scholarly journals Effects of the Foil Centering on the Irradiation Performance of U10Mo Alloy Based Monolithic Mini-Plates

2015 ◽  
Author(s):  
Jill Wright ◽  
Hakan Ozaltun
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
Foil Thickness ◽  
Operational Variables ◽  
Total Magnitude ◽  
Irradiation Performance ◽  
Fuel Elements ◽  
Performance Research ◽  
Cladding Material ◽  
Plate Type

Monolithic plate-type fuel is a fuel form being developed for high performance research and test reactors to minimize the use of enriched material. These plate-type fuels consist of a high uranium density LEU foil contained within diffusion barriers and encapsulated within a cladding material. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. For this work, the effects of fuel foil centering on the thermo-mechanical performance of the mini-plates were studied. To evaluate these effects, a selected plate from RERTR-12 experiments, the Plate L1P756, was considered. The fuel foil was moved within the fuel plate to study the effects of the fuel centering on stress, strain and overall shape of the fuel elements. The thickness of the fuel foil, thickness of the Zr-liners and total thickness of the plate were held constant, except the centerline alignment of the fuel foil. For this, the position of the fuel foil was varied from the center position to a maximum offset corresponding to the minimum allowable aluminum cladding thickness of 0.1524 mm. Results for various offset cases were then compared to each other and to the ideal case of a centered fuel foil. Fabrication simulations indicated that the thermal expansion mismatch results in warping of the fuel plate during fabrication as the fuel plate is cooled from the HIP temperature when the fuel is not centered. Even if the model is constrained during cooling to simulate the rigid HIP can surrounding the fuel plate during cooling, warping is observed when the constraint is removed. Similarly, irradiation simulations revealed that the fuel offset causes virtually all irradiation-induced swelling to occur on the thin-cladding side of the plate. This is observed even for the smallest offset that was considered. The total magnitude of the swelling is approximately same for all offsets values.

Impact of Mechanical Constraints on the Irradiation Performance of U10Mo Monolithic Mini-Plates

2015 ◽  
Author(s):  
Walid Mohamed ◽  
Hee Seok Roh ◽  
Gerard Hofman ◽  
Pavel G. Medvedev
Keyword(s):  
High Performance ◽  
Peak Stress ◽  
Stress Strain ◽  
Mechanical Constraints ◽  
Uranium Fuel ◽  
Operational Variables ◽  
The Difference ◽  
Irradiation Performance ◽  
Fuel Elements ◽  
Performance Research

For the conversion of high performance research reactors to low enrichment Uranium fuel, U-Mo alloy based fuels in monolithic form were proposed. These plate-type fuels consist of a high uranium density, low enrichment uranium (LEU) foil contained within a diffusion barrier, and encapsulated within a cladding. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. In this work, the effects of mechanical constraints on the thermo-mechanical behavior of a plate were studied. To evaluate these effects, a selected plate from RERTR-12 experiments (Plate L1P756) was simulated. Four distinct cases which represent four distinct welding conditions were considered. Evaluation of the stress-strain fields in the fuel elements revealed that mechanical constraints may impact the plate’s performance. These constraints include (a) inlet side, (b) outlet side, (c) both inlet and outlet sides; and finally, (d) entire long edges. Results of these cases were then compared with the ideal case. The peak stress-strain magnitudes, displacement, stress and strain profiles on the fuel elements are evaluated to make a comparative assessment. The results indicated that the cases with constraints on “inlet side only” and “outlet side only” yielded lower cladding strains compared with other cases. The difference on the displacement profiles on the fuel foil was not significant. Peak stresses on the foil did not change considerably. These results imply that the mechanical constraints effects peak cladding strains, while it does not cause significant effects on the fuel behavior.

