ML24023A296
| ML24023A296 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/09/2024 |
| From: | Dennis Galvin Plant Licensing Branch IV |
| To: | Peters K Vistra Operations Company |
| Galvin D | |
| References | |
| EPID L-2023-LLA-0058 | |
| Download: ML24023A296 (18) | |
Text
February 9, 2024 Mr. Ken J. Peters Senior Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Vistra Operations Company LLC Comanche Peak Nuclear Power Plant 6322 N FM 56 P.O. Box 1002 Glen Rose, TX 76043
SUBJECT:
COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 -
ISSUANCE OF AMENDMENT NOS. 186 AND 186 REGARDING GENERAL DESIGN CRITERION 5 OF APPENDIX A TO 10 CFR PART 50 AND REGULATORY GUIDE 1.81 (EPID L-2023-LLA-0058)
Dear Mr. Peters:
The U.S. Nuclear Regulatory Commission (the Commission) has issued the enclosed Amendment No. 186 to Facility Operating License No. NPF-87 and Amendment No. 186 to Facility Operating License No. NPF-89 for Comanche Peak Nuclear Power Plant, Unit Nos. 1 and 2 (Comanche Peak), respectively. The amendments authorize revision to the Updated Final Safety Analysis Report (UFSAR) in response to your application dated April 20, 2023, as supplemented by letters dated June 15, 2023, and October 12, 2023.
The amendments authorize revision to the Comanche Peak UFSAR to provide clarifications regarding conformance to Regulatory Guide 1.81, Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants, to meet the regulatory requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criterion 5, Sharing of structures, systems, and components. The UFSAR changes would provide additional description of the power feeds to some common 125 VDC (volt-direct-current) and 118 VAC (volt-alternating-current) safety-related electrical buses, which can be fed from both units, and also feeds some Unit 1 specific loads.
A copy of the related Safety Evaluation is also enclosed. Notice of Issuance will be included in the Commissions monthly Federal Register notice.
Sincerely,
/RA/
Dennis J. Galvin, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446
Enclosures:
- 1. Amendment No. 186 to NPF-87
- 2. Amendment No. 186 to NPF-89
- 3. Safety Evaluation cc: Listserv
COMANCHE PEAK POWER COMPANY LLC AND VISTRA OPERATIONS COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NO. 1 DOCKET NO. 50-445 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 186 License No. NPF-87
- 1.
The Nuclear Regulatory Commission (the Commission) has found that:
A.
The application for amendment by Vistra Operations Company LLC (Vistra OpCo) dated April 20, 2023, as supplemented by letters dated June 15, 2023 and October 12, 2023, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C.
There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D.
The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.
- 2.
Accordingly, by Amendment No. 186, the license is amended to authorize revision to the Updated Final Safety Analysis Report (UFSAR), as set forth in the application dated April 20, 2023, as supplemented by letters dated June 15, 2023, and October 12, 2023.
The licensee shall update the UFSAR to incorporate the changes as described in the licensees application dated April 20, 2023, as supplemented by letters dated June 15, 2023, and October 12, 2023, and in the NRC staffs safety evaluation enclosed with this amendment, and shall submit the revised description authorized by this amendment with the next update of the UFSAR.
- 3.
This license amendment is effective as of its date of issuance and shall be implemented within 90 days from the date of issuance. The UFSAR changes shall be implemented in the next periodic update to the UFSAR in accordance with 10 CFR 50.71(e).
FOR THE NUCLEAR REGULATORY COMMISSION Jennivine K. Rankin, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Date of Issuance: February 9, 2024 Jennivine K. Rankin Digitally signed by Jennivine K. Rankin Date: 2024.02.09 08:32:14 -05'00'
COMANCHE PEAK POWER COMPANY LLC AND VISTRA OPERATIONS COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NO. 2 DOCKET NO. 50-446 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 186 License No. NPF-89
- 1.
The Nuclear Regulatory Commission (the Commission) has found that:
A.
The application for amendment by Vistra Operations Company LLC (Vistra OpCo) dated April 20, 2023, as supplemented by letters dated June 15, 2023 and October 12, 2023, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C.
