 50.60(a) and 10 CFR part 50, Appendix G, is not 
necessary to serve the overall intent of the regulations, the NRC staff 
concludes that application of Code Case N-640 to the P-T limit curves 
meets the special circumstance provision of 10 CFR

[[Page 6758]]

50.12(a)(2)(ii). This is also consistent with the determination that 
the staff has reached for other licensees under similar conditions 
based on the same considerations. Therefore, the NRC staff concludes 
that requesting the exemption under the special circumstances of 10 CFR 
50.12(a)(2)(ii) is appropriate and that the methodology of Code Case N-
640 may be used to revise the P-T limits for SSES-1 and 2.

4.0  Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not present an undue 
risk to the public health and safety, and is consistent with the common 
defense and security. Also, special circumstances are present. 
Therefore, the Commission hereby grants PPL Susquehanna, LLC, an 
exemption from the requirements of 10 CFR part 50, section 50.60(a) and 
Appendix G, for generating the P-T limit curves for SSES-1 and 2.
    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 5322).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 7th 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. 02-3507 Filed 2-12-02; 8:45 am]
BILLING CODE 7590-01-P