The ninth anneal of Pile No.1 was due in early October 1957. Formerly anneals had been carried out after 30 000 megawatt days of irradiation, but the Windscale Technical Committee had recently decided to extend the interval to 50 000 megawatt days. However, the pile group manager, Ron Gausden, had asked for the change to be made in two steps, to 40 000 megawatt days on this occasion and to 50 000 later. So the ninth anneal was taking place after a longer irradiation period than before. Some small pockets of graphite, mainly in the front lower part of the pile, had apparently failed to release Wigner energy in the previous anneal and in these areas the irradiation probably amounted to 80 000 megawatt days.
KeywordsFuel Element Pile Group Nuclear Accident Friday Afternoon Friday Morning
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