ML23124A222
ML23124A222 | |
Person / Time | |
---|---|
Site: | Technical Specifications Task Force |
Issue date: | 06/30/2023 |
From: | Robert Elliott, Michelle Honcharik NRC/NRR/DEX/EEEB, NRC/NRR/DSS |
To: | Technical Specifications Task Force |
References | |
EPID L-2022-PMP-0000 | |
Download: ML23124A222 (7) | |
Text
1 2
3 4
DRAFT SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 5
TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER 6
TSTF-589, REVISION 0, ELIMINATE AUTOMATIC DIESEL GENERATOR START DURING 7
SHUTDOWN 8
USING THE CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS 9
(EPID L-2022-PMP-0000) 10 11
1.0 INTRODUCTION
12 13 By letter dated February 3, 2022 (Agencywide Documents Access and Management System 14 (ADAMS) Accession No. ML22034A015), the Technical Specifications Task Force (TSTF) 15 submitted Traveler TSTF-589, Revision 0, Eliminate Automatic Diesel Generator [DG] Start 16 During Shutdown, to the U.S. Nuclear Regulatory Commission (NRC); hereafter referred to as 17 TSTF-589. TSTF-589 proposed changes to the Standard Technical Specifications (STSs) for 18 pressurized-water reactor (PWR) plant designs. Upon approval, these changes will be 19 incorporated into future revisions of:
20 21 NRC NUREG-1430, Standard Technical Specifications, Babcock and Wilcox Plants, 22 Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 23 (ML21272A363 and ML21272A370, respectively).
24 NRC NUREG-1431, Standard Technical Specifications, Westinghouse Plants, Volume 1, 25 Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and 26 ML21259A159, respectively).
27 NRC NUREG-1432, Standard Technical Specifications, Combustion Engineering Plants, 28 Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 29 (ML21258A421 and ML21258A424, respectively).
30 31 Upon approval, this traveler will be made available to licensees for adoption through the 32 consolidated line item improvement process.
33 34 The proposed changes would eliminate the Technical Specifications (TSs) requirements for the 35 automatic DG start and loading capability to be operable during shutdown. In addition, the 36 traveler modifies which DG surveillance requirements (SRs) are required during shutdown.
37 38 2.0 REGULTORY EVALUATION 1
2 2.1
System Description
3 4
Class 1E refers to safety-related electric equipment. The Class 1E alternating current (AC) 5 electrical power system provides a reliable source of power to the engineered safety feature 6
(ESF) systems. The design provides independence and redundancy to ensure a reliable source 7
of power to the Class 1 E system. The AC electrical power system includes offsite power 8
sources and Class 1E onsite standby power sources (i.e., DGs) that supply electrical power to 9
the plant load groups, with each load group powered by an independent Class 1E ESF bus.
10 Each ESF bus has connections to offsite power sources and one or more DGs.
11 12 DGs provide AC power during a loss of offsite power (LOOP). A DG starts automatically on a 13 LOOP signal based on an ESF bus degraded voltage or undervoltage signal, or an ESF (safety 14 injection) signal. After the DG starts, it automatically ties to its respective Class 1E ESF bus in 15 case of LOOP signal, or coincident with, an ESF signal. In the event of a LOOP or LOOP 16 coincident with an accident, the ESF electrical loads are automatically connected to the DG in 17 time to provide for safe reactor shutdown and to mitigate the consequences of a design-basis 18 accident such as a loss of coolant accident (LOCA).
