Fundamental Understanding of Pebble Bed Nuclear Reactors for Environmentally Benign and Risk Free Proliferation 4th Generation Nuclear Energy and Hydrogen Production [abstract]

Abstract only availableTrack I: Power GenerationPebble bed nuclear reactor is among the 6 suggested 4th generation nuclear reactors. It is also one of the advanced high temperature gas nuclear reactors (AGRs). In such reactor the pebbles that contain the nuclear fuel particles (TRISO) (~900-950 micron) move downward while high temperature helium moves upward. These pebbles are circulated until they are spent. The pebble bed nuclear reactors are characterized as environmentally benign, risk free proliferation with high thermal efficiency (about 55% while the current nuclear reactor technology provides ~ 35%). The fundamental understanding of these reactors is lacking. Therefore, this work as a part of the research program on high temperature reactors through the consortium consists of University of Missouri - Columbia, Missouri S&T, North Carolina State University focuses on the detailed hydrodynamics of the pebbles movement, gas dynamics and heat transfer using both advanced measurement and computation techniques. The progress made on this project at Missouri S&T will be presented and the future work will be outlined

A Detailed Hydrodynamic Study of the Split-Plate Airlift Reactor by using Non-Invasive Gamma-Ray Techniques

This study focused on detailed investigations of selected local hydrodynamics in split airlift reactor by using an unconventional measurements facility: computed tomography (CT) and radioactive particle tracking (RPT). The local distribution in a cross-sectional manner with its radial\u27s profiles for gas holdup, liquid velocity flow field, shear stresses, and turbulent kinetic energy were studied under various gas velocity 1, 2 and 3 cm/s with various six axial level z = 12, 20, 40, 60, 90 and 112 cm. The distribution in gas–liquid phases in the whole split reactor column, the riser and downcomer sides, including their behavior at the top and bottom sections of the split plate was also described. The outcomes of this study displayed an exemplary gas–liquid phases dispersion approximately in all reactor\u27s zones and had large magnitude over the ring of the sparger as well as upper the split plate. Furthermore, the outcomes pointed out that the distribution of this flow may significantly impacts the performance of the split reactor, which may have essential influence on its performance particularly for microorganisms culturing applications. These outcomes are dependable as benchmark information to validate computational fluid dynamics (CFD) simulations and other models

A Detailed Hydrodynamic Study of the Split-Plate Airlift Reactor by using Non-Invasive Gamma-Ray Techniques

This study focused on detailed investigations of selected local hydrodynamics in split airlift reactor by using an unconventional measurements facility: computed tomography (CT) and radioactive particle tracking (RPT). The local distribution in a cross-sectional manner with its radial\u27s profiles for gas holdup, liquid velocity flow field, shear stresses, and turbulent kinetic energy were studied under various gas velocity 1, 2 and 3 cm/s with various six axial level z = 12, 20, 40, 60, 90 and 112 cm. The distribution in gas-liquid phases in the whole split reactor column, the riser and downcomer sides, including their behavior at the top and bottom sections of the split plate was also described. The outcomes of this study displayed an exemplary gas-liquid phases dispersion approximately in all reactor\u27s zones and had large magnitude over the ring of the sparger as well as upper the split plate. Furthermore, the outcomes pointed out that the distribution of this flow may significantly impacts the performance of the split reactor, which may have essential influence on its performance particularly for microorganisms culturing applications. These outcomes are dependable as benchmark information to validate computational fluid dynamics (CFD) simulations and other models

A Research Program on Very High Temperature Reactors

Track I: Power GenerationIncludes audio file (27 min.)Prismatic and pebble bed very high-temperature reactors (VHTRs) are very attractive both from a thermodynamic efficiency viewpoint and hydrogen-production capability. This project addresses numerous challenges associated with the fuel cycle, materials, and complex fluid dynamics and heat transfer. The objectives of the project are to: i. Conduct physical experiments for fission product transport phenomena in the overcoating and compact structural graphite and transport through TRISO coating layers; ii. Develop improved sorption measurement techniques to measure the accumulation of condensable radionuclides (“plateout”) in the VHTR primary coolant circuit and obtain representative data; iii. Develop advanced computations of charged, radioactive dust (aerosol) transport in the VHTR coolant circuit and confinement by exploring direct simulation Monte Carlo (DSMC) techniques for deposition and resuspension and conduct experiments to verify computational predictions; iv. Develop a program to measure emissivity for various VHTR component materials, both bare and oxidized, and obtain extensive data; v. Develop an experimental program to characterize gas, fission product, and particle flows in the complex geometries of pebble bed modular reactors (PBMRs) and help improve computational approaches and computer programs through experimental understandings. This project is leading to research training of about a dozen Ph D students at the participating universities. Upon graduation, these students will be able to contribute even more effectively to the future challenges in the global deployment of nuclear power generation and hydrogen technologies. We will discuss the VHTR technology and research challenges. We also describe progress on the project by the three Consortium participants

Investigation of a Complex Reaction Network: I. Experiments in a High-Pressure Trickle-Bed Reactor

