ML24207A032
| ML24207A032 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 09/13/2024 |
| From: | Bo Pham Plant Licensing Branch II |
| To: | |
| Mahoney, M NRR/DORL 415-3867 | |
| References | |
| Download: ML24207A032 (1) | |
Text
NUCLEAR REGULATORY COMMISSION
Docket Nos. 50-250 and 50-251
Florida Power and Light Company
Turkey Point Nuclear Generating, Unit Nos. 3 and 4
Exemption
I. Background.
Florida Power and Light Company (FPL, the licensee) is the holder of Renewed Facility
Operating License No s. DPR-31 and DPR-41, which authorize operation of Turkey Point
Nuclear Generating, Unit Nos. 3 and 4 (Turkey Point). 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) now or hereafter in effect. The facility consists of
pressurized-water reactors (PWRs) located in Miami -Dade County, Florida.
II. Request/Action.
By application dated November 15, 2023 (Agencywide Documents Access and
Management System (ADAMS) Accession No. ML23320A028), FPL, pursuant to Title 10 of the
Code of Federal Regulations (10 CFR), Section 50.12, Specific exemptions, requested an
exemption from certain requirements of 10 CFR 50.46, Acceptance criteria for emergency core
cooling systems for light-water nuclear power reactors, to use AXIOM fuel rod cladding at
Turkey Point.
The regulations in 10 CFR 50.46 are currently limited in applicability to the use of fuel
rods with zircaloy or ZIRLO ' cladding. This exemption will allow FPL to use AXIOM fuel rod
cladding at Turkey Point. The special circumstances associated with the exemption request are
that application of the regulation in this circumstance is not necessary to achieve the underlying
purpose of the rule.
III. Discussion.
The regulation in 10 CFR 50.46(a)(1)(i) states, in part, 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 loss-of-coolant accidents [LOCA] conforms to the criteria set forth in paragraph (b) of this section. ECCS cooling performance must be calculated in accordance with an acceptable evaluation model and must be calculated for a number of postulated loss -of-coolant accidents of different sizes, locations, and other properties sufficient to provide assurance that the most severe postulated loss -of-coolant, accidents are calculated.
Since 10 CFR 50.46 specifically refers to fuel with zircaloy or ZIRLO' cladding, its
application to fuel clads with materials other than zircaloy or ZIRLO' requires an exemption
from this section of the regulations.
The exemption request from the licensee relates solely to the types of fuel cladding
materials specified in these regulations. As written, the regulations presume the use of zircaloy
or ZIRLO' cladding. Thus,an exemption is necessary to apply 10 CFR 50.46 to cladding
materials (i.e., AXIOM), other than zircaloy or ZIRLO' cladding. The proposed request does
not exempt Turkey Point from any other requirements of 10 CFR 50.46 regarding acceptance
criteria,evaluation model features and documentation, reporting of changes or errors, etc.
Pursuant to 10 CFR 50.12, the NRC may, upon application by any interested person or
upon its own initiative, grant exemptions from requirements of 10 CFR part 50 when: (1) the
exemptions are authorized by law, will not present an undue risk to the public health and safety,
and are consistent with the common defense and security, and ( 2) special circumstances, as
defined in 10 CFR 50.12(a)(2), are present. The licensees proposed exemption request which
would permit application of the requirements of 10 CFR 50.46 to fuel rods clad with AXIOM at
Turkey Point identifies, in particular, that the special circumstance associated with this
exemption request is that the application of the regulation in this circumstance is not necessary
to achieve the underlying purpose of the rule.
The technical basis for the use of fuel cladding with AXIOM in PWRs is documented in
Topical Report (TR) WCAP-18546NP-A, Revision 0, Westinghouse AXIOM Cladding for Use
in Pressurized Water Reactor Fuel, dated March 2021 ( ML23089A066 ). This TR describes
Westinghouses evaluation for the use of the AXIOM alloy in PWR fuel assemblies as a
replacement for ZIRLO' and Optimized ZIRLO'. This TR discusses material properties of
AXIOM, as well as its behavior under normal operation, anticipated transients, and postulated
accident conditions.
As identified in TR WCAP-18546NP-A, Revision 0, the AXIOM alloy is a proprietary
niobium-bearing variant of zirconium. This material also has tin, vanadium, and copper as
alloying elements. Westinghouse stated that the AXIOM alloy was developed to provide
enhanced performance with respect to corrosion, hydrogen pickup, growth, and creep. While
demonstrating relevant differences in certain material properties and physical behavior, TR
WCAP-18546NP-A, Revision 0 identifies that the basic physical properties of AXIOM are
similar to ZIRLO'.
Sections 3.11, 3.12, and 6.2.1.4 of TR WCAP-18546NP-A, Revision 0 provide
Westinghouses rationale for concluding that each of the acceptance criteria in 10 CFR 50.46 is
applicable to fuel clad with AXIOM.
