Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems...
Transcript of Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems...
![Page 2: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/2.jpg)
The objectives of (nuclear) safety
THREAT (Release of radioactivity from a Nuclear Power Plant (NPP))
REGULATIONS
Objectives:
▪ ensure that (nuclear) facilities operate normally and without an
excessive risk of operating staff and the environment
▪ prevent incidents and limit the consequences of any incidents that
might occur.
Design
Operation
Decommissioning
Pla
ntlife
time
![Page 3: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/3.jpg)
Safety assessment competence is the key
to making the right decisions in design,
licensing and operation.
Prof. M. El-Shanawany
Department of Nuclear Safety & Security, Head
International Atomic Energy Agency
![Page 4: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/4.jpg)
Deterministic Safety Assessment (DSA)
Probabilistic Safety Assessment (PSA)
Safety Assessment
![Page 5: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/5.jpg)
Prof. George Apostolakis
Commissioner
Safety Assessment
The model of the world:
Deterministic, e.g., a thermal hydraulic code DSA
Probabilistic, e.g., a Monte Carlo simulation PSA
▪ Both deterministic and probabilistic models of the world have assumptions and parameters.
▪ How confident are we about the validity of these assumptions and the numerical values of the parameters?
![Page 6: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/6.jpg)
Towards and integrated DSA and PSA framework
Traditional Deterministic
ApproachesProbabilistic-Based
Approaches
Risk-Informed
Approaches
IDPSA
Combination of
Deterministic
and
Probabilistic
approaches
Complementary methods of safety analysis are used jointly in evaluating the
safety:
1. Deterministic Safety Analysis (DSA)
2. Probabilistic Safety Analysis (PSA)
![Page 7: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/7.jpg)
Application: LBE-XADS
Nuclear island
Conventional island• Accelerator Driven System (ADS)
▪ A means of transmuting nuclear waste
▪ A new type of fission reactor
▪ Both
• How?
▪Some of the “afterheat” of spent
nuclear fuel can be captured in a
power generator, instead of a
mountain– Goal is 95% of Minor Actinides (MA) & Long-
Lived Fission Products (LLFPs) transmuted
– 250 kg/300 days
![Page 8: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/8.jpg)
Accelerator Driven System for Disposing of Spent Nuclear Fuels
![Page 9: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/9.jpg)
The Concept
• Proton accelerator creates neutrons by spallating high-Z
target nuclei (Z=atomic/proton number)
• Spallation neutrons used to maintain fission reaction
where not normally possible
▪ Subcritical piles
▪ In waste actinides
▪ Chain reaction can’t exist w/o accelerator: To stop, just
unplug it
b e a m
s c a n n i n g
L B E f lo w
8 c m s c a n
1 2 c m d u c t w i d th
![Page 10: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/10.jpg)
Lead Bismuth Eutectic Accelerator Driven System (LBE-XADS)
![Page 11: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/11.jpg)
General View inside the Subcritical Assembly
![Page 12: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/12.jpg)
Deterministic Safety Assessment (DSA)Probabilistic Safety Assessment (PSA)
Safety Assessment
![Page 13: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/13.jpg)
The basic principles of DSA
1) Presence of leaktight barriers between the radioactive source and the
public/environment
▪ fuel cladding (1)
▪ primary reactor coolant system (2 and 3)
▪ containment building (4)
![Page 14: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/14.jpg)
The basic principles of DSA
2) Defence-in-depth, which applies to both the design and the operation
of the facility
Accidents may still occur
Systems are to be designed and installed
to combat them and to ensure that their
consequences are limited to a level that is
acceptable for both the public and the
environment
[Commission’s White Paper, February, 1999]
External hazards
Component
failures
Human error
Off-site emergency procedures
Safeguards
Protection
Prevention and surveillance
![Page 15: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/15.jpg)
The defence-in-depth principle
Prevention and surveillance:
▪ Items of equipment are designed with adequate safety margins
Protection:
▪ Provisions are made to detect incidents and to prevent them from
escalating safety systems are designed to restore the plant to a normal
state and maintain it under safe conditions.