19 20 2.2 Proposed Changes to Standard Technical Specifications 21 22 2.2.1 Proposed Changes to Instrumentation, STS 3.3 23 24 The traveler TSTF-589 proposes that the phrase: "When the associated DG is required to be 25 OPERABLE by LCO [Limiting Condition for Operation] 3.8.2, 'AC Sources - Shutdown', be 26 deleted from the Applicability statements of the following DG loss of power or DG loss of voltage 27 specifications:
28 29 NUREG-1430, STS 3.3.8, Emergency Diesel Generator (EDG) Loss of Power Start 30 (LOPS) 31 NUREG-1431, STS 3.3.5, Loss of Power (LOP) Diesel Generator (DG) Start 32 Instrumentation 33 NUREG-1432, STS 3.3.6 Diesel Generator (DG) - Loss of Voltage Start (LOVS) 34 (Analog) 35 NUREG-1432, STS 3.3.7, Diesel Generator (DG) - Loss of Voltage Start (LOVS) 36 (Digital) 37 38 The deleted phrase would change the LCO by no longer requiring the automatic start and 39 loading capabilities for the DGs to be operable during shutdown. The Bases are also modified to 40 remove references to the DG auto start and load capabilities being required in Modes 5 and 6.
41 42 2.2.2 Proposed Changes to Alternating Current Sources - Shutdown, STS 3.8.2 43 44 STS 3.8.1, "AC Sources - Operating," contains requirements on AC sources (offsite power and 45 DGs) in Modes 1, 2, 3, and 4. Many of those SRs are also applicable during shutdown. Instead 46 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 47 TSTF-589, lists details on the SRs that test AC sources. SR 3.8.2.1 states that all of the 48 STS 3.8.1 SRs are applicable during shutdown, except for a list of excepted SRs. TSTF-589 49 proposes that SR 3.8.2.1 be revised to state which of the TS 3.8.1 SRs are applicable instead of 50 the STS 3.8.1 SRs that are not applicable. Additionally, because the proposed changes to 1
STS 3.3, the automatic start and loading capabilities of the DGs would no longer be required to 2
be operable during shutdown, the SRs which test the automatic start would no longer need to 3
be met during shutdown. Therefore, TSTF-589 proposes that the following STS 3.8.1 SRs 4
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 5
3.8.1.15, and SR 3.8.1.18.
6 7
Additionally, the NOTE in SR 3.8.2.1 stating which of the STS 3.8.1 SRs are not required to be 8
performed would be revised to reflect the changes to the SRs that are not required to be met.
9 The capability to meet the acceptance criteria in these SRs must be present, but the licensee 10 would not be required to perform the SRs.
11 12 2.3 Applicable Regulatory Requirements and Guidance 13 14 The regulation under Title 10 of the Code of Federal Regulations (10 CFR) 50.36(a)(1) requires 15 that:
16 17 Each applicant for a license authorizing operation of a utilization facility shall 18 include in his application proposed technical specifications in accordance with 19 the requirements of this section. A summary statement of the bases or reasons 20 for such specifications, other than those covering administrative controls, shall 21 also be included in the application, but shall not become part of the technical 22 specifications.
23 24 The regulation under 10 CFR 50.36(b) requires that:
25 26 Each license authorizing operation of a utilization facility will include 27 technical specifications. The technical specifications will be derived from the 28 analyses and evaluation included in the safety analysis report, and amendments 29 thereto, submitted pursuant to [10 CFR] 50.34 [Contents of applications; 30 technical information]. The Commission may include such additional technical 31 specifications as the Commission finds appropriate.
32 33 The categories of items required to be in the TSs are listed in 10 CFR 50.36(c).
34 35 The regulation at 10 CFR 50.36(c)(2) requires that TSs include LCOs. Per 36 10 CFR 50.36(c)(2)(i), LCOs are the lowest functional capability or performance levels of 37 equipment required for safe operation of the facility. The regulation also requires that when an 38 LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any 39 remedial action permitted by the TS until the condition can be met.
40 41 The regulation at 10 CFR 50.36(c)(3) requires that TSs include items in the category of SRs, 42 which are requirements relating to test, calibration, or inspection to assure that the necessary 43 quality of systems and components is maintained, that facility operation will be within safety 44 limits, and that the LCOs will be met.
45 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."
