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{{#Wiki_filter:DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONQuestionRAI 3.6.2.2.2-1a (High Voltage Insulators)LRA 3.6.2.2.2 Degradation of Insulator Quality due to Presence of Any Salt Deposits and SurfaceContamination, and Loss of Material due to Mechanical WearRegulatory BasisSection 54.21(a)(1) of 10 CFR requires the applicant to identify and list those structures and componentssubject to an aging management review. Section 54.21(a)(3) of 10 CFR requires the applicant to demonstratethat the effects of aging for structures and components within the scope of license renewal and subject to anAMR pursuant to 10 CFR 54.21(a)(1) will be adequately managed so that the intended function(s) will bemaintained consistent with the current licensing basis for the period of extended operation. As described inSRP-LR, an applicant may demonstrate compliance with 10 CFR 54.21(a)(3) by referencing the GALL Reportwhen evaluation of the matter in the GALL Report applies to the plant.Section 3.6.2.2.2 of SRP-LR, "Reduced Insulation Resistance due to Presence of Any Salt Deposits andSurface Contamination, and Loss of Material due to Mechanical Wear Caused by Wind Blowing onTransmission Conductors" states that: "Loss of material due to mechanical wear caused by wind blowing ontransmission conductors could occur in high-voltage insulators. The GALL Report recommends furtherevaluation of a plant-specific AMP to ensure that this aging effect is adequately managed." The GALL reportalso recommends further evaluation of plant-specific AMP for potential salt deposits and surfacecontamination.BackgroundIn LRA 3.6.2.2.2, the applicant references SRP-LR for further evaluation of the above aging mechanisms andeffects for high-voltage insulators. Table 3.6.1, line item numbers 3.6.1-2 and 3.6.1-3 identify the componentas: "High voltage insulators composed of porcelain, malleable iron, aluminum, galvanized steel and cement."The corresponding items in Table 3.6.2 of the LRA identify the materials as: "Porcelain, galvanized metal andcement."During the onsite audit /walkdown, the staff noted that in-scope high-voltage insulators on the 230 kVtransmission lines are constructed of polymer material rather than the porcelain material listed in LRA Table3.6.1 and Table 3.6.2. The applicant stated that the porcelain insulators had been replaced with new insulatorsmade of polymeric material in 2008. The actual material (polymer) used in construction of the polymer in-scope high-voltage insulators are not identified in the applicant's LRA.Staff issued RAI 3.6.2.2.2-1 to obtain clarification on why the LRA did not address the replacementcomponents and aging effects related to polymer high-voltage insulators. The RAI and the applicant'sresponse are documented in ADAMS Accession No. ML 18051A531, dated February 20, 2018. In itsresponse, the applicant provided update to LRA section 3.6.2.1 as well as adding a new line item to AMR table3.6.2 for polymer high-voltage insulators. The applicant also provided further evaluation discussions inresponse to RAI 2.6.2.2.2-1 for these components and concluded that there are no aging effects requiringmanagement and did not propose a site-specific aging management program.The staff's review of the RAI response as well as industry literature, vendor documents, RBS procedures andwork orders identified some material used in the construction of the polymer high-voltage insulators that werenot listed in the applicant's changes to the LRA. Specifically, according to vendor and EPRI literature providedby the applicant, the missing material include: epoxy, silicone gel, sealants, and ductile iron.The staff's review of the RAI response and relevant technical information provided by the applicant further DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONidentified pertinent aging effects and mechanisms not addressed in the applicant's response. These include:Stress corrosion cracking of glass fibersSwelling of silicone rubber (SIR) layer due to chemical contaminationSheath wetting caused by chemicals absorbed by oil from SIR compoundBrittle fracture of rods resulting from discharge activity, flashunder, and flashoverChalking and crazing of insulator surfaces resulting in contamination, arcing, and flashoverBonding failure at rod and sheathing interfaceWater ingress through end fittings causing flashunder, corrosion and fracture of glass fibersThe staff also noted that rodent and bird excrement containing aggressive chemicals such as phosphates, uricacid, and ammonia create an environment that can cause sheath layer damage and subsequent failures of thecore material and fittings. Susceptibility of these components to this environment, which has not beenreviewed in GALL needs to be addressed.According to research results, aging studies and handbook material provided by the applicant, polymerinsulators have been shown to have unique failure modes with little advance indications. This information alsoindicates that contamination can be worse for SIR (compared to porcelain insulators) due to absorption bysilicone oil, especially in late stages of service life.The staff and representatives of the applicant held a public telephone conference call on April 18, 2018, todiscuss the applicant's responses to RAI 3.6.2.2.2.2-1 and issues outlined below. | {{#Wiki_filter:DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONQuestionRAI 3.6.2.2.2-1a (High Voltage Insulators)LRA 3.6.2.2.2 Degradation of Insulator Quality due to Presence of Any Salt Deposits and SurfaceContamination, and Loss of Material due to Mechanical WearRegulatory BasisSection 54.21(a)(1) of 10 CFR requires the applicant to identify and list those structures and componentssubject to an aging management review. Section 54.21(a)(3) of 10 CFR requires the applicant to demonstratethat the effects of aging for structures and components within the scope of license renewal and subject to anAMR pursuant to 10 CFR 54.21(a)(1) will be adequately managed so that the intended function(s) will bemaintained consistent with the current licensing basis for the period of extended operation. As described inSRP-LR, an applicant may demonstrate compliance with 10 CFR 54.21(a)(3) by referencing the GALL Reportwhen evaluation of the matter in the GALL Report applies to the plant.Section 3.6.2.2.2 of SRP-LR, "Reduced Insulation Resistance due to Presence of Any Salt Deposits andSurface Contamination, and Loss of Material due to Mechanical Wear Caused by Wind Blowing onTransmission Conductors" states that: "Loss of material due to mechanical wear caused by wind blowing ontransmission conductors could occur in high-voltage insulators. The GALL Report recommends furtherevaluation of a plant-specific AMP to ensure that this aging effect is adequately managed." The GALL reportalso recommends further evaluation of plant-specific AMP for potential salt deposits and surfacecontamination.BackgroundIn LRA 3.6.2.2.2, the applicant references SRP-LR for further evaluation of the above aging mechanisms andeffects for high-voltage insulators. Table 3.6.1, line item numbers 3.6.1-2 and 3.6.1-3 identify the componentas: "High voltage insulators composed of porcelain, malleable iron, aluminum, galvanized steel and cement."The corresponding items in Table 3.6.2 of the LRA identify the materials as: "Porcelain, galvanized metal andcement."During the onsite audit /walkdown, the staff noted that in-scope high-voltage insulators on the 230 kVtransmission lines are constructed of polymer material rather than the porcelain material listed in LRA Table3.6.1 and Table 3.6.2. The applicant stated that the porcelain insulators had been replaced with new insulatorsmade of polymeric material in 2008. The actual material (polymer) used in construction of the polymer in-scope high-voltage insulators are not identified in the applicant's LRA.Staff issued RAI 3.6.2.2.2-1 to obtain clarification on why the LRA did not address the replacementcomponents and aging effects related to polymer high-voltage insulators. The RAI and the applicant'sresponse are documented in ADAMS Accession No. ML 18051A531, dated February 20, 2018. In itsresponse, the applicant provided update to LRA section 3.6.2.1 as well as adding a new line item to AMR table3.6.2 for polymer high-voltage insulators. The applicant also provided further evaluation discussions inresponse to RAI 2.6.2.2.2-1 for these components and concluded that there are no aging effects requiringmanagement and did not propose a site-specific aging management program.The staff's review of the RAI response as well as industry literature, vendor documents, RBS procedures andwork orders identified some material used in the construction of the polymer high-voltage insulators that werenot listed in the applicant's changes to the LRA. Specifically, according to vendor and EPRI literature providedby the applicant, the missing material include: epoxy, silicone gel, sealants, and ductile iron.The staff's review of the RAI response and relevant technical information provided by the applicant further DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONidentified pertinent aging effects and mechanisms not addressed in the applicant's response. These include:Stress corrosion cracking of glass fibersSwelling of silicone rubber (SIR) layer due to chemical contaminationSheath wetting caused by chemicals absorbed by oil from SIR compoundBrittle fracture of rods resulting from discharge activity, flashunder, and flashoverChalking and crazing of insulator surfaces resulting in contamination, arcing, and flashoverBonding failure at rod and sheathing interfaceWater ingress through end fittings causing flashunder, corrosion and fracture of glass fibersThe staff also noted that rodent and bird excrement containing aggressive chemicals such as phosphates, uricacid, and ammonia create an environment that can cause sheath layer damage and subsequent failures of thecore material and fittings. Susceptibility of these components to this environment, which has not beenreviewed in GALL needs to be addressed.According to research results, aging studies and handbook material provided by the applicant, polymerinsulators have been shown to have unique failure modes with little advance indications. This information alsoindicates that contamination can be worse for SIR (compared to porcelain insulators) due to absorption bysilicone oil, especially in late stages of service life.The staff and representatives of the applicant held a public telephone conference call on April 18, 2018, todiscuss the applicant's responses to RAI 3.6.2.2.2.2-1 and issues outlined below.Issues 1.The material listed in the applicant's response to RAI 3.6.2.2.2-1 seems to have omitted certainmaterial that are used in construction of the polymer insulators. According to vendor and EPRIliterature, these include: epoxy, silicone gel, sealants, and ductile iron. | ||
