| 摘要 |
In the consolidation of aq. radioactive waste contg. nitrate by evaporating the soln. to dryness in the presence of H3PO4 and converting the phosphates formed into a hardly soluble solid, the alkali phosphate residue (I) obtd. by evapn. is mixed with alkaline earth (hydr)oxide(s) (II) and then converted to hardly soluble alkali-alkaline earth phosphates at 500-950 deg.C. Pref. the molar ratio of nitrate to added H3PO4 is 2-3. (I) is pref. heated to 300-500 deg.C before adding (II). (II) is pref. MgO, CaO, Mg(OH)2 and/or Ca(OH)2, esp. dolomite, CaO and/or (esp.) MgO. Ca-H phosphate and opt. surface-active SiO2 powder can also be added before calcination, which is carried out at 650-850 deg.C, pref. after moulding the mixt. by pressing. The prod. is pref. embedded in a matrix resistant to lixiviation. The vol. of the end prod. is reduced, since the amt. of waste that can be incorporated is increased. The prod. has good compatibility with the usual binders and gives dry end prods.
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