Southern Nuclear Operating Company, Inc., 77677-77679 [2010-31173]

Agencies

• NUCLEAR REGULATORY COMMISSION

[Federal Register Volume 75, Number 238 (Monday, December 13, 2010)]
[Notices]
[Pages 77677-77679]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-31173]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-366; NRC-2010-0345]


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, the Commission) now or hereafter in effect.
    The facility consists of a boiling-water reactor located in Appling 
County in Georgia.

[[Page 77678]]

2.0 Request/Action

    Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), 
Section 50.12, ``Specific Exemptions'', SNC has, by letter dated May 
12, 2010 (the application), requested an exemption from the fuel 
cladding material requirements in 10 CFR 50.46, ``Acceptance Criteria 
for Emergency Core Cooling Systems [ECCS] for Light-Water Nuclear Power 
Reactors'', and Appendix K to 10 CFR 50, ``ECCS Evaluation Models,'' 
(Appendix K). The regulation in 10 CFR 50.46 contains acceptance 
criteria for 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 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 four (Global 
Nuclear Fuel (GNF)) GNF2 lead test fuel assemblies manufactured with a 
cladding material called GNF-Ziron, which is outside of the cladding 
materials specified in the regulations (i.e., zircaloy or ZIRLO\TM\) 
into the core of HNP-2, during fuel cycles 22, 23 and 24. This 
exemption is similar to a previous exemption regarding the use of GE14 
LTAs with a limited number of fuel rods clad in GNF-Ziron at HNP-2 that 
was issued on November 7, 2008. The differences are that if GNF2 fuel 
is being used, all rods will be clad in GNF-Ziron, and evaluations of 
the LTAs will be performed using the PRIME code methodology. 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 V of the 
application, SNC provides a technical basis supporting the continued 
applicability of the 10 CFR 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 
10 CFR 50.46 post-quench ductility criteria), these results provide 
reasonable assurance that the 17 percent oxidation and 2200 degree 
Fahrenheit 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,'' (Agencywide Documents Access and Management Systems (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 in Enclosure 6 of its 
application demonstrate the favorable hydrogen pickup characteristics 
of GNF-Ziron as compared with standard Zircaloy-2. 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 
(Figure B-15 of Enclosure 5) of the application 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 burst test results are provided in Figure B-6 
(Enclosure 5 of Reference 1). These test results illustrate similar 
burst characteristics of GNF-Ziron as compared with standard Zry-2. In 
addition, Enclosure 6 of Reference 1 provides further comparisons of 
material properties between GNF-Ziron and Zry-2. 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 References 1 and 2, the NRC 
staff finds the use of current LOCA models and methods acceptable for 
the purpose of evaluating LTAs containing GNF-Ziron fuel rods.
    In support of its exemption request, SNC submitted a GNF document 
entitled, ``GNF-Ziron Performance Benefits and Licensing Requirements 
Assessment'' (Enclosure 6 of the application). This report provides a 
logical assessment of the potential impact of differences in material 
properties on the PRIME fuel thermal-mechanical methodology. While not 
directly related to the 10 CFR 50.46 exemption request, the NRC staff 
finds the conclusion of this report acceptable for the purpose of 
evaluating LTAs containing GNF-Ziron fuel rods. Further NRC staff 
review may be necessary prior to use of PRIME for 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 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

[[Page 77679]]

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 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 four 
GNF2 LTAs within HNP-2.

Consistent with Common Defense and Security

    The proposed exemption would allow the licensee to insert four 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, during fuel cycles 22, 23 and 24. 
This change has no relation to security issues. Therefore, the common 
defense 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 four LTAs with GNF-Ziron cladding during fuel cycles 
22, 23 and 24 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 (75 FR 69137; November 10, 2010).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland this 3rd day of December 2010.

    For the Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
[FR Doc. 2010-31173 Filed 12-10-10; 8:45 am]
BILLING CODE 7590-01-P