NL-10-0824, Hatch, Unit 2, GNF-0000-0114-0175NP, Technical Basis Supporting GNF-Ziron Lead Test Assembly Introduction.
| ML101340740 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 03/31/2010 |
| From: | Global Nuclear Fuel - Americas |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NL-10-0824 GNF-0000-0114-0175NP | |
| Download: ML101340740 (9) | |
Text
{{#Wiki_filter:Edwin I. Hatch Nuclear Plant-Unit 2 Proposed Exemption to 10 CFR 50.46 and 10 CFR 50 Appendix K for HNP Unit 2 Enclosure 7 GNF-0000-0114-0175NP, "Technical Basis Supporting GNF-Ziron Lead Test Assembly Introduction into the Hatch Unit 2 Nuclear Plant," March 2010 (Nonproprietary) Nm Global Nuclear Fuel A Joint Venture of GEToshiba, & Hitachi Global Nuclear Fuel GNF-0000-0114-0175NP Class I March 2010 Non-Proprietary Information Technical Basis Supporting GNF-Ziron Lead Test Assembly Introduction into the Hatch Unit 2 Nuclear Plant Copyright 2010 Global Nuclear Fuel-Americas, LLC All Rights Reserved Non-Proprietary Information GNF-0000-0114-0175NP Class I Technical Basis Supporting GNF-Ziron Lead Test Assembly Introduction into the Hatch Nuclear Plant I. Purpose: Southern Nuclear Operating Company (SNC) and Global Nuclear Fuel -Americas (GNF-A)intend to establish an option for use of GNF-Ziron fuel cladding in the Edwin I Hatch Nuclear Plant (Units 1 and 2). This document describes the licensing basis for using GNF-Ziron in Unit 2 to broaden operating experience with GNF-Ziron cladding material. It is proposed that this broadening of operating experience be achieved through irradiation of four GNF2 Lead Test Assemblies (LTAs) with GNF-Ziron fuel rod cladding in Plant Hatch Unit 2 during Cycles 22, 23 and 24. The purpose of this document is to provide the technical bases to support SNC's request for exemption to cladding-specific requirements of 10 CFR 50.46, and 10 CFR Part 50 Appendix K. In addition, this document also discusses the licensing approach to meeting the requirement described in Reference 1 for lead test assemblies to be analyzed with approved methods.II. GNF-Ziron Characteristics and Properties GNF-Ziron is a zirconium-based alloy that is a slight modification to Zircaloy-2, which is widely used in the BWR industry as the material for fuel rod cladding and other fuel assembly components. The primary compositional difference is in the iron content of GNF-Ziron, which is selected to be above the range for Zircaloy-2 as specified in the ASTM B350 industry standard.GNF-Ziron has a [[ ]] compared with a 0.20-wt% upper limit for Zircaloy-2. A more detailed description of GNF-Ziron was given in support of SNC's previous exemption request 12], in which two GE14 lead test assemblies with select fuel rods clad with GNF-Ziron were placed into Plant Hatch Unit 2 starting Cycle 21. A more complete description of GNF-Ziron is provided in Reference 3.The material properties that are inputs to approved methods for evaluating the performance of fuel rods during various operating conditions (e.g. normal operation, LOCA) have been evaluated and documented in References 3 and 4 (which are attached to this document), In addition to providing a detailed description of GNF-Ziron, Reference 4 documents material attributes of GNF-Ziron and demonstrates that the material properties are [[]]. These attributes include response to processing conditions, and physical, thermal and mechanical properties, such as creep, irradiation growth and high temperature oxidation behaviors. GNF-Ziron differentiates itself from Zircaloy-2 with regards to absorption of corrosion-released hydrogen at high exposure/residence