ML033370415

Slides, Summary of Public Meeting with South Texas Project Nuclear Operating Co on Risk-Informed Inservice Testing Issues

ML033370415
Person / Time
Site:	South Texas
Issue date:	12/05/2003
From:	Office of Nuclear Reactor Regulation
To:
Jaffe D, NRR/DLPM, 415-1439
Shared Package
ML033450054	List: ML033370415 ML033450033
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Download: ML033370415 (55)

Text

1' I Risk-informed - ic-.Testing Risk-Informed Inservice Testing 11/13/03 1

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RISK-INFORMED INSERVICE TESTING AT THE -SOUTH. TEXAS PROJECT A proposal to apply risk-informed criteria to inservice testing of- pumps and valves 11/13/03 2

STP Participants e Scott Head Manager,.

Licensing I e Brad Scott Inservice Testing Program Coordinator

• Bill Stillwell Supervisor, Risk. Management

• Glen Schinzel Supervisor, Risk Implementation 11/13/03 3

Purpose of Meeting

• Explain rationale for applying RI criteria to IST of pumps and valves

• Receive NRC feedback on proposed RI-IST submittal 11/13/03 4

(. -

Agenda e Describe RI-IST methodology to support resubmittal using SONGS approach.

• Compare Rl-IST treatment determination to GQA risk categorization for Exemption.

• GQA and RI-IST comparison.

• Address NRC's questions from previous submittal.

11/13/03 5

History RI-IST Special Treatment Exemption

• 12/1999

• 07/13/1999 RI-IST process begins Exemption request submitted

• 08/31/2000

• 05/21/2001 Revised exemption request submitted Relief request submitted

• 11/15/2000

• 04/09/2002 NRC preliminary assessment NRC questions issued

• 05/08/2001 Revised exemption request submitted

• 11/12/2002

• 06/05/2001 Revised relief request submitted Preliminary safety evaluation

• 06/08/2001

• 05/29/2003 Environmental assessment/no significant hazards NRC questions issued

• 07/03/2001

• 09/12/2003 Comments on Safety Evaluation Withdrawn

• 08/03/2001 NRC Safety Evaluation - Approval 11/13/03 6

Proposed Alternative Define inservice testing treatments for non-exempt components consistent with importance, Establish test intervals and treatments for pumps and valves using risk-informed classification as an alternative to ASME Section Xl requirements.

11/13/03 7

Method of Application

• Proposed application of risk-informed classification of SSCs at STP follows the San Onofre approach.

• San Onofre approach has been approved by the NRC.

• RG 1 175 criteria are satisfied by the test strategies.

11/13/03 8

Benefits of RI-IST

• Enhance nuclear safety

• Focus resources on highest risk equipment

• Save $80,000 per year 11/13/03 9

Key Differences from Previous Submittal

• F-V threshold adjusted from 0.005 to 0.001 e Treatment of common cause in RAW adjusted 11/13/03 10

Proposed Risk Thresholds 11/13/03 11

STP Exemption (GQA) Thresholds 11/13/03 12

STP F-V Number per SONGS Template o All failure modes are included in F-V values

• Common cause is included. Results in a higher F-V value, thus encompassing more SSCs as highly significant to safety.

• Threshold for F-V is .001 for components highly significant to safety, instead of .005.

This includes more SSCs as being highly significant to safety.

• F-V (high or low) determines treatment.

11/13/03 13

STP RAW per SONGS Template o Common cause is not included in the RAW.

• Results in lower RAW, encompassing fewer components in mid-range of safety significance.

o RAW is reviewed if component is classed as having low safety significance.

• RAW of 2 is consistent with code case OMN-3.

11/13/03 14

Risk-Informed Classifications

• If F-V value is greater than 0.001, treatment classification is "high".

• If F-V value is less than 0.001 and RAW > 2, treatment classification is "low/high".

• If F-V value is less than 0.001 and RAW < 2, treatment classification is "low".