There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D.
The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.
- 2.
Accordingly, by Amendment No. 186, the license is amended to authorize revision to the Updated Final Safety Analysis Report (UFSAR), as set forth in the application dated April 20, 2023, as supplemented by letters dated June 15, 2023, and October 12, 2023.
The licensee shall update the UFSAR to incorporate the changes as described in the licensees application dated April 20, 2023, as supplemented by letters dated June 15, 2023, and October 12, 2023, and in the NRC staffs safety evaluation enclosed with this amendment, and shall submit the revised description authorized by this amendment with the next update of the UFSAR.
- 3.
This license amendment is effective as of its date of issuance and shall be implemented within 90 days from the date of issuance. The UFSAR changes shall be implemented in the next periodic update to the UFSAR in accordance with 10 CFR 50.71(e).
FOR THE NUCLEAR REGULATORY COMMISSION Jennivine K. Rankin, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Date of Issuance: February 9, 2024 Jennivine K. Rankin Digitally signed by Jennivine K. Rankin Date: 2024.02.09 08:31:49 -05'00'
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 186 TO FACILITY OPERATING LICENSE NO. NPF-87 AND AMENDMENT NO. 186 TO FACILITY OPERATING LICENSE NO. NPF-89 COMANCHE PEAK POWER COMPANY LLC AND VISTRA OPERATIONS COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-445 AND 50-446
1.0 INTRODUCTION
By letter dated April 20, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23110A156), as supplemented by letters dated June 15, 2023 (ML23166B144), and October 12, 2023 (ML23285A096), Vistra Operations Company LLC (the licensee) submitted a license amendment request (LAR) for Comanche Peak Nuclear Power Plant Unit Nos. 1 and 2 (Comanche Peak or CPNPP), to request authorization for certain changes to the Updated Final Safety Analysis Report (UFSAR).
Specifically, the UFSAR changes would provide clarifications regarding conformance to Regulatory Guide (RG) 1.81, Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants (ML003740343), to meet the regulatory requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criteria for Nuclear Power Plants, General Design Criterion (GDC) 5, Sharing of structures, systems, and components. The proposed UFSAR changes would provide an additional description of the power feeds to some common 125 VDC (volt-direct-current) and 118 VAC (volt-alternating-current) safety-related electrical buses, which can be fed from both units, and also feeds some Unit 1 specific loads. The licensee also submitted Technical Specifications (TS) Bases changes (mark-ups) necessary to reflect changes in the UFSAR.
The U.S. Nuclear Regulatory Commission (NRC or the Commission) staff notes that in the LAR, the licensee describes its commitment to meet the guidelines of RG 1.81 as compliance with the requirements of the RG. Since a RG is guidance and not a requirement, the NRC staff discusses meeting the guidelines as conformance (not as compliance) with a RG.
The supplemental letter dated October 12, 2023, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the NRC staffs original proposed no significant hazards consideration determination as published in the Federal Register (FR) on July 11, 2023 (88 FR 44168).
2.0 REGULATORY EVALUATION
2.1 Description of the Onsite Power Distribution System As described in chapter 8,0, Electric Power, of the Comanche Peak UFSAR (Package ML22277A832) and TS Bases B3.8.9, Distribution Systems - Operating (ML22038A164), the onsite Class 1E alternating current (AC or a.c.), direct current (DC), and AC vital bus electrical power distribution systems are divided into two trains which consist of redundant and independent AC, DC, and AC vital bus electrical power distribution subsystems.
The AC electrical power subsystem for each train consists of a primary engineered safety feature (ESF) 6.9 kilovolt (kV) bus, secondary load centers, and 480 V and 120 V buses. Each 6.9 kV ESF bus has two separate and independent offsite sources of power as well as a dedicated onsite emergency diesel generator (EDG) source. Each 6.9 kV ESF bus is normally connected to a preferred offsite source. After a loss of the preferred offsite power source to a 6.9 kV ESF bus, a slow transfer to the alternate offsite source is accomplished. If the alternate offsite sources are unavailable, the onsite EDG supplies power to the 6.9 kV ESF bus.
