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IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making
DiabloDiablo Canyon NPPCanyon NPPProbabilistic Risk Assessment ProgramProbabilistic Risk Assessment Program
Workshop InformationWorkshop InformationIAEA WorkshopIAEA Workshop City , Country
XX - XX Month, YearCity , Country
XX - XX Month, Year
LecturerLesson IV 3_11.2
LecturerLesson IV 3_11.2
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 2
Risk Management and ItRisk Management and It’’s Applications Applicationat at Diablo Canyon NPP (DCPP) Diablo Canyon NPP (DCPP)
A process that evaluates the change in risk as a result of plant
changes in hardware, configuration, commitments,
processes, activities, and human and equipment performance.
The process uses risk- and performance-based methods as
opposed to traditional prescriptive methods.
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 3
Risk ManagementRisk Management
Motivation
US NRC plans to expand the use of PSA
Assessing changes to licensing basis
Assessing significance of findings
Enhance safety via systematic/integrated process
Reduce production interruption
Reduce operational cost
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 4
Definition of RulesDefinition of RulesPrescriptivePrescriptive--Based RulesBased Rules
These are rules that are based on arbitrary/judgmental assumptioThese are rules that are based on arbitrary/judgmental assumptions ns taken to assesstaken to assess adequacy of adequacy of plantplant response to certain bounding initiators. These arbitrary assumpresponse to certain bounding initiators. These arbitrary assumptions are often conservative tions are often conservative to account for the knowledge and model uncertainties. For examplto account for the knowledge and model uncertainties. For example, single failure criteria is a e, single failure criteria is a prescriptive rule which attempts to address the uncertainty abouprescriptive rule which attempts to address the uncertainty about equipment t equipment unavailabilityunavailability by by forcing at least two success paths for each function. forcing at least two success paths for each function.
DeterministicDeterministic--Based RulesBased RulesThese are rules which are purely based on the deterministic analThese are rules which are purely based on the deterministic analysis. For example, the amount ysis. For example, the amount of water required in the RWST for a PWR is usually based on the of water required in the RWST for a PWR is usually based on the amount of water that is amount of water that is required to allow for recirculation via the sump. And the amounrequired to allow for recirculation via the sump. And the amount of water is calculated based on t of water is calculated based on mechanistic calculationsmechanistic calculations..
ProbabilisticProbabilistic--Based RulesBased RulesThese are rules that are based on These are rules that are based on
probabilistic evaluation of the frequency of all possible initiaprobabilistic evaluation of the frequency of all possible initiatorstors
ANDAND
combination of deterministic and probabilistic evaluation of acccombination of deterministic and probabilistic evaluation of accident mitigating functions ident mitigating functions response to each (class of) initiators. response to each (class of) initiators. TheThe uncertainty in these rules can be statistically uncertainty in these rules can be statistically addressed. Defenseaddressed. Defense--inin--depth is an important consideration when implementing such rulesdepth is an important consideration when implementing such rules. .
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 5
Long Term Seismic Plan PSA in 1988 Long Term Seismic Plan PSA in 1988
LTSP is a full scope at power Level 1 PSA including External EveLTSP is a full scope at power Level 1 PSA including External Events nts
NRC staff issues SER on the NRC staff issues SER on the DCPPDCPP Level 1 PSA (NUREG/CRLevel 1 PSA (NUREG/CR--5726)5726)
DCPP IPE per Generic Letter 88DCPP IPE per Generic Letter 88--20 (Included Level 2 PSA) in 199120 (Included Level 2 PSA) in 1991
DCPP IPEEE model (Update of External Events) in 1993DCPP IPEEE model (Update of External Events) in 1993
Living PSA program including updates in 1995, 1997, and 2001 Living PSA program including updates in 1995, 1997, and 2001
DiabloDiablo Canyon Canyon NPP PSA ProgramNPP PSA ProgramProgram HistoryProgram History
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 6
Diablo Canyon Power Plant Diablo Canyon Power Plant PsaPsa ProgramProgram
PSA APPLICATIONS IMPLEMENTEDPSA APPLICATIONS IMPLEMENTEDMaintenance RuleMaintenance RuleConfiguration Risk Assessment (OnConfiguration Risk Assessment (On--line Maintenance)line Maintenance)Technical Specification OptimizationTechnical Specification OptimizationSevere Accident Management ProgramSevere Accident Management ProgramGeneration/Engineering SupportGeneration/Engineering SupportRiskRisk--Informed Informed InserviceInservice InspectionInspectionMotor Operated ValvesMotor Operated Valves
DCPP RISK MODEL PROGRAMDCPP RISK MODEL PROGRAMConfiguration Control ProgramConfiguration Control ProgramRiskRisk--Informed Application Projects Informed Application Projects PSA Model EnhancementsPSA Model Enhancements
