Precipitation separation and ceramic solidification method for divalent strontium and tetravalent uranium in radioactive waste liquid: Fid-Bau Portal

Precipitation separation and ceramic solidification method for divalent strontium and tetravalent uranium in radioactive waste liquid

ZHAO XIAOFENG / CHEN QINGGUO / TENG YUANCHENG / LI YUXIANG / WU LANG

Abstract

The invention discloses a precipitation separation and ceramic solidification method for radioactive waste liquid divalent strontium and tetravalent uranium, and relates to the field of treatment and disposal of radioactive waste liquid. U in the high-level liquid waste exists in the form of hexavalent uranyl (UO2 < 2 + >), the U4 < + > is prepared by hydrogenation catalytic reduction, and the difference between the ionic radius of the Sr < 2 + > and the ionic radius of the U4 < + > and the ionic radius of the Ln < 3 + > is large, so that CePO4.0.667 H2O bischoerite with higher nuclide containing capacity is selected as a separation precipitator for synchronously precipitating and enriching the Sr < 2 + > and the U4 < + >. UO2 (NO3) 2.6 H2O is selected as a raw material. The catalyst is prepared from cheap raw materials such as Sr (C2H3O2) 2, NH4H2PO4, Ce (NO3) 3.6 H2O and the like. By controlling the ion ratio of Sr < 2 + >: U < 4 + >, the reaction time, the temperature and the pH value, the bisporus solid solution precipitate which is good in crystal grain development and large in Sr < 2 + >/U < 4 + > solid solution amount is prepared. And by utilizing a discharge plasma solid-phase sintering technology, grain aggregation and adhesion occurring in the process of high-temperature dehydration and crystal transformation of the bischofite are avoided. In addition, the pressure sintering can promote the further growth of nanocrystals and promote the homogenization of U < 4 + > and Sr < 2 + > in the monazite ceramic solidified body, thereby realizing the one-step preparation of the monazite ceramic solidified body from the hydrophosphatiite solid solution.

本发明公开了放射性废液二价锶、四价铀的沉淀分离与陶瓷固化方法，涉及放射性废液的处理处置领域。高放废液中U以六价铀酰(UO22+)的形式存在，本发明采用加氢催化还原制备U4+，Sr2+和U4+的离子半径与Ln3+差异大，故选用对核素包容能力更强的CePO4·0.667H2O水磷铈石作为同步沉淀富集Sr2+和U4+的分离沉淀剂。选择UO2(NO3)2·6H2O。Sr(C2H3O2)2、NH4H2PO4、Ce(NO3)3·6H2O等廉价原料。通过控制Sr2+:U4+离子比、反应时间、温度、pH，制备晶粒发育良好、Sr2+/U4+固溶量大的水磷铈石固溶体沉淀。利用放电等离子固相烧结技术，避免水磷铈石高温脱水及晶型转变过程中出现的晶粒团聚粘结。另外，压力烧结可以促进纳米晶粒的进一步生长，促进U4+和Sr2+在独居石陶瓷固化体中均质化，实现水磷镧石固溶体一步法制备独居石陶瓷固化体。

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