11/13/03 15

Comparison With Other Plants Comanche Rank Peak SONGS STP IST 138 SSCs- 57 SSCs- 71 SSCs -

H Ig h 20.7% 13.1% 13.2%

NA 32 SSCs - 22 SSCs -

Low/H igh 7.4% 4.1%

529 SSCs - 346 SSCs - 444 SSCs -

LOW 79.3% 79.5% 82.7%

11/13/03 16

Relationship to Exemption

• Exemption Request removes designated SSCs from scope of 10CFR5

• RI-IST categorizes by significance those SSCs remaining under the scope of 10CFR50.

• RI-IST will not affect GQA categorization results 11/13/03 17

Comparing Classifications

• There are no Ss in the Exemption categorized as having low safety significance or no risk significance that are also ranked "high" for RI-IST.

• SSCs categorized as having low safety significance or no risk significance are not in RI-IST scope.

11/13/03 18

Ranking Philosophies

• GQA

- Categorization intended for Global / General Use

- System functions are first identified and ranked

- Each component is then tied to the functions that the component supports

- Component categorized based on highest ranking function supported

- Some components downgraded based on redundancy, diversity, etc.

• IST

- Starts at component level and determines relative redundancy available for component and for the function being tested.

- Categorization of SSCs does not impact program scope

- Categorization adjusts test treatments only 11/13/03 19

RI-IST PROGRAM MATRIX IST TREATMENT HIGH LOW/HIGH LOW SSC Not Exempt SSC Not Exempt SSC Not Exempt HIGH 14 Valve Groups - 49 Valves 5 Valve Groups - 16 Valves 9 Valve Groups - 28 Valves 6 Pump Groups - 16 Pumps 1 Pump Group - 3 Pumps 1 Pump Group - 3 Pumps 0

SSC Not Exempt SSC Not Exempt SSC Not Exempt I-MEDIUM 2 Valve Groups - 6 Valves 1 Valve Group - 3 Valves 43 Valve Groups - 150 Valves 0 0 Pump Groups - 0 Pumps 0 Pump Groups - 0 Pumps 2 Pump Groups - 4 Pumps z

0 I- SSC Exempt SSC Exempt SSC Exempt a-w LOW NONE NONE 122 Valve Groups - 251 Valves xj w 3 Pump Groups - 8 Pumps SSC Exempt SSC Exempt SSC Exempt NRS NONE NONE NONE 20 111/13/03 1/13/03 20

Auxiliary Feedwater System 11/13/03 21

Group AF07 - AFW Auto Recirc Valve AF001 1 GQA RI-IST

• Rank = High

• Treatment = Low/High

• Bases

• F-V = 7.5E-4 Supports the following system functions:

• RAW=2.9

- High risk

• Bases

• Prevent pump damage from insufficient flow or excessive flow - Valve opens, allows flow to SG during

• Supply feedwater to SGs to remove reactor accident core decay heat if normal feedwater is unavailable - 2/4 AF trains required for immediate

- Medium risk response; 1 train for long-term

• Provide feedwater to the SGs during startup, - Valve opens to allow minimum initial fill & wet lay-up, shutdown, hot standby, recirculation flow (not safety; pump and cool-down & heatup protection only)

• GQA ranked High based on: - RI-IST treatment

- Initial PRA rank of High, subsequently lowered to Medium

• F-V and RAW

- Supports High risk functions

• Valve failure affects only 1 of 4

- No credit taken for redundancy AFWP

• AFW x-connections allow flow from any AFWP to any SG 11/13/03 22

Emergency Core Cooling System I

I I

• S25

-S113

-SI14 S106 I

I 1MB I &M CIORC 11/13/03 23

Group RH01 - RHR HX Control AOVs CV0864, 5 6 GQA RI-IST

• Rank = Medium

• Treatment = Low

• Bases

• F-V = 3.OE-4 Supports the following system functions:

• RAW = 1.2

- High risk

• Bases

• Long term decay heat removal during the Si recirculation phase of a small or large break LOCA - Open for normal lineup for SI