As documented in the NRC staff's SE on TR WCAP-18546 NP-A, Revision 0, the staff
concluded that the criteria of 10 CFR 50.46 are acceptable for application to AXIOM cladding.
The technical basis for the NRC staff s conclusions is the testing and analysis Westinghouse
performed in support of the AXIOM alloy is described in the NRC staff's relevant safety
evaluation. Despite finding application of 10 CFR 50.46 to AXIOM acceptable from a technical
perspective, current regulations in 10 CFR 50.46 are limited in applicability to the use of fuel
rods with zircaloy or ZIRLO' cladding; therefore, an exemption for use of a new cladding
material (such as AXIOM),is required.
A. The Exemption is Authorized by Law.
The NRC has the authority under 10 CFR 50.12 to grant exemptions from the
requirements of 10 CFR part 50 upon demonstration of proper justification. The fuel that will be
irradiated at Turkey Point is clad with a zirconium-based alloy that is not expressly within the
scope of 10 CFR 50.46. However, the NRC staff considers all other aspects of these regulations
(e.g., acceptance criteria, prescribed methods, reporting requirements) applicable to the
AXIOM cladding material, and the licensee states that it will ensure that these regulations are
satisfied for operation with fuel clad with AXIOM. As discussed below, the NRC staff
determined that special circumstances exist, which support granting the proposed exemption.
Furthermore, granting the exemption would not result in a violation of the Atomic Energy Act of
1954, as amended, or the NRCs regulations. Therefore, the exemption is authorized by law.
B. The Exemption Presents no Undue Risk to Public Health and Safety.
The NRC staffs previous review of TR WCAP-18546NP-A, Revision 0, which concerns
the properties of the AXIOM alloy, provides assurance that predicted chemical, thermal, and
mechanical characteristics of AXIOM-alloy cladding are acceptable under normal operation,
anticipated transients, and postulated accidents. The NRC staff finds that by utilizing the
methods and properties listed in the NRC -approved TR (i.e., TR WCAP -18546NP-A), the
licensee meets the acceptance criteria and analytical methods in 10 CFR 50.46 to 10 CFR p art
50, and thus, ensures acceptable safety margins for fuel clad with AXIOM that are consistent
with those the Commission has established for zircaloy and ZIRLO '. Turkey Point cores
involving AXIOM cladding will continue to be subject to the operating limits specified in the
technical specifications and core operating limits report. Thus, granting this exemption request
will not pose undue risk to public health and safety.
C. The Exemption is Consistent with the Common Defense and Security.
The exemption will allow the licensee to use an enhanced fuel rod cladding material
relative to the zircaloy material for which the requirements of 10 CFR 50.46 were originally
established. The NRC staff concludes that the use of AXIOM fuel rod cladding at Turkey Point
will not significantly affect plant operations and is therefore consistent with the common defense
and security. Further, the exemption does not involve security requirements and does not create
a security risk. Therefore, the exemption is consistent with the common defense and security.
D. Special Circumstances.
The regulations in 10 CFR 50.46 do not explicitly apply to fuel clad with AXIOM.
However, the underlying purpose of 10 CFR 50.46 is to provide requirements capable of
ensuring adequate core cooling during and after the most limiting postulated LOCA. As
discussed above, Westinghouse has demonstrated in an NRC -approved TR (i.e. TR WCAP-
18546NP-A) that application of the acceptance criteria and analytical methods required in 10
CFR 50.46 to fuel cladding with AXIOM is acceptable. For the maximum local oxidation limit in
50.46(b)(2), Westinghouse meets the 17 percent limit in the rule for cladding without any
hydrogen, but further justified the use of an alternative limit that the NRC finds acceptable for
maintaining post quench ductility during a postulated LOCA. The licensee stated in the
exemption request that the core reload safety analyses will be used to confirm on a cycle -
specific basis that there is no adverse impact on ECCS performance for Turkey Point.
Therefore, strict application of the material -specific requirements for fuel cladding in 10 CFR
50.46 is not necessary to achieve the underlying purpose of ensuring adequate core cooling in
this instance. Furthermore, granting an exemption to allow application of the balance of these
regulations for fuel cladding with AXIOM at Turkey Point would be consistent with the
underlying regulatory purpose.
E. Environmental Considerations.
The exemption requested by the licensee includes changes to requirements with respect
to installation or use of a facility component located within the restricted area. The NRC staff
determined that the exemption meets the eligibility criteria for the categorical exclusion set forth
in 10 CFR 51.22(c)(9) because the granting of this exemption involves: (i) no significant hazards
consideration, (ii) no significant change in the types or a significant increase in the amounts of
any effluents that may be released offsite, and (iii) no significant increase in individual or
cumulative occupational radiation exposure. Therefore, in accordance with 10 CFR 51.22(b), no
environmental impact statement or environmental assessment need be prepared in connection
with the NRCs consideration of this exemption request. The basis for the NRC staffs
determination of each of the requirements in 10 CFR 51.22(c)(9) is discussed below.