time and [[ ]], as described in Reference 4.Ill. Lead Test Assemblies at Plant Hatch Unit 2 GNF and SNC are proposing to irradiate four (4) LTAs in Plant Hatch Unit 2 during cycles 22, 23 and 24 to provide broader in-reactor experience with GNF-Ziron cladding in GNF2 fuel. All fuel rods in these LTAs will have GNF-Ziron cladding. This operating experience, along with the revised GNF2 compliance report to be issued once GNF-Ziron is licensed by the NRC, will form the basis for future reload applications of GNF2 fuel with GNF-Ziron cladding in domestic BWRs.Page 1 Non-Proprietary Information GNF-0000-0114-0175NP Class I SNC has concluded that use of GNF-Ziron cladding is not prevented by the Plant Hatch Technical Specifications; therefore, subsequent to NRC-approval of this submittal, loading the LTAs into the Hatch Unit 2 reactor will be evaluated as a change to the Plant as required by 10 CFR 50.59. GNF will provide SNC technical information to support this evaluation. Consistent with the approach described in Reference 3, the evaluations of the LTAs will be performed using PRIME per References 5 -8 and other approved methods.IV. Review of Methods As described in Reference I "As long as the analysis of the LTAs using approved methods meets the approved criteria, it would be concluded that no unreviewed safety question exists." GEH/GNF perform fuel rod thermal-mechanical design and licensing analyses using the PRIME model and its associated application methodology, which has recently been approved by the NRC [8].A key part of the statistical methodology is the inclusion of model uncertainty based upon the PRIME qualification results. This prediction uncertainty, couched in terms of a corresponding uncertainty in [[ ]] In addition to this model uncertainty, the PRIME application methodology explicitly addresses uncertainties in fabrication parameters and uncertainties in cladding material and plant-specific factors such as cladding oxidation. Fuel rods are designed such that, if they are operated within their specific thermal-mechanical operating limits of power versus exposure (LHGR limits), all licensing and design criteria are explicitly satisfied. The LHGR limits are specified to ensure compliance with the primary fuel rod thermal-mechanical licensing and design constraints. The primary thermal-mechanical licensing parameters that may be impacted by the introduction of a new cladding material such as GNF-Ziron are: Fuel Melting Fuel Rod Internal Pressure Cladding Plastic Strain Cladding Stress/Strain Cladding Fatigue Cladding Creep Collapse Material properties inputs to approved methods for evaluating the performance of fuel rods are documented in References 3 and 4 (attached to this document). Reference 3 documents material attributes that are equivalent between GNF-Ziron and Zircaloy. The primary difference between GNF-Ziron and Zircaloy is in the area of hydriding, as documented in Reference
- 4. In consideration of the properties of GNF-Ziron, an assessment of the primary thermal-mechanical licensing parameters that may be affected by the introduction of the GNF-Ziron cladding has been performed; the details of the assessment are provided in Reference
- 4. The conclusion from the assessment was that, [[]] implementation of GNF-Ziron will have no detrimental impact on thermal-mechanical licensing limits or margins.Page 2 Non-Proprietary Information GNF-0000-01 14-0175NP Class I Reference 4 also provides assessment of GNF-Ziron instead of Zircaloy-2 as the cladding material from the perspective of compliance with requirements for simulated LOCA and RIA conditions.
