[ RadSafe ] The rad and mouse history

Nielsen, Erik nielseec at nv.doe.gov
Thu Oct 4 14:38:17 CDT 2007


The rad began, in 1918, as the dose required to kill a mouse, clearly an imprecise but usefully indicative amount. It received sharper definition in 1953, the International Commission on Radiology defining it in metric-c.g.s. terms as above. In 1956, it was accepted as the general unit of dose, displacing the roentgen in its use for x-rays; the rad is about 10% smaller than the roentgen, the precise relationship depending on the dosed material. Also expressed as 1 rad = 62.4 × 106MeV g-1.

Erik C. Nielsen 
Senior Scientist 
Remote Sensing Laboratory 
P.O. Box 98521, M/S RSL-47 
Las Vegas, NV 89193-8521 


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