There are two independent 125 VDC electrical power distribution subsystems (one for each train). The 118 VAC vital buses are arranged in two load groups per train and are normally powered from the inverters. The alternate power supply for each vital bus is from a Class 1E transformer powered from the same train as the associated inverter.
The safety-related distribution buses are listed in the following TS Bases B3.8.9-1:
Table B3.8.9-1 AC and DC Electrical Power Distribution Systems TYPE VOLTAGE TRAIN A(1)(2)
TRAIN B(1)(2)
AC safety buses 6900 V 480 V ESF Bus 1EA1 (2EA1)
Load Centers 1EB1, 1EB3 (2EB1, 2EB3)
ESF Bus 1EA2 (2EA2)
Load Centers 1EB2, 1EB4 (2EB2, 2EB4)
DC buses 125 V Bus 1ED1 (2ED1)
Bus 1ED3 (2ED3)
Bus 1ED2 (2ED2)
Bus 1ED4 (2ED4)
AC vital buses 118 V Buses 1EC1, 1EC5 (2EC1, 2EC5)
Buses 1PC1, 1PC3 (2PC1, 2PC3)
Bus XEC1-1(3)(4)
Buses 1EC2, 1EC6 (2EC2, 2EC6)
Buses 1PC2, 1PC4 (2PC2, 2PC4)
Bus XEC2-1(3)(4)
(1) Each train of the AC and DC electrical power distribution systems is a subsystem.
(2) The 480 V load centers are fed from the following transformers:
1EB1 - T1EB1 1EB2 - T1EB2 1EB3 - T1EB3 1EB4 - T1EB4 2EB1 - T2EB1 2EB2 - T2EB2 2EB3 - T2EB3 2EB4 - T2EB4 (3) When this bus is powered by Unit 2 in MODES 1-6, the bus is immediately considered INOPERABLE, and the requirements of TS 3.8.9, Condition B or TS 3.8.10, Condition A are applicable as appropriate for Unit 1 ONLY.
(4) When this bus is powered by Unit 1, the bus is not a required distribution bus for TS 3.8.9 or TS 3.8.10 purposes The above table is based on the supplement provided by the licensee on October 12, 2023.
Based on Comanche Peak UFSAR, figure 8.3-13, 118 VAC common bus XEC1-1 (Train A) is normally fed from upstream panel 1EC5, which in-turn is normally fed by an inverter connected to 125 VDC bus 1ED3. The 125 VDC bus 1ED3 is in-turn fed by a battery and a battery charger connected to upstream 480 VAC motor control center (MCC) bus 1EB1-1. The 480 VAC MCC bus 1EB1-1 is then normally fed from upstream 480 VAC load center bus 1EB1.
Also, based on Comanche Peak UFSAR figure 8.3-13, 118 VAC common bus XEC2-1 (Train B) is normally fed from upstream panel 1EC6, which in-turn is normally fed by an inverter connected to 125 VDC bus 1ED4. The 125 VDC bus 1ED4 is connected to a battery and through a battery charger to upstream 480 VAC MCC bus 1EB2-1. The 480 VAC MCC bus 1EB2-1 is then normally fed from upstream 480 VAC load center bus 1EB2.
2.2 Proposed Changes The licensee is requesting authorization for an UFSAR change previously made by the licensee that the NRC found in the Comanche Peak Integrated Inspection Report, dated November 1, 2022 (ML22299A056), required prior NRC approval. The inspection report stated, in part:
In January 2000, the licensee discovered electrical power panels that shared safety-related alternating current and direct current electrical power between Units 1 and 2, contrary to what was described in the Comanche Peak FSAR
[Final Safety Analysis Report] and NUREG-0797, Safety Evaluation Report related to the Operation of Comanche Peak Steam Electric Station, Units 1 and 2, Docket Nos. 50-445 and 50-446, Supplement 22. The licensee took corrective action to modify the plant and revise the FSAR description of their original commitments to NRC RG 1.81, Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants. RG 1.81 was used by the
licensee to comply with General Design criterion 5, Sharing of structures, systems, and components.
