ML23321A125

Draft Traveler SE of TSTF-592 Revise Automatic Depressurization System (ADS) Instrumentation Requirements

ML23321A125
Person / Time
Site:	Technical Specifications Task Force
Issue date:	12/18/2023
From:	NRC/NRR/DSS/STSB
To:
References
EPID L-2022-PMP-0011
Download: ML23321A125 (14)

Text

1 DRAFT SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 2 TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER 3 TSTF-592, REVISION 2 4 REVISE AUTOMATIC DEPRESSURIZATION SYSTEM (ADS) 5 INSTRUMENTATION REQUIREMENTS 6 USING THE CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS 7 (EPID: L-2022-PMP-0011) 8 9

1.0 INTRODUCTION

10 11 By letter dated September 13, 2023, as supplemented by letter dated October 10, 2023, 12 (Agencywide Documents Access and Management System (ADAMS) Accession 13 Nos. ML23256A352 and ML23283A002, respectively), the Technical Specifications Task Force 14 (TSTF) submitted Traveler TSTF-592, Revision 2, Revise Automatic Depressurization System 15 (ADS) Instrumentation Requirements (TSTF-592), to the U.S. Nuclear Regulatory Commission 16 (NRC). TSTF-592 proposed changes to the Standard Technical Specifications (STS) for 17 boiling-water reactor (BWR) designs under the consolidated line item improvement process 18 (CLIIP). Upon approval, these changes would be incorporated into future revisions of 19 NUREG-1433 and NUREG-1434, and this traveler would be available to licensees for adoption 20 through the CLIIP.1 21 22 The proposed change would revise Emergency Core Cooling System (ECCS) Instrumentation, 23 technical specifications (TS) Actions related to ADS instrumentation monitoring channels.

24 25

2.0 REGULATORY EVALUATION

26 27 2.1 System Description 28 29 The purpose of the ECCS instrumentation is to initiate appropriate responses from systems to 30 ensure that the fuel is adequately cooled in the event of a design basis accident or transient.

31 The ECCS uses two independent methods (flooding and spraying) to cool the core during a 32 loss-of-coolant accident (LOCA).

33 34 According to the BWR/4 STS Bases, the BWR/4 systems that ECCS instrumentation actuates 35 are core spray (CS), low-pressure coolant injection (LPCI), high-pressure coolant injection 36 (HPCI), ADS, and the diesel generators. According to the BWR/6 STS Bases, the BWR/6 1 U.S. Nuclear Regulatory Commission, Standard Technical Specifications, General Electric BWR/4 Plants, NUREG-1433, Volume 1, Specifications, and Volume 2, Bases, Revision 5.0, September 2021 (ML21272A357 and ML21272A358, respectively).

U.S. Nuclear Regulatory Commission, Standard Technical Specifications, General Electric BWR/6 Plants, NUREG-1434, Volume 1, Specifications, and Volume 2, Bases, Revision 5.0, September 2021 (ML21271A582 and ML21271A596, respectively).

1 systems that the ECCS instrumentation actuates are low-pressure core spray (LPCS), LPCI, 2 high pressure core spray (HPCS), ADS, and the diesel generators.

3 4 The low-pressure ECCS subsystems are designed to mitigate a large break LOCA where 5 reactor vessel pressure rapidly decreases to the point at which the low-pressure ECCS pumps 6 can inject water. There are two redundant divisions for each of the low-pressure ECCS 7 subsystems. For example, BWR/4 plants typically have two LPCI subsystems and two CS 8 subsystems. BWR/6 plants typically have one LPCS subsystem and three LPCI subsystems.

9 10 The high-pressure ECCS subsystem is designed to mitigate small break LOCAs during which 11 reactor vessel pressure remains higher than the ability of the low-pressure ECCS pumps to 12 inject water. There is a single high-pressure ECCS subsystem. For example, BWR/4 plants 13 have HPCI, and BWR/6 plants have HPCS.

14 15 The ADS provides redundancy for the single high-pressure ECCS subsystem. In the event of a 16 failure of the high-pressure ECCS subsystem, the ADS valves open to release reactor vessel 17 pressure to the suppression pool, rapidly reducing the pressure to the point at which a 18 low-pressure ECCS subsystem can inject water.

19 20 There are two ADS trip systems, designated in the STS as ADS Trip Systems A and B. Either 21 trip system can open all the ADS valves if drywell pressure (or a drywell pressure bypass timer 22 signal is present) and reactor vessel water level conditions are satisfied, the ADS initiation timer 23 has completed, and one low-pressure ECCS pump associated with the trip system is operating 24 as indicated by pump discharge pressure. Each of these conditions (e.g., pressure, level, and 25 timers) are described in more detail below.

26 27

• High pressure in the drywell could indicate a break in the reactor coolant pressure boundary.

