[Federal Register Volume 69, Number 212 (Wednesday, November 3, 2004)]
[Notices]
[Pages 64113-64115]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-24493]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-498 and 50-499]


STP Nuclear Operating Company; South Texas Project, Unit No. 1 
and 2; Exemption

1.0 Background

    The STP Nuclear Operating Company (STPNOC or the licensee) is the 
holder of Facility Operating License Nos. NPF-76 and NPF-80, which 
authorize operation of South Texas Project (STP), Units 1 and 2, 
respectively. The licenses provide, 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 two pressurized water reactors located in 
Matagorda County, Texas.

2.0 Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR) part 50, 
section 50.44, specifies requirements for the control of hydrogen gas 
generated after a postulated loss-of-coolant accident (LOCA). Section 
50.46 of 10 CFR contains acceptance criteria for the emergency core 
cooling system (ECCS) for reactors with zircaloy or ZIRLO\TM\ clad 
fuel. Appendix K to 10 CFR part 50 requires, among other things, that 
the Baker-Just equation be used to predict the rates of energy release, 
hydrogen concentration, and cladding oxidation from the metal-water 
reaction. Of these three regulations (10 CFR 50.44, 50.46, and Appendix 
K to 10 CFR part 50), 10 CFR 50.44 is the only one that has undergone 
considerable changes relative to its previous version, changes that 
became effective on January 1, 2004.

[[Page 64114]]

Prior to that date, 10 CFR 50.44 specified requirements for the control 
of hydrogen gas generated after a postulated LOCA for reactors with 
zircaloy or ZIRLO\TM\ clad fuel. The new regulation in 10 CFR 50.44 no 
longer identifies zircaloy or ZIRLO\TM\ as requisite fuel cladding, nor 
does it identify the LOCA or 10 CFR 50.46 as bases. Because the intent 
of this exemption request relates solely to the specific types of 
cladding material specified in these regulations, no exemption is 
needed from the requirements of 10 CFR 50.44. As written, zircaloy or 
ZIRLO\TM\ cladding continues to be the requisite fuel cladding that is 
explicitly identified in 10 CFR 50.46 and Appendix K to 10 CFR part 50. 
Therefore, an exemption from the requirements of 10 CFR 50.46 and 
Appendix K to 10 CFR part 50 is needed in order to irradiate up to 
eight lead test assemblies (LTAs) comprised of low tin (Optimized) 
ZIRLO\TM\ at the STP, Units 1 and/or 2.
    In summary, in a letter dated May 27, 2004 (Reference 1)\1\, as 
supplemented by letter dated August 23, 2004 (Reference 2)\2\, STPNOC 
requested an exemption from 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,'' which would allow irradiation of up to 
eight LTAs containing fuel rods, guide tubes, and instrumentation tubes 
fabricated with Optimized ZIRLO<SUP>TM</SUP>. Optimized 
ZIRLO<SUP>TM</SUP> is not within the licensing basis of the approved 
ZIRLO<SUP>TM</SUP> as described in WCAP-12610-P-A (Reference 3)\3\ for 
STP, Units 1 and 2. Irradiation of up to eight Optimized 
ZIRLO<SUP>TM</SUP> LTAs in STP Units 1 and/or 2 will provide data on 
fuel and material performance to support future licensing activities.
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    \1\ Letter from T.J. Jordan (South Texas) to U.S. Nuclear 
Regulatory Commission, ``The South Texas Project, Units 1 and 2 
Request for Exemption Pursuant to 10 CFR 50.12 Exemption to the Fuel 
Cladding Material Specified in 10 CFR 50.44, 10 CFR 50.46, and 10 
CFR 50 Appendix K,'' Docket Nos. STN 50-498 and STN 50-499, May 27, 
2004, ADAMS Accession No. ML041590200.
    \2\ Letter from T.J. Jordan (South Texas) to U.S. Nuclear 
Regulatory Commission, ``The South Texas Project, Units 1 and 2 
Response to Request for Additional Information Regarding Exemption 
to Use a Low Tin Cladding,'' Docket Nos. STN 50-498 and STN 50-499, 
August 23, 2004, ADAMS Accession No. ML042430272.
    \3\ Westinghouse Electric Company Topical Report, WCAP-12610-P-
A, ``VANTAGE+ Fuel Assembly Reference Core Report,'' April 1995.
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3.0 Discussion

