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BRAIDWOOD STATION, UNITS 1 and 2, and BYRON STATION, UNITS 1 and 2 - IMPOSITION OF FACILITY-SPECIFIC BACKFIT RE: COMPLIANCE WITH LICENSING BASIS PLANT DESIGN REQUIREMENTS (TAC NO. MF3206)
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION II 245 PEACHTREE CENTER AVENUE NE, SUITE 1200 ATLANTA, GEORGIA 30303-1257
March 21, 2016
MEMORANDUM TO: Marissa G. Bailey, Acting Director Division of Engineering Office of Nuclear Reactor Regulation
FROM:
SUBJECT: INPUT FOR EXELON BACKFIT REVIEW PANEL
In a memorandum to you dated January 12, 2016, William M. Dean tasked us to provide a recommendation on whether a backfit is necessary at Byron and Braidwood and whether the application of the compliance backfit was appropriate and in accordance with 10 CFR 50.109(a)(4)(i). The Exelon Generation Company’s, LLC (EGC) appeal to the U.S. Nuclear Regulatory Commission (NRC) was dated December 8, 2015. The NRC backfit was imposed in a letter dated October 9, 2015, which stated that the Byron and Braidwood Stations were not in compliance with General Design Criteria (GDC) 15, GDC 21, GDC 29, 10 CFR 50.34(b), and the plant-specific design bases. The backlit documents two primary issues with the licensee’s analyses: (1) failure to evaluate a stuck open Power Operated Relief Valve (PORV), and (2) failure to properly qualify the Pressurizer Safety Valve (PSV) for water relief.
After reviewing the assessment provided by Mr. Gendelman, Office of General Counsel, I concur that the staff implemented the backfit appropriately in accordance with 10 CFR 50.109(a)(4)(i) and NRC Management Directive 8.4. However, my assessment is that the backfit was not implemented appropriately in accordance with NRR Office Instruction LIC-202, Revision 2. Specifically, I suggest that the use of a plant-specific backfit may not be the most appropriate method for addressing the generic nature of the technical issues associated with this event. NRR 01 LIC-202, Section 1 states, ‘a backfit is plant-specific when it involves the imposition of a position that is unique to a particular plant,” in the case of Byron and Braidwood, I believe the issues communicated in the backfit are not unique to these plants.
Following the Three Mile Island accident, the NRC ordered licensees to implement numerous changes to their facilities and operating procedures. Some of these changes were focused on improving the PORV and block valve reliability, supplying Class 1 E power to the PORV and block valve, and to have position indication in the control room. NUREG-1316, “Technical Findings and Regulatory Analysis Related to Generic Issue 70,” concluded that it was not cost effective to upgrade (backfit) existing non-safety-grade PORVs and block valves (and associated control systems) to full safety-grade qualification status when they have been determined to perform any of the safety-related functions discussed in the NUREG or any identified in the future.
CONTACT: Anthony I. Gody, DRS 404 997-4600
M. Bailey 2
In Regulatory Issue Summary 2005-29, Revision 1, the staff reiterated the NRC position that Condition II events are not allowed to progress to Condition Ill or IV events and indicated that PSVs and PORVs (and associated block valves) are not safety-related or qualified for water relief.
Arguably, if these components are relied upon to satisfy a Chapter 15 accident analysis, they are required to be both safety-related and qualified to accomplish the intended safety function (See 10 CER, Part 50, Appendix A, General Design Criteria 1 and 10 CFR, Part 50, Appendix B). In 1993 and 1994, Westinghouse addressed a Nuclear Safety Advisory Letter (NSAL-93013 and NSAL-93-013 Supplement 1)to many pressurized water reactor licensees. In these NSALs, Westinghouse advised licensees that their pressurizer could fill much faster than anticipated during an increase in reactor coolant inventory event and recommended that they employ a strategy that used PORVs and associated block valves in their procedures.