2.The aging effects and mechanisms addressed in the applicant's response to RAI 3.6.2.2.2-1 seem tohave addressed some, but not all relevant aging effects requiring management (AERM). The AERMsnot considered in the response include the following: | 2.The aging effects and mechanisms addressed in the applicant's response to RAI 3.6.2.2.2-1 seem tohave addressed some, but not all relevant aging effects requiring management (AERM). The AERMsnot considered in the response include the following: | ||
a.Stress corrosion cracking (SCC) of glass fibers due to sheath degradation b.Swelling of SIR layer due to chemical contamination c.Sheath wetting caused by chemicals absorbed by oil from SIR compound d.Brittle fracture of rods resulting from discharge activity, flashunder, and flashover e.Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover f.Water penetration through the sheath followed by electrical failure g.Bonding failure at rod and sheathing interface h.Water ingress through end fittings causing flashunder, corrosion and fracture of glass fibers 3.Additionally, aggressive environment due to excrements from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers is notaddressed in the applicant's response to RAI 3.6.2.2.2-1. This environment and material combinationhas not previously been evaluated in the GALL Report and constitutes a condition that should beassessed for RBS. | a.Stress corrosion cracking (SCC) of glass fibers due to sheath degradation b.Swelling of SIR layer due to chemical contamination c.Sheath wetting caused by chemicals absorbed by oil from SIR compound d.Brittle fracture of rods resulting from discharge activity, flashunder, and flashover e.Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover f.Water penetration through the sheath followed by electrical failure g.Bonding failure at rod and sheathing interface h.Water ingress through end fittings causing flashunder, corrosion and fracture of glass fibers 3.Additionally, aggressive environment due to excrements from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers is notaddressed in the applicant's response to RAI 3.6.2.2.2-1. This environment and material combinationhas not previously been evaluated in the GALL Report and constitutes a condition that should beassessed for RBS. | ||
4.The applicant concluded, in its response to RAI 3.6.2.2.2-1, that an aging management program willnot be implemented for polymer high-voltage insulators. The staff noted that polymer insulators haveshown to have unique failure modes with little advance indications. Furthermore, contaminationbuildup can be worse for SIR (compared to porcelain insulators) due to absorption by silicone oil,especially in late stages of service life. It appears that the applicant's conclusion is based on the DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONassumption that polymer insulators are more reliable than porcelain and less likely to be affected byaging degradation, primarily due to the hydrophobic characteristics of the polymers and reducedpossibility of chemicals and particulate matter buildup on the surfaces of the insulators. The staffnotes that the licensee's response does not include consideration of new and unique degradationmechanisms and sensitivity to the environment, especially during later stages of service life, typicallypast the twenty-year period. It is not clear to the staff whether the applicant's conclusion considers allaspects of polymer insulators' degradation and aging that can result in aging effects such as reducedinsulation resistance and loss of material which may require aging management. | 4.The applicant concluded, in its response to RAI 3.6.2.2.2-1, that an aging management program willnot be implemented for polymer high-voltage insulators. The staff noted that polymer insulators haveshown to have unique failure modes with little advance indications. Furthermore, contaminationbuildup can be worse for SIR (compared to porcelain insulators) due to absorption by silicone oil,especially in late stages of service life. It appears that the applicant's conclusion is based on the DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONassumption that polymer insulators are more reliable than porcelain and less likely to be affected byaging degradation, primarily due to the hydrophobic characteristics of the polymers and reducedpossibility of chemicals and particulate matter buildup on the surfaces of the insulators. The staffnotes that the licensee's response does not include consideration of new and unique degradationmechanisms and sensitivity to the environment, especially during later stages of service life, typicallypast the twenty-year period. It is not clear to the staff whether the applicant's conclusion considers allaspects of polymer insulators' degradation and aging that can result in aging effects such as reducedinsulation resistance and loss of material which may require aging management.Request 1.Explain why epoxy, silicone gel, sealants, and ductile iron are not listed in the response to RAI3.6.2.2.2-1 as materials that are used in construction of polymer high-voltage insulators. | ||
2.Explain why certain aging effects and mechanisms that have been identified for polymer high-voltageinsulators, by industry as a result of operating experience reviews and aging study research, have notbeen considered in response to RAI 3.6.2.2.2-1. These aging effects and mechanisms are listed aboveunder the heading "Issues," items 2 (a) through (h). | 2.Explain why certain aging effects and mechanisms that have been identified for polymer high-voltageinsulators, by industry as a result of operating experience reviews and aging study research, have notbeen considered in response to RAI 3.6.2.2.2-1. These aging effects and mechanisms are listed aboveunder the heading "Issues," items 2 (a) through (h). | ||
3.Explain why aggressive environment due to excrement from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers has not beenaddressed in the response to RAI 3.6.2.2.2-1. This environment and material combination has notpreviously been evaluated in the GALL Report and constitutes a site-specific condition to be assessedfor RBS.4.Considering polymer insulators' degradation, aging, and failure mechanisms that may require agingmanagement, provide a discussion of any site-specific aging management program needed to ensurethat the aging effects such as reduced insulation resistance and loss of material for these componentscomposed of polymers, epoxy, silicone gel, sealants, and ductile iron will be adequately managed.Describe what parameters will be monitored or inspected to detect the AERM and how the frequency ofinspection will be established. If no program will be used, justify why loss of material, reducedinsulation resistance, presence of deposits, rod fiber glass degradation, SCC of fiber glass material,wetting and swelling of SIR, accelerated aging of polymer material due to discharge current activity andcorona, chalking and crazing of surfaces, tracking, corona, loosening of sheath layers, bonding failureat rod/sheath interface, separation of seals and sealants, water ingress through end fittings, andsurface contamination are not applicable for the polymer high-voltage insulators exposed to air-outdoorand chemicals such as uric acid, phosphates and ammonia from birds and rodents.ResponsePart 1Information from the manufacturer (MacLean Power Systems or MPS) of the RBS polymer insulators does notdiscuss "ductile iron" for the corona ring or the end fittings, which are the only metal components on theinsulators. The connection hardware does include ductile iron.The response to RAI 3.6.2.2.2-1 stated, "The RBS polymer high-voltage insulators and connection hardwarehave the following materials: fiberglass, silicone rubber, aluminum and aluminum alloy, steel and steel alloys, DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONgalvanized metal (galvanized ductile iron, galvanized forged steel, steel hot dip galvanized)." Therefore,galvanized ductile iron is explicitly identified.The RBS polymer high-voltage insulators are a recent generation of MPS polymer insulators that have beenmanufactured since 2007. The RBS polymer insulators do not use epoxy. The following figure shows thedifference between the first generation of MPS polymer insulators and the generation of MPS polymerinsulators that are used at RBS.The MPS polymer insulators in service at RBS use a PST sealing system, which is a triple seal design. Thetriple seal or PST seal comprises the primary seal (P), the secondary seal (S), and the tertiary seal (T). Theprimary seal is a silicone rubber sheath compressed into the chamfer of the crimped end fitting. The secondaryseal is RTV (room temperature vulcanizing) silicone applied to the rod, sheath, and end fitting interface. Thetertiary seal is a final external RTV silicone seal applied to the sheath and end fitting interface. The RBSpolymer insulators do not utilize silicone gel. The response to RAI 3.6.2.2.2-1 included silicone rubber, but didnot explicitly identify RTV silicone as a type of silicone rubber. The silicone rubber material includes the RTVsilicone that is part of the PST seal system. The RBS polymer insulators do not includesilicone gel or sealantsother than RTV silicone.Part 2The aging effects on polymer high-voltage insulators are the same as