## 4 Discussion  
The most important consideration of radiation-shielding clothing made using shielding materials with X-ray absorption characteristics is the activities of the wearer. Radiation-shielding clothing currently used in medical applications and in industry imposes many restrictions on user activities because of its heavy weight. Therefore, various studies have been conducted to discover new shielding materials and develop manufacturing process technologies for the production of lightweight shields [30; 31; 32]. The most meaningful aspect of this study is that it proposes a specific manufacturing process for mass production. The yarn containing the existing shielding material was manufactured from organic and inorganic composite fibers, and their manufacture employed the wet spinning process by using a cellulose solution through a lyocell process. Although that method may increase the mineral content, it is difficult to use for mass production due to the solvent removal stage in the fabrication process [33; 34; 35; 36]. The conditions for spinning yarn that maintains a constant strength during the process of weaving shielding fiber are difficult. If the shielding material content--that is, the amount of mineral--is increased, the shielding performance will be excellent, but the tensile strength will be weakened, which can cause problems in weaving. Conversely, if the mineral content is reduced to facilitate \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Radiation Type**} & \multirow{2}{*}{
\begin{tabular}{c} **Effective X-Ray** \\ **Energy (keV)** \\ \end{tabular} } & \multicolumn{2}{c}{**Radiation-Shielding Rate (\%)**} \\ \cline{3-4}  & & **Containing BaSO\({}_{4}\)** & **Containing Bi\({}_{2}\)O\({}_{3}\)** \\ \hline \multirow{4}{*}{X-ray} & 25.2 & 13.8 & 21.5 \\  & 27.9 & 11.5 & 18.4 \\ \cline{1-1}  & 31.4 & 9.4 & 12.8 \\ \cline{1-1}  & 42.8 & 8.6 & 10.2 \\ \cline{1-1}  & 50.8 & 7.4 & 9.4 \\ \cline{1-1}  & 57.2 & 4.1 & 7.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Shielding performance of the shielding fiber fabrics. Figure 7: Radiation transmittance according to Al thickness. weaving, the shielding performance will be reduced. Therefore, the optimum conditions must be determined. In this study, yarns of PET fiber were fabricated using barium sulfate and bismuth oxide and with a multifilament of 75 denier/36 filaments using a melt spinning process. The experimental results show that it was only possible to fabricate yarn up to a shielding material content of 5 wt%, and increasing the shielding material content reduced the tensile strength of the yarn. Therefore, further investigation of the melt spinning process and masterbatch manufacturing conditions are needed in future studies. Using the masterbatch for yarn production is one way to increase the content of the shielding material, and the multifilament structure during melt spinning process is used for the same purpose. The shielding performance of shielding fibers is ultimately determined by the content of shielding material and the process technology. The reproducibility of the shielding performance of the shielding fiber and maintenance of physical properties are very important considerations. Therefore, rather than simply investigating ways to increase the shielding material content, there is a need to research methods that can improve shielding performance through process technologies, such as weaving technology. Existing shielding fibers are manufactured by coating a fabric with a polymer composite--elastomer, rubber, and a mixture of tungsten, barium sulfate, and bismuth oxide. This method has the disadvantage of not imparting the inherent properties of the fibers to the fabric because of their low flexibility and high rigidity [37; 38; 39]. In addition, it is difficult to reproduce the shielding performance because the shielding performance must be controlled by adjusting the coating thickness during the process [40; 41].