[Federal Register Volume 73, Number 221 (Friday, November 14, 2008)]
[Notices]
[Pages 67555-67557]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-27102]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-366]


Southern Nuclear Operating Company, Inc.; Edwin I. Hatch Nuclear 
Plant, Unit No. 2; Exemption

1.0 Background

    The Southern Nuclear Operating Company, Inc. (SNC, the licensee) is 
the holder of the Renewed Facility Operating License No. NPF-5 which 
authorizes operation of the Edwin I. Hatch Nuclear Plant, Unit No. 2 
(HNP-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 or the Commission) now or hereafter in 
effect.
    The facility consists of a boiling-water reactor located in Appling 
County in Georgia.

2.0 Request/Action

    Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), 
Section 50.12, ``Specific Exemptions'', SNC has, by letters dated March 
21, May 2, August 8 and September 22, 2008, requested an exemption from 
the fuel cladding material requirements in 10 CFR 50.46, ``Acceptance 
Criteria for Emergency Core Cooling Systems for Light-Water Nuclear 
Power Reactors,'' and Appendix K to 10 CFR part 50, ``ECCS Evaluation 
Models,'' (Appendix K). The regulation in 10 CFR 50.46 contains 
acceptance criteria for emergency core cooling system (ECCS) for 
reactors fueled with zircaloy or ZIRLO\TM\ cladding. In addition, 
Appendix K requires that the Baker-Just equation be used to predict the 
rates of energy release, hydrogen concentration, and cladding oxidation 
from the metal-water reaction. The exemption request relates solely to 
the specific types of cladding material specified in these regulations. 
As written, the regulations

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presume the use of zircaloy or ZIRLO\TM\ fuel rod cladding. Thus, an 
exemption from the requirements of 10 CFR 50.46, and Appendix K is 
needed to irradiate a lead test assembly (LTA) comprised of different 
cladding alloys at HNP-2.

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. Under Section 50.12(a)(2) 
of 10 CFR, special circumstances include, among other things, when 
application of the specific regulation in the particular circumstance 
would not serve, or is not necessary to achieve, the underlying purpose 
of the rule.

Authorized by Law

    This exemption would allow the licensee to insert two lead test 
fuel assemblies with fuel rod cladding that does not meet the 
definition of Zircaloy or ZIRLO\TM\ as specified by 10 CFR 50.46, and 
Appendix K, into the core of HNP-2, beginning with fuel cycle 21. As 
stated above, 10 CFR 50.12 allows the NRC to grant exemptions from the 
requirements of 10 CFR Part 50. The NRC staff has determined that 
granting of the licensee's proposed exemption will not result in a 
violation of the Atomic Energy Act of 1954, as amended, or the 
Commission's regulations. Therefore, the exemption is authorized by 
law.

