Promethium 147 in laboratories

[Roger Gelder <74167.2472@CompuServe.COM>]

When I used to be with our Services Department, providing routine surveys in laboratories, one of the 'less-than-infrequent' events was the contamination arising from mis-use of beta back-scatter thickness gauges.
     The sources - usually a range for different thicknesses of eg paint paper etc, hence promethium, thallium, strontium - consisted of beads(~1/2 mm size) of active material mounted on very fine wire. It did not take too much violence when inserting a test sample for the bead to be "removed" and being in ceramic (I think) form, it was readily crushed without being noticed, until the next survey!
     The result was usually a write-off for the back-scatter gauge - try costing several hours of fine engineering decontamination against the cost of the equipment - OUCH! The bench was usually simple but the rest was expensive. 
     I suggest a check for such apparatus and it's recent use in the cold lab.
     Roger Gelder, NRPB, UK