    The staff has previously reviewed exemption requests for LTA 
programs comprised of fuel with Optimized ZIRLO<SUP>TM</SUP> cladding 
material manufactured by Westinghouse Electric Company (Westinghouse). 
Exemptions from 10 CFR 50.46 and Appendix K to 10 CFR part 50 for use 
of Optimized ZIRLO<SUP>TM</SUP> have been issued by the NRC staff for 
Millstone, Unit 3 (Reference 4)\4\, Catawba Station (Reference 5)\5\, 
and Calvert Cliffs, Unit 2 (Reference 6)\6\.
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    \4\ Letter from U.S. Nuclear Regulatory Commission to D.A. 
Christian (Dominion), ``Millstone Power Station, Unit No. 3, 
Exemption from the Requirements of Title 10 of the Code of Federal 
Regulations (10 CFR) Part 50.44, 10 CFR 50.46, and 10 CFR part 50, 
Appendix K,'' Docket No. 50-423, February 11, 2004, ADAMS Accession 
No. ML040070238.
    \5\ Letter from U.S. Nuclear Regulatory Commission to D.M. Jamil 
(Duke), ``Catawba Nuclear Station, Units 1 and 2 RE: Exemption from 
the Requirements of 10 CFR 50.44, 10 CFR 50.46, and 10 CFR 50 
Appendix K,'' August 4, 2003, ADAMS Accession No. ML032060473.
    \6\ Letter from U.S. Nuclear Regulatory Commission to P.E. Katz 
(Constellation), ``Calvert Cliffs Nuclear Power Plant, Unit No. 2,'' 
December 3, 2002, ADAMS Accession No. ML022540002.
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3.1 Material Evaluation

