# Itarare Group Sandstone as a Sustainable Alternative Material for Photon Radiation Shielding
## 1 Introduction  
The use of radioactive sources in various applications, including medical imaging, radiation therapy, and industrial processes, requires effective radiation shielding [1]. A range of materials is available for this purpose, including lead, concrete, rocks, and polymers [2, 3]. Typically, materials that are denser and consist of elements with high atomic numbers are preferred [4]. However, some of these materials, such as lead and concrete, can be toxic, heavy, and costly, and they may deteriorate over time. Therefore, it is essential to explore alternative materials for radiation shielding. One of the significant challenges facing our planet is the production of radioactive waste by the nuclear industry and power plants. The increasing demand for safe radioactive waste management highlights the need to explore alternative methods to protect humans from the harmful effects of radiation [5]. Therefore, it is essential to identify materials that can effectively shield against radiation, especially from photons. Rocks present a compellingalternative for this purpose, as they are composed of materials with moderate atomic numbers [6; 7]. Furthermore, rocks are abundant and less expensive compared to synthetic materials, such as polymers. This widespread availability facilitates the construction of remote storage facilities. Another advantage of using rocks is that they can be combined with other materials to create composite materials, which can enhance their effectiveness in radiation shielding [8; 9; 10]. Gamma and X-ray photons are often produced by medical equipment or emitted by radioactive sources, such as those found in radioactive waste. The effectiveness of different materials in shielding these photons varies based on the energies involved [11]. For rocks, the elemental composition is a key factor that affects radiation shielding. Additionally, the structure of the rock, which influences its density, plays a crucial role in determining how well it can shield radiation [12]. The presence of elements with higher atomic numbers improves a material's ability to attenuate photons. Therefore, simulating how photons interact with rocks of various chemical compositions and structures is essential for understanding these materials' effectiveness in radiation shielding. To understand how materials shield against radiation, a crucial parameter to calculate is the linear attenuation coefficient (LAC). However, because the LAC depends on the material's density, the mass attenuation coefficient (MAC) is more useful when comparing materials of different densities [13]. Other important parameters include the mean free path (MFP), the half-value layer (HVL), and the tenth-value layer (TVL). These parameters are essential for understanding how photons interact with matter. For instance, the HVL and TVL indicate the thicknesses of materials needed to attenuate 50% and 90% of photons, respectively [14]. In addition to the previously mentioned parameters, two key factors in quantifying the complex interactions between photons and matter are the energy buildup factor (EBF) and the exposure buildup factor (EABF). The EBF is defined as the ratio of the total photon energy fluence--comprising both primary and scattered photons--to the primary photon energy fluence at a specific point within a shielding material. On the other hand, the EABF represents the ratio of total exposure, which includes both primary and scattered photons, to exposure from primary photons alone at the same point within the shielding material [15]. In practical terms, the EBF indicates the increase in radiation dose due to secondary photons, while the EABF reflects the increase in exposure, demonstrating the amount of ionization in the air caused by these photons. Very few studies have investigated the radiation shielding properties of sandstones [16; 17], despite their potential relevance.