ML12025A162

Federal Register Notice - Exemption Regarding Use of M5 Alloy Fuel Rod Cladding

ML12025A162
Person / Time
Site:	Harris
Issue date:	02/24/2012
From:	Marilyn Evans Plant Licensing Branch II
To:
Billoch-Colon, Araceli
References
TAC ME5410, NRC-2012-0034
Download: ML12025A162 (6)

Text

[7590-01-P]

NUCLEAR REGULATORY COMMISSION

[NRC-2012-0034; Docket No. 50-400]

Carolina Power & Light Company Shearon Harris Nuclear Power Plant, Unit 1 Exemption

1.0 BACKGROUND

Carolina Power & Light Company, the licensee, doing business as Progress Energy Carolinas Inc., is the holder of Renewed Facility Operating License No. NPF-63, which authorizes operation of the Shearon Harris Nuclear Power Plant (HNP), Unit 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 one pressurized-water reactor (PWR) located in New Hill, North Carolina.

2.0 REQUEST/ACTION Title 10 of the Code of Federal Regulations (10 CFR) 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 loss-of-coolant accidents (LOCAs) conforms to the criteria set forth in paragraph (b) of this section. Appendix K to 10 CFR 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. The

regulations of 10 CFR 50.46 and 10 CFR Part 50, Appendix K, make no provisions for use of fuel rods clad in a material other than zircaloy or ZIRLO.

The licensee intends to load the M5TM cladding fuel assemblies into the core of HNP, Unit 1 during Refueling Outage 17, currently scheduled for spring 2012. The AREVA fuel design consists of low enriched uranium oxide fuel within M5TM zirconium alloy cladding. Since the chemical composition of the M5TM alloy differs from the specifications for zircaloy or ZIRLO, a plant-specific exemption is required to allow the use of the M5TM alloy as a cladding material or in other assembly structural components. Therefore, by letter dated January 19, 2011 (Agencywide Documents Access and Management System Accession No. ML110250473), the licensee requested an exemption from the requirements of 10 CFR 50.46 and Appendix K to 10 CFR Part 50 in order to use the fuel rods clad with AREVAs M5TM alloy.

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.

Authorized by Law This exemption would allow the use of M5TM advanced alloy, in lieu of zircaloy or ZIRLO, for fuel rod cladding in fuel assemblies at HNP, Unit 1. As stated above, 10 CFR 50.12 allows the NRC to grant exemptions from the requirements of 10 CFR 50.46 and Appendix K to 10 CFR Part 50. The NRC staff has determined that granting of the licensees proposed exemption will not result in a violation of the Atomic Energy Act of 1954, as amended, or the Commissions regulations. Therefore, the exemption is authorized by law.

No Undue Risk to Public Health and Safety The underlying purposes of 10 CFR 50.46 and 10 CFR Part 50, Appendix K, are to ensure that facilities have adequate acceptance criteria for the ECCS, and to ensure that cladding oxidation and hydrogen generation are appropriately limited during a LOCA and conservatively accounted for in the ECCS evaluation model, respectively. Topical Reports (TRs) BAW-10227(P)-A, Evaluation of Advanced Cladding and Structural Material (M5) in PWR Reactor Fuel, which was approved by the NRC in February 2000, and BAW-10240(P)-A, Incorporation of M5 Properties in Framatome ANP Approved Methods, which was approved by the NRC in May 2004, demonstrated that the effectiveness of the ECCS will not be affected by a change from zircaloy to M5TM. In addition, the TRs also demonstrated that the Baker-Just equation (used in the ECCS evaluation model to determine the rate of energy release, cladding oxidation, and hydrogen generation) is conservative in all post-LOCA scenarios with respect to the use of M5TM advanced alloy as a fuel rod cladding material or in other assembly structural components. Based on the above, no new accident precursors are created by using M5TM advanced alloy, thus, the probability of postulated accidents is not increased. Also, based on the above, the consequences of postulated accidents are not increased. In addition, the licensee will use NRC-approved methods for the reload design process for HNP Unit 1 reloads with M5TM. Therefore, there is no undue risk to public health and safety due to using M5TM.

