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Title: Enhanced 99Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals

We present that technetium ( 99Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Because reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals, two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt samples at temperatures between 600 and 1000 °C. After being cooled, the solid glass specimens prepared at different temperatures at 600, 800, and 1000 °C were analyzed for Tc oxidation state using Tc K-edge XANES. In most samples, Tc was partially (<60%) oxidized from Tc(IV) to Tc(VII) as the melt temperature increased up to 600 °C. However, most of Tc(IV) was completely (>95%) oxidized to Tc(VII) at temperature above 800 °C. Tc retention in glass melt samples prepared using Tc-incorporated Fe minerals were slightly higher (~10%) than in glass prepared using KTcO4 because of limited and delayed Tc volatilization.
Authors:
 [1] ;  [2] ;  [2] ; ORCiD logo [2] ; ORCiD logo [2] ;  [2] ;  [2] ; ORCiD logo [3] ; ORCiD logo [4] ;  [5]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Pohang University of Science and Technology (POSTECH) (South Korea). Division of Advanced Nuclear Engineering (DANE), Division of Environmental Science and Engineering (DESE)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  5. United States Department of Energy, Office of River Protection, Richland, WA (United States)
Publication Date:
Report Number(s):
PNNL-SA-123344
Journal ID: ISSN 0022-3115; PII: S0022311517301198
Grant/Contract Number:
AC05-76RL01830; AC02-05CH11231; NRF-2015M2A7A1000191
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 495; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; Technetium; Tc-incorporated goethite; Tc-incorporated magnetite; Tc volatilization; Glass waste form; Tc retention in glass
OSTI Identifier:
1395273
Alternate Identifier(s):
OSTI ID: 1408487