National Geographic : 1962 Aug
KODACHROMESBY NATIONALGEOGRAPHICPHOTOGRAPHERJOHN E. FLETCHER The heart of the plant is a core of uranium fuel-813,440 pellets of uranium oxide en riched with uranium 235 (page 284). Boron steel control rods absorb excess neutrons when the nuclear fire is damped. Withdrawal of these rods by remote control allows more neutrons to flash through the reactor. When a hurtling neutron collides with a uranium nucleus, the nucleus splits-"fis sions," to use the technical term. The two parts weigh less than the whole did, and the lost fraction has become stupendous energy in the form of heat. This heat is absorbed by water under pressure-nearly 2,000 pounds to the square inch-inside a closed primary system, self-contained to let no water out. Because it lies under so great a pressure, this water does not boil. Instead, it passes on its heat to water in a secondary system, which boils to form tremendous amounts of steam. This secondary-system steam drives huge turbines that transfer their energy to the pro peller through reduction gears. The pay-off is 22,000 shaft horsepower for an infinitesimal expenditure of fuel. Sea Pioneers Run Nuclear Engines I wanted to go down to the engine room to get the feel of things there, and began in the glassed-in gallery where future passengers will be able to see into the fantastic air-con ditioned control room. On watch at the con sole (where the only word of the new nuclear language I readily understood was SCRAM, which means shut down the reactor in a hurry) sat three strong-faced young men in 293 N.G.S.