"Will you please issue the following operating instructions to the operator engaged in controlling the Wigner Energy Release. If the highest Uranium or Graphite temperature reaches 300°C, then Mr Fair, Mr Gausden and Mr Robertson are

114

to be informed at once, and the PCE alerted, to be ready to insert plugs and close the chimney base.”

—D R R Fair, Manager, Pile

The atomic enthusiasm of the 1950s was supposed to acclimatize the general public to all things nuclear and prepare us for a future that was in the advanced planning stage, but just the opposite seemed to be happening. Instead of getting used to it, people seemed to develop general fears and anxieties that in the previous generation had existed in railway stations. This was true even among the servicemen who would be tasked with deploying nuclear weapons systems and remote power plants and fighting in conflicts using this new paradigm of warfare. In the case of the civilian public, a problem was the overbearing secrecy of the entire nuclear business. There is nothing more frightening than the unknown. In the case of the armed forces, it was an excess of knowledge.

Servicemen had been subjected to the flash, the thunderclap, and the ground shock of an atomic-bomb detonation in multiple test exercises using real weapons and real soldiers. In the next war, the infantry would have to move forward into territory that had just been sterilized by the radiation pulse of a nuclear detonation, moving toward ground zero as the mushroom cloud formed in front of them, wearing only light protective gear. This test series was both a confirmation that this maneuver was possible and an effort to allay the soldiers’ fears. They had to be convinced that they could advance into the freshly destroyed target area without dropping dead from some invisible, undetectable agent. The men had been prepared for the experience by sitting through several mass lectures, hearing about rems, rads, roentgens per hour, the importance of beating the dust off your clothing, symptoms of radiation poisoning, and how to aim a rifle while wearing a respirator. It was more than they wanted to know. The fact that the AEC observers were wearing full-body radiation suits and waving Geiger counters did not help.

As early as 1951, the Air Force had pushed for an atomic weapon that could be used against massed air attacks, and by January 1, 1957, Project Bell Boy had produced an air-to-air nuclear-tipped missile that could be launched from an F-89J pursuit plane. It looked short and fat, with a bulging nose cone and stubby fins. It had a solid-fuel rocket engine in the tail and no guidance system. The beauty of firing a nuclear warhead at another airplane was that you didn’t need a guidance system or even a particularly good aim. Any airplane within a mile of it would be destroyed as the 2-kiloton warhead exploded and made a hole in the atmosphere.

The warhead designation was changed from EC 25 (Emergency Capability) to fully operational MK 25 Mod 0 in July 1957, just before its proof of function and weapons effectiveness trial at the Nevada Test Site. The test was scheduled for July 19 in Shot John of Operation Plumbbob. The rocket-propelled weapon was designated MB-1, or, affectionately, “Genie.”

Genie was a well-designed system, and eventually 3,150 units would be manufactured and stored safely away, waiting for an appropriate war. There were two problems with Genie, mostly of a philosophical nature: there was nothing to use it against, and the troops were scared to death of it.

The concept of a massed air attack, in which a squadron of heavy bombers would blot out the sky and rain gravity bombs down on cities, was from World War II. It was a strategy used by the United States Army Air Force against enemy assets in Germany and Japan, and not the other way around. America had actually never seen a bomber group dropping explosives on it. We had therefore invented the perfect weapon for blowing up an entire sky full of multi-engine aircraft in one swat, so we could have defeated ourselves two wars back. If the UK had had a few Genies in 1940, the Battle of Britain could have been over in about 20 minutes, but the idea of attacking North America using a close formation of airplanes had never been seriously considered. In the Cold War era there was basically nothing to shoot down that an inexpensive Sidewinder air-to-air missile would not take care of.

Be that as it may, the problem of human squeamishness at having an A-bomb explode overhead could be addressed. Simply explaining to soldiers that a nuclear detonation at 10,000 feet was not the same as having it go off at 1,000 feet was true but insufficient. To the soldiers it was a matter of degree. At the high altitude there would be no ground disturbance. No radioactive dust kicked up into a mushroom cloud, no neutron activation of the ground, and negligible fallout. It was all a function of range. The fission neutrons could not travel that far in air before they decayed into hydrogen gas, and the gamma ray pulse would be short-lived and dissipated in a spherical wave-front with a diameter of four miles when it hit the ground.

Air Force Major Don Luttrell had a master’s degree in nuclear engineering, and he did not require convincing, but he came up with an idea to calm the fears of those unwashed by the firehose of knowledge. He persuaded four other officers and a camera operator to stand with him directly under the detonation point of Shot John and prove on film that the weapon was perfectly safe unless you were flying in a bomber group.

The camera man was George Yoshitake. For protective gear he wore a baseball cap as he filmed five officers squinting up into the sky, standing by a crude sign saying “GROUND ZERO,

POPULATION: 5,” disregarding George as a participant.115 The F-89J interceptor fired the Genie at a coordinate in the air directly over the men. It traveled the 20,000 feet from the plane in 4.5 seconds and exploded, causing a brilliant burst of light. In the bright desert sun the photon flash fell over the men and briefly washed out the picture. They felt the wave of heat, like opening the door on an oven. The shock wave followed in a few seconds, causing them to cringe from the thunderclap as they watched the bright spot turn into a red ball of fire, eventually disassembling into a weird atmospheric display. It was a cloud of white mist surrounded by an orange donut. There was no debris to fall, as the rocket and its payload had been reduced to individual atoms.116

The film was shown to military personnel likely to deal with nuclear weapons, but not to the public. The average citizen had no idea that such a weapon existed, regardless of President Dwight Eisenhower’s Peaceful Atom proclamation that declassified much of the atomic bomb development activities. The engine of the atomic submarine Nautilus, which was destined to become the model for standard civilian nuclear power plants, was also classified secret.

Typical of the public’s concept of a nuclear reactor was shown in 1953 on the very popular television program, The Adventures of Superman, starring George Reeves as the Man of Steel. It was episode 33, “Superman in Exile,” in which Clark Kent detects an atomic pile running out of control 100 miles away. He rips off his glasses and ducks into a janitor’s closet where he can change his clothing. Jumping out an open window, he flies to the reactor site and finds a scientist in a lab coat, obviously suffering badly from the radiation load, trying to push a control rod back into the face of the pile. Superman, who can withstand just about anything, pushes the rod home without breaking a sweat, and the world is saved from an impending

reactor explosion.117

From a nuclear engineering perspective, there are several things wrong with this picture, the first being the manually operated control. A reactor control rod had not been moved by hand since 1942, when the original CP-1 was in operation in Chicago, and even that rudimentary pile would have automatically shut down if any part of its operation were out of normal bounds. The fact that the reactor was shown as a vertical wall painted white with a matrix of round holes in it was modeled after the X-10 reactor (the “Clinton Pile”) at Oak Ridge, which everyone had seen in the newsreels and a few still pictures. It was the graphite-moderated, air-cooled, low-power job that had been banged together during the war to test fuel slugs for the plutonium production reactors being installed at Hanford, Washington, and it was probably the only reactor configuration that civilians had ever seen. The loading face of the pile, which was painted white, was a seven-foot-thick concrete wall, acting as a bio-shield for workers standing in front of it.

An impressive science fiction film in 1956, Forbidden Planet, starring Leslie Nielsen and Anne Francis, did greater harm with its depiction of a nuclear reactor. In the movie, which was loosely based on William Shakespeare’s shot at sci-fi, The Tempest, Nielsen and his crew land the flying saucer C57-D on the planet Altair-IV and find two survivors of an exploration party that had landed 20 years ago, ‘ in an abandoned extra-terrestrial civilization. Nielsen decides to contact Earth for instructions on dealing with this odd situation, and in a refreshing twist of drama such a message is not easy to send. Earth is 16 light-years away.

To accomplish this feat it is necessary to dig a shielding trench and remove the ship’s power reactor to drive the transmitter, which must be assembled in situ. At this point any remaining credibility is blown away, as the men are shown hauling the graphite reactor out of the engine room. Nuclear engineers watching this movie cringe as they see an unshielded core, which had just been used to hurl a ship across interstellar space, pulled casually through the crowd of crewmen with a motorized crane. The naked core would have painted them all with a withering blast of fission-product radiation. This is what the public saw of reactor design and practice: a technology full of danger that was safe as long as it was turned off, and neatly blocked piles of graphite with cross-holes drilled in them and stuffed with uranium.

