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Title: Getters for improved technetium containment in cementitious waste forms

A cementitious waste form, Cast Stone, is a possible candidate technology for the immobilization of low activity nuclear waste (LAW) at the Hanford site. This paper focuses on the addition of getter materials to Cast Stone that can sequester Tc from the LAW, and in turn, lower Tc release from the Cast Stone. Two getters which produce different products upon sequestering Tc from LAW were tested: Sn(II) apatite (Sn-A) that removes Tc as a Tc(IV)-oxide and potassium metal sulfide (KMS-2) that removes Tc as a Tc(IV)-sulfide species, allowing for a comparison of stability of the form of Tc upon entering the waste form. The Cast Stone with KMS-2 getter had the best performance with addition equivalent to ~0.08 wt% of the total waste form mass. The observed diffusion (D obs) of Tc decreased from 4.6 ± 0.2 × 10 -12 cm 2/s for Cast Stone that did not contain a getter to 5.4 ± 0.4 × 10 -13 cm 2/s for KMS-2 containing Cast Stone. Finally, it was found that Tc-sulfide species are more stable against re-oxidation within getter containing Cast Stone compared with Tc-oxide and is the origin of the decrease in Tc D obs when using the KMS-2.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Univ. of Arizona, Tucson, AZ (United States). College of Optical Sciences
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; AC02-76SF00515; AC06-76RL01830; P41EB002035
Type:
Accepted Manuscript
Journal Name:
Journal of Hazardous Materials
Additional Journal Information:
Journal Volume: 341; Journal ID: ISSN 0304-3894
Publisher:
Elsevier
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (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); USDOE Office of Environmental Management (EM); National Inst. of Health (NIH) (United States)
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; nuclear waste management; technetium; cementitious materials; waste forms; Hanford site; getters
OSTI Identifier:
1435098