With the end of World War II, the furious push for nuclear development came to a sudden halt. The scientists, engineers, and technicians were tired, and as a group they experienced the depression that can come from the completion of a huge task and the unique dread of having built unusu­ally ferocious weapons. Many workers at Los Alamos, having performed their duty, returned immediately to their lives in academia or industry. Some lingered. Robert Oppenheimer, director of the lab, remained a year and then resigned to return to the Institute for Advanced Studies at Princeton and to become chairman of the general advisory committee for nuclear project funding and laboratory construction. Enrico Fermi, inventor of the nuclear reactor, went back to teach at the University of Chicago.

The Hanford Works in Washington State kept turning out plutonium by the ton, and the gaseous diffusion plant at Oak Ridge, Tennessee, now running at full capacity, started producing bomb-grade U-235, even though there were no plans to build another uranium bomb. The Fat Man design was improved, and a few MK III plutonium implosion devices were assembled, in case of renewed global hostilities. Although building an electrical power plant using the vast wealth of knowledge and experi­mental data gained during the war seemed a logical idea, it was an idea for the future, and there was no immediate push to civilize the weapons work or to move on to public service applications. In comparison to the

effort of building a nuclear-based power plant, a bomb seemed simple. “Little Boy,” after all, had exactly one moving part, and it had cost $1.8 billion to build it. A nuclear plant would have turbines, pumps, and valves of all descriptions, electrical controls and monitors, and it would have to be taken apart to refuel it. The machinery would have to be safe enough to run in populated areas without disruptive accidental radiation releases. It was easier to build a nuclear device that would spread radiation than to build a nuclear device that would not spread radiation.

This atmosphere and attitude of not rushing into anything lasted only briefly, and soon there was a push for nuclear power and even a com­petition among the United States, the Soviet Union, Canada, and Great Britain to tame the wartime technology, and all would eventually claim to have built the first nuclear power plant. The four countries would have different approaches to similar goals, and it is interesting to see the results of the race for atomic power.

THE BUILDING OF THE NAUTILUS2

Of all the possible applications for nuclear power that tantalized scientists in the early days of development, from nuclear spaceship propulsion to heating an Antarctic station, the most sensible, immediate application was to power a submarine. Submarines in World War II were only mar­ginally capable of submerging for a few hours, operating slowly on batter­ies or near the surface on diesel engines sucking air through a snorkel sticking above the water. A submarine desperately needed a power source that would require no air and expel no exhaust. With such an engine, a submarine could operate indefinitely under water, and all the military advantages of submersion, stealth, speed, and safety could be used to full advantage. The navy, after an initial recoil from such radically new con­cepts in 1939, had begun to see the obvious advantages of nuclear power in 1940, but the army’s bomb program took supreme priority and command of nuclear matters and confiscated the navy’s thermal-column uranium enrichment facility for use at Oak Ridge.

At the end of the war, the U. S. Navy had 1,000 ships sitting idle, qui­etly rusting away at anchor. The world had just finished a long and costly crisis, and there were other needs to be met. Europe and Japan were in ashes and would need to be rebuilt; Great Britain was starving; and returning soldiers in the United States were jobless. There was also the inconvenient problem of uranium stockpiles. The United States had none to speak of. All the uranium in stock had been bought from Canada and from Belgian companies operating in the Congo, or had been seized in Germany from mines in Czechoslovakia. There was no clear source of uranium for the United States without dealing with touchy international situations. All uranium stocks were frozen, dedicated to future atomic bomb production.

Captain Hyman Rickover (1900-86) of the U. S. Navy was among the first to push for the development of a nuclear-powered submarine. Rickover was ambitious, creative, and tireless. He was also controversial, iron-fisted, and impatient with normal naval channels as a way of doing things. He was a master of the vituperative report, and he drove men and machines to the breaking point. He was famous, in naval circles, as a man who could “get the job done,” and he believed that the shortest path was a straight line, even if it cut through several admirals. He had been assigned to a post at Oak Ridge to study nuclear topics, and the concept of a nuclear submarine stuck him as an idea whose time had come. He formed a group of like-minded men at the Oak Ridge Laboratory, “The Naval Group,” composed of himself, Lieutenant-Colonel James H. Dunford, Lieutenant — Colonel Miles A. Gilbey, Lieutenant-Colonel Lou Roddis, and Lieutenant Ray Dick. It would require an enormous, seemingly superhuman effort, but this determined group would convince the navy, the Atomic Energy Commission (AEC), Westinghouse, General Electric, the Congress, and the general nuclear physics community that a nuclear submarine should and would be constructed, and it should be a priority project.