It is an exaggeration to say that the British Atomic Energy Authority after the end of World War II had about the same picture of how a nuclear reactor looks as the set designers of The Adventures of Superman, but not by much. The only reactor that the British scientists and engineers had ever seen was the X-10 pile at Oak Ridge, the first and almost the last

megawatt-capable air-cooled reactor ever built in the United States.118

The British had contributed greatly to the war-time atomic bomb project with a special delegation working at the Los Alamos lab in New Mexico, providing us with personnel ranging from William Penney, a brilliant mathematician, to Klaus Fuchs, the man who spilled every secret he could get his hands on to the Soviet Union. The Brits were useful and trusted, and they knew everything about atomic bomb theory and construction techniques. Everything, that is, except for the reactors. They were not allowed anywhere near the plutonium production reactors or fuel-processing facilities at the Hanford Site. The bombs were top secret, but the water-cooled graphite reactors, being extremely valuable industrial assets, were even more so. Just about any country having some physicists and engineers could figure out how to build an A-bomb, but producing the materials for this bomb was where the secrets lay. After the war was over, the British were very disappointed to learn that all the camaraderie and warm feelings of brotherhood were blown away by the United States Congress Atomic Energy Act of August 1946, forbidding any sharing of atomic secrets with anyone, even close allies. The Brits were left to fend for themselves in the twisted new world of Cold War and Mutually Assured Destruction. All they had in the world was Canada, an ambitious prime minister, a tour of the X-

10 pile, and a willing spirit.119

William Penney, fresh from working for the Americans on blast effects studies at the Bikini Atoll tests in 1946, was put in charge of the British atomic bomb development. Bill Penney was born in British-owned Gibraltar in 1909 and reared in Sheerness, Kent. Early interest in science and primary education in technical schools led eventually to a Ph. D. in mathematics from London University in 1932. After that he did time at the University of Wisconsin-Madison as a foreign research associate. This work persuaded him to change his career from math to physics, and he made it back to England, applied to the University of Cambridge, and earned a D. Sc. in Mathematical Physics in 1935.

In front of newsreel cameras, Penney always had the silliest grin, speaking with a back — country drawl and answering questions with the intellectual presence of a slow-witted kindergartner, but underneath it he was a razor-sharp scientist with experience and an ability to make people work together in harmony. As the guiding light for the steadfast British nuclear weapons program, he was awarded every honor, culminating in Queen Elizabeth II granting him the title The Lord William George Penney, Baron Penney.

Putting things in the order of priority, the first thing would be to figure out how to build an atomic pile. A heap of graphite called GLEEP (Graphite Low Energy Experimental Pile) was assembled at the new research center at Harwell, an abandoned World War II airfield in Oxfordshire, in an airplane hangar. It was first started up on August 15, 1947, and was used to

get the hang of how a nuclear reactor works.120 Time was of the essence. A month later, before there was any significant experimental work using GLEEP, construction of the first plutonium production pile began at a spot called Windscale.

Seascale was a vacation spot on the northwestern coast of England, or it had been during the Victorian age. Now it was a depressed area. A couple of hundred yards inland was an abandoned royal ordnance factory named Windscale, and here the British nuclear industry would begin. It was in the middle of dairy-farming country, and putting open-loop, air-cooled reactors there made as much sense as installing a fireworks stand in the middle of a high school auditorium. So be it.

The two production reactors would be like the X-10, only larger, with more capacity for making plutonium. X-10 was basically a short cylinder of solid neutron-moderation material, not perfectly circular but octagonal, laid on its side with holes bored clean through it to hold uranium fuel. A long platform in front moved up and down and would allow men, working like window washers, to poke little fuel cartridges into the holes on the vertical face. Each fuel element was metallic, natural uranium, having the small U-235 content allowed in nature, sealed up in an aluminum can, about the size of a roll of quarters. Using metal poles, workers could push in new fuel on the face of the reactor, and used-up fuel, still hot from having fissioned to exhaustion, would fall out the back, landing in a deep pool of cooling water sunk into the floor. It would be a terribly clumsy way to make a power reactor, but as a plutonium production pile the fast turnaround of the inefficient fuel and the enormous size necessary to keep a chain reaction going were perfect. Instead of wasting a lot of effort trying to make electricity, all exertion would be to convert the otherwise worthless uranium-238 in the fuel into plutonium-239, and the power was thrown overboard. A short time in the neutron-rich environment for the fuel meant that the probability of plutonium-239, the ideal bomb material, being up-converted into the undesirable plutonium-240 was minimized.

The two Windscale reactors were huge. The core, built like X-10, was 50 feet high and 25 feet deep. The fuel-loading face was covered with a four-foot-thick concrete bio-shield, backed with six inches of steel and drilled with the holes for inserting fuel cartridges into corresponding channels cut in the core and running clean through, horizontally. There were 3,440 fuel channels. Each square array of four fuel channels was serviced from one hole in the loading face, normally sealed with a round plug. Every fifth horizontal row of access holes had the positions numbered from left to right. When running, the core would be loaded with 21 fuel cartridges in each channel, or about 70,000 slugs of metallic uranium. The fissions would be controlled using 24 moving rods made of boron steel, engineered to absorb neutrons and discourage fission, trundling in and out using electric motors wired to the control room, located in front of the building. A scram of an emergency shutdown was handled separately, using 16 additional control rods inserted into vertical channels. Under normal operation, these rods were withheld using electromagnets. If anything went wrong, electricity to the magnets was cut and the heavy rods would fall by gravity into the core, shutting it completely down.

The first set of plutonium production reactors at Hanford were water-cooled, but even the Americans admitted that this scheme, while elegant and impressively complicated, invited a disastrous steam explosion. Let a water pump fail, and the coolant stalled in the reactor would flash into steam, sending the works skyward. Besides all that, unlike the Yanks, the Brits had no mighty river like the Columbia to waste as an open-loop cooling system. Using seawater was a possibility, but there would be destructive corrosion. Penney’s design team decided to do it the easy way, just like X-10, blowing air through the loose-fitting fuel channels and up a smokestack, sending the generated heat and whatever else managed to break loose up into the sky and out over the Irish Sea. Each reactor would be equipped with eight very large

blowers, two auxiliary fans, and four fans dedicated to shutdown cooling.121 Each main blower was a monster, driven by a 2,300-horsepower electric motor running on 11,000 volts. The exhaust stacks were designed to be an imposing 410 feet high, made of steel-reinforced concrete.

The Windscale Unit 1 plutonium production reactor, shown from the top looking down. Not shown are the two auxiliary buildings, left and right, containing air-blowers the sizes of double-decker buses. The water duct was used to cool off the used fuel as it was poked out the back of the graphite reactor core and move it out of the reactor building for plutonium extraction.

Such a reactor could be made using heavy water as the neutron moderator, as the Canadians were demonstrating, but it was cheaper and easier to use graphite, just like the X-10. It would take 2,000 tons of precision-machined graphite blocks to make one reactor.

The Windscale Unit 1 reactor, shown from the left side. Only a small portion of the chimney is shown so that the diagram would fit on the page. The charge hoist was a movable platform used to position workers on the front of the reactor, located behind a thick concrete shield and the space for cooling air to enter the fuel channels from the front.

Graphite is a strange and wonderful material. It is a crystalline form of carbon. So is diamond, and a diamond is the hardest material on Earth, hard enough to saw through a sapphire. Graphite is completely different, being soft enough to cut with a butter knife and be used to lubricate automobile window channels. In recorded history, an enormous deposit of natural graphite was first discovered on the approach to Grey Knotts from the town of Seathwaite in Borrowdale parish, Cumbria, England, about 13 miles northeast of Windscale. Locals found it exceedingly useful for marking sheep, and news of this proprietary livestock branding method leaked out in 1565 after decades of use. Expanding on this theme, entrepreneurs in Cumbria proceeded to invent the lead pencil, and from this wonderful application the mineral acquired its official name from the Greek word grapho, meaning to write or draw.

As happens to many such discoveries, a military use was soon found and the English government clamped down on the source. It had been determined that lining the molds for making cast-iron cannonballs with graphite resulted in smooth, well-thrown projectiles, and the military-industrial complex of 16th century England was well pleased. Afterward, the manufacturing enterprise found myriad uses for the fine, pure English graphite from Cumbria, from arc-light electrodes to the throw-out bearings for MGB sports cars. British industry thus had a long and complete history of working with graphite. They may not have known much about working with uranium in a controlled-fission environment, but they knew their black, greasy mineral like the bottom of a Guinness glass.