Safeguard:
▪ Special safety systems are therefore designed to limit the consequences
of severe accidents to an acceptable level.
Off-site and emergency procedures:
▪ Designed to provide protection against severe conditions under which
defences at the three levels described above prove inadequate.
![Page 16: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/16.jpg)
DSA before PSA (prior to 1975)
Design Basis Accidents (DBA) [ NUREG/CR-6042, USNRC, 1994]
▪ postulated accidents that a NPP must be designed and built to
withstand, without loss of the system structures and components
necessary to assure public health and safety
▪ include at least one significant failure of a component: failures
beyond those consistent with the single-failure criterion are not
required (unlike in PSAs)
• Very unlikely events (possible inconsistencies in requirements and decisions, unbalancing safety measures and introducing excessive burden)
• Small in number (Need to consider a broader set of safety threats, raking them, identifying and assessing uncertainties. Need to consider many operational situations (start up, shutdown, refuelling, maintenance, etc.), concurrent failures and human performance)
• Conservative initial conditions (to compensate for uncertainties)
CONCERNS ABOUT UNCERTAINTY MANAGEMENT
![Page 17: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/17.jpg)
“Conservatism” of DSA
Assumed
threats profile
Assumed conservative
case
Protection
against
assumed
conservative
threat
![Page 18: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/18.jpg)
Importance of the principles of DSA
Application: LBE-XADS
SAFETY BY DESIGN
Subcritical reactor
MULTI-BARRIERS:
Pellet
Safety vessel
Containment
Secondary coolant
![Page 19: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/19.jpg)
- The accident, caused by a sudden surge of power, destroyed the reactor and
released massive amounts of radioactive material into the environment
- Lack of containment
Chernobyl experience should remain a valuable part of the information to be taken into
account when dealing with reactor safety issues in the future
importance of the principles of DSA
The accident in 1986 at Chernobyl (I)
![Page 20: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/20.jpg)
- The accident, caused by a sudden surge of power, destroyed the reactor and
released massive amounts of radioactive material into the environment
- Lack of containment
Chernobyl experience should remain a valuable part of the information to be taken into
account when dealing with reactor safety issues in the future
importance of the principles of DSA
The accident in 1986 at Chernobyl (I)
![Page 21: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/21.jpg)
Deterministic Safety Assessment (DSA)
Probabilistic Safety Assessment (PSA)
Safety Assessment
![Page 22: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/22.jpg)
Farmer’s Paper (1967)
Credible (DBAs) VS incredible accidents
not logicalALL is based on assumptions in expert judgment about the credible cases
Example: consider a loss-of-coolant accident (LOCA),
various outcomes: - safe cooldown/shutdown
- partial failures
- accidental cooldown/shutdown
- severe accident
Classification of events according to the probability of its occurrence and potential consequences
• Design-basis accident (DBA):
• Beyond design-basis accidents (BDBA):
Accident sequences that are possible but were not fully considered in the
design process because they were judged to be too unlikely.
![Page 23: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/23.jpg)
The concept of risk
Risk and Safety are considered as two opposed terms, that can be used to assess a same thing
Remember PRA = PSA
• What can go wrong? (accident sequences or scenarios)
• How likely are these scenarios?
• What are their consequences?