In April 2002, the licensee issued 10 CFR 50.59 screening document 59SC-2000-000142-02-02 which changed the description of RG 1.81 commitments in the FSAR. The licensee was originally committed to positions C.1 and C.3 of RG 1.81, which describes that there was no sharing of emergency power sources between units. The 10 CFR 50.59 screening document changed the description of the licensees commitment to position C.2 of RG 1.81, which allowed sharing of emergency power sources given specific conditions. Specifically, position C.2 applied only to plants under construction permits issued before June 1, 1973, and the position was NRC reviewed on an individual case basis. The change was screened-out of the 10 CFR 10.59
[50.59] process and no license amendment was submitted.
The inspectors determined that the licensee inappropriately applied position C.2 of RG 1.81 because the Comanche Peak construction permit was issued after June 1, 1973, and Comanche Peak was originally evaluated against position C.3 of RG 1.81. The inspectors determined these were changes to commitments that were used to meet General Design Criteria 5. Additionally, the unit specific loads on the common unit panels could result in new failure modes for previously evaluated accidents.
The licensee was provided a Notice of Violation because the licensee failed to obtain a license amendment or perform a written evaluation demonstrating the basis for not obtaining a license amendment prior to making a change to the facility as described in the UFSAR. Specifically, the licensee revised the UFSAR to change the facility's commitments to RG 1.81, which demonstrated compliance with GDC 5, without obtaining a license amendment.
In the LAR, the licensee has proposed certain changes to the Comanche Peak UFSAR. In particular, the licensee has proposed conformance with RG 1.81, regulatory position C.2 instead of its original committed conformance with RG 1.81 regulatory positions C.1 and C.3. The LAR seeks approval of this commitment change. In addition, the licensee has added additional description of power feeds to common 125 VDC and 118 VAC panels. The licensee has also provided changes to the TS Bases B.3.8.9 regarding power feeds to 118 VAC common panels.
A detailed description of the UFSAR changes is provided in section 3.1 of this safety evaluation.
A description of the conforming change to the TS Bases is provided in section 3.3 of this safety evaluation.
2.3 Applicable Regulatory Requirements The NRC staff applied the following NRC regulations for review of the LAR:
Appendix A to 10 CFR Part 50, GDC 5, requires that structures, systems, and components important to safety, including the onsite electric power supplies and distribution systems, shall not be shared among nuclear power units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions, including, in the event of an accident in one unit, an orderly shutdown and cool down of the remaining units.
2.4 Applicable Regulatory Guidance The NRC staff also reviewed the LAR based on the following regulatory guidance document:
RG 1.81, Revision 1, dated January 31, 1975, describes a method acceptable to the NRC staff for complying with NRCs requirements with respect to the sharing of onsite emergency and shutdown electric systems for muti-unit nuclear power plants.
3.0 TECHNICAL EVALUATION
The LAR Attachment 1, FSAR Changes (markup) - For Information Only, provides the UFSAR changes for which the licensee is requesting authorization. In the LAR Attachment 2, Technical Specification Bases Changes (markup) - For Information Only, and the supplement dated October 12, 2023, the licensee provided conforming changes to the TS Bases.
3.1 Changes to the UFSAR In the LAR and supplement dated June 15, 2023, the licensee requested authorization to revise Comanche Peak UFSAR section 8.3.1.2.1, Item 8 (starting on UFSAR page 8.3-451 in the LAR and supplement markups) as follows:
- 8.
Compliance With NRC Regulatory Guide 1.81 [Revision 1]
The CPNPP design represents a deviation of Regulatory Guide 1.81, Regulatory Positions C.1 and C.3, as approved in Amendments xxx and xxx to the Unit 1 and Unit 2 facility licenses, respectively (Reference 49).
