MadSci Network: Physics

Re: Are longer half lifes truely more dangerous than shorter half lifes?

Date: Fri Jul 14 13:24:20 2006
Posted By: William Lorenzen, Staff, Radiation Safety, Children's Hospital
Area of science: Physics
ID: 1152688080.Ph

Not necessarily...

I would suggest you read further into the issue.  Here is one reference

The decay rate (or half-life) defines the rate at which a material 
transforms itself...  A 30 minute half-life material will still be 
releasing radiation after one half-life or 30 minutes.  The amount of 
radioactive atoms left after the first 30 minutes would however we reduced 
by 50% (one half as much)....  The rule of thumb is it takes about 10 half-
lives to have a radioactive material decay (or transform enough atoms) to 
a sufficently small amount so that it is no longer considered adioactive...

For a 30 minute half-life material that would be 30 x 10 or 300 minutes.

The length of time near the source, distance from the source, and the type 
of radiation emitted (Alpa, beta, gamma) will also be very important in 
determining the health risks.


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