The Effect of additive seed crystals method to control encrustation of zirconium molybdate hydrate

Sue, Kasumi*; Hirasawa, Izumi*; Miyazaki, Yasunori  ; Takeuchi, Masayuki 

In the dissolving process of spent nuclear fuel, poor water soluble substances precipitate and accumulate, which lead to lower heat transfer efficiency and pipe blockage. The major substance is known as zirconium molybdate dihydrate (ZMH). ZMH has characteristic properties; for example, water solubility decreases and adhesibility increases as the reaction temperature raises. This study revealed that encrustation of the metal wall vessel was prevented by adding ZMH crystal when compared to the case without ZMH addition. As the ZMH crystal was added, the reaction between Zr and Mo was accelerated that inhibits nucleation in the reaction solution.