Nuclear Engineering ETDs

Publication Date

Summer 8-1-2023

Abstract

Heavy metals and alkali Liquid Metals are suitable coolants for Generation IV terrestrial nuclear reactors for operating at elevated temperatures for achieving plant thermal efficiency more than 40% and the thermochemical generation of hydrogen fuel. In addition, the low vapor pressure of these liquids eliminates the need for a pressure vessel and instead operates slightly below ambient pressure. A primary issue with the uses of these coolants is their compatibility with nuclear fuel, cladding and core structure materials at elevated temperatures more than 500oC. Therefore, in pile and out-of-pile test loops have been constructed or being considered for quantifying the effect of the operating temperature flow velocity on the compatibility of versus fuel and structural materials with heavy liquid metals of lead (Pb) and lead Bismuth Eutectic (LBE) and alkali liquid metals of sodium for fast spectrum nuclear reactors. Recently, two in-pile test loops are thought for supporting the developments of molten lead and liquid sodium-cooled advanced reactors in the US and investigating the compatibility of several structure and cladding materials with these liquid metals at different temperatures and flow rates in a prototypical irradiation environment. These test loops were to be placed at designated locations within the core of the sodium-cooled, fast neutron spectrum 300 MWth Versatile Test Reactor (VTR). In these in-pile loops. It is desirable to employ miniature submersible v electromagnetic pumps (EMPS) with no moving parts for reliable operation. which is the focus of the present research. These pumps need to fit within the 2.5-inch diameter standard tube for the test loop riser downstream of the test article of one or more nuclear fuel rodlets, and with compatible components with molten lead and liquid sodium initially at temperatures up to 500oC. At these temperatures, 316SS cladding and structure materials is suitable choice, but not at higher temperature for which nickel free materials are being investigated. The objective of this research is therefore to develop designs and conduct performance analyses of miniature, submersible EMP for operating at temperatures < 500oC in in-pile and out-of-pile test loops for supporting the current development of GenIV molten Pb and liquid Na fast neutron spectrum terrestrial nuclear reactors. The two miniature submersible designs investigated are of a Direct Current-ElectroMagnetic pump (DC-EMP) and an Alternating Linear Induction Pump (ALIP). In the DC-EMP), in which DC electric current from Cu electrodes flows through the working fluid flowing in a narrow rectangular duct in the perpendicular direction to those of the flow and the generating magnetic flux density using permanent magnet(s). The produced Lorentz force in the pump duct drives the fluid flow. The ALIP’s linearly traveling magnetic fields produced by 3Phase alternative currents in winding coils surrounding the annular flow duct generate electrical current in the perpendicular directions of the generated electric current and magnetic field. The generated Lorentz force drives the flow in a narrow annular flow duct. The two submersible EMPs have an outer diameter of 66.8 mm outer diameters, which fit in a 2.5-inch standard tube with an inner diameter of 68.8 mm, and 1.00 mm clearance to the wall’s inner surface. The developed DC-EMP employs Alnico-5 permanent magnets with Hiperco-50 pole pieces for focusing the magnetic field lines in the 316SS rectangular flow duct and operating at temperatures up to 500oC. The novel 66.8mm pump design has dual pumping stages for enhance performance, enabled using a pair of Alnico-5 permanent magnets mounted along the rectangular flow duct and with opposite magnetizing directions in the two pumping regions of the flow duct. The electrical currents through the flow duct in the two pumping regions are supplied in opposite directions perpendicular to those of the flow and the magnetic field flux density, so that the generated Lorentz forces in the two pumping vi stages act in the same flow direction. The developed ALIP design employs hightemperature, ceramic insulated Copper wires for winding coils, and Hiperco-50 center core and stators. The performance analyses for the two pump designs are conducted using the lumped, electrical