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| Quarter | Site | Title | Description | |
|---|---|---|---|---|
| 05000528/FIN-2010007-01 | 2010Q1 | Palo Verde | Impact of recent operating experience on Metal-Enclosed Bus program | The Metal-Enclosed Bus program was a new program, consistent with the GALL Report, credited with managing the aging affects associated with loosening of bolted bus bar connections and reduced insulation and insulator resistance on bus ducts. Metal-enclosed buses are electrical buses installed on electrically insulated supports enclosed in a metal duct. The parameters monitored include loose connections, embrittlement, cracking, melting, swelling or discoloration of insulation, loss of material of bus enclosure assemblies, hardening of boots and gaskets, and cracking of internal bus supports. The applicant included these non safety-related bus ducts because the ducts supported compliance with the station blackout regulations. The applicant scoped in the following non-segregated bus ducts (all conductors enclosed in a common metal enclosure) listed below:1,2,3 NBNA031,2,3 NBNA041,2,3 NBNA051,2,3 NBNA061,2,3 NBNA081,2,3 NBNA09Secondary of Engineered Safety Features Service Transformer E-NBN-X03 to NBN-A08 and NBN-A09Secondary of Engineered Safety Features Service TransformerE-NBN-X04 to NBN-A05 and NBN-A06Connection between Bus NBN-A04 and Vital Bus E-PBA-S03Connection between Bus NBN-A04 and Vital Bus E-PBB-S04Connection between Bus NBN-A03 and Vital Bus E-PBA-S03Connection between Bus NBN-A03 and Vital Bus E-PBB-S04The team reviewed license renewal program basis documents, aging management review documents, existing and new procedures, and preventive maintenance requirements. The team interviewed the license renewal project personnel and the responsible plant and design engineers. The team walked down all the in-scope non-segregated bus ducts. The applicant had developed Procedure 82DP-OEE01, Electrical Aging Management, Draft B, which included qualitative and quantitative acceptance criteria for the inspection of metal enclosed bus internal assemblies. The procedure established the following requirements to monitor for aging effects: (1) inspect a sample of the accessible bolted connections for evidence of overheating; (2) conduct contact resistance testing of a sample of the accessible splice plates to check for loose connections; (3) inspect each bus section for cracks, corrosion, foreign debris, excessive dust buildup, and evidence of water intrusion; (4) inspect the bus insulation for signs of embrittlement, cracking, melting, swelling, or discoloration; and (5) inspect the internal bus supports for structural integrity and signs of cracking. The procedure used visual inspection of bus enclosure assemblies to monitor for loss of material resulting from corrosion and hardening of boots and gaskets. The applicant will allow no unacceptable indications of cracking and will use thermography to determine if excessive heating occurred. The metal enclosed bus inspections will be completed before the period of extended operation and every 10 years as specified by the GALL Report. The team determined that the applicant had an existing preventive maintenance program to inspect and clean bus ducts. The applicant inspected sections of the metal enclosed buses every other outage and performed thermography on the bus at the transformer connections once every 6 months. At the time of the onsite inspection, from review of the corrective action database, the team determined that the applicant had not found any occurrences of corrosion, loss of material, hardening, foreign debris, excessive dust buildup, water intrusion, or overheating that changed the scope of this aging management program. The team did review onsite operating experience that reinforced the need for these inspections. The previous operating experience related to Noryl insulation failures and ground faults on non-segregated bus ducts of components not within the scope of license renewal that resulted in ground faults on the affected buses. Subsequent to the onsite inspection, on March 7, 2010, Unit 1 tripped when a ground fault occurred on Bus 1E-NAN-A03 connecting the non-class 1E 13.8 kV Bus 1E-NAN-S01 to Breaker 1E-NAN-S03B. Because of heavy rains, water intruded past the cover protecting the non segregated bus. The applicant preliminarily concluded the fault resulted from an improperly installed bus duct cover and a breakdown in theNoryl insulation because of aging mechanisms. Because additional information was needed to determine whether a recent age-related failure would impact the proposed aging management program, this is an unresolved item: Unresolved Item 05000528, 05000529, 05000530/2010007-01, Impact of recent operating experience on Metal-Enclosed Bus program. For the Metal-Enclosed Bus program, although some questions remain related to the impact on this program of recent operating experience, the team concluded that the applicant had performed appropriate evaluations and considered pertinent industry experience and plant operating history to determine the effects of aging on the metal enclosed non-segregated bus ducts. The team concluded that, if implemented as described, the applicant provided guidance to appropriately identify and address aging effects during the period of extended operation |
