System message

The VR-2 reactor is a subrcitical reactor. A subcritical reactor is a simple device containing an insufficient amount of fuel.  Without an external source of neutrons, it stops, i.e. it cannot sustain a fission chain reaction.

The fact that the subcritical reactor can be stopped by simply removing the neutron source makes its design very simple. It uses inherent safety and passive elements, i.e. the response of the system is based on physical principles such as the use of gravity or the effect of different pressures.

What will the VR-2 look like?

  • Cylindrical container
  • Internal lattice system of different geometry - square, triangular, different distance of the rods
  • EK-10 fuel pins
  • Moderator - light water (possibility of varying the temperature and water level)
  • Monitoring system
  • External neutron source (various types of sources)
  • Shielding - light water and concrete
  • Experimental equipment - channels

The fuel was donated by the Aalto University in Finland, where it was part of a subcritical reactor in the 1970´s. The Faculty participated in the transport of the fuel to the Czech Republic in close cooperation with the Alta Group; and the transport containers were borrowed from the CEZ Group.

The fuel consists of a dispersion of UO2 with Mg in an aluminium coating. The rods used are enriched by 10 % 235U or rods with natural uranium (0.72%) are used. The diameter of the rod is 10.5 mm; the cladding is aluminium and its thickness are 1.6 mm, and the weight of the pin is 300 g.

Safety features

  • Design based on inherent safety preventing the development of an uncontrolled fission chain reaction
  • Negligible power positively affecting the radiation situation around the device


  • Education and training:
  • Measurement of system multiplication capability
  • Measurement of neutron flux density distribution
  • Determination of lattice parameters
  • Determination of savings by reflector
  • Measurement with a pulsed neutron source
  • Application of noise analysis
  • Benchmark experiments
  • Development and testing of detection systems

Project schedule

September 2019 – April 2020 – positioning
May 2020 – July 2021 – construction
January 2022 – August 2022 – start of operation
September 2022 – December 2022 – full operation


The design and construction of the VR-2 reactor is supported by the project "Modernization of the Large Research Infrastructure VR-1 - Training Reactor for Research Activities (reg. nr. CZ.02.1.01/0.0/0.0/18_046/0015833 ) supported by Operational Programme Research, Development and Education co-financed from European Structural and Investment Funds and from state budget of the Czech Republic.