Experimental and Computational Study of a Scaled Reactor Cavity Cooling System

The Very High Temperature Gas-Cooled Reactor (VHTR) is one of the next generation nuclear reactors designed to achieve high temperatures to support industrial applications and power generation. The Reactor Cavity Cooling System (RCCS) is a passive safety system that will be incorporated in the VTHR, designed to remove the heat from the reactor cavity and maintain the temperature of structures and concrete walls under desired limits during normal operation and accident scenarios. A small scale (1:23) water-cooled experimental facility was scaled, designed, and constructed in order to study the complex thermohydraulic phenomena taking place in the RCCS during steady-state and transient conditions. The facility represents a portion of the reactor vessel with nine stainless steel coolant risers and utilizes water as coolant. The facility was equipped with instrumentation to measure temperatures and flow rates and a general verification was completed during the shakedown. A model of the experimental facility was prepared using RELAP5-3D and simulations were performed to validate the scaling procedure. The overall behavior of the facility met the expectations. The steady-state condition was achieved and the facility capabilities were confirmed to be very promising in performing additional experimental tests, including flow visualization, and produce data for code validation. The experimental data produced during the steady-state run were successfully compared with the simulation results obtained using RELAP5-3D, confirming the capabilities of the system code of simulating the thermal-hydraulic phenomena occurring in the reactor cavity

Experimental Study of the Thermal-Hydraulic Phenomena in the Reactor Cavity Cooling System and Analysis of the Effects of Graphite Dispersion

An experimental activity was performed to observe and study the effects of graphite dispersion and deposition on thermal hydraulic phenomena in a Reactor Cavity Cooling System (RCCS). The small scale RCCS experimental facility (16.5cm x 16.5cm x 30.4cm) used for this activity represents half of the reactor cavity with an electrically heated vessel. Water flowing through five vertical pipes removes the heat produced in the vessel and releases it in the environment by mixing with cold water in a large tank. PIV technique was used to study the velocity field of the air inside the cavity. A set of 52 thermocouples was installed in the facility to monitor the temperature profiles of the vessel and pipes walls and air. 10g of a fine graphite powder (particle size average 2 [mu]m) were injected into the cavity through a spraying nozzle placed at the bottom of the vessel. Temperatures and air velocity field were recorded and compared with the measurements obtained before the graphite dispersion, showing a decrease of the temperature surfaces which was related to an increase in their emissivity. The results contribute to the understanding of the RCCS capability in case of an accident scenario

Preconceptual Design of Multifunctional Gas-Cooled Cartridge Loop for the Versatile Test Reactor: Instrumentation and Measurement—Part II

An integrated effort by the Versatile Test Reactor (VTR) Gas-Cooled Fast Reactor (GFR) Team to develop an experiment vehicle or extended-length test assembly for the VTR experiments is led by Idaho National Laboratory and supported by an industrial partner, General Atomics, and university partners, including Texas A&M University, University of Michigan, Oregon State University, University of Houston, and University of Idaho. The focus of the effort is to design a helium gas-cooled cartridge loop (GCL) to assist with the testing of fuels, materials, and instrumentation to further support development of advanced reactor systems. This study is divided into two parts. Part I provides the functional requirements and critical irradiation data needs for advancing gas-cooled fast reactor (GFR) technologies. The objective of Part I is to describe the overall preliminary conceptual design of the VTR helium cartridge loop, the design of a fission product venting system, thermal-hydraulic effects of flow direction, and gamma-heating generation in the cartridge. This paper, Part II, includes the measurement techniques being developed to measure the thermophysical properties of the different materials that make up the GCL, as well as the instrumentation and control system within the cartridge required for advancing GFR technologies. The purpose of Part II is to describe the functionality and efficacy of the measuring systems being developed to support the GCL. These systems include (a) a unique measurement platform that joins ion irradiation and a laser beam with an infrared camera and X-ray detection equipment developed and used to investigate more accurately and efficiently the influence of radiation and fission gases on the material properties under high temperatures; (b) a laser-induced breakdown spectroscopy to demonstrate its capability of monitoring possible fuel failure by detecting sub–part-per-million levels of xenon in the helium coolant stream, providing experimental data to better understand the interactions of fuel elements and coolant at high temperature, pressure, and fast neutron flux; (c) fiber-optic sensors with the ability to measure both the temperature demonstrated using a three-dimensional printed heat exchanger and, potentially, the strain in harsh environments; and (d) surface emissivity measurement test rigs to understand the effect of temperature, radiation, and surface finish on the silicon carbide cladding surface emissivity. Additional analyses and development, as well as integrated out-of-pile testing, are planned to demonstrate and validate the accuracy of the measuring systems and instrumentation in a more prototypic environment prior to their implementation into the VTRISSN:0029-5639ISSN:1943-748

Preconceptual Design of Multifunctional Gas-Cooled Cartridge Loop for the Versatile Test Reactor—Part I

An integrated effort by the Versatile Test Reactor (VTR) Gas-Cooled Fast Reactor (GFR) Team to develop an experiment vehicle or extended-length test assembly for the VTR experiments is led by the Idaho National Laboratory and supported by an industrial partner, General Atomics, and university partners, including Texas A&M University, University of Michigan, Oregon State University, University of Houston, and University of Idaho. The overall focus of the effort is to design a helium gas-cooled cartridge loop (GCL) to assist with the testing of fuels, materials, and instrumentation to further support development of advanced reactor systems. This study is divided into two parts. Part I provides the GCL functional requirements and critical irradiation data needs for advancing GFR technologies. Part II includes the measurement techniques developed to measure the thermophysical properties of the different materials in the GCL, as well as the functionality and efficacy of these instrumentation and control systems within the GCL. This paper, Part I, describes the overall preliminary conceptual design of the VTR helium cartridge loop, the design of a fission product venting system, the thermal-hydraulic effects of flow direction, and gamma-heating generation in the cartridge. This paper also describes a three-dimensional computational fluid dynamics study that was carried out to examine the effects of the helium flow direction in the GCL on its thermal-hydraulic characteristics, engineering feasibility, and in-VTR experiment design. Both steady-state operation and a transient scenario (pressurized loss of forced circulation) were analyzed for the upward and downward helium flow options in the test article section in the GCL to provide quantitative data for selection of the helium flow direction. Additional analyses and development, as well as integrated out-of-pile testing, are planned to demonstrate and verify the performance of the GCL prior to insertion into the VTR.ISSN:0029-5639ISSN:1943-748