| High-temperature gas-cooled reactor and fluoride salt-cooled high-temperature reactor are Generation IV advanced reactors and have designs that adopt a pebble bed core.When a reactor that has a pebble bed core is operating,a large quantity of fuel pebbles pass through the core and form a pebble flow.The pebble flow has significant impacts on the power distribution,temperature distribution and fuel burnup of the reactor.Thus,understanding the pebble flow is the basis of the design of the pebble bed core.Several important phenomena of the pebble flow,such as flow lines,flow mixing,residence time,pebble jam,pebble sliding and rotating are yet to be fully understood.It is a common practice to use a surrogate core and surrogate pebbles to study the pebble flow to avoid the harsh environment in a real reactor core.The surrogate experiment can simulate the real pebble flow in the reactor core when a scaling analysis is conducted correctly.And the cost of the surrogate experiment is low.The author has developed a smart detection system to study the pebble flow.Microchips are implanted into the surrogate pebbles so that the pebbles can record their motion when flowing with other pebbles.The recorded information can be stored locally and wirelessly transferred in real time.The smart system is capable of measuring angular velocity,acceleration,gesture,rotation angle and temperature of the pebbles,and will not disturb the pebble flow when performing measurements.Preliminary tests show that the accuracy of the measurements is within three percent.Using the smart system and a modular pebble bed high-temperature reactor as a model,the author studied the correlation between the residence time and the initial seeding positions of the surrogate pebbles in the surrogate core,quantified the angular velocities and the accumulated rotation angles of the pebbles,and discussed the contribution to the quantity of the graphite dust from the fuel pebble rotation. |
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