IAEA Training Course on Safety Assessment of NPPs to Assist …€¦ · at Cofrentes NPP IAEA...
Transcript of IAEA Training Course on Safety Assessment of NPPs to Assist …€¦ · at Cofrentes NPP IAEA...
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RiskRisk--informed Oninformed On--Line MaintenanceLine Maintenanceat Cofrentes NPPat Cofrentes NPP
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making
Workshop InformationWorkshop InformationIAEA WorkshopIAEA Workshop City , Country
XX - XX Month, YearCity , Country
XX - XX Month, Year
LecturerLesson IV 3_11.12
LecturerLesson IV 3_11.12
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IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 1
ObjectivesObjectives– To maintain and improve safety through:
• Negligible unavailability increase and configuration risk control due to simultaneous unavailability of systems.
• System reliability improvement by:Better scheduling of tasks.Use of most qualified people.Better control of results.
– To reduce maintenance costs:• Better schedule less unavailability time.• Reliability improve reduction in corrective maintenance.• Reduction on maintenance tasks during outages.• Potential reduction in outage time.
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Starting PointStarting Point
– Traditionally, maintenance tasks done at power over systems controlled by Technical Specifications were just:
• Corrective maintenance.
• Surveillance testing.
• Short maintenance tasks due to manufacturer recommendations or operating experience.
– During outages great amount of tasks.
• High unavailability during outages. Some systems could have bigger safety importance during outage than during power operation.
– To delay some maintenance tasks gives reliability get worse.
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Preventive Maintenance DefinitionPreventive Maintenance Definition
– A task should be consider inside this program if all these three condition are given:
• Plant is at operating Mode 1.
• System, equipment or component to maintain is controlled by Technical Specifications.
• Maintenance execution gives to a voluntary entry in aLCO.
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LimitationsLimitations
– Just one entry in each LCO.
– Just one entry each year by system.
– Preventive maintenance time: should be less than 60% of LCO limit.
– Time given by LCO should be more than 72 hours.
– No simultaneous works on more than one frontal system.
– No scheduled changes on plant operating mode during works.
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Current Scope of the ProgramCurrent Scope of the Program• E12 - Residual Heat Remove System A and B.• E12-C - Low Pressure Core Injection, train C.• E21 - Low Pressure Core Spray.• P38 -Standby Gas Treatment System Trains A and B.• P54 - Essential Compressed Air A and B.• T52 - Drywell /Containment mixing Air System.• T27/F42 - Transferring Tube /Fuel Upper Pool.• XG3 - Control Room HVAC, trains A and B.• P64 - Fire Protection System.• E32 - Main Steam Isolation Valves Leakage Control System.
– In the near future:• R43 - Diesel Generators.
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Feasibility StudyFeasibility Study– Scope (for each system):
• Tech specs affected.
• Safety functions affected.
• Deterministic and probabilistic (PSA) assessment of associated unavailability.
• Alternative systems to fulfil safety function(s) affected. Operability requirements.
• Simultaneous system unoperabilities forbidden, because of tech specs or because of causing high risk.
• Confirmation that trip probability is not increased, and review of ALARA criteria.
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Risk Limits of the ProgramRisk Limits of the Program– The risk limits are obtained from RG 1.174 and
NUMARC 93-01.– RG 1.174 gives the limits in the general implementation of
the program.
1E-05
1E-06
Region I -Forbidden change
Region II - Look for accumulated changes
Region III - Change should be accepted
CDF 1E-05 1E-04
ΔCDF
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Risk Limits of the Program (II)Risk Limits of the Program (II)
– NUMARC 93-01 gives the limit that apply to an specific configuration.
– None configuration should produce CDF greater than 1E-3/year.
– For any entry in the program, DCDP should be:
ΔCDP Considerations>1E-05 Do not enter voluntarily
1E-6 –1E-5
- Assess not quantifiable factors- Establish Risk Management Actions
<1E-6 Normal Work Controls
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Execution ProcedureExecution Procedure
– An specific plant procedure has been developed for the execution of on-line maintenance, in order to guarantee:• Responsibilities.
• Feasibility study existence.
• Plant configuration analysed (pre-requirements of operability of systems are fulfilled).
• Compensatory measures, if have been defined, has been taken .
• Task schedule is detailed and feasible. Spare parts are available and training have been done.
• It is not expected a change in the operating mode.
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Risk MonitorRisk Monitor
– A risk monitor based on PSA models analyse scheduled works (maintenance): temporary risk.
– It is also used when clearance are authorised (use by operators), because the case that plant situation is not the expected.
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Training to Maintenance PeopleTraining to Maintenance People
– Before the execution of the tasks people involved are trained, including:
• Function(s) of the system.
• Safety importance of the system, Technical Specifications and PSA.
• Importance of the works in plant objectives.
• Responsibility of the tasks.
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Results of the Program (1/2)Results of the Program (1/2)
– Program makes operators and schedulers work together with PSA, giving everybody a global vision of the problems associated with the running of the plant.
– Risk concept is introduced in the organisation, improving safety culture.
– Pre-working training gives a better people motivation, adding responsibility and involving in plant objectives
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– Detailed schedule of tasks gives that all organisation are involved in the execution of the tasks, comparing with a higher difumination during outages.
– Moving works from outages gives to safer and more simple outages.
– Tasks are done in less time and with more efficiency by own personnel.
– Due to a better global maintenance, reliability is improved and so safety.
Results of the Program (2/2)Results of the Program (2/2)