RE: help on point source calculations

["Bradshaw, Keith" <Keith.Bradshaw@nnc.co.uk>]

Other RADSAFERs have given simpler solutions to this specific problem.  Just
to add something, I've found an equation which dates back a bit (looking at
the units):

Exposure rate at 1 metre (R /h /Ci), k  = 1.32 for Co-60
Then exposure rate from a point source (R /h /Ci) = kA /d^2  where A is the
activity in curies and d is distance in metres
(Exposure in *roentgens*)

For the line source, you might envisage segmenting the 11 inches into say
1-inch segments and treating each segment as a point source of 1/11 of the
total at various distances.   It's probably a lot easier to actually measure
it :-)


> Can anyone show me how to do the following problems? or send me some good 
> examples with equations. 
> 
> If the Co-60 point source had a radiation intensity of 4.2 R/hr at two
> feet, 
> the distance at which the exposure rate would be 100 mR/hr  is ? 
> 
> What equation do I use and please give a example on how to do it.
> 
> 
> next question
> 
> Calculate exopsure rate at 3' from a 11' long line source. The line source
> is 
> reading an exposure rate of 600 mR/hr at 1 inch from the line.
> 
Regards

keith.bradshaw@nnc.co.uk

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