Definition of Risk
{ , , }i i i
R s c
is
ic
i
Three different aspects of risk:Risk assessmentRisk perceptionRisk communication
Decision makers can be influenced by all of these
![Page 24: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/24.jpg)
The concept of risk
"Farmer curve”
![Page 25: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/25.jpg)
Techniques for PSA
Hazard identification: FMEA (Failure Modes and Effects Analysis) & HAZOP (HAZard and OPerabilitystudy)
Accident Scenarios Identification: ETA, FTA
System Failure Probabilty Assessment: ETA, FTA, Monte Carlo simulation
![Page 26: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/26.jpg)
ETA: comments
1. One ET for each accident initiator
2. Time and logic of Sk interventions important for the tree structure (simplifications possible)
3. Sk states conditional on accident initiator and previous Sj’s
4. Conditional probabilities of Sk states (FTA)
![Page 27: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/27.jpg)
ETA+FTA
![Page 28: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/28.jpg)
PSA Reactor Safety Study (WASH-1400; 1975)
Prior Beliefs
• Protect against Large LOCA
• Core Damage Frequency (CDF) is low
(about once every 100 million years, 10-8 per reactor year)
• Consequences of accidents would be disastrous
Major Findings
• Dominant contributors: Small LOCAs and Transients
• CDF higher than earlier believed(best estimate: 5x10-5, once every 20,000 years; upper bound: 3x10-4 per reactor year, once
every 3,333 years)
• Consequences significantly smaller
• Support systems and operator actions very important
![Page 29: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/29.jpg)
“Conservatism” of DSA PSA
![Page 30: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/30.jpg)
The accident in 1979 at the Three Mile Island (TMI-2)
- Combination of equipment malfunctions, design-related problems and worker errors
led to TMI-2's partial meltdown and very small off-site releases of radioactivity
- Small radioactive releases
- No detectable health effects on plant workers or the public
Reveals potential consequences of failure to manage
NPP safety only based on DSA
Pilot operating relief valve
(PORV) fails stuck-open
![Page 31: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/31.jpg)
PSA Policy Statement (1995)
The use of PSA should be increased to the extent supported by the
state of the art and data and in a manner that complements the
defense-in-depth philosophy.
PSA should be used to reduce unnecessary conservatisms
associated with current regulatory requirements.
![Page 32: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/32.jpg)
PSA Model Overview
PLANT MODEL (PHYSICS, FUEL AND THERMAL
HYDRAULIC MODELS)
CONTAINMENT
MODEL
SITE/CONSEQUENCE
MODEL
(ATMOSPHERIC,
DISPERSION
MODELS)
Level I Level II Level III
Results
Accident sequences
leading to plant
damage states
(CDF frequencies)
Results
Containment
failure/release
sequences
Results
Public health
effects
PLANT MODE
At-power Operation
Shutdown / Transition
Evolutions
SCOPE
Internal Events
External Events
Uncertainties
Event Sequence Analysis
Event Tree Analysis
Fault Tree Analysis
Containment Event Tree
![Page 33: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/33.jpg)
Application: LBE-XADS
The model of the LBE-XADS has been embedded within an MC-driven fault
injection engine to sample component failures.
Maxim
um
dia
therm
ic o
il t
em
pera
ture
Upper threshold
Lower threshold
“High-temperature failure mode”
“Low-temperature failure mode”
“safe”
4 control/actuator faults
64 accident scenarios
E. Zio, F. Di Maio, “Fuzzy Clustering Classification of Dynamic Scenarios of Digital Instrumentation and Control in Nuclear Power
Plants”, Proceedings of the American Nuclear Society (ANS) NPIC HMIT 2009 Topical Meeting - Nuclear Plant Instrumentation,
Controls, and Human Machine Interface Technology, 5-9 April 2009, Knoxville, Tennessee, American Nuclear Society.
E. Zio, F. Di Maio, “Processing Dynamic Scenarios from a Reliability Analysis of a Nuclear Power Plant Digital Instrumentation and
Control System”, Annals of Nuclear Energy, doi:10.1016/j.anucene.2009.06.012, 2009.