Effects of Fuel Thickness on Thermo-Mechanical Performance of U10Mo Monolithic Fuel Plates

2017 ◽  
Author(s):  
Hakan Ozaltun ◽  
Barry H. Rabin
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
Behavioral Model ◽  
High Density ◽  
Foil Thickness ◽  
Operational Parameters ◽  
Operational Variables ◽  
Sensitivity Studies ◽  
Overall Performance ◽  
Performance Research

Monolithic fuels are being considered for conversion of high performance research and test reactors. These plate-type fuels are comprised of a low enrichment, high density U-Mo alloy fuels within an aluminum cladding. Although the plates have demonstrated satisfactory performance; still, use of a high density fuel in a foil form retains technical challenges that could affect the overall performance. To understand performance of this new design during fabrication and irradiation, the plates have been evaluated for various geometrical and operational variables. As a part of these set of parametric sensitivity studies, effects of foil thickness on performance were studied. Because high performance research reactors will utilize different fuel thicknesses, it is necessary to evaluate possible effects for a range of thicknesses that are being considered for various designs. Based on the preliminary design specifications, the fuel thicknesses were varied between the limiting cases. The bounding fuel thicknesses were 0.203 mm as minimum that is projected for ATR, and 0.635 mm as maximum that is projected for MITR. To study possible effects, a behavioral model was developed for a selected plate from RERTR-12 experiments and the plate was simulated with as run irradiation history. The simulations were repeated for a range of fuel thicknesses, while keeping the cladding thickness and the operational parameters the same. The results have indicated that the plates with thicker fuels would have higher temperatures, deformations and shutdown stresses. To investigate the effects of fuel thickness exclusively, operational parameters were scaled. In particular, a second set of simulations with prorated volumetric heat generation rates were performed. The results indicated that the fabrication stresses in the fuel foil decrease with an increasing fuel thickness. On contrary, irradiation stresses of the fuel at shutdown are higher for the plates with thicker fuels. Greater peak deformations occurred in plates with thicker fuels.

scholarly journals Effects of the Shape of the Foil Corners on the Irradiation Performance of U10Mo Alloy Based Monolithic Mini-Plates

2015 ◽  
Author(s):  
Hakan Ozaltun ◽  
Pavel Medvedev
Keyword(s):  
High Performance ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Behavioral Model ◽  
High Density ◽  
Thickness Variation ◽  
Stress Strain ◽  
Operational Variables ◽  
Irradiation Performance ◽  
Fuel Elements

Monolithic plate-type fuel is a fuel form being developed for high performance research and test reactors to minimize the use of enriched material. These fuel elements are comprised of a high density, low enrichment, U-Mo alloy based fuel foil, sandwiched between Zirconium liners and encapsulated in Aluminum cladding. The use of a high density fuel in a foil form presents a number of fabrication and operational concerns, such as: foil centering, flatness of the foil, fuel thickness variation, geometrical tilting, foil corner shape etc. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. As a part of these series of sensitivity studies, the shape of the foil corners were studied. To understand the effects of the corner shapes of the foil on thermo-mechanical performance of the plates, a behavioral model was developed for a selected plate from RERTR-12 experiments (Plate L1P785). Both fabrication and irradiation processes were simulated. Once the thermo-mechanical behavior the plate is understood for the nominal case, the simulations were repeated for two additional corner shapes to observe the changes in temperature, displacement and stress-strain fields. The results from the fabrication simulations indicated that the foil corners do not alter the post-fabrication stress-strain magnitudes. Furthermore, the irradiation simulations revealed that post-fabrication stresses of the foil would be relieved very quickly in operation. While, foils with chamfered and filleted corners yielded stresses with comparable magnitudes, they are slightly lower in magnitudes, and provided a more favorable mechanical response compared with the foil with sharp corners.

