44
2 Experiments in Pebble Flows
Fig. 2.1 Schematic drawing of the experiment apparatus
is 30
◦ . The center of the base is located at a single discharge hole with a diameter of
120 mm, the same size as that of the 1/5 scaled discharge hole of the actual reactor
core. Accordingly, the depth of the experimental vessel is set equal to the diameter
of the discharge hole, namely 120 mm.
Black and colorless glass pebbles with identical diameters of 12 mm, which are
also 1/5 of the diameter of the pebble elements in a practical reactor, are respectively
utilized to simulate graphite and fuel pebbles. Note that the surface roughness of
the pebbles is different from that of the pebble elements in a practical reactor core.
Various surface roughness should be chosen to cover that of an actual reactor core
in a future study.
The experimental vessel is filled with pebbles up to the required height, thus
forming the pebble bed. The pebble bed is made up of two sections. The lower
section is the base extending from the vertex of the vessel base to the top of the
conical base of the vessel. The upper section is a rectangular area extending from
the top of the vessel base to the top of the pebble bed.
The pebble bed runs in the mode of recirculation with pebbles moving outside the
vessel. Meanwhile, new pebbles are reloaded. The recirculation of the pebble bed is
controlled by three loading transport units and one discharge transport unit. Pebbles
to be loaded are pre-filled in three holders connected to three conveyors. Pebbles
are transported by the conveyors and then loaded into the pebble bed one by one
at a controlled rate, through three inlet tubes symmetrically located right above the
vessel. A discharge transport unit placed beneath the discharge hole allows pebbles to
2 Experiments in Pebble Flows
Fig. 2.1 Schematic drawing of the experiment apparatus
is 30
◦ . The center of the base is located at a single discharge hole with a diameter of
120 mm, the same size as that of the 1/5 scaled discharge hole of the actual reactor
core. Accordingly, the depth of the experimental vessel is set equal to the diameter
of the discharge hole, namely 120 mm.
Black and colorless glass pebbles with identical diameters of 12 mm, which are
also 1/5 of the diameter of the pebble elements in a practical reactor, are respectively
utilized to simulate graphite and fuel pebbles. Note that the surface roughness of
the pebbles is different from that of the pebble elements in a practical reactor core.
Various surface roughness should be chosen to cover that of an actual reactor core
in a future study.
The experimental vessel is filled with pebbles up to the required height, thus
forming the pebble bed. The pebble bed is made up of two sections. The lower
section is the base extending from the vertex of the vessel base to the top of the
conical base of the vessel. The upper section is a rectangular area extending from
the top of the vessel base to the top of the pebble bed.
The pebble bed runs in the mode of recirculation with pebbles moving outside the
vessel. Meanwhile, new pebbles are reloaded. The recirculation of the pebble bed is
controlled by three loading transport units and one discharge transport unit. Pebbles
to be loaded are pre-filled in three holders connected to three conveyors. Pebbles
are transported by the conveyors and then loaded into the pebble bed one by one
at a controlled rate, through three inlet tubes symmetrically located right above the
vessel. A discharge transport unit placed beneath the discharge hole allows pebbles to