The RADIAC Calculator No. 1 was produced by the UK company Blundell Rules Limited and is based on the Radiation Dosage Calculator designed by William Orr of Connecticut University in 1951. The company moved from Luton to Weymouth in 1956. The calculator shown below must have been produced after that date since the back gives the company’s address as Weymouth. However, the company may have started producing the calculator as early as 1952. A lot must have been produced because they are often on eBay. They were used by other countries besides the UK.
The two smaller disks can be turned over after releasing the metal clip. One side is blue and shows the contamination results from a sea burst. The other side shows the contamination resulting from a land burst. This side may be pink or white. Possibly earlier versions were pink and then the company changed to white at some point. I assume that for both land and sea bursts a surface or sub surface burst is assumed since air bursts would produce much less radioactive fallout.
The RADIAC Calculator No. 2 was produced by Blundell Rules Limited of Weymouth England. Since the company moved to Weymouth in 1956, and changed their name in 1964, it probably dates from about 1960. The two inner disks are one sided. No distinction is made between land and sea bursts.
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