Phase Chemistry in Fluidized-Bed Steam Reformer Waste-Form Granules Containing Technetium and Iodine
EMSL Project ID
44895
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 large cages in 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; radioactive sample analysis will proceed only after a reasonable probability of success has been established. As a result of the importance of solving the LAW disposal issue, our project has top priority within the Office for Environmental Management (EM) of the USDOE, and we are scheduled to brief the Assistant Secretary for EM regarding our progress on 15 June 2011. Thus, while we have submitted a full EMSL Science Theme proposal and a general proposal to cover the full range of our efforts, here we request rapid access to allow work to begin on the first stage. This work will involve the use of micro-x-ray diffraction for major phase determination and for analysis of individual grains to determine phase purity. If such purity is seen for sodalite-group minerals, we will then analyze these grains by confocal Raman spectroscopy to seek confirmation of the presence of TcO4- (ReO4-), and I- in their structures.
Project Details
Project type
Limited Scope
Start Date
2011-05-09
End Date
2011-07-09
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members