Windscale 1957

The Nuclear Winter

Narrator It was Colonel Paul Tibbetts who took war forward into the nuclear age when he dropped a single atomic bomb known as Little Boy on the Japanese city of Hiroshima on August 6th 1945 from a B-29 bomber called the Enola Gay. 130,000 people were killed, and of the city’s 76,000 buildings all but 6,000 were destroyed. Three days later a second device was exploded over Nagasaki and Japan surrendered.
David Holloway Prof David Holloway The use of the bomb to destroy Hiroshima and Nagasaki was the most powerful imaginable demonstration of the destructive force of the bomb.
Narrator The terrible capability of nuclear weapons had been shown for the first time, and there began a scramble by the world’s most powerful nations to develop their own bomb. One of those was Britain, and a secret plant was built at Windscale, a remote spot on the north west coast of England, to manufacture Plutonium, the man-made element which gives atomic weapons their terrifying power. But the British reactors, designed and built for the purpose, had one major flaw, and within seven years of the start of production would become the site of the world’s first nuclear accident.
Prof John Bayliss, University of Wales, Aberystwyth Windscale was an accident that was waiting to happen.
Narrator It was here at Los Alamos in the New Mexico Desert that the Manhattan Project, the wartime work to build a nuclear weapon, was carried out in utmost secrecy. It was led by Major-General Leslie Groves, a US army engineer. The Chief Scientist was J Robert Oppenheimer. The idea that nuclear fission could be used in the creation of the most powerful weapon the world had seen was first put forward in the late thirties. In Britain, the Maud Committee was set up to investigate the possibilities and reported in 1941. But it was the United States which undertook to build the first atomic bomb, a task it completed in less than three years. That it was able to achieve its aims in such a short space of time was a testament to the country’s determination, scientific abilities and industrial muscle. Three new towns were built. Los Alamos was where the scientific team was based and where testing was carried out, while production of fissile material took place at Oak Ridge, Tennessee and at Hanford in the Pacific North West. The Hanford Reactors were designed around a graphite core cooled by water drawn from the Columbia River. Such was the concern over the potential for a nuclear accident that a 25 mile four lane highway was built to allow the swift evacuation of workers. Scientists knew that, if the water supply failed, it would be impossible to shut down the reactors before a nuclear explosion. But the pressure to manufacture Plutonium was so high that the risk was judged to be acceptable.When the land upon which Hanford would be built was acquired, 1200 people lived within its 625 square miles. Construction was a massive undertaking, but the speed of progress allowed the first fissile material from Hanford to be delivered to Los Alamos in the Spring of 1945. It was eagerly awaited by the scientists and preparations were made for the world’s first nuclear explosion - code-named Trinity. The device was raised to the top of a 110 foot high metal tower and tested in the early hours of July 16th 1945. To the delight of Oppenheimer and Groves it was successful, producing a blast equivalent to 20,000 tonnes of TNT.
David Holloway Prof David Holloway, Stanford University It was very important for the US Government that the bomb project should be successful, for changing reasons. Initially because they were afraid Germany might get a bomb first, so early on it was a factor in thinking about the war with Germany. Then, secondly, when Germany was defeated and the bomb still wasn’t quite ready, but nearly ready, of course the whole focus was on the war with Japan. And there its importance was that it would help to bring the war to an end quickly.
Narrator When a second bomb was dropped on Nagasaki three days after the Hiroshima explosion, Japan immediately surrendered. The destructive power of this new weapon shocked the world, but served also to convince politicians that membership of the nuclear club would bring with it a world status few countries could hope to achieve. Britain had been very much the junior partner in the Manhattan Project, though its scientists had had access to some of the pool of American knowledge. The Soviet Union was aware of what had been going on at Los Alamos through a British spy Klaus Fuchs, though at diplomatic level there was no more than the merest hint of the kind of weapon the United States planned to deploy.
David Holloway Prof David Holloway, Stanford University The only thing that was done was that, at the Potsdam meeting in July of 1945 after the bomb had been successfully tested in Alamogordo Truman went up to Stalin after one of the formal sessions and remarked to him "we have a bomb of unusual power". And Stalin apparently said nothing - just nodded his head, maybe said thank you - but in any event went back and talked to his people, and it was clear he understood that what Truman had in mind was the Atomic Bomb, because the Soviet Union had very good intelligence about the Manhattan Project.
