This study aimed to evaluate the long-term stability of glass wool used as insulation material in domestic nuclear power 

plants and to quantify its degradation mechanisms and dissolution kinetics under highly alkaline conditions (pH≥12) 

expected in cementitious environments associated with vault-type disposal systems for low-level radioactive waste. Experiments

were conducted at 20 °C and 80 °C using cement-saturated groundwater (CGW) as the primary solution, while 

comparative tests were performed in NaOH and Ca(OH)₂ solutions at equivalent pH levels. ICP-OES, SEM-EDS, and 

XRD analyses revealed that dissolved Ca²⁺ significantly suppressed glass dissolution. The presence of abundant Ca²⁺ ions 

promoted densification of the surface alteration layer, retarding degradation, whereas depletion of Ca²⁺ resulted in a rapid 

increase in the dissolution rate. Although calcium silicate hydrate (CSH) precipitates are generally known to inhibit glass 

corrosion, the CSH phases formed in this study exhibited limited protective capability due to their low Ca/Si ratios and 

high porosity. Based on the dissolution rate constant at 20 °C, the complete dissolution of glass wool was estimated to 

require approximately 213 years; however, under conditions of limited Ca²⁺ availability, the dissolution rate could increase 

by up to 70-fold, approaching that observed in NaOH solution.