[ RadSafe ] Re:Reasonable risk?

[Peter Ryge]

Jerry Cohen asked: In radiation safety, is there any level of exposure so low that action to further reduce it can be considered unwarrented?

One answer for x-ray security screening is in the standard "Radiation Safety For Personnel Security Screening Systems Using X-rays" (ANSI N43.17-2002). It allows a dose per scan of  0.1 microSv (10 microrem) for general screening. The rationale is that any individual would be screened less than 100 times per year, not exceeding the annual NID ("negligible individual dose") which is 0.01 mSv (1 mrem). 

Quoting from the standard: "The NCRP defines a category for extremely low radiation exposures called the Negligible Individual Dose (NID), and sets its value at 0.01 mSv (1 mrem) per year. At radiation exposures below the NID, efforts to reduce the dose further are not warranted."

This is elaborated in NCRP Statement No. 10 (page 5) which cites NCRP 116.

Peter Ryge
Rapiscan Systems 
pryge at rapiscansystems.com