![Page 34: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/34.jpg)
SIMULINK model of the LBE-XADS
![Page 35: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/35.jpg)
Level I PSA: an example
PLANT MODEL (PHYSICS, FUEL AND THERMAL
HYDRAULIC MODELS)
Level I
Results
Accident sequences
leading to plant
damage states
(CDF frequencies)
Fault Tree Analysis
![Page 36: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/36.jpg)
PSA contain uncertainties arising from three main sources:
• lack of comprehensive data: It is impossible to demonstrate the
exhaustiveness of a PSA, even when the scope of the analysis
has been extended to as large a number of situations as possible
• reliability of data: frequency of initiating events (e.g., rare initiating
events such as the combination of a steam piping break and a
steam-generator tube break) common-mode failures and failures
resulting from human actions.
• modelling assumptions that cannot easily be quantified (e.g.,
resistance of certain components under accident conditions, poorly
understood physical phenomena or human actions).
Limitations of PSA (I)
![Page 37: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/37.jpg)
The accident in 2011 at the Daichi NPP
- Following a major earthquake, a 15-metre tsunami disabled the power supply and
cooling of three Fukushima Daiichi reactors, causing a nuclear accident on 11 March
2011.
- All three cores largely melted in the first three days.
Combination of external events (earthquake and tsunami)
Multi-unit severe accident
![Page 38: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/38.jpg)
Deterministic Safety Assessment (DSA)
Probabilistic Safety Assessment (PSA)
Safety Assessment
Integrated Deterministic
Probabilistic Safety Assessment
IDPSA = DSA+PSA
![Page 39: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/39.jpg)
State-of-the-art PSA / DSA are challenged by increasing complexity of
the existing plants safety systems
▪ Passive safety systems in new plants and retrofits in existing plants
▪ Digital Instrumentation & Control (I&C) and Human reliability
▪ Severe accident management implemented in design
WHY? very low CDF by reducing the number of equipment that can
breakdown
Difficult heuristic “a priori” judgment about conservatism in selected DSA
and PSA scenarios
The need of integration
![Page 40: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/40.jpg)
IDPSA
• Unquantified Probabilities
• Design-Basis Accidents
• Defense in Depth
• Can impose heavy regulatory
burden
• Incomplete
•Quantified Probabilities
• Scenario Based
• Realistic
• Rationalist Defense in
Depth
• Incomplete
Complementary methods of safety analysis are used jointly in evaluating the
safety of an NPP:
1. Deterministic Safety Analysis (DSA)
2. Probabilistic Safety Analysis (PSA)
Traditional Deterministic
ApproachesProbabilistic-Based
Approaches
Risk-Informed
Approaches
IDPSA
Combination of
Deterministic
and
Probabilistic
approaches
![Page 41: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/41.jpg)
IDPSA definition
Integrated Deterministic-Probabilistic Safety Analysis
(IDPSA) is a collective name for the variety of different
tools which use tightly coupled probabilistic and
deterministic approaches to address in a consistent
manner:
– stochastic aspects of scenario
– modelling uncertainties
![Page 42: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/42.jpg)
Benefits of integration
IDPSA can provide additional help to PSA and DSA practitioners in:
1) Resolving time dependent interactions between
• physical phenomena,
• equipment failures,
• safety and non-safety systems interactions,
• control logic and operator actions.