Regulatory Position C.1 states that DC systems in multi-unit nuclear power plants should not be shared. Regulatory Position C.3 states that each unit should have separate and independent onsite emergency and shutdown electric systems (i.e., vital power should not be shared between units). The CPNPP design includes some safety-related common loads, and some Unit 1 specific loads fed from common panels, which is a deviation from Regulatory Guide 1.81, Regulatory Positions C.1 and C.3.
The acceptability of this design is described below and is in compliance with GDC 5 in that the sharing of these loads does not significantly impair the ability to perform the necessary safety functions, assuming an accident in one unit and an orderly shutdown and cooldown of the remaining unit.
Compliance with Regulatory Position C.2:
Regulatory Position 2.a, The sharing of onsite a.c. electric systems should be limited to two units:
CPNNP sharing of onsite AC electric systems are limited to only Unit 1 and Unit 2.
1 In the LAR and supplement markups section 8.3.1.2.1, Item 8 begins on page 8.3-45 while in the Comanche Peak UFSAR (FSAR Amendment 111, dated February 1, 2022 (ML22277A825)),
section 8.3.1.2.1, Item 8 begins on page 8.3-44.
Regulatory Position 2.b, A single failure (a false or spurious accident signal at the system level in the non-accident unit should be considered as a single failure) should not preclude the capability to automatically supply minimum engineered safety feature (ESF) loads in any one unit and safely shut down the remaining unit, assuming a loss of the offsite power:
Due to redundancy for common systems being maintained consistent with that of unit-specific safety-related trains, a single-failure at the system level will not preclude the capability to automatically supply minimum ESF loads in any one unit and safely shutdown the other unit assuming a loss of off-site power.
Regulatory Position 2.c, Onsite power capacity should be provided to energize sufficient Seismic Category I equipment to attain a safe and orderly cold shutdown of all units, assuming the loss of offsite power and the most severe (in terms of power drain) design basis event and a single failure in the onsite electric system:
On-site power capacity to energize sufficient Seismic Category I equipment to attain a safe and orderly cold shutdown of both the units, assuming the loss of offsite power and most severe design basis event and a single failure in the on-site electrical system, is not compromised as a result of common buses because each unit system is designed to have sufficient capacity to feed common bus loads in addition to the unit specific loads.
Regulatory Position 2.d, The interaction between each unit's engineered safety feature electric circuits should be limited such that any allowable combination of maintenance and test operations in the units will not preclude the capability to automatically supply power to minimum ESF loads in any unit, assuming a loss of offsite power:
For AC electric systems, CPNPP has created the following administrative procedural requirement for XEC1-1 and XEC2-1, which power some Unit 1 safety-related loads, that the power source SHALL be aligned to Unit 1 during Unit 1 Modes 1 through 6. The panels power source alignment to Unit 2 will only be allowed when Unit 1 is in NO MODE. Since they only power Unit 1 loads this will not allow any interaction.
Two common DC electric systems, XED1-1 and XED2-1, feed both Unit 1 and common components. Alignment to either unit provides an acceptable power source for Unit 1 components fed from the panels. An evaluation of being aligned from a Unit 2 power source coincident with a Unit 1 SI
[safety injection] signal did not reveal any adverse impacts (i.e., no significant loss of safety function was identified). Evaluations confirmed that the power sources, from both units, feeding the common buses have sufficient capacity and capability to adequately feed all the common bus loads, as stated in the FSAR.
Regulatory Position 2.e, Coordination between the unit operators should not be necessary in order to meet Regulatory Positions 2.b and 2.c. Coordination required to meet Regulatory Position 2.d should be minimized:
As stated above, XEC1-1 and XEC2-1 cannot be aligned to Unit 2 while there is fuel in the Unit 1 reactor vessel; therefore, for AC electric systems there is no possible interaction from Unit 2 operators.
For DC electric systems the evaluations confirmed that the power sources from both units, have sufficient capacity and capability to adequately feed all XED1-1 and XED2-1 common loads and unit specific loads as stated in the FSAR. Because redundancy for common systems is maintained consistent with that of unit-specific safety-related trains, a single failure at the system level will not preclude the capability to automatically supply minimum ESF loads in any one unit and safely shutdown the other unit assuming a loss of off-site power. Based on this there is no need for coordination between unit operators for Regulatory Positions 2.b or 2.c, and minimal coordination would be needed for Regulatory Position 2.d.
