"Everything went quite well as long as a mechanic from Augsburg and an engineering school professor were permanently on hand.”

—a note from an early diesel engine owner to Rudolph Diesel, 1898

Canada was showing great initiative, independence, and creativity in their evolving quest for nuclear power at Chalk River in the 1950s, but whatever they were doing, the United States was doing it larger, faster, and in dazzling variety. Experimental projects, trying new and previously unheard-of ways to build atomic piles, were underway in Illinois and New Mexico, while plutonium and enriched uranium were being produced by the ton in Washington State and Tennessee. Europe was behind but gathering speed in England, France, and the Soviet Union.

In a rare fit of post-war brilliance, the government of the United States decided to relieve the military services of research, development, manufacturing, testing, and ownership of any nuclear weapons or power systems, beginning January 1, 1947. Everything having to do with nuclear reactions, including facilities, access roads, employees, and waste dumps, was transferred from the Army Corps of Engineers to a new federal agency, the Atomic Energy Commission, or the AEC. The Navy would own the nuclear submarine Nautilus, but the engine and the fuel would belong to the AEC. If you kicked up a rock in your back yard and it was carnotite, a uranium ore, it belonged to the AEC. David Lilienthal was appointed chairman. Lilienthal had proven his mettle by keeping both hands around the throat of the Tennessee Valley Authority as it evolved from a make-work project under President Franklin Roosevelt into a major source of electrical power. Piloting this new agency was no easier than controlling the TVA. The AEC was tasked with promoting world peace and improving the public welfare while developing weapons that could return civilization to low-population Stone Age conditions in a few seconds.

In 1949 the AEC decided that the public welfare could be improved by moving all of the experimental nuclear reactor developments to the middle of nowhere in Idaho. Montana had been considered for the site, but there was plant life and some animals scattered around in it. Roughly in the middle of Idaho, between Arco and Idaho Falls, was a flat desert resembling the surface of the moon. It even had craters, left over from its tenure as the Naval Proving Ground

during the war.92 Frankly, if a reactor experiment happened to go rogue and self-destruct, there was not much there to be harmed, and it was good practice to concentrate all the dangerous stuff in one place. The new facility was named the National Reactor Testing Station, or the NRTS, and its headquarters was built in Idaho Falls.

With more than 50 prototype reactors and some large-scale chemistry experiments, personal safety at the NRTS was not bad. There were a couple of meltdowns and three steam explosions that were considered to be accidents. Two of the blow-ups were staged events that happened to have larger effects than were expected, but one, the infamous SL-1 incident, was the strangest and most tragic reactor accident in American history. Lessons were learned and stringently applied in most cases. The causes of these unfortunate incidents were all over the map, and their listing does not necessarily help us pin down anything we saw in Canada as the universal reason for problems using nuclear fission.

The first accident at the NRTS involved the Experimental Breeder Reactor One, or the EBR-I, in 1955. EBR-I was an odd piece of atomic enthusiasm. It was designed in 1949 at the Argonne National Laboratory in suburban Chicago with the encouragement of Dr. Enrico Fermi, the Italian who conceived the CP-1 pile back in ’42 and the pontifex maximus of reactor physics. The design team was led by Walter Zinn, a nuclear physics Ph. D. from Canada. When the CP-1 was started up at the University of Chicago on December 2, 1942, Zinn was responsible for withdrawing the safety control rod, called the “zip.” By 1946 he was the head of the Argonne Lab, in charge of all the nuclear reactor research in the United States.

The importance and omnipotence of Walter Zinn’s monopoly was felt by the other labs still standing after the war. The Singing Oak Ridge Physicists expressed their feelings with this song at the 1947 Christmas party, to the tune of Deck the Halls:

Pile research is not for us’uns.

Fa la la la la, la la la la.

Leave it to our Argonne cousins.

Fa la la la la, la la la la.

Engineering is for we’uns.

Fa la la la la, la la la la.

We’re a bunch of dirty peons.

Fa la la la la, la la la la.

Zinn was comfortable at Argonne, but just as the breeder reactor design started to gel, this and every other reactor construction project was moved to Idaho, which some people came to know as “Argonne West.”

At the time, there was not a single electrical-power-producing reactor in the entire world. All the piles were used either for plutonium production or as neutron sources for research. Uranium mining out west was a small enterprise, usually involving old vanadium mines, and the thought of relying on Canada or the Belgian Congo for the fuel to run the industrial economy of the United States was not attractive. There simply was no promise of enough uranium to do anything but make bombs and run a few submarines. Rickover’s nuclear sub fuel was expensive, exotic 50- percent enriched U-235 from the still-top-secret gas diffusion plant at Oak Ridge, and there was no way that commercially competitive power could be produced by burning it in a privately owned pile.

Backing up at Oak Ridge by the hundreds of tons was an inventory of depleted uranium-238, the waste exhaust from the uranium enrichment process. In theory, this useless stuff could be converted to fissile plutonium-239 by fast neutron capture. This was possible in the graphite­moderated converter reactors, because the fissioning U-235 was co-located with the U-238 in the natural uranium fuel. Before it had a chance to escape the fuel rod and be moderated down to thermal energy, a freshly born neutron running at ramming speed had a chance of being captured by a nearby U-238 nucleus. The uranium nucleus, heavier by one captured neutron, would then be U-239, which would beta-minus decay into neptunium-239 with a 23.47-minute half-life. The neptunium would beta-minus decay in its own sweet time with a half-life of 2.365 days into almost-stable plutonium-239, a very useful nuclide. Once it made it out of a fuel rod and into the graphite, a neutron’s value changed from being able to convert U-238 to being able to cause fission in another U-235 nucleus as it slowed down to thermal speed. Walter Zinn postulated a reactor that could run without a moderator. All the neutrons would be fast, causing fissions at top speed rather than slowed down, and therefore neutrons not used for fission would be able to convert the wasted U-238 into useful plutonium. Each fission released more

than two hot-running neutrons, and only one was required to trigger another fission.93

Zinn’s concept was a reactor that burned the artificial nuclide Pu-239 to make power. Manufactured plutonium was almost 100 percent pure, containing no worthless isotopes, and it did not need the advantage of thermalized neutrons to fission efficiently in a fast-neutron environment. The fission process in pure Pu-239 was not marginal and barely able to make it, as was the natural uranium fission scheme. The plutonium reactor core, bleeding fast neutrons from every external surface, would be surrounded by a blanket of pure U-238. Wasted fast neutrons escaping the fission process would be captured in the uranium shield, converting in a few days into more Pu-239. Calculations showed that such a pile would produce more Pu-239 than it burned in the fission process. It seemed utopian. It was a power source that produced more fuel than it consumed. There was enough U-238 piling up from the weapons production to provide the total energy needs of civilization for thousands of years into the future, without drawing down the weapons material or the submarine fuel. This gorgeous concept would be known forevermore as the “fast breeder reactor.” There were some minor complications to be

worked out.94

A power reactor must have some means of transferring energy from the fission process to the power-generation process. In Rickover’s submarine reactor, being assembled for testing just over the horizon from the EBR-I site, the medium of transfer was water. The water absorbed heat from the fission by direct contact with the fission neutrons, which were born going 44 million miles per hour. Zinn’s breeder had to be different. There would be no neutron moderation, no slowing them down to thermal speed. The coolant in the breeder had to be heavy, metallic, and liquefied, so that it could absorb heat from the reaction by conduction to metal surfaces in the reactor structure without slowing anything down. Neutrons hitting heavy metal nuclei would simply bounce off and retain their speed. Both transfer methods, water and metal, kept energy from accumulating in the machine and causing it to melt. The fluid medium would flow into the bottom of the reactor core, picking up heat and exiting through a pipe at the top. For the EBR-I, the logical choice of coolant was a mixture of sodium and potassium metals, pronounced “nack.”

By mixing sodium with potassium, the melting point of the metal could be brought down to about room temperature. It was a very sluggish fluid, but it would flow, particularly when heated to 900 degrees Fahrenheit with the reactor at full power. Unlike water it was, of course, completely opaque. There was no way to visually inspect the reactor internal structures with the coolant in it, the way it was possible using water moderator. The sodium tended to activate under the neutron bombardment of fission, becoming sodium-24, throwing beta and gamma radiation with a 15-hour half-life. The potassium was a lesser activation risk, but it would contribute some to the induced radioactivity. The worst characteristic of nack is that it would react vigorously with air, water vapor, or particularly liquid water, becoming sodium and potassium hydroxides. In their undiluted form, these are nasty chemicals. Step in a puddle of it, and it will first dissolve your heavy leather boot followed by the foot inside the boot. Anything aluminum touched by it, like an airplane or a Pullman railway car, turns to white powder. There were entire reactors made of aluminum, but this one would have to be stainless steel.

Zinn found that plutonium-239 was impossible to obtain for reactor experiments. By 1951 the AEC was turning out plutonium-based implosion bombs on an industrial scale, and surplus material was simply unavailable at the time. It was easier to obtain 97-percent enriched

uranium-235 for the EBR-I fuel, and it was an adequate substitute for the plutonium.95 At Argonne, the 52 kilograms of bomb-grade uranium was fabricated into 179 stainless steel-clad fuel rods with some spares, made pencil-thin for good heat conductivity to the nack. The rods were mounted vertically in a steel tank, separated from each other in the preferred “hexagonal pitch” configuration so that the coolant could flow through them from bottom to top.

