[Federal Register Volume 68, Number 150 (Tuesday, August 5, 2003)]
[Notices]
[Pages 46236-46237]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-19887]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-285]
Omaha Public Power District, Fort Calhoun Station, Unit 1;
Exemption
1.0 Background
The Omaha Public Power District (the licensee) is the holder of
Facility Operating License No. DPR-40 which authorizes operation of the
Fort Calhoun Station, Unit 1 (FCS). 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 in Nebraska.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR), part 50,
appendix G, which is invoked by 10 CFR 50.60, 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, appendix G to 10 CFR part 50 states that
``[t]he appropriate requirements on * * * the pressure-temperature
limits and minimum permissible temperature must be met for all
conditions,'' and ``[t]he pressure-temperature limits identified as
`ASME [American Society for Mechanical Engineers] Appendix G limits'* *
* require that the limits must be at least as conservative as limits
obtained by following the methods of analysis and the margins of safety
of Appendix G of Section XI of the ASME [Boiler and Pressure Vessel]
Code.'' Appendix G of 10 CFR part 50 also specifies that the Editions
and Addenda of the ASME Code which are incorporated by reference in 10
CFR 50.55a apply to the requirements in appendix G to 10 CFR part 50.
In the 2003 Edition of the Code of Federal Regulations, the NRC
endorsed Editions and Addenda of the ASME Code through the 1998 Edition
and 2000 Addenda. However, the licensee has currently incorporated the
1989 Edition of the ASME Code into the FCS licensing basis for defining
the ASME Code requirements which apply to the plant's ASME Code,
Section XI program. Hence, with respect to the statements from appendix
G to 10 CFR part 50 referenced above, it is the 1989 Edition of ASME
Code, Section XI, Appendix G, which continues to apply for FCS.
Finally, 10 CFR 50.60(b) states that,
[[Page 46237]]
``[p]roposed alternatives to the requirements in [Appendix G] of this
part or portions thereof may be used when an exemption is granted by
the Commission under [10 CFR 50.12].''
In the licensee's October 8, 2002, license amendment request to
implement a pressure-temperature limits report (PTLR) for FCS, the
licensee identified Topical Report Combustion Engineering (CE) NPSD-
683-A, Revision 6, as part of the PTLR methodology that would be cited
in the FCS Technical Specifications (TS). The NRC staff approved CE
NPSD-683-A, Revision 6, by letter dated March 16, 2001, with specified
limitations or additional licensee actions which are necessary to
support a licensee's adoption of CE NPSD-683-A, Revision 6. One of the
specified licensing actions stated that if a licensee proposed to
utilize the methodology in CE NPSD-683-A, Revision 6, for the
calculation of flaw stress intensity factors due to thermal stress
loadings (KIt), an exemption was required since the
methodology for the calculation of KIt values in CE NPSD-
683-A, Revision 6, could not be shown to be conservative with respect
to the methodology for the determination of KIt provided in
Editions and Addenda of ASME Code, Section XI, Appendix G, through the
1995 Edition and 1996 Addenda (the latest Edition and Addenda of the
ASME Code which had been incorporated into 10 CFR 50.55a at the time of
the staff's review of CE NPSD-683-A, Revision 6). Therefore, in
conjunction with the licensee's October 8, 2002, license amendment
request, the licensee also submitted an exemption request, consistent
with the requirements of 10 CFR 50.60, to apply the KIt
calculational methodology of CE NPSD-683-A, Revision 6, as part of the
FCS PTLR methodology.
During the NRC staff's review of CE NPSD-683-A, Revision 6, the
staff evaluated the KIt calculational methodology of CE
NPSD-683-A, Revision 6, versus the methodologies for KIt
calculation given in Appendix G to Section XI of the ASME Code. In the
staff's March 16, 2001, safety evaluation (SE), the staff noted, ``[i]n
the [CE methodology], the KIt is calculated using thermal
[stress] influence coefficients developed from 2-dimensional (2-D) FEM
[finite element] models with linear, quadratic, and cubic vessel
temperature profiles. These thermal influence coefficients are then
corrected for the 3-D elliptical crack geometry using the procedures of
Appendix A to Section XI of the ASME Code. Theoretically, using CE's
thermal influence coefficients is equivalent to using the [thermal]
stress influence coefficients of the current [1995 Edition through 1996
Addenda] Appendix G methodology....Thus, the alternative methodology in
[the CE NPSD-683-A, Revision 6] for calculating KIt factors
is similar to that in the most recent edition of Appendix G to the Code
endorsed by the NRC.'' In addition, work done by Mr. J. A. Keeney and
Mr. T. L. Dickson of Oak Ridge National Laboratory has demonstrated
that a 3-dimensional FEM approach gives thermal influence coefficients
that are very similar to those incorporated in the CE NPSD-683-A,
Revision 6, methodology. In summary, the staff concluded in its March
16, 2001, SE that the methodology in CE NPSD-683-A, Revision 6,
including that for the calculation of KIt, would lead to the
development of P-T limit curves which are only slightly non-
conservative with respect to those which would be calculated using the
1989 Edition of Appendix G to Section XI of the ASME Code (the Edition
of record for FCS). The staff stated in the SE that P-T limit curves
developed using the methodology of CE NPSD-683-A, Revision 6, are
adequate to protect the RPV against brittle fracture under all normal
operating and hydrostatic/leak test conditions and licensees applying
for PTLRs could apply the methods of CE NPSD-683-A, Revision 6, to the
P-T limit calculations provided an exemption to use the methodology
would be reviewed and granted by the staff in accordance with the
provisions of 10 CFR 50.60(b).
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, pursuant to 10 CFR 50.12(a)(2)(ii), are
present in that continued operation of FCS with P-T limit curves
developed in accordance with ASME Section XI, Appendix G without the
relief provided by utilizing the KIt calculational
methodology of CE NPSD-683-A, Revision 6, is not necessary to achieve
the underlying purpose of Appendix G to 10 CFR part 50. Application of
the KIt calculational methodology of CE NPSD-683-A, Revision
6, in lieu of the calculational methodology specified in ASME Code
Section XI, Appendix G, provides an acceptable alternative evaluational
procedure which will continue to meet the underlying purpose of
appendix G to 10 CFR part 50. The underlying purpose of the regulations
in appendix G to 10 CFR part 50 is to provide an acceptable margin of
safety against brittle failure of the RCS during any condition of
normal operation to which the pressure boundary may be subjected over
its service lifetime.
Based on the staff's March 16, 2001, SE regarding CE NPSD-683-A,
Revision 6, and the licensee's exemption request, the staff accepts the
licensee's determination that an exemption would be required to approve
the use of the KIt calculational methodology of CE NPSD-683-
A, Revision 6. The staff concludes that the application by FCS of the
technical provisions of the KIt calculational methodology of
CE NPSD-683-A, Revision 6, provide sufficient margin in the development
of RPV P-T limit curves such that the underlying purpose of the
regulations (appendix G to 10 CFR part 50) continues to be met.
Therefore, the NRC staff concludes that the exemption requested by the
licensee meets the special circumstances of 10 CFR 50(a)(2)(ii),
``[a]pplication 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,'' and is therefore
justified and may be granted.
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 Omaha Public Power District an
exemption from the requirements of 10 CFR part 50, appendix G, to allow
application of the KIt calculational methodology of CE NPSD-
683-A, Revision 6, in establishing PTLR methodology for FCS.
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 (68 FR 44110).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 30th day of July 2003.
For The Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. 03-19887 Filed 8-4-03; 8:45 am]
BILLING CODE 7590-01-P