[Federal Register Volume 68, Number 153 (Friday, August 8, 2003)]
[Notices]
[Pages 47370-47371]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-20240]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-413 and 50-414]
Duke Energy Corporation, North Carolina Electric Membership
Corporation, Saluda River Electric Cooperative, Inc., Catawba Nuclear
Station, Units 1 and 2; Exemption
1.0 Background
Duke Energy Corporation et al., (the licensee) is the holder of
Facility Operating License Nos. NPF-35 and NPF-52, which authorize
operation of the Catawba Nuclear Station, Units 1 and 2. The licenses
provide, 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 two pressurized water reactors located in
York County, South Carolina.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR) part 50,
section 50.46 and appendix K identify requirements for calculating
emergency core cooling system (ECCS) performance for reactors
containing fuel with Zircaloy or ZIRLO cladding, and 10 CFR 50.44
identifies requirements for the control of hydrogen gas generated in
part from a metal-water reaction between the reactor coolant and
reactor fuel having Zircaloy or ZIRLO cladding.
The licensee has requested, in its letter dated December 3, 2002,
as supplemented by letter dated April 8, 2003, a temporary exemption to
10 CFR 50.44, ``Standards for combustible gas control system in light-
water-cooled power reactors,'' 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,'' that would allow the Catawba Nuclear Station, Units 1 and 2
to operate using eight lead test assemblies (LTAs) with a tin
composition that is nominally below the lower bound licensed limit of
0.80 percent, as specified in WCAP-12610-P-A, ``VANTAGE+ Fuel Assembly
Reference Core Report,'' in non-limiting core locations. The purpose of
the LTAs is to obtain data that would allow the optimization of ZIRLO
corrosion resistance, in order to support improved fuel performance and
reliability at increased burnup levels.
3.0 Discussion
Pursuant to 10 CFR 50.12, ``Specific exemptions,'' 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 section 50.12(a)(2), special circumstances include,
among other things, when the application of the regulation would not
serve, or is not necessary to achieve, the underlying purpose of the
rule.
The underlying purpose of 10 CFR 50.44, 10 CFR 50.46, and appendix
K to 10 CFR part 50, is to establish requirements for the calculation
of ECCS performance, and acceptance criteria for that performance, in
order to assure that the ECCS functions to transfer heat from the
reactor core following a loss-of-coolant-accident, such that (1) fuel
and clad damage that could interfere with continued effective core
cooling is prevented, and (2) clad metal-water reaction is limited to
specified amounts.
The mechanical properties of the low-tin ZIRLO in the LTAs are very
similar to those of the approved ZIRLO, since both of these alloys are
zirconium-based materials with slight variations in tin content. The
licensee will perform an evaluation of the fuel rod design using the
same methods used for the current robust fuel assembly design. No new
or altered design limits need to be applied, nor are any required for
this program for the purposes of 10 CFR part 50, appendix A, ``General
Design Criteria for Nuclear Power Plants,'' Criterion 10, ``Reactor
Design'' (GDC 10). The licensee has evaluated the three areas of the
mechanical design that could potentially be impacted by low-tin ZIRLO,
namely, material properties, corrosion and thermal creep. The staff
evaluated the data provided to substantiate that the material
properties are similar to Zircaloy and that the corrosion and thermal
creep will remain within established acceptance criteria. The NRC staff
concludes that the data show that the selected LTA mechanical design
will satisfy established acceptance criteria and should perform safely
in the Catawba Nuclear Station.
The licensee has performed evaluations of the impact of the LTAs on
the nuclear design. The approved reload methodologies can be used to
model the LTAs since the features of the LTAs do not challenge the
validity of the standard methodologies. The licensee has limited the
number of LTAs to eight, and all of the LTAs will be placed in non-
limiting locations in the
[[Page 47371]]
core. The licensee will use the approved reload methodologies for the
Catawba Nuclear Station reload design containing the LTAs. Given the
limited number of LTAs to be installed and the installation in non-
limiting locations, the NRC staff concludes that the LTA core design is
acceptable for use in the Catawba Nuclear Station.
10 CFR 50.46 identifies acceptance criteria for ECCS performance at
nuclear power plants. The material properties of the low-tin ZIRLO are
similar to those of the current ZIRLO cladding. Because the current
analyses are done with material properties that approximate the low-tin
ZIRLO properties, the current ECCS analysis remains applicable and
unchanged for the LTAs. Therefore, the NRC staff concludes that the
ECCS performance of the Catawba Nuclear Station will not be adversely
affected by the insertion of eight low-tin ZIRLO LTAs. As such, the
licensee has achieved the underlying purpose of 10 CFR 50.46. The staff
has also concluded that should these LTAs fail, the consequences will
be bounded by the current analyses for fuel failures and radiological
assessments because the source term will not be affected by a different
cladding material.
Paragraph I.A.5 of appendix K to 10 CFR part 50 states that the
rates of energy, hydrogen concentration, 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 determining acceptable fuel performance of advanced
zirconium-based alloys. The underlying intent of this portion of the
appendix, however, is to ensure that analysis of fuel response to LOCAs
is conservatively calculated. Due to the similarities in the chemical
composition between the low-tin ZIRLO and ZIRLO, the application of the
Baker-Just equation in the analysis of low-tin ZIRLO clad fuel will
conservatively bound all post-LOCA scenarios. Thus, the underlying
purpose of the rule will be met. Therefore, special circumstances exist
to grant an exemption from appendix K to 10 CFR part 50 that would
allow the licensee to apply the Baker-Just equation to low-tin ZIRLO.
The purpose of 10 CFR 50.44 is to ensure that means are provided
for the control of hydrogen gas that may be generated following a LOCA.
The hydrogen produced in a post-LOCA scenario comes from a metal-water
reaction. Tests performed by Westinghouse on the low-tin ZIRLO alloy
have demonstrated that the reduction in tin content will have no
significant effect on current assessments of hydrogen gas production.
As such, the licensee has met the underlying purpose of 10 CFR 50.44.
The NRC staff examined the licensee's rationale to support the
exemption request and, for the reasons set forth above, concludes that
allowing these eight LTAs with a nominally lower tin composition would
meet the underlying purpose of 10 CFR 50.44, 10 CFR 50.46, and appendix
K to 10 CFR part 50. Further, the NRC staff has determined that the
reduction in tin content will have no significant effect on current
assessments of a metal-water reaction, and that the mechanical design
of the LTAs would perform satisfactorily. Therefore, ECCS performance
will not be adversely affected and application of 10 CFR 50.44, 10 CFR
50.46 and 10 CFR part 50, appendix K, is not necessary to achieve their
underlying purpose.
Based upon the considerations above, the NRC staff concludes that,
pursuant to 10 CFR 50.12(a)(2), the granting of this exemption is
acceptable.
4.0 Conclusion
For the reasons set forth above, the Commission has determined
that, pursuant to 10 CFR 50.12(a), 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 Duke
Energy Corporation an exemption from the requirements of 10 CFR part
50, section 50.44, section 50.46, and appendix K to 10 CFR part 50,
with respect to the use of low-tin ZIRLO LTAs at the Catawba Nuclear
Station.
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 (68 FR 42136).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 4th day of August 2003.
For The Nuclear Regulatory Commission.
Herbert N. Berkow,
Acting Director, Division of Licensing Project Management, Office of
Nuclear Reactor Regulation.
[FR Doc. 03-20240 Filed 8-7-03; 8:45 am]
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