The so called High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) in Tennessee was refueled a few weeks ago, and the lab posted great images of the process. And what images!


The luminescent blue glow, caused by a phenomenon called Cherenkov radiation, was caught on camera, making the reactor looking like a spectral weapon from a science-fiction movie.

HFIR is a research reactor at ORNL, but it is also used for the production of isotopes for research, industrial and medical applications, isotopes such as californium-252 and other transuranium isotopes. What can we see in the photos below? ORNL explains:

The High Flux Isotope Reactor at Oak Ridge National Laboratory is the highest flux reactor-based source of neutrons for research in the United States, and it provides one of the highest steady-state neutron fluxes of any research reactor in the world. Operating at 85 MW, an average fuel cycle for the HFIR generally runs for approximately 26 days—depending on the experiment loading for that cycle—followed by a refueling and maintenance outage for various scheduled calibrations, modifications, repairs, and inspections. The reactor underwent routine refueling in July 2015, as seen in these photos. While submersed, the spent fuel emits a luminescent blue glow due to Cherenkov radiation, in which shedding electrons move through the water faster than the speed of light. Once removed from the reactor, spent fuel is then relocated into an adjacent holding pool for interim storage.


The end-of-cycle spent fuel elements in the HFIR vessel prior to removal. This is a view of the reactor core.

Photo: Genevieve Martin/ORNL

Here we see the removal of a HFIR fuel element as it passes through a hatch in the top head of the reactor vessel during defueling operations.



Photo: Genevieve Martin/ORNL



Spent fuel in the HFIR pool storage array.


Photo: Jason Richards/ORNL

The control room at the High Flux Isotope Reactor.


The flux trap of the High Flux Isotope Reactor (HFIR) at the center of the reactor’s fuel element. This is the area of the reactor in which target materials are irradiated to produce specialized isotopes.


Photo: Jason Richards/ORNL

The reactor pool at the High Flux Isotope Reactor


Photo and caption: Oak Ridge National Laboratory

