Alpha rules of thumb

[Joelle Key <jkey@mail.state.tn.us>]

A few years ago I was given a handout with the following "rules of
thumb" for detecting alpha contamination.  Can anyone confirm the
accuracy of these ROT?  Does anyone know where I might find
supporrting documentation for their use?

Scanning (~ 3 cm/sec)  can detect 300 dpm
Integrated  (1 min)         can detect 100 dpm
Probability of detection (<500 dpm) is around 90%

I suspect the last one should be >500 dpm.  But that is how my handout
reads.

Thank-you for any information you can provide me on this subject.

Joelle Key 
TN - DRH
jkey@mail.state.tn.us