[Federal Register Volume 69, Number 33 (Thursday, February 19, 2004)]
[Notices]
[Pages 7800-7801]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-3574]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-423]


Dominion Nuclear Connecticut, Inc., Millstone Power Station, Unit 
No. 3; Exemption

1.0 Background

    Dominion Nuclear Connecticut, Inc. (DNC or the licensee) is the 
holder of Facility Operating License No. NPF-49 which authorizes 
operation of Millstone Power Station, Unit No. 3 (MP3). 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 or the Commission) now or hereafter in effect. The 
facility consists of a pressurized water reactor located in Waterford, 
Connecticut.

 2.0 Request/Action

    Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 
section 50.12, ``Specific Exemptions,'' DNC, in a letter dated July 1, 
2003, as supplemented November 10, 2003, requested an 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.'' The regulation in 10 CFR 50.44 specifies requirements for the 
control of hydrogen gas generated after a postulated loss-of-coolant 
accident (LOCA) for reactors fueled with zircaloy or ZIRLOTM 
cladding. Section 50.46 of 10 CFR contains acceptance criteria for the 
emergency core cooling system (ECCS) for reactors fueled with zircaloy 
or ZIRLOTM 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. This 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 
ZIRLOTM fuel rod cladding. Thus, an exemption from the 
requirements of 10 CFR 50.44, 10 CFR 50.46, and Appendix K to 10 CFR 
Part 50 is needed to irradiate lead test assemblies (LTAs) comprised of 
a developmental alloy (Optimized ZIRLOTM) at MP3.

3.0 Discussion

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) Reduced tensile strength; (2) an increased 
thermal creep rate; (3) an increased irradiation growth rate; (4) a 
reduced [alpha] [rarr] [alpha] + [beta] phase transition temperature; 
and (5) an improved corrosion resistance. The stated reduction in tin 
content of Optimized ZIRLOTM 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 
ZIRLOTM will exhibit many material characteristics similar 
to those of the licensed ZIRLOTM.
    In response to a Request for Additional Information (RAI), DNC 
provided details of the planned post-irradiation examinations of the 
LTAs. Measured parameters 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 low tin alloy's performance, including the 
potential impacts of a 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 LTAs in MP3 
will remain well within the operating experience base and applicable 
licensed limits for ZIRLOTM.
    Utilizing currently-approved fuel performance and fuel mechanical 
design models and methods, DNC and Westinghouse will perform cycle-
specific reload evaluations to ensure that the LTAs satisfy design 
criteria.
    Based upon LTA irradiation experience of similar low tin versions 
of ZIRLOTM, expected performance due to similar material 
properties, and an extensive LTA post-irradiation examination program 
aimed at qualifying model predictions, the staff finds the LTA 
mechanical design acceptable for MP3.
3.1.2 Core Physics and Non-LOCA Safety Analysis
    The MP3 exemption request relates solely to the specific types of 
cladding material specified in the regulations. Due to similar material 
properties, any impact of Optimized ZIRLOTM 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, DNC 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 response to an RAI, DNC described how 
power-peaking margins 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 staff finds that the irradiation of up to eight LTAs in 
MP3 will not result in unsafe operation or violation of specified 
acceptable fuel design limits. Furthermore, in the event of a design-
basis accident, these LTAs will not promote consequences beyond those 
currently analyzed. Based upon 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 LTAs satisfy 10 CFR 50.46 acceptance criteria, the 
staff considers the LTAs acceptable for use at MP3 as proposed by DNC.

