News

Model checking verifies the correctness of nuclear power plant safety systems

The study utilises model checking to address the insufficiencies of testing and simulation in the verification of safety systems.

Model checking as a process.

The object of Jussi Lahtinen’s dissertation was to find a more formal and mathematical approach to system verification and to develop model checking practices that are suitable for the nuclear industry. The traditional system verification methods, such as testing and simulation, do not have enough coverage to address the increasing digitalisation of safety automation systems.

         ‘Nuclear power plants have large safety systems in place that encompass multiple safety functions, such as the emergency diesel generator control system. In one of the techniques now developed, the system is divided into modules, and an algorithm is used for pinpointing the subset of modules that verifies the correctness of the system,’ says Lahtinen, explaining the practical implementation of the study.

At the architecture level, hardware failures in the microcircuits used for computing a number of functions, for example, are of pronounced significance. An individual software failure, on the other hand, is not all that safety-critical, given that the plant has a number of independent software-based safety systems in place.

         ‘Model checking is a highly effective method for finding latent design errors that may also be strange or unusual. Unlike testing or simulation, model checking is capable of achieving complete sequential coverage with respect to the requirement being examined,’ Lahtinen adds.

In the concluding phase of the dissertation, a method to support the structure-based testing of the function block diagrams used in the design of software-based systems was created. The method generates tests based on the structure of the function block diagram that describes the functioning of the safety automation system.

         ‘According to the feedback received from Fortum, the process of model checking as such may reveal errors that are easily ignored in testing. The comprehensive checking is also capable of analysing events over a very short time span,’ Lahtinen adds.

The results of the dissertation work have already been used in practical assignments for the Radiation and Nuclear Safety Authority concerning the Olkiluoto 3 project, for Fortum concerning the automation renewal of the Loviisa nuclear power plant, and for Fennovoima concerning the functional architecture of the foreseen Hanhikivi nuclear power plant. Further study on the integration of model checking with probabilistic risk analysis is already underway.

The dissertation work related to the study was supervised at the Aalto University Department of Computer Science by Professor Keijo Heljanko, and it was carried out at the VTT Technical Research Centre of Finland. A substantial part of the study was funded by the Finnish nuclear power plant safety research programme SAFIR. Model checking has been studied on a constant basis since 2007, and it is a very demanding method computationally.

More information:

Jussi Lahtinen
VTT
[email protected]
+3580 400 519 798

Keijo Heljanko
Professor
Department of Computer Science
[email protected]
+358 50 430 0771

Doctoral dissertation:  Model Checking Large Nuclear Power Plant Safety System Design

Defence of dissertation

  • Published:
  • Updated:
Share
URL copied!

Related news

digital spareparts
Research & Art Published:

Digitalising and 3D printing spare parts enables manufacturing anywhere and anytime

The digitalisation of spare parts is a step towards more sustainable business and reducing the carbon footprint of industry.
Kuva nosturista
Honoured, Research & Art, Studies Published:

Mechatronics students claim top three prizes in development project competition

The end results of this spring's Mechatronics Project course had an opportunity to shine in the development project competition hosted by industrial production and maintenance association Promaint ry and the Finnish Fair Foundation.
Postin lehdistökuva. Kuvan laitteet eivät liity opiskelijaprojektin uutiseen.
Cooperation, Studies Published:

Students carried out mobile device user survey for Posti’s parcel drivers

The project also included investigation on how the digitalization of the working environment affects the employee experience of the drivers.
taidemaalauksesta poimittu yksityiskohta ihmisen silmästä on rajattu ympyräksi oranssilla pohjalla
Research & Art Published:

Towards interfaces that distinguish user’s visual attention

Dissertation of the Month: What if interfaces we use are able to distinguish whether we are looking at them or not, and change their behavior accordingly?