Regulatory Position 2.f, Complete information regarding the status of the shared systems should be provided for each unit operator:
The status of the which unit power supply is aligned to shared loads is provided in the control room which is available to the unit operator of each unit.
Regulatory Position 2.g, The design should conform to the recommendations contained in Regulatory Guides 1.6 [Independence Between Redundant Standby (Onsite) Power Sources and Between Their Distribution Systems]
(Safety Guide 6), 1.9 [Application and Testing of Safety-Related Diesel Generators in Nuclear Power Plants] (Safety Guide 9), and 1.47 [Bypassed and Inoperable Status Indication for Nuclear Power Plant Safety Systems]:
CPNPP design is in accordance with RG 1.6, RG 1.9, and RG 1.47. This is laid out in the sites UFSAR, this is laid out in other sections of Section 8.3.
3.2 Evaluation of UFSAR Changes The NRC staff evaluated the requested authorization to revise the Comanche Peak UFSAR, as described above, regarding conformance with RG 1.81, regulatory position C.2, (in lieu of original commitments to RG 1.81, regulatory positions C.1 and C.3). RG 1.81, regulatory position C.2 states:
Multi-unit nuclear power plants now under construction or for which construction permit application was made before June 1, 1973, will be reviewed on an individual-case basis. For these plants, the design of shared onsite emergency and shutdown a.c. electric systems should satisfy the following.
The NRC staff notes that while the construction permit application for Comanche Peak was made after June 1, 1973, and thus Comanche Peak did not meet construction permit date in
RG 1.81 for regulatory position C.2, the LAR states that Comanche Peak was under construction in December 1974, which is prior to the issuance of RG 1.81, Revision 1, in January 1975. Thus, Comanche Peak met the guideline for a multi-unit under construction applicable to RG 1.81, Revision 1. Therefore, the staff reviewed the change to the description of conformance to RG 1.81 on an individual basis, consistent with RG 1.81, regulatory positions C.2.a to C.2.g in the following paragraphs.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.a, because Comanche Peak is a two-unit plant, and the sharing of onsite AC electric systems is limited to two units.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.b, because the redundancy for common systems will be maintained to meet the single failure criteria between the two units to automatically supply minimum ESF loads in any one unit and safely shutdown the other unit assuming a loss of offsite power. The LAR does not propose to make any changes to the common loads.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.c, because the onsite power capacity to energize sufficient Seismic Category I equipment will remain available to attain a safe and orderly cold shutdown of both units, assuming the loss of offsite power, the most severe design basis event, and a single failure in the onsite electric system.
The LAR does not propose to make any changes to the Seismic Category I equipment to meet the safe shutdown criteria.
RG 1.81, regulatory position C.2.d, specifies that the interaction between each unit's ESF electric circuits should be limited such that any allowable combination of maintenance and test operations in the units will not preclude the capability to automatically supply power to minimum ESF loads in any unit, assuming a loss of offsite power. The NRC staff determined that the licensee conformance to regulatory position C.2.d required further review since common panels 118 VAC XEC1-1 and XEC2-1, and 125 VDC common XED1-1 and XED2-1 can be fed from either Unit 1 or Unit 2 upstream power sources.
As shown in Comanche Peak UFSAR figure 8.3-13, 118 VAC common bus XEC1-1 (Train A) is normally fed from upstream panel Unit 1 1EC5 bus, which in-turn is normally fed by an inverter connected to 125 VDC bus Unit 1 1ED3 bus. However, the XEC1-1 bus can be fed also by the Unit 2 2EC5 bus. Similarly, 118 VAC common bus XEC2-1 (Train B) is normally fed from upstream panel Unit 1 1EC6 bus, which in-turn is normally fed by an inverter connected to the 125 VDC bus Unit 1 1ED4 bus. However, the XEC2-1 bus can be fed also by the Unit 2 2EC6 bus. These possible alternate feed of 118 VAC common buses XEC1-1 and XEC2-1 from any unit raised concerns for safe shutdown during various design-basis conditions.
