[ RadSafe ] Gamma Radiation and Fire Eyes

[Walter Cofer]

Rob -

Thanks for the tip regarding inadvertent tripping of "fire eyes" alarm
systems.

However, let me caution you against referring to gamma radiography as
"x-raying" when posting to the Radsafe list.  It is a common practice in the
construction/maintenance industry to refer to all industrial radiography
operations as "x-ray testing" regardless of whether an x-ray machine or
isotope is used.

Based on your post, I suspect that it was an iridium-192 source being used
by the radiography crew, not an x-ray machine.  Gamma emitters such as
Ir-192 and Co-60 are used in the vast majority of field radiography
applications due to their greater penetrating power and portability.  While
is may also be possible for lower energy x-rays to set off a fire alarm
system, my guess is it was the high energy gammas from Ir-192 (mean E of 357
keV) that set off the alarm in question.

The lesson I got from your post is that radiographers should consider
informing their clients of the potential for the radiography sources to set
off such alarms and that preventive measures may be in order.  I will pass
it along.

Thanks,

Walt Cofer
Industrial Safety Consultant
Radiation Control Inc.