A Comprehensive Study of the Solubility, Thermochemistry, Ion Exchange and Precipitation Kinetics of NO3 Cancrinite and No3 Sodalite

Jove-Colon, Carlos ; Navrotsky, Alexandra

Sandia National Laboratories

关键词: Sodium Nitrates;    Zeolites;    12 Management Of Radioactive Wastes, And Non-Radioactive Wastes From Nuclear Facilities;    Actinides;    Sodium Carbonates;   

DOI  :  10.2172/839384
RP-ID  :  EMSP-81959
RP-ID  :  FG07-01ER63298
RP-ID  :  839384

美国|英语

来源: UNT Digital Library

【 摘 要 】

The precipitation of aluminosilicate phases from caustic nuclear wastes has proven to be problematic in a number of processes including radionuclide separations (cementation of columns by aluminosilicate phases), tank emptying (aluminosilicate tank heels), and condensation of wastes in evaporators (aluminosilicate precipitates in the evaporators, providing nucleation sites for growth of critical masses of radioactive actinide salts). In a collaboration between SNL and UCD, we have investigated why and how these phases form, and which conditions favor the formation of which phases. These studies have involved synthesis and characterization of aluminosilicate phases formed using a variety of synthesis techniques, kinetics of precipitation, structural investigations of aluminosilicate phases, thermodynamic calculations of aluminosilicate solubility, calorimetric studies of aluminosilicate precipitation, and a limited investigation of radionuclide partitioning and ion exchange processes (involving typical tank fluid chemistries and these materials). The predominant phases that are observed in the aluminosilicate precipitates from basic tanks wastes (i.e. Hanford, Savannah River Site ''SRS'' wastes) are the salt enclathrated zeolites: sodium nitrate, sodium carbonate and sodium hydroxide sodalite and cancrinite. These phases precipitate readily from the high ionic strength, highly basic solutions at ambient temperatures as well as at elevated temperatures, with or without the presence of an external Al and Si source (both are contained in the waste solutions), and upon interactions with reactive soil components such as clays. This report focuses on the portion of the work performed at UC Davis by Professor Navrotsky's group.