the aging effects on porcelain high-voltage insulators. Those aging effects are reduced insulation resistance and loss of material. Polymerdegradation is an additional mechanism unique to polymer high-voltage insulators that can cause the agingeffect of reduced insulation resistance.The items identified in part 2 of the issue as Items a) through h) are discussed in the following sections. Each DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONdiscussion describes how the item was considered in the aging management review of RBS polymer high-voltage insulators. The functions of high-voltage insulators are to insulate and support a high-voltageconductor. The failure of one high-voltage insulator does not cause the loss of the function of the high-voltageinsulator system to insulate and support a high-voltage conductor.a) Rod failures of early generation polymer insulators have been linked to stress corrosion cracking (SCC)resulting from infiltration of water into the fiberglass/glass reinforced plastic(GRP)rod. The failureshave been attributed to either acid or water leaching of the metallic ions in the glass fibers resulting instress corrosion cracking. SCC in an E-glass polymer composite results from the combined effect oflow mechanical tensile stresses applied along the fibers and chemical attack of either organic orinorganic acids. Known in the industry as brittle fracture this failure of the polymer insulator rods isgenerally associated with high-voltage applications in which nitric acid or other acids can be present. Inorder to avoid such failures, water is prevented from migrating into the end fittings of polymerinsulators. In-service failures have been observed when nitric acid forms and reaches the rod surface.The polymer high-voltage insulators installed on the 230 kV offsite power recovery paths for RBS arespecifically manufactured to eliminate the conditions that can cause brittle fracture of the polymerinsulator support rod. For these insulators, the fiberglass rod is a boron-free corrosion-resistant (CR) E-Glass, which is resistant to nitric acid attacks. There has never been a brittle facture failure of a MPSCR E-glassrod in an MPS polymerinsulator in over 30 years of use. Review of industry literatureapplicable to RBS polymer high-voltage insulators did not identify any aging effects requiringmanagement related to brittle fracture of the glass support rods.b) Swelling of SIR layer due to chemical contamination is not identified in industry documents as a causeof loss of function in high-voltage polymer insulators. One industry document, published in October2003, discusses that solvents can swell polymers, and that some polymer characterization tests arebased upon the degree of swelling of the unknown polymer in different solvents; the swelling ratios canfingerprint the polymer. The other discussion of swelling in this document is that studies could beperformed to determine chemical environments (unique chemicals or cocktails) that would theoreticallyassess the potential for swelling or other degradation that could change the water permeability orhydrophobic properties of the water shed polymer. No studies were found for using solvents to createpotential problems for silicone rubber polymers. Also, solvents are not found in the air environment ofhigh-voltage insulators at RBS. Review of industry literature for the type of polymer insulator used atRBS did not identify any aging effects requiring management related to swelling of silicone rubberinsulator components due to chemical contamination for polymer high-voltage insulators.c) Sheath wetting caused by chemicals absorbed by oil from SIR compound was not found as a failurecause for polymer insulators. Discussions of sheath wetting were not identified for polymer insulators.There are industry documents that contain statements from an old reference citing that silicone rubberinsulators, due to the presence of the silicone oils, collect more contaminants than glass or ceramicsurfaces. Later industry documents refuted this old reference, by stating that silicone rubber (SR) isnaturally hydrophobic, has excellent resistance to UV, and minimizes leakage currents on the surfaceof the insulator, all of which help polymer insulators perform well in contaminated environments. Thisposition was discussed in greater detail in the response to RAI 3.6.2.2.2-1. Review of industry literaturefor the type of polymer insulator used at RBS did not identify any aging effects requiring managementrelated to sheath wetting caused by chemical absorption for polymer high-voltage insulators.d) Failure of rods resulting from discharge activity, flashunder, and flashover is not called brittle facture inindustry documents. Brittle fracture due to stress corrosion cracking is discussed in item 2(a) above. | 3.Explain why aggressive environment due to excrement from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers has not beenaddressed in the response to RAI 3.6.2.2.2-1. This environment and material combination has notpreviously been evaluated in the GALL Report and constitutes a site-specific condition to be assessedfor RBS.4.Considering polymer insulators' degradation, aging, and failure mechanisms that may require agingmanagement, provide a discussion of any site-specific aging management program needed to ensurethat the aging effects such as reduced insulation resistance and loss of material for these componentscomposed of polymers, epoxy, silicone gel, sealants, and ductile iron will be adequately managed.Describe what parameters will be monitored or inspected to detect the AERM and how the frequency ofinspection will be established. If no program will be used, justify why loss of material, reducedinsulation resistance, presence of deposits, rod fiber glass degradation, SCC of fiber glass material,wetting and swelling of SIR, accelerated aging of polymer material due to discharge current activity andcorona, chalking and crazing of surfaces, tracking, corona, loosening of sheath layers, bonding failureat rod/sheath interface, separation of seals and sealants, water ingress through end fittings, andsurface contamination are not applicable for the polymer high-voltage insulators exposed to air-outdoorand chemicals such as uric acid, phosphates and ammonia from birds and rodents.ResponsePart 1Information from the manufacturer (MacLean Power Systems or MPS) of the RBS polymer insulators does notdiscuss "ductile iron" for the corona ring or the end fittings, which are the only metal components on theinsulators. The connection hardware does include ductile iron.The response to RAI 3.6.2.2.2-1 stated, "The RBS polymer high-voltage insulators and connection hardwarehave the following materials: fiberglass, silicone rubber, aluminum and aluminum alloy, steel and steel alloys, DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONgalvanized metal (galvanized ductile iron, galvanized forged steel, steel hot dip galvanized)." Therefore,galvanized ductile iron is explicitly identified.The RBS polymer high-voltage insulators are a recent generation of MPS polymer insulators that have beenmanufactured since 2007. The RBS polymer insulators do not use epoxy. The following figure shows thedifference between the first generation of MPS polymer insulators and the generation of MPS polymerinsulators that are used at RBS.The MPS polymer insulators in service at RBS use a PST sealing system, which is a triple seal design. Thetriple seal or PST seal comprises the primary seal (P), the secondary seal (S), and the tertiary seal (T). Theprimary seal is a silicone rubber sheath compressed into the chamfer of the crimped end fitting. The secondaryseal is RTV (room temperature vulcanizing) silicone applied to the rod, sheath, and end fitting interface. Thetertiary seal is a final external RTV silicone seal applied to the sheath and end fitting interface. The RBSpolymer insulators do not utilize silicone gel. The response to RAI 3.6.2.2.2-1 included silicone rubber, but didnot explicitly identify RTV silicone as a type of silicone rubber. The silicone rubber material includes the RTVsilicone that is part of the PST seal system. The RBS polymer insulators do not includesilicone gel or sealantsother than RTV silicone.Part 2The aging effects on polymer high-voltage insulators are the same as the aging effects on porcelain high-voltage insulators. Those aging effects are reduced insulation resistance and loss of material. Polymerdegradation is an additional mechanism unique to polymer high-voltage insulators that can cause the agingeffect of reduced insulation resistance.The items identified in part 2 of the issue as Items a) through h) are discussed in the following sections. Each DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONdiscussion describes how the item was considered in the aging management review of RBS polymer high-voltage insulators. The functions of high-voltage insulators are to insulate and support a high-voltageconductor. The failure of one high-voltage insulator does not cause the loss of the function of the high-voltageinsulator system to insulate and support a high-voltage conductor.a) Rod failures of early generation polymer insulators have been linked to stress corrosion cracking (SCC)resulting from infiltration of water into the fiberglass/glass reinforced plastic(GRP)rod. The failureshave been attributed to either acid or water leaching of the metallic ions in the glass fibers resulting instress corrosion cracking. SCC in an E-glass polymer composite results from the combined effect oflow mechanical tensile stresses applied along the fibers and chemical attack of either organic orinorganic acids. Known in the industry as brittle fracture this failure of the polymer insulator rods isgenerally associated with high-voltage applications in which nitric acid or other acids can be present. Inorder to avoid such failures, water is prevented from migrating into the end fittings of polymerinsulators. In-service failures have been observed when nitric acid forms and reaches the rod surface.The polymer high-voltage insulators installed on the 230 kV offsite power recovery paths for RBS