Patent Number: 043495079
Section: claims

1. A drive for an absorber rod of a nuclear reactor comprising: a drive chamber mounted within the pressure vessel of a nuclear power plant,  a drive piston mounted within said drive chamber for movement along its longitudinal axis,  an absorber rod fixedly attached at one end to said drive piston and extending outside said drive chamber to a terminating surface at its other end,  an equalizing surface fixedly attached to said drive piston, transverse to said longitudinal axis and facing the opposite direction of said terminating surface,  means for controlled movement of said drive piston within said drive chamber independent of the medium contained within the pressure vessel,  wherein both said absorber rod terminating surface and said equalizing surface are exposed to the medium contained within the pressure vessel.  a drive chamber mounted within the pressure vessel of a nuclear power plant,  a drive piston mounted within said drive chamber for movement along its longitudinal axis,  a hollow absorber rod fixedly attached at one end to said drive piston and extending outside said drive chamber to a terminating surface at its other end,  an equalizing surface fixedly attached to said drive piston, transverse to said longitudinal axis and facing the opposite direction of said terminating surface,  means for controlled movement of said drive piston within said drive chamber independent of the medium contained within the pressure vessel,  means for cooling said absorber rod with a cooling medium flowing within said hollow absorber rod,  wherein said absorber rod terminating surface is exposed to the medium contained within the pressure vessel and said equalizing surface is exposed to said cooling medium.  equalizing the inner driving forces contained within the reactor vessel acting on said piston drive in the axial direction, and  applying force independent of said equalizing forces to said drive piston while maintaining the equalized inner drive forces constant. 2. The drive of claim 1 wherein the means for controlled movement of said drive piston is a fluid medium flowing through a first conduit into said drive chamber to effect movement of said drive piston in one direction and flowing through a second conduit into said drive chamber to effect movement of said drive in the opposite direction. 3. The drive of claim 2 wherein said drive chamber is sealed from the medium contained within the pressure vessel by sealing gaskets and means for isolation of medium leaking past said sealing gaskets. 4. The drive of claim 3 wherein said equalizing surface is attached to a member extending in the opposite direction of said absorber rod. 5. The drive of claim 4 wherein said exposed surface area of said equalizing surface equals said exposed surface area of said terminating surface. 6. A drive for an absorber rod of a nuclear reactor comprising: 7. The drive of claim 6 wherein the means for controlled movement of said drive piston is a fluid medium flowing through a first conduit into said drive chamber to effect movement of said drive piston in one direction and flowing through a second conduit into said drive chamber to effect movement of said drive in the opposite direction. 8. The drive of claim 7 wherein said equalizing surface is the inner surface of said hollow absorber rod. 9. A method for controlling a piston drive for an absorber rod of a high temperature nuclear reactor comprising: 10. The method fo claim 9 wherein said nuclear reactor is a gas cooled high temperature reactor and said equalizing step comprises directing the medium of a pressure vessel against an equalizing surface of an absorber unit and a terminating surface of an absorber rod said equalizing surface and terminating surface facing opposite directions. 11. The method of claim 9 or 10 wherein said nuclear reactor is a gas cooled high temperature reactor and said medium is the cooling medium. 12. The method of claim 11 wherein said step of applying an independent force to said piston drive comprises flowing a fluid medium through a conduit into a drive chamber housing said drive piston and sealed from said medium of the pressure vessel.