Design of an electrochemically assisted radiation sensor for α-spectrometry of actinides traces in water

•The method allows to find trace of actinides in water.•The method allows direct α spectrometry of actinides in aqueous solutions.•Alpha spectrometry is performed without the use of a vacuum chamber.•Decontamination of the sensor before re-use is very fast and efficient.•Detection limit is lowered by concentration of actinides at the detector entrance window.

We describe a new approach for the detection and identification of actinides at low activity levels directly in aqueous solution. The measurement consists initially, in immobilizing alpha emitters in the form of insoluble hydroxides onto the entrance window of an immersed alpha particles detector. For this, a boron doped diamond detector window is negatively polarized to produce a basic layer on its surface by water decomposition. Actinides elements that are known to be very sensitive to hydrolysis are precipitated as solid hydroxides onto the entrance window of the sensor. Due to the absence of an air layer between the radioactive source and the detector, there is no need for vacuum during the alpha spectrometry measurement. After analysis, the detector can be easily cleaned by anodization in the aqueous medium to be reused at once. The minimum detectable activity concentration (MDA) of the system has been evaluated with 241Am at 0.5 Bq/L for a 0.33 cm2 area Si PIN diode.