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In recent years, the use of radioactive Co-60 in high-dose level brachytherapy (HDR-BT) has grown rapidly. This study aims to model the HDR-BT source, precisely the Bebig Co0.A86 type, and determine its spectrum characteristics. The simulation utilizes the GEANT4 Monte Carlo code to model radiation sources and irradiation systems. The BEBIG Co0.A86 brachytherapy source was modeled by encapsulation source. The beam characteristics of the source were simulated in a spherical scoring region. The scoring region had a radius of 50 cm with water medium, as recommended by the TG-43U1 protocol, and different scoring region sizes were considered: 10 cm, 20 cm, 30 cm, and 40 cm. The physical interactions used in the simulation were performed using the penelope model with 108 generated photons (history). The characteristic parameters of the photon spectrum in the scoring region were analyzed using the root program. The GEANT4 Monte Carlo simulation revealed two photoelectric energies of cobalt at 1.173 MeV and 1.332 MeV and the Compton edge in the energy distribution spectrum of the Bebig Co0.A86 model. The discrepancy between the Compton edge simulation results with theoretical calculations is about 3.22%. The source encapsulation with stainless steel material and the addition of cables to the source model did not affect the energy spectrum distribution pattern of Co-60. Furthermore, the results show that the photoelectric energy significantly decreased with increasing scoring region size, while the Compton continuum area increased accordingly. Additionally, the GEANT4 Monte Carlo method illustrated the differences in the spectrum distribution of HDR-BT Co-60 with variations in scoring region size. The scoring region size of 10 cm shows that the photoelectric effect has an amplitude almost equal to the Compton edge and Compton Continuum. [ABSTRACT FROM AUTHOR]

The climate change is one of the greatest challenges faced by human being in the 21st century. This phenomenon does not only affect the earth's ecosystems, but it also has a significant negative impact on human life. Climate change is causing the earth's temperature to rise globally, leading to drastic changes in weather patterns, rising sea levels and threats to the sustainability of natural resources and food supply. One of the preventive strategies to reduce the impact of climate change is improving young generation climate change literacy, and more specific, is fostering the students' climate change literacy. Specific learning models and approaches are therefore needed to develop this students' literacy. To realize it, we designed the RBL-STEM learning activities which is a combination of RBL (Research-Based Learning) model with STEM (Science, Technology, Engineering and Mathematics) approach. The contextual problem on tackling the climate change issue is recycling the plastic waste into ecobrick. This contextual problem is a makerspace on RBL-STEM learning activities. We used a narrative qualitative method for doing this research where an analytical approach was used to design the RBL-STEM learning activities. The results showed that there are six stages of the RBL-STEM learning activities on recycling the plastic waste into ecobrick. This study also presents the indicators and sub-indicators of students' climate change literacy to be a guideline for learning materials development, especially the assessment instruments. [ABSTRACT FROM AUTHOR]