Southern California Edison: San Onofre Nuclear Generating Station, Unit 2 and Unit 3 Temporary Exemption, 68639-68641 [E9-30674]

Agencies

• NUCLEAR REGULATORY COMMISSION

[Federal Register Volume 74, Number 247 (Monday, December 28, 2009)]
[Notices]
[Pages 68639-68641]
From the Federal Register Online via the Government Printing 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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