## 3 Results and Discussion
### Hydrolytic Resistance of the Materials  
The obtained data on the differential leaching rate of waste components from MPP-Z compound samples, including after heat treatment up to 450 \({}^{\circ}\)C, are shown in Figure 7. The leaching rates of Sr, La and Ba reduced by two orders of magnitude after the thermal treatment of the compound at 450 \({}^{\circ}\)C and equal to 1.6 \(\times\) 10\({}^{-7}\), 3.0 \(\times\) 10\({}^{-7}\) and 2.3 \(\times\) 10\({}^{-6}\) g/(cm\({}^{2}\cdot\)day), respectively, at 28 th days of contact with water (Figure 7a). The differential leaching rate of \({}^{137}\)Cs and \({}^{152}\)Eu (Figure 7b,c, respectively) from all samples under study on the 28 th day of contact of the samples with water was about 10\({}^{-5}\) g/(cm\({}^{2}\cdot\)day), and \({}^{239}\)Pu (Figure 7d) was about 10\({}^{-6}\) g/(cm\({}^{2}\cdot\)day), which is close to the normative requirements for vitrified HLW (no more than 1.0 \(\times\) 10\({}^{-5}\) g/(cm\({}^{2}\cdot\)day) for \({}^{137}\)Cs and 1.0 \(\times\) 10\({}^{-7}\) g/(cm\({}^{2}\cdot\)day) for \({}^{239}\)Pu) [26]. The heat treatment up to 450 \({}^{\circ}\)C of the compounds does not lead to a significant change in leaching rate. The kinetic dependences of sodium leaching rate from NAFP glass are presented in Figure 8a. It should be noted that there are no normative requirements for sodium leaching rate from solidified HLW, but due to the similarity of chemical behavior of sodium and cesium, it is possible to be oriented on norms for cesium: \({}^{137}\)Cs leaching rate from glass-like compounds should not exceed 10\({}^{-5}\) g/(cm\({}^{2}\cdot\)day) [26]. The data in Figure 8a show that the differential sodium leaching rate is about 10\({}^{-6}\) g/(cm\({}^{2}\cdot\)day), which meets the normative requirements, including after the glass heat treatment at 450 \({}^{\circ}\)C. It was found that the \({}^{137}\)Cs and \({}^{152}\)Eu contents in the solutions after leaching of NAFP samples were below detection limits, indicating high water resistance of NAFP glass to leaching of the most mobile nuclides. The differential leaching rate of \({}^{239}\)Pu from NAFP glass upon sample leaching at 25 \({}^{\circ}\)C on the 7 th day of contact with water is no more than 4.8 \(\times\) 10\({}^{-8}\) g/(cm\({}^{2}\cdot\)day) and the content of \({}^{239}\)Pu in solutions during the test was below the detection limits. At the same time, the leaching of \({}^{239}\)Pu from glass samples at 90 \({}^{\circ}\)C is observed, so the differential leaching rate from NAFP glass after heat treatment at 450 \({}^{\circ}\)C is higher than that from the original glass samples (Figure 8b). It is likely that the increased leaching of \({}^{239}\)Pu is due to its leaching from the formed modified surface layer (Figure 4). At the same time, the leaching rate of \({}^{239}\)Pu decreases to 4.7 \(\times\) 10\({}^{-7}\) g/(cm\({}^{2}\cdot\)day) on the 28 th day of water contact after the sample was exposed to heat treatment at 450 \({}^{\circ}\)C, which is close to the normative requirements for vitrified HLW (no more than 10\({}^{-7}\) g/(cm\({}^{2}\cdot\)day)) [26] and is likely to reach the required value when the tests continue. Figure 6: X-ray diffraction patterns of the ceramics based on bentonite clay, including after irradiation up to 10\({}^{9}\) Gy. Figure 8: Kinetic curve of the leaching rate of (**a**) sodium and (**b**) plutonium from NAFP glass. Figure 7: Kinetic curve of the leaching rate of (**a**) of the solidifying waste imitator components (**b**) \({}^{137}\)Cs, (**c**)\({}^{152}\)Eu and (**d**) \({}^{239}\)Pu from MPP-Z compound, including after its heat treatment. Figure 9 shows the kinetic curves of the differential leaching rate of components from ceramic samples based on bentonite clay. The leaching rate of cesium, as one of the main components of waste, from the samples is about 3 \(\times\) 10\({}^{-5}\) g/(cm\({}^{2}\cdot\)day), which is close to the regulatory requirements for immobilized HLW [26].