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| Fig. 1: This statue of a cow with nuclear reactors in the background represents the unprecedented effects on cattle pasture that resulted in the contamination of the milk supply after the Windscale catastrophe. (Source: Wikimedia Commons) |
Windscale is located in Sellafield in the United Kingdom and was originally built as a military installation. By the 1950's it was home to Britain's nuclear industry. It had two nuclear piles (today known as nuclear reactors), which were enclosed in concrete towering structures with the reactors at the base with air-cooled graphite cores. On October 10, 1957 a fire erupted in Pile 1 and the fire was not put out until the evening of the October 11 after a dangerous endeavor to flood the reactor with water. The cause of the fire is accredited to a combination of the release of Wigner energy and the rupture of a fuel element in the pile. [1] The Pile 1 damage was deemed irreversible and it took engineers nearly half a century to devise a plan to safely dismantle and dispose of the remains.
Wigner energy is stored potential energy that is released as heat when the graphite cores are exposed to neutrons. The engineers at Windscale designed the release of this energy in an annealing process where the core temperature was raised immediately and temporarily, followed by cooling of the core. On the day of the accident, however, this annealing process caused the temperature of the core to rise substantially causing a fire to break out. The actual cause of the accident is still unclear, as many design flaws presumably contributed to the accident. Nonetheless, Windscale remains the worst nuclear accident in Great Britain's history and resulted in many consequences that reached beyond the reactor site and could still have continued effects today. [2]
Radioactivity affecting a country's food supply became a main concern during the atomic age and the Windscale Fire is a prime example of this concern. Authorities began to monitor the effects of the Windscale Fire by examining the downwind external radiation levels as a result of the stack exhaust. Among the downwind areas impacted were many cattle pastures feared to have been contaminated with radioactive byproducts (See Fig. 1). Upon further investigation, officials found high levels of iodine-131 in the milk from the cows who consumed contaminated pasture. [3] Although officials were able to quantify the amount of iodine-131 found in the milk, no previous rules had been set stating the threshold for permissible levels of contamination. Authorities quickly devised a plan to set a permissible level of iodine coming to a consensus of 0.1 microcurie iodine per liter of milk. This limit was implemented to constrain thyroid doses with a focus on cases in infants and children as their main source of nutrition was milk. [1]
Wide scale sampling in the downwind area began and resulted in the condemning of 250,000 gallons of milk over an area of 200 to 300 square miles from roughly 600 herds of cattle. Due to public anxiety, although the milk could have been salvaged for use in livestock feedings or manufacturing processes, the condemned milk was thrown out. Despite the large size of the affected area, given the relatively short half-life of iodine, two to three weeks, the situation only was threatening for the duration of the half-life. The quick action of officials was crucial to preventing more serious consequences. [3]
Although the Windscale Fire resulted in the unprecedented consequence of a contaminated milk supply, it did ignite the movement for increased safety mechanisms that are present in nuclear technologies today. For example, reactors today have new built-in safety and control features that will help to prevent an accident of this severity from occurring again. Additionally, it exposed the need for more public and scientific understanding of the risks of these incidents.
© Tatyanna Dadabbo. 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. M. Harrison and R. E. Hester, Nuclear Power and the Environment (Royal Society of Chemistry, 2011).
[2] D. Eves, Disasters: Learning the Lessons for a Safer World (Routledge, 2015), pp. 121-124.
[3] A. H. Wolff, "Milk Contamination in the Windscale Incident," Public Health Rep. 74, 42 (1959).
