Stabilization/Solidification of radioactive molten salt waste via gel-route pretreatment.
The volatilization of radionuclides during the stabilization/solidification of radioactive wastes at high temperatures is one of the major problems to be considered in choosing suitable wasteforms, process, material systems, etc. This paper reports a novel method to convert volatile wastes into nonvolatile compounds via a sol-gel process, which is different from the conventional method using metal-alkoxides and organic solvents. The material system was designed with sodium silicate (Si) as a gelling agent, phosphoric acid (P) as a catalyst/stabilizer, aluminum nitrate (Al) as a property promoter, and H20 as a solvent. A novel structural model for the chemical conversion of molten salt waste, named RPRM (Reaction Product in Reaction Module), was established, and the waste could be solidified with glass matrix via a simple procedure. The leached fraction of Cs and Sr by a PCT leaching method was 0.72% and 0.014%, respectively. In conclusion, the RPRM model isto converttargetwastes into stable and manageable products, not to obtain a specific crystalline product for each radionuclide. This paper suggested a new stabilization/solidification method for salt wastes by establishing the gel-forming material system and showing a practical example, not a new synthesis method of stable crystalline phase. This process, named "gel-route stabilization/solidification (GRSS)", will be a prospective alternative with stable chemical process on the immobilization of salt wastes and various mixed radioactive waste for final disposal.
Park
Hwan-Seo
HS
Nuclear Fuel Cycle R&D Group, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong-gu, Daejeon, 305-353, Korea. hspark72@kaeri.re.kr
Kim
In-Tae
IT
Kim
Hwan-Young
HY
Ryu
Seung-Kon
SK
Kim
Joon-Hyung
JH
D017607:Aluminum Compounds / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D005782:Gels; D009566:Nitrates / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry; D011850:Radioactive Waste; D012037:Refuse Disposal / Q000379:methods*; D017640:Silicates / Q000737:chemistry
D017607:Aluminum Compounds; D002712:Chlorides; D005782:Gels; D009566:Nitrates; D010756:Phosphoric Acids; D011850:Radioactive Waste; D017640:Silicates; C030242:phosphoric acid; C050609:aluminum nitrate; C005691:sodium silicate