[Federal Register Volume 68, Number 179 (Tuesday, September 16, 2003)]
[Notices]
[Pages 54246-54249]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-23556]
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NUCLEAR REGULATORY COMMISSION
[Docket No. STN 50-454]
Exelon Generation Company, LLC, Byron Station, Unit No. 1;
Environmental Assessment and Finding of No Significant Impact
The U.S. Nuclear Regulatory Commission (NRC) is considering
issuance of an exemption to Title 10 of the Code of Federal Regulations
(10 CFR) Part 50, for Facility Operating License No. NPF-37 issued to
Exelon Generation Company, LLC, (Exelon or the licensee), for operation
of the Byron Station, Unit No. 1, located in Ogle County, Illinois.
Therefore, pursuant to 10 CFR 51.21, the NRC is issuing this
environmental assessment and finding of no significant impact.
Environmental Assessment
Identification of Proposed Action
The proposed action would allow the use of a limited number of fuel
rods with ZIRLO\TM\ cladding that has a tin content lower than the
currently licensed tin content range for ZIRLO\TM\ in one lead test
assembly (LTA) (i.e., LTA M09E). The licensee has also requested
approval to irradiate two LTAs (i.e., M09E and M12E) that contain low-
tin ZIRLO\TM\ clad fuel rods and two ``standard'' Westinghouse 17x17
VANTAGE+ ZIRLO\TM\ assemblies (i.e., M10E and M11E) up to 69,000 MWD/
MTU for Byron, Unit 1 Cycle 13 (B1C13). The burnup limits are not part
of the technical specifications (TS), but are design bases limits for
the fuel cladding, and limit the current fuel rod-average burnup to
less than or equal to 60,000 MWD/MTU. The proposed action is in
accordance with the licensee's application dated January 17, 2003, as
supplemented by letter dated March 24, 2003. The licensee has indicated
that it intends to submit an amendment request with respect to an
increase in the rod-average burnup.
The Need for the Proposed Action
Available industry data indicates that corrosion resistance of
nuclear fuel cladding improves for cladding with a low tin content. The
optimum tin level provides a reduced corrosion rate while maintaining
the benefits of mechanical strength and resistance to accelerated
corrosion from abnormal chemistry conditions. In addition, fuel rod
corrosion/temperature feedback effects have become more limiting with
respect to fuel rod design criteria. By reducing the associated
corrosion buildup and, thus, minimizing temperature feedback effects,
additional margin to fuel rod internal pressure design criteria can be
obtained.
As part of a program to address these issues, Westinghouse Electric
Company (Westinghouse), has developed an LTA program in cooperation
with Exelon that includes ZIRLO\TM\ fuel cladding with a tin content
lower than the currently licensed range for ZIRLO\TM\. Use of fuel rods
using such low-tin cladding requires exemptions 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.''
In addition, the basis for approval of ZIRLO\TM\ cladding used in
the Byron core is provided in an NRC safety evaluation addressed to
Westinghouse, ``Acceptance for Referencing of Topical Report WCAP-
12610, `VANTAGE+ Fuel Assembly Reference Core Report,' '' dated July 1,
1991. The safety evaluation approved the use of the VANTAGE+ fuel
design that was described in WCAP-12610-P-A, and found its use
acceptable up to a rod-average burnup of 60,000 MWD/MTU. Use of the
VANTAGE+ fuel design in the Byron core beyond that burnup level has not
been approved yet because of uncertainty in changes in the gap-release
fraction associated with increasing fuel burnup. The present methods
for assessing fission gas releases have not been validated with actual
data at higher peak-rod burnups. Therefore, part of the Westinghouse
LTA program includes acquisition of actual operating data through the
limited use of fuel rods in the Byron Unit 1 core to obtain burnup
levels higher than 60,000 MWD/MTU that will be examined at the end of
the Byron Unit 1, Cycle 13 (B1C13) fuel cycle.
Two LTAs (i.e., LTA M09E and M12E) were in use in Byron Unit 2,
Cycle 10 (B2C10). These LTAs are composed of low-tin and standard
composition ZIRLO\TM\ cladding. The licensee modified one of the LTAs
(M09E) to include fresh fuel rods with ZIRLO\TM\ cladding that has a
tin content lower than that of the ZIRLO\TM\ cladding of the currently
licensed fuel. No fuel rods were replaced in LTA M12E. Both LTAs will
be used in Byron Unit 1 Cycle 13
[[Page 54247]]
(B1C13) in non-limiting core locations. In addition, the licensee
proposes to irradiate two standard 17x17 VANTAGE+ ZIRLO\TM\ assemblies
(i.e., M10E and M11E) in Byron, Unit 1 Cycle 13 (B1C13), also in non-
limiting core locations. At the end of B2C10, the approximate assembly
average burnup is expected to be 51,094 MWD/MTU for LTA M09E, 51,123
MWD/MTU for LTA M12E, 51,457 MWD/MTU for LTA M10E, and 51,423 MWD/MTU
for LTA M11E.