28 Therefore, ADS receives one of the signals necessary for initiation from this Function to 29 minimize the possibility of fuel damage. However, if the event requiring ADS initiation occurs 30 outside the drywell (e.g., main steam line break outside containment), a high drywell 31 pressure signal may never be present. Therefore, in a typical BWR/4 plant the Automatic 32 Depressurization System Low Water Level Actuation Timer is used to bypass the Drywell 33 Pressure - High Function after a certain time period has elapsed. The typical BWR/6 design 34 has the same drywell pressure bypass function, but it is referred to as the ADS Bypass 35 Timer (High Drywell Pressure).

36 37

• Low reactor pressure vessel (RPV) water level indicates that the capability to cool the fuel 38 may be threatened. Should RPV water level decrease too far, fuel damage could result.

39 Therefore, ADS receives one of the signals (Level 1) necessary for initiation from this 40 Function. To prevent spurious initiation of the ADS due to spurious Level 1 signals, a 41 confirmatory low RPV water level signal (Level 3) must also be received before ADS 42 initiates.

43 44

• The ADS initiation timer delays depressurization of the reactor vessel to allow the 45 HPCI (BWR/4) or HPCS (BWR/6) system time to maintain reactor vessel water level. Since 46 the rapid depressurization caused by ADS operation is one of the most severe transients on 47 the reactor vessel, its occurrence should be limited. By delaying initiation of the ADS 48 Function, the operator is given the chance to monitor the success or failure of the HPCI or 49 HPCS system to maintain water level, and then to decide whether to allow ADS to initiate, to 50 delay initiation further by recycling the timer, or to inhibit initiation permanently.

51

1

• High pump discharge pressure signals from the low-pressure ECCS pumps are used as 2 permissives for ADS initiation, indicating that there is a source of low-pressure cooling water 3 available once the ADS has depressurized the vessel. The ADS valves will not open unless 4 at least one low-pressure ECCS pump is operating (i.e., both channels for the pump indicate 5 a high discharge pressure condition) to provide a source of coolant once the reactor vessel 6 has been depressurized. Any one of the six BWR/4 low pressure pumps or four BWR/6 low 7 pressure pumps is sufficient to permit automatic depressurization.

8 9 2.2 Proposed Changes to Standard Technical Specification 3.3.5.1, ECCS Instrumentation 10 11 The following safety evaluation (SE) subsections describe the proposed changes to STS 3.3.5.1 12 for NUREG-1433 (BWR/4) and NUREG-1434 (BWR/6). Traveler TSTF-592 provided STS 13 redline/strikeout mark-ups showing the changes described below.

14 15 2.2.1 Proposed Changes to NUREG-1433 STS 3.3.5.1, ECCS Instrumentation 16 17

• STS Table 3.3.5.1-1 is revised to reference Condition H instead of Condition G for 18 Functions 4.e, 4.f, 4.h, 5.e, 5.f, and 5.h.

19

• STS 3.3.5.1, Required Action G.1, is revised to delete the Note.

20

• STS 3.3.5.1 is revised to add a new Condition H and associated remedial actions.

21 o Condition H states, As required by Required Action A.1 and referenced in 22 Table 3.3.5.1-1.

23 o Required Action H.1 states, Declare ADS valves inoperable, and is modified by 24 two Notes. The first Note limits the Required Action applicability to Functions 4.e, 25 4.f, 5.e, and 5.f. The second Note limits the Required Action applicability to when 26 both ADS Trip Systems are inoperable due to Core Spray/LPCI Pump Discharge 27 Pressure - High channels being inoperable. The Completion Time is 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from 28 discovery of loss of ADS initiation capability in both trip systems.

29 o Required Action H.2 states, Restore affected channels to OPERABLE status, 30 and is modified by two Notes. The first Note limits the Required Action 31 applicability to Functions 4.e, 4.f, 5.e, and 5.f. The second Note limits the 32 Required Action applicability to when one ADS Trip System is inoperable due to 33 Core Spray/LPCI Pump Discharge Pressure - High channels being inoperable.

34 The Completion Time is 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> from discovery of inoperable channels 35 concurrent with HPCI or RCIC [reactor core isolation cooling] inoperable, and 36 8 days from discovery of loss of inoperable channels. The option of including a 37 Risk Informed Completion Time alternative is included.

38 o Required Action H.3 states, Restore channel to OPERABLE status, with a 39 Completion Time of 30 days.

40

• STS 3.3.5.1 current Action H is renamed Action I, and is modified to include the new 41 Condition H.

1 2.2.2 Proposed Changes to NUREG-1434 STS 3.3.5.1, ECCS Instrumentation 2

3

• STS Table 3.3.5.1-1 is revised to reference Condition H instead of Condition G for 4 Functions 4.e, 4.f, 4.h, 5.e, and 5.g.

5

• STS 3.3.5.1, Required Action G.1, is revised to delete the Note.

6

• STS 3.3.5.1 is revised to add a new Condition H and associated remedial actions.

7 o Condition H states, As required by Required Action A.1 and referenced in 8 Table 3.3.5.1-1.