Effects of Cladding Material on Irradiation Performance of Monolithic Mini-Plates

2016 ◽  
Author(s):  
Hakan Ozaltun
Keyword(s):  
Mechanical Performance ◽  
Reactor Core ◽  
Comparative Assessment ◽  
Plastic Strains ◽  
Fuel Type ◽  
Reactor Shutdown ◽  
Irradiation Performance ◽  
Mini Plate ◽  
Cladding Material ◽  
Plate Type

Monolithic, plate-type fuels are the proposed fuel form for the conversion of the research and test reactors to achieve higher uranium densities within the reactor core. This fuel type is comprised of a low enrichment, a high density U-10Mo alloy fuel-foil, which is sandwiched between diffusion barriers and encapsulated in a cladding material. To understand the irradiation performance, fuel-plates are being benchmarked for large number of parameters. In this work, effects of the cladding material were studied. In particular, a monolithic fuel-plate with U7Mo foil and Zry-4 cladding was simulated to explore feasibility of using Zircaloy as a surrogate cladding material. For this, a selected mini-plate from RERTR-7 tests was simulated first with as-run irradiation history. By using same irradiation parameters, a second case, a plate with U10Mo fuel and Al6061 cladding was simulated to make a comparative assessment. The results indicated that the plate with Zircaloy cladding would operate roughly 50 °C hotter compared with the plate with Aluminum cladding. Larger displacement profiles along the thickness for the plate with Zircaloy cladding were observed. Higher plastic strains occur for the plate with Aluminum cladding. The results have revealed that any pre-irradiation stresses would be relieved relatively fast in reactor and the fuel-foil would be essentially stress-free during irradiation. The fuel stresses however, develop at reactor shutdown. The plate with Zircaloy cladding would have higher residual stresses due to higher pre-shutdown temperatures. Similarly, the stresses magnitudes are higher in the foil core for the plates with Zircaloy cladding. Finally, pressure on the fuel is significantly higher for the plates with Zircaloy cladding. Overall, employing a Zircaloy as surrogate cladding material did not provide a better thermo-mechanical performance compared with the Aluminum cladding.

scholarly journals Effects of the Foil Flatness on the Stress-Strain Characteristics of U10Mo Alloy Based Monolithic Mini-Plates

2014 ◽  
Author(s):  
Hakan Ozaltun ◽  
Pavel Medvedev
Keyword(s):  
Mechanical Performance ◽  
Peak Stress ◽  
Stress Strain ◽  
Strain Behavior ◽  
Uranium Fuel ◽  
Considerable Impact ◽  
Enriched Uranium ◽  
Fuel Elements ◽  
Cladding Material ◽  
Plate Type

The effects of the foil flatness on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation were studied. Monolithic plate-type fuels are a new fuel form being developed for research and test reactors to achieve higher uranium densities. This concept facilitates the use of low-enriched uranium fuel in the reactor. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. To evaluate the effects of the foil flatness on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate from RERTR-12 experiments (Plate L1P756) was considered. Both fabrication and irradiation processes of the plate were simulated by using actual irradiation parameters. The simulations were repeated for various foil curvatures to observe the effects of the foil flatness on the peak stress and strain magnitudes of the fuel elements. Results of fabrication simulations revealed that the flatness of the foil does not have a considerable impact on the post fabrication stress-strain fields. Furthermore, the irradiation simulations indicated that any post-fabrication stresses in the foil would be relieved relatively fast in the reactor. While, the perfectly flat foil provided the slightly better mechanical performance, overall difference between the flat-foil case and curved-foil case was not significant. Even though the peak stresses are less affected, the foil curvature has several implications on the strain magnitudes in the cladding. It was observed that with an increasing foil curvature, there is a slight increase in the cladding strains.

Effect of Zr Diffusion Barrier Properties on the Irradiation Performance of U-10Mo Monolithic Fuel Plate

2019 ◽  
Author(s):  
Walid Mohamed ◽  
Hakan Ozaltun ◽  
Hee Seok Roh
Keyword(s):  
Mechanical Properties ◽  
Diffusion Barrier ◽  
High Performance ◽  
Mechanical Performance ◽  
Plate Thickness ◽  
Barrier Properties ◽  
Element Analysis ◽  
Uranium Fuel ◽  
High Enrichment ◽  
Irradiation Performance