The United Kingdom, still aching from the post-war abandonment, was trying to impress the United States nuclear establishment with their rapid ascent to atomic power status and thus reestablish a badly needed intimate connection to the material and industrial strength of its former colony. By showing that they were on equal footing and had expertise to contribute, they wished to demonstrate that an Anglo-American nuclear alliance could be a strong bulwark against the Red Menace that was having its way with Eastern Europe. The Windscale construction job was one of the largest, most time-pressed in English history, employing nearly 5,000 workers, including more than 300 surveyors, architects, and building engineers. Everything was in short supply except determination.

The Americans, irritatingly miles ahead of the Brits in these matters, were hard to impress, but they were concerned with what they had heard about the British plutonium production initiative. In 1948, a team from Los Alamos slipped into the headquarters at Harwell to give some advice. There were a couple of days of classified seminars with Bill Penney’s top scientists. All the talk came down to this: Whatever you think you know about graphite is wrong. The conversation between the American scientific delegation and their British counterparts might have gone like this:

“For example,” offered the Yank, “there’s the Wigner Growth.”

The Brit lowered his teacup slowly, seeming to twitch slightly. “Say what?”

“The Wigner Growth. If graphite is exposed to fast neutron flux, as it will be in your production pile design, the recoil action of neutrons colliding with carbon atoms will displace these atoms in the graphite crystal. Over time, changing the distance between atoms changes the physical size of your graphite block. It seems to grow.”

“But how do you… ,” Nigel sputtered.

“Control it? You don’t. You have to allow for it in the design. The only thing you can control is the direction in which it grows. If you make your blocks by extruding them, then the blocks will lengthen only at right angles to the extrusion axis.”

“Well, dash it all.”

It was best to learn of this wrinkle early on in the construction. Heroic redesign of the core allowed each block to expand horizontally, at right angles to the axis of extrusion, while being held in place with graphite slats. By March 1949, word had arrived from hastily convened experiments at Harwell, trying to replicate the effect claimed by the Americans. British graphite, so wonderful for making pencils, was completely different from the synthetic graphite they used in the U. S.A. It expanded in all directions. That was bad. The prediction was that after running just 2.5 years, the pile would be warped and unusable. The fuel channels would close up and trap the aluminum canisters in the core. The Canadians came through with a modified prediction. Yes, British graphite would expand on all axes, but only at one fifth the length of the American product. That was good. Under that condition, the pile might operate for as long as 35 years, if the internal stresses did not crumble it like a tea biscuit. Other potential problems were revealed too late to be designed out so easily.

Later in 1948, Cockcroft, head of the entire British nuclear enterprise, came back from a fact­finding tour of the X-10 at Oak Ridge with some more disturbing news. They would have to filter the pile-cooling air before releasing it to the general atmosphere. Of all the 70,000 fuel canisters in one pile, if the delicate aluminum case around just one of them were to break open, then its highly radioactive contents would go straight up the chimney and rain down on the dairy farms of Cumbria. That could be a problem. When building their improved version of the X-10 up on Long Island, New York, the Americans had put filters between the atomic pile and the air exhaust stack, just to prevent a fission product spread if the fuel broke apart or caught fire. “We shall do the same,” pronounced Cockcroft.

Impossible. The base of the Unit 1 chimney had already been poured, and 70 laboriously laid feet of vertical brickwork was already in place. If filtering were necessary, then it should have been designed in to begin with, in the gallery between the core and the chimney base. There was no way to tear the thing down and start over, and, at this late stage, the only place to put filters would be atop the chimneys. Cockcroft was adamant, and he was in command. The filter assemblies, aptly named “Cockcroft’s Follies,” were built as specified, using 200 tons of structural steel, concrete, and bricks hauled up 400 feet to the tops of the air stacks.

Several filter packs were tried. In early 1953, a temporary lash-up was settled on. The filters would be fiberglass tissue, sprayed with mineral oil to trap dust made radioactive by going through the reactor core and any fuel that might disintegrate and escape. There was much grumbling, not only among the men who had to retrofit this ghastly mess, but from Penney’s bomb makers. To make plutonium at the necessary rate, a ton of cooling air had to go up each of the two stacks every second. That meant that the hot air had to be moving at 2,000 feet per minute as it exited at the top, but at that point it would hit the drag-inducing filter pack like a brick wall. Delicate fiberglass tissue would quickly come apart, and the oil would be blown off the fibers. The air speed would have to be reduced, and this would mean less plutonium per month. The Canadians would have to pick up the slack using their heavy-water reactor at Chalk

River.122

With further improvements and changes in the filter packs, including substituting silicon oil for the mineral oil, Cockcroft’s follies were preventing the occasional radioactive dust particle from ejecting into the atmosphere. An exception was the volatile fission product iodine-131. As a gas, it was largely unhindered by the filters. There was nothing to worry about. When one was striving to build an arsenal of weapons, one of which can obliterate a large city, it seemed almost inappropriate to fret over probabilistic health effects on individuals. At this point, production speed outweighed all but the most basic safety concerns.

On they labored. Engineering problems were knocked down one at a time. Of particular concern were the fuel canisters. The metallic uranium, which would catch fire spontaneously if exposed to air, had to be cast into small cylinders a few inches long and sealed up in aluminum cans with heliarc-welded seams. The hot uranium would react chemically with the aluminum, so the inside of each can was coated with insulating graphite. The uranium slug would expand as it heated and burst the can, so it had to be made to fit loosely. Each can was filled with pressurized helium to ensure heat conduction to the aluminum, and the assembly was covered with cooling fins. In early summer 1950, Cockcroft threw another serious monkey wrench into the business. New calculations seemed to indicate that the critical mass of Pile. No. 1 would have to be increased by as much as 250 percent, or it would not work.

Reeling briefly with this news, the design team proceeded to inventory every material in the reactor that would parasitically absorb neutrons, affecting the core reactivity. There was one item that could be reduced enough to compensate for the lack of critical mass: the fins on the fuel cartridges. In three weeks the team managed to trim one sixteenth of an inch off each of the one million cooling fins, thus solving the problem.

In October 1950, craftsmanship triumphed over knowledge, and the Windscale Pile No. 1 achieved self-sustaining fission. By January 1951, used fuel cartridges had been chemically processed, and Tom Tuohy, the Works General Manager, held the first lump of British plutonium in his hands. In June 1951, Pile No. 2 became operational, and plutonium production was proceeding at full capacity. The people of the United Kingdom under hard postwar circumstances had put their backs into it and prevailed.

There were problems. On May 7, 1952, there was an unexplained temperature rise in Pile No. 2, only in the upper portion of the core. The operators were able to bring the temperature down with the fans, but there was not a clue as to why this had happened. In September the same thing happened to Pile No. 1, but this time there was smoke coming out of the stack. Was the graphite burning? They had been warned by the Americans: Whatever you do, do not let the graphite catch fire. Once it gets going, water will not extinguish the fire. It will only make it burn hotter, and the graphite sucks the oxygen out of the water and leaves you with explosive hydrogen. Analysis showed that the smoke was caused by lubricating oil leaking from a fan bearing, but the high temperature remained inexplicable.

In May 1952, Pile No. 2 was taken down for maintenance. The workers found that 2,140 cartridges had migrated out of the fuel channels. Some were hanging precariously out the back of the core, and some had flown over the pool of water below and into the wall behind it. The air flowing from front to back had literally blown them out of the reactor. Each fuel cartridge had a little graphite boat under it, so that the cooling fins would not make it stick in the channel, but this would have to be changed. A worse finding was that the Burst Cartridge Detection Gear (BCDG) had punched a hole in the end of a cartridge, putting fission products in the air stream.

There were eight BCDGs, called “Christmas trees,” in each reactor. A Christmas tree was a rectangular matrix of 32 vacuum nozzles, arranged to fit over any 4-by-8 array of exit holes in the back of the reactor core. It could be positioned remotely from the control room to sniff the holes, looking for escaping radioactivity that would indicate a broken fuel can, but the operation was completely blind. From the control room or even from the face of the pile where fuel was pushed in, you could not see the BCDGs in action. During normal operation the eight of them would crawl over the back end of the pile, like very large insects, looking for trouble. It was a good idea to have equipment that could tell exactly which hole was leaking, but it could be too strident and cause what it was trying to detect, punching the vacuum nozzle through the aluminum. Some fuel cartridges were even jammed into the frames of the Christmas trees, never making it to the recovery pool below for plutonium extraction.

