ML033370415
| 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: |
| References | |
| Download: ML033370415 (55) | |
Text
1' I Risk-informed ic-.Testing Risk-Informed Inservice Testing 11/13/03 1
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- 1.
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 e Brad Scott
- Bill Stillwell Manager, Licensing I
Inservice Testing Program Coordinator 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 12/1999 RI-IST process begins 05/21/2001 Relief request submitted 04/09/2002 NRC questions issued 11/12/2002 Revised relief request submitted 05/29/2003 NRC questions issued 09/12/2003 Withdrawn Special Treatment Exemption 07/13/1999 Exemption request submitted 08/31/2000 Revised exemption request submitted 11/15/2000 NRC preliminary assessment 05/08/2001 Revised exemption request submitted 06/05/2001 Preliminary safety evaluation 06/08/2001 Environmental assessment/no significant hazards 07/03/2001 Comments on Safety Evaluation 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 1 75 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 1 1
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 I g 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 1 6
Relationship to Exemption
- Exemption Request removes designated SSCs from scope of 1 OCFR5
- 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.
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 0
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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 SSC Not Exempt SSC Not Exempt SSC Not Exempt MEDIUM 2 Valve Groups - 6 Valves 1 Valve Group - 3 Valves 43 Valve Groups - 150 Valves 0 Pump Groups - 0 Pumps 0 Pump Groups - 0 Pumps 2 Pump Groups - 4 Pumps SSC Exempt SSC Exempt SSC Exempt LOW NONE NONE 122 Valve Groups - 251 Valves 3 Pump Groups - 8 Pumps SSC Exempt SSC Exempt SSC Exempt NRS NONE NONE NONE 11/13/03 20 1 1/13/03 20
Auxiliary Feedwater System 11/13/03 21
Group AF07 - AFW Auto Recirc Valve AF001 1 GQA Rank = High Bases Supports the following system functions:
High risk Prevent pump damage from insufficient flow or excessive flow Supply feedwater to SGs to remove reactor core decay heat if normal feedwater is unavailable Medium risk Provide feedwater to the SGs during startup, initial fill & wet lay-up, shutdown, hot standby, and cool-down & heatup GQA ranked High based on:
Initial PRA rank of High, subsequently lowered to Medium Supports High risk functions No credit taken for redundancy RI-IST Treatment = Low/High F-V = 7.5E-4 RAW=2.9 Bases
- Valve opens, allows flow to SG during accident
- 2/4 AF trains required for immediate response; 1 train for long-term
- Valve opens to allow minimum recirculation flow (not safety; pump protection only)
- RI-IST treatment
- F-V and RAW
- Valve failure affects only 1 of 4 AFWP
Emergency Core Cooling System I
II
- S25
-S113
-SI14 S106 I
I 1MB I &M C I ORC 11/13/03 23
Group RH01 - RHR HX Control AOVs CV0864, 5 6 GQA Rank = Medium Bases Supports the following system functions:
High risk Long term decay heat removal during the Si recirculation phase of a small or large break LOCA
- Serve as part of the ECCS LHSI flow path during SI Remove core decay heat and sensible heat to achieve and maintain cold shutdown following:
feedwater line break, secondary steam line break, and SGTR Remove residual and sensible heat during drain down and mid-loop operations Medium risk Remove residual and sensible heat during reactor hot and cold shutdown following normal reactor shutdown Provide pressure boundary GQA ranked Medium based on:
Initial PRA rank of Medium, subsequently lowered to Low Redundant Trains 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 RI-IST Treatment = Low F-V = 3.OE-4 RAW = 1.2 Bases Open for normal lineup for SI and long-term recirculation NO, FO, de-energized in "open" during Modes 1-3 Control function not safety; full open allows max heat removal R-IST treatment
- F-V and RAW
- 3 trains RHR available; only 1 required
- NO, FO, de-energized in "open" in Modes 1-3 11/13/03 24
Group RHO6 - RHR Discharge Check Valve GQA Rank = High Bases Supports the following system functions:
High risk Long term decay heat removal during the Si recirculation phase of a small or large break LOCA Serve as part of the ECCS LHSI flow path during safety injection Remove core decay heat and sensible heat to achieve and maintain cold shutdown following: feedwater line break, secondary steam line break, and SGTR Remove residual and sensible heat during drain down and mid-loop operations Medium risk 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 RI-IST Treatment = Low F-V = 6.7E-5 RAW= 1.1 Bases Open to allow safety cooldown using RHR "Close" not safety function RI-IST
- F-V and RAW
- 3 trains RHR available; only 1 required 25
Group RHO8 - RHR Cold Leg nj Check Valve GQA Rank = High Bases Supports the following system functions:
High risk Long term decay heat removal during the SI recirculation phase of a small or large break LOCA Serve as part of the emergency core cooling system (ECCS) LHSI flow path during safety injection Remove core decay heat and sensible heat from the reactor core and RCS to achieve and maintain cold shutdown after feedwater line break, secondary steam line break, and SGTR Remove residual and sensible heat from the reactor core and the RCS during drain down and mid-loop operations Medium risk Remove residual and sensible heat from the reactor core and the RCS during reactor hot and cold shutdown following normal shutdown Provide pressure boundary GQA ranked High based on:
Initial PRA rank of High, subsequently lowered to Medium Supports High risk functions No credit taken for redundancy 1 1/13/03 RI-IST Treatment = Low F-V = 9.2E-5 RAW= 1.2 Bases Close and leaktight to maintain RCPB Open to allow safety cooldown with RHR Open to allow SI path for LHSI RI-IST treatment
- F-V and RAW
- 3 trains RHR available; only 1 required
- 3 trains LHSI available; only 1 required
- valves are closed and leak tested prior to reactor startup per TS
- leak-by condition monitored daily per RCS inventory TS requirement 26
Group S113 - HHSI Recirc Isol MOV S1001 1, 12 GQA Rank = High Basis Supports the following system functions:
High risk Cold leg recirculation mode - recirculate borated water from the containment sump, through the RHR heat exchangers, and back to the RCS cold legs Medium risk Support automatic switchover from the injection mode to the cold leg recirculation mode (manual backup available)
Prevent pump damage from insufficient or excessive flow (orifices and mini-flow lines)
GQA ranked High based on:
PRA rank of High Supports High risk functions No credit taken for redundancy RI-IST Treatment = High F-V = 5.2E-3 RAW=3.3 Bases Remain open for HHSI minimum recirculation path Close to isolate flow to RWST during switchover to sump NO, FAI RI-IST treatment
- F-V
- Valve FAI so "open" function is satisfied even if valve fails
- Redundant closing function 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 Rank = High Basis Supports the following system functions:
High risk Cold leg recirculation mode - recirculate borated water from the containment sump, through the RHR heat exchangers, and back to the RCS cold legs Medium risk
- Support automatic switchover from the injection mode to the cold leg recirculation mode (manual backup available)
Prevent pump damage from insufficient or excessive flow (orifices and mini-flow lines)
GQA ranked High based on:
PRA rank of High Supports High risk functions No credit taken for redundancy RI-IST Treatment= High F-V=2.5E-3 RAW= 1.2 Bases Remain open for LHSI minimum recirculation path Close to isolate flow to RWST during switchover to sump NO, FAI RI-IST treatment
- F-V
- Valves FAI so "open" function is satisfied even if valves fail
- Redundant closing function provided by 2 valves in series
- 2 additional LHSI trains provide SI if both valves fail to close 28 11/13/03
Group S121 - LHSI Containment Isol Check Valve GQA Rank = High Bases Supports the following system functions:
High risk Injection mode - deliver borated water from RWST and accumulators to RCS cold legs to make up for loss of coolant resulting from a LOCA, rod ejection accident, or SGTR Cold leg recirculation mode - recirculate borated water from the containment sump, through the RHR heat exchangers, and back to the RCS cold legs Medium risk Hot leg recirculation mode - recirculate borated water from the containment sump simultaneously to the RCS hot legs by one train and to a cold leg by another train GQA ranked High based on:
Initial PRA rank of High, subsequently lowered to Low Supports High risk functions No credit taken for redundancy RI-IST Treatment = Low F-V = 4.8E-4 RAW= 1.2 Bases Close and leaktight for containment isolation; also close to prevent RHR backflow Open to allow LHSI during accident and sump recirculation Open to inject borated water during long-term cooling (hot-leg and cold-leg recirculation)
RI-IST treatment
- F-V and RAW
- 2 additional LHSI trains to provide SI if one valve fails to open 11/13/03 29
Group S125 - Si Suction Check Valve S10002 GQA Rank = High Bases Supports the following system functions:
High risk Injection mode - deliver borated water from RWST and accumulators to RCS cold legs to make up for loss of coolant resulting from a LOCA, rod ejection accident, or SGTR Injection mode - supply borated water to compensate for positive reactivity inserted and make up for shrinkage of reactor coolant from a decrease in temperature caused by secondary steam line break, feedline break, or main steam line depressurization Supports the following Medium risk system function Support the automatic switchover from the injection mode to the cold leg recirculation mode GQA ranked High based on:
Initial PRA rank of High, subsequently lowered to Medium Supports High risk functions No credit taken for redundancy RI-IST Treatment = Low F-V = 3.9E-4 RAW=3.5 Bases Open to allow suction to LHSI, HHSI, CS pumps Close to prevent backflow to RWST during sump recirculation Check valves stop backflow from RWST until Si MOV0001 valves close RI-IST treatment
- F-V and RAW
- Redundant closing function provided by upstream MOV
Group SILHP - LHSI Pump PA102 GQA GQA Rank: High Basis Supports the following system functions:
High risk Injection and Cold leg Recirc modes Medium risk Hot leg recirculation mode Low risk Pressure boundary and positive RCS volume control GQA ranked High based on Initial PRA rank of High, subsequently lowered to Medium*
Supports High.risk functions No credit taken for redundancy RI-IST Treatment = Low F-V=7.8E-4 RAW = 1.2 Basis:
F-V and RAW Active function to 'start and run' to support injection and recirculation functions Redundancy exists with three 100%
safety trains to satisfy the injection modes Diversity exists with 3 High Head pumps to support recirculation and injection 11/13/03 31
Group S106 - LHSI Isolation MOV GQA GQA Rank: Medium RI-IST Treatment = Low Basis Supports the following system functions:
High risk:
Injection and Cold leg recirculation modes Medium risk Hot leg recirculation mode Low risk Pressure boundary and Containment Isolation GQA ranked Medium based on:
Initial PRA rank of Medium, subsequently lowered to Low Redundant Trains Valve is normally open and stays open to support the High risk functions. Transfer closed is not a credible failure 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 F-V=4.3E-4 RAW = 1.2 Bases:
Valve is normally open - satisfies its safety function The 'remain open' function is passive IST testable function is to 'close on demand' RI-IST Treatment of Low based on:
Valve is normally in its required safety position -
no change of state required Redundancy exists with three 100% safety trains to satisfy the injection modes Diversity exists with 3 High Head pumps to support recirculation and injection Valve is routinely monitored by other means to check valve position and flow 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 o n ito rin g Testing Code Inservice Test Code Inservice Test Code Inservice Test Relief Valves.
Performance Test results trending, tighter Test results trending, tighter 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
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 passive.
ssc to be 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
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
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 models of common actuation systems with common cause included at the relay level.
11/13/03 54
Conclusions
- Proposed alternative provides an acceptable level of quality and safety pursuant to 1 OCFR5055a(a) (3) (i) 11/13/03 55