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We have studied the water durability of ZrO 2 containing FeOFe 2 O 3 P 2 O 5 glasses for the immobilization of nuclear waste including Zr isotope. ZrP 2 O 7 crystals with 12 micrometer in diameter were precipitated in the glass matrix incorporated with ²1 mol % ZrO 2. The molecular structure of phosphate network including ZrP 2 O 7 precipitates was analyzed by micro-Raman spectroscopy. Formations of Q 1 and Q 0 phosphate units contributing to better water durability are ascribed to preferential precipitation of ZrP 2 O 7 crystals with Q 1 units and the compensation of phosphate component in residual glass matrix.

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This study is carried out to make the pyroprocessing hold a competitive advantage from the viewpoint of environmental load reduction and economical improvement. As one of the measures is to reduce the volume of the high-level radioactive waste, the phosphate conversion method is applied for removal of fission products from the melt as spent electrolyte in this paper. Though the removing target elements in the medium are alkali metals, alkaline earth metals and lanthanoid elements, only lanthanoid elements and lithium form the insoluble phosphates by reaction with Li3PO4 or K3PO4. Therefore, as the first step, the precipitation experiment was carried out to observe the behaviours of elements which form the insoluble precipitates as double salts other than simple salts. Then the filtration was experimented to remove lanthanoid precipitates in the spent electrolyte using Fe2O3-P2O5 glass system as a filtlation medium which is compatible material with the glassification. The result of separation of lanthanoid precipitates by filtration was effective and attained almost 100%.

The great amount of water used for cooling the stricken power reactors at Fukushima Dai-ichi following the earthquake and tsunami of 11 March 2011 has resulted in accumulation of cooling water so-called the remaining water in some buildings. As the cooling water is subsequently contaminated by fission products (FPs) and some other radioactive substances, it is necessary to decontaminate this ‘cooling water’ to reduce the volume of liquid radioactive waste and to reuse it again for cooling the affected reactors. Some methods are applied to remove the radioactive substances from the cooling water. However, after treatments of water, there arises a secondary radioactive waste, the sludge. Steps are now taken to immobilize this sludge. In this paper, BaSO4, as one of main constituents of the sludge, was chosen as an immobilizing target substance. The appropriate manufacturing condition of glass waste form for loading the sludge (BaSO4) was studied and the chemical durability was evaluated by measuring the dissolution rate. For this experiment, the iron phosphate glass (IPG), which is known to possess a large loading capacity for a variety of chemical substances, was employed as the glass medium. Based on experimental results, it is evident that BaSO4 can be loaded into the IPG medium when it possesses the appropriate composition and melting temperature. During loading, BaSO4 converted into BaO, acting as a network modifier, which leads to enhanced stability of IPG.