Entergy Operations, Inc. (Entergy or the licensee) is the holder of Facility Operating License No. NPF-38 which authorizes operation of Waterford Steam Electric Station, Unit 3 (Waterford 3). 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 or the Commission) now or hereafter in effect. The facility consists of a pressurized water reactor located in St. Charles Parish, Louisiana.
Pursuant to title 10 of the Code of Federal Regulations (10 CFR) section 50.12, “Specific Exemptions,” Entergy, in a letter dated April 30, 2004, as supplemented by letter dated June 8, 2004, requested an exemption to 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.” The regulation in 10 CFR 50.46 contains acceptance criteria for the emergency core cooling system (ECCS) for reactors fueled with zircaloy or ZIRLOTM cladding. Appendix K to 10 CFR part 50 requires that the Baker-Just equation be used to predict the rates of energy release, hydrogen concentration, and cladding oxidation from the metal-water reaction. This exemption request relates solely to the specific types of cladding material specified in these regulations. As written, the regulations presume the use of zircaloy or ZIRLOTM fuel rod Start Printed Page 47466cladding. Thus, an exemption from the requirements of 10 CFR 50.46 and Appendix K to 10 CFR part 50 is needed to irradiate lead test assemblies (LTAs) comprised of a developmental alloy (Optimized ZIRLOTM) at Waterford 3.
3.1 Material Evaluation
3.1.1 Fuel Mechanical Design
Tin is a solid solution strengthener and α-phase stabilizer present entirely in the base α-phase zirconium crystalline structure. Potential impacts of a reduced tin content on material properties include: (1) A reduced tensile strength; (2) an increased thermal creep rate; (3) an increased irradiation growth rate; (4) a reduced α →α+β phase transition temperature; and (5) an improved corrosion resistance. The stated reduction in tin content of Optimized ZIRLOTM will not affect the size, shape, or distribution of any second-phase or inter-metallic precipitates nor the overall microstructure of this developmental zirconium alloy. With a consistent microstructure, Optimized ZIRLOTM will exhibit many material characteristics similar to those of the licensed ZIRLOTM.
In response to a Request for Additional Information (RAI), Entergy provided details of the planned post-irradiation examinations of the LTAs. Measured parameters include rod profilometry, rod wear, assembly and rod growth, assembly bow, grid cell dimensions, and oxide thickness. As a result of these post-irradiation examinations, any negative aspects of the low tin alloy's performance, including the potential impacts of a reduced tin content identified above, will be identified and resolved. Furthermore, significant deviations from model predictions will be reconciled.
The fuel rod burnup and fuel duty experienced by the LTAs in Waterford 3 will remain well within the operating experience base and applicable licensed limits for ZIRLOTM.
Utilizing currently-approved fuel performance and fuel mechanical design models and methods, Entergy and Westinghouse Electric Corporation (Westinghouse) will perform cycle-specific reload evaluations to ensure that the LTAs satisfy design criteria.
Based upon LTA irradiation experience of similar low tin versions of ZIRLOTM, expected performance due to similar material properties, and an extensive LTA post-irradiation examination program aimed at qualifying model predictions, the NRC staff finds the LTA mechanical design acceptable for Waterford 3.
3.1.2 Core Physics and Safety Analysis
The Waterford 3 exemption request relates solely to the specific types of cladding material specified in the regulations. Due to similar material properties, any impact of Optimized ZIRLOTM on the safety analysis models and methods is expected to be minimal. Utilizing currently-approved core physics, core thermal-hydraulics, and non-loss-of-coolant accident (LOCA) safety analysis models and methods, Entergy and Westinghouse will perform cycle-specific reload evaluations to ensure that the LTAs satisfy design criteria.
Fuel management guidelines will require that LTAs be placed in non-limiting core locations. In response to an RAI, Entergy described how power-peaking margins would be used to ensure that LTAs will not be limiting.
Based upon the use of approved models and methods, expected material performance, and the placement of LTAs in non-limiting core locations, the NRC staff finds that the irradiation of up to four LTAs in Waterford 3 will not result in unsafe operation or violation of specified acceptable fuel design limits. Furthermore, in the event of a design-basis accident, these LTAs will not promote consequences beyond those currently analyzed. Based upon results of metal-water reaction tests and ring-compression tests, which ensure the applicability of ECCS models and acceptance criteria and the use of approved LOCA models to ensure that the LTAs satisfy 10 CFR 50.46 acceptance criteria, the NRC staff considers the LTAs acceptable for use at Waterford 3 as proposed by Entergy.
3.2 Regulatory Evaluation
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 if: (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) special circumstances are present.