2) Identification of a-priori unknown vulnerable scenarios, or “sleeping
threats”
3) Reduction of reliance on expert judgment and simplifying assumptions
about complex interdependencies
• PSA and DSA can calculate what we know as an issue
• PSA and DSA are not capable of revealing what, and to what extent, we do
not know
![Page 43: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/43.jpg)
“Conservatism” of DSA
Assumed
threats profile
Assumed
conservative case
Protection against
assumed
conservative threat
![Page 44: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/44.jpg)
Deterministic and probabilistic safety assessment
(DSA&PSA)
DSA
Design Basis Accidents (DBAs)
PSA
Minimal Cut Sets
(MCS)(Precautionary
principle)
The problem:
Unknown plant
vulnerabilities are
left unknown in
traditional DSA
and PSA
(Safety margins,
multiple barriers)
![Page 45: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/45.jpg)
T
1
2 3 4
5 6
MCS
{1}
{2,4}, {2,5}, {2,6}
{3,4}, {3,5}, {3,6}
PSA: Construction of threat profiles by MCS
Each minimal cut set is an AND gate of a
set of basic events necessary and
sufficient to cause the top event
T
………
![Page 46: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/46.jpg)
T
1
2 3 4
5 6
PSA APPROXIMATION of threat profiles: MCS-order cut-off
CONSIDER:
Small order mcs
T
………
![Page 47: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/47.jpg)
T
1
2 3 4
5 6
T
………
CONSIDER:
Probability of occurrence larger
than a given threshold
PSA APPROXIMATION of threat profiles: MCS-order cut-off
![Page 48: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/48.jpg)
WORRY!!!! Wrong:
Probabilities of top events
Frequencies of sequences
Safety margins
Importance factors
Sensitivity indexes
APPROXIMATED
threat profiles
DSA
Design Basis Accidents (DBAs)
PSA
Minimal Cut Sets
(MCS)(Precautionary
principle)
Deterministic and probabilistic safety assessment
(DSA&PSA)
![Page 49: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/49.jpg)
Integrated Deterministic and Probabilistic Safety
Assessment (IDPSA=DSA + PSA)
IDPSA
IDENTIFIED SCENARIO!!!
-Timing of events
-Sequences of failures
PRIME IMPLICANTS
«CORRECT» THREAT
PROFILE
DSA
Design Basis Accidents (DBAs)
PSA
Minimal Cut Sets
(MCS)(Precautionary
principle)
![Page 50: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/50.jpg)
Application: LBE-XADS
The model of the LBE-XADS has been embedded within an MC-driven fault
injection engine to sample component failures.
Maxim
um
dia
therm
ic o
il t
em
pera
ture
Upper threshold
Lower threshold
“High-temperature failure mode”
“Low-temperature failure mode”
“safe”
4 control/actuator faults
64 accident scenarios
E. Zio, F. Di Maio, “Fuzzy Clustering Classification of Dynamic Scenarios of Digital Instrumentation and Control in Nuclear Power
Plants”, Proceedings of the American Nuclear Society (ANS) NPIC HMIT 2009 Topical Meeting - Nuclear Plant Instrumentation,
Controls, and Human Machine Interface Technology, 5-9 April 2009, Knoxville, Tennessee, American Nuclear Society.
E. Zio, F. Di Maio, “Processing Dynamic Scenarios from a Reliability Analysis of a Nuclear Power Plant Digital Instrumentation and
Control System”, Annals of Nuclear Energy, doi:10.1016/j.anucene.2009.06.012, 2009.
A. Cammi, L. Luzzi, A. Porta, M. E.
Ricotti, Modelling and control strategy of
the Italian LBE-XADS. Progress in
Nuclear Energy 48 (2006) pp. 578-589.
![Page 51: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/51.jpg)
Level I PSA: traditional approaches
PLANT MODEL (PHYSICS, FUEL AND THERMAL
HYDRAULIC MODELS)
Level I
Results
Accident sequences
leading to plant
damage states
(CDF frequencies)
Fault Tree Analysis
![Page 52: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/52.jpg)
ON OFF
Failure
As Good As New Failed
• Static: PSA is “Yes/No”, “black-and-white”
t
X(t)
100%
0%
System unavailability U(t) = Pr[X (t) <100%]
U(t) = Pr[X (t) =0%]
Conventional modelling to PSA
![Page 53: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/53.jpg)
Continuous “Grey” zone can integrally contain not less risk than “black-and-
white” skeleton of PSA tree
What can be worse than failure?