1 The NRC staffs guidance for the review of TSs is in Chapter 16.0, Technical Specifications, 2
of NUREG-0800, Revision 3, Standard Review Plan for the Review of Safety Analysis 3
Reports for Nuclear Power Plants: LWR [Light-Water Reactor] Edition (SRP), March 2010 4
(ML100351425). As described therein, as part of the regulatory standardization effort, the 5
NRC staff has prepared STSs for each of the LWR nuclear designs.
6 7
The Final Commission Policy Statement on Technical Specification (TS) Improvements for 8
Nuclear Power Reactors, dated July 22, 1993 (58 FR 39132), provides the following 9
description of the scope and the purpose of the STSs Bases:
10 11 Each LCO, Action, and Surveillance Requirement should have supporting Bases.
12 The Bases should at a minimum address the following questions and cite 13 references to appropriate licensing documentation (e.g., FSAR [final safety 14 analysis report], Topical Report) to support the Bases.
15 16
- 1. What is the justification for the Technical Specification, i.e., which Policy 17 Statement criterion requires it to be in the Technical Specifications?
18 19
- 2. What are the Bases for each LCO, i.e., why was it determined to be the lowest 20 functional capability or performance level for the system or component in 21 question necessary for safe operation of the facility and, what are the reasons 22 for the Applicability of the LCO?
23 24
- 3. What are the Bases for each Action, i.e., why should this remedial action be 25 taken if the associated LCO cannot be met; how does this Action relate to 26 other Actions associated with the LCO; and what justifies continued operation 27 of the system or component at the reduced state from the state specified in 28 the LCO for the allowed time period?
29 30
- 4. What are the Bases for each Safety Limit?
31 32
- 5. What are the Bases for each Surveillance Requirement and Surveillance 33 Frequency; i.e., what specific functional requirement is the surveillance 34 designed to verify? Why is this surveillance necessary at the specified 35 frequency to assure that the system or component function is maintained, 36 that facility operation will be within the Safety Limits, and that the LCO will be 37 met?
38 39 Note: In answering these questions the Bases for each number (e.g., Allowable 40 Value, Response Time, Completion Time, Surveillance Frequency), state, 41 condition, and definition (e.g., operability) should be clearly specified. As an 42 example, a number might be based on engineering judgment, past 43 experience, or PSA [probabilistic safety assessment] insights; but this should 44 be clearly stated.
45 46 47
3.0 TECHNICAL EVALUATION
1 2
3.1 Instrumentation, STS 3.3 3
4 This change removes the operability requirement for instrumentation that would automatically 5
start and load a DG during a LOOP. As stated in the STSs Bases for section 3.8.2:
6 7
The OPERABILITY of the minimum AC sources during MODES 5 and 6 and 8
during movement of [recently] irradiated fuel assemblies ensures that:
9 10
- a. The unit can be maintained in the shutdown or refueling condition for 11 extended periods, 12 13
- b. Sufficient instrumentation and control capability is available for monitoring 14 and maintaining the unit status, and 15 16
- c. Adequate AC electrical power is provided to mitigate events postulated during 17 shutdown, such as a fuel handling accident [involving handling recently 18 irradiated fuel. Due to radioactive decay, AC electrical power is only required 19 to mitigate fuel handling accidents involving recently irradiated fuel (i.e., fuel 20 that has occupied part of a critical reactor core within the previous [x] days)]
21 22 Worst case bounding events are deemed not credible in MODES 5 and 6 23 because the energy contained within the reactor pressure boundary, reactor 24 coolant temperature and pressure, and the corresponding stresses result in the 25 probabilities of occurrence being significantly reduced or eliminated, and in 26 minimal consequences.
