Nuclear Science


High Flux Isotope Reactor

The High Flux Isotope Reactor (HFIR) first achieved criticality on August 25, 1965, and achieved full power in August 1966. It is a versatile 85-MW isotope production, research, and test reactor with the capability and facilities for performing a wide variety of irradiation experiments and a world-class neutron scattering science program. HFIR is a beryllium-reflected, light water-cooled and moderated flux-trap type swimming pool reactor that uses highly enriched uranium-235 as fuel.  HFIR typically operates seven 23-to-27 day cycles per year.

Irradiation facility capabilities include

  • Flux trap positions: Peak thermal flux of 2.5X1015 n/cm2/s with similar epithermal and fast fluxes  (Highest thermal flux available in the western world.)
  • Instrumented  reflector positions:  Peak thermal flux of 1.0X1015 n/cm2/s with similar epithermal and fast fluxes
  • Uninstrumented reflector positions:  Thermal fluxes of 1.0X1015 n/cm2/s ranging down to  1.0X1014 n/cm2/s in the outermost positions
  • Two complimentary pneumatic tubes that shuttle samples from the core to the HFIR Neutron Activation Analysis (NAA) Laboratory
    1. PT-1: 2.8×1014 n/cm2/s (Thermal/Epithermal = 40)
    2. PT-2: 5.9×1013 n/cm2/s (Thermal/Epithermal = 200)
  • Gamma irradiation Facility maximum dose rate: 1.0×108 R/hr


  • Thermal and cold neutron scattering science
  • Isotope production
    1. Californium-252
    2. Other transcurium isotopes for R&D
    3. Lighter isotopes that require high flux for production
  • Fission and fusion reactor materials irradiation studies
  • Advanced reactor fuels irradiation studies


Reactor type Beryllium reflected, light water cooled and moderated, flux-trap type reactor
Fuel Highly Enriched Uranium-235
Thermal neutron scattering instruments 3 horizontal beam tubes serving 7 instruments
Cold neutron scattering instruments 1 horizontal beam tube serving 5 instruments
Flux trap region irradiation positions 30 target positions, 6 peripheral target positions
1 hydraulic rabbit facility position
Reflector region irradiation positions 42 vertical irradiation positions
2 slant positions on reflector periphery
Materials Irradiation Facility This facility supports instrumented and/or gas cooled experiments
-2 flux trap positions
-8 reflector positions (removable reflector)
Neutron Activation Analysis 2 pneumatic tubes shuttle samples from the  NAA Lab to the reflector region
Gamma Irradiation Facility In spent fuel flux trap

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