The licensee has requested that it (1) be authorized to use the
modified LTA M09E in Byron, Unit 1 Cycle 13 (B1C13) to obtain data on
both the use of low-tin ZIRLO\TM\ and high burnup operation (up to
69,000 MWD/MTU), and (2) be authorized to irradiate the other three
assemblies (M10E, M11E, and M12E) up to 69,000 MWD/MTU to obtain data
on the effects of high burnup operation. The proposed irradiation of
these fuel assemblies does not require a change to the TS; however;
this burnup will exceed the current design basis limit for the fuel
cladding of 60,000 MWD/MTU for peak fuel rod-average burnup.
Irradiation of these four LTAs to a higher burnup will provide data
on fuel and materials performance that will support industry goals of
extending the current fuel burnup limits and will provide additional
insight regarding gap-release fraction related to fuel performance
behavior at high burnups. The data will also help confirm the
applicability of nuclear design and fuel performance models at high
burnups.
Environmental Impacts of the Proposed Action
Background
In its previous environmental assessments concerning fuel burnup,
the Commission relied on the results of a study conducted for the NRC
by Pacific Northwest Laboratories. The results of the study were
documented in detail in the report, ``Assessment of the Use of Extended
Burnup Fuel in Light Water Power Reactors'' (NUREG/CR-5009, PNL-6258,
February 1988). The overall findings of this study showed there were no
significant adverse effects that would result from increasing the
batch-average burnup level of 33,000 MWD/MTU to 50,000 MWD/MTU or above
as long as the maximum rod average burnup level of any fuel rod was no
greater than 60,000 MWD/MTU. Furthermore, based on the above study and
the report, ``The Environmental Consequences of Higher Fuel Burn-up,''
(AIF/NESP-032), issued by the Atomic Industrial Forum, the NRC staff
concluded that the environmental impacts summarized in Table S-3 of 10
CFR 51.51 and in Table S-4 of 10 CFR 51.52 for a burnup level of 33,000
MWD/MTU are conservative and bound the corresponding impacts for burnup
levels up to 60,000 MWD/MTU and uranium-235 enrichments up to 5 percent
by weight.\1\
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\1\ See ``Extended Burnup Fuel Use in Commerical LWRs;
Environmental Assessment and Finding of No Significant Impact,'' 53
FR 6040, February 29, 1988.
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In this environmental assessment regarding the impacts of the use
of extended burnup fuel beyond 60,000 MWD/MTU, the Commission is also
relying on the results of an updated study conducted for it by the
Pacific Northwest National Laboratory (PNNL) entitled, ``Environmental
Effects of Extending Fuel Burnup Above 60 GWd/MTU,'' (NUREG/CR-6703,
PNNL-13257, January 2001). This report represents an update to NUREG/
CR-5009. Although the study evaluated the environmental impacts of high
burnup fuel up to 75,000 MWD/MTU, certain aspects of the review were
limited to evaluating the impacts of extended burnup up to 62,000 MWD/
MTU because of the need for additional data about the effect of
extended burn-up on gap-release fractions. During the study, all
aspects of the fuel-cycle were considered, from mining, milling,
conversion, enrichment and fabrication through normal reactor
operation, transportation, waste management, and storage of spent fuel.
Environmental Impacts
The NRC has completed its evaluation of the proposed action and
concludes that there are no significant environmental impacts
associated with (1) using LTA M09E with fuel rods composed of ZIRLO\TM\
cladding that has a tin content lower than the currently licensed tin
content range for ZIRLO\TM\, and (2) irradiating four fuel assemblies
(M09E, M10E, M11E, and M12E) to a burnup of 69,000 MWD/MTU. The
following is a summary of the staff's evaluation:
The extended burnup assemblies will have a different mix of fission
and activation product radionuclides than the rest of the core. The
activities of short-lived fission products will tend to remain constant
or decrease slightly, while activities associated with activation
products and actinides tend to increase with increasing burnup. As
discussed in Attachment 2 to the licensee's January 17, 2003, request,
although there are variations in core inventories of isotopes due to
extended burnup, there are no significant increases of isotopes that
are major contributors to accident doses. In addition, the four fuel
assemblies will only contribute a small variation in the isotopic
population of the entire core (193 assemblies). Thus, with extended
burnup of the four assemblies and their placement in non-limiting core
locations, no significant increase in the release of radionuclides to
the environment is expected during normal operation. In addition, no
change is being requested by Exelon in the licensed technical
specifications pertaining to allowed cooling-water activity
concentrations. If leakage of radionuclides from the extended burnup
fuel assemblies occurs during operation, then the radioactive material
is expected to be removed by the plant cooling water cleanup system.
