Rapid pretreatment of environmental samples of food and related materials by a microwave dehydration method

Abstract

A rapid and simple radioactivity determination method has been developed for food and related environmental samples of a radioactivity level corresponding to 5 mrem/y, Japan AEC's guideline, by pretreating with a modified microwave dehydration apparatus followed by radiation counting. An equation to estimate the heating conditions by the apparatus has been derived, and results calculated by the equation are in good agreement with experimental data. It took less than 4.5 hours to dehydrate by the propossed method, and radiation counting could be started on the day of sampling and dehydration procedure. The lower limit of detection for each radionuclide by the proposed method, using a Ge(Li) detector of 20% relative efficiency, is lower than one half of the needed detection limit to determine and evaluate the 5 mrem/y level. Radionuclide levels in food samples such as vegetables and crustaceans were determined by the proposed method and it was found that they were below the lower dection limit of the proposed method except natural radionuclide⁴⁰K and fallout-originated¹³⁷Cs.