In its response to Request 1 by letter dated June 15, 2023, the licensee stated that to address GDC 5 requirements, it evaluated the impact on performance of Unit 1 safety functions including safe shutdown and orderly shutdown and cooldown of Unit 1, if Unit 2 is feeding the Unit 1 components connected/fed by XEC1-1 and XEC2-1. According to the licensees evaluation, for some components, feeding the components from Unit 2 power source can have adverse impact on safe shutdown, and orderly shutdown and cool down of Unit 1. Therefore, the licensee determined that the XEC1-1 and XEC2-1 power source shall be aligned to Unit 1 while Unit 1 is in MODES 1 through 6. The panels power source alignment to Unit 2 will be allowed only when Unit 1 is in NO MODE (defueled). The licensee also added these requirements in TS Bases.
As shown in Comanche Peak UFSAR figure 8.3-13, 125 VDC common bus XED1-1 (Train A) is normally fed from upstream panel Unit 1 1ED1 bus, which in-turn is normally fed by a battery and a battery charger connected to a 480 VAC MCC bus 1EB1-1. However, XED1-1 bus can be fed also by a Unit 2 2ED1 bus. Similarly, 125 VDC common bus XED2-1 (train B) is normally fed from upstream panel Unit 1 1ED2 bus, which in-turn is normally fed by a battery and a battery charger connected to a 480 VAC MCC bus 1EB2-1. However, the XED2-1 bus can be fed also by the Unit 2 2ED2 bus. These possible alternate feed of 125 VDC common buses XED1-1 and XED2-1 from any unit raised concerns for safe shutdown during various design basis conditions.
In its response to Request 2 by letter dated June 15, 2023, the licensee stated that to address GDC 5 requirements, it evaluated the impact on performance of Unit 1 safety functions including safe shutdown and orderly shutdown and cooldown of Unit 1, if Unit 2 is feeding the Unit 1 components connected/fed by XED1-1 and XED2-1. According to the licensee evaluations, for some components, feeding the components from Unit 2 power source can have insignificant impact on safe shutdown, and orderly shutdown and cool down of Unit 1. However, the licensee determined that the XED1-1 and XED2-1 power source shall be normally aligned to Unit 1.
The NRC staff reviewed the evaluations performed by the licensee and finds that the licensee has adequately assessed the impact on performance of Unit 1 safety functions for safe shutdown of Unit 1, if Unit 2 is feeding the Unit 1 components connected/fed by 118 VAC buses XEC1-1 and XEC2-1, and by 125 VDC XED1-1 and XED2-1. The licensee will add the requirement in the UFSAR that XEC1-1 and XEC2-1 power source shall be aligned to Unit 1 while Unit 1 is in MODES 1 through 6, which provides an adequate level of change control since a change to the requirement would be subject to 10 CFR 50.59. The NRC staff also finds that additional controls for the XED1-1 and XED2-1 power sources are not needed since they can perform their credited functions aligned to either unit. Therefore, the staff finds that the licensee meets the guidelines of regulatory position C.2.d in RG 1.81.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.e, because the coordination between the unit operators will not be necessary in order to meet regulatory positions 2.b and 2.c, and the coordination required to meet regulatory position 2.d will be minimal based on the above evaluation.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.f, because the status of the unit power supply aligned to shared panels/loads is provided in the common control room available to the unit operator of each unit.
The NRC staff finds that the licensee meets the guidelines of regulatory position C.2.g, because the Comanche Peak design conforms to the recommendations contained in RGs 1.6 (Safety Guide 6), 1.9 (Safety Guide 9), and 1.47, as mentioned in UFSAR appendix 1A(B) and further discussed in UFSAR sections 8.3.1.2.1 (RGs 1.6 and 1.9) and 7.1.2.6 (RG 1.47).
