[Federal Register Volume 75, Number 170 (Thursday, September 2, 2010)]
[Notices]
[Pages 53985-53987]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-21942]


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NUCLEAR REGULATORY COMMISSION

[Docket No. STN 50-530; NRC-2010-0281]


Arizona Public Service Company, et al., Palo Verde Nuclear 
Generating Station, Unit 3; Temporary Exemption

1.0 Background

    Arizona Public Service Company (APS, the licensee) is the holder of 
Facility Operating License No. NPF-74, which authorizes operation of 
the Palo Verde Nuclear Generating Station (PVNGS), Unit 3. The license 
provides, among other things, that the facility is subject to all 
rules, regulations, and orders of the Nuclear Regulatory Commission 
(NRC, 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 
November 2, 2009, and supplemented by letter dated May 12, 2010 
(Agencywide Documents Access and Management System (ADAMS) Accession 
Nos. ML093160596 and ML101410262, 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 part 50, ``ECCS Evaluation Models,'' (Appendix K). The 
regulations in 10 CFR 50.46 contain acceptance criteria for the 
emergency core cooling system (ECCS) for reactors fueled with zircaloy 
or ZIRLO 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 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 3.
    The temporary exemption requested by the licensee would allow up to 
eight LFAs manufactured by Westinghouse Electric Company LLC 
(Westinghouse) with fuel rods clad with Optimized ZIRLO\TM\ to be 
inserted into the PVNGS, Unit 3, core during the fall 2010 refueling 
outage. The temporary exemption would allow the LFAs to be used for up 
to three operating cycles (Cycles 16, 17, and 18).

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 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 exemption would allow up to eight LFAs with Optimized 
ZIRLO\TM\ cladding to be inserted into the PVNGS, Unit 3 reactor core 
during the fall 2010 refueling outage. It would also allow the LFAs to 
be used for up to three operating cycles (Cycles 16, 17, and 18). The 
Optimized ZIRLO\TM\ cladding is of a slightly different material 
composition than the zircaloy or ZIRLO cladding explicitly identified 
in 10 CFR 50.46, and implicitly assumed in 10 CFR part 50, Appendix K, 
for light water reactor fuel. However, the fundamental requirements 
regarding ECCS performance can still be satisfied by the LFAs with the 
Optimized ZIRLO\TM\ cladding. 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

    The underlying purpose of 10 CFR 50.46 is to establish acceptance 
criteria for ECCS performance. Westinghouse topical reports WCAP-16500-
P-A, Revision 0, ``CE [Combustion Engineering] 16x16 Next Generation 
Fuel Core Reference Report,'' dated

[[Page 53986]]

August 2007, and WCAP-12610-P-A & CENPD-404-P-A, ``Optimized 
ZIRLO\TM\,'' dated July 2006, contain the justification to use 
Optimized ZIRLO\TM\ as a fuel cladding material in addition to 
Zircaloy-4 and ZIRLO (these topical reports are non-publicly available 
because they contain proprietary information). The NRC staff approved 
the use of these topical reports, subject to the conditions stated in 
the staff's safety evaluations for each. In these topical reports, 
Westinghouse evaluated the structural and material properties of 
Optimized ZIRLO\TM\ and determined that the use of Optimized ZIRLO\TM\ 
as cladding would have either no significant impact or would produce a 
reduction in corrosion or oxidation and a corresponding reduction in 
hydrogen pickup. Westinghouse also evaluated the impact of Optimized 
ZIRLO\TM\ fuel cladding on the LOCA and non-LOCA accident analyses. The 
evaluations determined that the LOCA analyses for fuel with Optimized 
ZIRLO\TM\ cladding complied with 10 CFR 50.46, and that there was a 
negligible difference in the non-LOCA analyses between fuel clad with 
standard ZIRLO and fuel clad with Optimized ZIRLO\TM\.
    The underlying purpose of 10 CFR part 50, Appendix K, Section 
I.A.5, ``Metal-Water Reaction Rate,'' is to ensure that cladding 
oxidation and hydrogen generation are appropriately limited during a 
LOCA and conservatively accounted for in the ECCS evaluation model. 
Appendix K of 10 CFR part 50 requires that the Baker-Just equation be 
used in the ECCS evaluation model to determine the rate of energy 
release, cladding oxidation, and hydrogen generation. Westinghouse has 
shown in WCAP-12610-P-A that the Baker-Just model is conservative in 
all post-LOCA scenarios with respect to the use of the Optimized 
ZIRLO\TM\ advanced alloy as a fuel cladding material.
    In its exemption request dated November 2, 2009, APS commits to 
evaluate the performance of the Next Generation Fuel (NGF) LFAs with 
Optimized ZIRLO\TM\ cladding with respect to the PVNGS safety analyses. 
The analyses to be performed as part of that evaluation, which the 
licensee commits to being due October 30, 2010, shall include thermal 
hydraulic compatibility, loss-of-coolant accident (LOCA) and non-LOCA 
criteria, mechanical design, thermal hydraulics, seismic, core physics, 
and neutronic capability of the NGF LFAs in the PVNGS, Unit 3 reactor 
core. The thermal-hydraulic compatibility analyses for the LFAs shall 
include evaluations of departure from nucleate boiling (DNB) 
performance, guide tube heating, core bypass flow, fuel centerline 
melt, rod bow, and LOCA. The neutronic compatibility evaluation will 
compare design characteristics of the LFAs to co-resident fuel to 
ensure compatibility. Furthermore, APS commits to having a 
compatibility study performed to ensure that insertion of the LFAs will 
not cause the remaining Westinghouse fuel to exceed its operating 
limits and ensure there is no adverse impact on the fuel performance or 
mechanical integrity. In order to ensure compatibility, the study shall 
include detailed evaluations in several functional areas, such as 
structural/seismic analyses, ECCS performance, LOCA dose assessment, 
thermal hydraulics, and mechanical design. In addition, the evaluations 
will determine the impact on the analyses of record, if any. The 
licensee commits to a due date of October 30, 2010, for the 
compatibility study. In addition, the licensee commits to poolside 
examinations of the ongoing assembly and cladding performance as 
detailed in the ``Commitments, Conditions, and Limitations'' section 
below.
    APS shall place the LFAs in non-limiting power locations where the 
predicted peak pin power is less than or equal to 0.95 of the predicted 
cycle maximum peak pin power in the core. Therefore, the LFAs will not 
contain the lead rod in the core and will have margin relative to cycle 
maximum peak power. Since the LFAs will not be in the highest core 
power density locations, their operation will be bounded by the safety 
analyses performed for the existing fuel assemblies. Additionally, the 
maximum LFA integrated fuel rod burnup shall be maintained less than or 
equal to 60 gigawatt days per metric ton uranium.
    The PVNGS, Unit 3, 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 part 50, 
Appendix A, General Design Criterion 10, ``Reactor Design,'' need to be 
applied or are required for this exemption.
    Based on the use of approved models and methods, expected material 
performance, and the placement of the LFAs in non-limiting core 
locations, the NRC staff concludes that the irradiation of up to eight 
LFAs in the PVNGS, Unit 3, core will not result in unsafe operation or 
violation of specified acceptable fuel design limits. Furthermore, in 
the event of a design-basis accident, these LFAs will not cause 
consequences beyond those previously analyzed. Based upon results from 
experimental data using Optimized ZIRLO\TM\ cladding for its cooling 
performance, and the results of the calculations of rate of energy 
release, hydrogen generation, and cladding oxidation from the metal-
water reaction, which ensure the applicability of ECCS models and 
acceptance criteria, and the use of approved LOCA evaluation models to 
ensure that LFAs satisfy 10 CFR 50.46 acceptance criteria, the NRC 
staff considers the LFAs acceptable for use in the PVNGS, Unit 3, core 
as proposed, subject to the additional commitments made by APS.
    Based on the above, no new accident precursors are created by 
allowing the use of the LFAs with Optimized ZIRLO\TM\ cladding material 
in the PVNGS, Unit 3, core during Operating Cycles 16, 17, and 18. 
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 proposed exemption would allow the use of up to 8 LFAs with 
advanced cladding material. This change to the plant 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(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 Optimized ZIRLO\TM\ cladding, even though the evaluations 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 the Optimized ZIRLO\TM\ cladding, the special circumstances 
required by 10 CFR 50.12(a)(2)(ii) for the granting of an exemption 
exist.

