AbstractMapping and measurement of radiation is a crucial activity to be performed when
radioactive sources are involved, for example during decommissioning of existing
nuclear power plants. These environments require fast and reliable devices able to identify the type and amount of the source but also to provide their geographical distribution. Since emitted photons have the longest life-time and carry specific energies typical for each isotope, gamma spectroscopy is the most common technique used. Spectrometers usually use semiconductor detectors. Their properties allow to build small and light detector systems. This makes them attractive for integration in Unmanned Air Vehicles (UAV). This is a key feature when considering deployment in hostile or dangerous conditions where human access is too dangerous. However, high precision spectroscopy systems have a limited bandwidth, which ultimately translates into a limit in the maximum dose rate they can measure. The system proposed overcomes this issue. The apparatus is based on a matrix of 5 different semiconductors (Silicon, Gallium Arsenide, Uranium Dioxide, Cadmium Zinc Telluride, and Diamond) which, thanks to their different response to incident photons of different energies, allow the identification of a large variety of isotopes by comparing count rates in the individual detectors after using a simple, fast thresholding system. This detector system allows the detection of the most common 12 isotopes (whose energies range from some keV to approximately 2 MeV) usually found in nuclear power plants at very high dose rates. A large GEANT4 simulation study was performed to prove the validity of the system, demonstrating that the detector will exhibit excellent performance as a fast readout gamma spectrometer in high radiation fields, and in addition will provide the location of the sources.
|Date of Award
|23 Jun 2020
|Jaap J Velthuis (Supervisor) & Thomas Bligh Scott (Supervisor)