9 o Required Action H.1 states, Declare ADS valves inoperable, and is modified by 10 two Notes. The first Note limits the Required Action applicability to Functions 4.e, 11 4.f, and 5.e. The second Note limits the Required Action applicability to when 12 both ADS trip systems are inoperable due to LPCS/LPCI Pump Discharge 13 Pressure - High channels being inoperable. The Completion Time is 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from 14 discovery of loss of ADS initiation capability in both trip systems.

15 o Required Action H.2 states, Restore affected channels to OPERABLE status, 16 and it is modified by two Notes. The first Note limits the Required Actions 17 applicability to Functions 4.e, 4.f, and 5.e. The second Note limits the Required 18 Actions applicability to when one ADS trip system is inoperable due to 19 LPCS/LPCI Pump Discharge Pressure - High channels being inoperable. The 20 Completion Time is 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> from discovery of inoperable channels concurrent 21 with HPCS or RCIC inoperable, and 8 days from discovery of inoperable 22 channels. The option of including a Risk Informed Completion Time alternative is 23 included.

24 o Required Action H.3 states, Restore channel to OPERABLE status, with a 25 Completion Time of 30 days.

26

• STS 3.3.5.1 current Action H is renamed Action I, and is modified to include the new 27 Condition H.

28 2.2.3 Proposed Changes to the Presentation of Risk Informed Completion Times.

29 The presentation of Risk Informed Completion Times (RICT) applicable to Completion Times 30 that state from discovery is revised as follows to provide consistency and clarity, without 31 changing the intent of the TS.

32 NUREG-1433 TS 3.3.5.1, Required Action F.2 Completion Time currently states (in part):

33

• 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> from discovery of inoperable channel concurrent with HPCI or reactor core 34 isolation cooling (RCIC) inoperable 35 [OR 36 In accordance with the Risk Informed Completion Time Program]

1 The Completion Time is revised to state:

2

• 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> [or in accordance with the Risk Informed Completion Time Program] from 3 discovery of inoperable channel concurrent with HPCI or reactor core isolation cooling 4 (RCIC) inoperable.

5 NUREG-1433 TS 3.3.5.1, Required Action G.2 Completion Time currently states (in part):

6

• 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> from discovery of inoperable channel concurrent with HPCI or RCIC inoperable 7 [OR 8 In accordance with the Risk Informed Completion Time Program]

9 The Completion Time is revised to state:

10

• 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> [or in accordance with the Risk Informed Completion Time Program] from 11 discovery of inoperable channel concurrent with HPCI or RCIC inoperable.

12 NUREG-1434 TS 3.8.1, Required Action A.3 Completion Time currently states (in part):

13

• 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> from discovery of two divisions with no offsite power 14 [OR 15 In accordance with the Risk Informed Completion Time Program]

16 The Completion Time is revised to state:

17

• 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> [or in accordance with the Risk Informed Completion Time Program] from 18 discovery of two divisions with no offsite power 19 2.3 Applicable Regulatory Requirements and Guidance 20 21 As described in the Commissions Final Policy Statement on Technical Specifications 22 Improvements for Nuclear Power Reactors (58 FR 39132, dated July 22, 1993), the NRC and 23 industry task groups for new STS recommended that improvements include greater emphasis 24 on human factors principles in order to add clarity and understanding to the text of the STS, and 25 provide improvements to the Bases of the STS, which provide the purpose for each requirement 26 in the STS. The improved vendor-specific STS were developed and issued by the NRC in 27 September 1992.

28 29 Section IV, The Commission Policy, of the Final Policy Statement on Technical Specifications 30 Improvements for Nuclear Power Reactors states, in part:

31 32 The purpose of Technical Specifications is to impose those 33 conditions or limitations upon reactor operation necessary to 34 obviate the possibility of an abnormal situation or event giving rise 35 to an immediate threat to the public health and safety by 36 identifying those features that are of controlling importance to

1 safety and establishing on them certain conditions of operation 2 which cannot be changed without prior Commission approval.

3 4 [T]he Commission will also entertain requests to adopt portions 5 of the improved STS [(e.g., TSTF-592)], even if the licensee does 6 not adopt all STS improvements. The Commission encourages 7 all licensees who submit Technical Specification related submittals 8 based on this Policy Statement to emphasize human factors 9 principles.

10 11 In accordance with this Policy Statement, improved STS have 12 been developed and will be maintained for each NSSS [nuclear 13 steam supply system] owners group. The Commission 14 encourages licensees to use the improved STS as the basis for 15 plant-specific Technical Specifications. [I]t is the Commission 16 intent that the wording and Bases of the improved STS be used 17 to the extent practicable.

18 19 The Summary section of the Final Policy Statement on Technical Specifications Improvements 20 for Nuclear Power Reactors states, in part:

21 22 Implementation of the Policy Statement through implementation of 23 the improved STS is expected to produce an improvement in the 24 safety of nuclear power plants through the use of more 25 operator-oriented Technical Specifications, improved Technical 26 Specification Bases, reduced action statement induced plant 27 transients, and more efficient use of NRC and industry resources.

