Materials and methods of making low-
sintering-temperature glass waste forms that sequester 
radioactive iodine in a strong and durable structure. First, the 
iodine is captured by an adsorbant, which forms an 
iodine-loaded material, e.g., AgI, AgI-
zeolite, AgI-
mordenite, Ag-silica 
aerogel, ZnI2, CuI, or Bi5O7I. Next, particles of the 
iodine-loaded material are mixed with powdered frits of low-
sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, 
ranging from 425° C. to 550° C. The 
sintering converts the mixed powders into a 
solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500° C. (below the 
silver iodide sublimation temperature of 500° C.) was identified that contains oxides of 
boron, 
bismuth, and 
zinc, while containing essentially no lead or 
silicon.