Control rod damping system
A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.
1 . A nuclear reactor having a reactor vessel housing a reactor core, the nuclear reactor comprising:
a riser section submerged in a primary coolant;
a baffle plate forming a support member positioned within the reactor vessel above the riser section and including an opening, the baffle plate including an upper surface and a lower surface, wherein the opening is formed between the upper surface and the lower surface;
a drive shaft extending through the opening, wherein the drive shaft includes:
an upper portion positioned to be coupled to a drive mechanism, wherein the upper portion has a first diameter;
a lower portion positioned to be coupled to a control rod assembly configured to control a nuclear reaction of the reactor core, wherein the lower portion has a second diameter less than the first diameter; and
a damping portion positioned between the upper portion and the lower portion, wherein the damping portion has an upper end portion and a lower end portion, and wherein the damping portion has the first diameter at the upper end portion and the second diameter at the lower end portion,
wherein the opening has a third diameter at the upper surface and a fourth diameter at the lower surface such that the third diameter is larger than the second diameter and the fourth diameter is less than the first diameter, and wherein the lower surface of the baffle plate is configured to redirect a flow of the primary coolant exiting the riser section toward a lower end of the reactor vessel.
2 . The nuclear reactor of claim 1 wherein the damping portion is configured to be positioned outside the opening and above the support member during normal operation of the reactor core.
3 . The nuclear reactor of claim 1 wherein the damping portion is configured to enter the opening during a scram operation.
4 . The nuclear reactor of claim 1 wherein the damping portion is configured to be positioned outside the opening and above the support member during normal operation of the reactor core, and wherein the damping portion is configured to enter the opening during a scram operation.
5 . The nuclear reactor of claim 1 wherein a width of the damping portion continuously decreases from the upper end portion to the lower end portion.
6 . A nuclear reactor having a reactor vessel housing a reactor core, the nuclear reactor comprising:
a drive shaft, wherein the drive shaft includes:
an upper portion positioned to be coupled to a drive mechanism;
a lower portion positioned to be coupled to a control rod assembly configured to control a nuclear reaction of the reactor core; and
a damping portion positioned between the upper portion and the lower portion, wherein the damping portion has a first conical shape that decreases in diameter in a direction from the upper portion toward the lower portion;
a riser section submerged in a primary coolant; and
a baffle plate forming a support member positioned within the reactor vessel above the riser section and including an opening formed between an upper surface of the baffle plate and a lower surface of the baffle plate, wherein the opening is positioned to receive the drive shaft therethrough, and wherein the opening has a second conical shape that decreases in diameter in the direction from the upper portion toward the lower portion, and wherein the lower surface of the baffle plate is configured to redirect a flow of the primary coolant exiting the riser section toward a lower end of the reactor vessel.
7 . The nuclear reactor of claim 6 wherein the first conical shape is the same as the second conical shape.
8 . The nuclear reactor of claim 6 wherein the damping portion is configured to be positioned outside the opening and above the support member during normal operation of the reactor core.
9 . The nuclear reactor of claim 6 wherein the damping portion is configured to enter the opening during a scram operation.
10 . A nuclear reactor system, comprising:
a reactor vessel;
a coolant positioned within the reactor vessel;
a reactor core positioned within the reactor vessel and configured to heat the coolant;
a riser positioned within the reactor vessel and configured to direct a portion of the coolant heated by the reactor core upward away from the reactor core;
a baffle plate forming a support member positioned within the reactor vessel above the riser, the baffle plate including an opening formed between an upper surface of the baffle plate and a lower surface of the baffle plate, wherein a width of the opening decreases from the upper surface of the baffle plate to the lower surface of the baffle plate, and wherein the lower surface of the baffle plate is configured to redirect a flow of the coolant exiting the riser toward a lower end of the reactor vessel; and
a drive shaft extending through the opening, wherein the drive shaft includes;
an upper portion positioned to be coupled to a drive mechanism, wherein the upper portion has a first diameter;
a lower portion positioned to be coupled to a control rod assembly configured to control a nuclear reaction of the reactor core, wherein the lower portion has a second diameter less than the first diameter; and
a damping portion positioned between the upper portion and the lower portion, wherein the damping portion has an upper end portion and a lower end portion, and wherein a width of the damping portion decreases from the upper end portion to the lower end portion.
11 . The nuclear reactor system of claim 10 wherein the drive mechanism is positioned above the baffle plate.