[Federal Register Volume 66, Number 93 (Monday, May 14, 2001)]
[Notices]
[Pages 24409-24410]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-12035]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-289]
Amergen Energy Company, LLC, Three Mile Island Nuclear Station,
Unit 1; Exemption
1.0 Background
AmerGen Energy Company, LLC (the licensee or AmerGen) is the holder
of Facility Operating License No. DPR-50 which authorizes operation of
the Three Mile Island Nuclear Station, Unit 1 (TMI-1). 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
Dauphin County in Pennsylvania.
2.0 Purpose
Title 10 of the Code of Federal Regulations (10 CFR), Part 50,
Section 50.44, ``Standards for combustible gas control system in light-
water-cooled power reactors,'' requires, among other items, that 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 that section, include means
for control of hydrogen gas that may be generated, following a
postulated loss-of-coolant accident (LOCA) by--(1) Metal-water reaction
involving the fuel cladding and the reactor coolant, (2) Radiolytic
decomposition of the reactor coolant, and (3) Corrosion of metals.
Section 50.46, ``Acceptance criteria for emergency core cooling
systems for light-water nuclear power reactors,'' requires, among other
items, that 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 LOCAs conform to the criteria set
forth in paragraph (b) of that section. ECCS cooling performance must
be calculated in accordance with an acceptable evaluation model and
must be
[[Page 24410]]
calculated for a number of postulated LOCAs of different sizes,
locations, and other properties sufficient to provide assurance that
the most severe postulated LOCAs are calculated.
Appendix K of Part 50, ``ECCS Evaluation Models,'' requires, among
other items, that the rate of energy release, hydrogen generation, and
cladding oxidation from the metal/water reaction shall be calculated
using the Baker-Just equation (Baker, L., Just, L.C., ``Studies of
Metal Water Reactions at High Temperatures, III. Experimental and
Theoretical Studies of the Zirconium-Water Reaction,'' ANL-6548, page
7, May 1962) and implicitly assumes that either zircaloy or ZIRLO shall
be used as the fuel rod cladding material.
Sections 50.44, and 50.46, and Appendix K of 10 CFR Part 50, make
no provisions for use of fuel rods clad with other than zircaloy or
ZIRLO. The licensee has requested the use of Framatome Cogema Fuels
(FCF) ``M5'' advanced alloy for fuel rod cladding for the TMI-1 Cycle
14 operation. In order to accommodate the high fuel rod burnups that
are required for today's modern fuel management schemes and core
designs, FCF developed the M5 advanced fuel rod cladding and fuel
assembly structural material. The M5 alloy is a proprietary zirconium-
based alloy comprised of primarily zirconium (~99 percent) and niobium
(~1 percent). The elimination of tin has resulted in superior corrosion
resistence and reduced irradiation induced growth relative to both
standard Zircaloy and low-tin Zircaloy. The addition of niobium
increases ductility. Since the chemical composition of the M5 alloy
differs from the specifications of Zircaloy or ZIRLO, a plant-specific
exemption is required to allow the use of the M5 alloy as a fuel rod
cladding material at TMI-1. The M5 would also be used for fuel assembly
spacer grids, fuel rod end plugs and fuel assembly guide and instrument
tubes.
3.0 Discussion
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, 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. Special circumstances are
present whenever application of the regulations 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 Section 50.46 is to ensure that
facilities have adequate acceptance criteria for ECCS. FCF demonstrated
in its topical report, BAW-10227P-A, ``Evaluation of Advanced Cladding
and Structural Material (M5) in PWR Reactor Fuel,'' dated September 30,
1997, and approved on February 4, 2000, that the effectiveness of the
ECCS will not be affected by a change from zircaloy fuel rod cladding
to M5 fuel rod cladding. The analysis described in BAW-10227P-A also
concludes that the ECCS acceptance criteria applied to reactors fueled
with zircaloy fuel are also applicable to reactors fueled with M5 fuel
rod cladding.
The underlying purposes of Section 50.44 and Appendix K, paragraph
I.A.5, are to ensure that cladding oxidation and hydrogen generation
are appropriately limited during a LOCA and conservatively accounted
for in the ECCS evaluation model. Specifically, Appendix K requires
that the Baker-Just equation be used in the ECCS evaluation model to
determine the rate of energy release, cladding oxidation, and hydrogen
generation. In BAW-10227P-A, FCF demonstrated that the Baker-Just model
is conservative in all post-LOCA scenarios with respect to the use of
M5 advanced alloy as fuel rod cladding material. The licensee has
stated that the amount of hydrogen generated in an M5-clad core will
remain within the TMI-1 design basis. The NRC staff has reviewed the
FCF's advanced cladding and structural material, M5, for pressurized
water reactor fuel mechanical designs as described in BAW-10227P-A. In
its February 4, 2000, safety evaluation, the NRC staff concluded that,
to the extent specified and with limitations noted in the NRC staff's
evaluation, the assumptions related to M5 material properties and
mechanical design methodology are acceptable for referencing in fuel
reload licensing applications. The NRC staff has determined that since
the licensee and FCF have ongoing processes which assure that LOCA
analysis input values for peak cladding temperature-sensitive
parameters bound the as-operated plant values for those parameters at
TMI-1 and also have ongoing processes to determine mixed-core penalties
as needed, the methodologies and analyses described in BAW-10227P-A
apply to TMI-1 and the plant can be safely operated within the bounds
of those analyses with mixed- and full-core loadings of M5 clad fuel
and other M5 core structures. The NRC staff further concluded that
since fuel assemblies which utilize the two different alloys (M5 and
zircaloy) and which will be co-resident in the core have only slight
geometry differences, there will be virtually no thermal-hydraulic
effect, and a mixed core penalty in LOCA evaluations would not have to
be assessed to compensate for the material differences. Therefore,
based on the information described above, the NRC staff has determined
that the underlying purposes of Section 50.44, and 50.46, and Appendix
K of 10 CFR Part 50 have been achieved through the use of M5 advanced
alloy as fuel rod cladding material and core structure material, and
that the special circumstances required by 10 CFR 50.12(a)(2)(ii) for
granting exemptions from 50.44, and 50.46, and Appendix K of 10 CFR
Part 50 exist.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a)(ii), 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 AmerGen Energy Company, LLC, an
exemption from the requirements of 10 CFR 50.44, 10 CFR 50.46, and
Appendix K to 10 CFR Part 50, for Three Mile Island Nuclear Station,
Unit 1, as to the use of M5 cladding and core structures in lieu of
Zircaloy or ZIRLO as currently specified or implied in those
regulations.
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 23279).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 8th day of May 2001.
For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. 01-12035 Filed 5-11-01; 8:45 am]
BILLING CODE 7590-01-P