Characterization of neutron detection efficiency in a liquid organic scintillator

Neutron detectors in the form of liquid organic scintillators are widely used for nuclear disarmament purposes. The main purpose of this thesis is to characterize the neutron detection efficiency of the organic liquid scintillator EJ-309 using Monte Carlo based simulations in the simulation program Geant4. The Monte Carlo simulation code was benchmarked using recorded light output data from a laboratory experiment and it was confirmed that the simulation code could reproduce data from this experiment. In order to characterize the efficiency of the neutron detector, the benchmarked code was used to simulate light output distributions of 241-Am-Be and Cf-252, an (α, n) and a spontaneous fission source respectively, where it was found that the two different types of sources could be distinguished. However, distinguishment between two different spontaneous fission sources was not possible, as simulations of the light output distribution of another spontaneous fission source, Pu-240, was similar to the one for Cf-252. The light output distributions from the simulations were compared to earlier research where good agreements were obtained. A quantitative study was also performed to determine how many detected neutrons were needed to properly be able to distinguish between the two sources 241-Am-Be and Cf-252, and the number was found to be 560. This value was considered low relative to the number of detected neutrons in the simulations, and hence, more quantitative studies are needed in order to verify this result. The absolute and intrinsic detection efficiency were also determined for varying threshold values of neutron energy

Characterization of neutron detection efficiency in a liquid organic scintillator

Neutron detectors in the form of liquid organic scintillators are widely used for nuclear disarmament purposes. The main purpose of this thesis is to characterize the neutron detection efficiency of the organic liquid scintillator EJ-309 using Monte Carlo based simulations in the simulation program Geant4. The Monte Carlo simulation code was benchmarked using recorded light output data from a laboratory experiment and it was confirmed that the simulation code could reproduce data from this experiment. In order to characterize the efficiency of the neutron detector, the benchmarked code was used to simulate light output distributions of 241-Am-Be and Cf-252, an (α, n) and a spontaneous fission source respectively, where it was found that the two different types of sources could be distinguished. However, distinguishment between two different spontaneous fission sources was not possible, as simulations of the light output distribution of another spontaneous fission source, Pu-240, was similar to the one for Cf-252. The light output distributions from the simulations were compared to earlier research where good agreements were obtained. A quantitative study was also performed to determine how many detected neutrons were needed to properly be able to distinguish between the two sources 241-Am-Be and Cf-252, and the number was found to be 560. This value was considered low relative to the number of detected neutrons in the simulations, and hence, more quantitative studies are needed in order to verify this result. The absolute and intrinsic detection efficiency were also determined for varying threshold values of neutron energy

Conditions for digital use in after school centers

Barnen idag växer upp i ett digitaliserat samhälle, ett samhälle som ställer högre krav på individernas digitala kompetens. Tekniken utvecklas och förnyas ständigt och det är viktigt att skol och fritidsverksamheten hänger med i utvecklingen. Skolan och fritidshemmet har ett ansvar att utbilda eleverna i digitalt användande för att utveckla digital kompetens hos eleverna. Därför har vi i detta arbete valt att undersöka om fritidsverksamheten har de förutsättningarna som krävs för att uppnå målsättningarna gällande digitala verktyg som finns i styrdokumenten. Studien innefattar både en kvalitativ och kvantitativ metod där vi genomfört både enkäter och intervjuer. Resultatet av studien visar att fritidslärarna i vissa fall saknar kompetens för att bedriva digitala aktiviteter och att det saknas formell utbildning i digitalt användande hos fritidslärarna

Minimizing greenhouse gases emissions and energy consumption from wastewater treatment plants via rational design and engineering strategies: A case study in Mashhad, Iran

Wastewater treatment plants (WWTPs) play direct and indirect roles in the emission of greenhouse gases (GHG) produced by biological processes and energy consumption, respectively. Nowadays, reducing GHG emission and the energy consumption of WWTPs are of interest. In this study, at first, the GHG emissions and energy consumption of the Mashhad WWTP (MLE and aerobic digestion process) were compared with energy self-sufficient WWTPs. In the next stage, four scenarios were developed to reduce GHG emissions and energy consumption. According to the results, energy consumption and GHG emissions in this WWTP is outside of the acceptable value. By changing aerobic digestion to anaerobic digestion, the energy consumption will decreases from 1 kWh/m3 to 0.58 kWh/m3, and the total amount of CO2 equivalent (CO2e-T) increases from 0.64 kg CO2e/m3 to 1.65 kg CO2e/m3. In order to reduce energy consumption and GHG emissions, anaerobic digester and CHP must be used together. This process leads to reduced energy consumption and GHG emissions by about 70% and 53% , respectively. The lowest (highest) GHG emissions will occur in MLE with anaerobic digester and CHP (without CHP). Based on this study, GHG emissions and energy consumption can be controlled by selecting a correct process for WWTPs