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Title: Investigation of sol-gel feedstock additions and process variables on the density and microstructure of UN microspheres

Abstract

The kernel of fully ceramic microencapsulated (FCM) fuel requires a material with high fissile density. For that reason, among others, UN is the appropriate chemical state for low enriched U fuel. The UN kernels are spheres ~800 μm in diameter made using a sol-gel process. The effect of additives on the chemistry and density of the UN microspheres are investigated in this work. Gadolinium nitrate hexahydrate, Gd 2O 3, B, SiO 2 and SiC were incorporated into the sol-gel broth in varying concentrations. It was found that Gd can serve as both a sintering aid and burnable poison when added to the sol-gel broth as a Gd(NO 3) 36H 2O. However, even with the increased theoretical density of the UN microspheres, the U density was still too low for the FCM design that replaces UO 2 pellets in a commercial light water reactor. Silicon carbide and B were also successfully added but produced a lower density final product. Other sol-gel processing variables were investigated. In conclusion, the pour density of the sol-gel feedstock was found to influence the final converted UN kernel density.

Authors:
ORCiD logo [1]; ORCiD logo [1];  [2]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. X-Energy, LLC, Greenbelt, MD (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1545223
Alternate Identifier(s):
OSTI ID: 1547548
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 520; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

McMurray, Jake W., Hunt, Rodney Dale, Reif, Tyler J., Helmreich, Grant W., Silva, Chinthaka M., Seibert, Rachel L., Gerczak, Tyler J., and Terrani, Kurt A. Investigation of sol-gel feedstock additions and process variables on the density and microstructure of UN microspheres. United States: N. p., 2019. Web. doi:10.1016/j.jnucmat.2019.04.003.
McMurray, Jake W., Hunt, Rodney Dale, Reif, Tyler J., Helmreich, Grant W., Silva, Chinthaka M., Seibert, Rachel L., Gerczak, Tyler J., & Terrani, Kurt A. Investigation of sol-gel feedstock additions and process variables on the density and microstructure of UN microspheres. United States. doi:10.1016/j.jnucmat.2019.04.003.
McMurray, Jake W., Hunt, Rodney Dale, Reif, Tyler J., Helmreich, Grant W., Silva, Chinthaka M., Seibert, Rachel L., Gerczak, Tyler J., and Terrani, Kurt A. Fri . "Investigation of sol-gel feedstock additions and process variables on the density and microstructure of UN microspheres". United States. doi:10.1016/j.jnucmat.2019.04.003.
@article{osti_1545223,
title = {Investigation of sol-gel feedstock additions and process variables on the density and microstructure of UN microspheres},
author = {McMurray, Jake W. and Hunt, Rodney Dale and Reif, Tyler J. and Helmreich, Grant W. and Silva, Chinthaka M. and Seibert, Rachel L. and Gerczak, Tyler J. and Terrani, Kurt A.},
abstractNote = {The kernel of fully ceramic microencapsulated (FCM) fuel requires a material with high fissile density. For that reason, among others, UN is the appropriate chemical state for low enriched U fuel. The UN kernels are spheres ~800 μm in diameter made using a sol-gel process. The effect of additives on the chemistry and density of the UN microspheres are investigated in this work. Gadolinium nitrate hexahydrate, Gd2O3, B, SiO2 and SiC were incorporated into the sol-gel broth in varying concentrations. It was found that Gd can serve as both a sintering aid and burnable poison when added to the sol-gel broth as a Gd(NO3)36H2O. However, even with the increased theoretical density of the UN microspheres, the U density was still too low for the FCM design that replaces UO2 pellets in a commercial light water reactor. Silicon carbide and B were also successfully added but produced a lower density final product. Other sol-gel processing variables were investigated. In conclusion, the pour density of the sol-gel feedstock was found to influence the final converted UN kernel density.},
doi = {10.1016/j.jnucmat.2019.04.003},
journal = {Journal of Nuclear Materials},
number = C,
volume = 520,
place = {United States},
year = {2019},
month = {4}
}

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