I reviewed 10 UFSARs and developed a brief summary of the various strategies used by licensees in addressing the increased reactor coolant inventory event. The quick review identified a wide range of strategies that were accepted by the NRC. The review identified some interesting facts as follows: two licensees rely solely on the PSVs being capable of opening and reseating due to water temperature above 500 degrees F (no supporting analyses is referenced for this conclusion), four licensees rely on a PORV and its block valve in their strategy but do not appear to address whether PORV/block valve are safety-related and qualified to operate in water blowdown conditions, two licensees directly reference the same Electric Power Research Institute (EPRI) test reports that Byron and Braidwood referenced as part of their mitigation strategy. Furthermore, licensees have implemented procedures to address high pressurizer level or inadvertent actuation of emergency core cooling (ECCS) events that employ the following strategy: assess the event, determining whether the ECCS actuation is appropriate, secure excess injection, re-establishing containment air and letdown, and control either pressurizer level with charging/letdown or reactor pressure with PORVs if solid. At least one licensee successfully avoided having to address the technical issues of the PSV and PORV passing water altogether with the statement that they can terminate a reactor coolant system overfill event before the pressurizer fills solid. One extreme example of this strategy approved by the NRC indicated that emergency core cooling system would be terminated as fast as 14 minutes. Most licensees rely on the PORV and block valve cycling (I think in automatic), preventing the reactor coolant system pressure rising above the PSV set point, while operators assess and terminate the overfill situation. One licensee documents that the PORV would cycle 88 times before injection could be stopped, it appears the PORV is in automatic during this operation.
In conclusion, the staff imposition of a plant-specific backfit to Byron and Braidwood was in accordance with 10 CFR 50.109(a)(4)(i) and NRC Management Directive 8.4. However, my assessment is that the backfit was not implemented appropriately in accordance with NRR Office Instruction LIC-202, Revision 2. Specifically, I suggest that the use of a plant-specific backfit may not be the most appropriate method for addressing the generic nature of the technical issues associated with this event. NRR 01 LIC-202, Section 1 states, “a backfit is plant-specific when it involves the imposition of a position that is unique to a particular plant,” in the case of Byron and Braidwood, I believe the issues communicated in the backfit are not unique to a particular plant. My recommendation is that the staff consider implementing the NRC MD 6.4 process to revisit GSI-70, decide if the issues identified in the Byron and Braidwood backfit are indeed generic, and, if so, initiate actions to issue a generic backfit for this issue and begin an interaction with the nuclear industry using the NRC Principles of Good Regulation.
M. Bailey 3
The transparent use of risk insights in developing strategy and timeline for addressing this issue would be appropriate. NRC and industry should recognize the need to develop a predictable and reliable strategy to address increased reactor coolant inventory events that credits both operator and automatic actions with fully validated procedures; qualified systems, structures, and components; appropriate analyses; and consistent documentation.
cc: Adam S. Gendleman
Enclosure: Increase in reactor coolant system inventory event strategy summary
March 21, 2016
MEMORANDUM TO: Marissa G. Bailey, Acting Director Division of Engineering Office of Nuclear Reactor Regulation
FROM:
SUBJECT: INPUT FOR EXELON BACKFIT REVIEW PANEL
In a memorandum to you dated January 12, 2016, William M. Dean tasked us to provide a recommendation on whether a backfit is necessary at Byron and Braidwood and whether the application of the compliance backfit was appropriate and in accordance with 10 CFR 50.109(a)(4)(i). The Exelon Generation Company’s, LLC (EGC) appeal to the U.S. Nuclear Regulatory Commission (NRC) was dated December 8, 2015. The NRC backfit was imposed in a letter dated October 9, 2015, which stated that the Byron and Braidwood Stations were not in compliance with General Design Criteria (GDC) 15, GDC 21, GDC 29, 10 CFR 50.34(b), and the plant-specific design bases. The backlit documents two primary issues with the licensee’s analyses: (1) failure to evaluate a stuck open Power Operated Relief Valve (PORV), and (2) failure to properly qualify the Pressurizer Safety Valve (PSV) for water relief.
After reviewing the assessment provided by Mr. Gendelman, Office of General Counsel, I concur that the staff implemented the backfit appropriately in accordance with 10 CFR 50.109(a)(4)(i) and NRC Management Directive 8.4. However, my assessment is that the backfit was not implemented appropriately in accordance with NRR Office Instruction LIC-202, Revision 2. Specifically, I suggest that the use of a plant-specific backfit may not be the most appropriate method for addressing the generic nature of the technical issues associated with this event. NRR 01 LIC-202, Section 1 states, ‘a backfit is plant-specific when it involves the imposition of a position that is unique to a particular plant,” in the case of Byron and Braidwood, I believe the issues communicated in the backfit are not unique to these plants.