Abstract The most recent design of U-Mo monolithic fuel as adopted by the U.S. for the conversion of its High Performance Research Reactors (USHPRR) from high enrichment uranium (HEU) to low enrichment uranium fuel (LEU, < 20% U235) consists of a high density (LEU) U-10Mo fuel sandwiched between Zirconium (Zr) diffusion barriers and encapsulated in aluminum (AA6061) cladding. In this work, finite element analysis (FEA) was used to evaluate effect of Zr diffusion barrier properties on the thermal and mechanical performance of a U-10Mo monolithic fuel plate by considering possible variation in thermal and mechanical properties of the Zr diffusion barrier. Possible variation in thermo-mechanical properties of the Zr diffusion barrier were determined and a simulation matrix was designed accordingly. Analyses of simulation results included determination of global peak stresses in the fuel, Zr diffusion barrier, and cladding sections as well as the plate thickness profile at a transverse section toward the top side of the plate. Results showed that variation in yield stress, elastic modulus and thermal conductivity of the Zr diffusion barrier has negligible effect on the thermal and mechanical performance of the monolithic fuel plate. The effect of variation in these properties was found to be limited to the barrier section itself, which may be attributed to the relatively smaller thickness of that section compared to the fuel and cladding sections of the fuel plate.

scholarly journals Effects of the Foil Flatness on Irradiation Performance of U10Mo Monolithic Mini-Plates

2015 ◽  
Vol 1 (4) ◽  
Author(s):  
Hakan Ozaltun ◽  
Pavel G. Medvedev ◽  
Barry H. Rabin
Keyword(s):  
High Density ◽  
Fabrication Process ◽  
Thickness Variation ◽  
Ideal Case ◽  
Maximum Curvature ◽  
Irradiation Stress ◽  
Overall Performance ◽  
Irradiation Performance ◽  
Cladding Material ◽  
Plate Type

Monolithic plate-type fuels comprise a high-density, low-enrichment, U10Mo fuel foil encapsulated in a cladding material. This concept generates several fabrication challenges, including flatness, centering, or thickness variation. There are concerns whether these parameters have implications on overall performance. To investigate these inquiries, the effects of the foil flatness were studied. For this, a representative plate was simulated for an ideal case. The simulations were repeated for additional cases with various foil curvatures to evaluate the effects on the irradiation performance. The results revealed that the stresses and strains induced by fabrication process are not affected by the flatness of the foil. Furthermore, fabrication stresses in the foil are relieved relatively fast in the reactor. The effects of the foil flatness on peak irradiation stress-strains are minimal. There is a slight increase in temperature for the case with maximum curvature. The major impact is on the displacement characteristics. While the case with a flat foil produces a symmetrical swelling, if the foil is curved, more swelling occurs on the thin-cladding side and the plate bows during irradiation.

scholarly journals Size Effects on Thermo-Mechanical Performance of U-10Mo Monolithic Fuel Plates

2019 ◽  
Author(s):  
Hakan Ozaltun ◽  
Hee Seok Roh ◽  
Walid Mohamed
Keyword(s):  
High Performance ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Operating Conditions ◽  
Temperature Deformation ◽  
Safety Standards ◽  
Plate Size ◽  
Successful Testing ◽  
Deformation Stress ◽  
Irradiation Performance

Abstract Monolithic fuel is a fuel form that is considered for the conversion of high performance research reactors. This plate-type fuel consists of a high density U-Mo fuel in monolithic form that is sandwiched between zirconium diffusion barriers, and encapsulated in an aluminum cladding. To date, large number of plates have been irradiated with satisfactory perforamce. The program is now moving into the qualification phase, a predecessor to the timely conversion of the target reactors. It must be shown that the fuel system meets the safety standards and performs well in reactor. The requirement to satisfactory irradiation performance under normal operating conditions is primarily demonstrated by a successful testing. Since each reactor employs distinct fuel plate geometries for various consideration with unique plate design features and attributes, a single “generic” plate geometry capturing all of the extremities is not achievable. Furthermore, testing all these geometric and irradiation parameters on a large size plate is not practical. Therefore, a smaller, “down-scaled” versions of fuel plates, are often employed for experimental purposes. This limitation consequently requires much more cautious performance evaluations, as thermal and mechanical response of a plate with certain geometry may not be representative for a plate with a different geometry. To investigate if plate size has any effects on irradiation performance, the plates with various geometric dimensions were parametrically evaluated. In particular, length and width of the plates were varied between the bounding values. Temperature, deformation, stress values were comparatively evaluated. The results have indicated that effects of geometric ratios and plate size variations in length and width directions are insignificant. However, wider plates could become more prone to a warping-type deformation, if there are nonlinearities.