Control of a fast reactor is a bit touchy, because a smaller percentage of the fission neutrons are delayed than in the usual thermal reactors. With most of the neutrons born instantly upon fission and no slowing-down time allowed, the smoothness of the controls is diminished. The fission in EBR-I was managed using boron neutron-absorption rods, moved up and down into the reactor core by electric motors. To shut it down quickly, you could bring your palm down on the red scram button and operate the motors at maximum in-speed, or you could hit the reflector release button. Under this condition, the bottom half of the breeding blanket would unlatch and fall away by gravity with a floor-shaking CLUMP. Just losing the blanket and its tendency to reflect some neutrons back into the core was enough to kill the fission process and make the reactor quickly subcritical. In the middle of the control room there was also an alternate scram control. It was a triangular metal handle, hanging by a chain. Anyone in the room could pull that handle at any time and shut down the pile instantly.

In late May 1951, the experiment was ready for a power-up, and dignified guests and visitors, having endured a dreary ride out to the site, were eagerly anticipating success. With all the controls carefully pulled out, the reactor remained serene and subcritical. Zinn remained calm and estimated that the core was so completely dead, he would need another 7.5 kilograms of fuel to make it work. With a hint of reluctance the AEC granted him some more U-235 from military stockpiles, and it took three months to get it fabricated into fuel.

On August 24, 1951, the world’s first fast breeder reactor was the first reactor at NRTS to go critical. At zero power it worked fine, but measurements indicated that the fuel assemblies would have to be modified if the thing was going to boil water and make steam, as was necessary for a power reactor. Two thirds of the fuel rods were shipped back to Argonne, where they were made shorter and wider by a hydraulic press. Arriving back in Idaho, they were arranged as a belt-line around the thinner fuel tubes.

On December 20, the reactor was run up to about 45 kilowatts. The hot metal coolant was pumped continuously through a heat exchanger with water on the other side of the heat transfer process. At 1:23 in the afternoon, an operator opened a steam valve connected to the heat exchanger, and steam ran through the power turbine. Four 200-watt light bulbs on the turbine deck began to glow white-hot. At that instant, electrical power was first generated by a nuclear

reactor.96 Zinn took a piece of chalk, wrote his name on the concrete wall of the building, and invited his entire team to do the same. Those names remain on that wall to this day.

Success followed success with EBR-I. Three days later, the crew was able to connect the entire facility to the generator and run everything off reactor power. They ran it at power until early in 1953, when they shut it down for a fuel and breeding blanket evaluation. Representative samples were sent back to Argonne for chemical analysis, and the results came back positive. There was more plutonium made in the blanket than there was uranium lost in the fuel. The breeder concept was verified, and the electrical power future of the world could now be moved beyond the point where the coal runs out. Zinn believed that in the short run, breeders would be the only type of reactor that could compete commercially with fossil-fuel power plants. He pressed on vigorously and started the plans for EBR-II.

Experiments continued, revealing the subtle unknowns in breeder reactor behavior. One characteristic was a particular nag. The breeder had a positive temperature coefficient of reactivity. That is, when the temperature increased, the thing went supercritical, and the operator would have to pull it back down by inserting control rods until it was back to the desired power level. Zinn had a theory that if he pushed the temperature to beyond 852°F, then the effect would reverse, pulling the power down. The logical way to run the temperature up and test this idea was to stop the coolant pump and see what happened. The scram channel for core temperature that would normally shut the reactor down if the core was hot beyond a threshold was disconnected.

On November 29, 1955, the EBR-I was ready for the experiment. It was kept at a low power of 50 watts, so that things would not get out of hand. The coolant flow was stopped with the controls set for a period of 60 seconds, meaning that the power level was multiplying by about

2.7 every minute.97 The pile immediately started acting crazy. In three seconds the power had climbed from 50 watts to one million watts, and the period was at 0.9 seconds and dropping. The thin, unsupported fuel rods had buckled under the high heat at the center of the reactor core, bending inward, getting closer together, and improving the reactivity of the non­moderated pile. As the heat increased, the fuel bent farther inward, becoming less like a metal — cooled reactor and more like a Godiva assembly, a touchy, dangerous ball of fissile metal. Harold Lichtenberger, the reactivity specialist on hand, yelled to the operator “Take it down!” The assistant operator at the controls, not knowing exactly how to respond to such a request, reached for the button to initiate a slow control drive-in. It took two seconds for this error to sink in, with the power rising faster and faster. Operating on instinct, the senior operator lunged for the scram button, and the power excursion ended immediately.

The crew resumed breathing. One strong advantage of a liquid-metal-cooled breeder reactor over a water-cooled reactor was immediately obvious. If they had been running a water reactor in that kind of runaway condition, the steam explosion would have wiped out the building. In this case, there was not a sound, not a whisper out of the pile as it went wild. The only way they could tell that anything was wrong was by the instruments on the control panel. Nobody had been exposed to any unusual radiation, and the reactor looked just as it had that morning before the startup. Fifteen minutes passed and they were feeling very good about their design concept when the building radiation alarms started going off.

It is an ear-damaging, hair follicle-killing sound that penetrates down to your center of mass. It sounds like a pterodactyl screaming into the side of your head, as if we knew what a pterodactyl sounds like. BRAK. You can almost feel his hot, nasty breath condensing on your temple and rolling down your cheek. BRAK. BRAK. Your nerves unravel at the urgency of the signal. BRAK. BRAK. BRAK. It means “make for the door,” or, as they say in the accident reports, “all personnel evacuated the building.” You unconsciously drop whatever you were holding and swivel to face the exit.

Careful analysis of the incident revealed that the core was completely trashed and the primary cooling loop was contaminated with fission products. The United States had experienced its first meltdown, with the top half of the core liquefied and running south into the bottom half. Nack in the center had vaporized and forced its way into the breeding blanket as the power reached 10 megawatts, or 7 times the pile’s designed capacity if the coolant were running. No personnel were harmed, and the accident was undetectable outside the building. If the senior operator had not hit the scram button, the reactor would have shut itself down anyway. At the time of the scram, the melted fuel was foaming in the metallic coolant, diluting in the nack and beginning to lose its supercritical configuration.

The AEC kept the incident secret out of fear that news of a nuclear reactor accident would affect public opinion in a negative way, which it did a year later when an account was leaked into the journal Nucleonics. The editor was merciless. Keeping such incidents secret deprived the engineering community of experience, and it was incorrect to keep information concerning a system that was meant to be handed over to the public out of the public view, particularly if it indicated something bad. The AEC agreed in principle and resumed doing what it was doing. The public, watching movies about giant insects mutated by A-bomb tests and digging backyard bomb shelters, was considered incapable of handling routine nuclear news. They were too saturated with Hiroshima, Nagasaki, deaths by radium, and Japanese fishing boats to think rationally.

The EBR-I core was redesigned and reinstalled in 1957. The new U-235 core had zirconium spacers between fuel rods, developed in Rickover’s S1W program 10.47 miles northeast of the site, and this embellishment seemed to prevent further power excursions due to mechanical effects. In 1962 EBR-I finally got a plutonium core, and it ran with good performance until 1964 when the old pile was shut down permanently. It was time to move on to a bigger, more advanced power plant, the EBR-II. The improved plant ran without incident until it was finally shut down in 1994. In its lifetime it made over two billion kilowatt-hours of electricity and, with the production of direct space heating, kept the workers at Argonne West, which had become an official installation at NRTS, from freezing in the Idaho winters.

By some opinions, the most bizarre adventure in fission development in the 1950s was not the nuclear-powered tractor wheel hub, the plutonium-fueled coffee maker, or even the atomic land mine. No, the prize for the most money thrown at the least likely application probably belongs to the Aircraft Nuclear Propulsion program, or the ANP.

The ANP program began in 1947. There was talk in the Defense Department about a possible nuclear submarine project for the Navy, and the Air Force wanted its own counterweight, a strategic bomber that could stay in the air for months on nuclear jet engines. The working slogan was “Fly early!”, and an unrealistic development period of five years was estimated.

Some reactor physicists knew better and expressed doubt as to the practicality of the plan. Putting a light-weight reactor operating at 2,000°F in an airplane and running it without killing everyone within a few hundred feet was not as easy as it sounded. Airplanes had to be made of thin, lightweight materials, like aluminum or magnesium. Reactors were set in concrete, with a lot of lead and steel involved. The two design concepts, fission power and airplanes, were working at opposite ends of the materials spectrum. There were many unknowns for building such an engine, and a lot of piecemeal experimentation would be necessary before the concept could be called possible.

In 1948 a report was commissioned at MIT for studying the feasibility of developing a nuclear — powered airplane. The final document, called the “Lexington Report,” contained some good news and some bad news. The good news was that building a nuclear-powered vehicle that could lift off the ground and fly on its own looked possible. The bad news was that it would take a billion dollars and 15 years to work out the details, and if the thing crashed somewhere, the debris field would be uninhabitable for thousands of years. The Air Force pounced on the good news. Together with the Joint Committee on Atomic Energy and a cadre of aircraft manufacturers, they overruled the nay-saying nuclear scientists, President Eisenhower, the Bureau of Budget, and the Secretary of Defense. The ANP got a green light to proceed in

1952.—

The project spread out all over the country, from Pratt & Whitney in Massachusetts to Lockheed in Georgia, from Convair in Texas to General Electric in Ohio. In July the largest chunk of the work went to the NRTS in Idaho, where the engines would be hot-tested out in the desert. There was jubilant celebration in every quarter.

A jet engine is basically a large metal tube, mounted with one open end pointing toward the front of the aircraft and the other end at the back. With the plane moving forward, air blows into the front of the tube. An axial compressor spinning at high speed at the front acts as a one-way door, encouraging air to come into the tube while preventing anything from escaping out. In the center of the tube is a continuous explosion of jet fuel mixed with the compressed incoming air. The mixture, burned and heated to the point of violence in the explosion, instead of blowing the airplane to pieces finds a clear path out through the back of the tube. The escaping explosion products create a reactive force, just as would be made by a rocket engine, pushing the engine and the vehicle to which it is attached forward. On its way out, the expanding gases spin a turbine, like a windmill, and it is connected forward to the spinning compressor wheel. The nuclear aircraft engine was to operate in this way, except that the continuously exploding jet fuel would be replaced by a nuclear reactor running perilously close to fiery destruction.