28 29 The regulations in Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.36(a)(1) 30 require that:

31 32 Each applicant for a license authorizing operation of a 33 utilization facility shall include in his application proposed technical 34 specifications in accordance with the requirements of this section.

35 A summary statement of the bases or reasons for such 36 specifications, other than those covering administrative controls, 37 shall also be included in the application, but shall not become part 38 of the technical specifications.

39 40 The regulations in 10 CFR 50.36(b) require that:

41 42 Each license authorizing operation of a utilization facility will 43 include technical specifications. The technical specifications will 44 be derived from the analyses and evaluation included in the safety 45 analysis report, and amendments thereto, submitted pursuant to 46 [10 CFR] 50.34 [Contents of applications; technical information].

47 The Commission may include such additional technical 48 specifications as the Commission finds appropriate.

49 50 The categories of items required to be in the TS are listed in 10 CFR 50.36(c). The regulation at 51 10 CFR 50.36(c)(2) requires that TS include limiting conditions for operations (LCOs). Per

1 10 CFR 50.36(c)(2)(i), LCOs are the lowest functional capability or performance levels of 2 equipment required for safe operation of the facility. The regulation also requires that when an 3 LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any 4 remedial action permitted by the TS until the condition can be met.

5 6 The NRC staffs guidance for the review of TS is in NUREG-0800, Standard Review Plan for 7 the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light-Water Reactor]

8 Edition (SRP), Chapter 16.0, Technical Specifications, Revision 3, dated March 2010 9 (ML100351425). As described therein, as part of the regulatory standardization effort, the NRC 10 staff has prepared STS for each of the LWR nuclear designs. Accordingly, the NRC staffs 11 review includes consideration of whether the proposed changes are consistent with the 12 applicable referenced STS, as modified by NRC-approved travelers. In addition, the SRP states 13 that comparing the change to previous STS can help clarify the STS intent.

14 15

3.0 TECHNICAL EVALUATION

16 The NRC staff reviewed Traveler TSTF-592, Revision 2, which proposed changes to 17 NUREG-1433 and NUREG-1434. The regulatory framework the NRC staff used to determine 18 the acceptability of the proposed changes consists of the requirements and guidance listed in 19 section 2.3 of this SE. The NRC staff reviewed the proposed changes to determine whether the 20 proposed changes to the STS meet the standards for TS in 10 CFR 50.36(c)(2)(i), as well as 21 conform to the Final Policy Statement on Technical Specifications Improvements for Nuclear 22 Power Reactors.

23 The OPERABILITY of the ECCS instrumentation is dependent upon the OPERABILITY of the 24 individual instrumentation Functions specified in STS Table 3.3.5.1-1. Each Function must have 25 a required number of OPERABLE channels. When a channel is discovered inoperable, in 26 applicable modes or other specified conditions, STS 3.3.5.1 Condition A is entered for that 27 channel and provides for transfer to the appropriate subsequent Condition by Required 28 Action A.1. Required Action A.1 directs entry into the appropriate Condition referenced in 29 Table 3.3.5.1-1. The applicable Condition referenced in Table 3.3.5.1-1 is Function dependent.

30 NUREG-1433 Table 3.3.5.1-1 currently references Condition G for ECCS Instrumentation 31 Functions 4.c, 4.e, 4.f, 4.g, 4.h, 5.c, 5.e, 5.f, 5.g, and 5.h. NUREG-1434 Table 3.3.5.1-1 32 currently references Condition G for ECCS Instrumentation Functions 4.c, 4.e, 4.f, 4.g, 4.h, 5.c, 33 5.e, 5.f, and 5.g. Inoperability of a single ECCS instrumentation channel associated with the 34 Functions identified above ultimately, if not restored after a maximum of 8 days, results in entry 35 into Condition H, the immediate declaration of the ADS valves as inoperable, and a plant 36 shutdown.

37 As an example, inoperability of a single pump pressure channel (NUREG-1433 Table 3.3.5.1-1 38 Function 4.e, 4.f, 5.e, or 5.f or NUREG-1434 Table 3.3.5.1-1 Function 4.e, 4.f, or 5.e), if not 39 restored in 8 days, would result in declaring ADS valves inoperable, leading to a plant 40 shutdown. However, due to redundancy in pump pressure channels, the loss of a single pump 41 pressure channel does not result in a loss of ADS initiation capability. Similarly, the loss of a 42 single manual initiation channel (e.g., NUREG-1433 Table 3.3.5.1-1 Function 4.h or 5.h, or 43 NUREG-1434 Table 3.3.5.1-1 Function 4.h or 5.g), if not restored within 8 days would result in a 44 plant shutdown. However, the manual initiation function does not impact automatic initiation 45 capability and is not assumed in any accident or transient analysis.

1 Traveler TSTF-592 proposed to revise the ADS instrumentation remedial action requirements 2 contained in the ECCS instrumentation specification, STS 3.3.5.1, to correct overly restrictive 3 action requirements, and to treat less significant channel inoperabilities consistently.

