Analytical Methods Gross Alpha Beta

A proportional counter with heavy shielding is recommended for this method. The instrument is calibrated by adding radionuclide standards to a matrix similar to the sample. A standard solution of cesium 137 or strontium 90 certified by the National Institute of Standards and Technology (NIST) is suitable for gross beta analysis. A solution of natural uranium, thorium, plutonium 239 or americium 241 is recommended for gross alpha analysis. Gross alpha-beta results are always reported in comparison to a specific standard.

The sample, usually a liquid, is evaporated onto a planchette, to a thin film. The standard is prepared in the same manner. Counts from the sample are then compared to the standard. Samples suspected of containing fission or artificial radionuclides can be tested for gross beta using either the cesium or strontium standard. Environmental samples suspected of containing natural radionuclides can be tested for gross alpha using any of the alpha standards previously listed. Careful attention must be paid to self absorption of alpha and beta particles due to sample thickness on the planchette whenever test results are evaluated.

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