Effects of Fission Profiles on the Performance of a U-10Mo Fuel Plate

2019 ◽  
Author(s):  
Hee Seok Roh ◽  
Walid Mohamed ◽  
Hakan Ozaltun
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Fuel Performance ◽  
Element Analysis ◽  
Actual Use ◽  
Enriched Uranium ◽  
Performance Research ◽  
Plate Geometry

Abstract In order to convert the high-performance research reactors from High Enriched Uranium (HEU) to Low Enriched Uranium (LEU) fuel, U-Mo alloy-based fuels in monolithic form have been proposed. These plate-type fuels consist of a high density and low enriched uranium (LEU) foil coated with a diffusion barrier and encapsulated with the aluminum cladding. The performance of the fuel plate has been evaluated by many studies through experimental tests and numerical analyses. When evaluating the performance of a fuel, it is expensive and time-consuming to consider a variation of several parameters, such as fuel plate geometry, material properties, and operating conditions. Fission profile is a critical component of the fuel performance analysis, causing swelling and creep deformation of the fuel plate. Therefore, it can directly affect the stress and strain distributions over the fuel plate. This study aims at investigating the effect of different fission profiles on the thermo-mechanical performance of the fuel plate by finite element analysis. To investigate the effect of fission profile on fuel performance, several different fission profiles were generated and analyzed. The fission profiles were generated based on actual use.

scholarly journals Effects of Plate Curvature on Thermo-Mechanical Performance of U-10Mo Monolithic Fuel Plates

2019 ◽  
Author(s):  
Hakan Ozaltun ◽  
Hee Seok Roh ◽  
Walid Mohamed
Keyword(s):  
High Performance ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Geometric Parameters ◽  
Temperature Deformation ◽  
Plate Design ◽  
Plate Curvature ◽  
Deformation Stress ◽  
Performance Research ◽  
Plate Geometry

Abstract Monolithic fuel is a candidate fuel form being considered for the conversion of high-performance research reactors. This plate-type fuel consists of a high-density, U-Mo fuel in a monolithic form that is sandwiched between zirconium diffusion barriers, and encapsulated in an aluminum cladding. To date, large number of plates have been irradiated with satisfactory performance. The program is now moving into the qualification phase, a predecessor to the timely conversion of the target reactors. Since each reactor employs distinct fuel plate geometries for various consideration, resulting nearly 50 distinct plate geometries with unique plate design features, a single “generic” plate geometry capturing all of the extremities is not achievable. This limitation consequently requires much more cautious performance evaluations, as thermal and mechanical response of a plate with certain geometry may not be representative for a plate with a different geometry. To evaluate the performance of the plates for various geometric parameters, parametric sensitives studies have been employed. One of the important geometric parameters may have potential effects on the performance is the plate curvature. In this study, curved-plates were parametrically simulated to investigate if this geometric parameter has any effects on overall performance, In particular, radius of curvatures of the plates were varied between the bounding values, and the plates were simulated for comparable irradiation histories. The resulted temperature, deformation, stress-strain results were comparatively evaluated. The results have indicated that preferential deformations occur. This consequently caused shifting of plate centerline on curved plates. The magnitude of centerline shifts increased with increasing plate curvatures.

Sign in / Sign up

Export Citation Format

Share Document