The American delegation made another informative visit, this time bringing the big guns, Dr. Edward Teller, the brilliant Hungarian theoretician and Mother of the H-bomb, and Dr. Gioacchino Failla from the Columbia University Radiological Research Laboratory. They could

explain the mysterious temperature transients in Piles No. 1 and 2.123 Technically, it was illegal to give such information to a foreign power, but the Brits had to be informed before their entire atomic bomb program went up in smoke.

There is another Wigner effect, called Wigner Energy. The same phenomenon that would bend the crystalline structure of graphite would store a great deal of potential energy in the material. If you allowed this energy to accumulate over a long period of time, it could reach a break-down point, at which it would all release at once, igniting the graphite with extremely high temperature and sending your plutonium production machinery up the chimney. The way to keep this from happening is to stage a periodic annealing, in which the core is heated to an abnormally high temperature, about 250°C, using nuclear fission with reduced cooling. At this point a “Wigner release” should occur, with the graphite providing its own heating without the need for fission. Shut down the reactor, and adjust the fans to slowly bring down the temperature.

It was not quite that simple, but the Atomic Energy Authority appreciated the heads-up, and thanks for not waiting until the Windscale facility was wiped out to let us know what had happened. The Windscale piles were very large, and Wigner Energy could collect in various regions or pockets in the graphite stack, meaning that the pile would have to be selectively heated and annealed by skillful use of the controls. There was never a written procedure for annealing. It was more of an art than a science. The first anneal on Pile No. 1 was in August

1953, and they were scheduled for once every 30,000 megawatt days of operation.124 There were eight anneals from the first until July 1957, and during the first operation three scientists hovered over the operators, giving advice and asking questions. After that, it seemed like a routine task, and no science was needed.

The two Windscale piles, with some help from the Canadian NRX, produced enough plutonium for an official British atomic bomb test on October 3, 1952. The blast, occurring under water a few hundred yards from Trimouille Island, Australia, released a respectable 25 kilotons of raw energy, digging a crater 20 feet deep and 980 feet across. William Penney’s bomb design crew and the efforts of thousands working at Windscale had paid off in the most visible way. This would prove to the United States that Britain had achieved parity in the arms race, and an immediate summit meeting was expected.

Unfortunately for this motive, a month later the United States set off “Ivy Mike,” the world’s first thermonuclear bomb on Elugelab Island at Enewetak Atoll, releasing the energy equivalent of 11 million tons of TNT high explosive. Elugelab Island vanished, replaced with a crater 64 feet deep and 6,240 feet across. The British arms industry would have to go a bit farther to come up even with that.

Penney’s team had the imposing task of coming up with a thermonuclear weapon design quickly, starting from scratch. They had not so much as an encouraging word from the Americans, and making hydrogen isotopes fuse explosively was not an easy problem. It was only obvious that a source of tritium, the heaviest isotope of hydrogen and one most likely to fuse, would be necessary.

There is no natural source of tritium, and, like plutonium, it must be manufactured using fission reactors. To accomplish this, a rod of lithium-magnesium alloy, about half an inch in diameter, is encased in a sealed aluminum can and pushed into one of many special “isotope channels” in the reactor. Neutrons from the fission process are captured by the lithium-6 nuclide component of natural lithium, and the atom subsequently breaks down into one helium atom and one tritium atom. The helium pressurizes the can, and the tritium combines chemically with the magnesium component of the alloy, becoming magnesium-tritide. After being in the reactor for about a week, the rods in several cans are harvested and chemically processed to remove the pure tritium. So far, so good.

The tritium production cartridges were given the code name “AM,” and the Mark I cartridges were built using standard fuel cans with a lead weight added so that they would not fly away.

The Mark II cartridges were an improvement, having the lithium-magnesium rod diameter increased to 0.63 inches. Under the extreme needs of the hydrogen bomb program, the even more improved Mark III cartridges were built using thinner cans, no lead weight, and alloy rods an inch in diameter. The Mark III’s were admittedly dangerous. The lithium-magnesium rods were pyrophoric, meaning they would burst into hot flame and burn like gasoline if they were exposed to air. The cans were as thin as possible, and the helium pressure could blow them open if the temperature was as high as 440°C. In addition, there were now so many AM cartridges in the Windscale cores, they dragged the fission process down. Absorbing neutrons without adding any to the fission process made the reactor subcritical. To work at all, the reactor fuel had to be beefed up with a slight uranium-235 enrichment, coming from the new

gaseous diffusion plant at Capenhurst.125

On January 9, 1957, the British Prime Minister, Anthony Eden, having just presided over the political disaster of the Suez Crisis, resigned from office after being accused of misleading the parliament. The British Army had done a splendid job of tearing up Port Said, Egypt, with French assistance, but internationally it was seen as the wrong force applied at the wrong time as a reaction to Egypt having nationalized the Suez Canal. Eden was succeeded by Harold Macmillan, who desperately wanted to recapture the benevolence and camaraderie of the United States, and the hydrogen bomb initiative was the point of the spear. It would proceed at an ever-accelerated pace.

By May 1957, Penney’s group had put together the first British thermonuclear test device, code named Short Granite, to be exploded in Operation Grapple I off the shore of Malden Island in the middle of the Pacific Ocean. Time was becoming crucial, as a nuclear test-ban treaty was in the works, and the end of unrestricted nuclear weapon experimentation was in sight. The expected yield was north of a megaton. On May 15 Short Granite was dropped from a Vickers Valiant bomber, and it was an embarrassing wipeout, giving an energy release of

only 300 kilotons. The first attempt at a British hydrogen bomb had failed.126 They would get it right the next time, but a lot more tritium was required.

After Grapple I, the Windscale piles were operating in emergency mode at the highest possible power level using flammable metallic uranium fuel and flammable lithium-magnesium in piles of flammable graphite with gale-force air blowing through them. Fire was prevented by coverings of thin aluminum on the fuel and AM cartridges sitting in graphite bricks that could become superheated on their own at an unpredictable time for reasons that were not entirely understood. The annealing interval was increased to once every 40,000 megawatt days for the sake of more plutonium and tritium production. It is not unreasonable to predict an eventual problem under these conditions.

Sunday night, October 6, 1957, was in the middle of a local influenza epidemic, and Windscale Pile No. 1 was well overdue for an anneal. The front lower part of the graphite had not really released any energy at the last anneal in July 1957, and it probably had 80,000 megawatt days of Wigner energy buildup ready to let go at any time. Production was halted, the pile was cooled down, and the ninth anneal would begin Monday morning.

The temperature of the pile was monitored using 66 thermocouples placed at three depths in the reactor face in selected fuel channels. Considering that the core occupied 62,000 cubic feet, and a detailed map of the temperature throughout the graphite was necessary to monitor an anneal, having only 66 thermocouples was pitifully inadequate. There were also 13 uranium — temperature monitors in the control room and another seven on top of the pile in the crane room. The operations staff had performed these measurements before, and there was no concern about this weakness in the instrumentation. On October 7, the main blowers were turned off at 11:45 a. m., and an extremely slow and cautious approach to criticality in the lower part of the core was begun. Stopping twice to look at the temperature readings, it took the operators seven and a half hours to withdraw the controls and reach criticality. There was a holdup to work on some faulty thermocouple connectors. Once the pile was maintaining a low power level, the crew wrangled with some control rod positions to concentrate the fissions in the lower front of the core, where annealing was obviously needed. The goal was to bring this section in the core up to 250°C.

The facts that Windscale Pile No. 1 was able to achieve criticality and maintain it could give one with a religious bent the belief that God was on the side of the United Kingdom. Or, perhaps the Devil was. Driving it was like trying to steer the RMS Titanic around an iceberg. The core was so big, the peak of the neutron flux curve could be put just about anywhere in the massive block of graphite by artistic positioning of the controls, but it was ponderously slow to respond to control movements, and the instrumentation was a bit numb. The pile would not do anything quickly, and the dangers of a sudden runaway or an explosion were nonexistent.

An hour after the beginning of Tuesday, October 8, the pile seemed to be running cool, reading between 50° and 80°C in the graphite. One thermocouple indicated 210°C, and this was obviously where the annealing process had begun. An anneal would always start somewhere and then spread out slowly, hopefully infecting the entire pile. The operators ran in the controls to shut it down, letting it cook, and sat back to watch it happen. For some odd reason, two uranium thermocouples read 250°C. Uranium does not anneal; only graphite. Ian Robertson, the pile physicist on duty, had the flu, and he went home to collapse in bed at 2:00 am. The anneal seemed well in hand by the operating crew.

