Electron Capture Isotopes

[BRUCE9@delphi.com]

Monitoring Electron Capture Isotopes

Analysis of some of our contamination containing the steel
activation products Cr-51, Mn-54, Fe-55, Fe59, Co-58 and Co60
 show that the activity is dominated by the electron capture
 isotopes Fe-55, Cr-51 and Mn-54 ( up to a ratio of 30:1 wrt
 Co-60). 

Our normal method of monitoring items out of Contamination
Controlled Areas is to use either scintillation probes (NET
BP4's) or pancake geigers (HP260's), however these have very
low efficiencies for detecting the x and gamma radiation from
electron capture isotopes( approx 0.5%) and for this reason
we have begun using 44B X-ray detctorsas well.

I would be interested to know if any other facilities are
experiencing similar problems and how they ensure that items
removed from Controlled Areas are kept below regulatory
contamination levels.

bruce macfarlane
Stockton-on-Tees, UK