General Electric got the contract for the engines, to be tested at the NRTS.99

A piece of desert about 30 miles north of the center of the NRTS was picked out and named Test Area North, or TAN. It was the farthest point from anyone else’s reactor experiment. A large assembly building was erected, the control room was buried for safety reasons, and the test stand was built a mile and a half away, with a four-track railway connecting back to the main site. The engine was put together in the assembly building, and then it was rolled out to the test stand using a lead-shielded locomotive. The engine weighed a hefty eight tons.

The first test engine was called “HTRE-1,” High Temperature Reactor Experiment One, or “Heater-One.” The two jets were modified GE J-47s, and the reactor having enough power to superheat the intake air turned out to be too large to fit in the space normally occupied by the fuel burners. The reactor used enriched uranium clad in nickel chromium, with water as the moderator. The airstream was taken from the jet engine tube immediately after the compressor stage at the intake opening. Using a large conduit, this compressed air was fed through a honeycomb of passages in the reactor, where it was heated and expanded as it would have been in the fuel burner in a normal engine. The air was then piped back into the engine in front of the turbine and out the exhaust nozzle. On November 4, 1955, the reactor was tested at criticality by itself, and on December 30, it was ready for a hot test in the fully assembled engine. The reactor was unrealistically large, meant to test the concept and not to be mounted in an airframe, and it heated the air for both tandem-mounted jet engines.

The assembly was rolled out to the test stand, bolted down to the concrete apron so it wouldn’t fly away, and hooked up to a long, horizontal pipe used to direct the exhaust into a filter bank. This would prevent disintegrating fuel rods from being blown all over NRTS. The pipe ended in a 150-foot vertical smokestack staring right up into the big Idaho sky. The operation crew, hunkered down in the control room, spun up the two compressors using electric starter motors, lit the flames in the burners, and powered up the reactor. When both engines reached operating temperature, the jet fuel automatically shut off, and the jets spooled up to screaming speed on pure atomic power. It performed as predicted, but the gamma radiation was far greater than had been anticipated. Operational plans for the bomber would have to be modified, and perhaps more crew shielding would be needed.

Testing of Heater One continued, and work began on the world’s first fully shielded bomber hangar. A special tracked vehicle, heavy with lead shielding, was built with robotic arms and a thick, lead-glass viewing port for the driver. It would be used by the mechanic to work on a radiologically dirty airplane, blazing with fission product contamination and neutron-activated metal parts. A 23,000-foot-long runway was surveyed, and test missions were scripted. An electric incinerator toilet was invented for use by the flight crew, and pre-packaged meals were planned. Money flowed.

There were problems with the extremely high temperature necessary in the reactor. Fuel and reactor internal components evolved into exotic ceramics. HTRE-1 was modified and renamed HTRE-2, changed into a high-temperature-materials test reactor by cutting a hexagonal, 11-inch hole in the middle of the reactor. Newly designed fuel elements were mounted in the hole and run up to 2,800°F. Progress was encouraging, and it was time for HTRE-3.

HTRE-3 was a complete redesign. One smaller, horizontally mounted reactor ran two tandem J-47 jet engines, mounted as they would be in the proposed airplane, with the reactor located

at the center of balance of the airframe.100 The reactor was sized realistically, such as would fit in the finished airplane, but it still dwarfed the big General Electric jets. The fuel pins and control rods took up a lot of space, but there still had to be enough air passageway to spin the turbines in two J-47s. The core diameter was 51 inches, and the length 43.5 inches. The moderator was a solid ceramic, zirconium hydride, and that also took up room in the reactor core. The whole thing was encased in a solid beryllium neutron reflector. The reactor would still be considered highly advanced 54 years later.

By November of 1958 Heater-Three was on the test stand and ready to show what it could do.101 On the morning of November 18 the crew started the engine compressors and made the reactor supercritical by manual control. Power was increased slowly to 60 kilowatts and leveled off, just to “check for leaks.” Everything seemed fine. The crew shut it down and went

to lunch.102 Feeling fed and frisky, the crew decided to proceed with the experiment program and run it up to 120 kilowatts. The engines started smoothly, with power increasing by a factor of 2.7 every 20 seconds. When the power reached 12 kilowatts, they switched to automatic, released the control handles, and sat back to watch it happen.

The automatic control used an ion chamber to detect gamma rays originating in fission. The number of gamma rays detected per second was perfectly proportional to the power level of the reactor, and it was read out as kilowatts on a meter at the control panel. The same signal was fed to a pen-chart recorder, giving a permanent record of power history of the engines. The current from this same detector was also fed to an amplifier, and this enhanced signal controlled a set of electric motors connected to the reactor control rods, running them in or out of the reactor core to satisfy a pre-set level of gamma-ray production rate. The high-voltage line feeding electricity to the ion chamber had been modified as an improvement to the circuit. A filter had been installed to prevent clicks and hums originating in the electric motors from contaminating the gamma ray signal.

If the power got out of hand for some unforeseen reason, the reactor would scram automatically on the gamma-ray level signal at a pre-set point, below the level where any harm could come to the machinery. As a backup, a set of thermocouples in the core monitored the reactor temperature continuously, feeding another scram channel. There was no steam to explode, so the worst thing that could happen would be too much power making too much temperature and causing the thing to melt.

The power level passed the 60-kilowatt level. No problems. They were now in untested territory, but the engines were accelerating smoothly. 80 kilowatts. No problem. 90 kilowatts. Still increasing power. 96 kilowatts. The power level started to fall rapidly, as if the bottom had dropped out. The crew, watching the instruments, found this curious, and the reactor operators cocked forward in their seats. The automatic control, sensing that the power was dropping quickly, pulled out the controls, trying to bring it back up. The power seemed to keep going south, and the needle on the meter fell to the left. Twenty agonizing seconds passed and WHAP! The scram circuit, detecting that the thermocouples in the reactor core had all melted, shut her down automatically, throwing in all the controls at once. In those 20 seconds, every piece of fuel in the reactor had lapsed into the liquid state. The fact that it overheated had not disassembled the reactor, as it was made of some very rugged ceramic materials, and the reactivity had actually increased as the nickel-chromium-uranium-oxide fuel turned to fluid. When the indication had been that the power was falling, it was actually increasing very quickly. Although the fuel was designed to be very tolerant of extreme temperature, the power level had spiked beyond the capacity of the two jet engine air-intakes to keep the reactor core from melting. Only a few of the zirconium-hydride moderator sections were damaged.

A slight increase in background radioactivity was detected downwind of the smokestack as some few fission products, evaporated off the white-hot fuel, made it through the filter bank. Aside from that and the pen-chart recording, there was no outside indication that anything had gone wrong, and no humans were harmed.

The steel annulus surrounding the reactor was pumped full of mercury from a holding tank.

Mercury is a high-density metal, liquid at room temperature, and it makes an excellent gamma — ray shield. With it in place, the crew could approach the Heater-Three to disconnect it without

danger from the decaying fission products built up in the damaged fuel.103 The engine was then dragged back to the hot-lab in the assembly building, where the core was rebuilt and the source of the problem was analyzed.

That filter in the high-voltage cable had unfortunately limited the number of electrons per second that could travel through the wire. That was fine, as long as not too many electrons were needed to register the number of gamma rays per second that were traversing the ion chamber. At the higher power level, at which the equipment had never been tested, the gamma flux overwhelmed the ability of the power supply to keep up. The current demand from the chamber was so high, the voltage dropped, and the detector stopped detecting. The automatic system interpreted this as a power loss, and it tried to compensate for it by pulling the controls. The power climb accelerated until the engine was, as we say, outside its operating envelope. This incident went down as the first time in history a reactor was melted because of an instrumentation error. Human error was a fault only indirectly.

In December the AEC told the Air Force that the nuclear bomber could not be flown over the United States. The only way it could be flown was out over the Pacific Ocean, presumably taking off from the beach. The 8-million-dollar shielded hangar, recently finished, could no longer be used to house a nuclear bomber, and grading the runway would not be productive. On January 20, 1961, John F. Kennedy was sworn in as President of the United States. On March 28, he signed a paper canceling the ANP project, and that was that. The much disappointed staff at the NRTS knew that they were very close to a working atomic aircraft engine, but for the good fortune of nuclear power we will never know if it would have flown.

A cluster of three reactor accidents involved the explosive conversion of water into steam by nuclear means. Two of the incidents were accidents only by procedural technicalities, and the other one was a complete surprise. We know exactly how it happened, down to the millisecond, but we have no answer as to why.

Among the gifted reactor physicists at Zinn’s Argonne lab was Samuel Untermyer II, grandchild of Samuel Untermyer I. Sam the First was a Jewish-American born in Lynchburg, Virginia, who became the most famous New York lawyer of all time. He was responsible for, among other things, maintenance of the 5-cent subway fare. His grandson, a graduate from MIT in 1934, did not believe that the revered pressurized water reactor, in which the coolant is kept at such a high pressure it cannot boil, was the only way to build a water-moderated pile. In those early days of reactor development in the late 1940s, the general opinion was that if the water in the reactor vessel were allowed to boil, then the neutron production would become erratic and unpredictable. The coolant voids caused by steam bubble formation were predicted to cause fuel melts, chemical explosions, unchecked power excursions, and probably boils on the reactor operators and tension headaches.

