Centrifuge launcher

Cryostat system

As concerns the pellet production, first the pellet material is frozen in the extrusion cryostat at a temperature of around 4 K. The solid fuel material is then conditioned by varying the temperature and pressure. By applying about 7 K for H2 and 13 K for D2 and a pressure from 180 to 200 bar, the material is extruded through the nozzle, which determines the quadratic cross-section of the fuel rod produced. This 192 mm long rod is now stored at the appropriate temperature (4 K for H2 and 6 K for D2) in the storage cryostat, which contains a separate channel for each different pellet size. The rigid solid (WEG) fuel rod is pushed by a lever driven by a stepping motor through the exit of the storage cryostat. The number of steps determines the pellet length; That is to say, the length of the pellet can only be increased by steps of 0.25 mm. The extrusion nozzle and the storage cryostat can both be moved pneumatically inside the vaccum system to select the pellet size.

The pellet feed-in procedure in the centrifuge turned out to be critical for the pellet injection. It can decisively determine the angle at the exit of the centrifuge. Futhermore, pellet impacts within the rotating acceleration guide has to be limited to velocities smaller than 50 m/s. This value limits the transversal velocity for a given feed-in radius with respect to the acceleration path.

If a pellet request signal arrives, first the step motor pushes out part of the fuel rod the preselected length . Then, the electronic control system brings the cutting knife into action with a delay time in order to synchronize the cutting and the centrifuge rotation so that it can feed in the pellet at the exact time. The cutter itself moves perpendicularly to the pushing direction of the rod and accelerates the pellets to velocities of about 4 m/s. It is thus ensured that the pellets cover the distance of 15 mm straight down to the acceleration guide within one revolution of the centrifuge.

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