[Federal Register Volume 66, Number 205 (Tuesday, October 23, 2001)]
[Notices]
[Pages 53641-53643]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-26694]


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NUCLEAR REGULATORY COMMISSION

[Docket No. STN 50-530]


Arizona Public Service Company, Palo Verde Nuclear Generating 
Station, Unit 3; Exemption

1.0  Background

    The Arizona Public Service Company (APS/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 U.S. Nuclear Regulatory 
Commission (NRC, the Commission) now, or hereafter in effect.
    The facility consists of a pressurized water reactor located in 
Maricopa County in Arizona.

[[Page 53642]]

2.0  Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR), part 50, 
discusses fuel performance requirements for fuel used in light water 
nuclear power reactors. The requirements refer specifically to cladding 
types of zircaloy or ZIRLO, and do not address other cladding material. 
Since advanced zirconium based cladding materials do not conform to the 
two designations specified in the code, an exemption is required.
    APS requested a temporary exemption from the requirements of 10 CFR 
50.44, 10 CFR 50.46, and 10 CFR part 50, appendix K, for PVNGS, Unit 3, 
by letter dated March 2, 2001, as supplemented on August 28, 2001, and 
September 25, 2001. The exemption would allow continued testing of a 
lead fuel assembly (LFA) containing fuel rods fabricated with an 
advanced zirconium based cladding material, designated as Alloy A. This 
cladding material has been previously approved for limited use and 
testing at PVNGS in letters dated July 17, 1992, and February 4, 1997. 
The requested exemption extension would allow the Unit 3 LFA to exceed 
the already approved operating cycles.
    Part 50 of 10 CFR specifies standards and acceptance criteria only 
for fuel rods clad with zircaloy or ZIRLO. As noted above, APS was 
granted an exemption to use Alloy A in a limited number of pins 
starting in Cycle 4 and continuing through Cycle 6 in Unit 3. Based on 
the success of this advanced cladding, APS was granted an additional 
exemption to extend the burnup for a limited number of pins clad with 
Alloy A during Cycle 7. As part of the second exemption, APS was 
allowed to use a full assembly of the Alloy A clad in Unit 3 for three 
operating cycles, starting in Cycle 7. Based on the results of physical 
examination and measurements that have confirmed the superior 
performance of Alloy A, and NRC's prior approval for a limited number 
of pins, APS has requested an exemption to extend the burnup into Cycle 
10 for the full assembly of Alloy A fuel rods.
    Section 50.44 (a) of 10 CFR states, ``Each boiling or pressurized 
light-water nuclear power reactor fueled with oxide pellets within 
cylindrical zircaloy or ZIRLO cladding, must, as provided in paragraphs 
(b) through (d) of this section, include means for control of hydrogen 
gas that may be generated, following a postulated loss-of-coolant 
accident (LOCA).''
    Section 50.46(a)(1)(i) of 10 CFR states, ``Each boiling or 
pressurized light-water nuclear power reactor fueled with uranium oxide 
pellets within cylindrical zircaloy or ZIRLO cladding must be provided 
with an emergency core cooling system (ECCS) that must be designed so 
that its calculated cooling performance following postulated loss-of-
coolant accidents conforms to the criteria set forth in paragraph (b) 
of this section. ECCS cooling performance must be calculated in 
accordance with an acceptable evaluation model and must be calculated 
for a number of postulated loss-of-coolant accidents of different 
sizes, locations, and other properties sufficient to provide assurance 
that the most severe postulated loss-of-coolant accidents are 
calculated.''
    Section 50.46 of 10 CFR continues on to delineate specifications 
for peak cladding temperature, maximum hydrogen generation, coolable 
geometry, and long-term cooling. Sections 50.44 and 50.46 of 10 CFR 
specifically refer to fuel with zircaloy or ZIRLO cladding; the use of 
fuel clad with zirconium-based alloys that do not conform to either of 
these two designations requires an exemption from this section of the 
Code.
    Appendix K, paragraph I.A.5, of 10 CFR part 50 states, ``The rate 
of energy release, hydrogen generation, and cladding oxidation from the 
metal/water reaction shall be calculated using the Baker-Just 
equation.'' The Baker-Just equation presumes the use of zircaloy or 
ZIRLO cladding. The use of fuel with zirconium-based alloys that do not 
conform to either of these two designations requires an exemption from 
this section of the Code.
    APS believes that special circumstances are present, pursuant to 10 
CFR 50.12(a)(ii), to warrant granting the exemption request.