arespecifically manufactured to eliminate the conditions that can cause brittle fracture of the polymerinsulator support rod. For these insulators, the fiberglass rod is a boron-free corrosion-resistant (CR) E-Glass, which is resistant to nitric acid attacks. There has never been a brittle facture failure of a MPSCR E-glassrod in an MPS polymerinsulator in over 30 years of use. Review of industry literatureapplicable to RBS polymer high-voltage insulators did not identify any aging effects requiringmanagement related to brittle fracture of the glass support rods.b) Swelling of SIR layer due to chemical contamination is not identified in industry documents as a causeof loss of function in high-voltage polymer insulators. One industry document, published in October2003, discusses that solvents can swell polymers, and that some polymer characterization tests arebased upon the degree of swelling of the unknown polymer in different solvents; the swelling ratios canfingerprint the polymer. The other discussion of swelling in this document is that studies could beperformed to determine chemical environments (unique chemicals or cocktails) that would theoreticallyassess the potential for swelling or other degradation that could change the water permeability orhydrophobic properties of the water shed polymer. No studies were found for using solvents to createpotential problems for silicone rubber polymers. Also, solvents are not found in the air environment ofhigh-voltage insulators at RBS. Review of industry literature for the type of polymer insulator used atRBS did not identify any aging effects requiring management related to swelling of silicone rubberinsulator components due to chemical contamination for polymer high-voltage insulators.c) Sheath wetting caused by chemicals absorbed by oil from SIR compound was not found as a failurecause for polymer insulators. Discussions of sheath wetting were not identified for polymer insulators.There are industry documents that contain statements from an old reference citing that silicone rubberinsulators, due to the presence of the silicone oils, collect more contaminants than glass or ceramicsurfaces. Later industry documents refuted this old reference, by stating that silicone rubber (SR) isnaturally hydrophobic, has excellent resistance to UV, and minimizes leakage currents on the surfaceof the insulator, all of which help polymer insulators perform well in contaminated environments. Thisposition was discussed in greater detail in the response to RAI 3.6.2.2.2-1. Review of industry literaturefor the type of polymer insulator used at RBS did not identify any aging effects requiring managementrelated to sheath wetting caused by chemical absorption for polymer high-voltage insulators.d) Failure of rods resulting from discharge activity, flashunder, and flashover is not called brittle facture inindustry documents. Brittle fracture due to stress corrosion cracking is discussed in item 2(a) above. | ||
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONFlashover occurs external to the sheath covering the rod; therefore, flashover is not applicable to failureof the rod by discharge activity. Flashunder is initiated by tracking along or through the rod under thesilicone rubber sheath and occurs when internal discharge activity results in carbonization within or onthe surface of the fiberglass rod.Industry documents discuss two different failure modes for polymerinsulator support rods.Failure of the rod caused by discharge activity and flashunder are relatively slowdegradation processes resulting from discharges in or along the rod. These discharges could occurwhen the rod is exposed to the environment because of a functional failure of either the rubberweathershed system or the end fitting seal. The MPS polymer high-voltage insulators are specificallymanufactured to preclude these degradation processes. TheCR E-Glass rod is housed in a concentricextrudedseamlesssheath ofsilicone rubber. The sheath and the sealing system of the MPS polymerhigh-voltage insulators prevent exposure of the rod to the environment, which mitigates or eliminatesdestruction of the rod by discharge activity and flashunder. Review of industry literature for the type ofpolymer insulator used at RBS did not identify any aging effects requiring management related to failureof the rod by discharge activity and flashunder for polymer high-voltage insulators.e) Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover arediscussed in industry documents for first-generation polymer insulators. Typical problems encounteredwith first-generation polymer insulators included chalking and crazing after a few years of operation.Chalking is a microstructure change on the surface of the insulator forming a powdery surface;however, based on testing, service-aged silicone rubber insulators still maintain acceptablehydrophobic properties with the presence of chalking. Crazing is defined as the formation of surfacecracks that do not affect the operating characteristics of the insulator. Crazing may be an early indicatorof insulator degradation. Review of industry literature did not identify any aging effects requiringmanagement related to chalking and crazing of silicone insulator surfaces as an aging mechanism formore recent generations of polymer insulators, which are used at RBS.f) Water penetration through the sheath followed by electrical failureis discussed in industry documentsfor first-generation polymer insulators. One failure mode observed in first-generation polymer insulatorswas water penetration followed by electrical failure after a few years of operation. This is not discussedas an aging mechanism for more recent generations of polymer insulators, which are used at RBS. Thediscussion in 2(d) provides the information relevant to water penetration into the rod for RBS polymerinsulators.g) Bonding failure at rod and sheathing interface is discussed in industry documents for first-generationpolymer insulators. Failure modes observed in first-generation polymer insulators included bondingfailures and breakdowns along the rod-sheath interface after a few years of operation. There wereseveral discussions of poor bonding of the end fittings, and this is discussed as a mechanical failure.There are manufacturer tests now for identifying poor bonding of the end fittings. End fittings used onRBS insulators are attached using a controlled / automated crimping process to achieve the requiredtensile strength. The end fittings are forged steel, galvanized for protection against corrosion.Therefore, this design mitigates or eliminates mechanical failures. The discussion in 2(a) for SSC and2(d) for water penetration into the rod provides the information relevant to RBS polymer insulators.h) Water ingress through end fittings causing corrosion and fracture of glass fibers is discussed withreferences to operating experience s for early or first-generation polymer insulators. Most of thediscussions of water ingress, immersion, penetration, or diffusion are associated with testing standardsfor manufacturers. This is not discussed as a failure cause for later-generation polymer insulators. Thediscussions in 2(a) for SSC, 2(d) for water penetration into the rod, and 2(g) for bonding failures providethe information relevant to RBS polymer insulators. | DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONFlashover occurs external to the sheath covering the rod; therefore, flashover is not applicable to failureof the rod by discharge activity. Flashunder is initiated by tracking along or through the rod under thesilicone rubber sheath and occurs when internal discharge activity results in carbonization within or onthe surface of the fiberglass rod.Industry documents discuss two different failure modes for polymerinsulator support rods.Failure of the rod caused by discharge activity and flashunder are relatively slowdegradation processes resulting from discharges in or along the rod. These discharges could occurwhen the rod is exposed to the environment because of a functional failure of either the rubberweathershed system or the end fitting seal. The MPS polymer high-voltage insulators are specificallymanufactured to preclude these degradation processes. TheCR E-Glass rod is housed in a concentricextrudedseamlesssheath ofsilicone rubber. The sheath and the sealing system of the MPS polymerhigh-voltage insulators prevent exposure of the rod to the environment, which mitigates or eliminatesdestruction of the rod by discharge activity and flashunder. Review of industry literature for the type ofpolymer insulator used at RBS did not identify any aging effects requiring management related to failureof the rod by discharge activity and flashunder for polymer high-voltage insulators.e) Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover arediscussed in industry documents for first-generation polymer insulators. Typical problems encounteredwith first-generation polymer insulators included chalking and crazing after a few years of operation.Chalking is a microstructure change on the surface of the insulator forming a powdery surface;however, based on testing, service-aged silicone rubber insulators still maintain acceptablehydrophobic properties with the presence of chalking. Crazing is defined as the formation of surfacecracks that do not affect the operating characteristics of the insulator. Crazing may be an early indicatorof insulator degradation. Review of industry literature did not identify any aging effects requiringmanagement related to chalking and crazing of silicone insulator surfaces as an aging mechanism formore recent generations of polymer insulators, which are used at RBS.f) Water penetration through the sheath followed by electrical failureis discussed in industry documentsfor first-generation polymer insulators. One failure mode observed in first-generation polymer insulatorswas water penetration followed by electrical failure after a few years of operation. This is not discussedas an aging mechanism for more recent generations of polymer insulators, which are used at RBS. Thediscussion in 2(d) provides the information relevant