[ RadSafe ] Apparent loss of activity of Tc-99 check sources

[WHILLANS David -NUCLEAR]

The following request for information is posted on behalf of Bob
Hanrahan, Manager of the central RP Field Support group at OPG. Please
reply directly to Bob at robert.hanrahan at opg.com .
 
Dave Whillans, Senior Scientist, Health Physics Department, Ontario
Power Generation - Nuclear, Canada 


Since converting to Tc-99 for the calibration and sensitivity checking
of whole body contamination monitors, we have experienced significant
decreases in the cpm/nCi detected from some calibration and sensitivity
check sources, while other Tc-99 sources of the same type have not
changed.

Have any other users of Tc-99 calibration and sensitivity check sources
experienced this effect - did the source manufacturer provide any
explanation for the effect - does anyone have an explanation for the
effect?





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