Following the Three Mile Island accident, the NRC ordered licensees to implement numerous changes to their facilities and operating procedures. Some of these changes were focused on improving the PORV and block valve reliability, supplying Class 1 E power to the PORV and block valve, and to have position indication in the control room. NUREG-1316, “Technical Findings and Regulatory Analysis Related to Generic Issue 70,” concluded that it was not cost effective to upgrade (backfit) existing non-safety-grade PORVs and block valves (and associated control systems) to full safety-grade qualification status when they have been determined to perform any of the safety-related functions discussed in the NUREG or any identified in the future.
CONTACT: Anthony I. Gody, DRS 404 997-4600
M. Bailey 2
In Regulatory Issue Summary 2005-29, Revision 1, the staff reiterated the NRC position that Condition II events are not allowed to progress to Condition Ill or IV events and indicated that PSVs and PORVs (and associated block valves) are not safety-related or qualified for water relief.
Arguably, if these components are relied upon to satisfy a Chapter 15 accident analysis, they are required to be both safety-related and qualified to accomplish the intended safety function (See 10 CER, Part 50, Appendix A, General Design Criteria 1 and 10 CFR, Part 50, Appendix B). In 1993 and 1994, Westinghouse addressed a Nuclear Safety Advisory Letter (NSAL-93013 and NSAL-93-013 Supplement 1)to many pressurized water reactor licensees. In these NSALs, Westinghouse advised licensees that their pressurizer could fill much faster than anticipated during an increase in reactor coolant inventory event and recommended that they employ a strategy that used PORVs and associated block valves in their procedures.
I reviewed 10 UFSARs and developed a brief summary of the various strategies used by licensees in addressing the increased reactor coolant inventory event. The quick review identified a wide range of strategies that were accepted by the NRC. The review identified some interesting facts as follows: two licensees rely solely on the PSVs being capable of opening and reseating due to water temperature above 500 degrees F (no supporting analyses is referenced for this conclusion), four licensees rely on a PORV and its block valve in their strategy but do not appear to address whether PORV/block valve are safety-related and qualified to operate in water blowdown conditions, two licensees directly reference the same Electric Power Research Institute (EPRI) test reports that Byron and Braidwood referenced as part of their mitigation strategy. Furthermore, licensees have implemented procedures to address high pressurizer level or inadvertent actuation of emergency core cooling (ECCS) events that employ the following strategy: assess the event, determining whether the ECCS actuation is appropriate, secure excess injection, re-establishing containment air and letdown, and control either pressurizer level with charging/letdown or reactor pressure with PORVs if solid. At least one licensee successfully avoided having to address the technical issues of the PSV and PORV passing water altogether with the statement that they can terminate a reactor coolant system overfill event before the pressurizer fills solid. One extreme example of this strategy approved by the NRC indicated that emergency core cooling system would be terminated as fast as 14 minutes. Most licensees rely on the PORV and block valve cycling (I think in automatic), preventing the reactor coolant system pressure rising above the PSV set point, while operators assess and terminate the overfill situation. One licensee documents that the PORV would cycle 88 times before injection could be stopped, it appears the PORV is in automatic during this operation.
In conclusion, the staff imposition of a plant-specific backfit to Byron and Braidwood was in accordance with 10 CFR 50.109(a)(4)(i) and NRC Management Directive 8.4. However, my assessment is that the backfit was not implemented appropriately in accordance with NRR Office Instruction LIC-202, Revision 2. Specifically, I suggest that the use of a plant-specific backfit may not be the most appropriate method for addressing the generic nature of the technical issues associated with this event. NRR 01 LIC-202, Section 1 states, “a backfit is plant-specific when it involves the imposition of a position that is unique to a particular plant,” in the case of Byron and Braidwood, I believe the issues communicated in the backfit are not unique to a particular plant. My recommendation is that the staff consider implementing the NRC MD 6.4 process to revisit GSI-70, decide if the issues identified in the Byron and Braidwood backfit are indeed generic, and, if so, initiate actions to issue a generic backfit for this issue and begin an interaction with the nuclear industry using the NRC Principles of Good Regulation.
M. Bailey 3
The transparent use of risk insights in developing strategy and timeline for addressing this issue would be appropriate. NRC and industry should recognize the need to develop a predictable and reliable strategy to address increased reactor coolant inventory events that credits both operator and automatic actions with fully validated procedures; qualified systems, structures, and components; appropriate analyses; and consistent documentation.
cc: Adam S. Gendleman
Enclosure: Increase in reactor coolant system inventory event strategy summary
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