Untermyer proposed a contrary prediction. If the coolant, which is also the moderator, in the reactor vessel were allowed to boil into steam, it would simplify the power production mechanism. There would be no need for a complicated, expensive, failure-prone steam generator and a second cooling loop. The reactor vessel would become a boiler, like the boiler in a coal-fired power plant but simpler, without any boiler tubes. No pressurizer to maintain the lack of boiling would be necessary, and several pumps and valves could be eliminated. Instead of running wild and unpredictable, the neutron flux would be controlled. A great deal of boiling would result in moderator voids, which would degrade the fission process and lower the power level. If the boiling were quenched, the density of the moderator would increase, and the power level would rise to a threshold cutoff, floating between too much power and too little power. Such a boiling-water pile would control itself and follow the load demand. There would be a lesser need for an electronic feedback-control system, such as would cause the HTRE-3 to melt in ’58. In the event of an uncontrolled upward power excursion, the moderator would boil away, and this would automatically turn off the fission process without the need for an electronically controlled scram system. These seemed like desirable qualities in a power reactor, but it would all have to be proven with physical experiments.

Untermyer convinced his boss, Walter Zinn, of the importance of the boiling-water-reactor concept, and together they petitioned the AEC for a contract to prove the principles. In 1952 he was given enough money to make a modest stab at it and a spot of desert at the NRTS. The test reactor would be laid out on the ground, without so much as a tin roof over it, and the control room was a small trailer parked half a mile away. Television cameras gave the experimenters views of the reactor, including one using a large mirror to show the top of the core. The reactor vessel was a steel tank, half an inch thick, 13 feet high and 4 feet in diameter, halfway sunk in the ground. The 28 aluminum-clad enriched-uranium fuel elements were surplus from the big-budget Materials Test Reactor being erected elsewhere on the desert. The total fuel loading was 4.16 kilograms of uranium. The control rods were inserted through the open top of the vessel, adjusted in and out of the core with electric motors and wired back to the control trailer. Pipes, cables, and tanks were all over the ground. The steam made by the reactor heat was simply vented into the air. Dirt was mounded around the exposed portion of the reactor to give it some gamma-ray shielding. Untermyer, expecting this

to be the first in a glorious series of experimental reactors, named it BORAX-I.104

By May 1953 BORAX-I was loaded with fuel, filled with water, and ready to go. Over the next 14 months, Untermyer and his operating crew would afflict this frail collection of scrounged parts with every torture imaginable. Over 200 experiments were performed, subjecting the system to all the operator errors and component failures they could think of. Tourists riding by on Highway 20/26 would report a geyser to the authorities. That would be Untermyer seeing how far he could throw a plume of water if the thing went uncontrollably supercritical. The record, I think, was 150 feet straight up. Under all conditions, the system performed exactly as predicted, shutting itself down automatically while allowing no harm to the machinery. The self­regulating feature worked right on the money.

By July 21, 1954, they had done everything to the reactor that their fertile minds could conjure, and it was time to shut her down and vacate the site. As one last experiment, Untermyer wanted to blow out the control with compressed air and see how the thing would react in a fast transient, with the reactivity taken from stable criticality to prompt supercriticality

as quickly as possible.105 Although there was no conceivable physical situation in which this would normally occur, it would give them an upper boundary of reactor mayhem to work with. It would also be a fine spectacle to watch, a steam explosion in keeping with the Bill Crush trainwreck spectacle in Waco, 1896, only without the public being able to watch. They would,

however, film it in slow motion, so that it could be watched and studied, over and over. Extra fuel was loaded, and the central control rod was beefed up.

The wind was blowing in the wrong direction. Thinking that it could waft fission products over someone else’s reactor experiment, the site meteorologist canceled the test. The crowd of important guests, expecting a train-wreck, went away disappointed. The next day at 7:50 a. m., the smoke bombs ringing the site were sending fumes straight up. It was time. The drivers cranked up the emergency evacuation buses, and the State Patrol stood prepared to close down the highway. The visitors, having returned with renewed anticipation of a good show, were standing in rapt attention at the official Observation Post, growing quiet, spitting out gum, and polishing the dust off eyeglasses.

The crew was worried. Would the explosion be big enough to excite the crowd? Would the

control rod hang in the guides and spoil the transient?106 Harold Lichtenberger, the physicist sitting at the controls, promised to give it his all.

Lichtenberger hit the EJECT CONTROLS button. KABOOM! Up she went with the force equivalent of 70 pounds of high explosive in the reactor vessel. A total energy release of 80 megajoules had been expected. They got 135 megajoules instead, and this inaccurate prediction instantly qualified the test as a nuclear accident. The little reactor that usually shed energy at the rate of 1 watt ramped up to 19 billion watts with a minimum period of 2.6 milliseconds. In all other tests of explosive steaming, the thing would send up a geyser of water droplets, sparkling in the western sun. This time the core melted instantly and homogenized into a vertical column of black smoke. A shock wave rippled through the floor of the control trailer.

Walter Zinn, standing in the control trailer, shouted “Harold, you’d better put the rods back in!”

“I don’t think it will do any good,” Lichtenberger shouted back. “There’s one flying through the air!”

In fact, the entire control mechanism, bolted to the top of the reactor vessel and weighing 2,200 pounds, was thrown 30 feet up in the air. Zinn watched as a sheet of plywood flew spinning across the desert like a Frisbee. BORAX-I was totally destroyed. Pieces were found 200 feet away, and all that was left of the reactor was the bottom plate of the vessel with some twisted fuel remnants lying on top of it. The slow-motion movies were fogged by unexpectedly high radiation, and the power to the cameras failed as the wiring was carried away in the blast, but there was enough footage to show the plume of debris as it shot upward. Pieces of fuel were shown catching fire in the air as they tumbled upward. A control rod could be seen rocketing away at the upper left and eventually the control chassis re-entered the frame from above. In the first few seconds of the film they watched something that always seemed a feature of a prompt fission runaway: the blue flash. It lasted only two milliseconds, but it lit up the top of the reactor assembly as if it had been struck with a bolt of lightning.

You could not have asked for a better show, and a fine time was had by all. Untermyer had pushed a boiling-water reactor as far over the brink of disaster as was possible, and there were no radiation exposures or physical injuries. With this one staged spectacle, Untermyer had brought the AEC, the Argonne Laboratory, the military services, and the NRTS face to face with their collective fear, that a nuclear power reactor out of control could wreak havoc with a nineteenth-century steam explosion. Instead of frightening everybody, it calmed them down to have seen it. The maximum disaster seemed finite and manageable, and it was clear that this accident could never happen again. No normal power reactor control panel would ever be built to pull out the rods at explosive speed, and nobody was crazy enough to jerk out the central control by hand.

The debris was buried on the spot, and plans for BORAX-II were implemented on the same site. In the next few years, BORAX-III, BORAX-IV, and finally BORAX-V, a full fledged commercial-grade power reactor, were built and tested, with further experimentation justifying Untermyer’s dream of an inherently safe, self-controlling nuclear reactor. The good feelings, however, would barely make it into the next decade.

The United States Department of Defense was forming strategies for winning the Cold War, the global stand-off with the Soviet Union in which each side threatened to blow the other to kingdom come. These preparations were forward-looking yet practical, and they seemed somewhat less like science-fiction than the Air Force’s ANP program. Among the plans were the Distant Early Warning System, or “DEW Line,” and Camp Century. The DEW Line would be a set of remote, long-distance radar stations along an arc inside the Arctic Circle, in Alaska and Canada, intended to give a heads-up of several minutes if Soviet nuclear missiles were bearing down on the United States. Camp Century would be an under-ice city in Greenland supporting a hidden array of mobile, medium-range guided missiles, capable of pounding Moscow down to

bedrock with thermonuclear warheads.107 The mission was code-named “Project Iceworm.”

Each of these proposed measures would require electricity for lighting in the months of total darkness and operation of the radars plus space-heating to keep the soldiers from freezing to death. These types of installation, such as outposts in the Antarctic, were usually powered with diesel generators running 24 hours a day, but to give life to a base as large as the proposed Camp Century would take a million barrels of diesel fuel per year, which seemed impractical. Camp Century supported 200 soldiers, one dog, and—brace yourself—two Boy Scouts: Kent Goering of Neldesha, Kansas, and Soren Gregerson of Korsor, Denmark, all existing on a sheet of glacial ice 6,000 feet thick. The base commander, Captain Andre G. Brouma, is credited with the motto, “Another day in which to excel!”

The Army Corps of Engineers was assigned, on April 9, 1954, to develop a range of small reactors to provide electrical power and space heating for remote conditions in the Arctic and the Antarctic. The U. S. Army Engineer Reactors Group, headquartered in Ft. Belvoir, Virginia, was in charge, and their observers had been very impressed with Untermyer’s BORAX-I experiments.

The list of specifications for the army reactors was interesting, and the boiling-water reactors being developed at NRTS were closer to meeting the requirements than were Rickover’s submarine plant or Zinn’s breeder. The reactors had to be small, relatively inexpensive, and as simple as possible, with a minimum number of moving parts. Nuclear reactors at this young stage were notorious for needing nuclear physicists, highly specialized engineers, and all manner of Ph. D. scientists on hand for normal operation. These reactors would need no such specialists at the plant site. Operators would be given a few months of training and a couple of weeks experience on a training reactor at Ft. Belvoir, but keeping a staff of thoughtful academics alive at a remote army base was out of the question. Moreover, the entire plant would have to be able to be pulled on a sled over ice, lowered into place, and hooked up with a minimum of effort. It could be broken down into sections, but they would have to screw together easily under hard conditions. Nothing could be welded together on site, and certainly no concrete, the basis of all nuclear construction, could be poured in temperatures far below freezing. There would be no calling the factory for replacement parts. They would have to be foolproof, such that an inexperienced operator or one deprived of sleep for three days would not be capable of pushing the wrong button and destroying anything.

