Formal–statistical methods - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 63

methods of analysis and specific tasks. First, it is the general problem of
determining an acceptable level of risk, safety standards for personnel, the
public and environmental protection. Secondly, the acceptable level of risk
is usually defined in areas with poor or unverified information, especially
when it comes to new processes or technology.Thirdly, the task of analysis
is to solve probabilistic problems that could lead to significant discrepancies
in the results. Fourthly, risk analysis should be viewed as a process of
solving multiobjective problems that may arise as a compromise between
the parties interested in the outcome of the analysis.
Risk analysis should give answers to three basic questions:
1. Which harmful events can happen? (hazard identification),
2. How often may this happen? (frequency analysis),
3. What might the consequences be? (analysis of the consequences).
The main element of risk analysis is hazard identification (detection of
potential violations) which can lead to negative consequences. The process
of risk analysis expressed in the most general form can be presented as a
series of sequential events:
1. Planning and organisation of work.
2. Hazard identification.
2.1. Hazard detection.
2.2. Preliminary assessment of the characteristics of hazards.
3. Risk assessment.
3.1. Frequency analysis.
3.2. Analysis of the consequences.
3.3. Uncertainty analysis.
4. Development of recommendations for risk management.
Firstly, the initial stage of any risk analysis is planning and organisation
of work. Risk analysis is conducted in accordance with the requirements of
regulations in order to provide input to the risk management process, but
a more accurate selection of tasks, means and methods of risk analysis is
usually not regulated. The documents emphasise that risk analysis should
match the complexity of the processes, the availability of essential data and
the qualification of specialists conducting the analysis. At the same time,
more simple and understandable methods of analysis should be preferred
for more complex methods that are not fully clear and methodically
supported. Therefore, the first step is to:
• describe the reasons and problems that caused the need for risk
analysis;
• identify and describe the analyzed system;
• choose the appropriate command for analysis;
• identify sources of safety information systems;
• specify the source data and restrictions governing the limits of risk
analysis;
• clearly define goals of risk analysis and criteria for acceptable risk.
All the regulations require documenting this phase of risk analysis.

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