Introduction to risk approach in nuclear Introduction to risk approach in nuclear safety safety The role of PSA in safety management The role of PSA in safety management IAEA Training in level 1 PSA and PSA applications
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Introduction to risk approach in nuclear Introduction to risk approach in nuclear safetysafety
The role of PSA in safety managementThe role of PSA in safety management
IAEA Training in level 1 PSA and PSA applications
The role of PSA in safety management
Slide 2.
The lecture is intended to introduce and explain some important philosophical aspects of the safety management related to Probabilistic Safety Assessment:
the importance of the complementary application of the deterministic and probabilistic approaches,the role of the PSA in safety management
The lecture is intended to introduce and explain The lecture is intended to introduce and explain some important philosophical aspects of the safety some important philosophical aspects of the safety management related to Probabilistic Safety management related to Probabilistic Safety Assessment:Assessment:
the importance of the complementary application of the the importance of the complementary application of the deterministic and probabilistic approaches,deterministic and probabilistic approaches,the role of the PSA in safety managementthe role of the PSA in safety management
IntroductionIntroduction
The role of PSA in safety management
Slide 3.
ContentContent
Defence in Depth principleThe Role of the BarriersHow does PSA Represent the Barriers?
The Safety Management and the Nuclear Power PlantThe Probabilistic and Deterministic Approaches
How do they complement each other?
The PSA Applications and the Safety Management
Defence in Depth principleDefence in Depth principleThe Role of the BarriersThe Role of the BarriersHow does PSA Represent the Barriers?How does PSA Represent the Barriers?
The Safety Management and the Nuclear Power PlantThe Safety Management and the Nuclear Power PlantThe Probabilistic and Deterministic ApproachesThe Probabilistic and Deterministic Approaches
How do they complement each other?How do they complement each other?
The PSA Applications and the Safety Management The PSA Applications and the Safety Management
The role of PSA in safety management
Slide 4.
OverviewOverview
The PSA has an important role to complement the deterministic approach to safety design, operation and regulation of nuclear power plants with the risk approach.
It is provided by the diversity of the approaches:Success oriented design with some risk aspectsFailure oriented approach of PSA: answers to questions: What can go wrong?, How likely is it?
The PSA has an important role to The PSA has an important role to complement the deterministic approach to complement the deterministic approach to safety design, operation and regulation of safety design, operation and regulation of nuclear power plants with the risk approach.nuclear power plants with the risk approach.
It is provided by the diversity of the approaches:It is provided by the diversity of the approaches:Success oriented design with some risk aspectsSuccess oriented design with some risk aspectsFailure oriented approach of PSA: answers to Failure oriented approach of PSA: answers to questions: What can go wrong?, How likely is it?questions: What can go wrong?, How likely is it?
The role of PSA in safety management
Slide 5.
The Defence in Depth PrincipleThe Defence in Depth Principle
I.
II.
III.
IV.
Classical interpretation of the barriersClassical interpretation of the barriersPhysical barriersPhysical barriers
Abstract interpretation of the barriersAbstract interpretation of the barriersTechnological systemsTechnological systems
systems of normal operationsystems of normal operationsafety systemssafety systemsaccident localisation systemsaccident localisation systems
Administrative barriersAdministrative barriersoperating instructions, Tech.Spec. operating instructions, Tech.Spec. EOPEOP’’ssAccident Management ProceduresAccident Management Procedures
The role of PSA in safety management
Slide 6.
The Defence in Depth Principle (contThe Defence in Depth Principle (cont’’d)d)
Properties of the barriers:What is the barrier able to cope with? (height)
The design basis
Is it sure any time? (integrity)Reliability
Low frequency of attacks, being able to cope with wide spectrum of events and high barrier reliability give together safety.
=> use PSA to evaluate the effectiveness of the protection
Properties of the barriers:Properties of the barriers:What is the barrier able to cope with? (height)What is the barrier able to cope with? (height)
The design basis The design basis
Is it sure any time? (integrity)Is it sure any time? (integrity)ReliabilityReliability
Low frequency of attacks, being able to cope with Low frequency of attacks, being able to cope with wide spectrum of events and high barrier wide spectrum of events and high barrier reliability give together safetyreliability give together safety..
=>=> use PSA to evaluate the effectiveness of the use PSA to evaluate the effectiveness of the protectionprotection
The role of PSA in safety management
Slide 7.
The Safety Management and the Nuclear The Safety Management and the Nuclear Power Plant SafetyPower Plant Safety
Three group of mechanisms Three group of mechanisms and tools to provide high and tools to provide high level of safety:level of safety:
initial knowledgeinitial knowledgeDBADBA
feedforwardfeedforwardPSAPSAexperimentsexperiments
feedbackfeedbackevent investigationevent investigationinternal and external internal and external experience feedbackexperience feedback
Analysis ofpotential events
Analysis ofreal eventsPlant Safety
Initial safety analysis
Feed forward Feed back
Initial knowledge
after J. Villadóniga, Argonne, 1995
The role of PSA in safety management
Slide 8.
Probabilistic and Deterministic Probabilistic and Deterministic ApproachesApproachesProbabilistic and Deterministic Probabilistic and Deterministic ApproachesApproaches
The probabilistic and the deterministic The probabilistic and the deterministic approaches have the same approaches have the same objective: to find the objective: to find the safe regionsafe region in in the space of the possible plant the space of the possible plant states.states.
