Iron Oxide Waste Form for Stabilizing 99Tc

Journal Article · Sat Jun 09 00:00:00 EDT 2012 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2012.06.004· OSTI ID:1046920

Um, Wooyong; Chang, Hyun-Shik; Icenhower, Jonathan P; Lukens, Wayne W; Serne, R Jeffrey; Qafoku, Nikolla; Kukkadapu, Ravi K; Westsik, Joseph H

Crystals of goethite were synthesized with reduced technetium [{sup 99}Tc(IV)] incorporated within the solid lattice. The presence of {sup 99}Tc(IV) as a substituting cation in the matrix and 'armoring' by an additional layer of precipitated goethite isolated the reduced {sup 99}Tc(IV) from oxidizing agents. These products were used to make monolithic pellets to quantify an effective diffusion coefficient for {sup 99}Tc from goethite waste form contacted with a synthetic Hanford IDF (integrated disposal facility) pore water solution (pH = 7.2, I = 0.05 M) at room temperature for up to 120 days in static reactors. XANES analysis of the goethite solids recovered post-run demonstrated that the {sup 99}Tc in the goethite crystals remains in the reduced {sup 99}Tc(IV) state. The slow release of pertechnetate concentration with time in the static experiments with the monolith followed a square root of time dependence, consistent with diffusion control for {sup 99}Tc release. An apparent diffusion coefficient of 6.15 x 10{sup -11} cm{sup 2}/s was calculated for the {sup 99}Tc-goethite pellet sample and the corresponding leaching index (LI) was 10.2. The results of this study indicate that technetium can be immobilized in a stable, low-cost Fe oxide matrix that is easy to fabricate and these findings can be useful in designing long-term solutions for nuclear waste disposal.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1046920
• Report Number(s): PNNL-SA-86045; JNUMAM; 35405; EY4049110; TRN: US1203800
• Journal Information: Journal of Nuclear Materials, Vol. 429, Issue 1-3; ISSN 0022-3115
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AQUEOUS SOLUTIONS
CATIONS
DIFFUSION
GOETHITE
IRON OXIDES
LEACHING
OXIDES
OXIDIZERS
PELLETS
PERTECHNETATES
RADIOACTIVE WASTES
TECHNETIUM
TIME DEPENDENCE
WASTE FORMS
Technetium
goethite
waste form
effective diffusion
secondary wastes
Hanford Site
Environmental Molecular Sciences Laboratory