ML23289A217
| ML23289A217 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 10/16/2023 |
| From: | Ameren Missouri, Union Electric Co |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML23289A214 | List: |
| References | |
| ULNRC-06825, LDCN 22-0029 | |
| Download: ML23289A217 (1) | |
Text
Attachment 2 to ULNRC-06825 Page 1 of 5 Updated Regulatory Evaluation and Environmental Evaluation for License Amendment Request to ULNRC-06825 Page 2 of 5
4.0 REGULATORY EVALUATION
4.1 Applicable Regulatory Requirements/Criteria The regulatory requirements and/or guidance documents associated with this LAR include the following:
The CRACS, ESW system, CCW system, and RHR system are protected from the effects of natural phenomena, such as earthquakes, tornadoes, hurricanes, floods, and external missiles (GDC-2) (Reference 3).
The CRACS, ESW system, CCW system, and RHR system are designed to remain functional after a safe-shutdown earthquake and to perform their intended functions following a postulated hazard, such as a fire, internal missiles, or pipe break (GDC-3 and 4) (Reference 3).
The CRACS provides the control room with a conditioned atmosphere during all modes of plant operation, including post-accident operation (GDC-19) (Reference 3).
The CRACS, ESW system, CCW system, and RHR system are designed and fabricated to codes consistent with the quality group classification assigned by Regulatory Guide 1.26 (Reference 4) and the seismic category assigned by Regulatory Guide 1.29 (Reference 5). The power supply and control functions are in accordance with Regulatory Guide 1.32 (Reference 6).
The functional requirements of the RHR system are derived from Appendix K (Reference 7) limits for fuel cladding temperature, etc., following any of the DBAs, as delineated in 10 CFR 50.46. The subsystem functional parameters are integrated so that the Appendix K requirements are met over the range of anticipated accidents and single failure assumptions.
The RHR system is provided to transfer fission product decay heat and other residual heat from the core at a rate sufficient to prevent fuel or pressure boundary design limits from being exceeded (GDC-34) (Reference 3).
The capability to isolate components or piping is provided so that the safety functions of the RHR system, CCW system, and ESW system will not be compromised. This includes isolation of components to deal with leakage or malfunctions and to isolate non-safety-related portions of the system (GDC-35 and 44) (Reference 3).
The ESW system and CCW system are designed to remove heat from components important to mitigating the consequences of a LOCA or MSLB and to transfer the heat to the UHS (GDC-44)
(Reference 3).
There are no changes being proposed in this LAR such that conformance or commitments to the regulatory requirements and/or guidance documents above be changed or would come into question. The GDCs listed here remain met as described within the Callaway Plant FSAR SP Section 3.1 and under the associated system sections. The evaluations documented herein confirm that Callaway Plant will continue to comply with all applicable regulatory requirements.
The GDCs provide the design requirements and capabilities for structures, systems, and components; this change does not alter the design of the related systems. The required design for decay heat removal and control room habitability provides for the availability of both trains of the applicable systems (concurrent with a LOOP) during operating Modes and when the plant is taken or driven to cold shutdown from an event or transient. The proposed changes only apply when the plant is in a cold shutdown condition and/or being taken to refueling conditions. As noted, for example, in the Bases of the Technical Specifications for the electrical sources/systems, TS requirements are reduced in these conditions, so that when the plant is in these conditions, the full complement of equipment, including systems and support systems having redundant trains, is not required (provided shutdown risk is managed, as effected in part by measures for ensuring defense in depth). The configurations allowed during Modes 5 and 6 are not to ULNRC-06825 Page 3 of 5 exceptions to the GDC; they merely reflect reduced TS requirements when a system's complete as-designed capability may not be required.
In conclusion, based on considerations discussed herein, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
4.2 Precedent This LAR is similar in nature, with respect to the justification and support system requirements applicable in Modes 5 and 6, to the following license amendment previously issued to Callaway Plant:
- Callaway Plant, Unit 1, License Amendment 184 issued May 9, 2007 (ML071020342)
While this precedent is specific to the electrical power system requirements for the CREVS, CRACS, and emergency exhaust systems, the discussions on reduced requirements during Modes 5 and 6, and during the movement of irradiated fuel, including the corresponding arguments made in regard to single failure assumptions, LOOP requirements, and support/supported system relationships, are similar to those being made within this request.
4.3 No Significant Hazards Consideration Determination Ameren Missouri has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
- 1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No In general, when the unit is shut down, the Technical Specification (TS) requirements ensure that the unit has the capability to mitigate the consequences of postulated accidents, including a fuel handling accident.