The technical problems were small compared to bureaucratic prob­lems, but they were still formidable, and the solution of these problems would affect all future application of nuclear power. At the time, in 1946, a nuclear reactor, or “pile,” was assumed to be built using blocks of graphite. Graphite is a fine neutron moderator, having a very small neutron cap­ture probability, and low-grade “natural” uranium can be used as fuel. Graphite is a solid and will neither boil away nor leak. A problem with a traditional graphite pile is that it is huge. The graphite power reactors at the Hanford Works fit in buildings the size of gymnasiums. A submarine, on the other hand, is a slender steel tube, designed to move through water. A graphite pile would simply not fit in even a large submarine, which was only 28 feet (8.5 m) in diameter. The reactor would have to be a completely different design and could not be a modification of a research reactor or a plutonium production facility. An alternate type of moderator material, allowing a small reactor core, would have to be found and proven.

The army, as owner of all the Manhattan Project facilities and every piece of nuclear material and researched knowledge, took a progressive move in April 1946. The Oak Ridge Laboratory was run by the Monsanto Company and the postwar director of the lab was Dr. Farrington Daniels (1889-1972), professor of chemistry at the University of Wisconsin. Dan­iels proposed that Monsanto, working for the army, build a demonstration industrial pile at Oak Ridge as a prototype civilian nuclear power plant. It became known as the Daniels Pile, and work began immediately, to be completed within 18 months.

Rickover’s group watched the Daniels Pile initiative spiral out of con­trol quickly and lose progress. Learning from this observation, the navy team decided to begin anew, designing their naval reactor backward. Instead of starting with the design of the uranium core, they began with the propeller shaft on the submarine. To move a submarine hull underwa­ter faster than a destroyer could run, they needed 10 megawatts of high — temperature steam directed into twin, multistage turbines, turning the two propellers. Another requirement for this reactor was unique: It would be enclosed in a metal tube with a crew of sailors, and they must be able to stay in the tube for an unlimited time without being subjected to harmful radiation. No radioactive substance, such as fuel, fission products, radio­active gases, or contaminated coolant could have the slightest leak into the submarine. This was a difficult proposition. Nobody had been killed by the big power reactors at Hanford, so far, but when one was running at full power no one could be near it. Moreover, the reactor had to have an inherently safe character.

The leakage of water from the primary cooling system, such as that caused by the failure of a pump or a valve, would result in a loss of moder­ator. The dual purpose of the water in the reactor, as both moderator and coolant, meant that losing water was losing moderator. With the modera­tor gone or reduced in volume, the fission process could not continue. The reactor shuts down and cannot be restarted, and this is considered a safe condition for a nuclear system with broken hardware. This was not neces­sarily a characteristic of the big graphite reactors. Lose the water coolant through a pipe rupture or boil-off and the reactor would go supercritical because the graphite alone was a better neutron moderator than graphite with water running through it.

As an additional requirement, the reactor had to be able to run for years at full speed without refueling, unlike the graphite piles. Using nat­ural uranium, the fuel in a graphite reactor had to be almost constantly replenished, pushing new fuel in one side of the pile with spent fuel falling out the other side of the pile, on a weekly basis.

Working in reverse, the submarine design continued from the turbines to the steam generator, with sizes and weights determined by the volume and pressure of steam needed to provide the specified power. The steam generator, or boiler, needed a source of heat. The source of heat was the combination coolant and moderator for the reactor core.

Instead of assuming that there would be no uranium fuel, Rickover assumed that there would be plenty of fuel. The United States is a big, wide country, and there had yet to be a comprehensive survey of avail­able uranium deposits. Given unlimited uranium reserves, a submarine could run on enriched fuel, made 50 percent U-235 in the diffusion plant at Oak Ridge. Given the high concentration of fissile U-235, graphite or any other high-efficiency moderator was not necessary. Ordinary or “light” water would be sufficient. The neutron slowing-down distance for the hydrogen in ordinary water is unusually short, so the core could be very small, the size of a garbage can. Water was well understood, easily pumped and managed, transparent, and liquid under pressure, regardless of the temperature. Liquid water under pressure, pumped in a tight loop through a reactor core, is both the coolant and the moderator. Lose cool­ant through mishap, and the reactor shuts down, because moderator is lost. Any fission-products or broken fuel are confined to this tight, inner loop of water, so everything on the other end of the power plant, from the steam generator to the turbines and the condenser, is isolated and free of potential radiation contamination.

One thing that Rickover had learned from his service on creaky, prewar undersea vessels was how not to design a submarine, and his plan, now named Nautilus after the craft in Jules Verne’s Twenty Thousand Leagues Under the Sea, would be safe and solid. The reactor plant would be inher­ently foolproof, free from possible criticality excursions, with far more strength than was necessary in all important components. Every piece of technical equipment on Rickover’s submarine would be built to shock and vibration specifications, with verification through physical testing.