The reactor design shop at Argonne took the challenge eagerly, and they came up with the Argonne Low Power Reactor. The name was changed to SL-1, meaning Stationary Low-power reactor, version one, and the small demonstration plant was built in a remote spot at the NRTS in Idaho. Construction and management of the project was transferred to Combustion Engineering in Stamford, Connecticut.

It was everything that the Army had asked for. It was a small boiling-water reactor, making three megawatts of heat. Of this, 200 kilowatts would be converted into electricity using a combined steam turbine-generator, 400 kilowatts would be hot air to be piped into living and working quarters, and the rest would be exhausted into the environment using an air-cooled heat exchanger. All the machinery was housed in a simple, cylindrical building made of quarter — inch steel, 38 feet in diameter and 48 feet high. In the ceiling was the “fan room,” containing the heat exchanger and electrically powered blowers. The lower section was filled in with a combination of loose gravel and steel punchings, with the reactor buried in the middle and flush with the floor. The punchings, left over from making rivet holes in bridge girders, and gravel acted as a bio-shield to absorb all radiation made during and after fission in the reactor vessel. The mid-section of the building was an open space containing the turbogenerator, transformer, tanks, valves, and equipment that could be accessed by workers.

The reactor vessel was 14 feet 6 inches tall, filled with water to the 9-foot level, leaving 5 feet 6 inches of clear space at the top where the steam could collect.

A covered walkway led to the sheet-metal control building sitting on the ground next to the reactor building. Security was provided by a high chain-link fence surrounding the site, with a guard stationed during the day shift. It was functional and as simple as it could be, and the entire facility was built for about $1.5 million. As an Arctic power source, it would cost less to buy and run than the shipping charges alone for the fuel that it was to replace.

The SL-1 plant was started up on August 11, 1958. Its Argonne design had been slightly modified to extend the operating time between fuelings to five years. The fuel assemblies had been lengthened by a few inches so that more highly enriched uranium could be included. This increased the reactivity of the core considerably, and to bring it down to a controllable level some metallic boron was added to the lower ends of the flat, aluminum-covered fuel strips. The boron would soak up neutrons and negate the extended reactivity, but as the fuel in the upper core fissioned away, the boron’s ability to absorb neutrons would also wane. Every time a boron-11 nucleus soaked up a neutron and took it out of the fission process, it would decay in multiple steps to carbon-14, which had no affinity for neutrons. Gradually, over five years, the active region of the reactor core would migrate down while maintaining the designed power level. There were better ways to do this, but for the SL-1 thin sheets of boron were riveted to the ends of the fuel assemblies.

The controls, like everything else in the plant, were designed to be as simple and foolproof as it was possible to make them. There was one main control, made as crossed cadmium-filled blades that would fit between the fuel assemblies, inserted down through the middle of the core. It was moved up and down in the reactor to control the neutron population by a rack-and — pinion mechanism, driven by a DC electric motor and gearbox bolted to the floor off to the side. The control rack penetrated the top of the reactor through a watertight seal called the “shield plug.”

In its operating configuration, the SL-1 reactor was radiation-shielded on top by large concrete blocks and a stack of steel plates. All this shielding had to be removed for servicing the inside of the reactor vessel. The control "rods” were actually cross-shaped, and only the large control in the center of the core was used to regulate the fission. The smaller rods were used to smooth out the neutron flux so that the fuel would be consumed evenly across the diameter of the reactor core.

Having one big, master control was fine, but for the fuel to last for more than a few years the flux profile would have to be flattened. In theory, the number of fission neutrons in the reactor at a given time would tend to peak at the center of the core. A plot of neutron population across the diameter of the reactor, or the “flux profile,” would be bell-shaped, and for this reason the fuel would fission unevenly, with center fuel burning out first. That one big control distorted the profile, actually improving it by discouraging the peak in the center. To further enhance the profile, there were eight minor controls spaced around the periphery of the core. They were shorter than the main control, with lesser loading of neutron-absorbing cadmium. The purpose of these controls was to flatten the flux, and they could be adjusted by moving them in and out with motors, just like the main control. As the fuel fissioned away over the years, the operators were expected to have to inch these controls out of the core to allow more fuel to be exposed to neutrons while trying to maintain a flat profile. Under all conditions the master control had sufficient heft to take the reactor from cold shutdown to supercriticality without any help from the peripheral devices.

There were no active control-room instruments that could evaluate the flatness of the flux profile. That was accomplished for this extended experiment using flux wires. Flux wires are aluminum with cobalt-59 pellets imbedded at one-inch intervals. Station flux wires around the core in specified locations, and the cobalt-59 was to be activated into radioactive cobalt-60 to an extent dependent on the density of neutrons. After having stayed in the core a while, these wires are retrieved and cut into one-inch lengths. The gamma rays emitted by each section of each wire are then counted, and from these measurements a map of the neutron flux in the reactor is drawn, evaluating the flux-flattening efforts. Unfortunately, to retrieve the flux wires and put in a new set, you have to take the reactor apart. It takes at least three men per shift working for a couple of days, and the reactor, of course, has to be completely shut down.

By January 3, 1961, the SL-1 had been producing power for over two years, and the experiment was going well. This was more than just a test to see if a small boiling-water reactor would produce power. There was not really anything to learn on this point. The purpose of the test was to see if such a plant could be run and managed by minimally trained soldiers without the advantage of expert scientists looking over their shoulders. Could the inhabitants of a remote station, even more cut off from civilization than the NRTS, maintain a power reactor no matter what happened?

There had been a few problems. Water seals and gaskets were leaking, but it was nothing fatal. Those boron strips tacked onto the fuel turned out to be a bad idea. The boron, when it was changed into carbon-14, would curl up and crack. Pieces of it were falling into the bottom of the vessel, and what was left on the fuel was binding up the controls. Under any normal reactor operating conditions, the words “binding up the controls” would result in a quick shutdown, a study, a redesign, assignment of blame, papers written, operating rules changed, and so on. In this case the problem was treated as an interesting perturbation thrown into the exercise. It was just the sort of unexpected problem that could show up on the glacier in Greenland. The Army said “Let’s see how it plays out,” while the AEC and Combustion Engineering kept a detached, mildly interested stance. Any time the reactor was down and apart for maintenance, the peripheral rods had to be jacked up and down by hand to clear out the bent boron at the bottom of the core, or the motors would not be strong enough to move them against the resistance. The main rod, weighing a hefty 100 pounds, was big enough to take care of itself, crashing its way through the twisted metal and having no particular trouble moving with the motor.

It was a clear night and bitterly cold. The graveyard shift consisted of Senior Reactor Operator Jack Byrnes, an Army private; Assistant Operator Dick Legg, a Navy Seabee; and trainee Richard McKinley, Air Force. Byrnes was going through a marriage crisis, he wasn’t making enough money, and he had problems with being managed. Legg was sensitive to comments about his stature and enjoyed playing tricks on his colleagues to pass the time. McKinley was there to learn how to run a reactor plant.

It was time to change out the flux wires, and the previous shifts had done all the heavy lifting. The reactor was basically put back together, with the vessel filled to 9 feet with water and the head screwed down. All the night shift had to do was reconnect the controls and put the big concrete blocks that shielded the top back into place. It was a three-man job. Byrnes and Legg would reconnect the rack to the main control while McKinley would stand off and act like a health physicist, pointing a “cutie pie” ionization chamber at Byrnes and Legg while they worked. The day shift would actually have an “HP” on the staff, monitoring all the activities in the reactor building to constantly check for abnormal radiation, but the night shift was a minimum crew.

The rack that engaged the pinion for up-down motion was screwed to the top of the control, which was at its lowest position in the core, keeping the reactor at cold shutdown status. A C — clamp had been tightened on the rack to hold it in a slightly raised condition, just above the top of the shield plug. This position allowed a three-foot metal rod to be temporarily screwed into the top of the rack so that a man could handle it with the motor disconnected.

The instructions were clearly mimeographed. Byrnes would take hold of the handling rod with all ten digits and lift the 100-pound center control by one inch. With the load off the C-clamp, Legg, crouching over the shield plug, would unscrew it and lay it aside, and then Byrnes would gently lower the control until it rested on the bottom of the core structure. McKinley was standing off the reactor top, in front of one of the man-sized concrete shield blocks, idly watching the show and pointing his radiation detector.

All that we know for sure is that at 9:01 P. M., Byrnes, against the written directions and everything that the instructors had drilled into his head, with one massive heave jerked the master control clean out of the core as fast as he could. If it were lifted four inches, the reactor would go critical, blasting the three workers with unshielded fission radiation. Byrnes managed a full 23-inch pull, and the reactor went prompt critical with a 2-millisecond period, producing a steam explosion in the reactor such as has never been seen before or since. The water

covering the reactor core instantly became superheated steam.108 The four-foot slug of still water over the core, not becoming steam, was pushed with incredible speed to the top of the reactor vessel, through the 4 feet 6 inches of clear space, until it hit the screwed-down top like a very big hammer. The force of the hammer-hit picked up the 13-ton steel vessel and shot it nine feet out of the floor, shearing away its feed-water and steam pipes. The nine shield plugs on top of the vessel shot off like cannon shells, burying control-rod fragments in the ceiling.

Byrnes and Legg were killed instantly, not by the intense radiation surge, but by the explosive shock of two billion billion fissions, 15 megawatt seconds of energy, and an air pressure wave of 500 pounds per square inch. McKinley died two hours later of a massive head wound, inflicted by the concrete shield block as he was thrown backwards. All three men had fission products, built up by the reactor running at full power for two years and turned to nascent vapor in the sudden heat of prompt fission, buried deep in their bodies. There was no way to simply wash away the contamination. It seemed embedded in every tissue.