Robertson came back on duty at 9:00 the next morning, sick as a dog, to find that the temperature was not spreading the way it was supposed to, and the operators had decided to reheat the reactor by bringing it back to criticality. In a couple of hours they had it back running at low power, but something was not right. One uranium thermocouple showed a sudden temperature rise to 380°C. What’s that all about? This type of reactor was run by the graphite temperature and not necessarily by the neutron counts, and it was meandering all over the place, from 328° to 336°C. Pile No. 1 had its own quirks, but meandering was not one of them. Something was amiss, but the annealing had to proceed. The fission process was shut down again at 7:25 PM. Robertson was starting to get woozy, and the operating crew insisted that he go home.

By Wednesday morning, things seemed to have calmed down. The crew shut the inspection ports atop the core and turned on the shutdown fans to give it some air and bring the wayward temperatures down. At about midnight, the temperature readings off the graphite thermocouples started to go wild.

It was now early Thursday morning. One thermocouple in the middle of hole 20-53, 20 rows up from the bottom and 53 across, was reading extremely high at 400°C. Air dampers were opened. In 15 minutes the temperature rose to 412°C. It did not make sense. At 5:10 am. the dampers were opened again, and this time the smokestack radiation monitor indicated a bit of radioactivity in the filter. At about the same time, the stack on Windscale Pile No. 2, which was running plutonium production at balls-to-the-wall power, indicated increased radioactivity. Obviously a fuel cartridge had burst in No. 2. They really should do something about that.

Attempts to bring the annealing under control continued. Air dampers were opened and closed again, with no expected results. By 1:30 P. M., the stack radiation was unusually high, and it was clear that there was a problem. The uranium temperature was at 420°C and rising quickly. The Pile Manager, Ron Gausden, was called in. He gave instructions to open the dampers, turn on the shutdown fans, and try to bring down this temperature. Obviously, a fuel cartridge had broken open and fission products were collecting in the stack filter. The Christmas trees, which were parked off to the side at the back of the core, would not work with the pile at this elevated temperature, so they could not identify the broken cartridge. The temperatures were not going down, and at 2:30 P. M. Gausden told the operators to turn on the main blowers. He picked up the phone to call Tom Hughes and share the excitement.

The Windscale operation was critically understaffed, particularly for this running emergency to produce bomb material. Of the 784 professional posts, 52 were vacant. Hughes had worked at Windscale since 1951 as the Assistant Works Manager in charge of the chemical group. He was also Acting Works Manager for the entire site and had just been assigned a third post as Works Manager for the pile group. His response to the call from Gausden would mark his first visit to an actual pile.

Huw Howells, the Health Physics Manager, was already there to inquire about radiation coming out of the stack. With a short rundown of the situation in the control room, Hughes and Howells decided to call H. Gethin Davey, the Works General Manager with bad news about Pile No. 1. A crew from the control room rode the lift to the refueling platform and pressed the

UP button to take them to row 20 on the loading face and have a peek behind plug 53.127

The loading face was a bio-shield, built to protect workers who could stand there and push fuel into the graphite pile behind the shield with long poles. When not in use, each hole was plugged with a metal cylinder. A worker pulled out the plug in 20-53 and looked in the hole. Normally, it would take a flashlight to illumine the black-as-carbon fuel channels to see what was inside, but in this case a bright red glare greeted them. All five holes behind the plug were glowing.

The pile was on fire, and it had been burning since Tuesday. Windscale Pile No. 1, running too fast in the dark, had crashed into its iceberg.

Gausden ordered the crew to make a firebreak by removing all the fuel around the burning channels. Easier said than done. Even some fuel cartridges that were not on fire were so swollen from the high temperature, they would not budge. The men dressed out in rubber suits, full-mask respirators, gloves, and dosimeters to monitor their radiation exposures. It was going to be a long night. They started dumping fuel into the cooling pool in back of the core, pushing it out with the heavy rods. It was hot, difficult work, but the main blowers put positive air pressure behind the loading face, and clean, cool air blew out the loading holes and onto the men. The airflow was all that made the work possible.

The graphite on the front of the pile below where the men were ejecting fuel was now a mass of flames, and the highest temperature reading had passed 1,200°C. At 5:00 P. M. on Thursday,

Davey picked up his phone and rang his deputy, Tom Tuohy. “Come at once,” he said. “Pile No.

1 is on fire.”

Tuohy was at home caring for his wife and children, who were all down with the flu, and when he got off the phone he instructed them to please keep all the windows closed and not to leave the house.

Tom Tuohy, excitable, bubbly, and auburn-haired, was born at the eastern end of Hadrian’s Wall in northern England in a town named Wallsend in 1917. He studied chemistry at Reading University, worked for the Royal Ordnance Corps during the war, and had joined the nuclear effort in 1946. He arrived at the stricken pile in minutes and went straight to the loading face. He saw men struggling to punch the fuel out the back of the pile and got a grim impression of the situation. They were pulling back rods that were glowing yellow on the ends and dripping molten uranium. Back in Davey’s office he found a knot of scientists arguing over using carbon dioxide or argon to quench the fire. By 7:00 P. M. he decided to get a better look. He took the stairs to the crane room and lifted an inspection plate so he could see the front of the reactor. It was glowing. He went back at 8:00 P. M. and found flames shooting from the fuel channels, colored yellow by the sodium in the construction workers’ sweaty handprints on the graphite blocks. At 11:30 he pried up the viewing port, which was becoming quite warm, and saw blue flames hitting the concrete wall many feet behind the back of the pile, and a new fear gripped him. The flames were hot enough to ionize the nitrogen in the air. Not only could the hot flames burn through the concrete wall, but he was not certain about the floor under him staying put much longer.

Early on Friday, October 11, Davey was sent home sick and in pain with the flu. Between 4:00 and 5:00 am., the largest tank of carbon dioxide that could be found was expended into the fire, with zero effect. There was nothing to do but start pumping water into the fuel channels, a desperate move. The concept of flooding a graphite reactor with water was so remote, there were no fire-hose taps in the building. The works fire brigade was called in with pumper trucks, and nozzles were jury-rigged to force water through the holes in the loading face and deep into the fuel channels, two feet above the highest point of the fire. The water was turned on just before 9:00 am. K. B. Ross, the Director of Operations, dispatched the following message to the Authority Chairman, Sir Edwin Plowden, in London:

Windscale Pile No. 1 found to be on fire in the middle of lattice at 4:30 pm yesterday during Wigner release. Position been

held all night but fire still fierce. Emission has not been very serious and hope continue to hold this. Are now injecting water

above fire and are watching results. Do not require help at present.

Plowden dashed off a note to the Minister of Agriculture, wisely anticipating trouble with radiation contamination of the dairy farms in the area.

Tuohy was relieved when there was no explosion from the water interacting with the graphite. Watching through the viewing port at the back end of the pile, he could see the water gushing out of the fuel channels and cascading down the pile into the cooling pool at the bottom. The water looked good tumbling down, but still the fire raged out of control. The back of the core remained a wall of flames. He watched for an hour, starting to feel that the situation was hopeless, when he was struck by a brilliant idea. All the men had evacuated the loading face. There was no longer any need for the blowers. He decided to turn them off.

Almost instantly, the flames died away.

This time when Tuohy went up to the crane room to look, the viewing port seemed firmly cemented to the floor. The fire in its dying gasp was sucking oxygen out of the remaining air and causing a vacuum in the reactor core. With no more air forced through the fuel channels, there was no more fire. By noon Tuohy was able to report to Davey that the fire was out and the situation was now under control. Just to make certain of his pronouncement, the water was kept flowing for another 30 hours.

The core of Windscale Pile No. 1 was a total loss. Over 10 tons of uranium were melted and five tons were burned. Very little of the uranium or even the fission products went up the chimney. A brittle oxide crust had formed in the extreme heat of the fire, and the heavy oxides were bogged down in it before they made it to the air outlet. The immediate concern was the volatile fission product, iodine-131. The filter packs, which were no longer called “Cockcroft’s follies,” were not expected to capture any of the 70,000 curies of iodine-131 that were present in the fuel when the fire began, but there was a fortuitous happening. The LM cartridges, containing bismuth oxide meant to activate into polonium-210, burned up, and the light bismuth oxide dust went up the stack and caught in the filters. This and some vaporized lead from the weights in the AM cartridges reacted chemically with the free iodine and captured some of it in the filters. Although 20,000 curies of iodine-131 blew out the top of the stack and over the dairy farms, about 30,000 curies of it were caught in the filters. It was better than no capture at all.128

The immediate bad thing about loose iodine-131 is that it falls on the grass, cows eat it, it winds up concentrated in the milk, people drink it, it goes straight to the thyroid gland, and the tightly contained radiation load has a good chance of causing thyroid cancer. The good thing is that it has a short half-life of only eight days. On Sunday night, October 6, the reactor was shut down, iodine-131 production by fission stopped, and the countdown for the decay of the iodine — 131 began. By eight days later, half of it was gone. On Saturday it was estimated that 20,000 curies of it were contaminating 200 square miles of territory north of the reactor, but in about 80 days that contamination would drop to 1/1,000 of that level.