to water penetration into the rod for RBS polymerinsulators.g) Bonding failure at rod and sheathing interface is discussed in industry documents for first-generationpolymer insulators. Failure modes observed in first-generation polymer insulators included bondingfailures and breakdowns along the rod-sheath interface after a few years of operation. There wereseveral discussions of poor bonding of the end fittings, and this is discussed as a mechanical failure.There are manufacturer tests now for identifying poor bonding of the end fittings. End fittings used onRBS insulators are attached using a controlled / automated crimping process to achieve the requiredtensile strength. The end fittings are forged steel, galvanized for protection against corrosion.Therefore, this design mitigates or eliminates mechanical failures. The discussion in 2(a) for SSC and2(d) for water penetration into the rod provides the information relevant to RBS polymer insulators.h) Water ingress through end fittings causing corrosion and fracture of glass fibers is discussed withreferences to operating experience s for early or first-generation polymer insulators. Most of thediscussions of water ingress, immersion, penetration, or diffusion are associated with testing standardsfor manufacturers. This is not discussed as a failure cause for later-generation polymer insulators. Thediscussions in 2(a) for SSC, 2(d) for water penetration into the rod, and 2(g) for bonding failures providethe information relevant to RBS polymer insulators. | ||
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONIndustry operating experience was summarized for polymer insulators in the response to RAI 3.6.2.2.2-1. Thisoperating experience provided information on failures from EPRI's polymer insulator database and includedspecific information on failures of MPS polymer insulators. In addition, the response to RAI 3.6.2.2.2-1provided information on aging studies performed for polymer insulators. The applicable aging mechanisms andstressors identified by the industry for polymer high-voltage insulators were considered as part of the operatingexperience and aging studies discussion in the response to RAI 3.6.2.2.2-1, and as part of the aging effectsevaluation for polymer high-voltage insulators. The aging effects of reduced insulation resistance due todeposits or surface contamination, loss of material due to mechanical wear caused by wind blowing ontransmission conductors, and reduced insulation resistance due to polymer degradation were discussed.Part 3Based on a search of industry documents, degradation of polymer insulators from "bird" and "rodent"excrement was not identified. An industry document providing guidance on the selection, specification, andprocurement of composite insulators for transmission lines discussed advantages and disadvantages fordifferent insulator technologies including older generation composite insulators. For composite insulators,"Susceptible to damage from birds and rodents" was postulated as a disadvantage, but there was no operatingexperience or aging studies cited for this claim.An environment due to excrement from rodents is not applicable to the transmission conductor polymer high-voltage insulators. Site operating experience has not identified an environment due to excrement frombirds forthe transmission conductors, the polymer high-voltage insulators, or the porcelain high-voltage insulators.Therefore, there is not anaggressive environment due to excrement from birds and rodents containingchemicals such as uric acid, phosphates, and ammonia for polymer high-voltage insulators.Part 4As discussed in the in the response to RAI 3.6.2.2.2-1, the following aging effects for polymer high-voltageinsulators were evaluated. reduced insulation resistance due to deposits or surface contamination loss of material due to mechanical wear caused by wind blowing on transmission conductors reduced insulation resistance due to polymer degradationAs stated in the response to RAI 3.6.2.2.2-1, the aging effect of loss of material due to mechanical wearcaused by wind blowing on transmission conductors is the same for polymer high-voltage insulators as forporcelain high-voltage insulators. The end components and the connection hardware for the polymer high-voltage insulators are similar in design and material to those of the porcelain high-voltage insulators. Asdiscussed in LRA Section 3.6.2.2.2 for porcelain high-voltage insulators,loss of material (wear) and fatigue thatcould be caused by transmission conductor vibration or sway are not applicable aging effects in that theywould not cause a loss of intended function if left unmanaged for the period of extended operation. LRA Table3.6.2 was updated to include a polymer insulator line item to align with Table 3.6.1, Item 3.6.1-2.For discussions of aging management and LRA Table 3.6.2, the other two aging effects listed in the responseto RAI 3.6.2.2.2-1 were combined into reduced insulation resistance. As previously indicated, reducedinsulationresistanceis the aging effect, which can be due to the mechanisms of polymer degradation or DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONsurface contamination.While reduced insulation resistance is not expected, RBS will include preventive maintenance activities in thePeriodic Surveillance and Preventive Maintenance Program to provide assurance that the effects of aging willnot prevent the polymer high-voltage insulators from continuing to perform their intended function during theperiod of extended operation.Preventive maintenance activities will include performing a corona scan (UV) and visual inspection of polymerhigh-voltage insulators on the RSS#1 and RSS#2 lines to the plant every 6 years to detect indications ofreduced insulation resistance. | DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONIndustry operating experience was summarized for polymer insulators in the response to RAI 3.6.2.2.2-1. Thisoperating experience provided information on failures from EPRI's polymer insulator database and includedspecific information on failures of MPS polymer insulators. In addition, the response to RAI 3.6.2.2.2-1provided information on aging studies performed for polymer insulators. The applicable aging mechanisms andstressors identified by the industry for polymer high-voltage insulators were considered as part of the operatingexperience and aging studies discussion in the response to RAI 3.6.2.2.2-1, and as part of the aging effectsevaluation for polymer high-voltage insulators. The aging effects of reduced insulation resistance due todeposits or surface contamination, loss of material due to mechanical wear caused by wind blowing ontransmission conductors, and reduced insulation resistance due to polymer degradation were discussed.Part 3Based on a search of industry documents, degradation of polymer insulators from "bird" and "rodent"excrement was not identified. An industry document providing guidance on the selection, specification, andprocurement of composite insulators for transmission lines discussed advantages and disadvantages fordifferent insulator technologies including older generation composite insulators. For composite insulators,"Susceptible to damage from birds and rodents" was postulated as a disadvantage, but there was no operatingexperience or aging studies cited for this claim.An environment due to excrement from rodents is not applicable to the transmission conductor polymer high-voltage insulators. Site operating experience has not identified an environment due to excrement frombirds forthe transmission conductors, the polymer high-voltage insulators, or the porcelain high-voltage insulators.Therefore, there is not anaggressive environment due to excrement from birds and rodents containingchemicals such as uric acid, phosphates, and ammonia for polymer high-voltage insulators.Part 4As discussed in the in the response to RAI 3.6.2.2.2-1, the following aging effects for polymer high-voltageinsulators were evaluated. reduced insulation resistance due to deposits or surface contamination loss of material due to mechanical wear caused by wind blowing on transmission conductors reduced insulation resistance due to polymer degradationAs stated in the response to RAI 3.6.2.2.2-1, the aging effect of loss of material due to mechanical wearcaused by wind blowing on transmission conductors is the same for polymer high-voltage insulators as forporcelain high-voltage insulators. The end components and the connection hardware for the polymer high-voltage insulators are similar in design and material to those of the porcelain high-voltage insulators. Asdiscussed in LRA Section 3.6.2.2.2 for porcelain high-voltage insulators,loss of material (wear) and fatigue thatcould be caused by transmission conductor vibration or sway are not applicable aging effects in that theywould not cause a loss of intended function if left unmanaged for the period of extended operation. LRA Table3.6.2 was updated to include a polymer insulator line item to align with Table 3.6.1, Item 3.6.1-2.For discussions of aging management and LRA Table 3.6.2, the other two aging effects listed in the responseto RAI 3.6.2.2.2-1 were combined into reduced insulation resistance. As previously indicated, reducedinsulationresistanceis the aging effect, which can be due to the mechanisms of polymer degradation or DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONsurface contamination.While reduced insulation resistance is not expected, RBS will include preventive maintenance activities in thePeriodic Surveillance and Preventive Maintenance Program to provide assurance that the effects of aging willnot prevent the polymer high-voltage insulators from continuing to perform their intended function during theperiod of extended operation.Preventive maintenance activities will include performing a corona scan (UV) and visual inspection of polymerhigh-voltage insulators on the RSS#1 and RSS#2 lines to the plant every 6 years to detect indications ofreduced insulation resistance. | ||