• Serve as part of the ECCS LHSI flow path during SI and long-term recirculation

• Remove core decay heat and sensible heat to - NO, FO, de-energized in achieve and maintain cold shutdown following:

feedwater line break, secondary steam line break, "open" during Modes 1-3 and SGTR - Control function not safety; full

• Remove residual and sensible heat during drain down open allows max heat removal and mid-loop operations

- Medium risk - R-IST treatment

• Remove residual and sensible heat during reactor hot

• F-V and RAW and cold shutdown following normal reactor shutdown

• Provide pressure boundary

• 3 trains RHR available; only 1 required

• GQA ranked Medium based on:

- Initial PRA rank of Medium, subsequently lowered to Low

• NO, FO, de-energized in

- Redundant Trains "open" in Modes 1-3

- Power removed during modes 1, 2, and 3

- Valve is normally open and stays open to support the High risk functions. Transfer closed is not a credible failure 11/13/03 24

Group RHO6 - RHR Discharge Check Valve GQA RI-IST

• Rank = High

• Treatment = Low

• Bases

• F-V = 6.7E-5 Supports the following system functions:

• RAW= 1.1

- High risk

• Bases

• Long term decay heat removal during the Si recirculation phase of a small or large break LOCA - Open to allow safety

• Serve as part of the ECCS LHSI flow path during cooldown using RHR safety injection

- "Close" not safety function

• Remove core decay heat and sensible heat to achieve and maintain cold shutdown following: feedwater line - RI-IST break, secondary steam line break, and SGTR

• F-V and RAW

• Remove residual and sensible heat during drain down and mid-loop operations

• 3 trains RHR available;

- Medium risk only 1 required

• Remove residual and sensible heat during reactor hot and cold shutdown following normal reactor shutdown

• Provide pressure boundary

• GQA ranked High based on:

- Initial PRA rank of High, subsequently lowered to Low

- Supports High risk functions

- No credit taken for redundancy 11/13/03 25

Group RHO8 - RHR Cold Leg nj Check Valve GQA RI-IST

• Rank = High

• Treatment = Low

• Bases

• F-V = 9.2E-5 Supports the following system functions: - RAW= 1.2

- High risk

• Bases

• Long term decay heat removal during the SI recirculation phase of a small or large break LOCA - Close and leaktight to maintain RCPB

• Serve as part of the emergency core cooling system - Open to allow safety cooldown with (ECCS) LHSI flow path during safety injection RHR

• Remove core decay heat and sensible heat from the - Open to allow SI path for LHSI reactor core and RCS to achieve and maintain cold shutdown after feedwater line break, secondary - RI-IST treatment steam line break, and SGTR

• F-V and RAW

• Remove residual and sensible heat from the reactor

• 3 trains RHR available; only 1 core and the RCS during drain down and mid-loop operations required

- Medium risk

• 3 trains LHSI available; only 1

• Remove residual and sensible heat from the reactor required core and the RCS during reactor hot and cold

• valves are closed and leak tested shutdown following normal shutdown prior to reactor startup per TS

• Provide pressure boundary

• leak-by condition monitored daily

• GQA ranked High based on: per RCS inventory TS requirement

- Initial PRA rank of High, subsequently lowered to Medium

- Supports High risk functions No credit taken for redundancy 11/13/03 26

Group S113 - HHSI Recirc Isol MOV S1001 1, 12 GQA RI-IST

• Rank = High

• Treatment = High

• Basis

• F-V = 5.2E-3 Supports the following system functions:

• RAW=3.3

- High risk Cold leg recirculation mode - recirculate

• Bases borated water from the containment sump, - Remain open for HHSI minimum through the RHR heat exchangers, and recirculation path back to the RCS cold legs

- Medium risk - Close to isolate flow to RWST

• Support automatic switchover from the during switchover to sump injection mode to the cold leg recirculation - NO, FAI mode (manual backup available)

• Prevent pump damage from insufficient or - RI-IST treatment excessive flow (orifices and mini-flow

• F-V lines)

• GQA ranked High based on:

