Investigation of fuel microstructure at the top of a metallic fuel pin after a reactor overpower transient

Lemma, Fidelma Giulia Di; Wright, Karen E.; Capriotti, Luca; Zabriskie, Adam; Winston, Alexander; Jensen, Colby; Wachs, Daniel M.

doi:10.1016/j.jnucmat.2020.152711

Cited by 14 publications

(6 citation statements)

References 22 publications

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“…The algorithm was developed mainly to remove the fragmentations at the top of the "fluff" (low fuel densities, colloquially) located at the top of the fuel pin in NRAD images. Details describing characterizations of the fluff can be found in [45], and an analysis on fluff formation can be found in [46]. Details of the irradiated fuel length interpretation process are given in ref.…”

Section: Specification Of Axial Fuel Length Measurementmentioning

confidence: 99%

Progress Report on SFR Metallic Fuel Data Qualification

Yacout

Billone

Kun

et al. 2022

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This report summarizes the progress of SFR metallic fuel qualification related activities, which are focused on providing quality assurance relevant information applicable to experiments irradiated during the Integral Fast Reactor (IFR) program. A background of metallic fuel performance data and the associated databases, including the EBR-II Fuels Irradiation & Physics Database (FIPD) and Out-of-Pile Transient Database (OPTD), is included. The legacy data in the databases, including as-built, post-irradiation examination (PIE), operating parameters, and out-of-pile experiment data are introduced. The SFR metallic fuel Quality Assurance Program Plan (QAPP) and its implementation to qualify these legacy data is described in detail. Important PIE data QA documents and the specifications of four types of PIE measurements (contact profilometry, laser profilometry, neutron radiography and gamma scan) are provided. Examples of the implementation of the QAPP to qualify each of those types of PIE data are provided.

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Section: Specification Of Axial Fuel Length Measurementmentioning

confidence: 99%

Progress Report on SFR Metallic Fuel Data Qualification

Yacout

Billone

Kun

et al. 2022

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“…The existence of a porous structure (previously referred to as fluff) at the top of metallic fuel pins used in Experimental Breeder Reactor II (EBR-II) has been well documented, and its properties were recently analyzed [11,12]. The post-irradiation examination using scanning electron microscopy, X-ray spectroscopy, and electron probe microanalyzer [11] revealed that the structure on top of the fuel pins contains the elements of ternary fuel (U, Pu, Zr), which are observed as regions of different porosity and oxidation [11]. The single pin examined in [11] was subjected to a moderate overpower.…”

Section: Introductionmentioning

confidence: 99%

“…The post-irradiation examination using scanning electron microscopy, X-ray spectroscopy, and electron probe microanalyzer [11] revealed that the structure on top of the fuel pins contains the elements of ternary fuel (U, Pu, Zr), which are observed as regions of different porosity and oxidation [11]. The single pin examined in [11] was subjected to a moderate overpower. However, the observed threemicrostructure redistribution behavior [13] for fuel regions is in line with the previous literature.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, rare earth precipitates were found in the porous structure. An important finding of the microstructural analysis was that the porous regions contained fuel with as-prefabricated elemental compositions in addition to expected fission products [11]. The porosity of the different fuel regions was thoroughly investigated, and it was found that lower porosity was present near the cladding and larger pores within the inner pin regions.…”

Section: Introductionmentioning

confidence: 99%

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Qualification and Quantification of Porosity at the Top of the Fuel Pins in Metallic Fuels Using Image Processing

Gribok,

Di Lemma,

Fay

et al. 2024

Energies

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Approximately 130,000 metal fuel pins were irradiated in the Experimental Breeder Reactor II (EBR-II) during its 30 years of operation to develop and characterize existing and prospective fuels. For many of the metal fuel irradiation experiments, neutron radiography imaging was performed to characterize fuel behavior, such as fuel axial expansion. While several fuel expansion results obtained from neutron radiography imaging have been published, the analysis of neutron radiography for the purpose of describing statistical properties of porous matter formed on top of the fuel pins, also referred to as fluff in previous publications, is significantly less represented in the literature with just a single paper so far. This study aims to validate and augment results reported in previous publications using automated image processing. The paper describes the statistical properties of the porous matter in terms of nine parameters derived from radiography images and correlates those parameters with such fuel properties as composition, expansion, temperature, and burnup. The reported results are based on 1097 fuel pins of eight different fuel compositions. For three major fuel types, U-10Zr, U-8Pu-10Zr, and U-19Pu-10Zr, a clear negative correlation is found between the Pu content and five parameters describing the amount of porous matter generated. The parameters describing granularity properties, however, showed either negative correlation or nonlinear dependency from fuel composition. The parameters describing the amount showed a positive correlation with fuel axial expansion, while granularity parameters showed a negative correlation with axial expansion. The dependency on cladding temperature was found to be weak. A positive correlation is demonstrated for volume parameters and fuel burnup. In general, reported results confirm and validate findings published in previous studies using a much larger number of pins and automated processing techniques, which easily lend themselves to reproducibility, thus avoiding subjective bias.

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“…9 Another unique feature of metallic fuels is the formation of fluff, a highly porous region at the top of the fuel pin [<40% theoretical density (TD)]. 10 This region comprises primarily fuel particulates and fission products, which can potentially impact the reactivity and source term during reactor operation or unexpected thermal transients. 10 The formation mechanisms behind fluff are not currently understood, but correlations have shown fluff increasing with burnup and forming more in U-Zr fuels compared to U-Pu-Zr metallic fuels.…”

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confidence: 99%

Uniaxial compressive creep tests by spark plasma sintering of 70% theoretical density α-uranium and U-10Zr

Fay,

Lemma,

Capriotti

et al. 2024

Journal of Applied Physics

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Metallic fuels hold numerous advantages over conventional uranium dioxide fuels and are a key component of several liquid metal-cooled advanced reactor concepts including sodium fast reactors. These fuels undergo rapid swelling during early burnup; consequently, they spend most of their reactor lifetime in a porous state. The presence of this porosity alters many of the mechanical properties of the fuel including creep impacting fuel deformation during axial swelling. This work investigates the creep behavior of the porous fuel using a spark plasma sintering technique. Creep tests were performed for the first time on porous α-phase uranium and uranium with 10 wt. % zirconium (U-10Zr) samples. The samples of α-phase uranium and U-10Zr were fabricated from depleted uranium by spark plasma sintering and subjected to uniaxial compressive creep testing. Calculated stress exponents were found to be 2.6±1.6 and 5.7±1.4 for α-U and U-10Zr, respectively, and calculated activation energies were found to be 61.6±1.1kJ/mol for α-U. The creep data were also used to evaluate existing porosity inclusive in creep models.

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Investigation of fuel microstructure at the top of a metallic fuel pin after a reactor overpower transient

Cited by 14 publications

References 22 publications

Progress Report on SFR Metallic Fuel Data Qualification

Progress Report on SFR Metallic Fuel Data Qualification

Qualification and Quantification of Porosity at the Top of the Fuel Pins in Metallic Fuels Using Image Processing

Uniaxial compressive creep tests by spark plasma sintering of 70% theoretical density α-uranium and U-10Zr

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