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result(s) for
"Sodium cooled reactors."
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Sodium fast reactors with closed fuel cycle
The authors cover research and development on the sodium cooled fast reactors. They deal with a wide range of topics in the domain of science and technology under topics like design aspects, safety, construction, fuel cycles, and more.
Book
Tellurium Corrosion of Type 304/304L Stainless Steel, Iron, Chromium, and Nickel in High-Temperature Liquid Sodium
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with Te in liquid sodium at 773 K for 30 days. At 10 ppm oxygen, SS304 showed multiple oxide layers, including a compact NaCrO2 interlayer and porous Na-Fe-Ni-O outer layers. Tellurium penetrated through the porous layers but was hindered by the NaCrO2 interlayer. At 0.01 ppm oxygen, Cr had no oxide layer, while Fe and Ni had unstable ones. Tellurium-induced pitting was deeper in Fe and Ni compared to Cr. Oxygen levels and Cr composition are critical factors affecting stable oxide compound layer formation and mitigating Te-induced pitting.
Journal Article
Phase transitions of sodium peroxide investigated by DSC
To simulate the sodium fire phenomenon that is expected to occur in an accident of sodium-cooled fast reactor, it is necessary to obtain the thermodynamic parameters that describe the structural phase transition and melting of sodium peroxide (Na
2
O
2
). Nevertheless, the thermodynamic database and existing literature provide only limited information on this topic. The objective of this study was to ascertain the thermodynamic parameters associated with the phase transitions of Na
2
O
2
through the use of differential scanning calorimetry (DSC). Due to the high chemical reactivity of Na
2
O
2
at elevated temperatures, particular precautions were necessary for the DSC measurement, including the selection of an appropriate crucible material, the preparation of a custom-made crucible with a specialized geometrical configuration, and the meticulous calibration of the recorded temperature and enthalpy change. Furthermore, all experimental procedures for the DSC measurement were required to be conducted under controlled atmospheric conditions of inert gas. Despite the aforementioned difficulties, we were able to successfully determine the transition temperatures and enthalpy changes associated with the structural phase transition and melting of Na
2
O
2
using DSC. The reliability of these thermodynamic parameters was validated by comparing them with previously reported values.
Journal Article
Effects of Temperature on the Fretting Wear Behavior of 2.25Cr-1Mo Tubes against Gr5C12 Rods
In the heat exchangers of sodium-cooled fast reactors, sodium flow can cause the tubes to vibrate, resulting in fretting wear damage due to the contact between the tubes (2.25Cr-1Mo steel) and their support plate (Gr5C12 alloy). In this work, the effects of temperature on the fretting wear behavior of a 2.25Cr-1Mo heat transfer tube on a Gr5C12 alloy rod were studied. The results showed that the coefficient of friction (COF) and wear volume increased first and then decreased with the increase in temperature. Moreover, 2.25Cr-1Mo showed great wear performance at high temperatures than at room temperature and 80 °C, because of the antifriction nature of the oxidative layer and the high hardness of the tribological transformed structure layer. As the temperature increased, material transfer and plastic deformation became increasingly obvious, but average wear depth decreased. This provides data support for the practical engineering application of 2.25Cr-1Mo steel at elevated temperatures. Wear mechanisms were found to depend modestly on temperature and largely on normal load. As temperature increases, the wear mechanism gradually changes from abrasive wear to adhesive wear.
Journal Article
Experimental study of the natural convection characteristics of finned-tube sodium-to-air heat exchanger
The finned-tube sodium-to-air heat exchanger plays a crucial role in ensuring the safety of prototype Gen IV sodium-cooled fast reactors. It is designed to actively operate with power, but it is also important to consider its passive performance to ensure availability during power-out conditions. This study focused on addressing this limitation through a natural convection experiment using a dedicated facility, and the obtained results were compared with the safety analysis code MARS-LMR. The overall temperature difference was observed to be within an acceptable range of less than 5 %. While the code calculations aligned well with the experimental results at higher temperatures, they underestimated the experimental results at lower temperatures. These findings can serve as a basis for other codes employing different heat transfer correlations and for future reactor licensing purposes.
Journal Article
Thermal behavior and kinetics of the reaction between liquid sodium and calcium hydroxide
Thermally-induced reaction between liquid sodium (Na(l)) and calcium hydroxide (Ca(OH)2(s)) was investigated as one of the possible component reactions when Na(l) was reacted with concrete materials under a postulated severe accidental condition in a sodium-cooled fast reactor. The Na(l)–Ca(OH)2(s) reaction was traced using a differential scanning calorimetry (DSC), placed in an argon substituted glove box. An exothermic DSC peak appeared in the temperature range of 550–700 K was attributed to the Na(l)–Ca(OH)2(s) reaction to form a mixed phase comprised of calcium oxide (CaO(s)), sodium hydroxide (NaOH(s,l)) and sodium oxide (Na2O(s)). Based on morphological analyses of reacting system, a physico-geometrical reaction model was proposed: the reaction initiates at the initial contact area of Na(l) and Ca(OH)2(s) and proceeds by the movement of the reaction interface toward Ca(OH)2(s), where the product layer is composed of CaO(s), NaOH(s,l), and Na2O(s). Therefore, the Na(l) diffusion through the product layer is the necessary process to promote the reaction between Na(l) and Ca(OH)2(s), for which a significant influence of the melting of NaOH(s) that has on the overall kinetic behavior is expected. This melting occurs midway through the Na(l)–Ca(OH)2(s) reaction at 594 K. The overall Na(l)–Ca(OH)2(s) reaction was analyzed kinetically using the DSC curves recorded at different heating rates. A partially overlapping two-step reaction feature was evidenced, in which the primary and secondary reaction steps were characterized by the apparent activation energy values of 128 and 138 kJ mol−1, respectively. The multistep feature of the Na(l)–Ca(OH)2(s) reaction could result from the melting of NaOH(s) in the product layer.