• Valve FAI so "open" function is

- PRA rank of High satisfied even if valve fails

- Supports High risk functions

• Redundant closing function

- No credit taken for redundancy provided by 2 valves in series

• 2 additional HHSI trains provide Si if both valves fail to close 1 1/,13/03 27

Group S114 - LHSI Recirc Isol MOVs S10013 14 GQA RI-IST

• Rank = High

• Treatment= High

• Basis

• F-V=2.5E-3 Supports the following system functions:

• RAW= 1.2

- High risk

• Bases

• Cold leg recirculation mode - recirculate - Remain open for LHSI minimum borated water from the containment sump, through the RHR heat exchangers, and recirculation path back to the RCS cold legs - Close to isolate flow to RWST

- Medium risk during switchover to sump

• Support automatic switchover from the injection mode to the cold leg recirculation - NO, FAI mode (manual backup available) - RI-IST treatment

• Prevent pump damage from insufficient or excessive flow (orifices and mini-flow

• F-V lines)

• Valves FAI so "open" function is

• GQA ranked High based on: satisfied even if valves fail

- PRA rank of High

• Redundant closing function

- Supports High risk functions provided by 2 valves in series

- No credit taken for redundancy

• 2 additional LHSI trains provide SI if both valves fail to close 11/13/03 28

Group S121 - LHSI Containment Isol Check Valve GQA RI-IST

• Rank = High

• Treatment = Low

• Bases

• F-V = 4.8E-4 Supports the following system functions:

• RAW= 1.2

- High risk

• Bases

• Injection mode - deliver borated water from RWST and accumulators to RCS cold legs to make up for loss of - Close and leaktight for coolant resulting from a LOCA, rod ejection accident, or containment isolation; also close SGTR to prevent RHR backflow

• Cold leg recirculation mode - recirculate borated water from the containment sump, through the RHR heat - Open to allow LHSI during exchangers, and back to the RCS cold legs accident and sump recirculation

- Medium risk - Open to inject borated water

• Hot leg recirculation mode - recirculate borated water from the containment sump simultaneously to the RCS during long-term cooling (hot-leg hot legs by one train and to a cold leg by another train and cold-leg recirculation)

• GQA ranked High based on: - RI-IST treatment

- Initial PRA rank of High, subsequently lowered to Low

• F-V and RAW

- Supports High risk functions

• 2 additional LHSI trains to

- No credit taken for redundancy provide SI if one valve fails to open 11/13/03 29

Group S125 - Si Suction Check Valve S10002 GQA RI-IST

• Rank = High

• Treatment = Low

• Bases

• F-V = 3.9E-4 Supports the following system functions:

• RAW=3.5

- High risk

• Bases Injection mode - deliver borated water from RWST and accumulators to RCS cold legs to make up for loss of - Open to allow suction to LHSI, coolant resulting from a LOCA, rod ejection accident, or HHSI, CS pumps SGTR

• Injection mode - supply borated water to compensate for

- Close to prevent backflow to positive reactivity inserted and make up for shrinkage of RWST during sump recirculation reactor coolant from a decrease in temperature caused by - Check valves stop backflow from secondary steam line break, feedline break, or main steam line depressurization RWST until Si MOV0001 valves

- Supports the following Medium risk system function close

• Support the automatic switchover from the injection mode - RI-IST treatment to the cold leg recirculation mode

• F-V and RAW

• GQA ranked High based on:

- Initial PRA rank of High, subsequently lowered to

• Redundant closing function Medium provided by upstream MOV

- Supports High risk functions

• 2 additional trains of LHSI,

- No credit taken for redundancy HHSI, CS provide safety function if 1 valve fails 11/13/03 30

Group SILHP - LHSI Pump PA102 GQA RI-IST

• GQA Rank: High

• Treatment = Low

• Basis

• F-V=7.8E-4 Supports the following system functions:

• RAW = 1.2

- High risk

• Basis:

• Injection and Cold leg Recirc modes - F-V and RAW

- Medium risk - Active function to 'start and run' to

• Hot leg recirculation mode support injection and recirculation functions

- Low risk

- Redundancy exists with three 100%

• Pressure boundary and positive safety trains to satisfy the injection RCS volume control modes

