Get Your Free Neutrons at ORNL!

Dr. Jim Freels - Oak Ridge National Laboratory, Oak Ridge, TN

Right now, the High-Flux Isotope Reactor is one of the most powerful research reactor facilities in existence. Established in the 1960s, its unique design currently uses moderated nuclear fission to produce free neutrons for researchers and industrial users.

The neutrons are termed "free" because they exist outside the nucleus of atoms after reactions break them into subnuclear constituents: protons, electrons, and antineutrinos. Being electrically neutral, the free neutrons penetrate deep because they pass unhindered through electrical fields within atoms and slow primarily when they collide with atomic nuclei. With only one proton and neutron encased in its nucleus, hydrogen makes an excellent refrigerant for the fast-moving free neutrons.

At HFIR, neutron production is most intense in the hot center of the 2-foot diameter reactor core, where rare isotopes such as californium-252 form. HFIR collects whatever free neutrons from outside the core to produce a dense or "bright" flux for scattering studies and other experiments at a new beam facility named HB-4. When their new low-temperature hydrogen system comes on line to cool the neutrons, the flux coming out of this beam tube to experimental equipment will be as slow and bright as the current best in the world.