4 3.1 Evaluation of Changes to STS Table 3.3.5.1-1 5

6 NUREG-1433 Table 3.3.5.1-1 Functions 4.c, 4.e, 4.f, 4.g, 4.h, 5.c, 5.e, 5.f, 5.g, and 5.h, and 7 NUREG-1434 Table 3.3.5.1-1 Functions 4.c, 4.e, 4.f, 4.g, 4.h, 5.c, 5.e, 5.f, and 5.g currently 8 reference Condition G.

9 Traveler TSTF-592 proposed to revise STS Table 3.3.5.1-1 to reference new Condition H 10 instead of the current Condition G for ADS Trip System Functions associated with low pressure 11 pumps and manual initiation. Timer Functions (NUREG-1433 Function 4.c, 4.g, 5.c, and 5.g; 12 and NUREG-1434 Function 4.c, 4.g, 5.c, and 5.f) remain referenced to Condition G.

13 The proposed change to STS Table 3.3.5.1-1 is acceptable because it is a conforming change 14 necessary to implement the new Action H remedial actions proposed by Traveler TSTF-592.

15 The acceptability of new Action H remedial actions is evaluated in section 3.3 of this SE.

16 3.2 Evaluation of Changes to STS 3.3.5.1 Required Action G.1 17 18 NUREG-1433 STS 3.3.5.1 Required Action G.1 currently contains a Note that states, Only 19 applicable to Functions 4.c, 4.e, 4.f, 4.g, 5.c, 5.e, 5.f, and 5.g. NUREG-1434 STS 3.3.5.1 20 Required Action G.1 currently contains a Note that states, Only applicable to Functions 4.c, 21 4.e, 4.f, 4.g, 5.c, 5.e, and 5.f.

22 Traveler TSTF-592 proposed to revise Required Action G.1 to delete the Note because the 23 Note is no longer necessary given the changes to STS Table 3.3.5.1-1 discussed in section 3.1 24 of this SE, wherein STS Table 3.3.5.1-1 is revised such that Condition G is only referenced from 25 ADS Trip System Functions associated with timers (NUREG-1433 Function 4.c, 4.g, 5.c, and 26 5.g; and NUREG-1434 Function 4.c, 4.g, 5.c, and 5.f).

27 The proposed change to STS 3.3.5.1 Required Action G.1 is acceptable because it is a 28 conforming change necessary to implement the new Action H remedial actions proposed 29 by Traveler TSTF-592. The acceptability of new Action H remedial actions is evaluated in 30 section 3.3 of this SE.

31 32 3.3 Evaluation of New Action H to STS 3.3.5.1 33 NUREG-1433 STS 3.3.5.1, proposed new Condition H, is referenced to Functions 4.e, 4.f, 4.h, 34 5.e, 5.f, and 5.h. Similarly, NUREG-1434 STS 3.3.5.1, proposed new Condition H, is referenced 35 to Functions 4.e, 4.f, 4.h, 5.e, and 5.g. As described in section 3.1 of this SE, these Functions 36 were previously referenced to existing Condition G. These Functions are associated with 37 instrumentation channels for pump pressure and manual initiation. Each of these Functions are 38 described in more detail below.

39 The Traveler TSTF-592 justification for shifting these Functions from current Condition G to 40 proposed new Condition H was to develop more appropriate remedial actions that account for 41 the redundancy and diversity of these channels, and whether the Function is assumed in the 42 accident analysis.

1 The NRC staff SE assessed if the proposed remedial actions ensured that appropriate actions 2 were taken for inoperable channels that 1) result in a loss of automatic initiation capability in 3 both ADS trip systems, 2) result in a loss of automatic initiation capability for one ADS trip 4 system, or 3) result in no loss of automatic initiation capability in either trip system but require 5 restoration per STS Table 3.3.5.1-1 to ensure overall redundancy and diversity of the ADS trip 6 system functions.

7 Pump Pressure Channels 8 For the ADS trip system design assumed in the STS, the ADS trip system logic will not permit 9 the ADS valves to open unless at least one low-pressure ECCS pump is operating to provide a 10 source of coolant to the reactor vessel once the reactor vessel has been depressurized. There 11 are six low-pressure ECCS pumps in BWR/4 plants and four low-pressure pumps in BWR/6 12 plants. One operating low-pressure ECCS pump is sufficient to permit automatic 13 depressurization. To determine if a pump is operating, two channels of discharge pressure 14 monitoring instrumentation are associated with each low-pressure ECCS pump. Both of a 15 pumps associated channels must actuate to satisfy the ADS trip system logic that indicates 16 pump operation.

17 The BWR/4 CS Pump A and LPCI Pumps A and D, and the BWR/6 LPCS Pump and LPCI 18 Pump A channels input to the ADS Trip System A logic. The BWR/4 CS Pump B and LPCI 19 Pumps B and C, and the BWR/6 LPCI Pumps B and C channels input to the ADS Trip System B 20 logic. Only a single low-pressure ECCS pump with two operable channels is required for the 21 associated ADS trip system to respond to design basis events. A single inoperable pump 22 discharge pressure channel cannot render the ADS initiation capability inoperable.

