[Federal Register: February 13, 2002 (Volume 67, Number 30)]
[Notices]
[Page 6757-6758]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr13fe02-140]
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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