Control rod damping system

A control rod for inserting into a guide tube of a nuclear reactor fuel assembly, comprising:

• a damping section including an upper portion and a lower portion extending from the upper portion, wherein the upper portion has a first diameter, wherein the damping section is configured to be positioned above the guide tube during normal operation of the nuclear reactor fuel assembly and to enter the guide tube only during a SCRAM operation of the nuclear reactor fuel assembly;
• a lower section extending from the lower portion of the damping section, wherein the lower section has a second diameter, and wherein the lower portion of the damping section has a third diameter that decreases from the first diameter to the second diameter in a direction from the upper portion toward the lower section;
• and
• a neutron-absorbing material positioned at least partially in the lower section.

A nuclear reactor system, comprising:

• a nuclear core;
• a guide tube extending at least partially into the nuclear core;
• a control rod including—
• a damping section including an upper portion and a lower portion extending from the upper portion, wherein the upper portion has a first diameter;
• a lower section extending from the lower portion of the damping section, wherein the lower section has a second diameter, and wherein the lower portion of the damping section has a third diameter that decreases from the first diameter to the second diameter in a direction from the upper portion toward the lower section;
• and
• an active material positioned at least partially in the lower section and configured to control a fission rate of the nuclear core;
• and
• a control rod drive mechanism (CRDM) coupled to the control rod and configured to move the control rod relative to the guide tube such that the damping section is positioned above the guide tube during normal operation of the nuclear reactor system and enters the guide tube only during a SCRAM operation of the nuclear reactor system.