Automation of soil samples mineralisation for the measurement of their alpha activity

Environment samples analysis requests are getting more and more numerous, and this in order to get a following of the artificial radioactivity in the environment as perfect as possible. The alpha emitters (plutonium, americium) measurements are the one which are the must problematic because previous to the measurements a wide number of chemical separation operations are needed. Two important stages characterise this separation: the sample mineralisation to transfer the radioelements in solution and the chemical separation of the elements to be analysed. The traditional techniques, long and not so easy doing, tend to be replaced by new automatic techniques which are quicker and more reliable. A new soil samples mineralisation method, using a focalized and automatic microwaves oven, has been studied, tested and optimised. The measurements needed to determine the percentage of the radioactivity transferred in solution have shown that the studied soil contamination is not homogenous (showing for example variations up to a factor 10 for americium), which get us to realize our measurement on samples as big as possible. The percentage of radioactivity transferred in solution obtained through direct gamma spectrometry measurements shows very satisfactory and reproducible results (almost 90%). In conclusion, we can say that this study has shown the advantages of an automatic system like the one presented here, compare to the nowadays used methods. (author)