[ RadSafe ] Gross Alpha questions

[Khalid Aleissa]

Actually, the proportional counter measurement of water gross alpha is an
old technique that has many uncertainties. One of these is the
self-absorption  which makes the maximum useable water sample should not
exceed 500 ppm of total dissolved solids. Once you establish
your  self-attenuation curve for your instrument by adding standard alpha
emitter to different sample TDS (100 to 500 ppm), you will find that above
500 ppm the sample size will be so small to a level it threatens the
sensitivity. Although this procedure still formal standard procedure in
some countries which makes it difficult to change (because of
the complicated government  system or other similar non technical reasons),
therefore, I think we should change to another one, i.e., using LSC for
gross alpha and gross beta with high sensitivity and less preparation.

Best regards

Khalid A. Aleissa




On Fri, May 11, 2012 at 4:19 PM, Michael E. Kitto
<mek14 at health.state.ny.us>wrote:

>
>
> Gross alpha activity can be determined by measuring planchets on
> gas-proportional counters.  We have a limit of 100 mg (5 mg/cm2) of
> precipitate on the planchet.  Does anyone have a method of estimating the
> maximum volume of a water sample that can be evaporated to stay below this
> limit without "trial and error" or pre-evaporation of small aliquot ?  For
> example, will a conductivity meter or turbidity measurement provide an
> estimate of the amount of dissolved solids?  I am looking to develop a
> correlation of the measured precipitate (dissolved solids) with a (yet to
> be determined) parameter.  Thanks in advance, Mike Kitto
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