Equivalent Circuit Model (ECM). For the present DC-EMP the ECM on MATLAB platform is linked to the FEMM software, for calculating the effective electrical currents and magnetic field distribution in the pump duct at zero flow. The fast-running ECM includes a few simplifying assumptions, nonetheless it has been shown by other investigators and in this work to overpredict the pump characteristics by 10- 25%. The implements ECM for the present ALIP design is improved compared to the widely used and originally proposed model by Baker and Tessier. The accuracy of the improved ECM for the present ALIP design is confirmed by comparing predictions to the reported experimental data by others for low-flow sodium, small ALIP. The ECM predictions of the pump characteristics are <6% higher than reported experimental measurements. The performed parametric analyses of the present 66.8 mm diameter DC-EMP design investigated the effects of varying the dimensions of the flow duct width and height, the length of the current electrodes the thickness of the ALNICO-5 permanent magnets, and the separation distance of the two pumping regions on the pump performance parameters. These include the pump characteristics and the cumulative pumping power, pump efficiency and the dissipated thermal power as functions of flow rate of molten lead and liquid sodium. The parametric analyses of the ALIP investigated the effects on the pump performance parameters of varying the dimensions, the winding wire diameter, the width of the annular flow duct, the length of center core, the terminal voltage and current frequency. The present miniature, submersible DC-EMP for circulating molten lead at inlet temperature of 500oC, has a maximum efficiency of 11.3% at a flow rate of 5.75 m3/h (16.2 kg/s) and pumping pressure of 282 kPa, with a dissipated thermal power of 3.2 kW. For liquid sodium at the same temperature, the maximum pump efficiency is much higher; 36.5% at a flow rate of 3.95 m3/h (0.9 kg/s) and pumping pressure of 379 kPa and dissipated thermal power of 4.1 kW. vii The predicted efficiency of the miniature, submersible ALIP design for molten lead at inlet temperature of 500oC is lower than for the Dc-EMP. The ALIP maximum efficiency of 6.7% occurs at a flow rate of 3.37 m3/h (9.5 kg/s) and pumping pressure of 263 kPa, with a dissipated thermal power of 3.2 kW. For liquid sodium at the same temperature, pump efficiency increases to 26.3% and occurs at a flow rate of 9.66 m3/h (2.2 kg/s), pumping pressure of 364 kPa, and dissipated thermal power of 2.7 kW. To gain insight into the pump operation parameters and quantify the effect of the simplifying assumption in the ECM, this work conducted 3-D MagnetoHydroDynamic (MHD) numerical analyses of the present design of the 66.8 mm diameter dual-stage DCEMP using Star-CCM+. The results of these analyses are not easily attainable otherwise, even experimentally. The MHD analyses solve the coupled electromagnetism, and the momentum and energy balance equations in the pump flow duct to obtain detailed spatial distributions of the coupled electrical, magnetic, thermal, and fluid flow parameters, and calculate the pump characteristics. The adequacy of the numerical mesh refinements for results conversion is confirmed using the Grid Convergence Index (GCI) criterion. The 3-D MHD numerical analyses results show strong dependence of the spatial distribution of the magnetic field on the value and the distribution of the electric current in the flow duct and confirm a negligible effect of joule heating on fluid temperature and pump characteristics. The MHD results of the pump characteristics are lower but in general agreement with the ECM predictions, with the difference increasing with increased flow rate and input electrodes electric current up to 12% and 14% for molten lead and liquid sodium, respectively.

Keywords

Gen-IV nuclear reactors, Electromagnetic pumps, Test loops, ALIP, DC-EMP, MHD, Magnetohydrodynamics, Liqiud metal reactors, Molten Lead, Sodium

Document Type

Dissertation

Language

English

Degree Name

Nuclear Engineering

Level of Degree

Doctoral

Department Name

Nuclear Engineering

First Committee Member (Chair)

Dr. Mohamed S. El-Genk

Second Committee Member

Dr. Edl Schamiloglu

Third Committee Member

Dr. Minghui Chen

Fourth Committee Member

Dr. Timothy M. Schriener

Download

Share

COinS