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.
118
An 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.
119
All 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.
120
GLEEP 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.