Narrator Post-war Britain was in a much weaker state than had been the case prior to 1939, though it took two decades before the country began to come to terms with its new world position. It seemed entirely natural to pursue a nuclear policy, so scientists were set to work creating an independent nuclear weapon - a deterrent in the cold war with the Soviets. The project had nothing like the money and resources available to the Americans, so an early decision had to be taken over which fissile material would form the heart of the British weapon. The Manhattan Project had hedged its bets by creating two production sites, each of which made a different core element. The task of Oak Ridge was to manufacture Uranium-235, whilst Hanford created Plutonium in its water-cooled graphite reactors. Neither technique was particularly easy, but there were advantages in following the Plutonium route, and at first the British Government set about looking for a site to house two water cooled reactors along the lines of those at Hanford. The Americans had realised very early on that such a design carried inherent risks. If the coolant system failed, the pile would quickly become an atomic bomb, so their plant had been sited on a loop of the Columbia River to give easy access to the 25,000 gallons of water a minute needed to keep each reactor cool. But Hanford covered over 600 square miles, and there was nowhere in Britain suitable which met all of the requirements for such a design. So instead the engineer in charge of production, Christopher Hinton, felt the only feasible solution was to build reactors cooled by air.
Lorna Arnold Lorna Arnold, Atomic Energy Authority Archivist Christopher Hinton was extremely resistant to the idea that he should build water-cooled reactors in England because he knew that the reactors at Hanford were far from safe and that they had deliberately been built in a very, very remote site and there was no site in Britain sufficiently remote to have a water-cooled reactor sited there.
Narrator So the decision was made to opt for air cooling, a system previously rejected by the Americans. The enhanced safety offered meant that a site much closer to inhabited areas could be used, and eventually a former Royal Ordinance Factory on the Cumbrian coast was chosen. But British scientists were at a disadvantage. Although they had been given access to many of the Manhattan Project’s secrets, they hadn’t been allowed near the Plutonium producing site at Hanford, and their knowledge of the process was sketchy. Furthermore, the McMahon Act of 1946, forbade American scientists from sharing nuclear secrets with any foreign national. But as time went on there were informal meetings between British and American nuclear physicists, notably one in 1949 involving Edward Teller. He had worked with Enrico Fermi on the first ever nuclear pile at the University of Chicago. Teller, who later went on to mastermind the Hydrogen Bomb, met with scientists from the Atomic Energy Authority at its Harwell headquarters.
Lorna Arnod Lorna Arnold, Atomic Energy Authority Archivist There was a visit from two or three American scientists - Teller and Wigner - and Wigner who was a very distinguished Hungarian refugee scientist in the USA, and who was obviously the discoverer of Wigner Energy - he said that he thought there was a danger of a fire in one of the British reactors because he said that, as a result of irradiation, you will get energy slowly building up in the graphite, and then, unless you can find a way to release it, you are going to have an explosive situation.
Narrator But although the British scientists listened to the warnings from Teller and Wigner they failed to pass them on to their colleagues at Risley responsible for design and construction of the Windscale Piles. The energy state discovered by Wigner, and pointed out to the British in 1949, would prove to be the cause of a fire in the number one reactor eight years later when the graphite moderator collected a potential energy from the irradiation process. Wigner’s prophetic warning suggested that the release of this energy, unless properly controlled, could lead to just such a conflagration.
Edward Teller Dr Edward Teller, Hoover Institution on War Peace & Revolution Fission produces fast neutrons. The neutrons produce fission, but in the reactor they do it not in their original fast state, but after they have been slowed down by many collisions with nuclei. These collisions with nuclei displace these nuclei, and in a graphite reactor, for instance, quite a number of the displaced Carbon nuclei remain stuck in a state different from their equilibrium state. If then, at a later time, the whole reactor is heated to a somewhat higher temperature, then the nuclei from the somewhat higher energy position move back into their original lower position and in doing so release the energy that they have contained. This in turn gives rise to an increase in temperature which of course accelerates the process that I have already described. And so, Wigner said, reactors run at a relatively low temperature, if the temperature’s increased, may undergo a process of instability, and this possibility should be taken into account in the design of the reactor.
Narrator Within a few months of the conversation about Wigner energy, a visit to the Oak Ridge plant in Tennessee by the Director of the Atomic Energy Authority Lord Cockcroft led to a decision which would have a far-reaching effect a decade later. During his trip a release of radioactivity was found within the site which was believed to have come from the chimneys of the Clinton Reactor, a prototype air-cooled pile similar to the design opted for by the British at Windscale. The release worried Cockcroft, even though American scientists had already rejected a need for any filtration of the cooling air after it passed through their reactor. On his return to Britain he insisted that the Windscale chimneys be fitted with filters to catch any radioactive particles and prevent their escape to the surrounding countryside. It was a major engineering headache. By this time construction work was well advanced, and the only place the filters could now be placed was in hurriedly designed galleries at the top of the 400 foot chimneys. Cockcroft’s insistence caused much friction.