| 05000528/FIN-2010007-02 | 2010Q1 | Palo Verde | Structures monitoring frequency and scope | The Structures Monitoring program was an existing program, consistent with the GALL Report after enhancement, credited with managing cracking, loss of material, and change in material properties of concrete structures and structural supports. The applicant used guidance contained in Procedure 81 DP-OZZ01, Civil System and Component Monitoring Program, to conduct structural inspections. The applicant will enhance the program to require that inspection personnel meet the requirements of American Concrete Institute 349.3R-96 related to qualifications of inspection personnel. The Structures Monitoring program provided inspection guidelines for concrete elements, structural steel, masonry walls, structural features (e.g., caulking, sealants, roofs, etc.), structural supports, and miscellaneous components such as doors. The Structures Monitoring program included all masonry walls and water-control structures within the scope of license renewal. The Structures Monitoring program also monitored settlement of each major structure and inspected supports for equipment, piping, conduit, cable tray, metal-enclosed bus, heating ventilation and air conditioning, and instrument components. The team reviewed the license renewal program basis documents, aging management review documents, and existing procedures. The team searched the corrective action database for relevant condition reports and evaluated the licensee evaluation of operating experience. The team interviewed system and civil engineers involved with performing the inspections and conducted detailed system walkdowns. The team was concerned that the applicant had established an inspection frequency that was not consistent with the frequencies specified in American Concrete Institute 349.3R-96 and the GALL Report. These standards specified that structures exposed to the elements and inside primary containment should be inspected every5 years and that interior structures should be inspected every 10 years. The applicant\'s Structural Monitoring program specified evaluating a representative sample of structures, systems, and components at each of the three units, such that the equivalent of one complete unit is inspected every 10 years. Based on this process, all areas in the three units will have undergone 100 percent inspection once in a 30-year period. The basis for this frequency was documented in procedure 81 DP-OZZ01, Civil System and Component Monitoring Program, which stated that the relative age of the structures at the time of the Maintenance Rule program implementation, the benign environment associated with the site, and having three identical units allowed for an extended inspection frequency. The team was concerned that the licensee had not completed a complete inspection of these structures to use as a basis for justifying an extended inspection schedule. The team noted that the NRC aging management program audit had raised similar questions in Request for Additional information 82.1.32-1. The applicant planned to evaluate whether they should have performed a complete baseline inspection of the facility structures, as documented in Condition Report Disposition Record 3441953.in response to the team\'s concern, the applicant provided a supplemental response to Request for Additional Information B2.1.32-1, as documented in License Renewal Application Amendment 13, dated April 1, 2010. The applicant revised Commitment 34in Table A.4-1, License Renewal Commitments, to state that prior to the period of extended operation, the Palo Verde Structures Monitoring program will be enhanced to inspect structures within the scope of license renewal at 1O-year intervals. The team concluded that the applicant had provided an appropriate response for internal structures, excluding primary containment. However, the team continued to have concerns with the applicant\'s assessment regarding external structures and structures inside containment. The applicant planned to supplement their response to Request for Additional Information B2.1.32-1 to provide a detailed technical justification for the inspection interval for structures inside primary containment or exposed to a natural environment, including all environmental factors. Because additional information is needed to determine whether the applicant had established an appropriate program to manage the effects of aging for the condition of external structures and containment internal structures during the period of extended operation, this is an unresolved item: Unresolved Item 05000528,05000529,05000530/2010007-02, Structures monitoring frequency and scope. For the Structures Monitoring program, the team determined that, with the exception of(1) issues related structural monitoring periodicity and methodology and (2) the limited completion of condition monitoring structural inspections to date, the applicant had implemented and performed appropriate evaluations of structures. Further, the applicant had considered pertinent industry experience and plant operating history to determine the effects of aging on plant structures and structural commodities. The team concluded that, if implemented as described and following resolution of the above concerns, the applicant will have provided adequate guidance to identify and address aging effects during the period of extended operation |