[Federal Register Volume 79, Number 30 (Thursday, February 13, 2014)]
[Notices]
[Pages 8738-8740]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-03215]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-321 and 50-366; NRC-2008-0585]
Southern Nuclear Operating Company, Inc.; Edwin I. Hatch Nuclear
Plant, Units 1 and 2; Exemption
1.0 Background
The Southern Nuclear Operating Company, Inc. (SNC, the licensee) is
the holder of the Renewed Facility Operating License Nos. DPR-57 and
NPF-5 which authorize operation of the Edwin I. Hatch Nuclear Plant,
Units 1 and 2 (HNP). The licenses provide, among other things, that the
facility is subject to the rules, regulations, and orders of the U.S.
Nuclear Regulatory Commission (NRC) now or hereafter in effect.
The HNP facility consists of two boiling-water reactors located in
Appling County, Georgia.
2.0 Request/Action
Pursuant to Sec. 50.12 of Title 10 of the Code of Federal
Regulations (10 CFR), Specific Exemptions, SNC has, by letter dated
April 23, 2013, 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 Part 50, ``ECCS Evaluation Models,'' (Appendix K).
The SNC's letter of April 23, 2013, constitutes the licensee's
second request for an exemption from the above fuel cladding material
requirements in order to irradiate two GE14 Lead Test Assemblies (LTAs)
in the HNP. The LTAs include a limited number of fuel rods manufactured
with an advanced cladding alloy, known as Global Nuclear Fuel (GNF)
Ziron, which is outside of the cladding materials specified in the
regulations (i.e. zircaloy or ZIRLO\TM\). By letter dated November 7,
2008, the NRC approved an earlier SNC request for an exemption in order
to irradiate these two GE14 LTAs in the HNP Unit 2 reactor for cycles
21, 22 and 23. These two LTAs have now completed operation in cycles 21
and 22; however, SNC decided not to include them in the Unit 2 cycle 23
core loading in order to allow sufficient time to perform pool-side
inspections. Since the original exemption request applied only to the
operation of the LTAs in the Unit 2 reactor for cycles 21-23, SNC has
requested a second exemption in order to continue irradiation of the
LTAs in either of the HNP reactors for one or more additional cycles,
up to GNF's approved peak pellet exposure.
[[Page 8739]]
The regulation in 10 CFR 50.46 contains acceptance criteria for an
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.
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 the public health
and safety, and are consistent with the common defense and security;
and (2) when special circumstances are present. Under 10 CFR
50.12(a)(2), special circumstances include, among other things, when
application of the regulation in the particular circumstances 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, in either of the HNP reactors for one or more additional
cycles, up to GNF's approved peak pellet exposure. 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. In Section VI of its letter dated April
23, 2013, SNC provides a technical basis supporting the applicability
of the 50.46 Paragraph (b) fuel criteria to GNF-Ziron. Experimental
results from tests conducted on GNF-Ziron samples exposed to loss-of-
coolant accident (LOCA) conditions were provided by SNC. 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 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.
As discussed in the NRC Research Information Letter 0801,
``Technical Basis for Revision of Embrittlement Criteria in 10 CFR
50.46,'' ADAMS Accession No. ML081350225, based on an ongoing LOCA
research program at Argonne National Laboratory, 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
rate of energy release, hydrogen generation, 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,
as described in the application for exemption, 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 included in the
application. 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 letter dated April 23, 2013, 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. The staff notes that Section V of GNF's technical
basis document (Enclosure 2 of the April 23, 2013 application) states
that the GNF fuel rod thermal mechanical code PRIME03 is now being used
to assess fuel rod performance. The PRIME03 code, which accounts for
exposure-dependent fuel thermal conductivity, replaces the legacy
GESTRM fuel rod performance code. While not explicitly approved for
GNF-Ziron, the use of PRIME03 is consistent with the approved GNF
reload methodology and therefore acceptable.
Through the mechanical testing and a comparison of material
properties provided by SNC, the staff has 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 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 in either of the HNP reactors for one or more additional cycles,
up to GNF's approved peak pellet exposure.
[[Page 8740]]
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 ZIRLO\TM\ as specified by 10 CFR 50.46, and
Appendix K, into either of the HNP reactors for one or more additional
cycles, up to GNF's approved peak pellet exposure. 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 Ziron, even though the
evaluations discussed above show that the intent of the regulations is
met. Therefore, since the NRC staff finds that the underlying purpose
of 10 CFR 50.46 and Appendix K is achieved with the use of Ziron, 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 an exemption 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 in either of the HNP reactors for one or more additional
cycles, up to GNF's approved peak pellet exposure.
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 (79 FR 4983; January 30, 2014).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 4th day of February 2014.
For the Nuclear Regulatory Commission.
Michele G. Evans,
Director, Division of Operating Reactor Licensing, Office of Nuclear
Reactor Regulation.
[FR Doc. 2014-03215 Filed 2-12-14; 8:45 am]
BILLING CODE 7590-01-P