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Is their any long term health hazard of nucleonic gauges having Cobalt 66 as an radioactive element, used for level measurement in granular solid catalyst?
 
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25/07/2018 A: sagar dandekar, Bharat petroleum, sagar.girgaon@gmail.com
It's cobalt 60
25/07/2018 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
Cobalt 66 has a very short half life (around 0.2 s) so I believe it is completely unsuitable as a radioactive source element for granular solid catalyst level measurement. The shorter the half life, the more frequent recalibration is required and the greater the exposure risk to personnel. I am aware of Cobalt 60 (photon energy ca 1.33 MeV, half life 5.3 years) being used in some applications, but Cesium 137 (photon energy 0.56 MeV, half life ca 33 years) is much more commonly used.
In all cases, safety precautions to minimise exposure of personnel to radiation include positioning the source and detector away from high traffic areas (eg. stairways), installing lead shielding, implementing strict lock out/tag out procedures for vessel entry etc. The radioactive source holder is typically a lead block with a small aperture and shutter encased in a carbon steel enclosure. The shutter must be closed for vessel entry.