27 28 As stated in the traveler, licensees do not typically assume a concurrent LOOP during analyzed 29 shutdown accidents, such as a fuel handling accident. Because of the lower energy (i.e., lower 30 temperatures and pressures) and decay heat in postulated events during shutdown, the NRC 31 staff finds that the plant accident response does not require the DG to automatically (and 32 rapidly) start and load to successfully mitigate the event should a LOOP occur. Based on this, 33 the staff concludes that there would be sufficient time during shutdown for an operator to 34 manually start and load the DG, if it was needed to maintain the reactor in a safe shutdown 35 condition or to mitigate a postulated event. In addition, the proposed change would not affect 36 the operability of instrumentation (normally powered by the uninterrupted power system (UPS) 37 supported by the battery power source, until the DG can be manually started to provide backup 38 power to UPS/instrument loads) used by operators to monitor and maintain the plant status or to 39 maintain the unit in the shutdown or refueling condition for an extended period of time.
40 Therefore, this change is acceptable.
41 42 3.2 Alternating Current Sources - Shutdown, STS 3.8.2 43 44 SR 3.8.2.1 requires the performance of the SRs in STS 3.8.1, AC Sources - Operating, but 45 lists some exceptions. Instead of listing the exceptions, SR 3.8.2.1 would be revised to list the 46 specific SRs from STS 3.8.1 that are applicable. Additionally, the NOTE in SR 3.8.2.1 stating 47 which of the STS 3.8.1 SRs are not required to be performed would be revised to reflect the 48 changes to the SRs that are not required to be met. The capability to meet the acceptance 49 criteria in these SRs must be present, but the licensee would not be required to perform the 50 SRs.
51 1
Consistent with the proposed instrumentation changes to STS 3.3 evaluated in section 3.1 2
above, the traveler proposes to remove SRs that verify the DG automatic start and load 3
capability during shutdown since the instrumentation required to provide that capability would no 4
longer be required in Modes 5 and 6.
5 6
The STS 3.8.2 Bases states that the LCO 3.8.2 ensures the capability of supporting systems 7
necessary for avoiding immediate difficulty in the event of an accident during shutdown 8
assuming either a LOOP or a loss of all onsite DG power. The operability of the required one 9
offsite circuit and one DG ensures the availability of sufficient AC sources to operate the plant in 10 a safe manner and to mitigate the consequences of postulated events (e.g., fuel handling 11 accidents) during shutdown).
12 13 The proposed change eliminates the requirement to meet SR 3.8.1.7 and 3.8.1.15 because 14 there is no longer a need for any minimum specified time to start and load a DG required during 15 shutdown. The proposed change eliminates the requirement to meet SR 3.8.1.11 and 16 SR 3.8.1.13 in Modes 5 and 6 because there is no longer a requirement that an ESF bus 17 automatically shed load and that a DG auto starts on a loss of power signal or ESF actuation 18 signal during shutdown. The proposed change eliminates the requirement to meet SR 3.8.1.18 19 because there is no longer a requirement that loads automatically sequence onto the ESF bus 20 during shutdown. If a plant's current "AC Sources - Shutdown" TS requires meeting "AC 21 Sources - Operating" SRs that verify these functions, the proposed change supports eliminating 22 the requirement to meet those SRs during shutdown. Since the DG automatic start and load 23 capabilities would no longer be required to be operable during shutdown conditions, verification 24 of the operability of these functions would no longer be required. Therefore, these changes are 25 acceptable.
26 27 The proposed Note to SR 3.8.2.1 states: "The following SRs are not required to be performed:
28 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 29 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 30 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 31 not required to be performed because only one DG is required to be operable, and performance 32 of the SRs could render the required DG inoperable. Consistent with the discussion of "met" and 33 "performed" in the STSs section 1.4, Frequency, the capability to meet the acceptance criteria 34 in these SRs must be present, but it is not required to perform the SRs. These SRs are typically 35 performed during a refueling outage by testing the DG that is not required to be operable such 36 that the SRs have been performed prior to entering the applicability of TS 3.8.1 when both SRs 37 must be met and performed on both DGs. The proposed changes to this note are to remove 38 reference to the four SRs that are no longer required to be met during shutdown (SR 3.8.1.11, 39 SR 3.8.1.13, SR 3.8.1.15, and SR 3.8.1.18) and are conforming changes based on the SR 40 changes evaluated above. Therefore, these changes are acceptable.
