39 research outputs found
Impact of reactor environment on quenching heat transfer of accident tolerant fuel cladding
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018Cataloged from student-submitted PDF version of thesis. Page 123 blank.Includes bibliographical references (pages 106-116).Development of accident tolerant fuels (ATF) for light water reactors (LWRs) came into focus for the nuclear engineering community after the accidents at Fukushima-Daiichi. The primary focus of the ATF program is to identify alternative fuel and cladding technologies that may provide enhanced safety, competitiveness, and economics. The new fuel design must also be compatible with present-day LWR design. For near-term applications, coatings on the nominal Zirconium-based cladding material and other metallic materials are being considered to improve the corrosion resistance and reduce the generation of hydrogen at high temperatures. Major ATF coating choices under consideration include chromium as a coating, iron-chromium-aluminum alloys (FeCrAl) as cladding and molybdenum as a coating, which have demonstrated better mechanical and oxidation behavior during the experimental testing.Thermal-fluids characteristics are pivotal for a robust testing of ATF concepts as the proposed candidates may have an entirely different thermal-hydraulic behavior when compared to Zircaloy-4. ATF coatings may display very different boiling characteristics as a result of different microstructures and surface characteristics. In the present work, transient boiling heat transfer during quenching of the candidate ATF claddings on vertical rodlets is studied experimentally. The candidate ATF material (chromium, FeCrAl, and molybdenum) are applied on Zircaloy-4 rodlets. The vertical solid rodlets are heated to temperatures up to 1000 °C and are quenched in a saturated pool of water at atmospheric pressure. The temperature variation during the quenching of rodlets was recorded insitu with synchronized visualization of boiling regimes over the test specimen using a high-speed video camera.The quench performance of the ATF coatings was analyzed based on the examination of various surface parameters such as wettability, roughness, emissivity and capillary wicking. In order to obtain a more realistic picture of the candidate performance during the emergency cooling reflood phase in a nuclear reactor, the coated rodlets are also oxidized in an autoclave before quenching. The performance of the candidate claddings is evaluated after oxidation and the surface characterized. It was observed from the post-test analysis that the surface characteristics and oxidation had a significant impact on the quench performance of ATF coatings, which varied between different coating materials. In order to better understand the thermal margins in a reactor specific environment, an analysis was performed on samples after exposing them to gamma rays. The gamma rays tend to change the surface wettability through a phenomenon called Radiation Induced Surface Activation.A Gammacell 220E irradiator that uses 12 cobalt-60 pencil sources, arranged axially in a sample chamber at MIT, was used to irradiated the samples. The results of water quenching and contact angle studies showed a higher Leidenfrost temperature and wettability in both samples exposed to gamma irradiation. The detailed microscopic analysis attributed the enhanced wettability to oxidation of the surface under gamma irradiation.by Arunkumar Seshadri.S.M.S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineerin
Development of Cr cold spray–coated fuel cladding with enhanced accident tolerance
No full textAccident-tolerant fuels (ATFs) are currently of high interest to researchers in the nuclear industry and in governmental and international organizations. One widely studied accident-tolerant fuel concept is multilayer cladding (also known as coated cladding). This concept is based on a traditional Zr-based alloy (Zircaloy-4, M5, E110, ZIRLO etc.) serving as a substrate. Different protective materials are applied to the substrate surface by various techniques, thus enhancing the accident tolerance of the fuel. This study focuses on the results of testing of Zircaloy-4 coated with pure chromium metal using the cold spray (CS) technique. In comparison with other deposition methods, e.g., Physical vapor deposition (PVD), laser coating, or Chemical vapor deposition techniques (CVD), the CS technique is more cost efficient due to lower energy consumption and high deposition rates, making it more suitable for industry-scale production. The Cr-coated samples were tested at different conditions (500°C steam, 1200°C steam, and Pressurized water reactor (PWR) pressurization test) and were precharacterized and postcharacterized by various techniques, such as scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX), or nanoindentation; results are discussed. Results of the steady-state fuel performance simulations using the Bison code predicted the concept's feasibility. It is concluded that CS Cr coating has high potential benefits but requires further optimization and out-of-pile and in-pile testing. Keywords: Accident-Tolerant Fuel, Chromium, Cladding, Coating, Cold Spray, Nuclear Fue
Understanding the Impact of Nuclear Environment on the Hydrothermal Corrosion in SIC
No full textSiC/SiC fiber composites are potential candidates for advanced cladding materials to improve the accident tolerance of commercial light-water nuclear reactor fuel. To evaluate the fiber composites’ viability, understanding the kinetics of their corrosion in Light Water Reactor (LWR) conditions is critical. SiC corrosion results in the formation of silica, which can then be rapidly dissolved in the LWR environment. LWR conditions are demanding on materials because they are subjected to irradiation, high pressure, high temperature, and aqueous chemistry. Experiments were performed under prototypical LWR conditions (Pressure, temperature, flow rate) to understand the corrosion and silica dissolution characteristics of high purity chemical vapor deposited (CVD) SiC. Sensitivity studies are performed to develop a comprehensive model for silica dissolution considering the impact from irradiated microstructure (through Si/ proton, Co60 gamma, and neutron pre-irradiation), flow rate, electrical resistivity, surface roughness, surface wettability, and CRUD (metallic oxide impurities) deposition. The corrosion rate in the irradiated microstructures was found to be an order of magnitude higher compared to the unirradiated microstructure under boiling water reactor (BWR) conditions. Electrochemical and spectroscopic studies revealed that the enhanced corrosion in irradiated samples was the result of an increased surface reaction potential that can be associated with the structural defects and the electronically excited states produced by irradiation. Surface roughness effects on hydrothermal corrosion also accelerated the corrosion rate significantly at high mass flow rates relevant to LWR operating conditions. Based on the experimental results, the existing semi-empirical SiC hydrothermal corrosion kinetic models are updated to include the effects of irradiation, resistivity, flow rate, and pH. Further, the experimental results suggest that the CRUD deposition on the CVD SiC would reduce corrosion significantly. Enhanced CRUD formation was observed under gamma irradiation and was correlated to the reduced zeta potential and the contact angle of the surface. Further adhesion properties responsible for CRUD deposition in SiC are investigated to evaluate the likelihood of CRUD deposition in LWR conditions.