Journal Article
Symmetric Heat Transfer Pattern of Fuel Assembly Subchannels in a Sodium-Cooled Fast Reactor
The method outlined in this paper is convenient and effective for studying the thermal performance of fuel assemblies cooled with sodium fast reactors using the subchannel procedure. To initially study an optimization model for a symmetric single fuel assembly heat transfer pattern analysis in a fast sodium-cooled reactor based on subchannel calculations, this paper innovatively proposes a subchannel heat transfer analysis method with the entransy dissipation theory, which can solve the limitations and inaccuracies of the traditional entropy method such as poor applicability for heat transfer processes without functional conversion and the paradox of entropy production of heat exchangers. The symmetric distributions of the thermal-hydraulic parameters such as coolant flow rate, coolant temperature, cladding temperature, and fuel pellet temperature were calculated, and the entransy dissipation calculation method corresponding to the fuel assembly subchannels was derived based on the entransy theory. The effect of subchannel differences on the thermal-hydraulic parameters and the symmetric distribution pattern of entransy dissipation during the cooling process of the fuel assembly was analyzed and compared from the symmetrical arrangement of subchannels in the axial and radial directions.
Journal Article
Design of perforated plate for uniform flow distribution in heat-exchanger unit of SFR steam generator
In the steam generator of a sodium-cooled fast reactor, heat transfer occurs from the primary sodium flow side at high temperature to the secondary water flow side at low temperature. Preventing the interaction between sodium and water in the heat exchanger is important to avoid a reactive explosion. To do so, the concept of the copper bonded steam generator, which consists of heat-exchanger modules with cross-flow-type arrangement, was recently proposed. In this cross-type arrangement, the sodium flow should be as uniform as possible throughout the horizontal channels in terms of the heat transfer efficiency between the sodium and water sides. This study aims to design a perforated plate leading to uniform sodium flow distribution throughout the 66×33 channels. The geometrical design and location of the perforated plate are optimized using numerical simulation. The designed plate improves the flow distribution uniformity at a slight cost of pressure loss.
Journal Article
Kinetic study on liquid sodium–silica reaction for safety assessment of sodium-cooled fast reactor
In this study, the kinetic behavior of the sodium (Na)–silica (SiO
2
) reaction was investigated for an assessment method of reactivity/stability of siliceous concrete against the sodium–concrete reaction (SCR) by postulating a severe accidental condition in the sodium-cooled fast reactor (SFR). The reaction behavior was tracked using a differential scanning calorimetry (DSC) equipped with a videoscope for viewing the changes in the sample during the reaction. The reaction was characterized as a partially overlapping multistep process controlled by physico-geometrical reaction scheme. The kinetic behavior in view of the change in the temperature at the maximum reaction rate with heating rate was analyzed using the simplified Kissinger method and the approximated Ozawa method. Further by separating the kinetic data for the overall reaction into five component reaction stages, the kinetic information for the second and third reaction stages was extracted. By comparing the kinetic results, it was revealed that the kinetic results determined from the kinetic data at the maximum reaction rate can be interpreted as is for the major reaction stage (the third reaction stage) controlled by an autocatalytic reaction. In addition, the second reaction stage was characterized as a possible premonitory process for the major reaction stage. Through the comprehensive interpretation of the kinetic results, significance of the kinetic analysis for the Na–SiO
2
reaction using DSC for the reactivity/stability evaluation against SCR and for the safety assessment of SFR is discussed.
Journal Article
Preparation of metallic fuel rodlets for irradiation testing in the HANARO research reactor
U–10 wt% Zr fuel rodlets, which will be irradiated in the HANARO research reactor in order to evaluate the irradiation performance of metallic fuel and validate the in-reactor behavior, were prepared through determined fabrication processes. Injection casting technology was applied to produce U–10Zr fuel slugs, and sodium melt and a bonding process were conducted to bond a fuel slug to the fuel cladding. To seal the end plug to the fuel cladding tube, a gas tungsten arc welding technique was adopted. Based on the results of these experiments, sodium-cooled fast reactor fuel rodlets for irradiation testing in the HANARO research reactor have been soundly fabricated.
Journal Article