communications devices to keep him in touch with the rest of the boat. One of the newest pieces of equipment to be added is known as a multifunction display, mounted adjacent to his bunk. This marvelous device, which is tied into the BSY-1 combat system, is a red gas-plasma display showing data on position, course, speed, heading, and depth, as well as modes to show the current tactical situation around the boat. The advantage to Commander Jones is that he can wake for a moment in the middle of the night, reach over and check the boat's status, then roll over and go back to sleep-all without having to ruin his night vision by turning on a light or having to pick up a phone and talk to the OOD. He figures that not having to wake up fully several times is worth several hours' more sleep. And that can be life and death for the boat in a combat situation. A total of eight of these devices are located around the boat in such places as the control room and sonar room.
The Engine-The Reactor/Maneuvering Spaces
If you wander aft from the enlisted mess, past the forward escape trunk and down half a deck, you find the great divide on the
The first thing to understand about the nuclear reactor on a submarine is that it has only one real purpose, to generate heat to boil water into saturated steam. Other than that, all of the other parts of a nuclear submarine propulsion system are similar to any other type of steam-powered turbine plant. Its advantage over an oil-fired steam plant is the amount of energy concentrated in the nuclear fuel in the reactor core, as well as the complete lack of any need for air. On a weight and volume basis, nuclear fuel, such as enriched uranium, has several million times the amount of stored heat of a comparable amount of fuel oil. This concentration of energy is what makes all the dangers of handling nuclear fuel worth the trouble. In addition, because of the efficiency of the nuclear 'fire,' it is possible to build boiler plants that are considerably smaller than comparable oil-fired plants.
The process of nuclear fission is essentially quite simple. Imagine a floor covered with mousetraps. Each mousetrap has, mounted on the striker arm, two Ping-Pong balls. If we imagine a uranium atom as a mousetrap, it is holding on to a pair of attached particles called neutrons much like the Ping-Pong balls. Now if you drop another Ping-Pong ball onto one of the traps and trip it, two balls will fly into the air. This represents what happens when a neutron enters the uranium atom and strikes the nucleus: the atom splits and releases the two neutrons, releasing energy as heat. And when those two fall onto two more traps, these will trip and each throw two more Ping-Pong balls skyward. This will continue to double and double again until all the traps fire off their balls in one final fusillade. This same principle, whereby neutrons strike more and more atoms until all of them finally split, is called an uncontrolled or supercritical fission reaction. And this is what happens when an atomic bomb detonates.
But we don't desire an explosion, we want a slower reaction like a fire in a boiler. Imagine that in our room of mousetraps and Ping-Pong balls, we hang some monkeys from the ceiling. And we train them to grab one out of every two Ping-Pong balls when a trap goes off. This would allow the series of tripping traps to go on for a much longer time. And this is exactly what happens in a nuclear reactor. Instead of monkeys, a reactor uses what are called control rods (made of a neutron-absorbing material like cadmium or hafnium) set to absorb exactly the right amount of neutrons to bring the reaction into controlled or critical fission. This reaction still generates a great deal of heat, which is used to boil water into saturated steam to power the sub's turbines. In this way the same nuclear fuel that can cause a nuclear explosion in an instant can be used to power a ship for a period of years. And because of design procedures that have been tested over a period of decades, the fuel in the reactor cannot explode or even come close to doing so. The DNR takes great pride in the safety record of the boats with U.S.-designed reactor plants, which is perfect.
Most of the heat in the reactor is collected into what is known as the primary coolant loop. This is a series of pipes passing an extremely pure water-based coolant through the core of the reactor. This heat is passed through a heat exchanger to what is called the secondary loop. This is where the water for the steam turbine is actually boiled. Now, the steam created here is not the stuff you get from the tea kettle on your stove. This steam, which is under high pressure, is heated to literally hundreds of degrees and contains a great deal of motive energy. And this is the stuff that turns the turbine blades of the main engines, which feed into the reduction gears, which turn the propeller shaft and the propeller. Quite simple, really!
There are a few small problems with this system, though, and we need to discuss them. The obvious one is the question of how to protect the men aboard from the harmful effects of the reactor's radiation. As we mentioned before, the early Soviet nuclear boats scrimped on shielding and became cancer incubators for the naval hospitals of that now-defunct nation. The answer, in a word, is shielding. The entire structure surrounding the reactor compartment is layered with a variety of different shielding materials.
Between the reactor compartment and the forward part of the boat is a huge tank of diesel fuel, which powers the big Fairbanks-Morse auxiliary engine in the machinery compartment. As it turns out, that fuel is extremely efficient at modulating or absorbing the various subatomic particles that could damage human tissues. In addition, the entire reactor is contained inside a reactor vessel that looks like an oversized cold capsule on end. Surrounding this vessel, as well as inside of it, is a system of layered shielding. While the materials actually used are classified, it is easy to deduce that lead (an excellent gamma ray absorber) and chemically treated plastics (based on fossil fuels) are probably used extensively.
In addition to its extensive shielding, the entire reactor plant has been overengineered. Since its earliest beginnings, the DNR has insisted that naval reactors be built with extremely high safety margins. While DNR will not comment, for example, upon just how much pressure all of the reactor plumbing can take, it is generally acknowledged that the entire reactor plant has been built several hundred percent more robustly than is required (400 percent to 600 percent has been mentioned). In addition, every system has at least one backup and usually an extra manual backup on top of that. The legacy of the
Another area of extreme secrecy is the exact configuration and design of the reactor core itself. In fact, other than the technology used to reduce radiated noise, nothing on the
Around the core circulates the coolant of the primary loop, which feeds the heated coolant into a steam generator. The steam generator directs its steam into a secondary cooling loop, which feeds a pair of high-pressure