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONThe changes to LRA Table 3.6.2, and Sections A.1.34 and B.1.34 follow with additions underlined anddeletions lined through.Table 3.6.2: Electrical and I&C ComponentsA.1.34 Periodic Surveillance and Preventive MaintenanceCredit for program activities has been taken in the aging management review for the following components orcommodities.Inspect the surface of the polymer high-voltage insulators for transmission conductors on the RSS#1and RSS#2 linesPerform corona scans (UV) of the polymer high-voltage insulators for transmission conductors on theRSS#1 and RSS#2 linesStructure and/orComponent orCommodityIntendedFunctionMaterialEnvironmentAging | DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONThe changes to LRA Table 3.6.2, and Sections A.1.34 and B.1.34 follow with additions underlined anddeletions lined through.Table 3.6.2: Electrical and I&C ComponentsA.1.34 Periodic Surveillance and Preventive MaintenanceCredit for program activities has been taken in the aging management review for the following components orcommodities.Inspect the surface of the polymer high-voltage insulators for transmission conductors on the RSS#1and RSS#2 linesPerform corona scans (UV) of the polymer high-voltage insulators for transmission conductors on theRSS#1 and RSS#2 linesStructure and/orComponent orCommodityIntendedFunctionMaterialEnvironmentAging EffectRequiringManagementAgingManagementProgram NUREG-1801 ItemTable 1 Item NotesHigh-voltageinsulators -Polymer (high-voltage insulatorsfor SBO recovery) | ||
INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor | INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor None Reducedinsulationresistance NonePeriodicSurveillanceand PreventiveMaintenance | ||
----FHigh-voltageinsulators -Polymer (high-voltage insulatorsfor SBO recovery) | ----FHigh-voltageinsulators -Polymer (high-voltage insulatorsfor SBO recovery) | ||
INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor | INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor None NoneVI.A.LP-32 VI.A-10(LP-11)3.6.1-2 I DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONA.4 LICENSE RENEWAL COMMITMENT LISTNo.Program or ActivityCommitmentImplementationScheduleSource(Letter Number) 24Periodic Surveillanceand PreventiveMaintenanceEnhance the PSPM Program as described in LRASection A.1.34.Prior to February 28,2025, or the end of thelast refueling outageprior to August 29,2025, whichever islater.RBG-47735RBG-47861 DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONB.1.34 PERIODIC SURVEILLANCE AND PREVENTIVE MAINTENANCECredit for program activities has been taken in the aging management review for the following commodities,systems and structures.Polymer high-voltageinsulators for thetransmissionconductors on theRSS#1 and RSS#2linesPerform a corona scan (UV) of polymer high-voltage insulators todetect reduced insulation resistance due to deposits or surfacecontamination, and reduced insulation resistance due to polymerdegradation.Polymer high-voltageinsulators for thetransmissionconductors on theRSS#1 and RSS#2linesPerform a visual inspection of the polymer high-voltage insulatorsvia routine aerial patrol of transmission linesto detect deposits orsurface contamination, and loss of material due to mechanicalwear.}} | ||
Revision as of 22:53, 5 July 2018
| ML18141A488 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 05/21/2018 |
| From: | Wong A NRC/NRR/DMLR/MRPB |
| To: | |
| Wong A, NRR-DMLR 415-3081 | |
| References | |
| Download: ML18141A488 (11) | |
Text
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONQuestionRAI 3.6.2.2.2-1a (High Voltage Insulators)LRA 3.6.2.2.2 Degradation of Insulator Quality due to Presence of Any Salt Deposits and SurfaceContamination, and Loss of Material due to Mechanical WearRegulatory BasisSection 54.21(a)(1) of 10 CFR requires the applicant to identify and list those structures and componentssubject to an aging management review. Section 54.21(a)(3) of 10 CFR requires the applicant to demonstratethat the effects of aging for structures and components within the scope of license renewal and subject to anAMR pursuant to 10 CFR 54.21(a)(1) will be adequately managed so that the intended function(s) will bemaintained consistent with the current licensing basis for the period of extended operation. As described inSRP-LR, an applicant may demonstrate compliance with 10 CFR 54.21(a)(3) by referencing the GALL Reportwhen evaluation of the matter in the GALL Report applies to the plant.Section 3.6.2.2.2 of SRP-LR, "Reduced Insulation Resistance due to Presence of Any Salt Deposits andSurface Contamination, and Loss of Material due to Mechanical Wear Caused by Wind Blowing onTransmission Conductors" states that: "Loss of material due to mechanical wear caused by wind blowing ontransmission conductors could occur in high-voltage insulators. The GALL Report recommends furtherevaluation of a plant-specific AMP to ensure that this aging effect is adequately managed." The GALL reportalso recommends further evaluation of plant-specific AMP for potential salt deposits and surfacecontamination.BackgroundIn LRA 3.6.2.2.2, the applicant references SRP-LR for further evaluation of the above aging mechanisms andeffects for high-voltage insulators. Table 3.6.1, line item numbers 3.6.1-2 and 3.6.1-3 identify the componentas: "High voltage insulators composed of porcelain, malleable iron, aluminum, galvanized steel and cement."The corresponding items in Table 3.6.2 of the LRA identify the materials as: "Porcelain, galvanized metal andcement."During the onsite audit /walkdown, the staff noted that in-scope high-voltage insulators on the 230 kVtransmission lines are constructed of polymer material rather than the porcelain material listed in LRA Table3.6.1 and Table 3.6.2. The applicant stated that the porcelain insulators had been replaced with new insulatorsmade of polymeric material in 2008. The actual material (polymer) used in construction of the polymer in-scope high-voltage insulators are not identified in the applicant's LRA.Staff issued RAI 3.6.2.2.2-1 to obtain clarification on why the LRA did not address the replacementcomponents and aging effects related to polymer high-voltage insulators. The RAI and the applicant'sresponse are documented in ADAMS Accession No. ML 18051A531, dated February 20, 2018. In itsresponse, the applicant provided update to LRA section 3.6.2.1 as well as adding a new line item to AMR table3.6.2 for polymer high-voltage insulators. The applicant also provided further evaluation discussions inresponse to RAI 2.6.2.2.2-1 for these components and concluded that there are no aging effects requiringmanagement and did not propose a site-specific aging management program.The staff's review of the RAI response as well as industry literature, vendor documents, RBS procedures andwork orders identified some material used in the construction of the polymer high-voltage insulators that werenot listed in the applicant's changes to the LRA. Specifically, according to vendor and EPRI literature providedby the applicant, the missing material include: epoxy, silicone gel, sealants, and ductile iron.The staff's review of the RAI response and relevant technical information provided by the applicant further DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONidentified pertinent aging effects and mechanisms not addressed in the applicant's response. These include:Stress corrosion cracking of glass fibersSwelling of silicone rubber (SIR) layer due to chemical contaminationSheath wetting caused by chemicals absorbed by oil from SIR compoundBrittle fracture of rods resulting from discharge activity, flashunder, and flashoverChalking and crazing of insulator surfaces resulting in contamination, arcing, and flashoverBonding failure at rod and sheathing interfaceWater ingress through end fittings causing flashunder, corrosion and fracture of glass fibersThe staff also noted that rodent and bird excrement containing aggressive chemicals such as phosphates, uricacid, and ammonia create an environment that can cause sheath layer damage and subsequent failures of thecore material and fittings. Susceptibility of these components to this environment, which has not beenreviewed in GALL needs to be addressed.According to research results, aging studies and handbook material provided by the applicant, polymerinsulators have been shown to have unique failure modes with little advance indications. This information alsoindicates that contamination can be worse for SIR (compared to porcelain insulators) due to absorption bysilicone oil, especially in late stages of service life.The staff and representatives of the applicant held a public telephone conference call on April 18, 2018, todiscuss the applicant's responses to RAI 3.6.2.2.2.2-1 and issues outlined below.Issues 1.The material listed in the applicant's response to RAI 3.6.2.2.2-1 seems to have omitted certainmaterial that are used in construction of the polymer insulators. According to vendor and EPRIliterature, these include: epoxy, silicone gel, sealants, and ductile iron.
2.The aging effects and mechanisms addressed in the applicant's response to RAI 3.6.2.2.2-1 seem tohave addressed some, but not all relevant aging effects requiring management (AERM). The AERMsnot considered in the response include the following:
a.Stress corrosion cracking (SCC) of glass fibers due to sheath degradation b.Swelling of SIR layer due to chemical contamination c.Sheath wetting caused by chemicals absorbed by oil from SIR compound d.Brittle fracture of rods resulting from discharge activity, flashunder, and flashover e.Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover f.Water penetration through the sheath followed by electrical failure g.Bonding failure at rod and sheathing interface h.Water ingress through end fittings causing flashunder, corrosion and fracture of glass fibers 3.Additionally, aggressive environment due to excrements from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers is notaddressed in the applicant's response to RAI 3.6.2.2.2-1. This environment and material combinationhas not previously been evaluated in the GALL Report and constitutes a condition that should beassessed for RBS.