23 Traveler TSTF-592 identified that there are some BWR/4 plants with an ADS initiation design 24 that varies from the design assumed in the STS. The effect of these variations and applicability 25 of the traveler will need to be evaluated on a plant-specific basis.

26 As described in Traveler TSTF-592, current Required Action G.2 applies when any low-pressure 27 ECCS Pump Discharge Pressure - High channel is inoperable in either ADS trip system. The 28 Completion Time is based on discovery of loss of ADS initiation capability for one trip system.

29 There is not a loss of ADS initiation capability if there are at least two Pump Discharge Pressure 30 - High channels for one low-pressure ECCS pump operable in either ADS trip system.

31 Therefore, the current remedial actions for one inoperable channel are considered overly 32 restrictive. The new proposed remedial actions for inoperable pump pressure channels are 33 addressed in sections 3.3.2 through 3.3.4 of this SE.

34 Manual Initiation 35 According to the STS Bases, the ADS manual initiation Function is redundant to the automatic 36 protective instrumentation Functions. The manual initiation Function is not assumed in any 37 accident or transient analyses in the FSAR.

38 Currently, Required Action G.2 applies when any manual initiation channel is inoperable in 39 either ADS trip system. As described in Traveler TSTF-592, the manual initiation Function is not 40 assumed in any accident or transient analysis and therefore, there is not a loss of credited ADS 41 initiation capability with this Function inoperable. Current remedial actions require restoring a

1 channel to operable status within 8 days. Traveler TSTF-592 describes that the current remedial 2 actions for inoperable manual initiation channels are overly restrictive.

3 Restoration of a manual initiation channel to operable status ensures the overall redundancy 4 and diversity of the ADS functions. New remedial actions associated with the manual initiation 5 Function are addressed in section 3.3.4 of this SE.

6 3.3.1 New Condition H 7 NUREG-1433 and NUREG-1434 STS 3.3.5.1 new Condition H states As required by Required 8 Action A.1 and referenced in Table 3.3.5.1-1. This proposed change aligns with the proposed 9 change to Table 3.3.5.1-1 discussed in section 3.1 of this SE. The new Condition H wording is 10 the same as the current Condition G wording.

11 The NRC staff reviewed Traveler TSTF-592 and concluded that the proposed new Condition H 12 is appropriate. The NRC staffs rationale is that new Condition H is treated the same as current 13 Condition G, that is As required by Required Action A.1 and referenced in Table 3.3.5.1-1.

14 This change is necessary because it is a conforming change that is consistent with the 15 proposed changes to STS Table 3.3.5.1-1 and is necessary to implement new Required Actions 16 and associated Completion Times. Therefore, based on the discussion above, the NRC staff 17 finds the proposed new Condition H acceptable.

18 3.3.2 New Required Action H.1 and Associated Completion Time 19 NUREG-1433 STS 3.3.5.1 new Required Action H.1 states, Declare ADS valves inoperable, 20 with a Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of loss of ADS initiation capability in both trip 21 systems. Required Action H.1 is modified by two Notes. Note 1 states, Only applicable for 22 Functions 4.e, 4.f, 5.e, and 5.f. Note 2 states, Only applicable when both ADS trips systems 23 are inoperable due to Core Spray/LPCI Pump Discharge Pressure - High channels inoperable.

24 NUREG-1434 STS 3.3.5.1 new Required Action H.1 states, Declare ADS valves inoperable, 25 with a Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of loss of ADS initiation capability in both trip 26 systems. Required Action H.1 is modified by two Notes. Note 1 states, Only applicable for 27 Functions 4.e, 4.f, and 5.e. Note 2 states, Only applicable when both ADS trips systems are 28 inoperable due to LPCS/LPCI Pump Discharge Pressure - High channels inoperable.

29 By Note 1, new Required Action H.1 is applicable to Functions associated with pump pressure 30 channels. This Note indicates that not all the Functions that are associated with new Condition 31 H are applicable to the new Required Action H.1. The Functions that are not identified in the 32 Note are excluded from the Required Action. The excluded Functions are associated with 33 manual initiation. The manual initiation Function is addressed in new Required Action H.3 and 34 evaluated in section 3.3.4 of this SE.

35 There are two ADS trip systems, designated as ADS Trip Systems A and B. A single ADS trip 36 system can initiate opening of the ADS valves constituting ADS initiation capability. Thus, 37 ADS initiation capability is lost when both trip systems are unable to initiate opening of the 38 ADS valves. Due to the proposed Note 2, new Required Action H.1 is only applicable when 39 multiple low pressure pump discharge pressure - high channels are inoperable such that both 40 ADS Trip Systems A and B lose initiation capability and are inoperable.