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 7
Diablo Canyon Power Plant Risk Management Diablo Canyon Power Plant Risk Management ProgramProgram
Elements of Risk Management Program
Probabilistic Safety Assessment (PSA) information
PSA configuration controlPSA applications
Identification of safety enhancing/burden reducing applications
Risk significance evaluation
Expert panel & working groups
Post review of maintenance activities (risk curves)
Shutdown risk evaluation (ORAM Calculations)
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 8
Diablo Canyon Power Plant PSA Program Diablo Canyon Power Plant PSA Program Major Elements of PSA Configuration ControlMajor Elements of PSA Configuration Control
PSA configuration control procedure PSA configuration control procedure
PSA risk ranking procedurePSA risk ranking procedure
PSA risk assessment guidelinesPSA risk assessment guidelines
Periodic review of plant hardware and procedural changesPeriodic review of plant hardware and procedural changes
Periodic update of PSA Model subPeriodic update of PSA Model sub--modelsmodels
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 9
Diablo Canyon Power Plant PSA ProgramDiablo Canyon Power Plant PSA ProgramRisk Model Configuration Control ElementRisk Model Configuration Control Element
sequencing, Thermohydraulic
PSA INPUT &
FEEDBACK PATHS
System DesignChange -
Generic IndustryData - industry
system/equipmentfailure rates
Vendor Manuals -equipment operatingfeatures, failure modes
Design BasisDocuments -
system design basis,success criteria
FSAR - system designbasis, assumptions, successcriteria, Failure Modes and
Effects Analysis
TechnicalSpecifications -
allowed outage times,surveillance test
intervals
Plant OperatingProcedures - Normal
system alignments
Emergency OperatingProcedures - Accident
condition alignments, operatorrecovery actions
SurveillanceProcedures
system alignmentfor testing
MaintenanceProcedures - system
alignment formaintenance
EngineeringProcedures -other testing
Engineering Analysis -Room Heat-up Calcs,
Accident progression and
evaluations
Performance Data -plant specific system/
equipment failure rates,Maintenance Datafrequency/duration
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 10
DiabloDiablo Canyon Power Plant PSA ProgramCanyon Power Plant PSA ProgramRisk Insights ElementRisk Insights Element
Contributions to CDF by Initiator
24%
23%18%
11% 4%
1%
2%
17%
Loss of ASW or CCW (24%)Floods (23%)Loss of Offsite Power (18%)General Transients (Rx Trip, Turb Trip, etc.) (17%)LOCAs (Excessive, Large, Medium, Small, RCP Seal) (11%)Steam Generator Tube Rupture (4%)Interfacing System LOCAs (2%)Loss of One 125V DC Bus (1%)
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 11
DiabloDiablo Canyon Power Plant PSA ProgramCanyon Power Plant PSA ProgramRisk Insights ElementRisk Insights Element
Contributions to LERF by Initiator
66%
32%
2%
Steam Generator Tube Rupture (66%)Interfacing System LOCAs (32%)Other (2%)
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 12
IMPORTANT OPERATOR RECOVERY ACTIONSIsolate Ruptured Steam Generator
Reduce Unnecessary CCW Loads
Align Firewater as Backup Cooling to CCPs
480V Switchgear Vent (Reduce IY & BTC Room Temps)
Electric Power (offsite power, vital bus crosstie, DG)
Switchover to Cold Leg Recirculation
Initiation of Feed and Bleed Cooling
Trip RHR Pumps Following Small Break LOCA
TOP 10 SYSTEMS (RRW for Internal Events)
Auxiliary SaltwaterDiesel Generators
Component Cooling WaterRCS (PORVs & Seal LOCA)
Vital AC PowerResidual Heat RemovalNon-Vital Electric Power
Charging & SIAuxiliary Feedwater
Vital DC Power
DiabloDiablo Canyon Power Plant PSA ProgramCanyon Power Plant PSA ProgramRisk Insights ElementRisk Insights Element
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 13
DiabloDiablo Canyon Power Plant PSA ProgramCanyon Power Plant PSA ProgramRisk Insights ElementRisk Insights Element
Blends prescriptive and deterministic/probabilistic insights
Considers factors outside the scope of PSA analyses
Evaluates aggregate affects of all risk informed, performance based programs
Provides an overall sanity check
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 14
DiabloDiablo Canyon Power PlantCanyon Power PlantExpert Panel Members and ResponsibilitiesExpert Panel Members and Responsibilities
MEMBERSOperations- Licensed SRORisk and Reliability Supervisor (Chairperson)System Engineering SupervisorPreventative Maintenance Program Specialist
RESPONSIBILITIES1. Approve the criteria for assessing the risk significance of SSCs.2. Review and approve the risk significance assigned to SSCs.3. Maintain cognizance over the implementation of the Risk Management
Program and other risk-informed initiatives. 4. Adjust criteria for risk-informed programs as appropriate.
IAEA Training Course on Safety Assessment of NPPs to Assist Decision Making 15
Diablo Canyon Power Plant PSA ProgramDiablo Canyon Power Plant PSA ProgramConclusionConclusion
ESSENTIAL ELEMENTS
Probabilistic Safety Assessment (PSA)
Deterministic insights
Expert Panel
Risk-Informed working group
Continuous performance feedback
Implementation strategies