4.The applicant concluded, in its response to RAI 3.6.2.2.2-1, that an aging management program willnot be implemented for polymer high-voltage insulators. The staff noted that polymer insulators haveshown to have unique failure modes with little advance indications. Furthermore, contaminationbuildup can be worse for SIR (compared to porcelain insulators) due to absorption by silicone oil,especially in late stages of service life. It appears that the applicant's conclusion is based on the DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONassumption that polymer insulators are more reliable than porcelain and less likely to be affected byaging degradation, primarily due to the hydrophobic characteristics of the polymers and reducedpossibility of chemicals and particulate matter buildup on the surfaces of the insulators. The staffnotes that the licensee's response does not include consideration of new and unique degradationmechanisms and sensitivity to the environment, especially during later stages of service life, typicallypast the twenty-year period. It is not clear to the staff whether the applicant's conclusion considers allaspects of polymer insulators' degradation and aging that can result in aging effects such as reducedinsulation resistance and loss of material which may require aging management.Request 1.Explain why epoxy, silicone gel, sealants, and ductile iron are not listed in the response to RAI3.6.2.2.2-1 as materials that are used in construction of polymer high-voltage insulators.
2.Explain why certain aging effects and mechanisms that have been identified for polymer high-voltageinsulators, by industry as a result of operating experience reviews and aging study research, have notbeen considered in response to RAI 3.6.2.2.2-1. These aging effects and mechanisms are listed aboveunder the heading "Issues," items 2 (a) through (h).
3.Explain why aggressive environment due to excrement from birds and rodents containing chemicalssuch as uric acid, phosphates, and ammonia that can accelerate degradation of polymers has not beenaddressed in the response to RAI 3.6.2.2.2-1. This environment and material combination has notpreviously been evaluated in the GALL Report and constitutes a site-specific condition to be assessedfor RBS.4.Considering polymer insulators' degradation, aging, and failure mechanisms that may require agingmanagement, provide a discussion of any site-specific aging management program needed to ensurethat the aging effects such as reduced insulation resistance and loss of material for these componentscomposed of polymers, epoxy, silicone gel, sealants, and ductile iron will be adequately managed.Describe what parameters will be monitored or inspected to detect the AERM and how the frequency ofinspection will be established. If no program will be used, justify why loss of material, reducedinsulation resistance, presence of deposits, rod fiber glass degradation, SCC of fiber glass material,wetting and swelling of SIR, accelerated aging of polymer material due to discharge current activity andcorona, chalking and crazing of surfaces, tracking, corona, loosening of sheath layers, bonding failureat rod/sheath interface, separation of seals and sealants, water ingress through end fittings, andsurface contamination are not applicable for the polymer high-voltage insulators exposed to air-outdoorand chemicals such as uric acid, phosphates and ammonia from birds and rodents.ResponsePart 1Information from the manufacturer (MacLean Power Systems or MPS) of the RBS polymer insulators does notdiscuss "ductile iron" for the corona ring or the end fittings, which are the only metal components on theinsulators. The connection hardware does include ductile iron.The response to RAI 3.6.2.2.2-1 stated, "The RBS polymer high-voltage insulators and connection hardwarehave the following materials: fiberglass, silicone rubber, aluminum and aluminum alloy, steel and steel alloys, DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONgalvanized metal (galvanized ductile iron, galvanized forged steel, steel hot dip galvanized)." Therefore,galvanized ductile iron is explicitly identified.The RBS polymer high-voltage insulators are a recent generation of MPS polymer insulators that have beenmanufactured since 2007. The RBS polymer insulators do not use epoxy. The following figure shows thedifference between the first generation of MPS polymer insulators and the generation of MPS polymerinsulators that are used at RBS.The MPS polymer insulators in service at RBS use a PST sealing system, which is a triple seal design. Thetriple seal or PST seal comprises the primary seal (P), the secondary seal (S), and the tertiary seal (T). Theprimary seal is a silicone rubber sheath compressed into the chamfer of the crimped end fitting. The secondaryseal is RTV (room temperature vulcanizing) silicone applied to the rod, sheath, and end fitting interface. Thetertiary seal is a final external RTV silicone seal applied to the sheath and end fitting interface. The RBSpolymer insulators do not utilize silicone gel. The response to RAI 3.6.2.2.2-1 included silicone rubber, but didnot explicitly identify RTV silicone as a type of silicone rubber. The silicone rubber material includes the RTVsilicone that is part of the PST seal system. The RBS polymer insulators do not includesilicone gel or sealantsother than RTV silicone.Part 2The aging effects on polymer high-voltage insulators are the same as the aging effects on porcelain high-voltage insulators. Those aging effects are reduced insulation resistance and loss of material. Polymerdegradation is an additional mechanism unique to polymer high-voltage insulators that can cause the agingeffect of reduced insulation resistance.The items identified in part 2 of the issue as Items a) through h) are discussed in the following sections. Each DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONdiscussion describes how the item was considered in the aging management review of RBS polymer high-voltage insulators. The functions of high-voltage insulators are to insulate and support a high-voltageconductor. The failure of one high-voltage insulator does not cause the loss of the function of the high-voltageinsulator system to insulate and support a high-voltage conductor.a) Rod failures of early generation polymer insulators have been linked to stress corrosion cracking (SCC)resulting from infiltration of water into the fiberglass/glass reinforced plastic(GRP)rod. The failureshave been attributed to either acid or water leaching of the metallic ions in the glass fibers resulting instress corrosion cracking. SCC in an E-glass polymer composite results from the combined effect oflow mechanical tensile stresses applied along the fibers and chemical attack of either organic orinorganic acids. Known in the industry as brittle fracture this failure of the polymer insulator rods isgenerally associated with high-voltage applications in which nitric acid or other acids can be present. Inorder to avoid such failures, water is prevented from migrating into the end fittings of polymerinsulators. In-service failures have been observed when nitric acid forms and reaches the rod surface.The polymer high-voltage insulators installed on the 230 kV offsite power recovery paths for RBS arespecifically manufactured to eliminate the conditions that can cause brittle fracture of the polymerinsulator support rod. For these insulators, the fiberglass rod is a boron-free corrosion-resistant (CR) E-Glass, which is resistant to nitric acid attacks. There has never been a brittle facture failure of a MPSCR E-glassrod in an MPS polymerinsulator in over 30 years of use. Review of industry literatureapplicable to RBS polymer high-voltage insulators did not identify any aging effects requiringmanagement related to brittle fracture of the glass support rods.b) Swelling of SIR layer due to chemical contamination is not identified in industry documents as a causeof loss of function in high-voltage polymer insulators. One industry document, published in October2003, discusses that solvents can swell polymers, and that some polymer characterization tests arebased upon the degree of swelling of the unknown polymer in different solvents; the swelling ratios canfingerprint the polymer. The other discussion of swelling in this document is that studies could beperformed to determine chemical environments (unique chemicals or cocktails) that would theoreticallyassess the potential for swelling or other degradation that could change the water permeability orhydrophobic properties of the water shed polymer. No studies were found for using solvents to createpotential problems for silicone rubber polymers. Also, solvents are not found in the air environment ofhigh-voltage insulators at RBS. Review of industry literature for the type of polymer insulator used atRBS did not identify any aging effects requiring management related to swelling of silicone rubberinsulator components due to chemical contamination for polymer high-voltage insulators.c) Sheath wetting caused by chemicals absorbed by oil from SIR compound was not found as a failurecause for polymer insulators. Discussions of sheath wetting were not identified for polymer insulators.There are industry documents that contain statements from an old reference citing that silicone rubberinsulators, due to the presence of the silicone oils, collect more contaminants than glass or ceramicsurfaces. Later industry documents refuted this old reference, by stating that silicone rubber (SR) isnaturally hydrophobic, has excellent resistance to UV, and minimizes leakage currents on the surfaceof the insulator, all of which help polymer insulators perform well in contaminated environments. Thisposition was discussed in greater detail in the response to RAI 3.6.2.2.2-1. Review of industry literaturefor the type of polymer insulator used at RBS did not identify any aging effects requiring managementrelated to sheath wetting caused by chemical absorption for polymer high-voltage insulators.d) Failure of rods resulting from discharge activity, flashunder, and flashover is not called brittle facture inindustry documents. Brittle fracture due to stress corrosion cracking is discussed in item 2(a) above.