1 New Required Action H.1 provides requirements that address the loss of Trip Systems A and B 2 due to inoperable pump pressure channels. New Required Action H.1 is intended to ensure that 3 appropriate actions are taken if a combination of pump pressure channels are inoperable such 4 that neither ADS Trip System A nor B has two operable pressure channels associated with one 5 low-pressure ECCS pump.

6 The NRC staff reviewed Traveler TSTF-592 and concluded that the proposed new Required 7 Action H.1 and associated Completion Time are appropriate. The NRC staffs rationale is that 8 the proposed remedial actions for a loss of automatic initiation capability in both ADS trip 9 systems are treated the same as the current remedial actions for a loss of automatic initiation 10 capability in both ADS trip systems (see existing Required Action G.1 and its associated 11 Completion Time). Therefore, because the proposed remedial actions ensure that appropriate 12 actions would be taken for inoperable pump pressure channels that result in a loss of automatic 13 initiation capability in both ADS trip systems, consistent with existing Required Action G.1 and 14 associated Completion Time, the NRC staff finds the proposed new Required Action H.1 and 15 associated Completion Time are acceptable.

16 3.3.3 New Required Action H.2 and Associated Completion Times 17 NUREG-1433 STS 3.3.5.1 new Required Action H.2 states, Restore affected channels to 18 OPERABLE status, with Completion Times the same as the Completion Times for current 19 Required Action G.2. Required Action H.2 is modified by two Notes. Note 1 states, Only 20 applicable for Functions 4.e, 4.f, 5.e, and 5.f. Note 2 states, Only applicable when one ADS 21 trip system is inoperable due to Core Spray/LPCI Pump Discharge Pressure - High channels 22 inoperable.

23 NUREG-1434 STS 3.3.5.1 new Required Action H.2 states, Restore affected channels to 24 OPERABLE status, with Completion Times like the Completion Times for current Required 25 Action G.2. Required Action H.2 is modified by two Notes. Note 1 states, Only applicable for 26 Functions 4.e, 4.f, and 5.e. Note 2 states, Only applicable when one ADS trip system is 27 inoperable due to LPCS/LPCI Pump Discharge Pressure - High channels inoperable.

28 By Note 1, new Required Action H.2 is only applicable to Functions associated with pump 29 pressure channels. This Note indicates that not all the Functions that are associated with new 30 Condition H are applicable to the Required Action H.2. The Functions that are not identified in 31 the Note are excluded from the Required Action. The excluded Functions are associated with 32 manual initiation. The manual initiation Function is addressed in new Required Action H.3 and 33 evaluated in section 3.3.4 of this SE.

34 There are two ADS trip systems, designated as ADS Trip Systems A and B. A single ADS trip 35 system can initiate opening of the ADS valves constituting ADS initiation capability. Thus, the 36 redundancy of ADS initiation capability is lost when one trip system is unable to initiate 37 opening of the ADS valves. By Note 2, new Required Action H.2 is only applicable when 38 multiple low pressure pump discharge pressure - high channels are inoperable such that one 39 ADS trip system loses initiation capability and is inoperable.

40 New Required Action H.2 provides requirements that address the loss of redundancy between 41 Trip Systems A and B due to inoperable pump pressure channels. New Required Action H.2 is 42 intended to ensure that appropriate actions are taken if there are not two operable pump

1 pressure channels associated with one low pressure pump within one ADS trip system, which 2 would result in loss of automatic initiation capability for an ADS trip system.

3 The NRC staff reviewed Traveler TSTF-592 and concluded that the proposed new Required 4 Action H.2 and associated Completion Times are appropriate. The NRC staffs rationale is that 5 the remedial actions for the loss of redundant automatic initiation capability (i.e., loss of 6 automatic initiation capability for one ADS trip system) due to pump pressure channels are 7 treated consistent with the current remedial actions for the loss of redundant automatic initiation 8 capability (see existing Required Action G.2 and its associated Completion Times). Additionally, 9 it was noted that both Completion Times contain a modified time zero associated with the 10 discovery of a loss of ADS initiation capability in one trip system for consistency with STS 11 Section 1.3. Therefore, because the proposed new remedial actions ensure that appropriate 12 actions would be taken for inoperable pump pressure channels that result in a loss of automatic 13 initiation capability for one ADS trip system, consistent with existing Required Action G.2 and 14 associated Completion Times and STS Section 1.3, the NRC staff finds the proposed new 15 Required Action H.2 and associated Completion Times acceptable.

16 3.3.4 New Required Action H.3 and associated Completion Time 17 NUREG-1433 and NUREG-1434 STS 3.3.5.1 proposed new Required Action H.3 states, 18 Restore channel to OPERABLE status with a Completion Time of 30 days.

19 Proposed new Required Action H.3, unlike proposed new Required Actions H.1 and H.2 20 described above, has no Note that limits the applicable Functions. Therefore, proposed new 21 Required Action H.3 is applicable to all Functions that reference Condition H in STS 22 Table 3.3.5.1-1. The Functions that reference Condition H in STS Table 3.3.5.1-1 are 23 associated with instrumentation for pump pressure and manual initiation. In particular, the 24 excluded Function (i.e., manual initiation) from new Required Actions H.1 and H.2 is addressed 25 in proposed new Required Action H.3.

