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| Fig. 1: View of the Windscale Piles in Sellafield, England. (Source: Wikimedia Commons) |
In the mid-1940s, the United Kingdom created a policy that allowed nuclear weapons to be manufactured in Great Britain. A large component of this policy was the construction of a plutonium production factory in (what was then) Cumberland, in North-West England (see Fig. 1). The plan was to build these reactors as part of the British post-war atomic bomb project. In September of 1947, construction for two piles began at the site that was renamed from Sellafield to Windscale. Each of these Windscale Piles were fueled by 180 tons of uranium metal fabricated into more than 70,000 aluminum clad elements. These were positioned into 3440 horizontal channels within 2,000 tons of graphite moderator. The main purpose of these Piles was to create weapons-grade plutonium, they were also used to create other nuclides. [1]
During the construction of these piles, it was urged by Sir John Cockcroft that there should be filters installed in order to remove the radioactive material that could already be present in the exhaust cooling air. Radiation detectors had located channels where bursts had occurred, but these were somehow left unattended to. Additionally, it was anticipated that the flow of cooling air would be so large that fuel elements would move along the channels. There were efforts taken to prevent this, but it was found that these elements were being blown out of the core, which led to a need for the re-design of these arrangements. Some elements were found to be stranded in locations where the irradiated metallic uranium fuel became oxidized in the cooling air as a result, radioactive particles were released from the chimneys into the environment. Additionally, there was Wigner energy stored within the graphite moderator. If released by accident, this could lead to high localized temperatures as well as the possibility of a fire. [1]
On October 10th in 1957, a fire occurred in the No 1 Pile at Windscale. This fire burned for three days, and led to an uncontrolled release of radioactive materials into the atmosphere, which was dispersed and deposited over England, Wales, and other parts of northern Europe. I-131 was the most important of the released radionuclides, due to its potential to cause cancer of the thyroid. This element was released due to its volatility. Radionuclides of iodine in general are transferred to human beings via the consumption of milk from cows that graze on pastures that are contaminated. Iodine that contaminates the human body is most concentrated in the thyroid gland. Though no one was evacuated from the surrounding areas, this incident therefor led to a ban on milk supplies to avoid high thyroid dose levels. [2]
© Caroline Lampl. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. Wakeford, "The Windscale Reactor Accident - 50 Years On," J Radiol. Prot. 27, 211 (2007).
[2] M. J. Crick and G. S. Linsley, "An Assessment of the Radiological Impact of the Windscale Reactor Fire, October 1957" Int. J. Radiat. Biol. Re. 46, 479 (1984).