Official approval for his submarine project in the navy would require the highest official approval, and Rickover decided to shorten the tedious chain of command, writing a letter directly to Fleet Admiral Chester Nimitz (1885-1966), decorated hero of World War II, former commander in chief of the Pacific Ocean areas, now chief of naval operations, and the navy’s principal expert on submarines. Writing a letter to Nimitz was

hardly a trivial matter, and even though directly addressed it still required approval and rewriting all up the line, from Rickovers captain level up to fleet admiral level. It took Rickover two months to build the letter and send it through official channels. Finally, on December 5, 1947, the letter reached Admiral Nimitz.

Nimitz was fascinated by the details of the proposed project. He signed the letter immediately, approving the program to build a nuclear-powered submarine. Still, much work was needed to persuade both the navy and the AEC that Nautilus should be built, but on May 1,1948, the concept had full approval. On August 2, Rickover formed the nuclear power division of the Bureau of Ships and re-collected his naval group from Oak Ridge. The Westinghouse Corporation was chosen to design a most critical part of the system, the steam generator, under an $830,000 contract.

Technical problems in Nautilus were interesting and numerous, and their solutions would forever guide the nuclear power industry. An exam­ple was the production of zirconium. It was found early on that zirconium was ideal for internal structures of a submarine reactor. It could with­stand high temperatures and did not absorb neutrons. Unfortunately, it was a rare material, more precious than platinum. They would need a lot of it for one reactor. A metallurgist broke the news of its cost to Rickover. It would be more than $1,000 per gram.

“My God,” Rickover said, “$1,000 a gram is $450,000 a pound. A half a million dollars a pound! . . . What’s the problem?”

The problem, explained the metallurgist, was that all the zirconium in the United States could be put in a shoe box.

“Well, we’ve got to step this thing up,” replied Rickover. “From now on you call me Mr. Zirconium, because I am going to get this stuff produced by the ton.”

And so he did. By 1952, zirconium was being mined, milled, and pro­duced in quantity and at low price, by Westinghouse. Asked by a congres­sional committee how in the world they managed to get the machinery and the expertise to make zirconium so quickly, the Westinghouse rep­resentative replied, “Rickover made us get it.” The zirconium exercise almost made the procurement of hafnium, a rare metal resistant to high temperature and perfect for the Nautilus control rods, seem simple.

With technical issues resolved, the first submarine reactor was built in 1952 by Westinghouse and the Electric Boat Company of Groton, Con­necticut, but it was nowhere near the ocean. It was built in a simulated ocean, a spherical building 18 stories tall, 225 feet (69 m) in diameter, filled with seawater and named the “Hortonsphere.” Located in the wilds of Idaho, near the town of Arco at the AEC’s Desert Test Station, the con­struction was a tightly held military secret. Those of little faith believed that an experimental reactor should be built where it could explode harm­lessly, and Rickover believed that it should be proven in a simulated sub­marine hull, completely under water.

The development of Rickover’s submarine reactor would have a pro­found effect on future nuclear power plant design in the United States. As the state of nuclear power production stands today, most of the reactors in the United States and in the world are based on the equipment in Hyman Rickover’s submarine, the Nautilus. The choice of moderator and coolant, reactor tank configuration, piping, safety systems, controls and monitors, exotic materials used, and even operator training are all directly con­nected to the navy’s first nuclear submarine program. The result is com­pact machinery, overbuilt for stamina, expensive, highly reliable, and safe to operate. The nuclear power program for the United States and most of the world was thus designed in reverse, starting with a highly specialized system, built to fit in a small space, with price being no object and using enriched uranium fuel, instead of first building a plant spread out over many acres, using readily available machinery and materials and the most inexpensive form of fuel. There would be other designs, but for better or

worse, this is the system that Rickover gave the nuclear industry. The navy reactor is known as the pressurized water reactor, or the PWR. It is the most licensed, copied, and stolen reactor plant design in the world.

The keel of the Nautilus, hull number SSN-571, was laid on June 14, 1952, at the shipyard in Groton, Connecticut. The president of the United States, Harry S. Truman, was present, as were the secretaries and chiefs of the armed forces, the governor of Connecticut, the chairman of the AEC, lesser officials of all types, and Hyman G. Rickover. The radical new vessel was launched into the Thames River on January 21,1954. It took 10 months to install the nuclear power equipment, and at 11:00 a. m. on Janu­ary 17,1955, she put to sea under Captain Eugene R Wilkinson (1918- ).

The age when uranium fission would be used for something other than explosives had begun.