However, 20,000 curies divided by 1,000 is 20 curies, and that is still a great deal of radiation. It is 7.4 3 1011 becquerels, or 7.4 3 1011 iodine-131 disintegrations per second, emitting first a 606 kev beta ray and then a 364 kev gamma ray, becoming a stable xenon isotope. The dairy industry in Cumbria was thus in serious trouble. On Saturday morning there was enough active iodine-131 on the grass, 132,000 disintegrations per second per square foot, to rattle a Geiger counter in a most alarming way.

This was new, untrod territory in the nuclear business, in which a private industry would have to be shut down because of an unfortunate situation in the government-owned, secret, dangerously handled fissile-isotope-production endeavor. There were no safety standards; no maximum limit for the amount of radiation to which a toddler should be subjected in its otherwise wholesome cow’s milk. The government did the right thing and bought every pint of contaminated milk. It was poured away into ditches, and the countryside smelled of sour milk

for quite a while.129 After a year, not a trace of iodine-131 could be found in the farmland. One good thing about radiation contamination is that it improves with age.

Neither Windscale reactor would ever be started up again, and there would be no more open — looped, air-cooled reactors built anywhere in the world. Pile No. 2, which was in perfect operating condition, was shut down permanently five days after the fire was stopped, and as much remaining fuel as could be moved was carefully taken out of the wrecked Pile No. 1 and processed to remove the plutonium. Unusable radioactive debris was dumped offshore into the Irish Sea. The cores of both reactors were sealed off with concrete, and the buildings were used for several decades as offices, labs, workshops, and for bulk storage. The 6,700 damaged fuel cartridges and 1,700 AM and LM cartridges in Pile No. 1 will be removed by remote-controlled robots by 2037. The core is still a bit warm. The name Windscale, carrying bad karma, was buried and the site was renamed Sellafield. It is now owned by the Nuclear Decommissioning Authority (NDA).

The people who worked at Windscale in 1957 and who participated in the cleanup operations have been studied, looking for radiation-caused diseases. Statistical analysis indicates that the widespread radiation release should have caused 240 thyroid cancers, but no correlation has been found. The last accounting in 2010 could find no evidence of health effects from the radiation release back in 1957. Tom Tuohy, who stood alone in the most hazardous conditions of radiation exposure at the height of the Windscale fire, died in his sleep on March 12, 2008,

at the advanced age of 90 years.130

Bill Penney, the man whose relentless demands for more tritium, plutonium, and polonium-210 had caused Pile No. 1 to be overworked to the point that it burned down, was assigned as the chairman of the inquiry committee. On October 26, 1957, 16 days after the fire was put out, he submitted his report to the Chairman of the United Kingdom Atomic Energy Authority. His committee found the operating staff at fault for causing the fire. During the annealing process, they had reapplied nuclear heating to the reactor too soon after the first try. He did not point out that the fire had started in hole 20-53 when the overheated lithium in a Mark III AM cartridge diffused through the aluminum and set fire to the adjoining fuel, and he assigned no responsibility to himself or to the questionable engineering of the isotope production

cartridges.131 In retrospect, the Windscale piles were a disaster waiting to happen. Panic — containment photos were released showing contented cows grazing in the grass with the Windscale chimneys looming in the background.

The secrecy covering the Windscale site and its mission did not help the publicity crisis that arose when it hit the newspapers in London and Manchester. Simply cautioning people about drinking milk or leaving windows open was enough to cause some concern. At one leak point a scientist at Windscale, Dr. Frank Leslie, wrote a letter to the Manchester Guardian on October 15, expressing disappointment that the government had given no warning to the public until the matter was resolved. Harold Macmillan, the excitable Prime Minister, had to be restrained from seeking out Dr. Leslie and strangling him manually. The Penney report was finally declassified and released to the public in January 1988.

On November 8, 1957, about a month after the Windscale fire, the British bomb program achieved what it had so dearly sought. Above the southern end of Christmas Island in the Pacific Ocean, the two-stage thermonuclear device Grapple X went off with a bang, yielding 1.8 megatons. Penney’s development crew had done it almost correctly, and a bomb that was built to give one megaton unexpectedly wiped out the military installations on the other end of the island with 80% over yield. A triumphant British delegation of scientists was invited to Washington to talk about thermonuclear topics with some fellows from the Lawrence Livermore

Lab, and the shutout was broken. From that point on, the United Kingdom was granted technical parity with the United States in matters of nuclear weapons and use of the Nevada Test Site.

The replacement plutonium production reactors for the Windscale units were already up and running, as of August 27, 1956, at the Windscale site. Four large graphite reactors using closed-loop cooling by carbon dioxide, named Calder Hall Piles 1 through 4, produced 60 megawatts of electricity each, and were considered to be the world’s first nuclear reactors making significant commercial power. In reality, the purpose of these reactors was to convert uranium-238 into plutonium-239 and to manufacture tritium. Calder Hall Pile No. 1 ran for nearly 47 years before it was finally shut down in 2003.

A sister plant named Chapelcross was built on an abandoned airfield in southwest Scotland near the town of Annan. The plant, comprising four 180-megawatt Calder Hall reactors, was completed in 1959. Its purpose was to produce plutonium and tritium, with 184 megawatts of electricity on the grid being a secondary byproduct. The Calder Hall and Chapelcross reactors were safer and more complex than the antique Windscale units. The carbon dioxide cooling gas worked just like air being blown through, but it was contained in a closed loop, pumped back into the bottom of the core after the heated gas had been used to make steam in heat exchangers. The steam, which was used to turn the turbo-generators, was also in a closed loop, and the ultimate heat sink for disposing of the waste energy was one large cooling tower per reactor, dumping heat into the atmosphere. There was not much worry of fire in a graphite pile cooled with fire-suppressing carbon dioxide. Even an unlikely steam explosion would not release fission products into Scotland.

For efficient plutonium production, the fuel was still metallic uranium, this time enclosed in cans made of magnesium oxide. It was code-named MAGNOX, and this became the type designation for a series of 26 power reactors built in the UK. Magnesium oxide is perfectly fine as a canning material, as long as it does not get too hot or too wet. If left too long in a cooling pond, the magnesium oxide corrodes and leaks, and the fuel inside can melt easily if deprived of coolant while fissioning.

Given the Cold War pressures of producing Poseidon and Trident missile warheads and the risky fuel design, these improved graphite reactors were remarkably safe. There were no meltdowns or fires of the Windscale severity, but there were some interesting incidents.

The British MAGNOX reactors used graphite neutron moderators and a fast-flowing gas for cooling. This design was different from the Windscale reactors in that the primary cooling system was closed, using the same gas over and over as it was recycled back into the reactor alter it had given up its heat to a steam generator. In this design, the gas was carbon dioxide or helium, and with the closed system the graphite would never be exposed to oxygen and would be unlikely to burst into flame.

The Chapelcross piles were just like the Calder Hall piles, only different. They were built in series, starting with Pile No. 1, and improvements were added as the construction progressed. Pile No. 1 required annealing, similar to the Windscale piles, but, starting with Pile No. 2, the graphite fuel channels were lined with graphite sleeves. The sleeves were fragile and were something else that could break, but they were designed to let the graphite run so hot it would never require annealing. In Chapelcross Pile No. 2 on May 19, 1967, after seven years of running at full power, the graphite sleeve inside one of 1,696 fuel channels crumbled and blocked the flow of carbon dioxide coolant over the fuel canisters. At least one fuel canister overheated, the uranium melted and caught fire, breaking open the can and sending radiation

alarms into a tizzy.132 Considering that a MAGNOX reactor is loaded with more than 9,000 fuel canisters at one time, this would seem a small statistical problem, but full-blown disasters can start small and memories of the Windscale fire were still fresh. The reactor was scrammed immediately, and the accident investigation began.