• Wrong timing of successful operation
• Partial success
• …
Conventional modelling to PSA
• Dynamic: Timing makes even discrete (0/1) parameters
continuous
![Page 54: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/54.jpg)
LBE-XADS: dynamic effects
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64
Fre
qu
en
cy o
f th
e e
nd
sta
te
occu
rren
ce
Failure sequence
Low-temperature failure mode Safe mode High-temperature failure mode
![Page 55: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/55.jpg)
LBE-XADS: effect of the ORDER of failure events
Dependence of the accident sequence end state from the ordering of the
components faults in the sequence
0 500 1000 1500 2000 2500 3000
240
260
280
300
320
340
360
380
400
Time [s]
Oil
tem
pera
ture
[C
]
Scenario: Air coolers fail at t=1500 [s], PID fails at t=2000 [s]
Air coolers @ 300[kg/s], PID output @ 500 [kg/s]
Air coolers @ 500[kg/s], PID output @ 220 [kg/s]
Air coolers @ 450[kg/s], PID output @ 100 [kg/s]
Air coolers @ 797[kg/s], PID output @ 0 [kg/s]
0 500 1000 1500 2000 2500 3000260
280
300
320
340
360
380
400
Time [s]
Oil
tem
pera
ture
[C
]
Scenario: PID fails at t=1500 [s], air coolers fail at t=2000 [s]
PID output @ 500 [kg/s], air coolers @ 300[kg/s]
PID output @ 220 [kg/s], air coolers @ 500[kg/s]
PID output @ 100 [kg/s], air coolers @ 500[kg/s]
PID output @ 0 [kg/s], air coolers @ 300[kg/s]
![Page 56: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/56.jpg)
LBE-XADS: digitalization effects
Dependence of the accident sequence end state on the exact timing of the
components failures
0 500 1000 1500 2000 2500 3000250
300
350
400
450
500
550
Time [s]
Oil
tem
pera
ture
[C
]
PID controller fails at time t=2239
PID controller fails at time t=2240
![Page 57: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/57.jpg)
LBE-XADS: magnitude effects
Dependence of the accident sequence end state with respect to the
components faults magnitudes
0 500 1000 1500 2000 2500 3000260
280
300
320
340
360
380
Time [s]
Oil
tem
pera
ture
[C
]
Scenario: PID fails at t=1500 [s]
PID controller fails at time t=1500, output @ 500 [kg/s]
PID controller fails at time t=1500, output @ 220 [kg/s]
PID controller fails at time t=1500, output @ 100 [kg/s]
PID controller fails at time t=1500, output @ 0 [kg/s]
0 500 1000 1500 2000 2500 3000260
280
300
320
340
360
380
400
Time [s]
Oil
tem
pera
ture
[C
]
Scenario: PID fails at t=1500 [s], air coolers fail at t=2000 [s]
PID output @ 500 [kg/s], air coolers @ 300[kg/s]
PID output @ 220 [kg/s], air coolers @ 500[kg/s]
PID output @ 100 [kg/s], air coolers @ 500[kg/s]
PID output @ 0 [kg/s], air coolers @ 300[kg/s]
![Page 58: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/58.jpg)
Methods for IDPSA
Conventional approaches to PSA
Fault-tree/event-tree (FT/ET) at best can account for the order
of occurrence of events in system evolution
Dynamic methodologies are defined as those that explicitly
• account for the time element in probabilistic system
evolution
• are needed when the system has
hardware/process/software/human interactions
![Page 59: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/59.jpg)
Dynamic methodologies for IDPSA
Continuous: CET (Continuos Event Tree)
CCCMT (Continuous Cell-to-Cell Mapping Technique)
Discrete: CCMT (Cell-to-Cell Mapping Technique)
MCDET/DYLAM/DETAM/ISA (Dynamic Event Tree
Generation)
Graphical: PETRI NETS
DYNAMIC FLOWGRAPHS
GO-FLOW
![Page 60: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/60.jpg)
Dynamic methodologies for IDPSA
Continuous: CET (Continuos Event Tree)
CCCMT (Continuous Cell-to-Cell Mapping Technique)
![Page 61: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/61.jpg)
Continuous Event Trees (CET)
Describes the system behavior in terms of the probability pn(x,t) of finding the
system in the state-space (x-space) with configuration n at a given time t.
