Operation Hurricane was the test of the first British atomic device on 3 October 1952. A plutonium implosion device was detonated in the lagoon between the Montebello Islands, Western Australia. The weapon was a close copy of the Fat Man (Nagasaki) weapon, although the design was modified to use a levitated pit. This increased the power of the bomb, but was actually done as a safety measure. There were concerns that without the gap between the tamper and the pit, a criticality accident could occur. The bomb used plutonium produced mainly at Windscale (now Sellafield) in Cumbria with a low plutonium 240 content since hurried production led to short irradiation times. However, Windscale could not quite meet the 1 August 1952 deadline for manufacturing the inner core and the device also used