ML23241B040
| ML23241B040 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 09/11/2023 |
| From: | Jardaneh M NRC/NRR/DSS/STSB |
| To: | Technical Specifications Task Force |
| Shared Package | |
| ML23241B051 | List: |
| References | |
| EPID L-2022-PMP-0000 | |
| Download: ML23241B040 (7) | |
Text
FINAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER TSTF-589, REVISION 0, ELIMINATE AUTOMATIC DIESEL GENERATOR START DURING SHUTDOWN USING THE CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS (EPID L-2022-PMP-0000)
1.0 INTRODUCTION
By letter dated February 3, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22034A015), the Technical Specifications Task Force (TSTF) submitted Traveler TSTF-589, Revision 0, Eliminate Automatic Diesel Generator [DG] Start During Shutdown, to the U.S. Nuclear Regulatory Commission (NRC); hereafter referred to as TSTF-589. TSTF-589 proposed changes to the Standard Technical Specifications (STSs) for the pressurized-water reactor (PWR) plant designs listed below. Upon approval, these changes will be incorporated into future revisions of:
NRC NUREG-1430, Standard Technical Specifications, Babcock and Wilcox Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21272A363 and ML21272A370, respectively).
NRC NUREG-1431, Standard Technical Specifications, Westinghouse Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and ML21259A159, respectively).
NRC NUREG-1432, Standard Technical Specifications, Combustion Engineering Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21258A421 and ML21258A424, respectively).
Upon approval, this traveler will be made available to licensees for adoption through the consolidated line item improvement process.
The proposed changes would eliminate the Technical Specifications (TSs) requirements for the automatic DG start and loading capability to be operable during shutdown. In addition, the traveler modifies which DG surveillance requirements (SRs) are required during shutdown.
2.0 REGULTORY EVALUATION 2.1
System Description
Class 1E refers to safety-related electric equipment. The Class 1E alternating current (AC) electrical power system provides a reliable source of power to the engineered safety feature (ESF) systems. The design provides independence and redundancy to ensure a reliable source of power to the Class 1E system. The AC electrical power system includes offsite power sources and Class 1E onsite standby power sources (i.e., DGs) that supply electrical power to the plant load groups, with each load group powered by an independent Class 1E ESF bus.
Each ESF bus has connections to offsite power sources and one or more DGs.
DGs provide AC power during a loss of offsite power (LOOP). A DG starts automatically on a LOOP signal based on an ESF bus degraded voltage or undervoltage signal, or an ESF (safety injection) signal. After the DG starts, it automatically ties to its respective Class 1E ESF bus in case of LOOP signal, or coincident with, an ESF signal. In the event of a LOOP or LOOP coincident with an accident, the ESF electrical loads are automatically connected to the DG in time to provide for safe reactor shutdown and to mitigate the consequences of a design-basis accident such as a loss of coolant accident (LOCA).
2.2 Proposed Changes to Standard Technical Specifications 2.2.1 Proposed Changes to Instrumentation, STS 3.3 The traveler TSTF-589 proposes that the phrase: "When the associated DG is required to be OPERABLE by LCO [Limiting Condition for Operation] 3.8.2, 'AC Sources - Shutdown', be deleted from the Applicability statements of the following DG loss of power or DG loss of voltage specifications:
NUREG-1430, STS 3.3.8, Emergency Diesel Generator (EDG) Loss of Power Start (LOPS)
NUREG-1431, STS 3.3.5, Loss of Power (LOP) Diesel Generator (DG) Start Instrumentation NUREG-1432, STS 3.3.6 Diesel Generator (DG) - Loss of Voltage Start (LOVS)
(Analog)
NUREG-1432, STS 3.3.7, Diesel Generator (DG) - Loss of Voltage Start (LOVS)
(Digital)
The deleted phrase would change the LCO by no longer requiring the automatic start and loading signals to the DGs to be operable during shutdown. The Bases are also modified to remove references to the DG auto start and load signals being required in Modes 5 and 6.