3.1.1 Fuel Mechanical Design
    Tin is a solid solution strengthener and [alpha]-phase stabilizer 
present entirely in the base [alpha]-phase zirconium crystalline 
structure. Potential impacts of a reduced tin content on material 
properties include (1) a reduced tensile strength, (2) an increased 
thermal creep rate, (3) an increased irradiation growth rate, (4) a 
reduced [alpha][harr][alpha]+[beta] phase transition temperature, and 
(5) an improved corrosion resistance. The slight reduction in tin 
content will not affect the size, shape, or distribution of any second 
phase or inter-metallic precipitates nor the overall microstructure of 
this developmental zirconium alloy. With a consistent microstructure, 
Optimized ZIRLO<SUP>TM</SUP> will exhibit material characteristics very 
similar to that of ZIRLO<SUP>TM</SUP>.
    In Reference 2, the licensee provided information concerning their 
post-irradiation examination plan. In Reference 2, the licensee stated 
that their plan would be consistent with those of the other Optimized 
ZIRLO<SUP>TM</SUP> irradiation programs currently underway. As with the 
post-irradiation examinations involved in the other irradiation 
programs, the detailed examinations in the licensee's Optimized 
ZIRLO<SUP>TM</SUP> irradiation program will be based on the fuel duty, 
cycle performance, need for specific information, and time available on 
site during refueling outages. The measured parameters will include rod 
profilometry, rod wear, assembly and rod growth, assembly bow, grid 
cell dimensions, and oxide thickness. As a result of these post-
irradiation examinations, any negative aspects of the Optimized 
ZIRLO<SUP>TM</SUP> performance, including the potential impacts of 
reduced tin content identified above, will be identified and resolved. 
Furthermore, significant deviations from model predictions will be 
reconciled.
    The fuel rod burnup and fuel duty experienced by the Optimized 
ZIRLO<SUP>TM</SUP> LTAs in STP, Units 1 and 2, will remain well within 
the operating experience base and applicable licensed limits for 
ZIRLO<SUP>TM</SUP>.
    Utilizing currently approved fuel performance and fuel mechanical 
design models and methods, the STP, Units 1 and 2, and Westinghouse 
will perform cycle-specific reload evaluations to ensure that the 
Optimized ZIRLO<SUP>TM</SUP> LTAs satisfy design criteria.
    Based upon the irradiation experience of LTAs with 
ZIRLO<SUP>TM</SUP> of a similar low tin content, expected performance 
due to similar material properties, and an extensive LTA post-
irradiation examination program aimed at qualifying model predictions, 
the NRC staff finds the Optimized ZIRLO<SUP>TM</SUP> LTA mechanical 
design acceptable for STP, Units 1 and 2.
3.1.2 Core Physics and Non-LOCA Safety Analysis
    The STP, Units 1 and 2, exemption request relates solely to the 
specific types of cladding material specified in the regulations. Due 
to similar material properties, any impact of Optimized 
ZIRLO<SUP>TM</SUP> on the safety analysis models and methods is 
expected to be minimal. Utilizing currently approved core physics, core 
thermal-hydraulics, and non-LOCA safety analysis models and methods, 
the licensee and Westinghouse will perform cycle-specific reload 
evaluations to ensure that the LTAs satisfy design criteria. Fuel 
management guidelines will require that LTAs be placed in non-limiting 
core locations. In Reference 2, the licensee described how the power 
peaking margin would be used to ensure that LTAs will not be limiting.
    Based upon the use of approved models and methods, expected 
material performance, and the placement of LTAs in non-limiting core 
locations, the NRC staff finds that the irradiation of up to eight 
Optimized ZIRLO<SUP>TM</SUP> LTAs in STP, Units 1 and 2, will not 
result in unsafe operation nor violation of specified acceptable fuel 
design limits. Furthermore, in the event of a design-basis accident, 
these LTAs will not

[[Page 64115]]

promote consequences beyond those currently analyzed.

3.2 ECCS Performance and Exemptions

    Pursuant to 10 CFR 50.12, the Commission may, upon application by 
any interested person or 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) special 
circumstances are present. Special circumstances are present if 
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 50.46 is to establish acceptance 
criteria for ECCS performance. In Addendum 1 to WCAP-12610-P-A 
(Reference 7)\7\, Westinghouse demonstrates that the material 
properties of Optimized ZIRLO<SUP>TM</SUP> are similar to those of the 
currently approved ZIRLO<SUP>TM</SUP> cladding and that the ECCS 
acceptance criteria for ZIRLO<SUP>TM</SUP> clad fuel are also 
applicable to fuel with Optimized ZIRLO<SUP>TM</SUP> cladding. Ring 
compression tests performed by Westinghouse on Optimized 
ZIRLO<SUP>TM</SUP> demonstrate an acceptable retention of ductility up 
to 10 CFR 50.46 limits of 2200 [deg]F peak cladding temperature and 17 
percent total oxidation. Utilizing currently approved LOCA models and 
methods, Westinghouse will perform cycle-specific reload evaluations to 
ensure that the Optimized ZIRLO<SUP>TM</SUP> LTAs satisfy 10 CFR 50.46 
acceptance criteria.
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    \7\ Westinghouse Electric Company Topical Report, Addendum 1 to 
WCAP-12610-P-A and CENPD-404-P-A, ``Optimized ZIRLO'', February 
2003.
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    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 the Optimized ZIRLO<SUP>TM</SUP> LTA cladding for 
determining acceptable fuel performance. Metal-water reaction tests 
performed by Westinghouse on Optimized ZIRLO<SUP>TM</SUP> (documented 
in Appendix B of Addendum 1 to WCAP-12610-P-A) demonstrate conservative 
reaction rates relative to the Baker-Just equation. Thus, application 
of Appendix K, Paragraph I.A.5, in these circumstances, is not 
necessary for the licensee to achieve the underlying purpose of the 
regulation.
    Based upon the results of metal-water reaction tests and ring-
compression tests, which ensure the applicability of ECCS models and 
acceptance criteria and the use of approved LOCA models to ensure that 
the Optimized ZIRLO<SUP>TM</SUP> LTAs satisfy 10 CFR 50.46 acceptance 
criteria, the NRC staff finds it acceptable to grant an exemption from 
the requirements of 10 CFR 50.46 and Appendix K to 10 CFR part 50 for 
the use of up to eight LTAs in STP, Units 1 and 2.

