[Federal Register Volume 74, Number 247 (Monday, December 28, 2009)]
[Notices]
[Pages 68639-68641]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-30674]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-361 and 50-362, NRC-2009-0570]
Southern California Edison: San Onofre Nuclear Generating
Station, Unit 2 and Unit 3 Temporary Exemption
1.0 Background
Southern California Edison (SCE, the licensee) is the holder of the
Facility Operating License Nos. NPF-10 and NPF-15, which authorize
operation of the San Onofre Nuclear Generating Station, Units 2 and 3
(SONGS 2 and 3), respectively. The licenses provide, among other
things, that the facility is subject to all rules, regulations, and
orders of the Nuclear Regulatory Commission (NRC or the Commission) now
or hereafter in effect.
The facility consists of two pressurized-water reactors (PWRs)
located in San Diego County, California.
2.0 Request/Action
Pursuant to Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.12, ``Specific exemptions,'' SCE has, by letter dated
January 30, 2009, as supplemented by letters dated March 16 and
September 29, 2009 (Agencywide Documents Access and Management System
(ADAMS) Accession Nos. ML090360738, ML090780251, and ML092740310,
respectively), requested a temporary exemption from 10 CFR 50.46,
``Acceptance criteria for emergency core cooling systems for light-
water nuclear power reactors,'' and Appendix K to 10 CFR 50, ``ECCS
[emergency core cooling system] Evaluation Models'' (Appendix K). The
regulation in 10 CFR 50.46 contains acceptance criteria for the ECCS
for light-water nuclear power reactors fueled with uranium oxide
pellets within cylindrical zircaloy or ZIRLOTM cladding. In
addition, Appendix K to 10 CFR Part 50 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 in
the development and application of an acceptable ECCS model. The
temporary exemption request relates solely to the specific types of
cladding material specified in these regulations. As written, the
regulations require the use of zircaloy or ZIRLOTM fuel rod
cladding. Thus, SCE needs an exemption from the requirements of 10 CFR
50.46, and Appendix K in order to use (irradiate) lead fuel assemblies
(LFAs) with a different cladding material, M5 alloy, at
[[Page 68640]]
SONGS 2 and 3. The scope of the staff's review of this temporary
exemption request is limited to the current burnup limits (i.e., 60
gigawatt-days per metric ton of uranium (GWD/MTU)). Extending the
burnup of these LFAs above 60 GWD/MTU will require further NRC staff
review and is beyond the scope of this exemption request.
The temporary exemption requested by the licensee would allow up to
16 LFAs with M5 alloy cladding manufactured by AREVA NP to be inserted
into the SONGS 2 reactor core or the SONGS 3 reactor core. Currently,
eight AREVA NP LFAs are scheduled for loading into the SONGS 2 reactor
core for Cycle 16. The exemption would allow the LFAs to be used for up
to three operating cycles (Cycles 16, 17, and 18). The use of M5 alloy
LFAs will allow SCE to evaluate cladding performance for future fuel
assemblies that need to be of a more robust design than the current
fuel assemblies, to allow for possible higher duty or extended burnup.
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 and
safety, and are consistent with the common defense and security; and
(2) special circumstances are present. Under 10 CFR 50.12(a)(2),
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 temporary exemption would allow the licensee to use a limited
number of M5 alloy LFAs to evaluate cladding performance for the design
of future fuel assemblies, which may need to be more robust than
current fuel assemblies, to account for possible higher duty or
extended burnup conditions. The regulations specify standards and
acceptance criteria only for fuel rods clad with zircaloy or
ZIRLOTM. Thus, a temporary exemption is required to allow
the licensee to use fuel rods clad with an advanced alloy that is not
zircaloy or ZIRLOTM. As stated above, 10 CFR 50.12
explicitly authorizes 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 temporary 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 temporary exemption
request for SONGS 2 and 3 relates solely to the types of cladding
material specified in the regulations. No new or altered design limits
for purposes of 10 CFR 50, Appendix A, General Design Criterion 10,
``Reactor Design,'' need to be applied or are required for the
licensee's LFA program. In its exemption request, SCE committed to
perform additional analyses of the LFAs to verify LFA performance and
compatibility with existing fuel assemblies. These analyses will use
approved methods, in compliance with the existing Technical
Specifications (TS) and consistent with the Updated Final Safety
Analysis Report (UFSAR) for SONGS 2 and 3, and will address the core
physics, core thermal hydraulics, fuel thermal-mechanical design, and
other safety analysis aspects of the LFAs. The LFAs will be placed in
non-limiting core locations, in accordance with TS 4.2.1, ``Fuel
Assemblies,'' where the peak integrated radial power peaking factor in
the LFAs will be 0.95 or less of the core maximum integrated radial
power peaking factor at all times in life. SCE further committed to
perform poolside examinations of the LFAs after each cycle of operation
to evaluate their performance and acceptability for continued use.
