[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