Unlike the Windscale piles, the more advanced gas-cooled reactors were built with the fuel channels cut vertically, and fuel handling was semi-automated to prevent workers from having to get anywhere near the reactor cores. The entire core was encased both in a steel pseudo­sphere as protection from fission product leakage and a pressure vessel, containing the cooling gas and keeping broken fuel cartridges off the landscape. This was an excellent plan, but peeking into a fuel channel was not as easy as it was in the old days. A special television camera was built, mounted on the end of a pole that could be positioned over the burned fuel channel to look in and see what had happened. This device confirmed that the fuel channel was blocked with graphite debris and that it would have to be cleaned of this and the remains of the burned fuel, but unfortunately the camera broke off and fell into the reactor. It did everything but scream as it tumbled off into the abyss, with the monitor screen image spinning and then going black. This would complicate the repair.

It took two years, but the men at Pile No. 2 were able to design a workable plan for restoring the plant to full operation. Three men were outfitted in fully sealed radiation suits with closed respirators. Each man was given only three minutes to work, during which he would receive his entire year’s allowed radiation dose working at the top end of the core in a concentrated radiation field. One at a time, they moved quickly through the forest of control rods to the clogged fuel passage and ran a scrubber on a long pole down the hole, cleaning the passage and restoring its roundness.

The cleanout was successful, and Chapelcross Pile No. 2 resumed operation. All was good until 2001, when the Chapelcross power plants seemed to trip over a streak of bad luck.

Fuel has to be changed-out at the MAGNOX reactors at least twice a year. First, the burned fuel, blisteringly radioactive with fission products, must be pulled out of the fuel channels and lowered down a chute and into a lead coffin. This is accomplished using the discharge machine, which runs on rails on the floor of the crane room, addressing holes that are opened one at a time, giving access to the reactor below. An operator rides in a seat on the back of the machine, which weighs a hefty 60 tons. Half of that weight is lead shielding to protect the operator from what he is pulling out of the reactor, and if the machine is operating properly, the workers never see or touch the fuel cartridge.

The operator positions the discharge machine over a hole in the floor, grabs a fuel cartridge down in the reactor, and pulls it up into the shield. The machine then rolls on rails to the end of the room, where the well hoist grabs the cartridge away from the discharge machine and lowers it on a cable down five floors, through the concrete-shielded discharge well. It drops into a lead barrel, which then rolls out on rails to the transit hoist for a trip to Windscale for fuel reprocessing. After you have discharged a few hundred thousand fuel cartridges, it seems routine and foolproof; but one day early in 2001, one fuel cartridge out of 10,176 had a problem.

The operator sent the cartridge down the discharge well and into the lead barrel. For some reason it did not release, and the cable came back up, ready to snag another cartridge after it had been snaked out of the core. Instead of an empty grabber, up came a live cartridge, broadcasting gamma radiation all over the refueling floor. Alarms jangled everyone’s nerves as they leaped from the chairs on their discharge machines and hot-footed for the door. Nobody was injured by the radiation, but it was considered a serious accident, and inadequate design, improper operation of the discharge machine, and statistical probability were blamed. All refueling of the early MAGNOX reactors at Chapelcross and Calder Hall was halted while the incident was investigated.

In July 2001, the workers at Chapelcross discovered that steel drums filled with depleted uranium trioxide tend to rust and develop holes when they are left out in the rain for several years. It was decided to substitute stainless steel barrels.

Later in July, corrections to the problem experienced earlier that year, when a fuel cartridge grabber would not let go, seemed to cause the opposite problem. After hearing something heavy crash into the door at the bottom of the discharge well, investigators sent a remote — controlled TV camera into the area and had a look. Twelve fuel cartridges had let go of the grabber and fallen over 80 feet into the transport barrel, splattering the irradiated uranium over the discharge bay. A careful cleanup was accomplished.

In August it was time for the annual maintenance and cleanup at Chapelcross, starting with Pile No. 1. There was a disturbing finding. It was known that graphite could “grow” in just about any direction under neutron bombardment at temperatures lower than 300°C, but in Pile No. 1 the graphite had shrunken. The pile was now not quite as tall as it had been, and the steel charging pans, designed to guide new cartridges into the core when refueling, were now hanging in space, supported perilously by the nozzles on the burst-can-detection gear. The other piles were found to have similar defects, but not as bad as Pile No. 1, which was built differently.

Only Piles 2 and 3 were in decent enough shape to be restarted. In June 2004, the entire power station was shut down for good. The sister plant, Calder Hall at Sellafield, had been shut down permanently in 2003. The British graphite reactors had made a good run of it, but they were now obsolete and it was time to call it quits. By 2004, there was no longer a need to manufacture plutonium, and better ways to build a power reactor had been developed. On May 20, 2007, at 9:00 am., the four 300-foot hyperboloid cooling towers, visible on a clear day from a distance of 50 miles, were brought down in 10 seconds by demolition explosives, and that was that.

The fuel-reprocessing industry in the UK has reported only one criticality accident in which fissile material managed to come together accidentally in a supercritical configuration. Just about every other country that has tried to separate plutonium from uranium in spent reactor fuel has experienced at least one such excursion, and this was Britain’s. This incident at the Windscale Works on August 24, 1970, is described by the criticality review committee at Los Alamos as “one of the most interesting and complex because of the intricate configurations involved.” An entire book could be written to describe this accident, but I will be brief.

It is the goal of every chemical engineer working on a reprocessing plant design to allow no vessel large enough or of an optimizing shape, such as a sphere or tomato can, to exist in the complicated pipe-works of a reprocessing plant. Occasionally, however, when there is no conceivable way that fissile material, such as plutonium, can collect there, a round tank finds its way into the layout. At Windscale, plutonium was recovered from spent MAGNOX fuel, and near the end of the process it was refined in 300-gram batches. The plutonium was dissolved in a mixture of tributyl phosphate and kerosene and fed to a conditioner vessel, where the amount of plutonium in solution was adjusted to between 6 and 7 grams per liter. This was safely less than the concentration required for criticality.

From there, the small batch was lifted through a pipe to a transfer vessel by vacuum, where it would be fed through a U-shaped trap to a refining operation called the pulsed column. The transfer vessel was a short, cylindrical tank having hemispherical top and bottom. It was a near-perfect size and shape to house an impromptu reactor, but surely no such concentration of fissile material could be fed to it from the conditioner in one gulp, and the trap prevented any backflow into it. It was a mistake to think this.

It turned out that after every transfer of a subcritical amount of plutonium to the transfer vessel, a small amount of plutonium was stripped out of the solution by water sitting in the bottom of the tank. Ordinarily, that would be no problem, because the concentration of plutonium in the tank would never be greater than 7 grams per liter of solvent, but the amount of plutonium dissolved in the water grew gradually. This went on for two years, until the bottom of the tank held a whopping 2.15 kilograms of fissile plutonium-239.

On the last batch through the system, 30 grams of plutonium were dumped in on top of the water, mixing the solvent and water together and causing a supercritical nuclear reactor to suddenly exist in the plumbing for 10 seconds.

It was not a fatal accident. Nobody was injured, and the intricate piping in the plant looked exactly the same before and after the supercriticality, but the fact that it happened in such a carefully designed process was unnerving. It goes down in history as proof of how difficult it is to predict what will happen in a maze of pipes, valves, tanks, and traps carrying a fluid for which its volume and shape are important. The concept of impossibility becomes murky.

Windscale became Sellafield, and the THORP, or the Thermal Oxide Reprocessing Plant, became operational in 1997. It took 19 years to build the facility at the place formerly known as Windscale. Its mission is to take used reactor fuel from Britain, Germany, and Japan and separate it into 96% uranium, 1% plutonium, and 3% radioactive waste, using a modified PUREX process.

In July 2004, a pipe broke and started filling the basement with highly radioactive, pre­processed fuel dissolved in nitric acid. The loss of inventory after nine months had climbed to 18,250 gallons. This went unnoticed until staff reported the discrepancy between solution going out of one tank and not arriving in another tank.

As it turned out, the liquid flow was monitored by weighing it periodically in an “accountancy tank.” This tank had to be free to move up and down as it accumulated the heavy uranium — plutonium waste in dissolved form, and the extent of sag as it filled was translated into weight. As the tank was being installed, it was decided to leave off the restraints that would keep it from wagging side to side as it accumulated liquid. This move, thought to protect it in case of earthquake, proved to be too much for the pipe connecting it to another process downstream, and it broke under the floor where it could not be seen.

