Characterization of Highly Waste Loaded Glass for HLW
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CHARACTERIZATION OF HIGHLY WASTE LOADED GLASS FOR HLW
KAZUHIRO KAWAMURA AND JIN OHUCHI Power Reactor and Nuclear Fuel Development Corporation (PNC), Tokai -works, 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki-ken, 319-11, JAPAN
ABSTRACT Possibility of highly waste loaded borosilicate glasses up to 65wt% were investigated for HLW. In the case the waste was loaded at a content higher than 45wt%, apatite crystal was identified in the glasses. Adding above 2.5wt% of M0O3. yellow phase was observed in the 45wt% waste glass. In the case the composition of actual waste was simulated, waste(2545wt%) glasses were characterized. Chemical durability of 45wt% waste glass was equivalent to that of 25wt% waste glass under the condition of Na20 content lower than 12wt%. Rheological behavior of 45wt% waste glass was equivalent to that of 25wt% waste glass in the range of melting temperature. Electrical resistivity of 45wt% waste glass were a little lower than that of 25wt% waste glass and it depended on the noble metal content. The Time-TemperatureTransformation (T-T-T) diagram and the leach rate of heat treated glass indicated a good thermal stability of highly waste loaded glass below the glass transition temperature. Possibility of high waste loading up to 45wt% was elucidated.
INTRODUCTION There is an economic incentive to highly waste loaded glass for HLW. The relationship between the waste content and the properties had been investigated[I,2]. Typical waste glasses of PNC contain 25wt% waste oxide including lOwt% of Na20[l1. The waste loading rate is limited under 30wt% to keep chemical durability and to prevent soluble "Yellow Phase". Main constituent in the phase is molybdenum which is precipitated in fully radioactive HLW solution in the form of zirconium molybdate[3]. Separation of the precipitate from HLW solution is one of methods to avoid the phase. In this study, possibility of highly waste loading in the HLW glass with or without molybdenum and zirconium was investigated.
EXPERIMENTAL Glass preparation Waste composition was simulated on the basis of analytical value of real waste solution, and the content of molybdenum and zirconium were adjusted. Typical glass flit developed was used in this study. The glasses shown in Table I were prepared for three series of experiments. (])Maximum waste loading test Waste glasses without molybdenum and zirconium were melted at 11 50'C for 25-35wt% waste glasses and at I 100'C for 40-65wt% waste glasses for 2.5hours, respectively. The glasses were kept at 510Tc for 2hours after melting, then annealed at 16.7'C/h to room temperature.
Mat. Res. Soc. Symp. Proc. Vol. 353 0 1995 Materials Research Society
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(2)Maximum MoO3 loading test Waste(45wt%) glasses with M0O3(2, 2.5, 3wt%) and ZrO2(4.6-6.9 wt%) were melted at 1100°C for 2.5hours and annealed. The ratio between molybdenum and zirconium was determined by the composition of the precipitate in full active HLW.
Table I. Typical composition of prepared glasses
Components SiO2 B203 Li20 CaO ZnO A1203 Na2O P205 Fe203 NiO Cr
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