3.0  Discussion

    Pursuant to 10 CFR 50.12, the Commission may, upon application by 
an 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. These circumstances include 
the special circumstances as set forth in 10 CFR 50.12(a)(2)(ii), which 
states that special circumstances are present whenever, ``Application 
of the regulation in the particular circumstances would not serve the 
underlying purpose of the rule or is not necessary to achieve the 
underlying purpose of the rule.''
    The underlying purpose of 10 CFR 50.44 is to ensure that there is 
an adequate means of controlling generated hydrogen. The hydrogen 
produced in a post-LOCA scenario comes from a metal-water reaction. In 
the previous exemptions, it was concluded that the use of the Baker-
Just equation to determine the metal-water reaction rate is 
conservative for Alloy A cladding. Therefore, the amount of hydrogen 
generated by metal-water reaction in these materials will be within the 
design basis of Palo Verde Unit 3.
    Section 50.46 of 10 CFR identifies acceptance criteria for ECCS 
system performance at nuclear power facilities. The effectiveness of 
the ECCS in Palo Verde Unit 3 will not be affected by the reinsertion 
of the LFA. Due to the similarities in the material properties of Alloy 
A to zircaloy, and the location of the LFA in a non-limiting location, 
it can be concluded that the ECCS performance in Palo Verde Unit 3 will 
not be adversely affected.
    The intent of paragraph I.A.5 of Appendix K to 10 CFR part 50 is to 
apply an equation for rates of energy release, hydrogen generation, and 
cladding oxidation from a metal-water reaction which conservatively 
bounds all post-LOCA scenarios. CEN-429-P, Rev. 00-P, ``Safety Analysis 
Report for Use of Advanced Zirconium Based Cladding Material in PVNGS 
Unit 3 Lead Fuel Assemblies,'' August 1996, verifies that due to the 
similarities in the composition of the Alloy A cladding and zircaloy, 
the application of the Baker-Just equation will continue to 
conservatively bound all post-LOCA scenarios.
    The staff examined the licensee's rationale to support the 
exemption requests and concluded that continued use of advanced 
zirconium based cladding materials would meet the underlying purpose of 
10 CFR part 50.
    Based upon the considerations discussed in this exemption, the 
staff concludes that the information provided by APS and the actions 
described in the application form an acceptable basis for extending the 
exemption for another cycle.
    The safety evaluation may be examined, and/or copied for a fee, at 
the NRC's Public Document Room, located at One White Flint North, 11555 
Rockville Pike (first floor), Rockville, Maryland. Publicly available 
records will be accessible electronically from the ADAMS Public Library 
component on the NRC Web site, http://www.nrc.gov (the Public 
Electronic Reading Room).
    Therefore, the staff concludes that pursuant to 10 CFR 
50.12(a)(2)(ii),

[[Page 53643]]

special circumstances exist as discussed in Section 3.0 above, and 
granting this exemption will not present an undue risk to the public 
health and safety and is consistent with the common defense and 
security.

4.0  Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not endanger life or 
property or common defense and security, and is, otherwise, in the 
public interest. Also, special circumstances are present. Therefore, 
the Commission hereby grants Arizona Public Service Company, et al., an 
exemption from the requirements of 10 CFR 50.44, 10 CFR 50.46, and 10 
CFR part 50, appendix K, for Palo Verde Nuclear Generating Station, 
Unit 3.
    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 (66 FR 52644).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 16th day of October 2001.
    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 01-26694 Filed 10-22-01; 8:45 am]
BILLING CODE 7590-01-P