Corrugated thimble tube for controlling control rod descent in nuclear reactor
AssigneeUop LLC
InventorHoward J. Luetzow
Life of this patent
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Abstract
Improved shock absorber for slowing down the descent of a control rod in a liquid cooled reactor core at a controlled rate uses a thimble tube which has a corrugated section at its lower end to distribute the control rod deceleration forces over an extended distance in a "scram" situation. In a preferred embodiment, the corrugations have a lesser internal diameter at the lower end of the thimble tube than at the top to increase the rate of deceleration as the control rod aproaches the bottom of the core. In several modifications, the corrugation pitch and/or depth is varied over the length of the corrugated surface.
Claims2
In a shock absorber for a control rod used in a nuclear reactor cooled by liquid, the improvement comprising a guide or thimble tube for said control rod, said thimble tube being internally helically corrugated along at least one extended axial portion near its lower end, said helically corrugated portion having internal diameters of smaller distance at the lower end than at the upper end of said corrugated portion and a progressively smaller pitch of corrugation from the top to the bottom of said corrugated portion and cooperating with the outer wall portion of the lower end of said control rod to brake the descent of said control rod with progressively increasing hydraulic restraining force provided by the liquid coolant in the annular space between the thimble or guide tube and said control rod as each adjacent progressively smaller section of corrugation is encountered.
Dependencies are inferred from the claim text.