Lorna Arnold Lorna Arnold, Atomic Energy Authority Archivist Construction was very difficult - building the filter galleries that high up - hauling that amount of material up and doing the construction at that height. And then of course maintaining the filters was very difficult because the big filter pads in the frames had to be regularly changed. Very often they were done in a howling gale above cloud level, and it was a horrendous job.
Narrator The first pile went critical towards the end of 1950 with the second following eight months later. But by now the pressure on the Atomic Energy Authority to begin the production of Plutonium was intense. Britain was being left behind in the arms race, and the timetable for the development of an Atomic Bomb laid down in the Overall Strategic Plan of May 1947 had been overtaken by world events.
Paul Rogers Prof Paul Rogers, University of Bradford The Russians, I think, really surprised the West. They had got a crude Atom Bomb testable, and they actually tested it, in 1949. Most people seem to think that was three or four years ahead of when the Americans expected them to do it. The bigger surprise, though, was the development of the H Bomb, because whilst the United States had developed an H Bomb by about 1952 and tested a crude one, the Soviets came in only a year later. So in that sense there was a lot of progress on the Soviet side. It took them years to deploy the finished systems, but at the testing levels they were pretty advanced.
Narrator With the Cold War growing in intensity the British desire to move forward could only increase. Every effort was put into making the Windscale Piles as efficient as possible to meet the deadline for a first atomic test in 1952. And although the production of Plutonium reached its target on schedule, there were some worrying incidents in the behaviour of the reactors that year. In May there had been an unexplained temperature rise in the number two pile, and four months later smoke was seen coming from the core of the other reactor following a shut down. It turned out the smoke was simply caused by oil particles being blown onto the hot graphite from the cooling fan bearings, but the unexpected temperature rise was a worry for scientists. Consultations were carried out with the Americans, and it became apparent the cause lay in the release of Wigner energy - something Harwell had been warned about three years earlier. A month later, on the 3rd of October 1952, the first British atomic test was carried out aboard a ship moored off the north west coast of Australia using Plutonium from Windscale. For the politicians and scientists it was a triumph. Britain had gained entry to the nuclear club.
David Holloway Prof David Holloway, Stanford University Building the bomb seemed the natural thing. It was one of the great powers, despite being greatly weakened by the economic costs of the War. But still it was a natural thing and hardly anybody opposed the decision. Of course it was carried out in secrecy - there wasn’t a great public debate about it. It just sprang from a certain assumption that Britain should have the bomb. And the British did in fact expect to be the second to develop an Atomic Bomb and were very taken aback by the Soviet test which came in 1949 when the first British test was 1952. And Western intelligence had predicted that the first Soviet test would probably be 1953, maybe 1954. So the British suddenly found they weren’t the second nuclear power, they were now the third nuclear power. And increasingly through the fifties, especially after both the United States and the Soviet Union developed the Hydrogen Bomb, the again Britain was lagging further behind. So I think the 1950s were a period of some tension in British nuclear policy because there wasn’t a fundamental revision of assumptions saying "we shouldn’t have these things at all", "we can rely on the Americans", or "we don’t need them" or "they’re immoral" or whatever. So the Government didn’t go that far. On the other hand they were finding it very difficult to keep up in this race when the United States and the Soviet Union could mobilise such massive resources into not merely developing new kinds of weapons but building large numbers of them and delivery vehicles and so on. So I think it was a very difficult period for the British.
Narrator Throughout the mid-fifties, atomic tests were carried out by each of the three nuclear powers. The Windscale Piles remained the only production source of Plutonium in Britain and there was heavy pressure on the Atomic Energy Authority production group not only to meet demand for that element but also for others such as Tritium and Polonium, required for the testing of a Hydrogen device. So two reactors of a new type cooled by Carbon Dioxide rather than air were commissioned next to the existing piles, and construction work began in August 1953. Two years later the need for Plutonium had become so desperate that a further six of these Magnox reactors were ordered.

Meanwhile, a system had been developed to deal with the build up of potentially hazardous Wigner energy in the graphite core of the Windscale Piles. After every 30,000 Megawatt days of irradiation it would be released by a process called annealing. Although the technique occasionally threw up a problem, generally it worked well. But then, in October 1957, there was the accident scientists feared most. During the 9th anneal the worst case scenario predicted in 1949 by Wigner and Teller came about . The number one pile caught fire.

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