## 3 Results and Discussions
### Simulation of the Solidification of Radioactive Wastes Using SRC
#### 3.5.2. Leachability of Radionuclides Contained in Radioactive Wastes  
Based on the results of the maximum packing capacity of the SRC, the amounts of each waste used for the leachability tests were 30 wt% for coarse aggregates and 5 wt% for waste soil and metal waste. The leaching indices of each nuclide are given in Table 7, and all values met the acceptance level (6) for disposal. In the case of waste soil, the leaching indices decreased with increasing amounts of spiking, but satisfied the criterion. However, the  
Figure 10. The maximum packing capacities of SRC for the simulated radioactive wastes. (**a**) The case of coarse aggregate and waste soil and (**b**) the case of coarse aggregate and metal waste. Refer to the detailed experimental conditions in Table 4.  
leadability indices of waste soil and metal waste at high concentrations tended to increase dramatically, and it is speculated that they could not meet the disposal criterion if the concentration exceeded the levels of this study. Recently, there has been a lot of research to improve the adsorption of radioactive nuclides. [PERSON] et al. (2024) reported that zirconium phosphate(ZrP) is an excellent inorganic adsorbent for radioactive Cs ([PERSON] et al., 2023), and [PERSON] et al. (2023) revealed the predominant affinity of carboxyl-functionalized carbon nanotubes (cCNTs) for radioactive Co as well as their high thermal stability ([PERSON] et al., 2023). A comparison of the compressive strength of SRC during the curing period and after the leaching tests is shown in Figure 11. In the case of SRC containing waste soil, its compressive strength was found to be 4.2 MPa and met the standard after 28 days of curing, regardless of the type of nuclide. The case of metal waste showed an acceptable level of compressive strength (4.5 MPa) for all types of nuclides after 28 days of curing. In addition, it was confirmed that the compressive strength of SRC did not change after the 90-day leaching tests in all the cases. Consequently, the results indicated that SRC can be used to safely solidify a considerable amount of radioactive waste contaminated with different radionuclides.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & **Co** & **Cs** & **Sr** & **Co-1** & **Co-2** & **Co-3** & **Cs-1** & **Cs-2** & **Cs-3** & **Sr-1** & **Sr-2** & **Sr-3** \\ \hline Leachability index & 14.69 & 13.96 & 7.75 & 14.59 & 14.16 & 6.3 & 14.78 & 13.84 & 6.57 & 14.9 & 13.13 & 6.14 \\ \hline \hline \end{tabular} Refer to the experimental conditions in Table 5.  
\end{table}
Table 7: The leaching indices of each radionuclide.  
Figure 11: The comparison of the compressive strengths of SRC during the curing period and after leaching test. (**a**) The case of metal waste soaked in the solutions of Co, Cs, and Sr and the cases of waste soil spiked by (**b**) Co, (**c**) Cs, and (**d**) Sr. The numbers 1, 2, and 3 denote three different levels of concentration, which are 10 % lower than maximum adsorption capacity (MAC), equal to MAC, and 10% higher than MAC, respectively. Refer to the detailed experimental conditions in Table 5.