[ RadSafe ] Any experience in detection of polonium on large scale contamination ?
parthasarathy k s
ksparth at yahoo.co.uk
Sun Dec 10 22:54:00 CST 2006
Detection of polonium contamination by area monitoring has certain difficulties. Since the range of alpha particle from Po-210 is only a few cm in air and the gamma emision accompanying Po decay is very feeble, how do you carry out large scale area monitoring?
If you are using large area alpha scintillation counters, based on Zn S(Ag), one of the problems is to maintain the background counting rate at a low value.The thin (0.1 mg/square cm)aluminium covered window develops pinholes leading to light leaks. This results in stray counting. We had difficulty in less trying circumstances. we had to replace the thin alunmnium foil very frequently
This story is decades old! Now there may be better instruments availble commercially.I am an old hand and used to make large area scintillation counters by making alpha detector foils by sprayng fine ZnS(Ag) powder on transparent plastic sheets coated with silicone oil. Can any one in the list throw some light on newer methods if any? I was told that large area air proportional counters are available commercially. During the seventies we tried to develop spark counters with limited success.
Urine sampling etc is well developed and relatively easy though time consuming and is not applicable in area monitoring!The UK Health Protection Agency must be combing large areas
Not much is known about the methods used by them.
The infamous polonium poisoning incident is worrying for those who have to carry out area minitoring in case some rogue elements try to spray it in busy malls, shoping centres etc.
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