However, assuming a single failure and concurrent loss of all offsite or all onsite power is not required (as described in Callaway Plant Final Safety Analysis Report, Standard Plant, section 3.1.2). The rationale for this is based on the fact that many design basis accidents (DBAs) that are analyzed in Modes 1, 2, 3, and 4 have no specific analyses in Modes 5 and 6. Worst case bounding events such as loss-of-coolant accidents and limiting pipe breaks are deemed not credible in Modes 5 and 6 because the energy contained within the reactor pressure boundary, reactor coolant temperature and pressure, and the corresponding stresses result in the probabilities of occurrence being significantly reduced or eliminated, and in minimal consequences. These deviations from DBA analysis assumptions and design requirements during shutdown conditions are allowed by the Limiting Conditions of Operation (LCOs) for required systems, including those required for mitigation of a fuel handling accident which may be postulated to occur during such conditions (i.e., Modes 5 and 6 or with the reactor defueled/offloaded).
The plant's design is such that, during normal plant operating conditions, the non-safety related Service Water (SW) system supplies cooling water (via safety-related Essential Service Water (ESW) piping) to plant loads, including the Component Cooling Water (CCW) system. During accident/emergency conditions, the safety-related ESW system serves as the emergency back-up for providing cooling water.
to ULNRC-06825 Page 4 of 5 The proposed changes to TS 3.4.8 and TS 3.9.6 would make it clear that the SW system is allowed to be a credited support system for one of the two required trains of the Residual Heat Removal (RHR) system in Modes 5 and 6, respectively, except when the plant is in a reduced-inventory, hot-core condition. The proposed change to 3.7.11 would make it clear that the SW system is allowed to be a credited support system for one of the two required trains of the Control Room Air Conditioning System (CRACS) during Modes 5 and 6 and during movement of irradiated fuel assemblies. The SW-supported train in either case would be the one not required to be supported by an emergency diesel generator per TS 3.8.2, "Electrical Sources - Shutdown."
The proposed amendment will not impact the ability of the RHR system to remove decay heat in Modes 5 or 6, or impact its ability to ensure mixing, prevent stratification, and effect gradual reactivity changes as needed during reactor coolant system boron concentration reductions. A loss of decay heat removal is not an "accident previously evaluated" in the FSAR; however, the design basis for the RHR system is clearly intended to preclude such an event. This intent will still be met, as the Technical Specifications will still require two RHR trains to be Operable during applicable conditions such that one train of the RHR system would remain available assuming either a LOOP or a single failure, consistent with the plant's licensing basis. On that basis, the RHR function would be met via the RHR train supported by the ESW system and an DG, or by the RHR train supported by the non-essential SW system and a normal offsite power source (except as prohibited when the plant is in a reduced-inventory, hot-core condition).
The one FSAR described DBA that may be postulated to occur during Mode 5 or Mode 6 is a fuel handling accident (FHA). The proposed changes do not affect the systems/functions required to mitigate the dose consequences of an FHA. (Control room dose is mitigated by the Control Room Emergency Ventilation System and not by CRACS.) Therefore, the proposed changes do not involve any significant increase in the consequences of the FHA as previously described in the FSAR.
The proposed changes are consistent with the assumptions for system availability made within the accident and transient analysis for shutdown Modes (5 and 6) and do not involve making any physical changes to the plant. As such, the changes do not introduce any new failure mechanisms or transient precursors, nor do they modify the likelihood of any existing precursors to an accident or transient as analyzed in the Callaway Plant FSAR.
Based on the above, it is concluded that the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.
- 2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No This proposed license amendment does not involve any physical changes to the plant or any changes to operation, function, or the performance requirements of the CRACS or RHR system (except as described above). As such, it does not introduce any new failure mechanisms or transient precursors different than those previously evaluated. The continued, very low potential for a loss of decay heat removal "event" is as described and explained above.
Therefore, it is concluded that this change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
- 3. Does the proposed change involve a significant reduction in a margin of safety?
to ULNRC-06825 Page 5 of 5 Response: No The margin of safety is established through equipment design, operating parameters, and the setpoints at which automatic actions are initiated. This amendment makes no physical changes to safety-related systems, operating parameters, or setpoints for initiation of protective actions.
The allowance for one train of the CRACS and RHR systems to be supported by the SW system in lieu of the ESW system during shutdown conditions per the proposed TS changes) is not expected to result in any significant change the availability of these systems for providing their required cooling function. The system alignment wherein the SW system supplies cooling water to the CRACS and the CCW system heat exchangers (the intermediary cooling water loop to the RHR heat exchangers) is a normal operating configuration for these systems. The SW system provides a more than an adequate cooling water flow rate, with system temperature limitations comparable to the ESW system, such that a significant change in residual heat removal rate and control room cooling would not be realized by this change.
Therefore, it is concluded that the proposed change does not involve a significant reduction in a margin of safety.
In consideration of all of the above, Ameren Missouri concludes that the proposed changes present no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and on that basis, a finding of "no significant hazards consideration" is justified.
4.4 Conclusions Based on the considerations discussed above, 1) there is a reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, 2) such activities will be conducted in compliance with the Commission's regulations, and 3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
5.0 ENVIRONMENTAL EVALUATION The proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, but it does not involve (i) a significant hazards consideration, (ii) a significant change in the types or a significant increase in the amounts of any effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.