The underlying purpose of 10 CFR 50.46 is to establish acceptance
criteria for ECCS performance. The staff's review and approval of
topical report BAW-10227P-A, ``Evaluation of Advanced Cladding and
Structural Material (M5) in PWR Reactor Fuel,'' dated February 4, 2000
(ADAMS Accession Nos. ML003681479 and ML003681490), addressed all of
the important aspects of M5 cladding with respect to ECCS performance
requirements: (1) Applicability of 10 CFR 50.46(b) fuel acceptance
criteria, (2) M5 material properties including fuel rod ballooning and
rupture strains, and (3) steam oxidation kinetics and applicability of
the Baker-Just weight gain correlation. A subsequent NRC-approved
topical report, BAW-10240P-A, ``Incorporation of M5 Properties in
Framatome ANP Approved Methods,'' dated May 5, 2004 (ADAMS Accession
No. ML041260560), further addressed M5 material properties with respect
to loss-of-coolant accident (LOCA) applications.
Based on an ongoing LOCA research program at Argonne National
Laboratory (ANL), and NRC Research Information Letter 0801, ``Technical
Basis for Revision of Embrittlement Criteria in 10 CFR 50.46,'' dated
May 30, 2008 (ADAMS Accession No. ML081350225), cladding corrosion (and
associated hydrogen pickup) has a significant impact on post-quench
ductility. Pre-test characterization of irradiated M5 fuel cladding
segments at ANL provides further evidence of favorable corrosion and
hydrogen pickup characteristics of M5 as compared with standard
Zircaloy-4. Hence, the M5 fuel rods would be less susceptible to the
detrimental effects of hydrogen uptake during normal operation and
their impact on post-quench ductility. Furthermore, ANL post-quench
ductility tests on un-irradiated and irradiated M5 cladding segments
demonstrate that the 10 CFR 50.46(b) fuel criteria (i.e., 2200 degrees
Fahrenheit and 17 percent equivalent cladding reacted) remain
conservative up to current burnup limits.
Information provided in the NRC-approved M5 alloy topical reports,
as well as recent ANL LOCA research, demonstrates that the acceptance
criteria within 10 CFR 50.46 remain valid for M5 alloy cladding, and
thus, the underlying purpose of the rule--to maintain a degree of post-
quench ductility in the fuel cladding material--is met.
Paragraph I.A.5 of Appendix K to 10 CFR Part 50 states that the
rates 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 LFA cladding for determining acceptable fuel
performance. Metal-water reaction tests performed on M5 alloy material
by AREVA NP (as discussed in topical report BAW-10227P-A) demonstrate
conservative reaction rates relative to the Baker-Just equation. Thus,
strict application of Appendix K, Paragraph I.A.5 is not necessary to
achieve the underlying purpose of the rule in these circumstances, as
acceptable performance of the LFAs can be demonstrated.
In addition, SCE states that the LFAs will be placed in non-
limiting core locations, which provides further margin to ECCS
performance requirements and ensures that the behavior of the LFAs is
bounded by the safety analyses performed for the standard fuel rods.
Based upon the results of metal-water reaction testing
[[Page 68641]]
and mechanical testing, which demonstrate that the 10 CFR 50.46
acceptance criteria and 10 CFR 50 Appendix K methods can be applied to
the M5 alloy material, and the planned placement of the LFAs in non-
limiting core locations, the NRC staff finds it acceptable to grant a
temporary exemption from the requirements of 10 CFR 50.46 and Appendix
K to 10 CFR Part 50 for the use of up to 16 AREVA NP LFAs within SONGS
2 and 3.
Based on the above, no new accident precursors are created by
allowing the use of the LFAs with M5 cladding material in the SONGS 2
and/or SONGS 3 reactor cores during operating Cycles 16, 17, and 18;
therefore, the probability of postulated accidents is not increased.
Also, based on the above, the consequences of postulated accidents are
not increased. Therefore, there is no undue risk to public health and
safety in granting this temporary exemption.
Consistent With Common Defense and Security
The temporary exemption would allow up to 16 LFAs, with advanced M5
alloy cladding material, to be inserted into the SONGS 2 reactor core
or potentially into the SONGS 3 reactor core. Currently, eight AREVA NP
LFAs are scheduled to be loaded into the SONGS 2 core for Cycle 16, to
be used for up to three operating cycles (Cycles 16, 17, and 18). This
change to the reactor core configuration does not affect any existing
or planned security measures. Therefore, the common defense and
security is not impacted by this temporary exemption.
Special Circumstances
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii),
are present whenever application of the specific regulation in the
particular circumstance would not serve, or 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 ECCS performance. The wording of the
regulations in 10 CFR 50.46 and Appendix K is not directly applicable
to the M5 advanced cladding alloy, even though the evaluations
discussed above show that the intent of the regulations is met.
Therefore, since the underlying purposes of 10 CFR 50.46 and Appendix K
are achieved with the use of the M5 advanced cladding alloy, the
special circumstances required by 10 CFR 50.12(a)(2)(ii) for granting
of an exemption exist.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a), the temporary 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 SCE
temporary exemption from the requirements of 10 CFR 50.46 and Appendix
K to 10 CFR Part 50 to allow up to 16 LFAs clad with M5 alloy and
manufactured by AREVA NP, to be inserted into the SONGS 2 reactor core
or the SONGS 3 reactor core, in non-limiting core locations, for use
for up to three operating cycles (Cycles 16, 17, and 18 for the
respective units).
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this temporary exemption will not have a significant effect
on the quality of the human environment (74 FR 51339; October 6, 2009).
This temporary exemption is effective upon issuance.
Dated at Rockville, Maryland, this 17th day of December 2009.
For the Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear
Reactor Regulation.
[FR Doc. E9-30674 Filed 12-24-09; 8:45 am]
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