[Federal Register Volume 73, Number 205 (Wednesday, October 22, 2008)]
[Notices]
[Pages 63024-63025]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-25152]


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NUCLEAR REGULATORY COMMISSION

[Docket No. STN 50-528]


Arizona Public Service Company, et al.; Palo Verde Nuclear 
Generating Station, Unit 1; Temporary Exemption

1.0 Background

    The Arizona Public Service Company (APS, the licensee) is the 
holder of the Renewed Facility Operating License No. NPF-41 which 
authorizes operation of the Palo Verde Nuclear Generating Station 
(PVNGS), Unit 1. The license provides, 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 a pressurized-water reactor located in 
Maricopa County, Arizona.

2.0 Request/Action

    Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), 
Section 50.12, ``Specific exemptions,'' APS has, by letter dated March 
8, 2008, and supplemented by letter dated September 10, 2008 
(Agencywide Documents Access and Management System (ADAMS) Accession 
Nos. ML080790524 and ML082620212, 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 Evaluation Models,'' (Appendix K). The 
regulation in 10 CFR 50.46 contains acceptance criteria for the 
emergency core cooling system (ECCS) for reactors fueled with zircaloy 
or ZIRLO\TM\ 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. The temporary 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 lead fuel assemblies 
(LFAs) comprised of different cladding alloys at PVNGS, Unit 1. 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 unit (GWD/MTU). Extending the burnup of these LFAs will require 
further NRC staff review.
    The temporary exemption requested by the licensee would allow up to 
eight LFAs manufactured by AREVA NP consisting of fuel rods with M5 
cladding material to be inserted into the PVNGS, Unit 1 reactor core in 
non-limiting locations during operating Cycles 15, 16, and 17. The use 
of M5 LFAs will allow APS to evaluate cladding 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 the use of M5 
LFAs to evaluate cladding for future fuel assemblies that may need to 
be of a more robust design than the current fuel assemblies to allow 
for possible higher duty or extended burnup. The regulations specify 
standards and acceptance criteria only for fuel rod clads with Zircaloy 
or ZIRLO\TM\. Thus, a temporary exemption is required to use fuel rods 
clad with an advanced alloy that is not Zircaloy or ZIRLO\TM\. 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 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 PVNGS, Unit 1 
temporary exemption request relates solely to the specific 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 this program. Also, the NRC staff's review was limited to the 
exemption request and does not address the core physics, core thermal 
hydraulics, fuel thermal-mechanical design, or the safety analysis 
aspects of the LFAs associated with the Updated Safety Analysis Report 
nor their placement in a non-limiting core location. APS has notified 
the staff of their intent to evaluate the LFAs as a change to the plant 
in accordance with 10 CFR 50.59. Furthermore, APS has provided 
information related to their planned evaluation of the LFAs as part of 
their exemption request (letter dated March 8, 2008) and in response to 
RAIs (letter dated September 10, 2008).
    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 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 
Baker-Just weight gain correlation. A subsequent NRC-approved topical 
report, BAW-10240P-A, ``Incorporation of M5 Properties in Framatome ANP 
Approved Methods,'' 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 Research Information Letter 0801, titled, 
``Technical Basis for Revision of Embrittlement Criteria in 10 CFR 
50.46,'' dated May 30, 2008 (ADAMS Accession No. ML0813502251), 
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 provide further evidence of

[[Page 63025]]

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 previously approved M5 topical reports, 
as well as recent ANL LOCA research, demonstrate that the acceptance 
criteria within 10 CFR 50.46 remain valid for M5 alloy and meet the 
underlying purpose of the rule--maintain a degree of post-quench 
ductility in the fuel cladding material.
    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 by AREVA (topical 
report BAW-10227-P-A) 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.
    In addition, APS states that the eight LFAs will be placed in non-
limiting core locations (e.g., lower power assembly locations), which 
provide further margin to ECCS performance requirements and ensure that 
the behavior of the LFAs is bounded by the safety analyses performed 
for the standard fuel rods. Based upon results of metal-water reaction 
testing and mechanical testing, which ensure the applicability of 10 
CFR 50.46 acceptance criteria and 10 CFR 50 Appendix K methods and the 
placement of LFAs in non-limiting locations, the 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 eight AREVA 
LFAs within PVNGS, Unit 1.
    Based on the above, no new accident precursors are created by 
allowing the use of LFAs with M5 cladding material in PVNGS, Unit 1 
reactor core during operating Cycles 15, 16, and 17, thus, 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.

Consistent With Common Defense and Security

    The proposed temporary exemption would allow the use of up to eight 
LFAs with advanced cladding materials. This change to the plant core 
configuration has no relation to security issues. 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 these advanced cladding alloys, even though the evaluations 
discussed above show that the intent of the regulations are met. 
Therefore, since the underlying purposes of 10 CFR 50.46 and Appendix K 
are achieved with the use of these advanced cladding alloys, the 
special circumstances required by 10 CFR 50.12(a)(2)(ii) for 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 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 APS 
temporary exemption from the requirements of 10 CFR 50.46 and Appendix 
K to 10 CFR Part 50, to allow the use of fuel rods clad with an 
advanced alloy that is not Zircaloy or ZIRLO\TM\ to be inserted into 
the PVNGS, Unit 1 reactor core in non-limiting locations during 
operating Cycles 15, 16, and 17.
    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 (73 FR 57386, October 2, 2008).
    This temporary exemption is effective upon issuance.


    Dated at Rockville, Maryland, this 14th day of October 2008.

    For the Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
[FR Doc. E8-25152 Filed 10-21-08; 8:45 am]
BILLING CODE 7590-01-P