Input:
• Configuration transition rates h(n|m, x, t)
• Probability Fn(x,t) that the system leaves configuration n before time t
• Initial condition p0(x,0)
Output:
pn(x,t)
Solution Method:
Monte Carlo simulation
x1
x2 h(n|m, x, t)
m
p0(x,0)
n
Fn(x,t)Fm(x,t)h(m|0, x, 0)
![Page 62: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/62.jpg)
Continuous Cell-to-Cell Mapping (CCCMT)
Describes the system behavior in terms of the probability πi(j,t) of finding the
system in the cell j of the state-space (x-space) with configuration i at a given
time t.
• Derivable from CET
Input:
• Cell-to-cell transition probabilities g(j|j’,i’,t) in the state space
• Configuration transition rates Fi(j’,t) that the system leaves configuration i
before time t
• Initial condition π0(j0,0)
Output:
πi(j,t)
Solution Method:
Monte Carlo simulation
ODE solvers
x1
x2 g(j|j’,i’,t)
j'
π0(j0,0)
j
Fi(j,t)Fi’(j’,t)g(j’|j0,i’,t)
j0
![Page 63: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/63.jpg)
Dynamic methodologies for IDPSA
Discrete: CCMT (Cell-to-Cell Mapping Technique)
MCDET/DYLAM/DETAM/ADS/ISA (Dynamic Event
Tree Generation)
![Page 64: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/64.jpg)
Cell-to-Cell Mapping (CCMT)
Describes the system behavior in terms of the probability πi(j,k) of finding the
system in the cell j of the state-space (x-space) with configuration i at a given
time k (k=0,1,…).
• Derivable from CET
Input:
• Cell-to-cell transition probabilities g(j|j’,i’,k) in the state space
• Configuration transition rates Fi(j’,k) that the system leaves configuration
i before time step k
• Initial condition π0 (j0,0)
Output:
πi(j,k)
Solution Method:
Monte Carlo simulation
Matrix solvers
x1
x2 g(j|j’,i’, k)
j'
π0(j0,0)
j
Fi(j, k)Fi’(j’, k)g(j’|j0, i’,k)
j0
![Page 65: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/65.jpg)
Comparison
![Page 66: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/66.jpg)
Dynamic Event Tree Methodologies
MCDET/DYLAM/DETAM/ISA
• All methods generate event trees based on possible trajectory branching during system
evolution
• Methods differ in terms of branching and pruning rules, human reliability models and operator
representation
Branching occurs when particular
conditions have been reached:
•Value of specific variables
•Specific time instants
•Plant status
![Page 67: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/67.jpg)
Traditional PRA tools (ET/FT) not suitable because:
• ORDER of failure events neglected
• TIMING of failure events neglected
IDPSA Methods proposed as suitable but:
• Modelling and computationally demanding
• Number of scenarios to be analyzed much larger than in the classic
FT/ET approach
A posteriori information retrieval
Key Points of IDPSA
![Page 68: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/68.jpg)
A posteriori information retrieval
The number of the scenarios that are simulated is much larger than
that of the classical ET/FT approaches
Aim: Identify and group the scenarios of a dynamic safety assessment by
characterizing the principal patterns of system evolution towards failure with
an evolutionary Fuzzy C-Means (FCM) clustering algorithm
E. Zio, F. Di Maio, “Processing Dynamic
Scenarios from a Reliability Analysis of a
Nuclear Power Plant Digital
Instrumentation and Control System”,
Annals of Nuclear Energy, Vol. 36(9),
2009
![Page 69: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/69.jpg)
Application: LBE-XADS
Maxim
um
dia
therm
ic o
il t
em
pera
ture
Upper threshold
Lower threshold
“High-temperature failure mode”
“Low-temperature failure mode”
“safe”
Feedforward control stuck @ t=0 AND failed