2.2.2 Proposed Changes to Alternating Current Sources - Shutdown, STS 3.8.2 STS 3.8.1, "AC Sources - Operating," contains requirements on AC sources (offsite power and DGs) in Modes 1, 2, 3, and 4. Many of those SRs are also applicable during shutdown. Instead of listing the SRs again, STS 3.8.2 refers to the SRs in STS 3.8.1. The table in section 3.3 of TSTF-589, lists details on the SRs that test AC sources. SR 3.8.2.1 states that all of the STS 3.8.1 SRs are applicable during shutdown, except for a list of excepted SRs. TSTF-589 proposes that SR 3.8.2.1 be revised to state which of the TS 3.8.1 SRs are applicable instead of the STS 3.8.1 SRs that are not applicable. Additionally, because of the proposed changes to STS 3.3, the automatic start and loading signals to the DGs would no longer be required to be operable during shutdown, and the SRs that test the automatic start would no longer need to be met during shutdown. Therefore, TSTF-589 proposes that the following STS 3.8.1 SRs would no longer be required to be met1 or performed2: SR 3.8.1.7, SR 3.8.1.11, SR 3.8.1.13, SR 3.8.1.15, and SR 3.8.1.18.
Additionally, the NOTE in SR 3.8.2.1 stating which of the STS 3.8.1 SRs are not required to be performed would be revised to reflect the changes to the SRs that are not required to be met.
The capability to meet the acceptance criteria in these SRs must be present, but the licensee would not be required to perform the SRs.
2.3 Applicable Regulatory Requirements and Guidance The regulation under Title 10 of the Code of Federal Regulations (10 CFR) 50.36(a)(1) requires that:
Each applicant for a license authorizing operation of a utilization facility shall include in his application proposed technical specifications in accordance with the requirements of this section. A summary statement of the bases or reasons for such specifications, other than those covering administrative controls, shall also be included in the application, but shall not become part of the technical specifications.
The regulation under 10 CFR 50.36(b) requires that:
Each license authorizing operation of a utilization facility will include technical specifications. The technical specifications will be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto, submitted pursuant to [10 CFR] 50.34 [Contents of applications; technical information]. The Commission may include such additional technical specifications as the Commission finds appropriate.
The categories of items required to be in the TSs are listed in 10 CFR 50.36(c).
The regulation at 10 CFR 50.36(c)(2) requires that TSs include LCOs. Per 10 CFR 50.36(c)(2)(i), LCOs are the lowest functional capability or performance levels of equipment required for safe operation of the facility. The regulation also requires that when an LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TS until the condition can be met.
The regulation at 10 CFR 50.36(c)(3) requires that TSs include items in the category of SRs, which are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met.
1 A Surveillance is 'met' when the acceptance criteria are satisfied (actual performance Surveillance test is not required to be performed). Known failure of the requirements of a Surveillance, whether or not the Surveillance was 'performed,' constitutes a Surveillance not 'met.'
2 'Performed' refers only to the requirement to specifically determine (via Surveillance) the ability to meet the acceptance criteria."
The NRC staffs guidance for the review of TSs is in Chapter 16.0, Technical Specifications, of NUREG-0800, Revision 3, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light-Water Reactor] Edition (SRP), March 2010 (ML100351425). As described therein, as part of the regulatory standardization effort, the NRC staff has prepared STSs for each of the LWR nuclear designs.
The Final Commission Policy Statement on Technical Specification (TS) Improvements for Nuclear Power Reactors, dated July 22, 1993 (58 FR 39132), provides the following description of the scope and the purpose of the STSs Bases:
Each LCO, Action, and Surveillance Requirement should have supporting Bases.
The Bases should at a minimum address the following questions and cite references to appropriate licensing documentation (e.g., FSAR [final safety analysis report], Topical Report) to support the Bases.
- 1. What is the justification for the Technical Specification, i.e., which Policy Statement criterion requires it to be in the Technical Specifications?
- 2. What are the Bases for each LCO, i.e., why was it determined to be the lowest functional capability or performance level for the system or component in question necessary for safe operation of the facility and, what are the reasons for the Applicability of the LCO?
- 3. What are the Bases for each Action, i.e., why should this remedial action be taken if the associated LCO cannot be met; how does this Action relate to other Actions associated with the LCO; and what justifies continued operation of the system or component at the reduced state from the state specified in the LCO for the allowed time period?
- 4. What are the Bases for each Safety Limit?
- 5. What are the Bases for each Surveillance Requirement and Surveillance Frequency; i.e., what specific functional requirement is the surveillance designed to verify? Why is this surveillance necessary at the specified frequency to assure that the system or component function is maintained, that facility operation will be within the Safety Limits, and that the LCO will be met?
