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Reactor and aerosol physics for fission and fusion


Serpent model of the JET fusion reactor

​When you need reliable and efficient modeling or measurement services - VTT will deliver. We care about customer needs.


Nuclear reactor analysis services include:

  • Criticality safety analysis of fissile material in storage pools, transfer casks, final disposal canisters, etc.
  • Evaluation of radionuclide inventories of fuel and irradiated materials.
  • Production of cross sections f​​or reactor core calculations.
  • Radiation dose rate and shielding analysis.
  • Research reactor modeling.
  • Photon transport calculations.

Fusion physics and technology services include:

  • Fusion power plant simulator design.
  • Full size reactor balance of plant calculations and analyses.
  • Fusion reactor core calculations, including the design of optimum heating and current drive systems.
  • Fusion neutronics, source terms and transport using high-fidelity Monte Carlo methods.
  • Plasma-material surface analysis using SIMS device.
  • Plasma wall cleaning processes.
  • Fusion power related diagnostics expertise under reactor relevant conditions.

Experimental source term analysis and aerosol physics include:

  • Experimental analysis of fission products chemistry and transport / filtration as gaseous and aeresol compounds in primary circuit and containment conditions in a severe nuclear power plant accident.
  • Aerosol research in other application areas such as e.g. emission measurements, material research, new device testing, and measurement services.
  • Research and measurement services can be fitted based on the customer requirements:
                • Custom-built experimental set-ups
                • Measurements also at customer site

 Examples of service packages

Reactor analysis - Criticality safety

  • Criticality safety analysis using state-of-the-art calculation tools.
  • Reactivity changes due to variable conditions in fresh and spent fuel pools and transport as specified by the customer.
  • Reactivity changes of final disposal canisters at different stages of the disposal process.

Reactor analysis - Inventory calculations

  • Radionuclide inventory calculations and source term determination of fuel assemblies for final disposal and severe accident analysis. Results will include atomic densities, activities, decay heat, photon emission rates, spontaneous fission rates, etc. as desired by the customer.
  • Neutron activation analysis for reactor core internals and other components subjected to strong neutron irradiation. Provides data for decommissioning waste handling and estimates of dose rates for dismantling planning.

Reactor analysis - Cross sections and reactor modeling

  • Production of homogenized group constants for nodal diffusion codes.
  • Determination of reactor physics parameters such as e.g. prompt neutron lifetime, peaking factor, power density, etc. for various fuel assembly types and reactor cores.
  • Reasearch reactor modeling using high-fidelity Monte Carlo methods.

Fusion physics and technology

  • Power plant simulator design for ITER.
  • Reactor core physics calculations for tokamaks, including neutral beam heating and current drive optimisation.
  • Neutronics calculation and analysis for ITER.
  • Fusion diagnostics I&C.
  • Estimating dust and tritium inventories for ITER reactor in-vessel components.

Aerosol physics - Experimental analysis of fission products

  • Design and construction of an automated sampling system for the high temperature chemistry of iodine, CHIP, study.
  • Design and construction of a facility for revaporisation study of Phébus FP program samples.
  • Online monitoring of radiocarbon emissions during the normal operation of a nuclear power plant.

Aerosol physics - other applications

  • Emission measurements of a bio-oil-operated heating boiler in power plant scale.
  • Emission measurements of a coal power plant.
  • Performance testing of a coal power plant ESP filter.
  • Performance testing of an industrial particle monitor.
  • Measurement and chemical analysis of particles in gas phase and liquid phase. 

Why choose VTT 

VTT has several decades of experience in reactor analysis calculations and aerosol physics. Our staff is highly educated and experienced both in modeling and experimental research.

  • We have extensive experience in the use of both deterministic and Monte Carlo based particle transport codes.
  • VTT has a long history of developing our own calculation codes such as e.g. Apros and Serpent providing us a deep understanding on the capabilites and limitations of reactor modeling. 
  • We have a broad network of collaboration enabling us to cover any additional needs with reliable sources of expertise.
  • VTT has a deep knowledge of and connections to Euratom and ITER programs at all levels, making us a desirabe collaborator acting between the private sector and large scale nuclear projects.
  • VTT is trusted by colleagues, communities and governments.
  • We provide continued customer support - VTT will preserve the models and data for purposes of future modeling when updates are needed by the customer.

​Funding organizations and projects involving VTT


European laboratories with a fusion device


Fusion research outside Europe


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