Heavy water is used as a coolant and moderator by some of these devices.
A scale ranging from zero cents to a dollar measures the activity of these devices. SCRAM mechanisms are safety measures used with these devices. A fudge factor literally called the "fudge factor" is used to calculate their critical masses. The first of these devices was built on a squash court underneath the University of (*) Chicago football field. Heavy water is used as a coolant and moderator by some of these devices. They have control rods made out of boron to absorb neutrons. Those rods usually surround a fuel composed of uranium-235 or plutonium-239. For 10 points, name these devices which produce energy through nuclear fission.
A scale ranging from zero cents to a dollar measures the activity of these devices.
nuclear reactors [or nuclear power plants; or similar answers; or nuclear piles; prompt on reactors; prompt on nuclear bombs or nuclear weapons or similar answers]