coomunication between air coolers and actuators
PID output stuck @ t=0
Nominal
![Page 70: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/70.jpg)
Application: LBE-XADS
Maxim
um
dia
therm
ic o
il t
em
pera
ture
Upper threshold
Lower threshold
“High-temperature failure mode”
“Low-temperature failure mode”
“safe”
Feedforward control stuck @ t=0
Failed communication between air
coolers actuators and PID @ t=0
Air coolers stuck @ t=0
![Page 71: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/71.jpg)
Application: LBE-XADS
Maxim
um
dia
therm
ic o
il t
em
pera
ture
Upper threshold
Lower threshold
“High-temperature failure mode”
“Low-temperature failure mode”
“safe”
Failed communication
between air coolers actuators
and PID @ t=0 AND Air
coolers stuck
Air coolers stuck @ t=0
PID output stuck @ t=0
![Page 72: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/72.jpg)
The method
Fuzzy C-MEANS classifier
Matlab® fcm(…)
![Page 73: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/73.jpg)
The FCM algorithms
Target: identify similarity in data
partitioning the data set to minimize:
•Constraints
•Iterative scheme
c
i
N
k
ikr
ik vxdVJ m
1 1
2 ),()(),(
Degree of membership of to cluster Γikx
Center of the cluster Γi
ikiv ,
Nk
c
i
ik ,...,2,11
1
Nkciik , 2, 1, , , 2, 1,10
Nkxk ,...,1,
![Page 74: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/74.jpg)
Clustering results
System state variables Process variable
Fault 1
time
Fault 1
magnitude
Fault 2
time
Fault 2
magnitude
Fault 3
time
Fault 3
magnitude
Fault 4
time
Temperature of the primary
coolant at time t=3000 [s]
1- Feature Selection:
• Engineering judgement
RESULTS:
• Functional Principal Components analysis
2- RESULTS:
Fuzzy C-Means
Temperature 1st, 2nd, 3rd PC’s 5.25%
Test Set Misclassification Rate
Fuzzy C-Means
System state variables and Process Variable 7.65%
Test Set Misclassification Rate
![Page 75: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/75.jpg)
![Page 76: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/76.jpg)
ARTIFICIAL INTELLIGENCE AND ADVANCED SIMULATION FOR THE
SAFETY, RELIABILITY AND MAINTENANCE OF ENERGY SYSTEMS
(10 ECTS – 5+5) – 1st semester AA 2018/2019
• INTEGRATED DETERMINISTIC AND PROBABILISTIC SAFETY ANALYSIS
OF NUCLEAR POWER PLANTS (5 ECTS)
The objective of the course is to provide students with an understanding of the
Deterministic (D) and Probabilistic (P) Safety Analysis (SA) methods, and their
integration (IDPSA), which requires Artificial Intelligence (AI) and advanced
simulation methods. These will be presented with respect to practical cases of
nuclear systems.
• COMPUTATIONAL METHODS FOR RELIABILITY, AVAILABILITY AND
MAINTENANCE (5 ECTS)
The goal of this course is to provide students with the knowledge on Artificial
Intelligence (AI) and advanced simulation methods used for the reliability
and availability analysis, and maintenance engineering of industrial
equipment and energy systems.
![Page 77: Integrated Probabilistic and Deterministic Safety ... · • safety and non-safety systems interactions, • control logic and operator actions. 2) Identification of a-priori unknown](https://reader034.fdocuments.in/reader034/viewer/2022051808/60097953dee7880da53edd85/html5/thumbnails/77.jpg)
SAFETY PERFORMANCE ASSESSMENT OF RADIOACTIVE WASTE
REPOSITORIES (5 ECTS)
• The primary goal of this course is to provide the students with the adequate
competence on methods and techniques for the assessment of the
safety performance of a radioactive waste repository, which requires the
systematic analysis of the performance of the engineered and natural barriers
of protection against radionuclide release and dispersion.