Consistent with Common Defense and Security The proposed exemption results in changes to the operation of the plant by allowing the use of the M5TM alloy as fuel cladding material or in other assembly structural components in lieu of zircaloy or ZIRLO. This change to the fuel material used in the plant has no relation to security issues. Therefore, the common defense and security are not impacted by this exemption request.

Special Circumstances Special circumstances, in accordance with 10 CFR 50.12, are present whenever application of the regulation 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. In this circumstance neither 10 CFR 50.46 nor 10 CFR Part 50, Appendix K, explicitly allows the use of M5TM as a fuel rod cladding material or in use of other assembly structural components.

The underlying purpose of 10 CFR 50.46 is to ensure that facilities have adequate acceptance criteria for the ECCS. The staffs review and approval of TR BAW-10227(P)-A addressed all of the important aspects of M5TM with respect to ECCS Performance Requirements: (1) applicability of 10 CFR 50.46(b) fuel acceptance criteria, (2) M5TM material properties including fuel rod ballooning and rupture strains, and (3) steam oxidation kinetics and applicability of Baker-Just weight gain correlation. A subsequent NRC-approved TR, BAW-10240(P)-A, further addressed M5TM material properties with respect to LOCA applications.

The underlying purpose of 10 CFR Part 50, Appendix K, paragraph I.A.5, is to ensure that cladding oxidation and hydrogen generation are appropriately limited during a LOCA and conservatively accounted for in the ECCS evaluation model. 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 TR BAW-10227(P)-A, Framatome demonstrated that the Baker-Just model is conservative in all post-LOCA scenarios with respect to the use of the M5TM advanced alloy as a fuel rod cladding material or in other assembly structural components, and that the amount of hydrogen generated in an M5TM core during a LOCA will remain within the HNP Unit 1 design basis.

The M5TM 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 resistance and reduced irradiation-induced growth relative to both standard zircaloy (1.7 percent

tin) and low-tin zircaloy (1.2 percent tin). The addition of niobium increases ductility, which is desirable to avoid brittle failures.

The NRC staff has reviewed the licensee's advanced cladding material, M5TM, for PWR fuel mechanical designs as described in TR BAW-10227(P)-A. In the safety evaluation for TR BAW-10227(P)-A, the staff concluded that, to the extent specified in the staff's evaluation, the M5TM properties and mechanical design methodology are acceptable for referencing in fuel reload licensing applications. Application of the requirements of 10 CFR 50.46 and 10 CFR Part 0 Appendix K, paragraph I.A. 5 is not necessary to achieve their underlying purpose. The underlying purposes of 10 CFR 50.46 and 10 CFR Part 50, Appendix K, paragraph I.A.5 are achieved through the use of the M5TM advanced alloy as a fuel rod cladding material or in other assembly structural components. Thus, the special circumstances required by 10 CFR 50.12(a)(2)(ii) for the granting of an exemption from 10 CFR 50.46 and 10 CFR Part 50, Appendix K, exist.

Summary The NRC staff has reviewed the licensee's request to use the M5TM advanced alloy for fuel rod cladding and in other assembly structural components in lieu of zircaloy or ZIRLO.

Based on the NRC staff's evaluation, as set forth above, the NRC staff concludes that the exemption is authorized by law, will not present an undue risk to public health and safety, and is consistent with the common defense and security. In addition, the NRC staff concludes that the application of 10 CFR 50.46 and 10 CFR Part 50, Appendix K, is not necessary to achieve the underlying purpose of the regulations. Therefore, pursuant to 10 CFR 50.12(a), the NRC staff concludes that the use of the M5TM advanced alloy for fuel rod cladding and in other assembly structural components is acceptable and the exemption from 10 CFR 50.46 and 10 CFR Part 50, Appendix K, is justified.

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 the licensee an exemption from the requirements of 10 CFR 50.46 and 10 CFR Part 50, Appendix K, for HNP Unit 1.

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 (February 15, 2012; 77 FR 8903). This exemption is effective upon issuance.

Dated at Rockville, Maryland, this 24th day of February 2012.

FOR THE NUCLEAR REGULATORY COMMISSION

/RA/

Michele G. Evans, Director Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation