ML25289A274
| ML25289A274 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 10/16/2025 |
| From: | Dia K Nebraska Public Power District (NPPD) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| N132025053, 50.12 | |
| Download: ML25289A274 (1) | |
Text
N Nebraska Public Power District "ALwaSs therc when yu need us" N132025053 October 16,2025 50.12 Attention: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001
Subject:
Request for Exemption from 10 CFR 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors" Cooper Nuclear Station, Docket No. 50-298, Renewed License No. DpR-46 Pursuant to Title 10 of the Code of Federal Regulations (CFR), Section 50.12, Nebraska Public Power District (NPPD) requests an exemption from the provisions of 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors" for Cooper Nuclear Station (CNS). The requested exemption would permit insertion of a limited number of Global Nuclear Fuel (GNF) GNF4 Lead Use Assemblies with Nuclear Regulatory Commission (NRC) approved GNF-Ziron cladding material in lieu of GNF's traditional Zircaloy-2 cladding material, to be loaded co-resident with the currently licensed GNF2 fuel assemblies in the reactor core.
10 CFR 50.46 contains acceptance criteria for the emergency core cooling system for reactors that have fuel rods fabricated with zircaloy or ZIRLO fuel cladding material. By use of the GNF-Ziron cladding material, GNF4 fuel assemblies will not be aligned with the regulation. Therefore, an exemption from 10 CFR 50.46 is required for this cladding material to support the use of GNF-Ziron at CNS. This exemption request relates solely to the specific cladding material as identified in the regulation (fuel rods with zircaloy or ZIRLO cladding) and does not exempt CNS from other requirements of 10 CFR 50.46 or 10 CFR 50 Appendix K.
The attachment to this letter provides the technicaljustification for this request. The requested exemption from the specific requirements of 10 CFR 50.46 is permissible under 10 CFR 50.12 criteria because it is authorized by law, will not present an undue risk to the public health and safety, is consistent with the common defense and security, and special circumstances are present.
This exemption is needed to support CNS' next refueling outage currently scheduled to commence on September 26,2026. As such, NPPD requests approval of this exemption by March 31, 2026.
There are no regulatory commitments contained in this submittal.
Should you have questions regarding this submittal, please contact Linda Dewhirst, Regulatory Affairs and Compliance Manager, at (402) 825-5416.
COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-381 1 http:/iwww.nppd.com
N1S2025053 Page 2 of 2 Respectfully, Khalil Dia
/sn Aftachment: Exemption Request for Use of GNF-Ziron cladding Material cc:
Cooper Project Manager w/ attachment USNRC - NRR Plant Licensing Branch lV Regional Administrator Mattachment USNRC - Region lV Senior Resident lnspector dattachment USNRC - CNS NPG Distribution Mattachment CNS Records w/attachment
N132025053 Attachment Page 1 ofS ATTACHMENT Exemption Request for Use of GNF-Ziron Cladding Material Gooper Nuclear Station, Docket No. 50-298, Renewed License No. DPR-4G
N1S2025053 Attachment Page 2 ofS Exemption Request for Use of GNF4 Lead Use Assemblies with GNF-Ziron Cladding 1.0 PURPOSE Pursuant to Title 10 of the Code of Federal Regulations, (CFR) Section 50.12 [1], Nebraska Public Power District as license holder requests an exemption from the provisions of 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors" for the Cooper Nuclear Station (CNS). The requested exemption would permit insertion of a limited number of Global Nuclear Fuel Americas LLC (GNF)4 Lead Use Assemblies (LUAs) with Nuclear Regulatory Commission (NRC)-approved GNF-Ziron cladding material in lieu of GNF's traditional Zircaloy-2 cladding material, to be loaded co-resident with the currently licensed GNF2 fuel [2] assemblies in the reactor core. The regulation in 10 CFR 50.46 contains acceptance criteria for the emergency core cooling system (ECCS) for reactors that have fuel rods fabricated with zircaloy or ZIRLO fuel cladding material. By use of the GNF-Ziron cladding material, it is understood that the GNF4 fuel assemblies will not be aligned with the regulation.