Legg was pinned to the ceiling with a piece of the master control. The reactor internals were an unrecognizable tangle of twisted parts, and water, gravel, and steel punchings were scattered all over the reactor building floor. The crude steel building, which was meant only to house the equipment and keep the rain off, managed to prevent a scattering of radioactive debris, and outside it was hard to tell that anything had happened. The plant was a total loss, and everything would have to be carefully disposed of, leaving not a trace of radioactive contamination or subjecting any worker to an abnormal dose. The three bodies were so deeply and severely contaminated, they would have to be treated as high-level radioactive waste. Autopsies were performed quickly, behind lead shields with instruments on 10-foot poles.

A commendable job was done analyzing the accident and cleansing the site of any trace of it. It required a great deal of skill and planning to decontaminate the site, as the inside of the reactor building was too radioactive for normal work. A full-scale mock-up of the building was constructed for decontamination practice and to figure out the actions of Byrnes and Legg before and during the accident. Television cameras were inserted into the reactor core using remote manipulators, and a Minox subminiature camera was used on the end of a pole to take photographs through small openings. A seldom-mentioned technique called the “gamma camera” was used to spot where highly radioactive fragments of the reactor had landed in the ceiling and on the floor of the building.

The gamma camera is a variation of the old “pinhole” camera. It is possible to make a picture on a piece of photographic film by mounting it on one inside face of a light-proof, square box. On the opposite face of the box is a tiny pinhole. Light enters the box through the hole, very dimly, and it forms an image on the film without the use of a lens. Light can only travel in a straight line, so individual rays of light from the scene outside the box are organized into an image simply because they all have to come through at the same point, the pinhole. If the box is made of lead, through which radiation cannot pass, then the pinhole on the front face of the box will image gamma rays onto the film the same way it uses visible light. Gamma rays are photons, just like visible light but at a much higher oscillatory frequency and energy. To use the camera, the investigators first made a light image of the ceiling in the reactor building using the open pinhole, then covered the pinhole with a light-tight but gamma-transparent shutter. The gamma ray image was allowed to expose the film for 24 hours through the same pinhole, superimposing a gamma-ray image atop the light image. When the film was developed, it identified radioactive objects in the picture as shining brightly, like points of light.

The reactor building and its contents were buried in a trench 1,600 feet away from the original SL-1 building site. The cleanup took 13 months and $2.5 million. Much was learned about managing power reactor disasters, and the question of what had happened was answered in great detail, down to the millisecond.

What was never answered by detailed forensic analysis was: Why did Byrnes pull that control out? He knew good and well what it would do if it came up to four inches. Why jerk it out all the way? There are, to this day, a few conflicting opinions, ranging from it was a murder-suicide to he was exercising the rod to clear the bent boron. In my opinion, Byrnes was showing off for McKinley, the new guy from the almighty Air Force. The Air Force was running the dangerous, super high-tech HTRE experiments down the road at Test Area North, and the Army was stuck with this cheap, low-power rig that was just sitting here making a slight turbine-hum. Byrnes wanted to give McKinley a thrilling blip on the cutie-pie radiation detector he was holding by bouncing the main rod. He knew that if he could bring it up to supercritical for just a split second, the power would drop again quickly as the control went back down. No harm done, but he bet himself that he could make Air Force lose control of his bladder. The thing was heavier than it looked. He wiped his sweaty palms on his pants, braced, and put both arms into it. Up she came. They never knew what hit them. Their nervous systems were destroyed before the senses had time to register the violent event.

It was a tragic loss of life, and the general attitude toward small, simple, cheap nuclear power was affected. The Army went on to deploy the PM-2A portable medium-power reactor in Greenland, the PM-3A at McMurdo Station in Antarctica, the MH-1A mobile high-power reactor at the Panama Canal, the SM-1A stationary medium-power reactor at Ft. Greely, Alaska, and the PM-1 at Sundance, Wyoming. They even developed the ML-1 at the NRTS, the first nuclear power plant that would fit on the back of a truck. It all ground to a stop in 1977 when the need for remote power and the money to support it both drifted away. It was not at all a bad idea, but commercial nuclear power production moved off in the opposite direction, toward bigger, more complicated, more expensive installations, and the SL-1 incident was a reminder of the dangers of making it too simple. The accident had proven that there was no such thing as foolproof.

The snowcap over Greenland into which Project Iceworm was dug turned out to be one big, slow-moving glacier. The rooms and tunnels so carefully carved out of the ice deformed and shrank with time. Every month, 120 tons of ice had to be shaved off the inside walls, and by the summer of 1962 the ceiling in the reactor room had come down five feet. In July 1963 it was clear that this bold step in missile positioning was not going to work, and the PM-2A reactor was shut down and shipped back home. By 1966, Camp Century was unlivable, and it was given back to nature. When last visited in 1969, it was completely wrecked and buried under a great deal of new snow.

The deep snow cores taken at Camp Century are still in use today. These long cylinders of snow cut from the glacier are a record of the climate and atmospheric conditions for the last 100,000 years, and they have been used to map the carbon dioxide history on Earth since the emergence of mankind.

The last steam explosion in Idaho was the final in a series of experiments with the SPERT-I, or the Special Power Excursion Reactor Test One, on November 5, 1962. One would think that enough was learned in the BORAX-I and the SL-1 blow-ups to pretty much give us what there was to know about water boiling too fast in a reactor tank, but this odd experiment was funded by the AEC. It, like BORAX, gave a bit more of a show than was anticipated, and it went down in history as another accidental power excursion at the NRTS. The incident was all recorded as

a movie in slow-motion at 650 frames per second.109

The reason for the SPERT experiments had to do with the expanding need for nuclear specialists in the 1950s. The AEC was aware of a projected shortage of nuclear engineering and health physics graduates in American universities, and technical campuses needed small research reactors in place to encourage these studies and excite some interest in nuclear topics. The Aerojet General Corporation had already introduced an inexpensive “swimming pool” reactor for use in schools. It was simply a concrete-lined pool of water, sunk in the floor, with uranium fuel assemblies and control rods clustered in the middle. “Is it safe?” asked the AEC. “What would happen if a control rod came loose and dropped out the center of the core?”

It would explode, of course, with the water shooting out the open top of the reactor and hitting the roof really hard, but that was not a sufficient answer. Details of everything that could possibly happen to an open-topped, water-moderated, low-power reactor were demanded. The SPERT contract was given to the Phillips Petroleum Company, and a site was chosen about 15 miles west of the eastern boundary of the NRTS. The first of four SPERT reactors was started up in June 1955, and it was run through a series of torturous accident scenarios.

The setup was very much similar to BORAX-I, but it was enhanced with a metal shed covering the reactor. Controls were inserted through the bottom of the reactor core leaving the top completely open, with one master control in the center. Two periscopes looked down into the core from above, and a tilted mirror showed the open reactor top from the side. These optical features were used to make motion pictures of every experiment simulating wrongful operation

by undergraduates horsing around with the controls.110 Nuclear instruments and recording procedures had improved since BORAX, and better data collection was anticipated. Experiments with fast power transients blew the water out the top of the reactor, just as seen in the BORAX excursions. The fuel was the same as was used in most of the test reactors at NRTS, thin plates of aluminum-uranium alloy clad with pure aluminum. It was not meant as a high-temperature fuel, and some plate warpage and slight melting were observed in the core.

November was the end of the open experiment season in Idaho, as the temperature began to drop to Greenland levels, and the team was out of tortures for the SPERT-I. SPERT-II was designed and ready to build. As one last experiment for 1962, the team wanted to simulate AEC’s worst fear, that the main control rod would fall out. The control-rod drive was modified to break free and fall with gravity, and the metal roof was removed so that the driven water would have nothing to blow away. A 3.2-millisecond period was predicted, with some fuel melting this time. The test was not cut out to be such an event as the BORAX-I excursion. SL-1 had taken the thrill out of seeing water reactors explode.

It was a sunny day in the desert, and the wind was calm. Three… two… one… RELEASE. The main control rod went into freefall. The little reactor suddenly lit up with a blue flash in the mirror as 30.7 megajoules of energy came alive and started heating the fuel. All 270 fuel plates melted, and the fission process shut down completely, as predicted. Everything was going according to plan for about 15 milliseconds, and then all hell broke loose as the unexpected transpired.

The melting fuel sagged and changed shape. Heat transfer between the fuel and the water was suddenly improved, and the resulting steam explosion was more energetic than expected. It completely destroyed the reactor. Contents of the reactor vessel were pounded out of shape and thrown skyward. There was no roof to carry away, but a flying periscope hit a steel roof — beam and bent it outward. Bits and pieces of reactor were scattered all over the place. There were no injuries except to a few egos, and the large bank of instruments could find no harmful release of radioactive gasses into the atmosphere. I will not say that the fine engineers at the NRTS were slow to learn, but this sort of behavior in a suddenly uncontrolled water reactor was hardly a new finding.

This was not the last reactor blown up at NRTS, but all the others were predictable, controlled, and not considered accidents. NASA planned to send up a nuclear reactor into space in the System for Nuclear Auxiliary Power program, and the SNAP-10A nuclear power

generating station was scheduled to be launched into orbit in 1965.111 There were, of course, concerns that the booster could fail before achieving orbit and a power reactor could come down in the ocean. What would be the hazards if this worst launch failure happened?

At NRTS the recently vacated ANP test facilities at Test Area North were converted to test the SNAP-10A in a simulated high-speed crash into the Pacific Ocean. It was correctly predicted that a severe nuclear power transient would result from slamming into the salt water. The reactor was naked of any shielding, and it was moderated by zirconium hydride mixed with the uranium fuel. Hitting the surface would suddenly introduce extra moderating material favorable to fission (water) and the reactor would go prompt supercritical.

