Nanofluid Operation and Valve Engineering of SUPER for Small Unit Passive Enclosed Reactor

Abstract

The basic features as well as nanofluid operation and valve engineering of Small Unit Passive Enclosed Reactor abbreviated as SUPER, a new reactor system that has been proposed by the Department of Energy Systems Engineering at the Seoul National University, are presented in this dissertation. SUPER is a small modular reactor system or SMR that is cooled by water and designed to be factory-manufactured and shipped as modules to be assembled on-site. It has been evolved from the System-integrated Modular Advance Reactor (SMART). SUPER enhances the safety features for robustness, design/equipment simplification for natural convection, and multi-purpose application for co-generation, suitable for isolated or small electrical grids, just-in-time capacity addition, short construction time, and last but not least, lower capital cost per unit. In this study, a simplified core thermal analysis of SUPER is performed using APR1400 fuel configuration as the reference. An octant symmetry of the same fuel assembly (FA) using McCARD is also analyzed. Considering the single-phase natural circulation, the SUPER core thermal power of 400 MW and mass flow rate of 1306 kg/s are estimated. Finally, the power conversion cycle efficiency of the SUPER system is calculated without considering the effect of turbine valves which is approx. 36%.

Nanofluids has regained the attention as a promising coolant for light-water reactors (LWRs) due to its higher heat transfer performance that attributed as: convective heat transfer and critical heat flux enhancement as well as improved flow stability in natural circulation system. This attributes offer several opportunities of using nanofluids as favorable coolant in nuclear applications, including LWR main coolant, passive emergency safety and severe-accident mitigation coolant. Motivated by the promising options of nanofluids, in this study the heat transfer and pressure drop characteristics are studied in the so-called NANO (Nine Array Nanofluid Operation) rod bundle under a fully-developed single-phase turbulent upflow condition. The NANO bundle is designed to check on thermos- and hydrodynamic performance of alumina nanofluid in a uniformly-heated square-array rod bundle having a pitch-to-diameter ratio of 1.286, a fuel assembly building block for a SMR sharing commonalities with the current fleet of pressurized water reactors (PWRs). Nine cartridge-type heater rods are installed in the 3×3 square array with four grid spacers utilizing water and alumina as coolant spanning the inlet Reynolds numbers from 21,000 to 100,000. The Nusselt numbers for a wide range of flow inlet velocity and power are obtained and compared against the well-known correlations. For unheated water the predicted pressure drop generally agreed with the experimental data. For heated nanofluid the pressure drop as well as heat transfer increased with the Reynolds number. The results are compared against the recognized correlations, and deviations are elucidated quantitatively.

In nuclear power plant

reactor, turbine and electrical-generator systems are coupled together in which turbine valves play a pivotal rule by controlling the steam mass flow rate to the turbine as per load demand. Being motivated by the significance of turbine valve, in this study experimental and numerical analysis are carried out to study the flow characteristics (FC) of turbine combined (i.e. stop and control) valve which is well-suited for proposed SUPER system. The model valve has specially designed, developed and tested to use as turbine overload by-pass valve to support effective electrical-load following operation. Valve Engineering Layout Operation (VELO) and Valve Engineering Numeric Analysis (VENA) are used as experimental and numerical tools, respectively. CATIA V.5® and STAR-CCM+ are used for computer-aided-design and computational-fluid-dynamics analysis, respectively.