It can operate at a maximum thermal power of 250 MW and has a "Four Leaf Clover" core design (similar to the Camunian rose) that allows for a variety of testing locations.

In addition to its role in nuclear fuels and materials irradiation, the ATR is the United States' only domestic source of high specific activity (HSA) cobalt-60 (60Co) for medical applications.

[2] Its primary function is to intensely bombard samples of materials and fuels with neutrons to replicate long-term exposure to high levels of radiation, as would be present after years in a commercial nuclear reactor.

[5] This status is intended to stimulate experiments to extend the life of existing commercial reactors and encourage nuclear power development.

Through the NSUF system, ATR and partner facilities have hosted 213 awarded experiments from 42 different institutions (universities, national labs and industry), resulting in 178 publications and presentations.

[4] Because of their large size and stored energy, commercial reactors require a robust "containment structure" to prevent the release of radioactive material in the event of an emergency situation.

[4] The reactor vessel itself, which is made of stainless steel surrounded by concrete that extends more than 20 feet (6.1 m) underground, is hardened against accidental or intentional damage.

It verified for reactor designers the effectiveness of control mechanisms and physicists predictions of power distribution in the large core of the ATR .

Low-power testing in the ATRC conserved valuable time so that the large ATR could irradiate experiments at high power levels.