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Identifying strontium-90

Problem

Identifying strontium-90 is a difficult task. There are many unknown variables, such as shielding and scattering involved and the spectrum of strontium is heavily affected by this. Common nuclide identification instruments rely on an automated interpretation of the energy spectrum taken from a radioactive source. In the figure on the right side, you can see in the top section a sample spectrum of strontium-90 plotted in red. The omnipresent potassium-40 radiation is shown in black. Only a small area in the first channels points towards the presence of an additional source.

Maximum-likelihood deconvolution

In a work of 2013, I proposed a possible solution to tackle the presence of strontium by using a so-called maximum-likelihood approach. Basically, this method incorporates knowledge about the true, unvariable contributions that strontium puts into an energy spectrum. Based on these traces, the deconvolution classifies wether the spectrum contains these traces or not. An example result for the masking with potassium is given in the lower part of the righthandside picture.

Strontium-ID as soft-sensor

The strontium ID module is used one single agent within a multi-agent system for nuclide identification. This system uses communication strategies to extract the ID of a nuclear source. Additionally the module acts as a soft-sensor in the strict sense, that prior knowledge and the measurement of one sensor are fused to achieve a principally new output.

Further reading

About the chemical element strontium

Wikipedia article about maximum-likelihood

Publication

Marcus J. Neuer, Spectral identification of a 90Sr source in the presence of masking nuclides using Maximum-Likelihood deconvolution, Nuclear Instruments and Methods in Physics Research A, Volume 728, p. 73-80, 2013, DOI: 10.1016/j.nima.2013.06.013