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Title: Characterization of slag and metal from uranium bomb reduction: Morphology, speciation, and the search for thorium

Abstract

Metallic uranium is an important material for many applications, especially nuclear energy for low enriched metallic fuel forms and new reactor concepts. Due to the its high electropositivity, production pathways to the metallic form are limited. One of the historically most common synthesis routes involves the heating of a uranium (IV) halide, in this study UF 4, with a highly electropositive metal like calcium. This synthesis is referred to as “bomb reduction” due to the temperatures and pressures released by the resulting exothermic reaction. This synthesis route is important for production, but it has also been shown to separate a decay product, thorium, from the parent uranium. This fractionation could be important for purification, but also presents the opportunity for radiochronometric dating of the reduction date. Unfortunately, little characterization has been performed on the products of this reaction. The present study performed bomb reduction on ~10 g of thorium-doped (2000 ppm) UF 4 followed by scanning electron microscopy and energy dispersive spectroscopy. This characterization revealed morphological features of the metal product and slag, the latter of which displayed a wide range of features that indicates a complex reaction in which many variables are involved. Initial characterizations also identified thorium-rich particles,more » which were extracted and analyzed via transmission electron microscopy and atom probe tomography. These characterizations identified a new thorium-bearing phase, Al 9-xFe 7-xTh 2Si <1, and also indicated thorium fractionation from uranium via at least four mechanistic pathways.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1570014
Alternate Identifier(s):
OSTI ID: 1574882
Report Number(s):
PNNL-SA-144324
Journal ID: ISSN 1044-5803
Grant/Contract Number:  
AC05-76RL01830; AC06-76RL01830
Resource Type:
Published Article
Journal Name:
Materials Characterization
Additional Journal Information:
Journal Volume: 158; Journal Issue: C; Journal ID: ISSN 1044-5803
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; uranium; thorium; bomb reduction; radiochronometry; slag; transmission electron microscopy; scanning electron microscopy; atom probe tomography

Citation Formats

Reilly, Dallas, Athon, Matthew T., Kovarik, Libor, and Lach, Timothy G. Characterization of slag and metal from uranium bomb reduction: Morphology, speciation, and the search for thorium. United States: N. p., 2019. Web. doi:10.1016/j.matchar.2019.109948.
Reilly, Dallas, Athon, Matthew T., Kovarik, Libor, & Lach, Timothy G. Characterization of slag and metal from uranium bomb reduction: Morphology, speciation, and the search for thorium. United States. doi:10.1016/j.matchar.2019.109948.
Reilly, Dallas, Athon, Matthew T., Kovarik, Libor, and Lach, Timothy G. Thu . "Characterization of slag and metal from uranium bomb reduction: Morphology, speciation, and the search for thorium". United States. doi:10.1016/j.matchar.2019.109948.
@article{osti_1570014,
title = {Characterization of slag and metal from uranium bomb reduction: Morphology, speciation, and the search for thorium},
author = {Reilly, Dallas and Athon, Matthew T. and Kovarik, Libor and Lach, Timothy G.},
abstractNote = {Metallic uranium is an important material for many applications, especially nuclear energy for low enriched metallic fuel forms and new reactor concepts. Due to the its high electropositivity, production pathways to the metallic form are limited. One of the historically most common synthesis routes involves the heating of a uranium (IV) halide, in this study UF4, with a highly electropositive metal like calcium. This synthesis is referred to as “bomb reduction” due to the temperatures and pressures released by the resulting exothermic reaction. This synthesis route is important for production, but it has also been shown to separate a decay product, thorium, from the parent uranium. This fractionation could be important for purification, but also presents the opportunity for radiochronometric dating of the reduction date. Unfortunately, little characterization has been performed on the products of this reaction. The present study performed bomb reduction on ~10 g of thorium-doped (2000 ppm) UF4 followed by scanning electron microscopy and energy dispersive spectroscopy. This characterization revealed morphological features of the metal product and slag, the latter of which displayed a wide range of features that indicates a complex reaction in which many variables are involved. Initial characterizations also identified thorium-rich particles, which were extracted and analyzed via transmission electron microscopy and atom probe tomography. These characterizations identified a new thorium-bearing phase, Al9-xFe7-xTh2Si<1, and also indicated thorium fractionation from uranium via at least four mechanistic pathways.},
doi = {10.1016/j.matchar.2019.109948},
journal = {Materials Characterization},
number = C,
volume = 158,
place = {United States},
year = {2019},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1016/j.matchar.2019.109948

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