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Nuclear reactor safety analysis


VTT possesses the multidisciplinary competence required to ensure safe and efficient operation of nuclear power plants including all the essential research areas:
- Fuel and reactor physics
- Thermal hydraulics
- Severe accidents
- Structural safety of reactor circuit
- Construction safety
- Probabilistic Risk Analysis (PRA)
- Automation and control room
- Organisation and human issues.


Safe and efficient use of the current four Finnish nuclear power plants with expected lifetime of 50-60 years, the new Olkiluoto 3 EPR unit to be commissioned in 2012, and possible new units to be built pose profound requirements for nuclear safety assessment and for training of experts. Within the next few years the experts who have taken part in the design, licensing, construction and start-up of the currently operating plants in Finland are retiring.


Fuel and reactor physics research includes analysis of fuel behaviour, reactor physics and dynamics with versatile calculation methods. Thermal hydraulics in cooling circuit during normal operation and in accidents is studied with versatile codes. Substantial part of knowledge in reactor dynamics and thermal hydraulics has been integrated into the APROS-code, which is currently the main tool for thermal hydraulic studies.

Accident management includes small to mid-range experiments and analyses of capabilities of modern nuclear power plants to cope with severe accidents. Experimental capabilities also include aerosol research and radiochemistry.

In structural safety of reactor circuit ands in construction safety ageing management together with new issues originating with new plant types are in the focus of the research. In these areas VTT possesses large and in to some extent unique experimental facilities together with excellent analytical tools.

References and merits

VTT has had an important role in the safety assessment of the current Finnish nuclear power plants, both during the initial licensing phase and later on in the license extensions including modernisations and power uprating. Currently VTT supports safety assessments for the new Olkiluoto 3 unit, and similar studies for international customers.

Public reference on VTT’s broad activities in reactor safety research is found via the research done in SAFIR2010, The Finnish Research Programme on Nuclear Power Plant Safety 2007-2010.

Additional information

Timo Vanttola
Technology manager
+358 20 722 5020

Eija Karita Puska
Research Coordinator
+358 20 722 5036