A High-Pressure Trickle-Bed Reactor Was Used to Achieve High Productivity and Selectivity for the Manufacture of a Key Herbicide Intermediate (Α-Aminomethyl-2-Furanmethanol (Amino Alcohol, AA) from Α-Nitromethyl-2-Furanmethanol (Nitro Alcohol, NA). Raney Nickel Catalysts of Varying Activity Were Prescreened for Suitability in Trickle-Bed Operation. the Effect of Operating Parameters Such as Reactant Feed Concentration, Liquid Mass Velocity, and Temperature on the Yield of Amino Alcohol (AA) for RNi-A Are Discussed. the Superiority of Trickle-Bed Reactors over Others Such as Semibatch and Batch Slurry Systems is Demonstrated. the AA Yield Increases with Decrease in Feed Reactant Concentration and Liquid Mass Velocity, as Well as with Lowering of the Operating Temperature. a Maximum Product Yield of 90.1% Was Obtained at 8.3 Wt. % Feed Concentration of Nitroalcohol (NA), While at the Highest Feed Concentration of 40 Wt. % NA, the Maximum Product Yield Was 58%. the Volumetric Productivity of AA Was Significantly Higher at Higher Reactant Feed Concentrations, Even Though the Yield Was Lower under These Conditions. the Operating Temperature Was Also an Important Parameter, with a Lower Temperature Being Preferable for Trickle-Bed Experiments. Bed Dilution with Inert Fines Improved Catalyst Utilization and Increased the AA Yield and Productivity in the Laboratory-Scale Trickle-Bed Reactor

Investigation of a Complex Reaction Network: II. Kinetics, Mechanism and Parameter Estimation

Conventional Strategies for Discrimination of Intrinsic and Apparent Kinetics from Crushed- and Whole-Catalyst-Pellet Experimental Data, Respectively, Do Not Yield Satisfactory Results for the Reaction Network in the Manufacture of Α-Aminomethyl-2-Furanmethanol (Aminoalcohol) from Α-Nitromethyl-2-Furanmethanol (Nitroalcohol). Laboratory Trickle-Bed Reactor Tests in the Range of Concentration and Product Yield of Commercial Interest Are Utilized to Yield a Reasonable Set of Kinetic Parameters, Which Are Otherwise Unobtainable. This is Accomplished by Proposing a Reaction Network, a Plausible Mechanism, and Optimizing the Kinetic Parameters based on the Reactor-Model-Generated Performance Data to Fit Experimental Output Concentrations of All Species for the Entire Set of Experiments. a Complex Reaction Network for the Key Reactions in the System is Developed based on the Reaction Scheme in Part I. Fitting of Trickle-Bed Reactor Data to This Model is Attempted to Yield an Insight into the Actual Kinetics. the Results Show Promise of Obtaining an overall Network Kinetic Model, Even with the Limited Data Available

Evaluating different machine learning methods to simulate runoff from extensive green roofs

Green roofs are increasingly popular measures to permanently reduce or delay storm-water runoff. The main objective of the study was to examine the potential of using machine learning (ML) to simulate runoff from green roofs to estimate their hydrological performance. Four machine learning methods, artificial neural network (ANN), M5 model tree, long short-term memory (LSTM) and k nearest neighbour (kNN), were applied to simulate storm-water runoff from 16 extensive green roofs located in four Norwegian cities across different climatic zones. The potential of these ML methods for estimating green roof retention was assessed by comparing their simulations with a proven conceptual retention model. Furthermore, the transferability of ML models between the different green roofs in the study was tested to investigate the potential of using ML models as a tool for planning and design purposes. The ML models yielded low volumetric errors that were comparable with the conceptual retention models, which indicates good performance in estimating annual retention. The ML models yielded satisfactory modelling results (NSE >0.5) in most of the roofs, which indicates an ability to estimate green roof detention. The variations in ML models' performance between the cities was larger than between the different configurations, which was attributed to the different climatic characteristics between the four cities. Transferred ML models between cities with similar rainfall events characteristics (Bergen–Sandnes, Trondheim–Oslo) could yield satisfactory modelling performance (Nash–Sutcliffe efficiency NSE >0.5 and percentage bias |PBIAS| <25 %) in most cases. However, we recommend the use of the conceptual retention model over the transferred ML models, to estimate the retention of new green roofs, as it gives more accurate volume estimates. Follow-up studies are needed to explore the potential of ML models in estimating detention from higher temporal resolution datasets

Pressure Distribution in Bolted Connections

Pressure distribution in bolted connections obtained from an exact analysis by the authors has been compared with that of an approximate method suggested by Motosh. Based on this comparison, the limitation of Motosh\u27s procedure has been clearly brought out. It is shown that the pressure distribution in bolted connections could be obtained fairly accurately by using a two-dimensional solution of a semi-infinite strip

Stress Analysis of a Thick Plate Having a Circular Hole under Axisymmetric Radial Load

In this paper a solution for the determination of stresses and displacements in a thick plate having a cylindrical hole subjected to localised hydrostatic loading has been given. Detail numerical results have been presented and compared with the results of an infinite hole subjected to localised hydrostatic load and a semiinfinite hole subjected to localised end load. It has been shown that for certain ratio of thickness of the pate to the radius of the hole and loading, the results could be obtained by using the solution of infinite or semiinfinite hole subjected to the same hydrostatic loading