Patent Number: 046860770
Section: abstract

The reactor has a pressure vessel receiving a coolant and a reactor core. The core has vertically movable control rods to which absorber rods are secured. Each tubular control rod extends, with the interposition of an annular gap, around an immobile guide rod which is also tubular and which is longer than the control rod. To move the control rods, coolant is supplied from the pressure vessel under pressure to the interior of the guide rods. The annular chamber communicates by way of communicating bores with the interior of the associated guide rod and, by way of at least two annular restrictions providing different restrictors with the pressure vessel interior. One restrictor is disposed at the top end of the associated control rod and the other restrictor at the bottom end thereof.. The control rods move axially upwards in response to an increasing quantity of coolant in the guide rod interiors and downwards in response to a decreasing quantity of coolant in the guide rod interiors.