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONFlashover occurs external to the sheath covering the rod; therefore, flashover is not applicable to failureof the rod by discharge activity. Flashunder is initiated by tracking along or through the rod under thesilicone rubber sheath and occurs when internal discharge activity results in carbonization within or onthe surface of the fiberglass rod.Industry documents discuss two different failure modes for polymerinsulator support rods.Failure of the rod caused by discharge activity and flashunder are relatively slowdegradation processes resulting from discharges in or along the rod. These discharges could occurwhen the rod is exposed to the environment because of a functional failure of either the rubberweathershed system or the end fitting seal. The MPS polymer high-voltage insulators are specificallymanufactured to preclude these degradation processes. TheCR E-Glass rod is housed in a concentricextrudedseamlesssheath ofsilicone rubber. The sheath and the sealing system of the MPS polymerhigh-voltage insulators prevent exposure of the rod to the environment, which mitigates or eliminatesdestruction of the rod by discharge activity and flashunder. Review of industry literature for the type ofpolymer insulator used at RBS did not identify any aging effects requiring management related to failureof the rod by discharge activity and flashunder for polymer high-voltage insulators.e) Chalking and crazing of insulator surfaces resulting in contamination, arcing, and flashover arediscussed in industry documents for first-generation polymer insulators. Typical problems encounteredwith first-generation polymer insulators included chalking and crazing after a few years of operation.Chalking is a microstructure change on the surface of the insulator forming a powdery surface;however, based on testing, service-aged silicone rubber insulators still maintain acceptablehydrophobic properties with the presence of chalking. Crazing is defined as the formation of surfacecracks that do not affect the operating characteristics of the insulator. Crazing may be an early indicatorof insulator degradation. Review of industry literature did not identify any aging effects requiringmanagement related to chalking and crazing of silicone insulator surfaces as an aging mechanism formore recent generations of polymer insulators, which are used at RBS.f) Water penetration through the sheath followed by electrical failureis discussed in industry documentsfor first-generation polymer insulators. One failure mode observed in first-generation polymer insulatorswas water penetration followed by electrical failure after a few years of operation. This is not discussedas an aging mechanism for more recent generations of polymer insulators, which are used at RBS. Thediscussion in 2(d) provides the information relevant to water penetration into the rod for RBS polymerinsulators.g) Bonding failure at rod and sheathing interface is discussed in industry documents for first-generationpolymer insulators. Failure modes observed in first-generation polymer insulators included bondingfailures and breakdowns along the rod-sheath interface after a few years of operation. There wereseveral discussions of poor bonding of the end fittings, and this is discussed as a mechanical failure.There are manufacturer tests now for identifying poor bonding of the end fittings. End fittings used onRBS insulators are attached using a controlled / automated crimping process to achieve the requiredtensile strength. The end fittings are forged steel, galvanized for protection against corrosion.Therefore, this design mitigates or eliminates mechanical failures. The discussion in 2(a) for SSC and2(d) for water penetration into the rod provides the information relevant to RBS polymer insulators.h) Water ingress through end fittings causing corrosion and fracture of glass fibers is discussed withreferences to operating experience s for early or first-generation polymer insulators. Most of thediscussions of water ingress, immersion, penetration, or diffusion are associated with testing standardsfor manufacturers. This is not discussed as a failure cause for later-generation polymer insulators. Thediscussions in 2(a) for SSC, 2(d) for water penetration into the rod, and 2(g) for bonding failures providethe information relevant to RBS polymer insulators.
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONIndustry operating experience was summarized for polymer insulators in the response to RAI 3.6.2.2.2-1. Thisoperating experience provided information on failures from EPRI's polymer insulator database and includedspecific information on failures of MPS polymer insulators. In addition, the response to RAI 3.6.2.2.2-1provided information on aging studies performed for polymer insulators. The applicable aging mechanisms andstressors identified by the industry for polymer high-voltage insulators were considered as part of the operatingexperience and aging studies discussion in the response to RAI 3.6.2.2.2-1, and as part of the aging effectsevaluation for polymer high-voltage insulators. The aging effects of reduced insulation resistance due todeposits or surface contamination, loss of material due to mechanical wear caused by wind blowing ontransmission conductors, and reduced insulation resistance due to polymer degradation were discussed.Part 3Based on a search of industry documents, degradation of polymer insulators from "bird" and "rodent"excrement was not identified. An industry document providing guidance on the selection, specification, andprocurement of composite insulators for transmission lines discussed advantages and disadvantages fordifferent insulator technologies including older generation composite insulators. For composite insulators,"Susceptible to damage from birds and rodents" was postulated as a disadvantage, but there was no operatingexperience or aging studies cited for this claim.An environment due to excrement from rodents is not applicable to the transmission conductor polymer high-voltage insulators. Site operating experience has not identified an environment due to excrement frombirds forthe transmission conductors, the polymer high-voltage insulators, or the porcelain high-voltage insulators.Therefore, there is not anaggressive environment due to excrement from birds and rodents containingchemicals such as uric acid, phosphates, and ammonia for polymer high-voltage insulators.Part 4As discussed in the in the response to RAI 3.6.2.2.2-1, the following aging effects for polymer high-voltageinsulators were evaluated. reduced insulation resistance due to deposits or surface contamination loss of material due to mechanical wear caused by wind blowing on transmission conductors reduced insulation resistance due to polymer degradationAs stated in the response to RAI 3.6.2.2.2-1, the aging effect of loss of material due to mechanical wearcaused by wind blowing on transmission conductors is the same for polymer high-voltage insulators as forporcelain high-voltage insulators. The end components and the connection hardware for the polymer high-voltage insulators are similar in design and material to those of the porcelain high-voltage insulators. Asdiscussed in LRA Section 3.6.2.2.2 for porcelain high-voltage insulators,loss of material (wear) and fatigue thatcould be caused by transmission conductor vibration or sway are not applicable aging effects in that theywould not cause a loss of intended function if left unmanaged for the period of extended operation. LRA Table3.6.2 was updated to include a polymer insulator line item to align with Table 3.6.1, Item 3.6.1-2.For discussions of aging management and LRA Table 3.6.2, the other two aging effects listed in the responseto RAI 3.6.2.2.2-1 were combined into reduced insulation resistance. As previously indicated, reducedinsulationresistanceis the aging effect, which can be due to the mechanisms of polymer degradation or DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONsurface contamination.While reduced insulation resistance is not expected, RBS will include preventive maintenance activities in thePeriodic Surveillance and Preventive Maintenance Program to provide assurance that the effects of aging willnot prevent the polymer high-voltage insulators from continuing to perform their intended function during theperiod of extended operation.Preventive maintenance activities will include performing a corona scan (UV) and visual inspection of polymerhigh-voltage insulators on the RSS#1 and RSS#2 lines to the plant every 6 years to detect indications ofreduced insulation resistance.
DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONThe changes to LRA Table 3.6.2, and Sections A.1.34 and B.1.34 follow with additions underlined anddeletions lined through.Table 3.6.2: Electrical and I&C ComponentsA.1.34 Periodic Surveillance and Preventive MaintenanceCredit for program activities has been taken in the aging management review for the following components orcommodities.Inspect the surface of the polymer high-voltage insulators for transmission conductors on the RSS#1and RSS#2 linesPerform corona scans (UV) of the polymer high-voltage insulators for transmission conductors on theRSS#1 and RSS#2 linesStructure and/orComponent orCommodityIntendedFunctionMaterialEnvironmentAging EffectRequiringManagementAgingManagementProgram NUREG-1801 ItemTable 1 Item NotesHigh-voltageinsulators -Polymer (high-voltage insulatorsfor SBO recovery)
INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor None Reducedinsulationresistance NonePeriodicSurveillanceand PreventiveMaintenance
FHigh-voltageinsulators -Polymer (high-voltage insulatorsfor SBO recovery)
INFiberglass,siliconerubber,aluminum andaluminumalloy, steel andgalvanizedmetalsAir - outdoor None NoneVI.A.LP-32 VI.A-10(LP-11)3.6.1-2 I DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONA.4 LICENSE RENEWAL COMMITMENT LISTNo.Program or ActivityCommitmentImplementationScheduleSource(Letter Number) 24Periodic Surveillanceand PreventiveMaintenanceEnhance the PSPM Program as described in LRASection A.1.34.Prior to February 28,2025, or the end of thelast refueling outageprior to August 29,2025, whichever islater.RBG-47735RBG-47861 DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONB.1.34 PERIODIC SURVEILLANCE AND PREVENTIVE MAINTENANCECredit for program activities has been taken in the aging management review for the following commodities,systems and structures.Polymer high-voltageinsulators for thetransmissionconductors on theRSS#1 and RSS#2linesPerform a corona scan (UV) of polymer high-voltage insulators todetect reduced insulation resistance due to deposits or surfacecontamination, and reduced insulation resistance due to polymerdegradation.Polymer high-voltageinsulators for thetransmissionconductors on theRSS#1 and RSS#2linesPerform a visual inspection of the polymer high-voltage insulatorsvia routine aerial patrol of transmission linesto detect deposits orsurface contamination, and loss of material due to mechanicalwear.