Note: In answering these questions the Bases for each number (e.g., Allowable Value, Response Time, Completion Time, Surveillance Frequency), state, condition, and definition (e.g., operability) should be clearly specified. As an example, a number might be based on engineering judgment, past experience, or PSA [probabilistic safety assessment] insights; but this should be clearly stated.
3.0 TECHNICAL EVALUATION
3.1 Instrumentation, STS 3.3 This change removes the operability requirement for instrumentation that would signal the automatic start and load of a DG during a LOOP. As stated in the STSs Bases for section 3.8.2:
The OPERABILITY of the minimum AC sources during MODES 5 and 6 and during movement of [recently] irradiated fuel assemblies ensures that:
- a. The unit can be maintained in the shutdown or refueling condition for extended periods,
- b. Sufficient instrumentation and control capability is available for monitoring and maintaining the unit status, and
- c. Adequate AC electrical power is provided to mitigate events postulated during shutdown, such as a fuel handling accident [involving handling recently irradiated fuel. Due to radioactive decay, AC electrical power is only required to mitigate fuel handling accidents involving recently irradiated fuel (i.e., fuel that has occupied part of a critical reactor core within the previous [x] days)]
Worst case bounding events 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.
As stated in the traveler, licensees do not typically assume a concurrent LOOP during analyzed shutdown accidents, such as a fuel handling accident. Because of the lower energy (i.e., lower temperatures and pressures) and decay heat in postulated events during shutdown, the NRC staff finds that the plant accident response does not require the DG to automatically (and rapidly) start and load to successfully mitigate the event should a LOOP occur. Based on this, the staff concludes that there would be sufficient time during shutdown for an operator to manually start and load the DG, if it was needed to maintain the reactor in a safe shutdown condition or to mitigate a postulated event. In addition, the proposed change would not affect the operability of instrumentation (normally powered by the uninterrupted power system (UPS) supported by the battery power source, until the DG can be manually started to provide backup power to UPS/instrument loads) used by operators to monitor and maintain the plant status or to maintain the unit in the shutdown or refueling condition for an extended period of time.
Therefore, this change is acceptable.
3.2 Alternating Current Sources - Shutdown, STS 3.8.2 SR 3.8.2.1 requires the performance of the SRs in STS 3.8.1, AC Sources - Operating, but lists some exceptions. Instead of listing the exceptions, SR 3.8.2.1 would be revised to list the specific SRs from STS 3.8.1 that are applicable. Additionally, the NOTE in SR 3.8.2.1 stating which of the STS 3.8.1 SRs are not required to be performed would be revised to reflect the changes to the SRs that are not required to be met. The capability to meet the acceptance criteria in these SRs must be present, but the licensee would not be required to perform the SRs.
Consistent with the proposed instrumentation changes to STS 3.3 evaluated in section 3.1 above, the traveler proposes to remove SRs that verify the DG automatic start and load capability during shutdown since the instrumentation required to provide those signals would no longer be required in Modes 5 and 6.
The STS 3.8.2 Bases states that LCO 3.8.2 ensures the capability of supporting systems necessary for avoiding immediate difficulty in the event of an accident during shutdown assuming either a LOOP or a loss of all onsite DG power. The operability of the required one offsite circuit and one DG ensures the availability of sufficient AC sources to operate the plant in a safe manner and to mitigate the consequences of postulated events (e.g., fuel handling accidents) during shutdown.
The proposed change eliminates the requirement to meet SR 3.8.1.7 and 3.8.1.15 because there is no longer a need for any minimum specified time to start and load a DG required during shutdown. The proposed change eliminates the requirement to meet SR 3.8.1.11 and SR 3.8.1.13 in Modes 5 and 6 because there is no longer a requirement that an ESF bus automatically shed load and that a DG auto starts on a loss of power signal or ESF actuation signal during shutdown. The proposed change eliminates the requirement to meet SR 3.8.1.18 because there is no longer a requirement that loads automatically sequence onto the ESF bus during shutdown. If a plant's current "AC Sources - Shutdown" TS requires meeting "AC Sources - Operating" SRs that verify these functions, the proposed change supports eliminating the requirement to meet those SRs during shutdown. Since the DG automatic start and load capabilities would no longer be required to be operable during shutdown conditions, verification of the operability of these functions would no longer be required. Therefore, these changes are acceptable.