Requirements in 10 CFR 51.22(c)(9)(i)
The NRC staff evaluated the issue of no significant hazards consideration using the
standards described in 10 CFR 50.92(c), as presented below:
- 1. Does the proposed exemption involve a significant increase in the probability or
consequences of an accident previously evaluated?
Response: No.
The proposed exemption to allow the use of AXIOM fuel rod cladding does not involve
a significant increase in the probability or consequences of an accident previously evaluated.
For the set of previously evaluated accidents, their probability is governed by the failure
or malfunction of equipment or components other than the fuel rod cladding. The fuel rod
cladding itself is not an accident initiator and does not affect the accident probability. Therefore,
the change in fuel rod cladding material does not affect the probability of previously evaluated
accidents.
The proposed exemption does not involve a significant increase in the consequences of
previously evaluated accidents. This conclusion is demonstrated by the analysis submitted by
the licensee in support of the proposed use of AXIOM cladding that the NRC staff has
reviewed in support of the proposed license amendment. The licensees analysis shows that
fuel clad with AXIOM material performs comparably to fuel cladding materials that have been
used previously. This satisfies the acceptance criteria in 10 CFR 50.46(b) for the LOCA event.
Therefore, the proposed exemption does not involve a significant increase in the
probability or consequences of an accident previously evaluated.
- 2. Does the proposed exemption create the possibility of a new or different kind of accident
from any accident previously evaluated?
Response: No.
The use of AXIOM fuel rod cladding does not create the possibility of a new or different
kind of accident from any previously evaluated. The fuel rod cladding is not an accident initiator.
The use of AXIOM cladding has been assessed by the licensee and vendor, and it has been
found to exhibit comparable or enhanced behavior relative to Optimized ZIRCLO cladding
material specifically identified in 10 CFR 50.46. The NRC staff has previously reviewed this
information in its safety evaluation approving TR WCAP -18546NP-A. Use of Westinghouse fuel
with AXIOM cladding in the Turkey Point reactor core is compatible with the plant design and
does not introduce any new safety functions for plant structures, systems, or components.
Furthermore, the introduction of AXIOM cladding does not affect any accident mitigation
systems and does not introduce any new accident initiation methods.
Therefore, the proposed exemption does not create the possibility of a new or different
kind of accident from any previously evaluated.
- 3. Does the proposed exemption involve a significant reduction in a margin of safety?
Response: No.
The proposed exemption does not involve a significant reduction in the margin of safety.
The licensees analysis of the spectrum of postulated LOCA events for fuel rods clad with
AXIOM exhibits results comparable to those for the fuel currently in use at Turkey Point for the
small-break and the large-break LOCA events. Furthermore, the fuel vendor has generically
evaluated the performance of AXIOM cladding relative to the zircaloy cladding specifically
identified in 10 CFR 50.46. The vendor concluded that the performance of the AXIOM
cladding material is quite similar to or enhanced relative to Optimized ZIRCLO cladding material
The NRC staff has performed a review of these conclusions and documented in its safety
evaluation on TR WCAP -18546NP-A that the AXIOM material properties and mechanical
design methodology are in accordance with applicable regulations and regulatory guidance.
Therefore, the proposed exemption does not involve a significant reduction in a margin
of safety.
The NRC staff concludes that the proposed exemption presents no significant hazards
consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of no
significant hazards consideration is justified (i.e., satisfies the provision of
Requirements in 10 CFR 51.22(c)(9)(ii)
The proposed exemption would allow the use of AXIOM fuel rod cladding material in
the reactors. AXIOM cladding has similar properties and performance characteristics as the
currently licensed optimized ZIRLO cladding. Therefore, the use of the AXIOM fuel rod
cladding material will not significantly change the types of effluents that may be released offsite,
or significantly increase the amount of effluents that may be released offsite. Therefore, the
provision of 10 CFR 51.22(c)(9)(ii) is satisfied.
Requirements in 10 CFR 51.22(c)(9)(iii)
The proposed exemption would allow the use of the AXIOM fuel rod cladding material
in the reactors. AXIOM cladding has similar properties and performance characteristics as the
currently licensed optimized ZIRLO cladding. Therefore, the use of the AXIOM fuel rod
cladding material will not significantly increase individual occupational radiation exposure, or
significantly increase cumulative occupational radiation exposure. Therefore, the provision of 10
CFR 51.22(c)(9)(iii) is satisfied.
The NRC staff concludes that the proposed exemption meets the eligibility criteria for the
categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, in accordance with
10 CFR 51.22(b), no environmental impact statement or environmental assessment need be
prepared in connection with the NRCs proposed granting of this exemption.
IV. Conclusions.
Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12, 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 FPL an exemption from the specific
requirements of 10 CFR 50.46 for use of AXIOM fuel rod cladding.
Dated: September 13, 2024
For the Nuclear Regulatory Commission.
Bo M. Pham, Director, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation.