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| {{#Wiki_filter:Exelon BWR Fleet MSSV/SRVTesting Frequency Relief RequestNRC Pre-Application MeetingJune 4, 2019 IntroductionsPurpose and AgendaDavid Neff AttendeesCraig Shinafelt -Fleet Program EngineerExelonPhilip Twaddle -SRV Subject Matter ExpertExelon David Neff -Principal Regulatory EngineerExelon William Reynolds -Engineering ManagerExelon Mark DiRado -Senior Engineering ManagerExelon Thomas Basso -Director EngineeringExelon Bret Collier -Engineering ConsultantRC Engineering 2 | | {{#Wiki_filter:Exelon BWR Fleet MSSV/SRV Testing Frequency Relief Request NRC Pre-Application Meeting June 4, 2019 |
| Brief the NRC on proposed Inservice Testing Relief Requests by covering the following:Extension of test intervals for Group-of-One SRV/MSSVs from 24 months to 48 months, based upon past performance.Extension of test intervals for certain population of OMN-17 SRV/MSSVs to 8 years, based upon past performance.Exelon's Best Practices for SRV/MSSVs Maintenance and Inspections, Testing, and TrendingThe Process used to forecast SRV/MSSV setpoint drift, based upon past performance.Benefits to minimizing dose exposure and maximizing system integrity. Purpose 3 AgendaCurrent Class 1 Relief Valve Frequency Requirements -Craig ShinafeltCurrent Exelon BWR SRV/MSSV Testing Frequency Requirements -Craig ShinafeltBest Practices -Philip TwaddleThe Process -Craig ShinafeltRelief Request Impacts -Craig ShinafeltRelief Request Duration -Craig ShinafeltRelief Request Submittal -David Neff 4
| |
| Current Class 1 Relief Valve Frequency Requirements The testing frequencies for ASME Class 1 Main Steam Safety Valves (MSSV) and Class 1 Safety Relief Valves (SRV) are established in section I-1320 of Appendix I, of the ASME OM Code, which is incorporated by reference in 10CFR50.55a.The ASME OM Code requires every Class 1 SRVs to be tested every 5 years with at least 20% of the valves in each "group" (preferably untested within the previously 5 years), tested every 24 months.
| |
| 5 Current Class 1 Relief Valve Frequency Requirements As an alternative to the ASME OM Code, Mandatory Appendix I requirements, ASME Code Case OMN-17 was developed which allows utilities to extend the Code required 5 year test interval to 6 years, provided the Owner Disassembles and Inspects (D&I) each valve following As-Found testing to verify that parts are free from defects resulting from time-related degradation or service-induced wear.
| |
| 6 Current Exelon SRV/MSSV Testing Frequency ReqmtsThis presentation discusses the testing requirements of the over-pressurization protection devices used at 6 of Exelon's BWR sites. At these 6 BWR sites, which contain 10 individual units, a variety of ASME Class 1 Pressure Relief Devices are utilized to provide over-pressure protection of their Main Steam Piping. The number of Pressure Relief Devices per unit vary as does the manufacture/style of each Pressure Relief Device. All sites requesting relief, except one, utilize Code Case OMN-17 for their current IST 10-year intervals.
| |
| 7 Best Practices Four Pillars of Exelon SRV/MSSVs Best Practices1)Spring Testing -includes physical dimension measurements and compression rate evaluation.2)SRV/MSSVs Lapping Techniques and Tools.3)SRV/MSSVs Set Pressure Adjustment Methodology Precision.4)Target Rock SRV/MSSVs Average Delay Time Trending Performance Improvement.
| |
| 8 Best Practices As-Found Variation Reduced 34%Exelon SRV Best Practices have reduced as-found set point drift and set point variation by 34% over the past 10 years when compared to the 8-year pre-Best Practices period of historical performance at one of our sites.Lapping improvements reduced variation 7%.Springs and set pressure methodology improvements reduced variation by 27%.
| |
| 9 The ProcessHaving seen an increase in the reliability of our valves over the years as a result of Exelon's applied Best Practices, an independent analysis was performed to determine whether valve performance improved to a level that would support an increased test interval.Keeping in mind that, typically, when utilities request the use of OMN-17, they simply include a statement in their Relief Request attesting to how, over the past few refueling outages, few if any SRV have failed to maintain their set pressure within their required tolerances.In this case, Exelon has taken it a step further. . . .
| |
| 10 The ProcessExelon has gone back 5 or more cycles, identified the actual As-Left set pressure as well as the As-Found set pressure, incorporated these values and dates into spreadsheets which not only calculates the valves "drift" but projects, through a simple linear extrapolation, when that valve could fall outside of its set pressure tolerance.The next slide provides one example of a spreadsheet calculation.
| |
| 11 The ProcessBelow is an example of one such calculation for set point drift projections, which shows the drift at -1.0, -5.5 and -8.8 psig for years 1, 5 and 8 respectively based on the measured As-Left, As-Found measured set pressures and time between test. Based upon a +/-3.0% set point tolerance, this valve is not expected to fall outside of tolerance until after 30.9 years.
| |
| 12 The ProcessOnce the spreadsheet has calculated the drifts for each serial numbered valve over the period of interest, the results are condensed into a table, by refueling outage. The Pass/Fail column indicates whether the valve was shown to be able to maintain its set point tolerance for greater than 8 years. In the example above, it shows that based upon the drift calculation, over the past two refueling outages all of the valves would have been able to maintain their set pressure tolerance for more than 8 years.
| |
| 13 The ProcessThis same process was also utilized when considering the proposed Relief Request dealing with valves in a "Group-of-One", specifically those sole Target Rock 3-Stage Safety Relief Valves utilized in two of Exelon's BWR sites. At the first site, calculations have identified that every valve installed since 2012, would have been able to maintain its set pressure tolerance for greater than (4) years.At the second site, calculations have identified that every valve installed since 2011, would have been able to maintain its set pressure tolerance for greater than (4) years. 14 Relief Request Impacts Potential dose savings are calculated based upon individual station historical dose calculations. Saving at a station range from 1.31 rem to 6.5 rem over a 10-year period. In addition to the dose savings, a reduction in the number of valves that are required to be tested during each outage will:
| |
| 15Reduce Industrial Safety Concerns (Fewer heavy lifts)Reduced System Breaches (Fewer FME zones)Reduced number of activities with potential for spreading radioactive contaminationNo impact to PRA risk as a result of increased service time Relief Request Duration Exelon plans to request that these Relief Request be approved for the remaining licensed life of the
| |
|
| |
|
| plant.Saves both time and effort for the Utility and Regulator by removing redundant future reviews and approvals. | | ===Introductions=== |
| 16 Relief Request SubmittalSubmittal to include 5 site specific Relief Requests to extend the testing interval from its current 5/6 year frequency to 8 years.Submittal to include a combined, multi-unit, Relief Request to extend testing interval for Class 1 SRVs in a Group-of-One from the current ASME OM Mandatory Appendix I, 24 month frequency to a 48 month frequency.Submittal are planned for early July 2019. | | Purpose and Agenda David Neff |
| 17 Questions? | | |
| | Attendees Craig Shinafelt - Fleet Program Engineer Exelon Philip Twaddle - SRV Subject Matter Expert Exelon David Neff - Principal Regulatory Engineer Exelon William Reynolds - Engineering Manager Exelon Mark DiRado - Senior Engineering Manager Exelon Thomas Basso - Director Engineering Exelon Bret Collier - Engineering Consultant RC Engineering 2 |
| | |
| | Purpose Brief the NRC on proposed Inservice Testing Relief Requests by covering the following: |
| | * Extension of test intervals for Group-of-One SRV/MSSVs from 24 months to 48 months, based upon past performance. |
| | * Extension of test intervals for certain population of OMN-17 SRV/MSSVs to 8 years, based upon past performance. |
| | * Exelons Best Practices for SRV/MSSVs Maintenance and Inspections, Testing, and Trending |
| | * The Process used to forecast SRV/MSSV setpoint drift, based upon past performance. |
| | * Benefits to minimizing dose exposure and maximizing system integrity. |
| | 3 |
| | |
| | Agenda |
| | * Current Class 1 Relief Valve Frequency Requirements |
| | - Craig Shinafelt |
| | * Current Exelon BWR SRV/MSSV Testing Frequency Requirements - Craig Shinafelt |
| | * Best Practices - Philip Twaddle |
| | * The Process - Craig Shinafelt |
| | * Relief Request Impacts - Craig Shinafelt |
| | * Relief Request Duration - Craig Shinafelt |
| | * Relief Request Submittal - David Neff 4 |
| | |
| | Current Class 1 Relief Valve Frequency Requirements The testing frequencies for ASME Class 1 Main Steam Safety Valves (MSSV) and Class 1 Safety Relief Valves (SRV) are established in section I-1320 of Appendix I, of the ASME OM Code, which is incorporated by reference in 10CFR50.55a. |
| | The ASME OM Code requires every Class 1 SRVs to be tested every 5 years with at least 20% of the valves in each group (preferably untested within the previously 5 years), tested every 24 months. |
| | 5 |
| | |
| | Current Class 1 Relief Valve Frequency Requirements As an alternative to the ASME OM Code, Mandatory Appendix I requirements, ASME Code Case OMN-17 was developed which allows utilities to extend the Code required 5 year test interval to 6 years, provided the Owner Disassembles and Inspects (D&I) each valve following As-Found testing to verify that parts are free from defects resulting from time-related degradation or service-induced wear. |
| | 6 |
| | |
| | Current Exelon SRV/MSSV Testing Frequency Reqmts This presentation discusses the testing requirements of the over-pressurization protection devices used at 6 of Exelons BWR sites. At these 6 BWR sites, which contain 10 individual units, a variety of ASME Class 1 Pressure Relief Devices are utilized to provide over-pressure protection of their Main Steam Piping. The number of Pressure Relief Devices per unit vary as does the manufacture/style of each Pressure Relief Device. |
| | All sites requesting relief, except one, utilize Code Case OMN-17 for their current IST 10-year intervals. |
| | 7 |
| | |
| | Best Practices Four Pillars of Exelon SRV/MSSVs Best Practices |
| | : 1) Spring Testing - includes physical dimension measurements and compression rate evaluation. |
| | : 2) SRV/MSSVs Lapping Techniques and Tools. |
| | : 3) SRV/MSSVs Set Pressure Adjustment Methodology Precision. |
| | : 4) Target Rock SRV/MSSVs Average Delay Time Trending Performance Improvement. |
| | 8 |
| | |
| | Best Practices As-Found Variation Reduced 34% |
| | Exelon SRV Best Practices have reduced as-found set point drift and set point variation by 34% over the past 10 years when compared to the 8-year pre-Best Practices period of historical performance at one of our sites. |
| | * Lapping improvements reduced variation 7%. |
| | * Springs and set pressure methodology improvements reduced variation by 27%. |
| | 9 |
| | |
| | The Process Having seen an increase in the reliability of our valves over the years as a result of Exelons applied Best Practices, an independent analysis was performed to determine whether valve performance improved to a level that would support an increased test interval. |
| | Keeping in mind that, typically, when utilities request the use of OMN-17, they simply include a statement in their Relief Request attesting to how, over the past few refueling outages, few if any SRV have failed to maintain their set pressure within their required tolerances. |
| | In this case, Exelon has taken it a step further. . . . |
| | 10 |
| | |
| | The Process Exelon has gone back 5 or more cycles, identified the actual As-Left set pressure as well as the As-Found set pressure, incorporated these values and dates into spreadsheets which not only calculates the valves drift but projects, through a simple linear extrapolation, when that valve could fall outside of its set pressure tolerance. |
| | The next slide provides one example of a spreadsheet calculation. |
| | 11 |
| | |
| | The Process Below is an example of one such calculation for set point drift projections, which shows the drift at -1.0, -5.5 and -8.8 psig for years 1, 5 and 8 respectively based on the measured As-Left, As-Found measured set pressures and time between test. |
| | Based upon a +/- 3.0% set point tolerance, this valve is not expected to fall outside of tolerance until after 30.9 years. |
| | 12 |
| | |
| | The Process Once the spreadsheet has calculated the drifts for each serial numbered valve over the period of interest, the results are condensed into a table, by refueling outage. |
| | The Pass/Fail column indicates whether the valve was shown to be able to maintain its set point tolerance for greater than 8 years. |
| | In the example above, it shows that based upon the drift calculation, over the past two refueling outages all of the valves would have been able to maintain their set pressure tolerance for more than 8 years. |
| | 13 |
| | |
| | The Process This same process was also utilized when considering the proposed Relief Request dealing with valves in a Group-of-One, specifically those sole Target Rock 3-Stage Safety Relief Valves utilized in two of Exelons BWR sites. |
| | * At the first site, calculations have identified that every valve installed since 2012, would have been able to maintain its set pressure tolerance for greater than (4) years. |
| | * At the second site, calculations have identified that every valve installed since 2011, would have been able to maintain its set pressure tolerance for greater than (4) years. |
| | 14 |
| | |
| | Relief Request Impacts Potential dose savings are calculated based upon individual station historical dose calculations. Saving at a station range from 1.31 rem to 6.5 rem over a 10-year period. |
| | In addition to the dose savings, a reduction in the number of valves that are required to be tested during each outage will: |
| | * Reduce Industrial Safety Concerns (Fewer heavy lifts) |
| | * Reduced System Breaches (Fewer FME zones) |
| | * Reduced number of activities with potential for spreading radioactive contamination |
| | * No impact to PRA risk as a result of increased service time 15 |
| | |
| | Relief Request Duration Exelon plans to request that these Relief Request be approved for the remaining licensed life of the plant. |
| | Saves both time and effort for the Utility and Regulator by removing redundant future reviews and approvals. |
| | 16 |
| | |
| | Relief Request Submittal Submittal to include 5 site specific Relief Requests to extend the testing interval from its current 5/6 year frequency to 8 years. |
| | Submittal to include a combined, multi-unit, Relief Request to extend testing interval for Class 1 SRVs in a Group-of-One from the current ASME OM Mandatory Appendix I, 24 month frequency to a 48 month frequency. |
| | Submittal are planned for early July 2019. |
| | 17 |
| | |
| | Questions? |
| 18}} | | 18}} |
BWR Fleet Mssv/Srv Testing Frequency Relief Request NRC Pre-Application Meeting June 4, 2019| ML19151A660 |
| Person / Time |
|---|
| Site: |
Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Byron, Three Mile Island, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle  |
|---|
| Issue date: |
05/31/2019 |
|---|
| From: |
Blake Purnell
Plant Licensing Branch III |
|---|
| To: |
Bryan Hanson
Exelon Generation Co, Exelon Nuclear |
|---|
| Purnell B |
| References |
|---|
| Download: ML19151A660 (19) |
|
Similar Documents at Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Byron, Three Mile Island, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle |
|---|
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ML24057A3062024-02-24024 February 2024
Attachment 4: BW-SDP-006 Rev. 0 - Braidwood 2B AF Pump Fuel Oil Leak SOP Sensitivities
ML24040A0722024-02-13013 February 2024
– Energy Solution Feb 13 Pubic Meeting Slides on TMI-2 Decommissioning
ML24029A1742024-01-30030 January 2024
Constellation Pre-Application January 30, 2024, Meeting Slides - Proposed Alternative to Utilize Code Case N-932, Alternative Requirements for Acceptance of Containment Base Metal Corrosion or Erosion
ML24057A3042024-01-22022 January 2024
Attachment 2: EC 640630 Rev. 000 - Documentation of Test Results with Diluted Lube Oil from Fuel In-Leakage - 28 AF Diesel Engine Past Operability
ML24003A1812024-01-0808 January 2024
Handout - Byron-Braidwood Core Monitoring and Support System LAR Pre-Submittal Meeting January 8,2024
ML24057A3052023-12-12012 December 2023
Attachment 3: EC 640287 Rev. 000 - Past Operability Test Plan Acceptance Related to 2AF01PB-K
ML23345A0362023-12-11011 December 2023
ATWS Uet December 11, 2023 Pre-submittal Meeting Slides
ML23317A0712023-11-14014 November 2023
NRC Pre-Submittal Meeting on November 14th, 2023 - TSTF-591 and Selected 50.69 License Condition Updates (EPID L-2023-LLM-0098) (Slides)
ML23272A0622023-09-29029 September 2023
Ultimate Heat Sink Temperature Tech Spec Limit Change
ML23262B2602023-09-19019 September 2023
Slides - Constellation - Pre-Application EP 9/25/2023 Meeting Handout
ML23229A0132023-08-17017 August 2023
Relief Request for Alternative Requirements for Byron Unit 1 Reactor Pressure Vessel Inservice Inspection Intervals NRC Meeting Handout
ML23229A4832023-08-17017 August 2023
RR 20-Year ISI Pre-Submittal NRC Meeting Handout
ML23255A1042023-08-11011 August 2023
Slides - Constellation - Pre-Application EP 9/18/2023 Draft CEG Presubmittal SG Performance Monitoring Plan Meeting Handout
ML23170A0082023-06-29029 June 2023
Decommissioning Presentation for NRC Pre-submittal Meeting, June 29, 2023
ML23173A0462023-06-28028 June 2023
DNPS SLR Pre-submittal Meeting Presentation Rev. 1
ML23173A0472023-06-28028 June 2023
SLRA - NRC Presubmittal Meeting Slides - 6-28-23
ML23172A2092023-06-28028 June 2023
LRA - NRC Pre-Submittal Meeting Slides
ML23172A2102023-06-28028 June 2023
CPS Lr Pre-Submittal Meeting Presentation
ML23165A0242023-06-27027 June 2023
June 27, 2023, Dresden Nuclear Power Station Subsequent License Renewal Environmental Pre-application Public Meeting - NRC Slides
ML23145A1322023-06-27027 June 2023
June 27, 2023, Dresden Nuclear Power Station Subsequent License Renewal Environmental Pre-application Public Meeting - Constellation Slides
ML23174A0012023-06-23023 June 2023
Pre-submittal Meeting Slides Regarding Update to the FitzPatrick Fuel Handling Accident Analysis with Impacts to Technical Specifications, June 26, 2023
ML23165A0162023-06-14014 June 2023
June 27, 2023, Clinton Power Station License Renewal Environmental Pre-application Public Meeting - NRC Slides
ML23145A1342023-06-14014 June 2023
June 27, 2023, Clinton Power Station License Renewal Environmental Pre-application Public Meeting - Constellation Slides
ML23163A1642023-06-12012 June 2023
2022 Braidwood/Byron End-of-Cycle Meeting Presentation
ML23157A0352023-06-0606 June 2023
Annual Assessment Meeting for Pa/Md/Ny/Nj Nuclear Power Plants - NRC Presentation Slides
ML23103A4072023-04-13013 April 2023
Presentation Slides for Information Call on 4/13/23 N2E Recirc Discharge Nozzle Weld Repair 2nd Request for Alternative
ML23094A1492023-04-11011 April 2023
Licensee Presentation on Whr Exemption Request for Public Meeting on April 11, 2023
ML23076A0442023-03-16016 March 2023
Pb U2 Scram Barrier Presentation KT Session
ML23055A2712023-03-0202 March 2023
March 2, 2023, Preapplication Meeting to Discuss Planned Amendments to Adopt TSTF-505 and 10 CFR 50.69 (EPID L-2023-LRM-0007) - Slides
ML23053A1562023-02-23023 February 2023
NRC Presentation Slides for Public Meeting on February 23, 2023 - 10 CFR 50.69 Alternate Processes License Amendment Request Preliminary Partial Denial
ML23076A2812023-02-23023 February 2023
Licensee Presentation on Pressure Boundary Process
ML23076A2822023-02-23023 February 2023
Licensee Presentation on Defense-in-Depth Process
ML23033A6662023-02-0909 February 2023
Summary of Public Meeting with Constellation Energy Generation, LLC (Constellation) to Discuss Its Request for Alternatives for Certain Steam Generator Weld Inspections for Calvert Cliffs 1 & 2, Byron 1 & 2, Braidwood 1 & 2, and Ginna
ML23033A6672023-01-30030 January 2023
Public Call with Constellation January 30, 2023 (Slides)
2024-09-24
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Exelon BWR Fleet MSSV/SRV Testing Frequency Relief Request NRC Pre-Application Meeting June 4, 2019
Introductions
Purpose and Agenda David Neff
Attendees Craig Shinafelt - Fleet Program Engineer Exelon Philip Twaddle - SRV Subject Matter Expert Exelon David Neff - Principal Regulatory Engineer Exelon William Reynolds - Engineering Manager Exelon Mark DiRado - Senior Engineering Manager Exelon Thomas Basso - Director Engineering Exelon Bret Collier - Engineering Consultant RC Engineering 2
Purpose Brief the NRC on proposed Inservice Testing Relief Requests by covering the following:
- Extension of test intervals for Group-of-One SRV/MSSVs from 24 months to 48 months, based upon past performance.
- Extension of test intervals for certain population of OMN-17 SRV/MSSVs to 8 years, based upon past performance.
- Exelons Best Practices for SRV/MSSVs Maintenance and Inspections, Testing, and Trending
- The Process used to forecast SRV/MSSV setpoint drift, based upon past performance.
- Benefits to minimizing dose exposure and maximizing system integrity.
3
Agenda
- Current Class 1 Relief Valve Frequency Requirements
- Craig Shinafelt
- Current Exelon BWR SRV/MSSV Testing Frequency Requirements - Craig Shinafelt
- Best Practices - Philip Twaddle
- The Process - Craig Shinafelt
- Relief Request Impacts - Craig Shinafelt
- Relief Request Duration - Craig Shinafelt
- Relief Request Submittal - David Neff 4
Current Class 1 Relief Valve Frequency Requirements The testing frequencies for ASME Class 1 Main Steam Safety Valves (MSSV) and Class 1 Safety Relief Valves (SRV) are established in section I-1320 of Appendix I, of the ASME OM Code, which is incorporated by reference in 10CFR50.55a.
The ASME OM Code requires every Class 1 SRVs to be tested every 5 years with at least 20% of the valves in each group (preferably untested within the previously 5 years), tested every 24 months.
5
Current Class 1 Relief Valve Frequency Requirements As an alternative to the ASME OM Code, Mandatory Appendix I requirements, ASME Code Case OMN-17 was developed which allows utilities to extend the Code required 5 year test interval to 6 years, provided the Owner Disassembles and Inspects (D&I) each valve following As-Found testing to verify that parts are free from defects resulting from time-related degradation or service-induced wear.
6
Current Exelon SRV/MSSV Testing Frequency Reqmts This presentation discusses the testing requirements of the over-pressurization protection devices used at 6 of Exelons BWR sites. At these 6 BWR sites, which contain 10 individual units, a variety of ASME Class 1 Pressure Relief Devices are utilized to provide over-pressure protection of their Main Steam Piping. The number of Pressure Relief Devices per unit vary as does the manufacture/style of each Pressure Relief Device.