41 42 In summary, the NRC staff finds that since the DG automatic start is not required to mitigate the 43 consequences of postulated events in shutdown conditions, testing of the DG automatic start 44 and load capabilities are not required to demonstrate the operability of the DG during shutdown 45 conditions. Therefore, the NRC staff finds that the proposed removal of SR 3.8.1.7, SR 3.8.1.11, 46 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 47 acceptable since testing of the DG automatic start and the automatic sequencing of loads to the 48 ESF bus are no longer required to demonstrate the operability of the DG in shutdown 49 conditions. The NRC staff finds that the proposed changes to SR 3.8.2.1 are acceptable 50 because the revised SR 3.8.2.1 will continue to assure that the necessary quality of the onsite 51 standby power systems and components is maintained, that facility operation will be within 1
safety limits, and that the associated LCO 3.8.2 will be met in accordance with 2
3 4
3.3 Standard Technical Specification Bases 5
6 The STSs Bases would be revised to state that automatic start of a DG is not assumed in 7
Modes 5 and 6, and that operability of a DG in Modes 5 and 6 is based on the ability of the DG 8
to be manually started, to accelerate to rated speed and voltage, to be manually connected to 9
its respective ESF bus, and to accept required loads.
10 11 As discussed in section 2.3 of this SE, the Final Policy Statement on TSs describes the scope 12 and purpose of the STSs Bases. It does so by listing five questions the STSs Bases must 13 address. While the STSs Bases as a whole must address these questions, not every question 14 will be relevant to every change to the STSs Bases.
15 16 The Policy Statement criterion that applies to the LCO is not affected and the first question is 17 not relevant to this evaluation. The proposed change does not add any new actions or alter any 18 remaining actions; therefore, the third question is not relevant to the changes. The fourth 19 question is not relevant to this evaluation because the STS changes proposed in TSTF-589, 20 Revision 0, as evaluated above, do not affect the safety limits.
21 22 The proposed changes to the STSs Bases explain the reasons for the applicability of the LCO 23 and the basis for the SRs. The NRC staff finds that the proposed STSs Bases changes are 24 appropriate to reflect the proposed revisions to the LCO Applicability and SR. Therefore, the 25 NRC staff finds that the proposed revisions to the STSs Bases are consistent with the 26 Commissions Final Policy Statement and 10 CFR 50.36 because the STS Bases changes 27 adequately address the second and fifth questions.
28 29
4.0 CONCLUSION
30 31 The NRC staff finds that the proposed changes to STS 3 3 instrumentation requirements are 32 acceptable because the LCO will continue to define the lowest functional capability or 33 performance levels of equipment required for safe operation of the facility, and therefore, meet 34 10 CFR 50.36(c)(2)(i). In addition, the staff finds that the proposed changes to SR 3.8.2.1 are 35 acceptable because the surveillances meet 10 CFR 50.36(c)(3) because they continue to 36 provide requirements relating to test, calibration, or inspection to assure that the necessary 37 quality of systems and components is maintained, that facility operation will be within safety 38 limits, and that the LCOs will be met. Accordingly, the NRC staff finds TSTF-589 changes 39 acceptable. Additionally, the NRC staff determined that the changes are technically clear and 40 consistent with customary terminology and format in STSs.
41 42 Principal Reviewers: Michelle Honcharik, NRR/DSS/STSB 43 Tarico Sweat, NRR/DSS/STSB 44 Rob Elliott, NRR/DSS/STSB 45 Vijay Goel, NRR/DE/EEEB 46 47 Date: June 30, 2023 48