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Safety Performance Indicators Improving Nuclear Safety through Operating Experience

Safety Performance Indicators Improving Nuclear Safety through Operating Experience. Cologne 29-31 May 2006 Lennart Carlsson. SPI:s in the context of operating experience. CNRA/CSNI Task Force on Safety Performance Indicators Overview of results Interpretation of changes in performance

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Safety Performance Indicators Improving Nuclear Safety through Operating Experience

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  1. Safety Performance IndicatorsImproving Nuclear Safety through Operating Experience Cologne 29-31 May 2006 Lennart Carlsson "OH-seriens namn"

  2. SPI:s in the context of operating experience CNRA/CSNI Task Force on Safety Performance Indicators Overview of results Interpretation of changes in performance Some personal views "OH-seriens namn"

  3. Report outline – Areas covered 3.1 THE NEEDS OF REGULATORS • 3.2 The influence of regulatory policy and framework in use of SPI • 3.3 Desirable attributes of an SPI system • 3.4 How SPI systems have been established • 3.5 Coverage of safety areas or cornerstones by SPI systems • 3.6 How regulators collect and process data • 3.7 Indicators of SM, SC and attitude towards safety • 3.8 PSA-related indicators • 3.9 Role of SPIs in improving and demonstrating regulatory effectiveness "OH-seriens namn"

  4. Regulators need • To measure the safety performance • To improve their own regulatory activities • To communicate about the safety of NPP • To measure their own efficiency and effectiveness • To compare safety performance with similar plants "OH-seriens namn"

  5. Reglatory policy and framework Role of SPIs in regulatory oversight – measuring safety performance Role of SPIs in focusing regulatory activities Role of SPIs in communicating with stakeholders Use of indicators for international benchmarking "OH-seriens namn"

  6. Integrated Safety Assessment Safety Review • Indicators Inspections Event analysis and operational feed-back Plant Surveillance Investigations and Research Comprehensive Integrated Safety Assessment Notification of Plant Modification Experience and skills of SKI-staff for example international co-operation SKI opinion on Safety Status RUS PSR Planning and budgeting/ Prioritisation SKI-Forum "OH-seriens namn"

  7. Desirable attributes • A clear defined, logical relationship to the safety regulators goals and objectives • The definition of indicators should be clear and precise • Resistive to manipulation, misuse or misunderstanding • At least some of the SPIs should lead to timely indications of safety degradation • (reveal latent deficiencies) "OH-seriens namn"

  8. Coverage of safety areas orcornerstones by SPIs • Similar SPIs may arise independently of a chosen hierarchy • It could be strategic level or operational • Comparison of cornerstones and IAEA Tecdoc 1141 structure • The comparison is straightforward and a few areas seem not to be included in the Tecdoc structure eg. Physical protection and investments • About 17 indicators (recogn. diff. definitions) commonly used "OH-seriens namn"

  9. Evolution • Earlier work identified 6 common indicators (among 6 or more RB in 2000), • The development goes very fast at the RB • In June 2005 it was 14 • In December 2005 it was17 in common "OH-seriens namn"

  10. Some common regulatory SPIsfor at least 6 RBs / 18 Events: • Unplanned scrams/ RPS actuations • Safety system actuations • Safety significant events/reportable events • Unplanned power changes Mitigating systems: • Safety system unavailability • Safety system failures (loss of redundancy) Barrier integrity: • Fuel cladding/reliability • RCS/pressure boundary leakage • Drywell/ Primary Containment/Hermetic zone tightness "OH-seriens namn"

  11. Some common regulatory SPIsfor at least 6 RBs / 18 Radiation Safety Occupational and public radiation safety: • Radiation exposure to workers - Collective dose Public Radiation Safety • Public dose • Liquid releases • Gaseous/air born releases "OH-seriens namn"

  12. Common indicators 17 Safety Management/ Safety related processes Human performance • Events due to human and organizational failure Compliance / Attitude • Number of TS violations/non compliance • Number of TS exemptions (temporary changes) Emergency preparedness • Drill participation / training on emergency response "OH-seriens namn"

  13. How regulators collect and processdata • Data collection and calculation of indicators • Thresholds and trends • Use of colour codes • Aggregation of indicators • Review of SPI system "OH-seriens namn"

  14. Cautions (1) • SPIs may not be resistant to temptation of manipulation • The possibility to manage the indicators rather than safety • Regulators should be aware of the dangers of reacting to small changes in SPIs or any changes in those SPIs that have a high scatter as a result of small samples e.g. counting small numbers of events "OH-seriens namn"

  15. Cautions (2) • Should be constructed with a specific objective in mind • Indicator systems may have to be tailored for multiple purpose • Time-lag between decline in performance and change in value of an SPI • International comparison • Aggregation has to be made with care – opposite trends • Colour codes may cause confusion amongst people not fully familiar with their meaning "OH-seriens namn"

  16. SKI’s safety performance indicator system started in 1999 and includes: • Industry - WANO’s indicators (8) • Indicators based on LERs: • MTO-related SPI • System unavailability • SPI based on work orders (pilot study) • Additional indicators under development • Emergency preparedness • Physical protection • Fires, etc "OH-seriens namn"

  17. Indicators based on LERsMTO-related SPI • MTO-related SPI are based on the evaluation of: • MTO-database (Man-Technology-Organisation) • Work Order system at one unit (pilot study) • The MTO-db contains, since 1994, the MTO-relatedLERs and Scrams for all Swedish units • Strategic SPI relate to the causal categories of theMTO-db, and specific SPI relate to the root causes "OH-seriens namn"

  18. Plant A – Strategic safety performance indicators , , : 1, 2 resp. 3 or more LERs/quarter/unit for the indicator "OH-seriens namn"

  19. Indicators based on LERsSPI -System unavailability SKI monitors, following the defence-in-depth philosophy, the unavailability of 31 systems • Level 2 - Control & protection systems (8) • Level 3 - Safety systems (6) • Level 3 - Separation barriers (7) • Level 4 - Surveillance & monitoring systems (8) • Level 4 - Consequence mitigating systems (2) System unavailability is calculated from the LERs "OH-seriens namn"

  20. Calculation of the system unavailability Qsys tsys = Unavailable hours (depends on component) T = Time for critical reactor or calendar time n = Number of subdivisions/redundant components fsys = Constant, 0 or 1, indicating the influence on the system of a component unavailability fcredit = Constant (0,1 or 0,01) indicating the possibility forfast, simpler & supported corrective actions tsysT x n x fsys x fcredit Qsys = "OH-seriens namn"

  21. SPI – ECCS unavailability (2001 – 2003)Level 3: Control of conditions during DBA "OH-seriens namn"

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