Deterministic safety analyses are an important part of ensuring the safety of nuclear power plants. Various computer-aided safety analyses are typically carried out throughout the service life of a nuclear power plant, from the design and construction phase to the decommission of the plant.

The preparation of safety analyses requires vast knowledge of the laws of thermodynamics and the special characteristics of nuclear technology and fuel, as well as knowledge of the operation of the plant unit to be modelled. Thus, experts who perform safety analyses typically develop into excellent plant experts.

In addition to safety systems important and significant for nuclear safety, the process analysis model of a nuclear power plant includes the plant’s operating systems and automation. The process model expert uses the plant’s design material as the starting material: PI diagrams, automation diagrams, piping isometric drawings, etc. That is why the author of the model gets acquainted in detail with the entire plant that’s being modelled.

Analysing anticipated operational occurrences and postulated accidents provides the expert with excellent information on the dynamic behaviour of the plant. Usually, when analysing a particular case, one is not satisfied with calculating only one predefined case, but also looking for the worst combination of failures in terms of consequences by analysing different variations. In addition, the requirements of different analysis categories differ in terms of which safety class systems can be used to mitigate the consequences.

The purpose of safety analyses is to demonstrate that the plant can cope with all anticipated operational occurrences, postulated accidents, and design extension conditions, including severe accidents, so that the acceptance criteria are met and that no significant radiation consequences are caused to the public. Safety analyses also demonstrate that safety systems meet the design requirements set for them.

As a result of the demanding work, the analyst becomes one of the best experts in the plant entity and its systems. In addition, she/he learns to know the levels of defence-in-depth. When the analysis work has been carried out long enough for one plant, it is easier to take over the operations of another plant in a short time.

The people doing the analysis work are usually the best plant experts, and it is also easy for them to move on to different tasks that require understanding both the exact details and the big picture. Such expertise is needed especially in process system modifications, automation renewal projects, plant permitting, plant disturbance investigation, energy efficiency and optimisation. One of Platom’s analysis experts is Tomi Pakarinen.