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Title: Selection of Nuclear Fuel for TREAT: UO2 vs U3O8

The Transient Reactor Test (TREAT) that resides at the Materials and Fuels Complex (MFC) at Idaho National Laboratory (INL), first achieved criticality in 1959, and successfully performed many transient tests on nuclear fuel until 1994 when its operations were suspended. Resumption of operations at TREAT was approved in February 2014 to meet the U.S. Department of Energy (DOE) Office of Nuclear Energy’s objectives in transient testing of nuclear fuels. The National Nuclear Security Administration’s is converting TREAT from its existing highly enriched uranium (HEU) core to a new core containing low enriched uranium (LEU) (i.e., U-235< 20% by weight). The TREAT Conversion project is currently progressing with conceptual design phase activities. Dimensional stability of the fuel element assemblies, predictable fuel can oxidation and sufficient heat conductivity by the fuel blocks are some of the critical performance requirements of the new LEU fuel. Furthermore, to enable the design team to design fuel block and can specifications, it is amongst the objectives to evaluate TREAT LEU fuel and cladding material’s chemical interaction. This information is important to understand the viability of Zr-based alloys and fuel characteristics for the fabrication of the TREAT LEU fuel and cladding. Also, it is very important tomore » make the right decision on what type of nuclear fuel will be used at TREAT. In particular, one has to consider different oxides of uranium, and most importantly, UO2 vs U3O8. In this report, the results are documented pertaining to the choice mentioned above (UO2 vs U3O8). The conclusion in favor of using UO2 was made based on the analysis of historical data, up-to-date literature, and self-consistent calculations of phase equilibria and thermodynamic properties in the U-O and U-O-C systems. The report is organized as follows. First, the criteria that were used to make the choice are analyzed. Secondly, existing historical data and current literature were reviewed. This analysis was supplemented by the construction and examination of the U-O and U-O-C phase diagrams at pressure close to negligent, thereby mimicking the conditions in which nuclear fuel is supposed to function inside the zirconium-based cladding in the reactor. Finally, our conclusion in favor of the UO2 down selection was summarized and explained in the last Section of this document.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
1260461
Report Number(s):
INL/EXT--16-37972
TRN: US1601556
DOE Contract Number:
AC07-05ID14517
Resource Type:
Technical Report
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; URANIUM DIOXIDE; URANIUM OXIDES U3O8; HIGHLY ENRICHED URANIUM; NUCLEAR FUELS; PHASE DIAGRAMS; URANIUM 235; ZIRCONIUM; DESIGN; TRANSIENTS; REACTOR CORES; SLIGHTLY ENRICHED URANIUM, THERMODYNAMIC PROPERTIES; OXIDATION; FUEL CANS; ZIRCONIUM BASE ALLOYS; CONVERSION; FABRICATION; FUEL-CLADDING INTERACTIONS; PERFORMANCE; STABILITY; FUEL ELEMENTS; TESTING; TREAT REACTOR; THERMAL CONDUCTIVITY Nuclear Fuel; TREAT; UO2