The story picks up in the spring of 1953, when construction of the “Mark I” was completed. But "many serious problems” remained, and we'll let Kintner take it from here:
The pumps and valves and heat exchangers, turbines, electrical generators, thermometers, control panels—all the many hundreds of items which made up the complex and interrelated systems of the plant—had been mechanically and electrically tested until they were as nearly perfect as they could be made. The crews had practiced for a week at carefully opening the main turbine throttle from an oil-fired boiler so as to disturb the reactor as little as possible. They were rehearsed in casualty drills, and STR Mark I was ready for an attempt at power operation.
Captain Rickover, who had followed preparations on an hourly basis, flew to Idaho in company with Atomic Energy Commissioner Thomas E. Murray, a man who had contributed much support to the Navy's nuclear propulsion program and who was to have the honor of opening the turbine throttle valve, admitting steam generated by a power reactor into a turbine for the first time. Murray knew that eight years had passed since Hiroshima and that, except for the Navy's program, no U.S. atomic power project was anywhere near fruition. He knew also that the Navy and the AEC were committing almost one quarter of a billion dollars to the project whose success was now to be determined.
That first operation was amazingly successful. After a two-hour run, during which power levels of several thousand horsepower were achieved, the reactor was shut down. Six years of study, organization, planning, conniving, fighting for funds, building laboratories, manipulating people, developing new materials and devices had paid off. The first day of Mark I had surprised its most optimistic proponents.
There were many happy people in the Idaho desert the night of May 31, 1953. The happiest was Captain Rickover, who had had the vision, constantly forced the program against opposition, and provided the technical judgment to steer it through areas far beyond those previously known.
Then followed a month of careful, precise building up in power level. Test operations went on night and day, seven days a week. Power was increased in small steps. What could happen on these increasing steps could only be conjecture until the trial run had been completed. Every man at the desert site knew the danger associated with each increase in power.
The first feasibility question to be answered affirmatively was that of safety. Mark I turned out to be a calm and stable machine and even when treated roughly, as its inexperienced operators often treated it, showed no tendency to become an atomic bomb. There was no indication of any dangerous overheating in the reactor fuel elements. The shield designers were surprised to find that radiation levels were less than half of those which they had calculated, indicating that the Nautilus could easily carry her radiation shield. As additional physics data became available, the estimate of reactor life was greatly increased.
The major difficulty was with the numerous safety circuits, any one of which could cause the reactor to shut down suddenly. These circuits were meant to be extremely tender in their operation; they were, in fact, so sensitive as to provide a serious difficulty to the operators. A submarine propulsion plant not capable of operating without emergency shutdowns under sea motion and depth-charge attack would not be satisfactory, yet the Mark I had a constant plague of "scrams" from such slight causes as vibration from a crew member's walking through the reactor compartment or a bolt of lightning striking a Montana power line three hundred miles away.
As the crew gained operating experience, and as additional information was obtained concerning safety, the number of signals causing "scram" was selectively reduced to less than twenty. By this means, and by intensive crew training, the problem was licked. As a result, the Nautilus experienced very little difficulty of this sort.
On June 25, 1953, full design power was reached. Not one part of the plant indicated failure to meet the rigid specifications. In less than a month after power generation by the world's first nuclear power plant, Mark I was running smoothly at its maximum rating. The one remaining question was whether the machinery could withstand long high-power running.
The operating crews began a forty-eight-hour test at full power to obtain important physics information. At the twenty-four-hour point the data obtained seemed sufficient, and the engineers intended to shut down the plant. Rickover, who was at the site, inadvertently learned of this plan and immediately overruled it. He had visualized that if the forty-eight-hour run turned out well, they should continue on a simulated cruise across the Atlantic. He reasoned that such a dramatic feat, if successful, would end the doubts in the Navy that nuclear power was a feasible means for propelling ships. It would give the project the momentum and breathing space needed to carry on the development without constant harassment until the Nautilus could get to sea.