The silica dissolution rate of nuclear grade Hi-Nicalon type S fibers and fibers manufactured with Rapid Laser chemical vapor deposition (R-LCVD) with varying surface chemistries were also obtained through experiments performed in static autoclave simulating PWR conditions. The hydrothermal corrosion behavior of stoichiometric R-LCVD fibers was observed to be comparable to the nuclear grade Hi-Nicalon Type S fibers. The results show that the impact of stoichiometry was much higher than the particular manufacturing technique, though the higher surface roughness in R-LCVD fibers significantly affected the corrosion kinetics. Thermal pre-treatment of R-LCVD fibers leads to a drastic reduction in the corrosion of SiC fibers and was correlated to the increased grain size on the fiber surface when exposed to high temperatures. The effect of pre-ion irradiation on the hydrothermal corrosion behavior of SiC fibers was found to exhibit a complex relationship based on the stoichiometric composition of the fibers.
Finally, the Radiation Chemistry Analysis Loop (RADICAL) code that models the complete coolant loop chemistry, radical, and species transport in LWRs, is modified to include SiC/SiC cladding corrosion and silica transport based on experimentally determined silica formation and dissolution rates. Sensitivity analysis is further carried out on several parameters in RADICAL to inform the industry on the extent of spatial inventory of silica deposition in typical BWR and pressurized water reactor (PWR) primary loops. RADICAL modeling suggests that silica deposition in PWR components and CVD SiC thickness loss is not of great concern even when the effect of irradiation damage on SiC corrosion is considered. However, for BWRs, significant silica deposition on components and CVD SiC thickness loss is expected unless the fuel rod is covered entirely in stable CRUD within the first few months of operation. As such, a feasibility study on different protective metallic coatings applied on the SiC/SiC fiber composite was conducted to reduce the thickness loss. Out of different coatings tested, plasma spray coated and vacuum annealed FeCrAL with blended FeCrAl, Cr coating served as a stable protective barrier against SiC dissolution in hydrothermal conditions.Ph.D
A Review of Irradiation Damage and Effects in α-Uranium
No full textUnderstanding irradiation damage and effects in α-uranium (α-U) is critical to modeling the behavior of U-based metallic fuels. The aim of this review is to address the renewed interest in U-based metallic fuels by examining the state-of-the-art knowledge associated with the effect of irradiation on the microstructure, dimensional changes, and properties of α-U. We critically review the research progress on irradiation-induced growth and swelling, the enhancement of plastic flow and superplasticity by irradiation, and the effect of irradiation on thermal and electrical properties of α-U. Finally, we outline the research directions that require advancements, specifically the need to carry out fundamental research on several of the less understood mechanisms of irradiation damage and effects in α-U
Stability of n-Dimensional Additive Functional Equation in Generalized 2-Normed Space
No full textIn this paper, the author established the general solution and generalized Ulam-Hyers-Rassias stability of n-dimensional additive functional equatio
Investigations on optical properties of Eu3+ ion doped magnesium telluroborate glasses for red laser applications
No full textScreening of Pediocin Pa-1 Producing Lactic Acid Bacteria by Pcr
No full textThis Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page
Generalized Ulam- Hyers Stability of Derivations of a AQ- Functional Equation
No full textIn this paper, the author established the generalized Ulam- Hyers stability of Deriva-tions of additive and quadratic (AQ)- functional equation f(x+ y) + f(x − y) = 2f(x) + f(y) + f(−y). RESUMEN En este art́ıculo el autor establece la estabilidad generalizada Ulam-Hyers de deriva-ciones de la ecuación (AQ)-funcional cuadrática y aditiva f(x+ y) + f(x − y) = 2f(x) + f(y) + f(−y)
