Conditions Conducive to Forming Crystalline Uranyl Silicates in SRS Evaporators

OJI, LN

Savannah River Site (S.C.)

关键词: Evaporators;    Silicate Minerals;    Sodium Uranates;    Clarkeite;    Sodium;   

DOI  :  10.2172/823370
RP-ID  :  WSRC-TR-2003-00553, R0
RP-ID  :  AC09-96SR18500
RP-ID  :  823370

美国|英语

来源: UNT Digital Library

【 摘 要 】

The laboratory conditions under which synthetic uranyl silicates are made are almost identical to SRS evaporator conditions,with the exception of differences in sodium ion concentration. Synthetic uranyl silicates have been made only under low sodium ion concentration (less than 0.02 M), while attempts to synthesize uranyl silicates in this study in the presence of high sodium ion concentration (5.6 M), which are typical of SRS evaporators have proved unfruitful. In the presence of soluble silica and uranyl ion, uranyl silicates (sodium weeksite, sodium boltwoodite and uranophane) have been synthesized at moderately low to high pH in temperature ranges of 80-150 degrees C and at less than 0.02 M sodium ion ion concentration in the reaction mixtures. However, in the presence of high sodium ion concentration the main product distribution for the same soluble silica-uranium reaction mixture shifts towards the formation of clarkeite, a hydrated sodium uranate and not towards the formation of uranyl silicates. There is a threshold sodium ion concentration requirement above which uranyl silicates are not formed under laboratory conditions that are quite similar to SRS evaporator conditions. This threshold sodium ion concentration, which is yet to be determined, may be influenced by the sodium-to-uranium ratio in a reaction mixture.