All sites requesting relief, except one, utilize Code Case OMN-17 for their current IST 10-year intervals.
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Best Practices Four Pillars of Exelon SRV/MSSVs Best Practices
- 1) Spring Testing - includes physical dimension measurements and compression rate evaluation.
- 2) SRV/MSSVs Lapping Techniques and Tools.
- 3) SRV/MSSVs Set Pressure Adjustment Methodology Precision.
- 4) Target Rock SRV/MSSVs Average Delay Time Trending Performance Improvement.
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Best Practices As-Found Variation Reduced 34%
Exelon SRV Best Practices have reduced as-found set point drift and set point variation by 34% over the past 10 years when compared to the 8-year pre-Best Practices period of historical performance at one of our sites.
- Lapping improvements reduced variation 7%.
- Springs and set pressure methodology improvements reduced variation by 27%.
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The Process Having seen an increase in the reliability of our valves over the years as a result of Exelons applied Best Practices, an independent analysis was performed to determine whether valve performance improved to a level that would support an increased test interval.
Keeping in mind that, typically, when utilities request the use of OMN-17, they simply include a statement in their Relief Request attesting to how, over the past few refueling outages, few if any SRV have failed to maintain their set pressure within their required tolerances.
In this case, Exelon has taken it a step further. . . .
10
The Process Exelon has gone back 5 or more cycles, identified the actual As-Left set pressure as well as the As-Found set pressure, incorporated these values and dates into spreadsheets which not only calculates the valves drift but projects, through a simple linear extrapolation, when that valve could fall outside of its set pressure tolerance.
The next slide provides one example of a spreadsheet calculation.
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The Process Below is an example of one such calculation for set point drift projections, which shows the drift at -1.0, -5.5 and -8.8 psig for years 1, 5 and 8 respectively based on the measured As-Left, As-Found measured set pressures and time between test.
Based upon a +/- 3.0% set point tolerance, this valve is not expected to fall outside of tolerance until after 30.9 years.
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The Process Once the spreadsheet has calculated the drifts for each serial numbered valve over the period of interest, the results are condensed into a table, by refueling outage.
The Pass/Fail column indicates whether the valve was shown to be able to maintain its set point tolerance for greater than 8 years.
In the example above, it shows that based upon the drift calculation, over the past two refueling outages all of the valves would have been able to maintain their set pressure tolerance for more than 8 years.
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The Process This same process was also utilized when considering the proposed Relief Request dealing with valves in a Group-of-One, specifically those sole Target Rock 3-Stage Safety Relief Valves utilized in two of Exelons BWR sites.
- At the first site, calculations have identified that every valve installed since 2012, would have been able to maintain its set pressure tolerance for greater than (4) years.
- At the second site, calculations have identified that every valve installed since 2011, would have been able to maintain its set pressure tolerance for greater than (4) years.
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Relief Request Impacts Potential dose savings are calculated based upon individual station historical dose calculations. Saving at a station range from 1.31 rem to 6.5 rem over a 10-year period.
In addition to the dose savings, a reduction in the number of valves that are required to be tested during each outage will:
- Reduce Industrial Safety Concerns (Fewer heavy lifts)
- Reduced System Breaches (Fewer FME zones)
- Reduced number of activities with potential for spreading radioactive contamination
- No impact to PRA risk as a result of increased service time 15
Relief Request Duration Exelon plans to request that these Relief Request be approved for the remaining licensed life of the plant.
Saves both time and effort for the Utility and Regulator by removing redundant future reviews and approvals.
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Relief Request Submittal Submittal to include 5 site specific Relief Requests to extend the testing interval from its current 5/6 year frequency to 8 years.
Submittal to include a combined, multi-unit, Relief Request to extend testing interval for Class 1 SRVs in a Group-of-One from the current ASME OM Mandatory Appendix I, 24 month frequency to a 48 month frequency.
Submittal are planned for early July 2019.
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Questions?
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