Using the modified LTA M09E in B1C13 with low-tin ZIRLO\TM\
cladding and irradiating the four fuel assemblies to a burnup of 69,000
MWD/MTU will not result in changes in the operation or configuration of
the facility. There will be no change in the level of controls or
methodology used for processing radioactive effluents or handling solid
radioactive waste, nor will the proposal result in any change in the
normal radiation levels within the plant. Accordingly, the impacts on
workers and the general population would not be significant because of
the small radiological effect of the four extended-burnup assemblies.
Environmental Impacts of Potential Accidents
Accidents that involve the damage or melting of the fuel in the
reactor core and spent-fuel handling accidents were also evaluated in
NUREG/CR-6703. The accidents considered were a loss-of-coolant accident
(LOCA), a steam generator tube rupture, and a fuel-handling accident.
In addition, Exelon addressed both LOCA and non-LOCA events in
Attachment 2 to the January 17, 2003 request.
For LOCAs, the amount of radionuclides that would be released from
the core (1) is proportional to the amount of radionuclides in the core
and (2) is not significantly affected by the gap-release fraction. The
gap-release fraction is a small contribution to the amount of
radionuclides available for release when the fuel is severally damaged.
Any increase in the amount of some longer-lived radionuclides available
for release from the four LTAs (1) will be small and (2) will not
result in a significant increase in the overall core inventory of
radionuclides. Therefore, there would be no significant increase in the
previously calculated
[[Page 54248]]
dose from a LOCA and the dose would remain below regulatory limits.
The pressurized-water reactor (PWR) steam generator tube rupture
accident involves direct release of radioactive material from
contaminated reactor coolant to the environment. As discussed
previously, no change is being requested by Exelon in the licensed
technical specifications pertaining to allowed cooling-water activity
concentrations. The maximum coolant activity is regulated through
technical specifications that are independent of fuel burnup.
Therefore, the gap-release fraction does not significantly affect the
amount of radionuclides available for release during a steam generator
tube rupture. Therefore, there would be no significant increase in the
previously calculated dose from a steam generator tube rupture and the
calculated dose would remain below regulatory limits.
The scenario postulated to evaluate potential fuel-handling
accidents involves a direct release of gap activity to the environment.
The assumptions regarding gap activity are based on guidance in
Regulatory Guide 1.183, ``Alternative Radiological Source Terms for
Evaluating Design Basis Accidents at Nuclear Power Reactors'' and
NUREG-1465, ``Accident Source Terms for Light-Water Nuclear Power
Plants''; the gap activity consists primarily of the noble gases,
iodines, and cesiums. The only isotopes that contribute significant
fractions of the committed effective dose equivalent and thyroid doses
are \131\I and \134\Cs. Similarly, the only isotopes that contribute
significant fractions of the deep dose are \132\I and \133\Xe. The
inventory of iodine, the primary dose contributor, decreases with
increasing burnup. However, gap-release fraction increases as burnup
increases; this in turn, would increase the calculated dose from a fuel
handling accident involving one of the four assembles addressed in this
exemption. As discussed earlier and outlined in NUREG/CR-6703,
additional information is needed to assess the relationship between
gap-release fraction and burnup beyond 60,000 MWD/MTU to 75,000 MWD/
MTU. However, based on the trend of the gap-release fraction from
33,000 MWD/MTU to 60,000 MWD/MTU, the increase in gap-release fraction
as burnup increases from 60,000 MWD/MTU to 69,000 MWD/MTU is expected
to be small. Therefore, the staff concludes (1) that the increase in
the previously calculated dose resulting from a fuel-handling accident
involving one of the assemblies would not be significant and (2) that
the dose would remain below regulatory limits.
Environmental Impacts of Transportation
The environmental effects of incident-free spent fuel
transportation were also evaluated in NUREG/CR-6703. Incident-free
transportation refers to transportation activities in which shipments
of radioactive material reach their destination without releasing any
radioactive cargo to the environment. The vast majority of radioactive
shipments are expected to reach their destination without experiencing
an accident or incident, or releasing any cargo. The incident-free
impacts from these normal, routine shipments arise from the low levels
of radiation that are emitted externally from the shipping container.
