Molecular-Scale Assessment of Technetium and Iodine Phase Chemistry in Fluidized Bed Steam Reformer Waste Form
EMSL Project ID
44746
Abstract
Technetium (99Tc) and radioactive iodine (129I) are long-lived fission products found in nuclear waste. Their abundance coupled with their long half-lives and aqueous mobility, make them the two contaminants of greatest concern in low-activity-waste (LAW) disposal scenarios at the Hanford Site. This project focuses on characterizing an alternative waste form for LAW and secondary waste containing these radionuclides made by the process of fluidized bed steam reformation (FBSR). The FBSR process involves the formation of an aluminosilicate mineral matrix that is believed to incorporate anionic forms of Tc and I into its structure. However, due to the redox conditions during the process there is some uncertainty as to whether Tc remains oxidized and anionic or is reduced and consequently forms an amorphous phase separate from the aluminosilicate matrix. Work to date has not taken a rigorous approach to this question, particularly at the molecular scale. The major questions to be addressed are what mineral forms are present in the FBSR waste, in what forms are the Tc and I located and how are these forms distributed throughout the FBSR waste form. We have a total of 12 samples, 4 of which are nonradioactive (using Re as a substitute for Tc), for possible analysis. Most of our work will start with the nonradioactive samples, with radioactive sample analysis occurring only after probable success has been established. We will address these questions by the use of micro-x-ray diffraction for major phase determination. EPR spectroscopy and possibly XPS and laser fluorescence spectroscopy will be used to assess the oxidation states of Tc (Re). FIB-SEM and TOF-SIMS will be used to assess the distribution of Tc (Re) and I in the samples.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2011-10-01
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Neeway JJ, N Qafoku, BD Williams, KA Rod, ME Bowden, CF Brown, and EM Pierce. 2014. "Performance of the Fluidized Bed Steam Reforming Product Under Hydraulically Unsaturated Conditions." Journal of Environmental Radioactivity 131:119-128. doi:10.1016/j.jenvrad.2013.10.008