Ceramics for high level radioactive waste solidification

Abstract

Several countries reprocess their nuclear spent fuel using the Purex process to recover U and Pu as MOX fuel. The high level radioactive waste (HLW) produced during this reprocessing is a complex mixture containing both radioactive (fission products, minor actinides) and non-radioactive elements. Since HLW shows high rate heat release and contains some long half-life and biologically toxic radionuclide, its treatment and disposal technology is complex, difficult and high cost. HLW treatment and disposal become a worldwide challenge and research focus. In order to minimize the potential long-term impact of HLW, studies on enhanced chemical separation processes of long-lived radionuclides are in progress. Two options are then envisaged for these separated radionuclides: (a) transmutation into short-lived or non-radioactive elements, (b) immobilization in highly durable ceramic matrix instead of borosilicate glass. In this paper, we briefly review the composition, structure, processing and product properties of some ceramic candidates for inert matrix fuels (IMF) and the immobilization of high level radioactive waste.

Synthesis and Thermal Behavior of Nanopowders in LaPO4-YPO4(-H2O), LaPO4-LuPO4(-H2O) and YPO4-ScPO4(-H2O) Systems for Ceramic Matrices

“…Leaching experiments exhibit quite good resistance of Ln' 1-x Ln" x PO 4 matrices in a strongly acid HNO 3 solution (pH 1-2) at room temperature (Figure 8 & 9). The results of leaching experiments for Ln' 1-x Ln" x PO 4 are close to [20] for GdPO 4 in strongly HCl and HNO 3 solutions (pH 1-2) corresponding to value of ~10 -2 g L -1…”

“…In many previous works, the monazite-type lanthanum orthophosphate (LaPO 4 ), and xenotime one (YPO 4 ) has been suggested as matrices for radioactive waste immobilization (radioactive rare earth elements or trivalent actinides) and sensors [1][2][3][4][5][6][7][8]. Nanopowder-based ceramics designed for immobilizing purpose should possess high chemical resistance and isomorphic capacity, high durability and thermal stability.…”

“…Nanopowder-based ceramics designed for immobilizing purpose should possess high chemical resistance and isomorphic capacity, high durability and thermal stability. It is supposed to use ceramics obtained by sintering nanopowders with general formula Ln' 1-x Ln" x PO 4 The DSC/TG measurements were conducted in STA 449C (NETZSCH) calorimeter; sample mass was about 30 mg; heating rate was 20 °C/min. Preliminary calcined at 850 °C for 2 h nanopowders were compacted into tablets under a pressure of 8-10 MPa and then stepwise heated in air at 1000, 1200, 1600 and 1700 °C to obtain ceramic samples (matrices).…”

“…Yttrium, lutetium and scandium orthophosphates, hydrated and dehydrated, crystallizes in tetragonal xenotime-type form [9,10]. In this instance it was expected formation of limited solid solutions in the LaPO 4 -YPO 4 (-H 2 O) and LaPO 4 -LuPO 4 (-H 2 O) systems [9] and unlimited solid solutions in the YPO 4 -ScPO 4 (-H 2 O) system [10].…”

Response of strontium titanate to electron irradiation for the immobilization of strontium

“…As a result, radionuclides are easy to escape from glass forms. In recent years, many results showed that ceramic forms exhibit superior long-term stability, radiation tolerance and leaching resistance to glass forms, and most actinides and fission products can be incorporated into polycrystalline phases [3][4][5]. Perovskite phases, particularly SrTiO 3 , are good host phases for the immobilization of actinides and some long-lived fission products [6,7].…”