Therefore, an exemption from 10 CFR 50.46 is required for this cladding material to support the use of GNF-Ziron at CNS. This exemption request relates solely to the specific cladding material as identified in the regulation (fuel rods with zircaloy or ZIRLO cladding) and does not exempt CNS from other requirements of 10 CFR 50.46 or 10 CFR 50 Appendix K.
2.0 BACKGROUND
Advances in components of nuclear fuel applications improves the performance, economics and safety of plant operation. Relative to the reactor core, development effort has resulted in evolving the fuel bundle design via enhanced configuration and materials. GNF4 fuel is the latest generation fuel product design under development by Global Nuclear Fuel Americas LLC.
A feature of the GNF4 design is a change from Zircaloy-2 to GNF-Ziron for fuel cladding.
lmprovement in cladding corrosion performance under normal operating conditions, which provides margins to numerous fuel design limits, is the motivation for this change.
Licensing for GNF fuel bundle designs is completed via the NRO-approved GESTAR ll methodology [3]. Based on demonstration of continued compliance to the several regulatory limits and criteria, this approach is allowed via the regulatory process of 10 CFR 50.59 [4]. Table 2-1 of the GESTAR ll document states that an exemption to 10 CFR 50.46 and 10 CFR 50 Appendix K is required for application of GNF-Ziron cladding outside of the Lead Test Assembly (LTA) provisions described in Appendix B [3].
Supporting development of GNF4, LUAs of this bundle design are proposed for insertion into CNS reactor core. ln-service observation and inspection of the LUAs will confirm expected performance and benefits. Licensing of the LUAs constitutes a "change, test or experiment" as determined acceptable via the same regulatory provisions of 10 CFR 50.59. This demonstration of acceptability for the LUAs is then incorporated into the standard reload process of GESTAR ll along with the balance of the reload core as to meeting fuel and core design criteria.
Not addressed by this licensing process is the definition of applicability for the ECCS requirements of 10 CFR 50.46 as stated above. For the application of GNF-Ziron material - not seen as included in the regulation - the current request for exemption is in order.
N1S2025053 Attachment Page 3 ofS 3.0 TECHNICAL JUSTIFICATION OF ACCEPTABILITY GNF-Ziron material is NRC-approved for use in Boiling Water Reactor fuel via NEDC-33353P-A
[5]. The approvalwas based on observed similarity to Zircaloy-2 material for features such as composition and microstructure, materialand thermal properties, and finding analytical methods conservative and suitable to demonstrate adequate performance under conditions of normal operation, anticipated operationaloccurrences, and design basis accidents. Demonstrating compliance of GNF-Ziron to regulatory requirements with models based on zircaloy was shown to be suitable and acceptable. The topical report concludes that this approach is acceptable under the GESTAR ll process for general application.
For ECCS-Loss of Coolant Accident (LOCA) analyses, the basis on which GNF-Ziron was approved included observation and testing demonstrating that effects relevant to a postulated LOCA event, such as cladding rupture, embrittlement and potential fragmentation, ballooning and blockage, fuel assembly damage and continued post-accident coolability, were acceptable.
Also, current models and analysis applications were concluded to be conservative and acceptable [6].
The reference for GNF-Ziron [5] also reports an extensive testing program, assessing GNF-Ziron in multiple plants and fuel design configurations.
The conclusion of the NRC review for GNF-Ziron was that it was a suitable substitute or replacement for Zircaloy-2. As such, no technical issue is noted which would preclude its exemption from the stipulation of the regulation as being applicable for plants with zircaloy or ZIRLO fuel.
4.0 JUSTIFICATION OF EXEMPTION 10 CFR 50.12 [1] allows exemptions to regulations as granted by the NRC. Exemptions may be granted an applicant based on two criteria: (1) 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; and (2) special circumstances are present. The requested exemption to allow the use of assemblies with GNF-Ziron cladding material meets these criteria.
Criterion 1 This exemption is authorized by law. The specification of cladding material in 10 CFR 50.46 was adopted at the discretion of the NRC consistent with its statutory authority and reflected material options common for fuel at the time of enactment. No statute drives or requires the NRC to stipulate material type in this instance. Nor is there any statutory prohibition against alternate, new or advanced materials, so long as suitability can be demonstrated. The stipulation of cladding material in this instance is viewed as an artifact of the regulation. No exemption is requested from the requirements for an acceptable evaluation model nor the acceptance criteria of 10 CFR 50.46. The intent of this request is solely to allow the use of the GNF-Ziron material as it is not explicitly referenced by 10 CFR 50.46.
