Safety Performance Indicators Improving Nuclear Safety through Operating Experience

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Safety Performance Indicators

Improving Nuclear Safety through Operating Experience

Cologne 29-31 May 2006 Lennart Carlsson

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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

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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

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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

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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

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Integrated Safety Assessment

Comprehensive

Integrated Safety

Assessment

Plant Surveillance

InspectionsSafety Review

Event analysis andoperational feed-back

Investigations andResearch

Notification ofPlant Modification

PSR

RUS

Experience and skills of SKI-staff for exampleinternational co-operation

SKI opinion

on Safety Status

Planning and budgeting/Prioritisation

Indicators

SKI-Forum

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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)

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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

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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

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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

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Some common regulatory SPIsfor at least 6 RBs / 18

Radiation SafetyOccupational and public radiation safety: Radiation exposure to workers - Collective dose

Public Radiation Safety Public dose Liquid releases Gaseous/air born releases

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Common indicators 17Safety Management/ Safety related processesHuman 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

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How regulators collect and process

data Data collection and calculation of indicators Thresholds and trends Use of colour codes Aggregation of indicators Review of SPI system

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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

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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

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SKI’s safety performance indicator system

started in 1999 and includes:• Industry - WANO’s indicators (8)• Indicators based on LERs:MTO-related SPISystem unavailabilitySPI based on work orders (pilot study)

• Additional indicators under developmentEmergency preparednessPhysical protectionFires, etc

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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-related LERs and Scrams for all Swedish units

• Strategic SPI relate to the causal categories of the MTO-db, and specific SPI relate to the root causes

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Plant A – Strategic safety performance indicators

, , : 1, 2 resp. 3 or more LERs/quarter/unit for the indicator

Indicator 2001 2002 2003

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Sum

Number of MTO-LER 8 7 5 6 9 10 13 9 7 13 20 12 119

Company mgt & plant org. 46

Work organisation 33

Change management 16

Supervisory methods 30

Work practices 71

Communication 16

Instruction / Documentation 26

Training / Competence 29

Ergonomics / Design 20

Work schedule 3

Work environment 0

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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

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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 for fast, simpler & supported corrective actions

Qsys = tsysT x n

x fsys x fcredit

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SPI – ECCS unavailability (2001 – 2003)Level 3: Control of conditions during DBA

System Unit

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4LPIS B2 3,9 E-4 1,1 E-3

LPIS F1 1,7 E-2 1,3 E-2

LPIS F2 1,3 E-2 1,0 E-3

LPIS F3

LPIS O1

LPIS O2 3,2 E-2

LPIS O3 4,7 E-2

LPIS R1 9,8 E-2 1,2 E-2 7,0 E-4 3,6 E-2 5,1 E-2

SI R2 1,6 E-4 2,6 E-3 3,8 E-2 4,5 E-2 3,3 E-3 2,9 E-3 4,5 E-2 3,8 E-2

SI R3 1,7 E-1

SI R4 8,9 E-5 6,5 E-3 8,9 E-3

<0,010,1-0,01>0,1

20032001 2002Safety systems