3.2.1 10 CFR 50.46
The underlying purpose of 10 CFR 50.46 is to establish acceptance criteria for ECCS performance. The applicability of the ECCS acceptance criteria has been demonstrated by Westinghouse. Ring-compression tests performed by Westinghouse on Optimized ZIRLOTM (documented in Appendix B of Addendum 1 to WCAP-12610-P-A) demonstrate an acceptable retention of ductility up to 10 CFR 50.46 limits of 2200 °F and 17 percent Equivalent Cladding Reacted.
Utilizing currently approved LOCA models and methods, Westinghouse will perform cycle-specific reload evaluations to ensure that the LTAs satisfy 10 CFR 50.46 acceptance criteria. Therefore, granting the proposed exemption will not defeat the underlying purpose of 10 CFR 50.46.
3.2.2 10 CFR Part 50, Appendix K
Paragraph I.A.5 of Appendix K to 10 CFR part 50 states that the rates of energy, hydrogen concentration, and cladding oxidation from the metal-water reaction shall be calculated using the Baker-Just equation. Since the Baker-Just equation presumes the use of zircaloy clad fuel, strict application of the rule would not permit use of the equation for the LTA cladding for determining acceptable fuel performance. Metal-water reaction tests performed by Westinghouse on Optimized ZIRLOTM (documented in Appendix B of Addendum 1 to WCAP-12610-P-A) demonstrate conservative reaction rates relative to the Baker-Just equation. Therefore, granting the proposed exemption will not defeat the underlying purpose of Appendix K, Paragraph I.A.5.
3.2.3 Special Circumstances
In summary, the NRC staff reviewed the licensee's request of proposed exemption to allow up to four LTAs containing fuel rods fabricated with Optimized ZIRLOTM. Based on the NRC staff's evaluation, as set forth above, the NRC staff considers that granting the proposed exemption will not defeat the underlying purpose of 10 CFR 50.46 or Appendix K to 10 CFR Part 50. Accordingly, special circumstances, are present pursuant to 10 CFR 50.12(a)(2)(ii).
3.2.4 Other Standards in 10 CFR 50.12
The staff examined the rest of the licensee's rationale to support the exemption request, and concluded that the use of Optimized ZIRLOTM would satisfy 10 CFR 50.12(a) as follows:
(1) The requested exemption is authorized by law:
No law precludes the activities covered by this exemption request. The Commission, based on technical reasons set forth in rulemaking records, specified the specific cladding materials identified in 10 CFR 50.46 and 10 CFR part 50, Appendix K. Cladding materials are not specified by statute.
(2) The requested exemption does not present an undue risk to the public Start Printed Page 47467health and safety as stated by the licensee:
The LTA reload evaluation will ensure that these acceptance criteria [in the Commission's regulations] are met following the insertion of LTAs containing Optimized ZIRLOTM material. Fuel assemblies using Optimized ZIRLOTM cladding will be evaluated using NRC-approved analytical methods and plant specific models to address the changes in the cladding material properties. The safety analysis for Waterford 3 is supported by the applicable Technical Specifications. The Waterford 3 reload cores containing Optimized ZIRLOTM cladding are required to be operated in accordance with the operating limits specified in the Technical Specifications. The LTAs utilizing Optimized ZIRLOTM cladding will be placed in non-limiting core locations. Thus, the granting of this exemption request will not pose an undue risk to public health and safety.
The NRC staff has evaluated these considerations as set forth in Section 3.1 of this exemption. For the reasons set forth in that section, the NRC staff concludes that Optimized ZIRLOTM may be used as a cladding material for no more than four LTAs to be placed in non-limiting core locations during Waterford 3's next refueling outage, and that an exemption from the requirements of 10 CFR 50.46 and 10 CFR part 50, Appendix K does not pose an undue risk to the public health and safety.
(3) The requested exemption will not endanger the common defense and security:
The common defense and security are not affected and, therefore, not endangered by this exemption.
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 Entergy an exemption from the requirements of 10 CFR 50.46 and 10 CFR part 50, Appendix K, to allow the use of Optimized ZIRLOTM as a cladding material in four LTAs in the capacity described in their April 30, 2004, submittal, as supplemented by letter dated June 8, 2004, up to a lead rod average burnup of 60,000 MWD/MTU.
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 (69 FR 31848 dated June 7, 2004).
This exemption is effective upon issuance.Start Signature
Dated in Rockville, Maryland, this 28th day of July, 2004.
For the Nuclear Regulatory Commission.
James E. Lyons,
Deputy Director, Division of Licensing Project Management, Office of Nuclear Reactor Regulation.
[FR Doc. 04-17853 Filed 8-4-04; 8:45 am]
BILLING CODE 7590-01-P