The second nuclear reactor to power up at INL, the Materials Test Reactor (MTR) was used to conduct research on the materials inside of commercial power reactors. When the nuclear industry was just getting started, not a lot was known about how high levels of radiation would affect the metals and components that would be used in reactors. The MTR was an essential test bed for conducting fundamental research in this area.

The high-flux radiation fields available in this reactor made it possible to accelerate the screening of potential reactor materials. In its early years, the MTR contributed to the design of pressurized water, organic-moderated, liquid-metal-cooled, and other reactors. Successful operation of the MTR itself was a great experiment resulting in a family of plate-type reactors. The reactor operated at a power level of 30 megawatts until September 1955 when thermal output was increased to 40 megawatts.

Proving the Principle, Susan M. Stacy