Commitments, Conditions, and Limitations

    In its letter dated November 2, 2009, the licensee made the 
following regulatory commitments:
    1. Prior to startup for Unit 3 Cycle 17, poolside examinations will 
be

[[Page 53987]]

performed to evaluate ongoing assembly and cladding performance. (Due 
4/30/2012)
    2. Prior to startup for Unit 3 Cycle 18, poolside examinations will 
be performed to evaluate ongoing assembly and cladding performance. 
(Due 10/30/2013)
    3. After completion of Unit 3 Cycle 18 (the third and final 
irradiation cycle), poolside examinations will be performed to evaluate 
assembly and cladding performance. (Due 6/30/2015)
    4. The Westinghouse NGF LFAs will be modeled in the PVNGS core 
physics models, including the Zirconium di-boride integral fuel 
burnable absorber (IFBA). As such, the impact of the LFAs will be 
included in the PVNGS cycle-specific core physics calculations 
supporting the reload effort for each cycle during use of the LFAs. 
(Due 10/30/2010, 4/30/2012, and 10/30/2013, respectively)
    5. Evaluations will verify performance of the Westinghouse NGF LFAs 
with respect to the safety analysis. The analyses will include thermal-
hydraulic compatibility, loss-of-coolant accident (LOCA) and non-LOCA 
criteria, mechanical design, thermal hydraulic, seismic, core physics, 
and neutronic compatibility of the LFAs in the PVNGS Unit 3 core. The 
evaluations will make use of the fact that the LFAs will be operated in 
non-limiting locations and will verify the reload analyses are not 
adversely impacted. The results will be documented in a final design 
report. (Due 10/30/2010)
    6. A compatibility study will be performed to ensure that insertion 
of the Westinghouse NGF LFAs will not cause the remaining Westinghouse 
fuel to exceed its operating limits and ensure there is no adverse 
impact on fuel performance or mechanical integrity. The results of the 
compatibility study will be documented in a final design report. (Due 
10/30/2010)
    In addition, since APS referenced Westinghouse Topical Report WCAP-
12610-P-A & CENPD-404-P-A, Addendum 1-A, ``Optimized 
ZIRLO<SUP>TM</SUP>,'' dated July 2006, in its request for the exemption 
to use LFAs with Optimized ZIRLO<SUP>TM</SUP> cladding, the licensee 
shall ensure compliance with the conditions and limitations listed in 
Section 5.0 of the NRC staff's Safety Evaluation Report for that 
report.

4.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12, 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 APS a temporary exemption from 
the requirements of 10 CFR 50.46 and Appendix K to allow the use of 
fuel rods clad with an advanced alloy, Optimized ZIRLO<SUP>TM</SUP>, in 
the PVNGS, Unit 3, core in non-limiting locations during Operating 
Cycles 16, 17, and 18.
    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 as published in the Federal Register 
on August 24, 2010 (75 FR 52045).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 26th day of August 2010.

    For The Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
[FR Doc. 2010-21942 Filed 9-1-10; 8:45 am]
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