Analiza aktivacije vode po obsevanju z nevtroni

Water as a primary coolant will play an important role in the performance of fusion reactors, as after being irradiated and activated, it causes an ionising radiation field throughout the facility. Therefore, additional protection and shielding for the instruments and personnel must be adequately considered. As part of this dissertation and in direct support of ITER, the KATANA irradiation facility, which utilises a closed-water activation loop, was designed, constructed, experimentally evaluated and studied, and successfully commissioned in 2024 at the TRIGA Mark II research reactor at the Jožef Stefan Institute in Slovenia. In this dissertation, a comprehensive overview of the KATANA, which serves as a well-defined and stable high-energy (6 MeV - 7 MeV) gamma and ∼1 MeV neutron source, is given, including the design optimisation analysis, final design, experimental set-up, detector systems. The physical characteristics of KATANA were assessed by analyses of neutron transport simulations leading to activity calculations in connection with a conventional analytical approach, without using CFD calculations. To complement the computational analyses, a series of first experiments was performed to determine the operational characteristics of the KATANA, i.e. characterisation of the neutron flux within the irradiation component, dose rate measurements, spectrum characterisation of the activated water, and response to a change in reactor power and flow rate. Since the performance of the pump and thus the flow rate was gradually improved several times during the commissioning phase, not all experiments were carried out under the same conditions. KATANA facility demonstrated the desired operational characteristics in terms of high and stable water flow rates and high activity values of the observed isotopes 16N, 17N and 19O, which is essential for minimising the experimental uncertainties. The calculations and first experiments performed at KATANA provided in-depth knowledge into the operation and capabilities of the facility and essential data to serve as a basis for further, more detailed experiments. The ultimate goal of KATANA is to perform benchmark-quality experiments, e.g. validation of fluid activation codes, and to establish itself as a reference facility for the calibration of high-energy gamma-ray detectors, which will significantly support the operation of ITER and other future water-cooled fusion reactors. The work has also been done within the framework of EUROfusion as part of the work package Preparation of ITER Operation.