No Undue Risk to Public Health and Safety

    In regard to the fuel mechanical design, the exemption request 
relates solely to the specific types of cladding material specified in 
the regulations. The underlying purpose of 10 CFR 50.46 is to establish 
acceptance criteria for ECCS performance. In Section VI of its letter 
dated May 2, 2008, SNC provides a technical basis supporting the 
continued applicability of the 50.46 Paragraph (b) fuel criteria to 
GNF-Ziron. Quench tests under a restrained load have been conducted on 
GNF-Ziron samples oxidized to various levels at elevated loss-of-
coolant accident (LOCA) temperatures. While these tests differ from the 
post-steam oxidized ring-compression testing (which forms the basis of 
the 50.46 post-quench ductility criteria), these results provide 
reasonable assurance that the 17 percent oxidation and 2200 degree 
Farenheit criteria are valid for GNF-Ziron and meet the underlying 
purpose of the rule, which is to maintain a degree of post-quench 
ductility in the fuel cladding material.
    Based on an ongoing LOCA research program at Argonne National 
Laboratory, as discussed in NRC Research Information Letter 0801, 
``Technical Basis for Revision of Embrittlement Criteria in 10 CFR 
50.46,'' ADAMS Accession No. ML081350225, cladding corrosion (and 
associated hydrogen pickup) has a significant impact on post-quench 
ductility. Post-irradiation examinations provided by the licensee 
demonstrate the favorable hydrogen pickup characteristics of GNF-Ziron 
as compared with standard zircaloy. Hence, the GNF-Ziron fuel rods 
would be less susceptible to the detrimental effects of hydrogen uptake 
during normal operation and their impact on post-quench ductility.
    Paragraph I.A.5 of Appendix K to 10 CFR Part 50 states that the 
rates of energy, hydrogen concentration, and cladding oxidation from 
the metal-water reaction shall be calculated using the Baker-Just 
equation. Since the Baker-Just equation presumes the use of zircaloy 
clad fuel, strict application of the rule would not permit use of the 
equation for the LTA cladding for determining acceptable fuel 
performance. Metal-water reaction tests performed by GNF on GNF-Ziron 
demonstrate conservative reaction rates relative to the Baker-Just 
equation. Thus, application of Appendix K, Paragraph I.A.5 is not 
necessary for the licensee to achieve its underlying purpose in these 
circumstances.
    High temperature perforation test results were provided. These test 
results illustrate similar burst characteristics of GNF-Ziron as 
compared with standard zircaloy. In addition, the licensee provides 
further comparisons of material properties between GNF-Ziron and 
zircaloy. Based upon this comparison of material properties, GNF and 
SNC believe that currently approved methods and models are directly 
applicable to GNF-Ziron. Based upon the material properties provided in 
SNC's letters dated May 2 and August 8, 2008, the NRC staff finds the 
use of current LOCA models and methods acceptable for the purpose of 
evaluating LTAs containing a limited number of GNF-Ziron fuel rods.
    In support of their exemption request, SNC submitted, with its 
letter dated August 8, 2008, a GNF document entitled, ``Impact of GNF-
Ziron Cladding on Thermal-Mechanical Licensing Limits''. This report 
provides an assessment of the potential impact of differences in 
material properties on the GSTR-M fuel thermal-mechanical methodology. 
While not directly related to the 50.46 exemption request, the NRC 
staff finds the conclusion of this report acceptable for the purpose of 
evaluating LTAs containing a limited number of GNF-Ziron fuel rods. 
Further NRC staff review may be necessary prior to batch application of 
GNF-Ziron fuel cladding material.
    Through mechanical testing and a comparison of material properties, 
SNC has provided reasonable assurance that anticipated in-reactor 
performance will be acceptable. Further, the licensee has demonstrated 
that the use of current methods and models are reasonable for 
evaluating the cladding's performance in response to anticipated 
operational occurrences and accidents. Nevertheless, as with any 
developmental cladding alloy, the NRC staff requires a limitation on 
the total number of fuel rods clad in a developmental alloy in order to 
ensure a minimal impact on the simulated progression and calculated 
consequences of postulated accidents. This limitation is directly 
related to the available material properties (both unirradiated and 
irradiated) used to judge the cladding alloy's anticipated in-reactor 
performance. Based on the material properties data presented within the 
application attachments, the NRC staff finds the HNP-2 LTA program 
acceptable with respect to achieving the underlying purpose of 10 CFR 
50.46 and Appendix K to 10 CFR part 50.
    Based upon results of metal-water reaction tests and mechanical 
testing which ensure the applicability of ECCS models and acceptance 
criteria, the limited number and anticipated performance of the 
advanced cladding fuel rods, and the use of approved LOCA models to 
ensure that the LTAs satisfy 10 CFR 50.46 acceptance criteria, the NRC 
staff finds it acceptable to grant an exemption from the requirements 
of 10 CFR 50.46 and Appendix K to 10 CFR part 50 for the use of two 
LTAs within HNP-2.

Consistent With Common Defense and Security

    The proposed exemption would allow the licensee to insert two lead 
test fuel assemblies with fuel rod cladding that does not meet the 
definition of Zircaloy or ZIRLOTM as specified by 10 CFR 
50.46, and Appendix K, into the core of HNP-2, beginning with fuel 
cycle 21. This change has no relation to security issues. Therefore, 
the common defense

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and security is not impacted by this exemption.

Special Circumstances

    Special circumstances, in accordance with 10 CFR 50.12, are present 
whenever application of the regulation in the particular circumstances 
is not necessary to achieve the underlying purpose of the rule. The 
underlying purpose of 10 CFR 50.46 and Appendix K to 10 CFR part 50 is 
to establish acceptance criteria for emergency core cooling system 
performance. The wording of the regulations in 10 CFR 50.46 and 
Appendix K is not directly applicable to these advanced cladding 
alloys, even though the evaluations discussed above show that the 
intent of the regulations is met. Therefore, since the underlying 
purpose of 10 CFR 50. 46 and Appendix K is achieved with the use of 
these advanced cladding alloys, the special circumstances required by 
10 CFR 50.12 for the granting of an exemption from 10 CFR 50.46 and 
Appendix K exist.

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 SNC exemptions from the 
requirements of 10 CFR 50.46, and 10 CFR Part 50, Appendix K, to allow 
the limited use of two LTAs with selected rods clad with GNF-Ziron 
cladding during fuel cycles 21 through 23 for the HNP-2 plant.
    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 (73 FR 65415; November 3, 2008).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 7th day of November 2008.

    For the Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
 [FR Doc. E8-27102 Filed 11-13-08; 8:45 am]
BILLING CODE 7590-01-P