The heart of the HT3R facility is the reactor core, which supplies process heat for the experimental energy research labs and neutron and gamma radiation for the radiation laboratories. Inside the core is also the location where samples will be irradiated. It is also the subject of the most public concern, since the few people know the key advances that the last 30 years have brought to the science of nuclear power.
The key safety feature of the reactor is its high-temperature design. As displayed in the video below, the nuclear reactions which sustain the core are caused by the neutrons scattering around inside the core. As the core heats up, the quantum wavelength of these neutrons shrinks and so does their probability of causing a fission event. This causes more of the neutrons in the core to escape into the surrounding shielding material, where they are simple absorbed, and lower the reaction rate. The nuclear reaction essentially quenches itself, making it unnecessary for the operators to intervene in order to keep the reactor from reaching unsafe temperatures. The basic physics which causes the reactor to operate now also prevents it from coming closer than about 800 degrees Fahrenheit below the safe temperature of the tiny Tristructural Isotropic (TRISO) fuel beads which power the reactor.
The basic physics which causes the reactor to operate now also prevents it from coming closer than about 800 degrees Fahrenheit below the safe temperature of the tiny Tristructural Isotropic (TRISO) fuel beads which power the reactor. These beads contain all the fission byproducts inside a shell of high-temperature ceramic. Their sub-millimeter size and spherical shape give them very high mechanical strength (imagine trying to squish a grain of sand) so that they may safely contain all but traces (constantly filtered from the coolant) of fission byproducts. Even in the event that coolant was lost from the reactor, the helium coolant (helium itself cannot become radioactive as it passes through the core, hence its choice as a coolant gas) would be inert and non-radioactive. The HT3R facility will revise the very notion of safety in nuclear reactors because it was designed to make the worst imaginable scenarios impossible to occur.