a process for chemical fixation of radionuclides and radioactive compounds present in soils , solid materials , sludges and liquids . radionuclides and other radioactive compounds are converted to low - temperature apatite - group structural isomorphs 5 3 z ), usually phosphatic , that are insoluble , non - leachable , non - zeolitic , and ph stable by contacting with a suspension containing a sulfate , hydroxide , chloride , fluoride and / or silicate source and a phosphate anion . the apatitic - structure end product is chemically altered from the initial material and reduced in volume and mass . the end product can be void of free liquids and exhibits sufficiently high levels of thermal stability to be effective in the presence of heat generating nuclear reactions . the process occurs at ambient temperature and pressure .