Lecture 3 - Quantitative Risk Assessment Flashcards
What is QRA?
- QRA is a systematic, model-based, procedure for investigating the ways in which complex systems operate.
- QRAs model how human, software, and hardware elements of a system interact with each other.
- From this QRAs are used to assess the most significant contributors to the risks of a system and to determine if societal and individual risk expectations have been met.
- Across different industries different terms may be used for QRA, for example Probabilistic Risk Assessment or Formal Risk Assessment. It is best to check what the person using the words means by them.
What are the 3 basic questions?
- What can go wrong that could lead to exposure of hazards (associated with specific scenarios)?
- How likely is this to happen? (i.e. what’s the frequency/ probability of the scenario leading to the exposure)
- If it happens, what consequences are expected? (i.e. predict the magnitudes of health, safety, environment and economic consequences for each scenario)
Establishing consequences for realisation of uncontrolled hazards and/or failure of engineering controls
- Consequence estimates are often complex and require an estimation of who and what is impacted and the nature of the impact.
- In most industries it is a requirement to use structured and documented methods to identify scenarios, hazards, likelihood and consequence estimates, and controls.
- Quantitative risk assessment (QRA) is used in high hazard industries which use models and numbers to quantify the likelihood and/ or
consequence of events.
What is the value of QRA?
- 45The outputs of the QRA are used to
- highlight system design and operational deficiencies,
- prioritise resources to improve design and operation,
- identify elements of the system that contribute substantially to the risks,
- examine the uncertainty associated with these estimates,
- Test the effectiveness of the various risk-reduction strategies available
- QRA is widely used in the development of Safety Cases. Safety Cases are a regulatory requirement in high hazard industries.
What are the strengths for QRA?
- A systematic examination of the design and operation of a complex system
- Consideration of influence of system interactions and human-system interfaces
- Consideration of assumptions and uncertainties
What are the challanges for QRA?4
- Errors result from weak models, and lack of data.
- Problematic for estimating low frequency (but high impact events)
- Challenges with modelling complex dependent systems and extreme operating conditions.
What are some examples of models, tools and processes that maybe used for likelihood and/or consequence estimates in QRA?
Functional block diagrams
FMEA/ FMECA – Failure modes and effects analysis
Logic models - Fault trees and Event trees (together these form a bow-tie)
Reliability block diagrams
Reliability analysis
Monte Carlo simulation
Sensitivity analysis
How is uncertainty expressed?
REFER TO SLIDES
What re safety cases?
*QRA is widely used in the development of Safety Cases.
* Safety Cases are a regulatory requirement in high hazard industries.
- A safety case for a facility includes a:
* description of the facility,
* formal safety assessment and
* the safety management system.
- A safety case enables an operator’s to demonstrate to others (workers, regulators) that they understand the factors that influence risk and the controls that are critical to managing risk on their facility.
What are regulators?
- Regulatory powers are the powers used by government agencies and regulators to ensure individuals and industry comply with legislative requirements, and to respond to instances of non-compliance.
- In Australia, the Commonwealth, states and territories are responsible for making their own laws. Each jurisdiction has a regulator who monitors and enforces compliance with these laws.
