ML24260A079
| ML24260A079 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 09/23/2024 |
| From: | Southern Nuclear Operating Co |
| To: | Turner Z Division of Operating Reactor Licensing |
| Turner, Zachary | |
| Shared Package | |
| ML24260A080 | List: |
| References | |
| EPID L-2024-LRM-0108 | |
| Download: ML24260A079 (15) | |
Text
Proposed Farley Nuclear Plant Units 1 & 2 License Amendment Request Proposing a New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods That Exceed the Linear Heat Generation Rate Limit Detailed in Regulatory Guide 1.183, Table 3, Footnote 11 Presubmittal Meeting: September 23, 2024
Agenda Description History Technical Evaluation Regulatory Evaluation Discussion
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods DESCRIPTION
- The proposed amendment would revise the facilities as described in the Updated Final Safety Analysis Report (UFSAR) to provide gap release fractions for fuel rods with greater than 54 GWD/MTU that exceed the 6.3 kW/ft linear heat generation rate (LHGR) limit stated in Regulatory Guide (RG) 1.183, Table 3, Footnote 11.
- This is a change to the alternative source term (AST) methodology approved for FNP.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods HISTORY In 2017 the NRC approved a full scope application of the AST to FNP Units 1 and 2 (ML17271A265). This full scope AST application revised the fuel handling accident (FHA) analysis. Fission product gap release fractions were developed in accordance with RG 1.183, Table 3, including Footnote 11.
- Footnote 11 in Section 3.2 of RG 1.183, Revision 0, notes that the non-LOCA fuel rod gap release fractions listed in Table 3 have been found acceptable for light-water reactor fuel with peak burnup of 62 GWD/MTU, provided that the maximum LHGR does not exceed 6.3 kW/ft at burnups greater than 54 GWD/MTU.
Then in 2019 the NRC approved a change to the Technical Specifications (TSs) to adopt TSTF-51 and TSTF-471 (ML19071A138). The FHA was re-evaluated to support those changes. The methodology approved for the AST was used.
The current licensing basis for the FHA conforms to RG 1.183, including Table 3, Footnote 11 fission product gap release fractions.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION
- Source Term - generated using the proposed gap release fractions and instantaneously released as a result of the accident
- Gap Release Fractions - generated as described below
- SNC requests an exception to RG 1.183, Revision 0, Table 3, Footnote 11
- 60% of the rods with greater than 54 GWD/MTU will be allowed to exceed the 6.3 kW/ft limit with a new LHGR limit of 7.4 kW/ft.
- No limit on the number of assemblies for which this exception applies
- Instead, the analysis will employ the maximum gap release fractions presented in Table 2.9 of PNNL-18212 5
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION (cont)
Gap Release Fractions
- PNNL-18212, Table 2.9 maximum gap release fractions for Kr-85, I-132, other noble gases, and alkali metals are greater than the RG 1.183 Table 3 gap release fractions.
- Applicability of the gap release fractions presented in Table 2.9 are the power and burnup bounds provided in Figure A.1 of PNNL-18212. Operation must be equal to or below the bounding power history in Figure A.1.
- The following will be documented on a cycle basis
- Adherence to the power history in PNNL-18212, Figure A.1
- No more than 60% of fuel rods exceed the RG 1.183, Table 3, Footnote 11 limits
- LHGR and burnup of the 60% are within PNNL-18212, Table 2.9 applicability limits
- Fuel rods that may be damaged because they may experience DNB following a locked rotor accident are not those that exceed the LHGR and burnup applicability limits 6
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION (cont)
- Fuel Handling Accident
- Described in UFSAR Section 15.4.5 - assumptions and inputs follow RG 1.183, Rev. 0 as approved in the AST
- No changes were made to the methods, inputs or assumptions in the analysis of record.
- Except as related to the gap release fractions
- Although requesting that PNNL-18212 maximum gap release fractions be applied to 60%
of the fuel rods, for the dose analysis, the PNNL-18212 maximum gap release fractions were conservatively applied to 100% of the rods in the affected fuel assembly.
- This maximizes the release from the fuel assembly.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION (cont)
- Control Rod Ejection Accident The rod ejection accident dose analysis does not need to consider the gap release fractions requested for the FHA. The rod ejection accident gap release fractions are independent of the Table 3 gap release fractions, and thus are not subject to the Footnote 11 limitations on LHGR and burnup which only apply to the Table 3 gap release fractions.
- Locked Rotor Accident
- The locked rotor accident dose analysis does not need to consider the gap release fractions requested for the FHA. The rods that may be damaged because they may experience departure from nucleate boiling (DNB) following a locked rotor accident are not those that exceed the LHGR and burnup applicability limits of RG 1.183, Revision 0, Table 3, Footnote 11. This will be checked on a reload-specific basis.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION (cont)
- Fuel Handling Accident - Results 9
Acceptance Criteria (Rem)
Containment FHA Location/Dose Point 6.3 3.2 3.2 EAB 6.3 1.2 1.2 LPZ 5
2.5 3.2 CR Regardless of whether the FHA accident occurs inside the containment or in the SFP room, the dose results at the EAB and LPZ are the same because the accident occurring in either location does not alter the activity released over the 2-hour period and the EAB and LPZ /Q values are not sensitive to the specific reactor building or auxiliary building release points.
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods TECHNICAL EVALUATION (cont)
- Fuel Handling Accident - Comparison with current results 10 Revised TEDE (Rem) - SFP FHA Current TEDE (Rem) - SFP FHA Revised TEDE (Rem) -
Containment FHA Current TEDE (Rem) -
Containment FHA Location/Do se Point 3.2 2.9 3.2 2.9 EAB 1.2 1.1 1.2 1.1 LPZ 2.5 2.4 3.2 3.0 CR These small increases are due to the revised source term related to the increased gap release fractions.
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods REGULATORY EVALUATION
- Provides an AST approach that is acceptable to the NRC Staff.
- Fundamental to the definition of an AST according to RG 1.183 are gap release fractions, and Table 3 of the RG provides gap release fractions for various volatile fission product isotopes and isotope groups, to be applied to non-LOCA accidents.
- Increased gap release fractions are proposed. The FHA dose analysis was revised to include these changes. The revised dose consequences continue to satisfy the requirements set forth in 10 CFR 50.67 and the acceptance criteria set forth in RG 1.183, Section 4.4.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods REGULATORY EVALUATION (cont)
- Provides requirements for updating a facility's final safety analysis report (FSAR)
- The affected radiological analyses descriptions in the FSAR will be updated to reflect the proposed changes and are included with this amendment.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods PRECEDENT
- Vogtle
- The NRC approved the Vogtle Units 1 and 2 AST FHA with up to 40% of the damaged fuel rods exceeding the RG 1.183, Revision 0, Footnote 11 applicability limits but meeting the PNNL-18212, Revision 1 applicability limits. These FHA gap release fractions were not applied to either locked rotor or rod ejection accidents.
- Wolf Creek
- The Wolf Creek AST approval described the use of the gap release fractions for the FHA dose analysis. These gap release fractions assumed 90% of the damaged fuel met the RG 1.183, Revision 0, Table 3, Footnote 11 applicability limits and the remaining 10% met the PNNL-18212, Revision 1 applicability limits. The FHA composite gap release fractions were not applied to either locked rotor or rod ejection accidents.
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New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods Remaining Actions and Schedule
- NRC Pre-Submittal Meeting 9/23/2024
- Submit LAR to NRC 9/30/2024
- Requested Approval by NRC 1 year from completion of acceptance review 14
New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods Discussion / Feedback 15