Shaft sealing structure and reactor coolant pump

A shaft sealing structure for a pump, comprising:

• an annular groove;
• a seal ring that has abutment portions each having a shape obtained by cutting the seal ring along an axial direction and that is installed with the abutment portions in the annular groove that is provided around a shaft in a ring-like manner;
• a supporting member that is provided in the seal ring along a circumferential direction of the shaft, that is moved toward a center of the shaft while being brought into contact with the seal ring, and that is moved relative to the seal ring along the circumferential direction of the shaft;
• and
• a first driving part that is connected to the supporting member between the abutment portions and that presses the supporting member toward the center of the shaft when the temperature rises to a temperature higher than that during normal operation,
• wherein the seal ring is fixed at a position separated from the shaft during the normal operation and is moved by the supporting member toward the center of the shaft when the temperature rises to a temperature higher than that during the normal operation.