3.3 Special Circumstances

    In summary, the NRC staff has reviewed the licensee's request for 
an exemption to allow up to eight LTAs containing fuel rods, guide 
thimble tubes, and instrumentation tubes fabricated with Optimized 
ZIRLO<SUP>TM</SUP> to be used in STP, Units 1 and 2. Based on the NRC 
staff's evaluation, as set forth above, the NRC staff considers that 
granting the proposed exemption will not defeat the underlying purpose 
of 10 CFR 50.46, or Appendix K to 10 CFR part 50. Accordingly, special 
circumstances, are present pursuant to 10 CFR 50.12(a)(2)(ii).

3.4 Other Standards in 10 CFR 50.12

    The NRC staff reviewed information provided by the licensee in 
References 1 and 2 to support the exemption request, and concluded that 
the use of Optimized ZIRLO<SUP>TM</SUP> would satisfy 10 CFR 50.12(a) 
as follows:
    (1) The requested exemption is authorized by law:
    No law precludes the activities covered by this exemption request. 
The Commission, based on technical reasons set forth in rulemaking 
records, specified the specific cladding materials identified in 10 CFR 
50.46 and 10 CFR part 50, Appendix K. Cladding materials are not 
specified by statute.
    (2) The requested exemption does not present an undue risk to the 
public health and safety. As stated by the licensee in Reference 1:

    The lead test assembly safety evaluation will ensure that these 
acceptance criteria are met following insertion of the assemblies 
containing Optimized ZIRLO<SUP>TM</SUP> material. Fuel assemblies 
using Optimized ZIRLO<SUP>TM</SUP> cladding will be evaluated using 
NRC-approved analytical methods and will address the changes in the 
cladding material properties. The safety analysis for the South 
Texas Project is supported by the applicable technical 
specifications. The South Texas Project reload cores containing 
Optimized ZIRLO<SUP>TM</SUP> cladding will continue to be operated 
in accordance with the operating limits specified in the technical 
specifications. Lead test assemblies using Optimized 
ZIRLO<SUP>TM</SUP> cladding will be placed in non-limiting core 
locations. Therefore, this exemption will not pose an undue risk to 
public health and safety.

    The NRC staff has evaluated these considerations as set forth in 
Section 3.1 and 3.2 of this Exemption. For the reasons set forth in 
Sections 3.1 and 3.2, the NRC staff concludes that Optimized 
ZIRLO<SUP>TM</SUP> may be used as a cladding material for up to eight 
LTAs to be placed in non-limiting core locations in STP, Units 1 and 2, 
and that an exemption from the requirements of 10 CFR 50.46 and 10 CFR 
part 50, Appendix K, does not pose an undue risk to the public health 
and safety.
    (3) The common defense and security are not affected and, 
therefore, not endangered by this exemption.

4.0 Conclusion

    Accordingly, 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 STPNOC an exemption from the 
requirements of 10 CFR part 50, Appendix K and Section 50.46, for the 
use of up to eight LTAs containing Optimized ZIRLO<SUP>TM</SUP> in STP, 
Units 1 and 2, up to a lead rod average burnup of 62,000 megawatt days 
per metric ton of uranium.
    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 (69 FR 45352).
    This exemption is effective upon issuance.

    For the Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 04-24493 Filed 11-2-04; 8:45 am]
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