Abstract
The low level radioactive waste is generated in reprocessing steps of nuclear fuel cycle.
The technology which converts the sodium nitrate in the waste into sodium carbonate is developed for environmental loading reduction. It is requested to solidify low level radioactive waste solution containing Na2CO3. In this research, we discussed the reaction mechanism of blast furnace slag and fly ash Na2CO3 system, and solidification of Na2CO3.
In the case of using Na2CO3 as alkali activating agent the reaction of blast-furnace-slag was proceeded and solidified substance was obtained. On the other hand the reaction of fly ash was not proceeded.
And reaction mechanism of blast furnace slag-Na2CO3 system was also investigated.
Reaction ratio of blast furnace slag was about 50％ in a week. Hydrated products in this system was C-S-H, Calcite, gaylussite and AFm（CO3）.
Reaction rate of blast-furnace-slag was related to the existence of gaylussite.
The maximum replacement ratio of fly ash for blast furnace slag is 15％ for obtaining the solidified substance in a week. The reaction of blast furnace slag was retarded by replacement of fly ash.
The retardation mechanism of blast-furnace-slag reaction is due to the existence of gaylussite and reduction of CaO/SiO2 in C-S-H.