3.2 Regulatory Evaluation

    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 if: (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.
3.2.1 10 CFR 50.44
    The underlying 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 licensee has provided means for controlling 
hydrogen gas and has previously considered the potential for hydrogen 
gas generation stemming from a metal-water reaction. The LTA rods of 
Optimized ZIRLOTM cladding are similar in chemical 
composition to

[[Page 7801]]

zircaloy cladding. Metal-water reaction tests performed by Westinghouse 
on Optimized ZIRLOTM (documented in Appendix B of Addendum 1 
to WCAP-12610-P-A) demonstrate comparable reaction rates. Accordingly, 
the previous calculations of hydrogen production resulting from a 
metal-water reaction will not be significantly changed. Granting the 
proposed exemption will not defeat the underlying purpose of 10 CFR 
50.44.
3.2.2 10 CFR 50.46
    The underlying purpose of 10 CFR 50.46 is to establish acceptance 
criteria for ECCS performance. The applicability of the ECCS acceptance 
criteria has been demonstrated by Westinghouse. Ring compression tests 
performed by Westinghouse on Optimized ZIRLOTM (documented 
in Appendix B of Addendum 1 to WCAP-12610-P-A) demonstrate an 
acceptable retention of ductility up to 10 CFR 50.46 limits of 2200 
[deg]F and 17% Equivalent Cladding Reacted (ECR).
    Utilizing currently approved LOCA models and methods, Westinghouse 
will perform cycle-specific reload evaluations to ensure that the LTAs 
satisfy 10 CFR 50.46 acceptance criteria. Granting the proposed 
amendment will not defeat the underlying purpose of 10 CFR 50.46.
3.2.3 10 CFR Part 50, Appendix K
    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 LTA cladding for determining acceptable fuel 
performance. Metal-water reaction tests performed by Westinghouse on 
Optimized ZIRLOTM (documented in Appendix B of Addendum 1 to 
WCAP-12610-P-A) demonstrate conservative reaction rates relative to the 
Baker-Just equation. Granting the proposed exemption will not defeat 
the underlying purpose of Appendix K, Paragraph I.A.5.
3.2.4 Special Circumstances
    In summary, the staff reviewed the licensee's request of proposed 
exemption to allow up to eight LTAs containing fuel rods, guide thimble 
tubes, and instrumentation tubes fabricated with Optimized 
ZIRLOTM. Based on the staff's evaluation, as set forth 
above, the staff considers that granting the proposed exemption will 
not defeat the underlying purpose of 10 CFR 50.44, 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).
3.2.5 Other Standards in 10 CFR 50.12
    The staff examined the rest of the licensee's rationale to support 
the exemption request, and concluded that the use of Optimized 
ZIRLOTM 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 
50.44, 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:

    The LTA reload evaluation will ensure that these acceptance 
criteria [in the Commission's regulations] are met following the 
insertion of LTAs containing Optimized ZIRLOTM material. 
Fuel assemblies using Optimized ZIRLOTM cladding will be 
evaluated using NRC-approved analytical methods and plant specific 
models to address the changes in the cladding material properties. 
The safety analysis for Millstone, Unit No. 3 is supported by the 
applicable technical specification. The Millstone, Unit No. 3 reload 
cores containing Optimized ZIRLOTM cladding are required 
to be operated in accordance with the operating limits specified in 
the technical specifications. As required by the technical 
specifications, the LTAs utilizing Optimized ZIRLOTM 
cladding will be placed in non-limiting core locations. Thus, the 
granting of this exemption request 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 of this exemption. For the reasons set forth in that 
Section, the staff concludes that Optimized ZIRLOTM may be 
used as a cladding material for no more than eight LTAs to be placed in 
non-limiting core locations during MP3's next refueling outage, and 
that an exemption from the requirements of 10 CFR 50.44, 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 requested exemption will not endanger the common defense 
and security:
    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 DNC an exemption from the 
requirements of 10 CFR 50.44, 10 CFR 50.46, and 10 CFR Part 50, 
Appendix K, to allow the use of Optimized ZIRLOTM as a 
cladding material in eight LTAs in the capacity described in their July 
1, 2003 submittal, as supplemented November 10, 2003, up to a lead rod 
average burnup of 62,000 MWD/MTU.
    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 75291).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 11th day of February 2004.

    For the Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 04-3574 Filed 2-18-04; 8:45 am]
BILLING CODE 7590-01-P