26 There are two ADS trip systems, designated as ADS Trip Systems A and B. A single ADS trip 27 system can initiate opening of the ADS valves constituting ADS initiation capability. The 28 proposed new Required Action H.3 is intended to ensure that appropriate actions are taken if 29 inoperable channels do not result in a loss of automatic initiation capability in either trip system.

30 For example, the proposed new Required Action H.3 addresses the condition of inoperable 31 pump pressure channels where there is no loss of ADS initiation capability in both trip systems 32 (addressed by Required Action H.1) and there is no loss of redundant ADS initiation capability 33 (addressed by Required Action H.2). In addition, the proposed new Required Action H.3 34 addresses the condition of inoperable channels associated with manual initiation. According to 35 Traveler TSTF-592, the manual initiation Function is not credited in any accident or transient 36 analysis.

37 The NRC staff reviewed Traveler TSTF-592 and concluded that the proposed new Required 38 Action H.3 and associated Completion Time are appropriate. The NRC staffs rationale is that 39 the proposed new remedial action ensures that appropriate actions are taken if inoperable 40 channels result in no loss of automatic initiation capability in either ADS trip system; however, 41 the inoperable channels do require restoration per STS Table 3.3.5.1-1 to ensure overall 42 redundancy and diversity of the ADS functions. The new Completion Time ensures that the 43 plant will not be operated in a reduced capability configuration for a lengthy timeframe. The 44 30-day Completion Time is based on operating experience, the consideration that there are

1 multiple channels available for meeting the lower pressure ECCS pump discharge pressure 2 permissive, and the availability of the automatic ADS initiation. Therefore, because the 3 proposed new remedial action ensures that appropriate actions would be taken for inoperable 4 channels that result in no loss of automatic initiation capability for either ADS trip system, in a 5 reasonable timeframe, the NRC staff finds the proposed new Required Action H.3 and 6 associated Completion Time acceptable.

7 3.4 Evaluation of New Action I 8 NUREG-1433 and NUREG-1434 STS 3.3.5.1 currently reference Condition H as the default 9 action when the Required Action and associated Completion Time of an associated Condition is 10 not met.

11 Traveler TSTF-592 proposed to revise NUREG-1433 and NUREG-1434 STS 3.3.5.1 to create a 12 new Condition H and associated remedial actions, which is evaluated in section 3.3 of this SE.

13 Therefore, Traveler TSTF-592 proposed to renumber the current default action (Condition H) as 14 Condition I. In addition, the proposed new Condition H was included in the scope of the 15 proposed new Condition I.

16 The NRC staff finds that the new proposed default action, Condition I and associated remedial 17 actions, are acceptable because it is a conforming change necessary to implement the 18 proposed new Condition H.

19 3.5. Evaluation of Proposed Changes to the Presentation of RICT 20 Traveler TSTF-592, Section 3, Technical Evaluation, describes that there are three instances 21 in the STS where the presentations of Completion Times with the option to apply RICT are 22 inconsistent. This inconsistency was introduced in TSTF-505, Provide Risk-Informed Extended 23 Completion Times, Revision 2, which was incorporated into Revision 5 of the STS.

24 Section 2.2 of this SE identifies the proposed changes to NUREG-1433 and NUREG-1434 25 presentation of RICT to address the three instances in the STS where the presentation of 26 Completion Times with the option to apply RICT are inconsistent. The proposed changes fix 27 inconsistencies with the presentation of Completion Times that incorporate a RICT option and 28 contain the expression from discovery, which indicates the Completion Time begins when the 29 conditions in the Completion Time are satisfied.

30 The NRC staff reviewed the proposed changes to the presentation of RICT described in 31 section 2.2 of this SE. The NRC staff finds the proposed changes provide consistency and 32 clarity, without changing the intent of the STS, and therefore are acceptable.

33

4.0 CONCLUSION

34 35 The NRC staff concludes that the proposed changes to STS 3.3.5.1 for BWR/4 and BWR/6 in 36 Traveler TSTF-592 are acceptable because the remedial actions to be taken until the LCO can 37 be met provide protection to the health and safety of the public. The NRC staff also concludes 38 that there is reasonable assurance that plants adopting TSTF-592 will continue to ensure that 39 when LCO 3.3.5.1 is not met, the licensee shall shut down the reactor or follow any remedial 40 action permitted by the TS until the condition can be met. Therefore, the NRC staff finds that the

1 proposed changes to STS 3.3.5.1 are acceptable because they continue to meet the 2 requirements of 10 CFR 50.36(c)(2)(i).

3 4 Principal Contributors: C. Ashley, NRR/DSS/STSB 5 N. Karipineni, NRR/DSS/SCPB 6 H. Vu, NRR/DEX/EICB 7

8 Date: December 18, 2023