Overview:

The Soft Pellet Loader automates the transfer of green nuclear pellets to steel sintering "boats" in a safe and organized manner.

Process Description:

Green pellets are dispensed from a sintering press onto a stainless steel conveyor belt. The pellets, which are cylindrical in shape, are arrayed end to end. The pellet stream is passed through a short crowding section into the row singulator.

The pellets enter the row singulator on the stainless steel belt. As the row fills, the pellets stack up, one against another.  When a row is filled, a sensor detects that the row is complete, and the stack of pellets are rolled off the conveyor belt into a grooved tray.

As each row of the tray is filled, the tray indexes and an empty row is exposed.  When each row of the tray is filled, the entire layer is picked up using a high-flow vacuum head.  The layer is then placed into the sintering boat and released. The highly organized stack is then fired in the sintering boat as it passes through the firing oven.

Technical Challenge:

The most serious challenge in this project involved the high-flow vacuum head, and the entire strategy of picking up a complete layer of pellets. Nuclear fuel is very dense, and an 8" X 11" layer requires a serious amount of vacuum flow to fix it to the gripper. The project team originally considered a plate which was shaped to the curvature of the individual pellets, but the variety of sizes made this approach impractical. A simple grooved plate was attempted, and initially failed when combined with a regenerative blower as the vacuum source.  The blower was replaced with a Piab vacuum venture, which provided good negative pressure at high-flow rates, and gripper worked. The final gripper design was able to successfully handle the entire range of pellets planned for the machine.