Although Federal regulations in 10 CFR part 71 and 49 CFR Part 173
impose constraints on radioactive material shipments, some radiation is
not entirely shielded by the shipping container and exposes nearby
persons to low levels of radiation. Based on the analyses presented in
NUREG/CR-6703, the staff concludes that doses associated with incident-
free transportation of spent fuel with burnup to 75,000 MWD/MTU are
bounded by the doses given in 10 CFR 51.52, Table S-4, for all regions
of the country if dose rates from the shipping casks are maintained
within regulatory limits.
Additionally, the environmental effects of spent fuel
transportation accidents were also evaluated in NUREG/CR-6703. Accident
risks are the product of the likelihood of an accident involving a
spent-fuel shipment and the consequences of a release of radioactive
material resulting from the accident. The consequences of such a
transportation accident are represented by the population dose from a
release of radioactive material, given that an accident occurs that
leads to a breach in the shipping cask's containment systems. The
consequences are a function of the total amount of radioactive material
in the shipment, the fraction that escapes from the shipping cask, the
transport of radioactive material to humans, and the characteristics of
the exposed population. Considering the uncertainties in the data and
computational methods, the overall changes in transportation accident
risks due to increasing fuel burnup of the four fuel assemblies are not
significant. The calculated doses resulting from a spent fuel
transportation accident will remain below regulatory limits, and no
significant increase in the environmental effects of spent-fuel
transportation accidents are expected.
Non-Radiological Impacts
With regard to potential non-radiological impacts, the proposed
action does not have a potential to affect any historic sites. It does
not affect non-radiological plant effluents and has no other
environmental impact. Therefore, there are no significant non-
radiological environmental impacts associated with the proposed action.
Summary
Based on the staff's independent assessment discussed above, the
NRC concludes that there will be no significant environmental impacts
associated with (1) using LTA M09E with fuel rods composed of ZIRLO\TM\
cladding that has a tin content lower than the currently licensed tin
content range for ZIRLO\TM\, and (2) irradiating the four fuel
assemblies (M09E, M10E, M11E, and M12E) to a burnup of 69,000 MWD/MTU.
Environmental Impacts of the Alternatives to the Proposed Action
As an alternative to the proposed action, the staff considered
denial of the proposed action (i.e., the ``no action'' alternative).
Denial of the application would result in no change in current
environmental impacts. The environmental impacts of the proposed action
and the alternative action are similar. However, it would deny to the
licensee and the NRC operational data on low-tin content ZIRLO\TM\ and
the performance of fuel at extended burnup conditions.
Alternative Use of Resources
The action does not involve the use of any different resources than
those previously considered in the Final Environmental Statement for
the Byron Station, Unit Nos. 1 and 2, dated April 30, 1982.
Agencies and Persons Consulted
On July 9, 2003, the staff consulted with the Illinois State
official, Frank Niziolek, of the Illinois Department of Nuclear Safety,
regarding the environmental impact of the proposed action. The State
official had no comments.
Finding of No Significant Impact
On the basis of the foregoing environmental assessment, the NRC
staff concludes that (1) allowing use of an LTA (i.e., LTA M09E) with a
limited number of replacement fuel rods with ZIRLO\TM\ cladding that
has a tin content lower than the currently licensed tin content range
for ZIRLO\TM\, and (2) permitting irradiation of four fuel assemblies
(M09E, M10E, M11E, and
[[Page 54249]]
M12E) to a burnup of 69,000 MWD/MTU, will not have a significant effect
on the quality of the human environment. Accordingly, the NRC has
determined not to prepare an environmental impact statement for the
proposed actions.
For further details with respect to the proposed action, see the
licensee's letters dated January 17 and March 24, 2003. Documents may
be examined, and/or copied for a fee, at the NRC 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 of NRC's Web
site, http://www.nrc.gov (the Public Electronic Reading Room). If you
do not have access to ADAMS or if there are problems in accessing the
documents located in ADAMS, contact the NRC Public Document Room (PDR)
Reference staff at 1 (800) 397-4209, or (301) 415-4737, or by e-mail to
[email protected].
Dated at Rockville, Maryland, this 9th day of September, 2003.
For the Nuclear Regulatory Commission.
Anthony J. Mendiola,
Chief, Section 2, Project Directorate III, Division of Licensing
Project Management, Office of Nuclear Reactor Regulation.
[FR Doc. 03-23556 Filed 9-15-03; 8:45 am]
BILLING CODE 7590-01-P