| With the development of economy and the progress of the society, humans haveincreasing demand for energy, nuclear energy as a clean energy, effectively relievedthe energy crisis of the world, while also produced a large amount of nuclear wastes,which caused a certain pressure on the environment. Cement solidificationtechnology is a common management approach for radioactive wastes, which waseasy to implement, small investment, high curing efficiency, etc. The traditionalcement solidification method often exists water-cement ratio too large, the solidifiedbody not dense; resin containing capacity small, solidified body expandingobviously; high hydration heat which was bad for big volume casting solidificationbody, and Other impurity ions in waste resin affecting cement performance suchproblems.The paper studied alkali slag cement adding some additive in order to optimizea solidification formulation and process, for big volume solidifying simulation L-Mradioactive waste resin containing boron, and meeting the requirements of theconstruction and solidified body’s performance stability. The solidificationmechanism of Cs+ions was also researched. This research provided a theoreticalbasis for dealing with radioactive waste in practical engineering.The major work and conclusions of this paper listed as followed:1. Researches on alkali slag cement slurry propertiesThe setting time of alkali slag cement differed from motivation agent types anddosage, it came to decrease with the increasing dosage of sodium hydroxide orsodium silicate water glass, and also diminished with the increasing modulus ofwater glass. Zeolite powder could significantly increase water consumption, and thebest dosage was10%,20%zeolite powder had less damage on compressive strengthof alkali slag cement. KH-5water reducing agent had no effect on the fluidity ofalkali slag cement, NS water reducing agent should be limited in10‰, when thedosage was4‰-8‰, the fluidity growed quickly, over the range was not good.Through the preliminary optimization, we select modulus1.4,6%dosage of sodiumsilicate water glass as motivation agent,20%zeolite powder,10‰NS waterreducing agent as curing matrix material formulation. 2. Researches on solidification formulation and process for big volumesolidifying simulation L-M radioactive waste resin containing boronTo meet the performance of solidified body which demanded byGB14569.1-2011, we optimized a solidification formulation: sodium silicate waterglass (glass modulus was1.4, and dosage was6%),20%zeolite powder, watercement ratio of0.42,5‰dosage of water reducing agent, resin coating capacity60%(mass ratio), silica fume5%to8%. Sodium silicate water glass (glass modulusis1.4, dosage of6%), zeolite powder20%, water cement ratio of0.42,5‰dosageof NS water reducing agent,60%resin (mass ratio), lime0-5%. From theperspective of setting time and fluidity, mixing in storage barrel was more suitablefor for big volume solidifying simulation L-M radioactive waste resin containingboron, but retarder must be used to adjust the setting time.3. Researches on the solidification mechanism of Cs+ions in alkali slagcementTaking ions solution, ions adsorption and physical package by the solidifiedbody into account, the solidification mechanism of Cs+ions were studied by usingXRD, SEM-EDS and mercury injection test. Zeolite powder was the mostprominent factor for reducing the leaching rate of Cs+ions, secondly, the density ofthe solidified body structure can effectively retain Cs+ions, appropriate dosage ofsilica fume could not only improve the chemical curing effect of Cs+ion, but alsocould improve the density of the solidified body, therefore reduced harmful pore inthe solidified body which might also reducing the leaching rate of Cs+ions. |
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