Speaker
Description
The NAUTILUS project aims at determining nuclear data for chlorine to contribute to the research on chloride-based molten salt fast reactors. Therefore, experimental methods based on the principles of neutron activation analysis, neutron transmission and pile oscillation are utilized in the neutron field of the AKR-2 training reactor (Chair of Hydrogen and Nuclear Energy, Dresden University of Technology, Germany). However, a quantitative evaluation of the experimental data is only possible if its underlying field is precisely characterized. Thus, a further goal of the NAUTILUS project is the determination of the spectral neutron flux for different energy ranges of the AKR-2’s neutron spectrum.
Regarding the evaluation of the fast neutron spectrum, neutron detection via elastically scattered recoil protons can be exploited. Different kinds of detectors exist for this purpose. However, they are suitable for measuring neutrons of different energy ranges. Hydrogen-filled proportional detectors can be utilized for measuring neutrons with energies between about 50 keV and 1.2 MeV. Stilbene scintillation detectors can be used for measuring neutrons with energies higher than approximately 1 MeV. Both detector types hold pulse shape discrimination capabilities allowing separation between neutron- and photon-induced detector events. Histograms of deposited energies by neutrons can be unfolded if the detectors response matrices are known. By this, the spectral neutron flux for fast neutrons can be determined.
This contribution presents a novel setup for measuring neutron energy deposition in the fast energy region. It is suitable for pulses generated from hydrogen-filled proportional detectors and stilbene scintillation detectors alike. In the setup, the detector’s analog signals are digitized via an analog-to-digital converter. The latter is coupled to a field-programmable gate array which digitally realizes pulse shaping, baseline restoration and threshold triggering via custom-made logic modules. Additional custom software is used for configuring the setup and controlling the data acquisition and evaluation process.
Experimental results yielded by utilizing the setup for measurements with hydrogen-filled proportional detectors and stilbene scintillation detectors will be shown. Characterization methods and pulse shape discrimination capabilities of the detectors will be discussed by means of evaluated measurement data. Analog data from particle transport simulations with the Monte Carlo code Geant4 will be examined for comparison. Further steps in the scope of the NAUTILUS project to determine the spectral neutron flux of the AKR-2’s fast neutron spectrum will be illustrated.
