DEVELOPMENT OF STABLE SOLIDIFICATION PROCESS OF PHOSPHATES WASTE FORM FOR ALPS SLURRY WASTES

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Over 10,000 m3 of slurry wastes were generated from Multinuclide Removal Facility (ALPS) since the accident. Simulated carbonate slurry was composed of CaCO3, Mg(OH)2 and NaCl and iron coprecipitation slurry was mainly composed of FeOOH and NaCl with SrCO3 and CsCl. To convert phosphates, simulated slurry was dissolved. FeOOH was dissolved in 2 M-HCl and ascorbic acid, and the other compounds were dissolved by adding HCl up to 3.5 M. Na2HPO4 was added to the solution. 4.8 M of NaOH solution was added to neutralize, and precipitation includes NaCl was obtained. When ratio of cation to phosphate (C/P) is less than 2, Sr and Ca in the filtrate were less than 0.01 %. It was rinsed by water to remove NaCl. Total amount of Sr and Ca were less than 0.1 %, Mg and Fe were less than 1.0 %. The rinsed precipitation was heated from 400 to 600 ºC. Heated precipitation at 600 ºC was crystalized and others were still amorphous. The heated precipitation was hot-pressed at 127 MPa with 300 ºC. The pellet was evaluated leachability based on ANSI/ANS 16.1. It was suggested leachability of the pellet on the condition ≤ 500 ºC and C/P = 1.4 was especially quite low. Although Cs wasn’t contained in phosphates, but over 99 % of Cs can be removed from dissolve solution by chabazite and CST. The solidification process from ALPS slurry was made by acid dissolution and Cs adsorption step, conversion and precipitation, rinsing, heating and hot press. This solidification waste was confirmed quite low leachability.