The low- and intermediate-level radioactive waste liquid is a solution with high concentration of sodium nitrate (100–500 g/L). In order to immobilize the radioactive waste effectively, a certain content of sodium hydroxide (0.82–10%) would be added into the solidified fly ash-cement matrices as alkali activator. This study was aimed to investigate the coupling effect of sodium nitrate and sodium hydroxide on the reaction products, microstructure and leachability of solidified fly ash-cement matrices. The results indicated that a rather high content of sodium hydroxide (above 5%) was necessary for the crystallization of zeolite Na–P1 and sodium nitrate had participated in the formation of zeolite of chabazite and acted as a source of Na. Sodium hydroxide promoted the enhancement of pore structure and increased the compressive strength while sodium nitrate generated an opposite effect. The absorption performance for Cs⁺ was that: chabazite > zeolite Na–P1 > N-A-S-H gel. The cumulative leaching rate of Cs⁺ decreased with the increasing content of sodium hydroxide and the increasing concentration of sodium nitrate. However, on the contrary, an excessive amount of sodium nitrate (500 g/L) would accelerate the cumulative leaching rate of Cs⁺ because of the extreme degradation of the pore structure.

低级和中级放射性废液是一种高浓度硝酸钠（100-500 g / L）的溶液。为了有效地固定放射性废物，将一定量的氢氧化钠（0.82–10％）作为碱活化剂加入固化的粉煤灰水泥基质中。本研究旨在研究硝酸钠和氢氧化钠对固结粉煤灰水泥基体反应产物，微观结构和浸出性的耦合作用。结果表明，Na-P1沸石的结晶需要较高含量的氢氧化钠（高于5％），而硝酸钠参与了菱沸石的形成并成为Na的来源。氢氧化钠促进孔结构的增强并增加抗压强度，而硝酸钠产生相反的作用。Cs的吸收性能⁺是：菱沸石> Na-P1沸石> NASH凝胶。随着氢氧化钠含量的增加和硝酸钠浓度的增加，Cs ⁺的累积浸出率降低。但是，相反，由于孔结构的极度劣化，过量的硝酸钠（500 g / L）会加速Cs ⁺的累积浸出速率。