• GQA ranked High based on - Diversity exists with 3 High Head pumps

- Initial PRA rank of High, to support recirculation and injection subsequently lowered to Medium*

- Supports High.risk functions

- No credit taken for redundancy 11/13/03 31

Group S106 - LHSI Isolation MOV GQA RI-IST

• GQA Rank: Medium

• Treatment = Low

• Basis

• F-V=4.3E-4 Supports the following system functions:

• RAW = 1.2

- High risk:

• Bases:

• Injection and Cold leg recirculation modes

- Valve is normally open - satisfies its safety

- Medium risk function

• Hot leg recirculation mode

- The 'remain open' function is passive

- Low risk

- IST testable function is to 'close on demand'

• Pressure boundary and Containment Isolation

- RI-IST Treatment of Low based on:

• GQA ranked Medium based on:

• Valve is normally in its required safety position -

- Initial PRA rank of Medium, subsequently no change of state required lowered to Low

• Redundancy exists with three 100% safety

- Redundant Trains trains to satisfy the injection modes

• Diversity exists with 3 High Head pumps to

- Valve is normally open and stays open to support recirculation and injection support the High risk functions. Transfer

• Valve is routinely monitored by other means to closed is not a credible failure check valve position and flow

- Valve is closed to isolate RHR from the LHSI pump when the RHR pump is used for long term accident recovery. Failure to close mitigated by the inside containment check valve.

11/13/03 32

Effects of R-IST on Ssc Treatments Component Type Requirement High Treatment Low/High Treatment Low Treatment Testing Code nserice Test Code Test on extended interval Code Test on extended interval Pumps with compensatory measure Performance (Vibration Monitoring, Oil (Vibration Monitoring, Oil (Vibration Monitoring, Oil Monitoring Analysis, Thermography, etc.) Analysis, Thermography, etc.) Analysis, Thermography, etc.)

Code Inservice Test and MOV MOV Periodic Verification MOV Periodic Verification Testing Periodic Verification Program Program Program MOVS Performance Periodic inspections and Periodic inspections and Periodic inspections and Monitoring maintenance actiAties maintenance acthities maintenance activties Testing Code Insernhce Test Code Test on extended interval Code Test on extended interval with compensatory measure AOVs Performance JOG AOV Testing Program JOG AOV Testing Program JOG AOV Testing Program Monitoring and Maintenance activities and Maintenance activities and Maintenance acthAties Notes: l I I I

1. Valves are exercised at least once every refuel cycle if practical. I ______________ _____________

2. Extended intervals will not exceed 6 years plus 25% grace except where allowed by. referenced programs or NUREG-1482.

3. Performance monitoring described above is in addition to monitoring as required by the Maintenance Rule Program and CAP.

4. Details of such activities are included in the RI-IST Program Summary. _

11/13/03 33

Effects of RI-IST on sSc Treatments Component Type Requirement High Treatment Low/High Treatment Low Treatment Testing Code nservice'Test Code Test on extended interval Code Test on extended interval HOVs, SOVs, and with compensatory measure Manual Valves Performance Periodic inspections and Periodic inspections and Periodic inspections and Monitoring maintenance activities maintenance activities maintenance activities Condition Monitoring IAW Condition Monitoring IAW Condition Monitoring IAW Testing ASME Code Case OMN-4 ASME Code Case OMN-4 ASME Code Case OMN-4 Check Valves (As endorsed in'RG 1.192) (As endorsed in RG 1.192) (As endorsed in RG 1.192)

Performance N/A N/A N/A

___________ M on itorin g _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Testing Code Inservice Test Code Inservice Test Code Inservice Test Relief Valves. Test results trending, tighter Test results trending, tighter Performance Test results trending, tighter Monitoring reset tolerances reset tolerances reset tolerances Notes:

1. Valves are exercised at least once every refuel cycle if practical. __________________________

2. Extended intervals will not exceed 6 years plus 25% grace except where allowed by referenced programs or NUREG-1482.

3. Performance monitoring described above is in addition to monitoring as required by the Maintenance Rule Program and CAP.