The GNF-Ziron material is shown by the technical evaluation to perform comparably with the zircaloy material as historically applied. By this determination, this exemption will not create an
N152025053 Attachment Page 4 of5 undue risk to public health and safety, nor create any challenge to common defense and security, compared to current, approved applications.
Criterion 2 The cited regulation states that the NRC will not consider granting an exemption to the regulations unless special circumstances are present. This exemption request meets the special circumstance criteria in two ways:
10 CFR 50.12(a)(2)(ii), "Application of the regulation in the particular circumstances would not serue the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule."
For assemblies with GNF-Ziron cladding material, stipulation of the cladding material -
otherurise omitting an alternate, advanced material - is not necessary to achieve the underlying purpose of the10 CFR 50.46 rule, which regulates adequacy of the required ECCS system and analytical models.
10 cFR 50.12(a)(2)(vi), "Thereis presenf any other material circumstance not considered when the regulation was adopted for which it would be in the pubtic interest to grant an exemption."
a As noted above, the 10 CFR 50.46 rule was written mentioning common cladding materials at the time of enactment. The "other material circumstance" of improved cladding materials becoming available was not considered when adopted. lmproved operation while still supporting consistent or enhanced safety standards would serve the public interest for licensed plants.
10 CFR 50.46 identifies acceptance criteria for ECCS performance. GNF has performed an evaluation of ECCS-LOCA methods as part of the topical report [5]. Plant specific evaluation upon application will ensure that fuel bundles with GNF-Ziron cladding material meet all ECCS-LOCA acceptance criteria. The need for this exemption was anticipated prior to the approved GNF-Ziron report (Sec. 3.3.7.1) [5], and acknowledged by NRC in the ensuing Safety Evaluation:
"The current wording and interpretation of the criteria in 10 CFR 50.46 and Part 50 Appendix K requires an exemption for GNF-Ziron prior to use in a given plant."
5.0 coNcLUStoN The 10 CFR 50.46 regulation is currently limited in applicability to the use of fuel rods with zircaloy or ZIRLO cladding. 10 CFR 50.46 does not consider the proposed use of GNF-Ziron due to its composition being outside of zircaloy or ZIRLO material specification. With the approval of this exemption request, 10 CFR 50.46 can be applied adequately to bundles made with GNF-Ziron cladding material.
To support the use of GNF-Ziron cladding material in GNF4 LUAs, an exemption from the requirements of 10 CFR 50.46 is requested. The acceptability of GNF-Ziron cladding has been established in the generically approved Topical Report [5] and the plant specific application will show compliance with the acceptance criteria of the regulation. Considering 10 CFR 50.12, the
N1S2025053 Attachment Page 5 of5 requested exemption conforms to the criteria on which an exception may be granted.
6.0 REFERENCES
t1] 10 CFR 50.12, "Specific exemptions.", (Last Reviewed/Updated, March 24,2021) l2l NEDC-33270. 'GNF2 Advantage Generic Compliance with NEDE-24011-P-A (GESTAR ll)", Revision 11, August,2020. (ML171134086) t3l NEDE-24011-P-A-32, "General Electric Standard Application for Reactor Fuel (GESTAR ll)", Revision 32, August2O24. (ML24243A028) t4l 10 CFR 50.59, "Changes, tests and experiments" (Last Reviewed/Updated, January 29, 2025) tsl NEDC-33353P-A, "Application of GNF-Ziron to GNF Fuel Designs," Revision 1, April 2019 (M119100A260) 161 NEDE-23785-1-PA:
- a. Vol. l, Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident, Volume l, GESTR-LOCA - A Model for the Prediction of Fuel Rod Thermal Performance," General Electric Company, October 1984.
- b. Vol. ll, Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident, Volume ll, SAFER - Long Term lnventory Modelfor BWR Loss-of-Coolant Analysis," General Electric Company, October 1984.
- c. Vol. lll, Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident, Volume lll, SAFERyGESTR Application Methodology,"
General Electric Company, October 1984