The proposed Note to SR 3.8.2.1 states: "The following SRs are not required to be performed:
SR 3.8.1.3, SR 3.8.1.9, SR 3.8.1.10, SR 3.8.1.14, and SR 3.8.1.16." Currently, the Note lists the following SRs that are not required to be performed: SR 3.8.1.3, SR 3.8.1.9, SR 3.8.1.10, SR 3.8.1.11, SR 3.8.1.13, SR 3.8.1.14, SR 3.8.1.15, SR 3.8.1.16, and SR 3.8.1.18. These SRs are not required to be performed because only one DG is required to be operable, and performance of the SRs could render the required DG inoperable. Consistent with the discussion of "met" and "performed" in the STSs section 1.4, Frequency, the capability to meet the acceptance criteria in these SRs must be present, but it is not required to perform the SRs. These SRs are typically performed during a refueling outage by testing the DG that is not required to be operable such that the SRs have been performed prior to entering the applicability of TS 3.8.1 when the SRs must be both met and performed on both DGs. The proposed changes to this note are to remove reference to the four SRs that are no longer required to be met during shutdown (SR 3.8.1.11, SR 3.8.1.13, SR 3.8.1.15, and SR 3.8.1.18) and are conforming changes based on the SR changes evaluated above. Therefore, these changes are acceptable.
In summary, the NRC staff finds that since the DG automatic start is not required to mitigate the consequences of postulated events in shutdown conditions, testing of the DG automatic start and load capabilities is not required to demonstrate the operability of the DG during shutdown conditions. Therefore, the NRC staff finds that the proposed removal of SR 3.8.1.7, SR 3.8.1.11, SR 3.8.1.13, SR 3.8.1.15, and SR 3.8.18 from the list of SRs that are required for SR 3.8.2.1 is acceptable since testing of the DG automatic start and the automatic sequencing of loads to the ESF bus are no longer required to demonstrate the operability of the DG in shutdown conditions. The NRC staff finds that the proposed changes to SR 3.8.2.1 are acceptable because the revised SR 3.8.2.1 will continue to assure that the necessary quality of the onsite standby power systems and components is maintained, that facility operation will be within safety limits, and that the associated LCO 3.8.2 will be met in accordance with 10 CFR 50.36(c)(3).
3.3 Standard Technical Specification Bases The STSs Bases would be revised to state that automatic start of a DG is not assumed in Modes 5 and 6, and that operability of a DG in Modes 5 and 6 is based on the ability of the DG to be manually started, to accelerate to rated speed and voltage, to be manually connected to its respective ESF bus, and to accept required loads.
As discussed in section 2.3 of this SE, the Final Policy Statement on TSs describes the scope and purpose of the STSs Bases. It does so by listing five questions the STSs Bases must address. While the STSs Bases as a whole must address these questions, not every question will be relevant to every change to the STSs Bases.
The Policy Statement criterion that applies to the LCO is not affected and the first question is not relevant to this evaluation. The proposed change does not add any new actions or alter any remaining actions; therefore, the third question is not relevant to the changes. The fourth question is not relevant to this evaluation because the STS changes proposed in TSTF-589, Revision 0, as evaluated above, do not affect the safety limits.
The proposed changes to the STSs Bases explain the reasons for the applicability of the LCO and the basis for the SRs. The NRC staff finds that the proposed STSs Bases changes are appropriate to reflect the proposed revisions to the LCO Applicability and SR. Therefore, the NRC staff finds that the proposed revisions to the STSs Bases are consistent with the Commissions Final Policy Statement and 10 CFR 50.36 because the STS Bases changes adequately address the second and fifth questions.
4.0 CONCLUSION
The NRC staff finds that the proposed changes to STS 3.3 instrumentation requirements are acceptable because the LCO will continue to define the lowest functional capability or performance levels of equipment required for safe operation of the facility, and therefore, meet 10 CFR 50.36(c)(2)(i). In addition, the staff finds that the proposed changes to SR 3.8.2.1 are acceptable because the surveillances meet 10 CFR 50.36(c)(3) because they continue to provide requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met. Accordingly, the NRC staff finds TSTF-589 changes acceptable. Additionally, the NRC staff determined that the changes are technically clear and consistent with customary terminology and format in STSs.
Principal Reviewers: Michelle Honcharik, NRR/DSS/STSB Tarico Sweat, NRR/DSS/STSB Rob Elliott, NRR/DSS/STSB Vijay Goel, NRR/DE/EEEB Date: September 11, 2023