Determination of the Rate of Formation of Hydroceramic Waste Forms made with INEEL Calcined Wastes

Abstract

iii Executive SummaryA "hydroceramic" nuclear waste form, developed especially to address the immobilization of the reprocessing wastes from the Idaho National Engineering and Environmental Laboratory, has been demonstrated to possess superior chemical and mechanincal properties. Furthermore, the processing requirements of hydroceramic waste forms are simple, less costly and offer greater safety to INEEL personnel than other waste form preparation systems.The objective of this research was two fold. The initial phase of the study was to systematically survey the suitability of readily available pozzolanic additions as raw materials for hydroceramic formulations in order to identify a source material that would be compatible with the established processing requirements for the waste form i.e., no excessive water demand, proper mineralogical composition of the waste form, low leachability, waste loadings greater than 20 weight percent calcine and also readily available to INEEL in large quantities once the pozzolan(s) selection was made. Pozzolanic materials are normally finely divided substances that contain either glassy or crystalline sources of silica that are chemically reactive enough to combine with lime and water at room temperature to form cementitious material. The primary objective of the research program was to establish the final processing parameters for the preparation of hydroceramic waste forms form INEEL wastes i.e., the rate at which hydroceramic is formed, the phases that formed and the optimum temperature needed to minimize leachability.A total of 20 pozzolanic materials were surveyed. These included a number of different fly ash sample, natural and thermally altered clays, reactive aluminas and even finely ground bottle glass. The survey resulted in the selection of a natural, thermally altered clay (metakaolinite) that has found extensive use in the manufacture of blended Portland cement and currently mined in Troy Idaho.A "host" matix formulation was initially developed using Troy metakaolinite and all processing parameters and chemical and mineralogical characterization was conducted on these samples. Once developed, the host matrix was used to subsequently prepare waste forms based on fluorinel and zirconia simulated calcines supplied by INEEL. A waste loading study was conducted in order to determine the maximum loading that could be sustained and still exibit the leaching characteristics and mechanical properties of the laboratory specimens. The "host" matrix samples and the two waste forms were processed at 75, 85, 95, 125, 150, 175 and 200 o C at 100% relative humidity for times often exceeding 500 hours. Two sets of mineralogy were observed for the "host" samples and "waste loaded" samples. The waste loading study optimized the hydroceramic waste form at 30% by weight for both fluorinel and zirconia waste calcines.The hydration rate studies conducted as a function of time and temperature determined that both the "host" matrix formulation and the fluorinel and zirconia waste loaded...

Accelerated Leach Testing of Glass (ALTGLASS): II. Mineralization of hydrogels by leachate strong bases

“…64,65 Zeolites also form when metakaolin (Al 2 O 3 Á2SiO 2 ) or amorphous/glassy fly ash (0.74Al 2 O 3 Á2.40SiO 2 ) is reacted with excess NaOH during geopolymerization [73][74][75] and/or during hydroceramic formation. [76][77][78][79][80] According to a compilation by Barrer, 55 the zeolite analcime has been made from aluminous glass plus Na 2 SiO 3 and NaOH at 180-190°C, from NaAlO 2 and Na 2 SiO 3 at 180°C, from kaolin and Na 2 SiO 3 at 200-220°C, and from Al 2 O 3 plus 3-4 moles SiO 2 and Na 2 CO 3 at 190-200°C. Zeolites from synthetic sodic rich glasses with variable SiO 2 /Al 2 O 3 or Na 2 O/Al 2 O 3 and natural analog glasses have been studied in excess NaOH and found to form Zeoite A, Na-P zeolite, analcime, basic sodalite and/or faujasite.…”

Inorganic Waste Forms for Efficient Immobilization of Radionuclides

“…Hydroceramics are zeolite-like crystalline materials synthesized from aluminosilicates (e.g., metakaolin, vermiculite, fly ash, and slag) via the hydrothermal method in alkaline conditions at a mild reaction temperature (80–200 °C). ,− Hydroceramics prepared using metakaolin have lower compressive strength (<5 MPa), which could be significantly improved up to 40 MPa by introducing slag in the synthesis mixture (Al/Si molar ratio is varied from 1 to 0.77 by the addition of slag from 0 to 50 wt %). ,,, …”

“…Scheetz et al − reported the rate of formation of hydroceramic waste forms with Idaho National Engineering and Environmental Laboratory (INEEL) calcined wastes. The authors investigated the synthesis, characterization, and hydration kinetics of hydroceramic waste forms as potential hosts for existing INEEL calcined HLW as functions of temperature and processing time.…”

“…74,114−117 Hydroceramics prepared using metakaolin have lower compressive strength (<5 MPa), 73 which could be significantly improved up to 40 MPa by introducing slag in the synthesis mixture (Al/Si molar ratio is varied from 1 to 0.77 by the addition of slag from 0 to 50 wt %). 68,69,118,119 Scheetz et al 116−118 reported the rate of formation of hydroceramic waste forms with Idaho National Engineering and Environmental Laboratory (INEEL) calcined wastes. The authors investigated the synthesis, characterization, and hydration kinetics of hydroceramic waste forms as potential hosts for existing INEEL calcined HLW as functions of temperature and processing time.…”

Radioactive waste (RAW) conditioning, immobilization, and encapsulation processes and technologies: overview and advances

“…[144,145] Hydroceramic wasteforms have been made with Idaho National Laboratory's HLW calcine. [146]…”