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Title: Detecting the Extent of Eutectoid Transformation in U-10Mo

Abstract

During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U 2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloy as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based onmore » our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the α/γ interface.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [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
OSTI Identifier:
1340892
Report Number(s):
PNNL-SA-120714
DN3001010; TRN: US1701827
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; DENSITY; EUTECTOIDS; CONCENTRATION RATIO; NUCLEAR FUELS; PHASE TRANSFORMATIONS; IRRADIATION; PERFORMANCE

Citation Formats

Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, and Lavender, Curt A. Detecting the Extent of Eutectoid Transformation in U-10Mo. United States: N. p., 2016. Web. doi:10.2172/1340892.
Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, & Lavender, Curt A. Detecting the Extent of Eutectoid Transformation in U-10Mo. United States. doi:10.2172/1340892.
Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, and Lavender, Curt A. Wed . "Detecting the Extent of Eutectoid Transformation in U-10Mo". United States. doi:10.2172/1340892. https://www.osti.gov/servlets/purl/1340892.
@article{osti_1340892,
title = {Detecting the Extent of Eutectoid Transformation in U-10Mo},
author = {Devaraj, Arun and Jana, Saumyadeep and McInnis, Colleen A. and Lombardo, Nicholas J. and Joshi, Vineet V. and Sweet, Lucas E. and Manandhar, Sandeep and Lavender, Curt A.},
abstractNote = {During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloy as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based on our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the α/γ interface.},
doi = {10.2172/1340892},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Aug 31 00:00:00 EDT 2016},
month = {Wed Aug 31 00:00:00 EDT 2016}
}

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