[ RadSafe ] Co-60 dose to those who handled the bare source in the Mexican theft incident , more incidents reported earlier by the IAEA

[parthasarathy k s]

A minor point. The specific gamma ray constant for a bare teletherapy source is assumed to be one R per hr at one metre and not 1.37.The bulky source offers nearly 30% self absorption.

Another important factor is the dose due to secondary electrons emitted from the wall material.Generally the wall material is steel.

Dosimetry at locations close to a sealed source is very complex. Besides the gamma dose, there is a dose component due to electrons scattered from the wall material.The fraction of dose due to this electron contribution depends on the energy of the source. The contribution to dose from scattered electron from the wall material can be as high as 45%. For Co-60 it may be as high as 30%. This part of the dose is readily absorbed in the first few mm of the tissue if the source is in contact.This results in severe burns.There are instances in which persons who kept sources in pocket in close contact with the skin suffering from such severe burns.

There are many instances of loss of control of sources leading to radiation accidents. The following link from the International Atomic Energy Agency describes some of them:

http://www.iaea.org/Publications/Booklets/SealedRadioactiveSources/sealedradsource1013.pdf

Regards
Parthasarathy