On April 19, 2005, a remote TV camera was sent down to see what was going on, and it confirmed that the radioactive soup had formed a lake in the secondary containment under the Feed Clarification Cell. The spill was nicely contained in the stainless steel liner of the containment structure, but it contained 44,092 pounds of uranium, 353 pounds of plutonium, and 1,378 pounds of fission products. It was the fission products that made it a problem, as no human being would ever be able to enter the room and repair the broken pipe, even when the solution was removed using existing steam ejectors. The only possibility is to repair the break using a robot, but building a mechanical plumber is proving to be difficult. THORP will possibly complete its existing reprocessing contracts, bypassing the accountancy tank, and close down in 2018.

The history of atomic accidents in Britain is thus a story of ambition, impatience, originality, and accomplishment under hard circumstances, marked by a spectacular incident the year that David Lean filmed The Bridge on the River Kwai. If you find yourself cornered by a force of Brits who rib you mercilessly about the SL-1 explosion, it is correct to remind them of the British Blue Peacock nuclear weapon, in which the batteries were kept warm by two chickens living in

the electronics module aft of the warhead. It is an effective diversion, and it is almost true.133

114I am not sure what “PCE” means. It was possibly a typographical error in the original memo, meant to be “PEC,” or Production Executive Committee.

115See the film at http://dvice. com/archives/2012/07/this-is-what-st. php.

116Two of the men, Luttrell and Yoshitake, are still alive, although all six participants eventually suffered from cancer. It is doubtful that any disease was caused by standing under Shot John. It was only a short pulse of radiation that hit them, and not the chronic exposure that can cause cancer. They as well as the majority of soldiers in the armed forces, smoked tobacco, and this dangerous habit typically overwhelms any signal of radiation-induced cancer in the thousands of nuclear test participants. The study of cancer in Cold War veterans continues.

117Superman finds that his few seconds in front of the reactor face have infused him with radiation, and he must exile himself to prevent harm to anyone around him. It has been over 55 years since I saw that episode, but I also remember the radiation making noise and electrical sparks, all of which is wrong. However, episode 69, “Peril,” has Perry White, the editor of the Daily Planet, exercising his inner scientist by engaging in astonishingly prescient nuclear research. Perry is working on a process that extracts uranium from seawater, named “formula U183.” A large percentage of the Earth’s available uranium is dissolved in the ocean, and Japanese scientists are currently working on a system to extract it for use in power reactors. I have been advised of their secret uranium-extraction filter material, but there is not room in this footnote to discuss it.

118An updated replica of the X-10 was built at the Brookhaven National Laboratory in 1948, and it was in constant use for research until final shutdown in 1968. The Brookhaven Graphite Research Reactor was not a military secret, and newsreels showing workers pushing fuel rods or experiment samples into the holes on its front can be difficult to distinguish from similar films made at X-10. I think that the power-scram point on the X-10 was set for 1.8 megawatts.

119All was not lost. Some leeway was granted quietly in 1948 by an agreement called the “Modus Vivendi.” It allowed American scientists to tell their British colleagues that they were perhaps going in the wrong direction in their bomb-production development, but not exactly how.

120GLEEP was initially thought to be the first working reactor in the Eastern Hemisphere, but the Soviets had beaten them to it. The F-1, which was an excellent copy of the Hanford 305 plutonium production reactor, first started up at 6:00 P. M. local time on Christmas Day 1946. The Soviet espionage network, which was second to none, obtained the plans for this top secret system at the Hanford Works, and this was a short-cut to production without a lot of rediscovery and experimental development as was necessary in the UK.

121No published plan diagram of the Windscale reactors shows the blowers. That is because the blowers were located in two separate buildings per reactor, one left and one right, connected by large concrete tunnels. The Windscale reactors are still there and can be seen on Google Earth. Windscale Unit 1 is at latitude 54.423796°, longitude -3.496658°. The stack on Unit 1 has been torn down and the base is filled with concrete. Unit 2, to the left of Unit 1, looks complete, but the west-side blower building has been torn down and made into a parking lot.

122The Canadians did indeed supply plutonium for the time-critical atomic bomb project, but unlike the Windscale reactors, the NRX reactor at Chalk River was not designed specifically to make Pu-239. The Windscale pile operations would purposefully run the fuel through very quickly whereas NRX would use the fuel to useful depletion. As a result, the fissile material for the bomb contained a lot of Pu-240, which fissions spontaneously and threatens to melt the bomb core before it can explode. The Brits solved this problem by using a “levitated pit,” in which the bomb core was suspended in the middle of a hollow sphere of high explosive, removing it from close contact with any neutron-reflecting material. It seemed a brilliant innovation, but the Americans had been using this design feature since 1948 in the MK-4 A-bomb, tested in Operation Sandstone.

123Inside nuclear engineering, Dr. Teller is considered to be the mother of the H-bomb and not the father because he “took it to full term.”

124The operating power of a Windscale reactor has never been published, but near as I can tell it was 90 days between anneal no. 8 and anneal no. 9 on Pile No. 1. The plutonium/tritium production was so pressed at this time, it was decided to go 40,000 megawatt days between anneals for no. 9. Assuming that Pile No. 1 ran 24/7, a power rating of over 400 megawatts can be calculated. That is a lot of power for an air-cooled reactor.

125The piles were also loaded with LM cartridges. These special canisters were used to produce polonium-210 from neutron capture in bismuth oxide for use in A-bomb triggers. The LM cans were not considered flammable.

126I am told that Short Granite was a full-scale two-stage hydrogen bomb weighing 4,550 kilograms, and the active fusion component had to be the light solid, lithium deuteride. So what was all the furious tritium production for if not a liquid tritium-deuterium bomb? A tritium-based two-stage thermonuclear weapon, such as the American EC-16, would weigh about 32,000 kilograms, which would have nailed the Vickers Valiant bomber to the ground. As it turns out, the tritium production in the Windscale piles was not for the Short Granite bomb. It was used in the electrically driven neutron generator, or “initiator,” used in the A-bomb “Orange Herald,” tested over Malden Island on May 31, 1957. Short Granite used a beryllium — polonium solid-state initiator, made using the polonium-210 produced in the Windscale piles in the LM cartridges. The accelerated production at Windscale was to make bomb-trigger components.

127An interesting bit of trivia from B. J. Marsden of the Nuclear Graphite Research Group at the University of Manchester: the refueling platforms at the Windscale reactors, called “charging hoists,” were airplane elevators salvaged from WWII aircraft carriers.

128There was also a great deal of radioactive xenon-133 gas released at Windscale, 16 times more than the iodine-131. This sounds terrible to the general public, but xenon-133 has zero body burden and it cannot react chemically with anything, unlike iodine-131. Animal body chemistry has no use for xenon. The xenon-133 floats away and decays to stable cadmium with a half-life of 5.24 days. There is no xenon filter, and radioactive xenon escapes regularly from every nuclear power plant in the world.

129There are also reports that the milk was diluted with water and then dumped into the Irish Sea. It seems a bit odd to dilute it with water before pouring it into the ocean, and the aroma of decomposing milk was mentioned in local newspapers. It’s possible that farmers who were not found to have contaminated milk disposed of it anyway on their own initiatives, but more likely they took advantage of the inflated milk prices and sold it.

130See an interesting British documentary on the Windscale fire from 2007 at http://www. youtube. com/watch? v=ElotW9oKv1s&feature=relmfu. Some important technical details are garbled, and the recreated scenes of men working at the loading face are seriously wrong.

131The actual cause of the Windscale fire remains a controversial and unresolved topic. It is probable that it was started in an isotope channel by one of the many AM cartridges, which were the most temperature-sensitive components in the entire pile. There was one isotope channel for every four fuel channels, and when you opened an access plug, the isotope channel was in the center, with four fuel channels surrounding it. The first man to open plug 20-53 reported that “it was glowing bright red, and so were the four channels around it.” It is often assumed that the center hole was a fuel channel, but clearly he was referring to the isotope channel behind 20-53.

132Quoting the OSHA Occupational Safety and Health Guidelines for Uranium and Insoluble Compounds, under Reactivity: “Contact of uranium with carbon dioxide causes fires and explosions.” The carbon dioxide coolant probably protected against graphite fires, but it was dangerous in contact with metallic uranium. Ironically, the suggested method for putting out a uranium fire is to smother it with graphite chips.

133Although the use of live chickens, installed with a one-week supply of food and water, as a heat source was a serious proposal for the Blue Peacock

(originally Blue Bunny) in October 1954, accounts of its implementation are difficult to find. Unfortunately this specification was declassified on April 1, 2004, and it was immediately assumed to be an April fool’s joke. Tom O’Leary head of Education and Interpretation at the National Archives, responded with: “The civil service does not do jokes.”

Chapter 6