ML18115A163

Draft Response on RBS LRA RAI B.1.21-2 Flow Accelerated Corrosion

ML18115A163
Person / Time
Site:	River Bend
Issue date:	04/25/2018
From:	Wong A NRC/NRR/DMLR/MRPB
To:
Wong A, NRR-DMLR 415-3081
References
Download: ML18115A163 (3)

Text

DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONPage1 of3QuestionRAI B.1.21-2 (Flow-Accelerated Corrosion)BackgroundFor the "detection of aging effects" program element, Section 4.8 of RBS EP 15 00007 cites procedure EN-DC-315, "Flow-Accelerated Corrosion [FAC] Program," as the basis for being consistent with the GALL ReportAMP XI.M17. Procedure EN-DC-315 states that specific software programs (i.e., "CHECWORKS" and "FACManager Web Edition") shall be used in determining the remaining component life. Based on discussionsduring the AMP Audit breakout session, both software programs are classified as Level C, which does notrequire verification/validation activities. GALL Report AMP XI.M17 states that the FAC program is described inNSAC-202L and that components are suitable for continued service if the predicted wall thickness at the nextscheduled inspection is greater than or equal to the minimum allowable wall thickness. NSAC-202L, Section 2,"Elements of an Effective FAC Program," provides recommendations for ensuring that appropriate qualityassurance is applied, including properly documenting work. Entergy report EC-0000072133, "RF-19 Post-Outage Report," includes a signed output sheet from FAC Manager, which contains wall thickness data andthe measured wear rate from each inspection.IssueFor safety-related components, it is not clear to the staff that the remaining component life is being properlydetermined because the wear rate values are taken from Level C software (i.e., "CHECWORKS" and "FACManager Web Edition"), which does not require validation and verification activities. Although the FACManager output sheets are signed as prepared and verified, the determination of the wear rate values cannotbe independently verified based on the information provided.RequestProvide additional information to show that appropriate quality assurance has been applied to the calculatedwear rates used in the determination of the schedule for inspection of safety-related components.ResponseNote: A previous response to RAI B.1.21-2 was submitted in letter RBG-47834, dated March 8, 2018.The following response is the same as the response in letter RBG-47834 except additional informationregarding software validation has been provided in the 3rd paragraph below. The following responsesupersedes the previous response submitted in letter RBG-47834.CHECWORKS and FAC Manager Web Edition (FMWE) are Level C software which is used for day-to-daysupport activities and whose loss or failure would not affect the immediate ability to operate the plant but couldthreaten the plant's long-term ability to operate. The Level C classification is appropriate because the softwareis not embedded in or integral to a safety-related (SR) structure, system or component (SSC), is not utilized inthe design process of SR SSCs, is not embedded in or an integral part of a non-safety related (NSR) SSCused to support or maintain an important to safety SSC (e.g. surveillance, calibration, post-maintenance test),is not used to determine Technical Specification, NRC regulation/commitments or 10CFR50 compliance, and is DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONPage2 of3not used to calibrate or maintain maintenance and test equipment (M&TE) used on safety-related or TechnicalSpecification SSCs.Level C software does not require "verification," which consists of evaluating and analyzing products of eachlife cycle phase (e.g., requirements specification, design descriptions, code, and databases) through testingand reviews or audits to discover and correct deficiencies as early as possible. However, the CHECWORKScode was developed in accordance with the quality assurance policies of EPRI, which require a formalsoftware plan and detailed program documentation. These policies also mandate that a list of program bugs bemaintained. The FMWE code was developed in accordance with the quality assurance policies of Altran, whichalso require a formal testing plan, detailed program documentation, and a list of program bugs.Level C software does require "validation," which is the final testing activity and ensures that the softwareinstallation and integration into the production environment is successful. The installation is performed inaccordance with a documented plan or vendor instructions which may include sample program inputs andoutputs for use in verifying installation. In accordance with the Entergy software quality assurance procedure,each time CHECWORKS or FMWE is revised, FAC personnel validate the revised software using test casesand test databases before the software is placed in production mode. The validation tests provide theappropriate quality assurance to ensure that component wear, wear rate, predicted thickness, and remainingservice life are calculated consistently with NSAC-202L.Predictive model CHECWORKS is just one of the tools used to determine inspection eligibility and priority.Selection of inspection locations for an outage is based on the following factors.previous inspection resultsCHECWORKS susceptibility rankingindustry and plant-specific operating experiencecomponents selected to calibrate CHECWORKScomponents subject to off normal flow conditions, such as caused by a leaking valvesusceptible non-modeled small bore piping that has not been inspectedMeasurement of actual wall thickness during inspections is the primary tool used in the FAC Program todetermine component wear. The measured wall thickness is used to determine wear rates, predictedthickness, and remaining service life in FAC Manager Web Edition (FMWE) according to the following steps.Initial thickness of a component is determined by ultrasonic inspection prior to the component beingplaced in service or in the first ultrasonic inspection during its service life. If an examination has notpreviously been performed on the component, the initial thickness is determined by reviewing the initialultrasonic data for that component. The area of maximum wall thickness within the same region as theworn area is identified. If the thickness is greater than the nominal component wall thickness, themaximum wall thickness within the relevant area is used as the initial thickness. If that thickness is lessthan the nominal wall thickness, the nominal wall thickness is used as the initial thickness.The projected wear rate is calculated by dividing the wear by the time between measurements or thetime between when the component was placed in service and the time of the measurement. Wear isthe amount of material removed or lost from a components wall thickness since baseline or subsequentto being placed in service and time is theactual plant operating hours, although calendar hours may beused for conservatism.

DRAFT - UNCERTIFIED INFORMATIONDRAFT - UNCERTIFIED INFORMATIONPage3 of3The remaining service life (RSL) is determined by subtracting the minimum acceptable wall thicknessfrom the actual measured wall thickness, then dividing by the wear rate times a safety factor of 1.1.If the RSL of a component is greater than or equal to the number of hours in the next operating cycle,the component may be returned to service.If the component's RSL is greater than the number of hoursin the next operating cycle but is less than the number of hours in the next two operating cycles, thecomponent should be considered for re-inspection, repair or replacement during the next scheduledoutage. If the component is acceptable for continued service, it shall be re-examined before, or duringthe cycle during which it is projected to wear to the minimum acceptable wall thickness.Evaluation of wear rates, predicted thickness, and remaining service life is documented and reviewed byqualified FAC personnel or designated personnel qualified in accordance with the engineering calculationprocess. Therefore, appropriate quality assurance is applied to the calculated wear rates used in thedetermination of the schedule for inspection of safety-related components.