The NRC staff also reviewed the other related changes to the Comanche Peak UFSAR identified in attachment 1 of the LAR and determined that they are conforming changes to be consistent with the changes to UFSAR section 8.3.1.2.1, Item 8. The NRC did not review other incidental unrelated changes to the Comanche Peak UFSAR as these are subject to licensee control under 10 CFR 50.59 and provided to the NRC in accordance with 10 CFR 50.71(e). The staff finds the revised proposed UFSAR section 8.3.1.2.1, Item 8 acceptable, as the licensee would be in conformance with RG 1.81, regulatory position C2, to meet the requirements of GDC 5. Therefore, the staff finds that it is acceptable to authorize the proposed change to Comanche Peak UFSAR section 8.3.1.2.1, Item 8, as described in the LAR, as supplemented.
3.3 Changes to the TS Bases In the LAR, the licensee proposed the addition of the following paragraph to TS Bases 3.8.9, Required Action B.1 corresponding to Condition B (One AC vital bus subsystem inoperable):
As AC Vital Bus 1EC5 or 2EC5 power AC common panel XEC1-1 and AC Vital Bus 1EC6 or 2EC6 power AC common panel XEC2-1, and evaluations have called into question the ability for Unit 2 to fully power all Unit 1 loads, XEC1-1 and XEC2-1 cannot be powered by Unit 2 when Unit 1 is in any mode applicable to TS 3.8.9 (i.e., MODES 1-4). When Unit 2 is powering XEC1-1 and XEC2-1 in MODES 1, 2, 3, or 4, the requirements of TS 3.8.9, Condition B are applicable for the associated vital bus (Ref. 3 [FSAR, Chapter 8.3]).
The licensee proposed appropriate changes to TS Bases table 3.8.9-1, in its supplement dated October 12, 2023.
In the LAR, the licensee proposed the addition of the following paragraph to TS Bases 3.8.10 (Distributing Systems - Shutdown) Required Actions A.1, A.2.1, A.2.2, A.2.3, A.2.4, and A.2.5, corresponding to Condition A (One or more required AC, DC, or AC vital bus electrical power distribution subsystems inoperable).
As AC Vital Bus 1EC5 or 2EC5 power common panel XEC1-1 and AC Vital Bus 1EC6 or 2EC6 power common panel XEC2-1, and evaluations have called into question the ability for Unit 2 to fully power all Unit 1 loads, XEC1-1 and XEC2-1 cannot be powered by Unit 2 when Unit 1 is in any mode applicable to TS 3.8.10 (i.e., MODES 5-6). When Unit 2 is powering XEC1-1 or XEC2-1 in MODES 5 or 6, the requirements of TS 3.8.10, Condition A, are applicable for the associated vital bus (Ref. 3 [FSAR Chapter 8.3]).
The NRC staff finds that the proposed changes to the TS Bases B3.8.9 and B3.8.9.10 are consistent with the proposed changes to Comanche Peak UFSAR section 8.3. These changes will be implemented in accordance with Comanche Peak TS 5.5.14, Technical Specifications (TS) Bases Control Program.
3.4 Technical Evaluation Conclusion
Based on the technical evaluation provided in section 3.0 above, the NRC staff finds there is reasonable assurance that the licensee would continue to meet the regulatory requirements discussed in section 2.3 of this safety evaluation. Therefore, the proposed changes to Comanche Peak UFSAR and TS Bases are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendments on January 25, 2024. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements with respect to installation or use of facility components located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration published in the Federal Register on July 11, 2023 (88 FR 44168), and there has been no public comment on such finding. Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
6.0 CONCLUSION
Based on the considerations discussed above, the NRC staff concludes that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: Vijay Goel Khadijah West Date: February 9, 2024
- via e-mail OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA*
NRR/DEX/EEEB/BC*
NAME DGalvin PBlechman WMorton DATE 1/25/2024 1/25/2024 12/6/2023 OFFICE NRR/DSS/STSB/BC(A)
NAME MShivani RSeigman JRankin DATE 1/24/2024 2/6/2024 2/9/2024 OFFICE NRR/DORL/LPL4/PM NAME DGalvin DATE 2/9/2024