[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]
-----------------------------------------------------------------------
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
[[Page 67556]]
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
[[Page 67557]]
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