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Abstract: 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 0.5Bq/L for a 0.33cm2 area Si PIN diode. [Copyright &y& Elsevier]

• Diamond detector test with Neutron source and in the VR-1 reactor. • Pulse shape discrimination conditions were studied and set. • up to 33% of pulses were alpha interactions in reactor measurement. Diamond crystal-based detector for neutron flux measurement is a promising solution as a fast, small and stable detector especially suited for fast transient measurements. The work aims to test the method and to find the best parameters of the pulse shape analysis for the thermal neutron detection. The developed diamond detectors were tested with the AmBe neutron source and in the VR-1 reactor core. Based on the results obtained from the AmBe measurements, the discrimination conditions for the pulse shape analysis were set and optimized. The diamond detector was then tested in mixed n- γ field of the nuclear reactor core. First results from the VR-1 reactor measurement showed high yield of thermal neutron interactions (up to 33% of all recorded interactions, like in AmBe measurements). The presented results therefore proved that diamond detectors are promising for the fast transient measurements. [ABSTRACT FROM AUTHOR]