A huge water tank was mounted on one of the ANP double-wide rail cars that carried a nuclear jet engine with a SNAP reactor mounted in the middle. The reactor was protected from the water with a Plexiglas shield until an explosive charge threw it out of the way and let the

water crash in. The resulting fireball on April 1, 1964, threw reactor fragments far and wide.112 To keep thermocouples and radiation instruments from being melted and lost in the explosion, the measurements were done remotely, using infrared pyrometers looking into a mirror behind a lead wall. Just to be sure, the test was run three times in experiments SNAPTRAN-1, 2, and

3, and three perfectly good SNAP reactors were destroyed.113 They took movies.

There was also the LOFT (Loss Of Fluid Test) reactor and Semiscale, which was not really a reactor. Both experiment series were used to find what would happen if a water-cooled reactor breaks a major steam pipe. The LOFT reactor was a half-scale, fully operational pressurized water reactor, while Semiscale was a slightly safer experiment using an electrical heat source instead of fission to make the steam in a simulated power plant. These programs and the accidental experiments dating back to EBR-I were all valuable in finding how to build a safe power reactor and how not to build one. This knowledge was put to use in designing the Generation II nuclear reactors that now produce 20 percent of the electrical power in the United States. There would be commercial reactor accidents in America, but never a steam explosion, and the three men who stood on top of the SL-1 were the last people ever to die in a power reactor accident in this country.

Today, there are no ongoing reactor safety experiments, anywhere in the world.

Torturing nuclear reactors to make them give up the secrets to safe power production was not the only activity at the NRTS. Among the first building sites at the new reservation in 1948 was the Idaho Chemical Processing Plant, known to all as the “Chem Plant.” If the techniques for building civilian power plants were to be sorted out in the Idaho desert, then it made perfect sense to also work on fuel reprocessing and waste handling. A model plant was built to recycle the fuel used in reactor experiments and to develop practical methods for extracting the various components made in the fission process.

Commercial reactor fuel is uranium oxide, with two out of every three atoms in the solid material being oxygen. The uranium content in fuel is usually enriched to 3.5% fissile uranium — 235. The rest is uranium-238. After about 4.4% of the uranium-235 has fissioned, the fuel can no longer support the self-sustained chain reaction, and it must be replaced. Approximately 20.5% of the waste product embedded in the spent fuel is plutonium resulting from neutron activation of the U-238. The rest of the waste, 79.5%, is fission products, 82.9% of which are stable. That leaves 1.1% of the spent U-235 as radioactive waste which must be either disposed of or put to use as industrial and medical isotopes. The idea of fuel reprocessing is to remove the remaining U-235 and Pu-239 from the spent fuel and return it to the energy production process. As you can see from the breakdown of the used fuel components, the waste to be buried is a tiny part of the original fuel. In 1948 when uranium was thought to be scarce, it made no sense to bury an entire used fuel-load without breaking it down and sorting the portions.

The Foster Wheeler Company of New York, experts at making oil refineries, designed the plant, the Bechtel Corporation out of San Francisco built it, and American Cyanamid ran it. The Army had wanted to operate it under military control, but the AEC wisely argued that if it was to model a commercial process, then civilians should learn how to do it. Construction took 31 months on 83 acres of flat-as-pool-table desert north of Big Southern Butte. The first shipment of fuel arrived to be processed in November 1951.

Spent fuel arrived in heavily shielded casks, strapped down to flatbed trucks. A truck would make it past the security checkpoint and roll into a special bay in the storage building. Remotely controlled mechanical hands would take off the top of the cask and gently place the spent fuel in stainless steel buckets suspended from the ceiling. Using motorized overhead tracks, the fuel rolled into the long crane building and was diverted into its appropriate place to be processed. The fuel was dissolved and then broken down into components by specific chemical reactions. The fuel solution ran through stainless steel pipes and tanks, with the routings automatically controlled by pneumatic valve sequencers behind a shield wall in the building. Pressures, temperatures, flow rates, and tank levels were monitored and recorded. Every aspect of the facility was designed to shield human workers from any contact with radiation. There were radiation detectors and alarms everywhere, and to prevent possible power outages the plant had its own motor generator.

In general, the Chem Plant was well managed and well designed, and there was never a radiation injury or an accident that damaged the equipment. There were, however, three criticality accidents in which uranium dissolved in solution managed to find itself in a critical mass and go supercritical. Enriched uranium dissolved in water or an organic solvent will become an active nuclear reactor, increasing in power, if a specific “critical mass” is accumulated. The hydrogen in the water or the solvent acts as a moderator, slowing the fission neutrons to an advantageous speed, and even a fairly low U-235 enrichment level, like 3%, will overcome neutron losses by non-productive absorption in the moderator. This has been realized since the earliest days of reactor engineering, and those who work with uranium solutions are quite aware of the possibility.

The volume or mass of the potentially critical solution is not the only factor. Any shape that reduces the surface-area-to-volume ratio is a bad choice for a vessel that is to contain a uranium solution. In a worst-case configuration, such as a spherical tank, a minimum critical mass is needed to start a chain reaction, because the neutron leakage from the surface is minimized. Another example of a shape that is good for making an impromptu reactor is a cylindrical tank, especially one built with the “tomato can” height-to-diameter ratio. Tin cans holding food are purposely made to optimize the amount of material they can contain using the least amount of sheet metal, to lessen the manufacturing cost. A uranium solution shaped like a can is a disaster waiting to happen. If any concentration of uranium in solution is held in a tank in a reprocessing plant, then the tank has to have a seriously bad magnitude of surface area compared to its volume. It absolutely must promote neutron loss by surface leakage. The tanks are therefore vertically mounted, thin tubes. They look like thickened pipes.

The Chem Plant at the NRTS was not the only one being built in the world. Eventually Canada, England, France, the Soviet Union, and Japan would have fuel processing and reprocessing plants serving their nuclear power plants and, in a few cases, bomb manufacturing. I would like to think that not one of these plants was built having a container inside the building that could hold a critical mass and configuration of uranium in solution, but I would be wrong. Incredibly, there has never been a Chem Plant made that could not support a critical mass in at least one tank. Given time, uranium will eventually find this tank, usually by inappropriate means, and a problematic supercriticality will result. A death in a power-reactor accident is exceedingly rare, but many people have died worldwide in criticality accidents involving nuclear fuel.

On October 16, 1959, the graveyard shift was working on 34 kilograms of uranium fuel enriched to 91% U-235 in the form of liquid uranyl nitrate diluted with water. The next step of the processing was to extract impurities by mixing the nitrate solution with sulfuric acid in three steps. The first step had been completed, and the mixture was held in two vertical “pencil tanks.” These vessels were specifically designed to defeat criticality, being too small to hold the entire fuel load in one tank and being thin, measuring 3.050 meters tall and 0.125 meters in diameter. There was a tube leading from the drain end of the pencil tanks to a 5,000-gallon waste-receiving tank, looking like a tomato can. This tank was never, of course, supposed to have any uranium in it. It was there to hold the non-fissile waste products that were being extracted from the fuel. Just to make sure that it was impossible to siphon uranium solution out of the pencils or start a gravity drain, there was a loop in the connecting tube, located way above the top of the tanks. Only deliberate sabotage, it was thought, could cause any uranium to get into the receiving vessel.

An operator, reading his instructions, turned on two valves to spray some air into the two pencil tanks to stir it up and make sure that the acid and the uranyl nitrate were thoroughly mixed. Pencil tank number one had a pressure gauge on it so that the operator could make certain that he was applying the air at the correct sparge rate. Pencil tank number two did not have a pressure gauge, so the operator just opened the valve until he was sure the thing was good and sparged. Unfortunately, the excessive blast of air forced the liquid up through the anti­siphon loop, defeating it, and causing uranyl nitrate to siphon into the tomato can at 13 liters per minute.

The tank waited until it had 800 liters of 91% U-235 in solution before it went supercritical. Radiation alarms started going off all over the place. They were ignored. If you evacuated the building every time one of those hyper-active alarms sounded, nothing would ever get done in this place. The third time somebody hit the evacuation alarm, people started moving. Nobody took the clearly marked evacuation routes, only the well-worn paths that they took out of the building every working day. As a result, there was a log jam at the door. Fortunately it was a small staff for this shift, and everybody showed up at the guard shack alive and well.

In the initial blue flash, hidden by the stainless steel tank walls if anyone had been looking, a hundred million billion fissions occurred. There were several excursions, with the contents of the tank boiling furiously, which would dilute the moderator with steam and kill the reaction. The steam bubbles would then collapse, and the supercritical condition would start over and do it again. After about 20 minutes, half the water content of the solution had boiled away, and the unplanned reactor aborted itself.

The lessons learned from this accident were sobering. Those particular pencil tanks were seldom used, and nobody on shift that night had any experience with them, so they had to read the written instructions, which were out of date. Routinely used waste tanks had better anti­siphoning systems. This one did not. The evacuation procedure, which had never been used before, obviously needed work. It did not take a sabotage to put uranium where it was not supposed to go. It only took the turn of an unfamiliar valve.

On January 25, 1961, the Chem Plant had been down for a year of renovation and had been operating 24 hours a day for the past four days. At 9:50 in the morning, another batch of uranyl nitrate found an “unfavorable geometry” in the upper disengagement head of the H-110 product evaporator. This was thought impossible because of an overflow line in the head that was supposed to prevent it from holding enough uranium solution to be critical. Someone had cleared out a clogged line downstream using compressed air, and it managed to blow enough uranyl nitrate into the cylindrical vessel to cause another big boil-off. Nobody was hurt, and nothing was damaged, but again it called into question several philosophies and engineering practices. The general boredom of working a shift in a chemical processing facility may have had something to do with it.

Finally, on October 17, 1978, a slow leak in a water valve eventually let the uranyl nitrate concentration in the lower disengagement section of scrubbing column H-100 grow to a supercritical level. It was another non-damaging, zero-death, embarrassing reactor where there should not have been one.

