This 1979 photo is of a woman at the U.S. Department of Energy's Lawrence Livermore National Laboratory (LLNL) opening a 97,000 pound (48.5 ton) door. Eight feet thick and nearly twelve feet wide, this concrete-filled door included a special bearing in the hinge that allowed a single person to open or close it. The door was used to shield the Rotating Target Neutron Source-II (RTNS-II), which scientists used to study the properties of metals and other materials that could be used inside theoretical fusion power plants.

Photo credit: U.S. Department of Energy, Lawrence Livermore National Laboratory.