V. Technical Basis for Exemptions to 10 CFR 50.46 and Part 50 Appendix K Title 10 of the Code of Federal Regulations (10 CFR) Part 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," requires that the calculated emergency core cooling system (ECCS) performance for reactors with Zircaloy or ZIRLO fuel cladding meet certain criteria which have requirements related to: maximum cladding oxidation; peak cladding temperature; maximum hydrogen generation;' coolable geometry and long-term cooling. 10 CFR Part 50 Appendix K, "ECCS Evaluation Models," further requires that the Baker-Just (BJ) equation be used in the ECCS evaluation model to determine the rate of energy release, cladding oxidation, and hydrogen generation after a postulated loss-of-coolant accident (LOCA). The BJ equation presumes the use of Zircaloy or ZIRLO fuel cladding. There is no provision for cladding material other than Zircaloy or ZIRLO in 10 CFR 50.46 and Part 50 Appendix K. Exemptions to 10 CFR 50.46 and Part 50 Appendix K are therefore required for the use of GNF-Ziron as the cladding material.In 10 CFR 50.46 and within the BJ equation, no differentiation is made between types of Zircaloy, specifically between the commercially available Zircaloy-2 and Zircaloy-4. The underlying reason is that differences in composition between the two types of Zircaloy are not sufficient to result in significant differences in the high temperature oxidation characteristics. The composition of GNF-Ziron is not substantially different from that of Zircaloy-2. The behavior and properties of GNF-Ziron during and after a postulated LOCA [[]]High temperature oxidation tests have been conducted at 1000°C (1273 K) and 12000C (1473 K) to demonstrate the applicability of the BJ equation to GNF-Ziron and the results are shown in Figure 1. Figure 1 shows that the use of the BJ and Cathcart-Powel (CP) equations remains conservative in the postulated LOCA circumstances relative to the measured GNF-Ziron data. The maximum cladding oxidation and peak cladding temperature limits are collectively known as the embrittlement criteria. In order to address the potential embrittlement due to absorbed hydrogen associated with a postulated LOCA, post-quench ductility tests following oxidation at 10000C and 1200 0 C have been conducted at room temperature and 135 0 C (408K), respectively. The post-quench ductility results are shown in Figure 2 on the basis of permanent strain and as a function of Effective Cladding Reacted (ECR) calculated using the CP equation. The results show post-quench ductility of greater than a threshold of 1%permanent strain at up to 17% ECR. It should be noted that the ECR values in Figure 2 are expressed using the CP correlation, whereas the current embrittlement criterion is based on the BJ equation. If the BJ equation were used, the embrittlement ductilities for GNF-Ziron would be higher than indicated in Figure 2. In addition, quench tests under a restraining load have been conducted at -1100 and -1 200'C with GNF-Ziron cladding oxidized to [[ ]]ECR at -11 00°C and to [[ ]] ECR at -12000C. The predicted ECR values were calculated using the BJ equation. The test results showed that cladding oxidized to[[ ]] BJ-ECR or less did not fail and that only cladding oxidized to [[ ]] BJ-ECR failed. The test results thus indicate margin to embrittlement relative to the 17% BJ-ECR clad oxidation limit stated in 10 CFR 50.46.Page 3 Non-Proprietary Information 1 GNF-0000-0114-0175NP Class I The iron content of GNF-Ziron deviates only slightly from that of Zircaloy-2, while the alloy compositions are otherwise the same. Consequently, a significant change in the hydrogen generated from cladding-water reaction is not expected. Moreover, in the context of the proposed LTAs for Hatch Unit 2, any core-wide change in hydrogen generation due to a change from Zircaloy-2 to GNF-Ziron would be further diminished by the fact that only four LTAs will be involved. Additionally, since the composition change is only increased Fe content relative to Zircaloy-2, the change in essence replaces some zirconium atoms with iron atoms. The potential effect on hydrogen generation due to replacing one Zr atom with a Fe atom can be estimated as follows. Each Zr atom will react with two H 2 0 molecules to form stoichiometric ZrO 2 , thereby releasing 4 