The Chem plant is still there, but it is now called INTEC, the Idaho Nuclear Technology and Engineering Center. It is working on a liquid-waste-processing method as part of the Department of Energy’s Idaho Cleanup Project. The exciting days of reactor experiments are long gone, and the purpose of this federally funded effort is to erase radiological traces of the old NRTS off the desert. Now, irrigated circles of land, planted with Idaho potatoes, encroach on the property once alight with the technology of the future.

Despite all the fine development work and all the logical reasons for reprocessing, such as greatly reducing the throw-away waste product, there is no commercial fuel reprocessing plant in the United States. Our fuel would be buried whole, if it were buried. There is currently no place to bury spent fuel in this country, so it just piles up at the power-plant sites. All other countries relying on nuclear power as a base-load source of electricity have routine reprocessing and waste burial, from Great Britain to Japan.

In spite of three criticality accidents, the Idaho Chemical Processing Plant was probably the safest fuel reprocessing facility in the entire world. We will visit this topic again in glorious detail, but now let’s remain calm, go across The Pond, and see what the reserved and quiet Brits were up to.

was testing blast shields, boxcars, and explosive bunkers to see how they would perform when subjected to 250,000 pounds of TNT going off all at once. Although the Navy no longer owned the facility they were allowed to test 16-inch guns from the USS New Jersey battleship as late as 1970. Unexploded ordnance was still showing up on the ground in 1990.

93 Probability factors into all sub-atomic processes. In the case of neutron release, every 100 fissions in U-235 at thermal speed produce eventually an average of 243 free neutrons. Some of those neutrons are delayed, and may wait hours to release. In Pu-239, you get 290 neutrons per 100 fissions, but when high-speed neutrons cause fission in U-235, you also get nearly 290 neutrons.

94 Recently the phrase “fast breeder reactor” has been changed to “integral fast reactor.” I’m not sure why A sign on Highway 20 leading into the NRTS cautioned travelers, “warning: do not disturb breeding reactors.” It was a real knee-slapper at the time.

95 The use of plutonium in a fast-neutron reactor had already been proven. In 1945, an experimental reactor was built at Los Alamos in a deep canyon, far removed from other activities in case it misbehaved. At the time, the code-name for plutonium was “49,” and the scientists involved in the project were called “49ers.” You can probably guess the name of the reactor: Clementine. It ran experimentally at a maximum power of 25 kilowatts for six years, until a fuel-cladding failure shut it down for good. The dangerous coolant was pure mercury which would enthusiastically activate into radioactive Hg — 203. The purpose of Clementine was not to advance power-reactor technology, but to test bomb materials under the neutron-soak expected in a nuclear explos ion.

96 So it is written in the official history of the world, but nothing is that simple. On September 3, 1948, Logan Emlet opened the valve on a toy steam engine connected to a water pipe running through the air-cooled X-10 graphite reactor at Oak Ridge, Tennessee. The reactor, running at one megawatt, was making steam in the pipe, and the little engine started puffing. The flywheel was belt-driving a classroom demonstration generator, which was connected to a 1/3-watt flashlight bulb. It wasn’t much light, but it was definitely the first. Everything done on the X-10 was still secret, so this historical generation of electrical power by nuclear means was buried. Buried deeper was the first use of a reactor to heat a building, which occurred in England in the fall of 1948. The reactor was named “Bepo,” meant to sound like an unknown Marx brother. I’m not making this up.

97 In the popular literature, I have seen the initial rate of power-climb for EBR-I listed as “doubling every 60 seconds.” Not quite true. The “period” of reactor power increase or decrease is expressed in “e-folding time,” or the time required for the power to change by a factor of e, where e is the root of the natural logarithm, 2.718281828459045… . In breeder parlance, “doubling time” is actually the time required for the amount of bred plutonium to increase by a factor of two.

98 Not to be outdone by the Air Force, the U. S. Navy in 1954 commissioned a study by E. W. Locke Jr. to find the feasibility of an atomic-powered dirigible. That’s right, a rigid airship filled with two million cubic feet of helium with a feather-light nuclear reactor driving two T56 gas turbine engines. The design combined two dubious technologies: an enormous, lumbering military air vehicle blown around by the wind, and an unshielded nuclear power plant weighing less than 40,000 pounds. The Navy decided instead to build a nuclear-powered float plane (the Princess Project), but in 1959 Goodyear Tire and Rubber invested time in preliminary designs of a nuclear blimp. Francis Morse at the University of Boston proposed a 980-foot-long nuclear dirigible for the New York World’s Fair in 1964. It would be a “flying hotel” carrying 400 passengers. He argued that the spread of radioactive debris in the event of a crash would be manageable, because dirigibles crash softly Fortunately for the public impression of nuclear technology, none of these plans were implemented.

99 There were two nuclear jet engine designs in the ANP program: the direct cycle at GE of Ohio, and an indirect cycle at Pratt & Whitney of Massachusetts. For the indirect cycle, an intermediate heat exchanger would transfer heat from a centrally located reactor to multiple jet engines, while it was assumed that in the direct cycle a small reactor would take the place of the fuel burners in the middle of the jet engine. The P&W design was complicated, and its development was at least a year behind the GE engine. The ideal circulating coolant for the indirect cycle engine turned out to be lead, which seemed a cruel material to be used on a high-performance jet.

100I first saw the HTRE-3 and HTRE-2 in 1980. They were near the security checkpoint for TAN. They were still considered to be radiologically unapproachable, and to examine them closely you had to use binoculars. A fellow who had worked on the project damned HTRE-3 with faint praise, saying “It was so powerful, it could practically lift its own weight off the ground.” Today the two engines are tourist traps. You can go up and take a picture of your kids pointing into the exhaust nozzles. They are in the parking lot of the EBR-I, which is a National Historic Landmark, opened for touring between Memorial Day and Labor Day.

101There is a bit of confusion here. The NRTS records show that the HTRE-3 operated between September 1959 and December 1960, but this account is taken from Summary Report of HTRE no. 3 Nuclear Excursion. APEX-509, and it places the accident in 1958. This type of event was usually classified SECRET, and the operating schedule may have been distorted to hide it.

102I’m not sure there was anywhere to eat near the test stand, so they probably brought lunch with them or had it trucked in. I once had lunch at what was possibly the only restaurant within 40 miles of the HTRE test stand on Highway 33, called the “Broken Wheel.” As I stared out the window at the featureless, dun-colored desert, suddenly the ground-cover moved and a ripple went through it. An earthquake? No, as it turned out I had been looking at a vast herd of sheep, covered with dust and huddled close together against the extreme cold.

103Hold on to your seat. Three quarters of the free world’s supply of mercury was used to shield the HTRE-3. At the end of the project it had to be released slowly back into the market to prevent an economic crash in the liquid metals trade.

104Although I and everyone else call it BORAX-I, it may not have been known as a numbered unit until BORAX-II was built. Contemporary reports from the field simply call it “The Borax Experiment.” Local newsmen called it “The Runaway,” and this name stuck to it like cobalt-60 contamination.

105I could not at this writing be certain how the central control was blown out of the core. Some accounts say compressed air, but others say it was an explosive charge or a cocked steel spring. The pneumatic cylinder seemed most likely, but other mechanisms are possible.

106There had been serious talk of burying a case of dynamite under the reactor vessel to ensure a visually satisfying event in case the steam explosion fizzled. I find no record of this ploy being carried out.

107Although the plans for Camp Century were profiled in the Saturday Evening Post in 1960, its military purpose was not revealed to the public until January 1997, when the Danish Foreign Policy Institute spilled the beans in a report to the Danish Parliament. Greenland, the site of the missile base, is owned by Denmark.

108Some accounts say that the rod was pulled 20 inches, but the revised figure of 23 inches is based on careful reevaluation of the data. The rod was pushed out an additional 7 inches by the upward force of the steam blast. The weight of the master control was originally recorded as 85 pounds, but this did not take into account the weight of the rack plus the handling rod.

109See it on YouTube. http://www. youtube. com/watch? v=0FIhafVX_6I&feature=related

110On May 3, 1958, Frederic de Hoffman announced the introduction of the Test, Research, and Isotope reactor of General Atomic, or the TRIGA. It was a brilliant design, started as an exercise for young nuclear engineers by Dr. Edward Teller, co-inventor of the H-bomb and the inspiration for the movie “Dr. Strangelove, Or How I Learned to Stop Worrying and Love the Bomb.” Dr. Freeman Dyson, also a nuclear genius, contributed to the concept, and the design was influenced by findings at the NRTS in the BORAX and SPERT programs. The TRIGA pool reactor was “safe even in the hands of a young graduate student,” which is saying a lot. The unique fuel formula was a mixture of uranium and zirconium hydride. Being co-located with the uranium, the hydrogen moderator would heat instantly in the event of a fission runaway and the hot hydrogen would lose its ability to moderate the neutrons down to the advantageous low speed. The result was a reactor that absolutely could not be made to explode or melt down. The TRIGA is still available from General Atomics of San Diego, California. Three new ones were sold recently overseas.

111 There were actually seven SNAP-10As built. Three were blown up at the NRTS, one was a spare, two were used for flight system ground tests, and only one was orbited.

112What burned, causing a “fireball?” Ask yourself, why is fire visible? Why does fire glow bright yellow? The answer is sodium contamination. Sodium atoms glow yellow when heated by an otherwise invisible flame, and the slightest trace of sodium in a fire is what makes it look like fire. In the case of SNAP-10A, it used nack, or a sodium-potassium alloy as the coolant. There was plenty of sodium on hand to light up the event when the reactor violently overheated. The sodium and potassium reacting explosively with the water topped it off.

113I have been unable to find a report that describes the destruction of SNAPTRAN-1. I’m not sure whether it was too insignificant to warrant a report, or too significant to be declassified.

Chapter 5