4. Details of such activities are included in the RI-IST Program Summary.

11/13/033 34

Response to RAI NRC Issue 1 The re-categorization process might not properly include components with important safety-significant functions within the scope of the RI-IST Program.

11/13/03 35

Response to Issue 1

• GQA ranking. is unaffected by RI.-IST importance determination.

• R-IST treatment strategy. process considers all safety significant functions for SSCs included in scope.

• R-IST ranking determines the treatment requirements for components remaining within the scope of the program.

11/13/03 36

NRC Issue 2 CDF and LERF must include the cumulative impacts to the IST program resulting from the exemption process and the proposed RI-IST Program.

11/13/03 37

Response to Issue 2

• CDF and LERF will include the cumulative impacts to the ST program.

• Changes in CDF and LERF will still meet the requirements of RG 1.174 and RG 1.175.

• LRS and NRS components contribute minimally to the overall CDF and LERF.

11/13/03 38

NRC Issue 3 Without sufficient justification that the ssc cannot be in a non-normal state, re-categorize these SSCs and test the risk-important function, even if STP considers the ssc to be passive.

11/13/03 39

Response to Issue 3

• All failure modes are considered in the F-V ranking.

11/13/03 40

NRC Issue 4.a The proposed RI-IST Program does not provide assurance that SSCs will be tested in a manner that collects sufficient performance information to support functionality over the test interval.

11/13/03 41

Response to Issue 4.a

@Treatments are consistent with those at SONGS.

• See slides 33 and 34.

11/13/03 42

NRC Issue 4.b STP does not indicate that data and information will be obtained to allow evaluation of operating characteristics for safety-related AOVs other than those HSS under the proposed program.

Implementation would not provide timely and systematic collection of data.

11/13/03 43

Response to Issue 4.b

• Treatments are consistent with those at SONGS.

• See slides 33 and 34.

11/13/03 44

NRC Issue 4.c The proposed program is inconsistent with RG 1.175 for testing of SSCs categorized as LSS under the proposed program using test methods that support the extended test intervals.

11/13/03 45

Response to Issue 4.c

• Treatments are consistent with those at SONGS.

• See slides 33 and 34.

11/13/03 46

NRC Issue 4.d The proposed RI-IST Program is inconsistent with the provisions for surveillance testing and monitoring of low safety-significant components which served as the basis for approval of the exemption request.

11/13/03 47

Response to Issue 4.d o The program follows SONGS approach for low risk SSCs remaining in scope of the IST program.

11/13/03 48

NRC Issue 5.a UFSAR states that HSS and MSS SSCs would continue to satisfy regulations, and HSS and MSS SSCs would be evaluated to determine whether enhanced treatment is warranted. The proposed program is inconsistent with the basis for the exemption, request.

11/13/03 49

Response to Issue 5.a

• The program follows SONGS approach for low risk SSCs remaining in scope of the IST program.

11/13/03 50

NRC Issue 5.b Proposed RI-IST Program does not specify adequate testing of safety significant functions of components where those functions could be, but are not, tested as part of the current IST program.

11/13/03 51

Response to Issue 5.b

• STP has added trending requirements for equipment not in the traditional scope of the OM Code.

11/13/03 52

NRC Issue 6 Implementation of defense strategies for common-cause failures has not been demonstrated to be sufficient to eliminate the need to address the potential for common cause failures under the RI-IST Program.

11/13/03 53

Response to Issue 6

• Common-cause failures across system boundaries are not routinely included in any PRA.

• STP includes common cause across multiple switchgear breakers for LOOP.

• STP includes models of common actuation systems with common cause included at the relay level.

11/13/03 54

Conclusions

• STP will submit an application consistent with the previously approved SONGS approach.

• Proposed alternative provides an acceptable level of quality and safety pursuant to 10CFR5055a(a) (3)(i) 11/13/03 55