Motoo Fumizawa

Visualization and Numerical Simulation of Exchange Flow in Density Different Gases

Buoyancy-driven exchange flows of helium-air through inclined a narrow tube was investigated. Exchange flows may occur following the opening of a window for ventilation, as well as when a pipe ruptures in a high temperature gas-cooled reactor. The experiment in this paper was carried out in a test chamber filled with helium and the flow was visualized using the smoke wire method. A high-speed camera recorded the flow behavior. The image of the flow was transferred to digital data, and the slow flow velocity, i.e. micro flow rate was measured by PIV software. Numerical simulation was carried out by the code of moving particle method with Lagrange method.Copyright

Thermal Evaluation for a Ultra High Temperature Reactor With Pebble Type Fuels

This study presents a predictive thermal-hydraulic analysis with packed spheres in a nuclear gas-cooled reactor core. The predictive analysis considering the effects of high power density and the some porosity value were applied as a design condition for an Ultra High Temperature Reactor (UHTR). The thermal-hydraulic computer code was developed and identified as PEBTEMP. The highest outlet coolant temperature of 1316 °C was achieved in the case of an UHTREX at LASL, which was a small scale UHTR using hollow-rod as a fuel element. In the present study, the fuel was changed to a pebble type, a porous media. Several calculation based on HTGR-GT300 through GT600 were 4.8 w/cm3 through 9.6 w/cm3 respectively. As a result, the relation between the fuel temperature and the power density was obtained under the different system pressure and coolant outlet temperature. Finally, available design conditions are selected.© 2009 ASME

Helium-Air Exchange Flow Rate Measurement Through a Small Opening

Buoyancy-driven counter flows of helium-air were investigated through horizontal and inclined small openings. Counter flows may occur following a window opening as ventilation, fire in the room as well as a pipe rupture accident in a high temperature gas-cooled nuclear reactor [1]. The counter flows also occur following the fusion reactor accident of LOVA that takes place through the breaches of vacuum vessel penetration duct [2]. The experiment has carried out by a test chamber filled with helium and flow was visualized by the smoke wire method. The flow behavior has recorded by a high-speed camera with a computer system. The image of the flow was transferred to the digital data, thus the flow velocity was measured by PTV software. The mass fraction in the test chamber was measured by electronic balance. The detected data was arranged by the densimetric Floude number of the counter flow rate that derived from the dimensional analysis. The method of mass increment was developed and applied to measure the counter flow rate. By removing the cover plate placed on the top of the opening, the counter flow initiated. Air enters the test chamber and the mass of the gas mixture in the test chamber increased. The volumetric counter flow rate was evaluated from the mass increment data. In the case of inclination openings, the results of both methods were compared. The inclination angle for maximum densimetric Floude number decreased with increasing length-to-diameter ratio of the opening. For a horizontal opening, the results from the method of mass increment agreed with those obtained by other authors for a water-brine system.Copyright

Thermal Hydraulics and Thermal Radiation for Ultra High Temperature Gas-Cooled Nuclear Reactor With Pebble Type Fuel

This report presents the results of thermal-hydraulic analysis for the Ultra High Temperature Reactor Experiment (UHTREX) as well as the modular Gas Turbine High Temperature Reactor 300 MWth (HTGR-GT300) loaded with Pebble Type Fuel. A thermal-hydraulic computer code was developed that was named PEBTEMP. In order to compare the present PBR case with UHTREX, a calculation for HTGR-GT300 was carried out in the similar conditions with UHTREX i.e. the inlet coolant temperature of 871°C, system pressure of 3.45 MPa and power density of 1.3 W/cm3 . The hot channel factor of 1.0, 1.1, 1.2, and 1.3 are chosen for the present calculation. As the result, the fuel temperature for the present PBR case is extremely low when compared to the UHTREX case. The evaluated temperature is compared to the data of conventional optical high temperature camera using the principle of the thermal radiation flux dependence upon surface temperature. Therefore, the present PBR system design will be named as NUHTREX i.e. New UHTREX. The evaluated temperature is compared to the data of conventional optical high temperature camera using the principle of the thermal radiation flux dependence upon surface temperature.Copyright