hydrogen atoms. Since Fe has a lower valence than Zr, each Fe atom can result in the release of 2, 3, or 2.67 atoms of hydrogen depending on whether stoichiometric FeO, Fe 2 0 3 or Fe 3 0 4 , respectively, is formed from the reaction with water. The expected result of replacing one Zr atom with one Fe atom is therefore a reduction in the number of released hydrogen atoms. Thus, because of the similarity in composition between Zircaloy-2 and GNF-Ziron, evaluation of hydrogen release based on GNF-Ziron cladding is conservatively bounded by the calculation based on Zircaloy-2 cladding. Furthermore, any difference in calculated hydrogen generation would be slightly less for the GNF-Ziron case.The coolable geometry criterion is generally addressed through high temperature perforation tests. A comparison of test data of GNF-Ziron and Zircaloy-2, provided in Figure 3, shows that the high temperature perforation characteristic, and hence coolable geometry evaluation, for GNF-Ziron [[]] because of the similar composition. The similarity in composition with Zircaloy-2 and the high temperature test results described above thus demonstrate with a high degree of confidence that the underlying requirements of 10 CFR 50.46 and Part 50 Appendix K are met when GNF-Ziron is used as the cladding material.Therefore, there is no anticipated decrease in coolability or increase in dose consequences as a result of a postulated LOCA for GNF-Ziron relative to evaluations performed assuming Zircaloy cladding.Page 4 Non-Proprietary Information Class I GNF-0000-0114-0175NP Er TI Figure 1 Weight gain data for GNF-Ziron at 1273K and 1473K compared with Baker-Just and Cathcart-Powel relationships Er Figure 2 Post-Quench Ductility (Permanent Strain) at Room Temperature for GNF-Ziron and Zircaloy-2 as a function of ECR at 1273K followed by quench from 1073K and at 408K as a function of ECR at 1473K followed by quench from 1073K.Page 5 Non-Proprietary Information Class I GNF-0000-01 14-0175NP[[Figure 3 Perforation hoop stress of GNF-Ziron cladding compared with Zircaloy-2 data VI. Summary 10 CFR 50.46 and Part 50 Appendix K explicitly state or implicitly assume the cladding material to be Zircaloy or ZIRLO. To allow the development and in-reactor testing of a fuel cladding material which is neither Zircaloy or ZIRLO, it is necessary to request exemptions to 10 CFR 50.46 and Part 50 Appendix K from the NRC for the Plant Hatch Unit 2 LTAs containing GNF-Ziron cladding. Based on the similarity in composition with Zircaloy-2 and the high temperature test results, the underlying requirements of 10 CFR 50.46 and Part 50 Appendix K are shown to be met with a high degree of confidence when GNF-Ziron is used as the cladding material.Based upon the [[ ]] GNF has concluded that evaluations using the currently approved methods (including the PRIME model and its application methodology) for fuel performance during various operating conditions, including accidents, are fully applicable to GNF2 fuel assemblies with GNF-Ziron fuel rod cladding. The GNF2 LTAs with GNF-Ziron fuel rod cladding to be inserted in Plant Hatch Unit 2 reactor during Cycles 22, 23 and 24 will be evaluated by applying existing approved methods.Page 6 Non-Proprietary Information GNF-0000-0114-0175NP Class I VIII. References
- 1. NRC Letter, "Lead Test Assembly Licensing," T. A. Ippolito (NRC) to R. E. Engel (GE), September 23, 1981.2. NRC Letter, "Edwin I. Hatch Nuclear Plant, Unit No 2- Exemptions from the Requirements of 10 CFR Part 50, Section 50.46, and Appendix K (TAC No. MD8356)," R. E. Martin to D. H. Jones, November 7, 2008, ML082950149.
- 3. GNF-0000-0101-6839P, "GNF-Ziron Basic Characteristics and Properties," March 2010.4. GNF-0000-01 13-8604P, "GNF-Ziron Performance Benefits and Licensing Requirements Assessment," March 2010 5. NEDC-33245P "The PRIME Model for Analysis of Fuel Rod Thermal -Mechanical Performance Part I -Technical Bases." 6. NEDC-33257P, "The PRIME Model for Analysis of Fuel Rod Thermal -Mechanical Performance Part 2 -Qualification." 7. NEDC-33258P, "The PRIME Model for Analysis of Fuel Rod Thermal -Mechanical Performance Part 3 -Application Methodology." 8. NRC Letter, "The PRIME Model for Analysis of Fuel Rod Thermal-Mechanical Performance," T.B. Blount (NRC) to A.A. Lingenfelter (GNF), ML100190258, January 22, 2010.Page 7}}