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S U MM ARY

LESSONS LEARNED FROM AGING MANAGEMENT ACTIVITIES MODERNISATION OF THE WWER 440 UNITS CONSIDERING ASPECTS OF THE LTO J.ZDAREK, P.KADECKA. S U MM ARY.

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S U MM ARY

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  1. LESSONS LEARNED FROM AGING MANAGEMENT ACTIVITIESMODERNISATION OF THE WWER 440 UNITS CONSIDERING ASPECTS OF THE LTOJ.ZDAREK, P.KADECKA

  2. SUMMARY Existing NPPs are secure source of energy. Their Long Term Operation is strategic goal for any utility. The US License Renewal process is closely followed by the IAEA activity and WWER operating countries. Recent lessons learned from several Aging Management Programmes (US, IAEA, WWER) will be summarized.

  3. INTEGRATED PLANT REVIEW Scope Screen Aging Mgmt. Review Passive or Active? • Systems, components, • and structures within • the scope of • 10CFR54: • Safety-Related • Non-Safety Related • that could prevent • safety function • Regulated Events – • SBO, EQ, Fire, • PTS, ATWS • SCOPE Passive Periodically Replaced? No Active Managed by existing activities? Aging Management Review No Yes Modify existing or add new programs Yes Structures & Components not subject to Additional Aging Management Review Demonstration that the effects of aging are adequately managed

  4. RPV • RPV internals • pressurizer • main coolant pump • main coolant loop • auxiliary primary piping • containment • electrical containment penetration • large openings in the containment • nuclear civil engineering structures • cables • I&C 12 DETAILED AGING ANALYSIS

  5. THE LTO DATABASE • Together 6000 SSCs divided to 60 LTO groups • It is not possible to provide assessment for all selected 6000 SSCs • Based on engineering judgement and operation experience 215 type groups defined • For the type groups detailed assessment and conclusions prepared

  6. KEY RECOMMENDATIONS FROM THE NPP • For the type groups where replacement of the SSCs is standard practice without large cost is proposed to cancel them from the LTO database. About 25 out of 215 type groups. • In the assessment to account for existing changes of material, including all means to prevent different damage mechanisms e.g. corrosion

  7. FIRST SET OF REQUIREMENTS FROM THE NPP • To assure enough spare parts or new components in case that regular replacement is possible • In all high damage exposed places to accomplish material replacement with higher damage resistance • On all components with higher degradation occurrence to increase maintenance and testing requirements

  8. DB Collation Equipment Qualification PTS/WPS P/T curves Civil structures SG monitoring Sealing Programme UT/EC Qualification RI ISI Cable monitoring LIST OF PROGRAMMESWITH INPUT TO MODERNISATION

  9. DB COLLATION • Detail knowledge of the DB Requirements and DB Parameters will assure correct modernization programme • The configuration management programme requires to have DB data • The License Renewal for the LTO also requires the DB Collation

  10. EQ • Qualification status for about 2200 equipment per unit within EQ list is established • All equipment from the EQ list is classified in following categories • Qualified • Qualified if specified conditions are fulfilled • Nonqualified • Modernization Programme has to assure qualified categories within EQ list as principle requirement for the LTO

  11. PRIMARY SIDE FAILURES DOMINATE PTS RISK We need PTS conclusion for WWER. Presented conclusion is for US PWRs. • Primary side failures dominate • Low embrittlement: stuck open valves that later re-close • Higher embrittlement: medium & large diameter pipe breaks • Secondary • main steam line breaks • stuck open valves of much smaller consequence, & only at extremely high embrittlement levels

  12. P-T CURVES • 2 types of p-T curves created for NPP Dukovany: • for constant temperature (serving for protection against low-temperature-over- pressurisation) • for step cool down (serving for protection against PTS) • Westinghouse methodology applied • New set of p-T curves generated in 2005 for underclad cracks with depth 15 mm

  13. CIVIL STRUCTURES Ageing management programme and monitoring shall be applied on the following components of NPP structures • soil – structure interaction • design, construction and performance of: • basemat • vertical concrete constructions (shrinkage, creep) • ceilings • roofs • ways • operation mode of NPP • preventive and corrective maintenance • influence of components modernization

  14. On-line / periodical Chemistry of feed water, blow down During shut down HOR (Hide out return) + MULTEQ = pH in crevices Outage NDT (Visual control, Eddy current.) Analyses of removed deposits, withdrawn tubes Statistical evaluation of new damage indications Database of chemical regimes and tube damage SG MONITORING Electrochemical Evaluation System + on-line information on crevice status ? + on-line solution sampling from crevice ?

  15. SEALING PROGRAMME • complex approach to seal assessment • serrated profile gaskets with pure-graphite facing MITesHT • applications: main circulation pump, steam generator • replace of nickel seals • low level of stress for leakage rate class • low torque • verification of seal parameters • great numbers of seal renovation

  16. UT/EC QUALIFICATION • NDT Qualification focused on UT/ET qualification of equipment, inspection procedures (IP) and additional personnel qualification • UT/ET qualification has to be completed for majority of inspection areas in 2006 (incl. PHARE ISI 2002) • In all above aspects Qualified inspections of Safety Significant and Safety Related inspection areas required • for extended inspection intervals • as principle requirement for the LTO • Missing: • additional personnel qualification (especially by blind tests) • verification and evidence by computer modelling (CIVA simulations) for early completed UT/ET qualifications • verification on realistic type defects for some qualifications

  17. RI ISI • Current Status: Verification of selected RI ISI approach/EPRI methodology for WWER type plants based on the following pilot studies: • LP ECCS at Temelin NPP (ETE) • Primary piping including pressuriser piping for Dukovany NPP • Steam and feed water piping (as High Energy piping) at ETE • Participation in a worldwide benchmark of RI ISI methodologies and verification on at least 4 selected systems at Ringhals NPP in 2006-2007 (RISMET) • Transition to commercial RI ISI applications after completion of RISMET project and in case of approval by SUJB as a requirement for the LTO • Verification of other risk/RI-ISI approaches: BER RI ISI, Streamlined RI ISI, RI Repair/Replacement

  18. CABLE MONITORING • Systematic cable ageing management programme is needed at all NPPs based on cable deposits, environmental monitoring, cable ageing monitoring and software system for cable life assessment. • Replacement of degraded cables. • Relocation of cables to avoid hot spots. • Modify environment to reduce severe conditions.

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