I was the senior Naval officer at the site. I felt that extension of the run was unwise considering the many uncertainties, and told Rickover that beyond forty-eight hours I could not accept responsibility for the safety of the $30 million prototype. Rickover directed me to proceed with the simulated voyage.
Charts of the North Atlantic were posted in the control room and a great-circle course to Ireland plotted. The position of the ship after each four-hour watch was computed and marked on the chart. For watch after watch, the course plotted in the control room crawled toward Ireland. No submarine had covered more than twenty miles submerge at full speed. A propulsion unit, even for a surface ship, need steam only four hours at a full power to obtain acceptance for Naval use.
At the mid-point of the Atlantic crossing, the operation seemed to be going well. As one of the Nautilus crew members standing watch in the hull state, "She just sits there and cooks." A veteran marine engineer, familiar with the large quantities of fuel oil which would have been required to drive a ship so far with a conventional propulsion plant, pointed to the propeller shaft and then to the reactor and said, "So much comes out back here, and nothing goes in up there!"
At the 60th hour, however, difficulties began. Carbon dust from the brushes depositing in the windings caused difficulty in the vital electrical generating sets. Nuclear instrumentation, operating perfectly at the beginning of the run, became erratic, and the crews could not be sure what was happening within the reactor core. One of the large pumps which kept the reactor cool by circulating water through it began making a worrisome, intermittent whining sound. We had not had any check on "crud" build-up; we feared that heat transfer would be so reduced by this point that the core would burn up. The most pressing problem, however, was caused by the failure at the sixty-fifth hour of a tube in the main condenser into which exhausted turbine steam was being discharged. Steam pressure fell off rapidly.
The Westinghouse manager responsible for the operation of the plant strongly recommended discontinuing the run. In Washington, the technical directors of the Naval Reactors Branch was so concerned that he called a meeting of all its senior personnel, who urged Rickover to terminate the test at once. But the Captain was adamant that it should continue until an unsafe situation developed. "If the plant has a limitation so serious," he said, "now is the time to find out. I accept full responsibility for any casualty." Rickover had twice been passed over by Naval selection boards for promotion to Rear Admiral. As a result of congressional action, he was to appear within two weeks for an unprecedented third time. If the Mark I had been seriously damaged, Rickover's prospects for promotion and his Naval career were ended.
The tensions surrounding the test increased the challenge to the crews, and as each watch came on duty it resolved it would not be responsible for ending the run prematurely. Crew members worked hard to repair those items which could be repaired while the plant was in operation.
Finally, the position indicator on the chart reached Fastnet. A nuclear-powered submarine had, in effect, steamed at full power non-stop across the Atlantic without surfacing. When an inspection was made of the core and the main coolant pump, no "crud" or other defects which could not de corrected by minor improvements were found. It was assured that the Nautilus could cross an ocean at full speed submerged.
A month after nuclear power was first produced, the most doubting among those who had participated in the STR project knew that atomic propulsion of ships was feasible, that it was only a matter of time before the technology developed for Mark I would bring about a revolution in Naval engineering, strategy, and tactics. We knew, too, that industrial nuclear power could be built on the same technological foundations. The Pressurized Water Reactor at Shippingport, Pennsylvania—the world's first solely industrial power reactor—was in fact developed from STR experience under Admiral Rickover's direction.
To those of us who had participated in the STR project, who knew how many chances were taken, how far previous engineering knowledge had been extrapolated, the fact that all the unknowns had turned out in our favor was a humbling experience. Rickover, paraphrasing Pasteur, put it this way: "We must have had a horseshoe around our necks. But then Nature seems to want to work for those who work hardest for themselves."
STR Mark I is now a flexible facility providing much of the experimental information for the Navy's nuclear propulsion program, which today includes thirty-three submarines, a guided missile cruiser, and the first nuclear-powered aircraft carrier. It provides the practical training for all the hundreds of officers and enlisted men who will man our nuclear fleet. The courage, the will, the judgment and resourceful which went into STR Mark I have made the United States Submarine Nautilus an outstandingly successful venture in man's long struggle with nature.