Which is better?Which is better?
The The complementary use complementary use of both is the of both is the best.best.
?
The role of PSA in safety management
Slide 9.
Probabilistic and Deterministic Probabilistic and Deterministic Approaches (contApproaches (cont’’d)d)
Which approach is better, the probabilistic, or the deterministic?
Both approaches look for the region in the possible plant states, where the operation of the nuclear power plant is thought to be safe enough
The objective of both approaches is the same. Thus, it is expected that both approaches find the same region
However, being different approaches, there are regions covered by one and not covered by the other one
Which, does not mean, that one is more strict or better, than the other
From the point of view of the safety the right answer is to use both approaches in order to optimize the region found safe enough by both methods i.e. the region with low risk fulfilling the deterministic requirements
That should be the principle of a modern risk based safety regulation
Which approach is better, the probabilistic, or the deterministiWhich approach is better, the probabilistic, or the deterministic?c?
Both approaches look for the region in the possible plant statesBoth approaches look for the region in the possible plant states, where , where the operation of the nuclear power plant is thought to be safe ethe operation of the nuclear power plant is thought to be safe enoughnough
The objective of both approaches is the same. Thus, it is expectThe objective of both approaches is the same. Thus, it is expected that ed that both approaches find the same regionboth approaches find the same region
However, being different approaches, there are regions covered bHowever, being different approaches, there are regions covered by one y one and not covered by the other oneand not covered by the other one
Which, does not mean, that one is more strict or better, than thWhich, does not mean, that one is more strict or better, than the othere other
From the point of view of the safety the right answer is to use From the point of view of the safety the right answer is to use both both approaches in order to optimize the region found safe enough by approaches in order to optimize the region found safe enough by both both methods i.e. the region with low risk fulfilling the deterministmethods i.e. the region with low risk fulfilling the deterministic ic requirementsrequirements
That should be the principle of a modern risk based safety regulThat should be the principle of a modern risk based safety regulationation
The role of PSA in safety management
Slide 10.
How does PSA fit into plant safety?How does PSA fit into plant safety?MMaaiinntteennaannccee aanndd tteesstt
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LLiivviinngg PPSSAA MMooddiiffiiccaattiioonnss..SSaaffeettyy uuppggrraaddiinngg
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The role of PSA in safety management
Slide 11.
How does PSA fit into plant safety?How does PSA fit into plant safety?
The Living PSA can be used for direct applications. Additionally the LPSA can be used to develop a model for use in real time on-line (risk monitor)
The results of some LPSA applications can significantly contribute to support the plant maintenance and test scheduling activities
NPP maintenance affects the random equipment behaviour, and therefore, the use of LPSA to support maintenance planning has an impact on the random disturbances
Other LPSA applications are focused towards supporting plant modifications and safety upgrading. These plant modifications have a feedback effect in the whole system.
Thus, in this way a closed control system is defined, which, providing the whole system is used in an efficient manner, will enhance the safety management of the plant
The Living PSA can be used for direct applications. AdditionallyThe Living PSA can be used for direct applications. Additionally the LPSA can be the LPSA can be used to develop a model for use in real time onused to develop a model for use in real time on--line (risk monitor)line (risk monitor)
The results of some LPSA applications can significantly contribuThe results of some LPSA applications can significantly contribute to support the te to support the plant maintenance and test scheduling activitiesplant maintenance and test scheduling activities
NPP maintenance affects the random equipment behaviour, and therNPP maintenance affects the random equipment behaviour, and therefore, the efore, the use of LPSA to support maintenance planning has an impact on theuse of LPSA to support maintenance planning has an impact on the random random disturbancesdisturbances
Other LPSA applications are focused towards supporting plant modOther LPSA applications are focused towards supporting plant modifications and ifications and safety upgrading. These plant modifications have a feedback effesafety upgrading. These plant modifications have a feedback effect in the whole ct in the whole system.system.
Thus, in this way a closed control system is defined, which, proThus, in this way a closed control system is defined, which, providing the whole viding the whole system is used in an efficient manner, will enhance the safety msystem is used in an efficient manner, will enhance the safety management of the anagement of the plantplant
The role of PSA in safety management
Slide 12.
SummarySummary
The PSA and the PSA applications are very useful tools to maintain high safety, if the user understands the basic safety philosophy, and regards the nuclear power plant safety consisting of many components, not underestimating anyone of them.The risk approach complements the deterministic approach to safety and they together assure safe operation for the whole lifetime of the nuclear power plants.
The PSA and the PSA applications are very useful The PSA and the PSA applications are very useful tools to maintain high safety, if the user understands tools to maintain high safety, if the user understands the basic safety philosophy, and regards the nuclear the basic safety philosophy, and regards the nuclear power plant safety consisting of many components, power plant safety consisting of many components, not underestimating anyone of them.not underestimating anyone of them.The risk approach complements the deterministic The risk approach complements the deterministic approach to safety and they together assure safe approach to safety and they together assure safe operation for the whole lifetime of the nuclear power operation for the whole lifetime of the nuclear power plants. plants.
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