Design of an in-situ CONOSEAL sealing surface repairing equipment for nuclear reactor thermocouple column

The CONOSEAL seal for the nuclear reactor thermocouple column belongs to the boundary seal of the primary circuit. When the sealing surface suffers from scratches, damages, or other defects, it will directly affect the sealing reliability and result in leakage. However, replacing the thermocouple column is a complex process with huge workload and long period. To address these issues, an in-situ reactor thermocouple column CONOSEAL sealing surface repairing device is designed. Due to the in-situ structure and operation conditions, the repairing device is designed in a compact modular and light weighted manner. Repair tests have been conducted on a thermocouple column to verify the repair capability of the CONOSEAL sealing surface repairing device. A prototype of cycling test platform is established to simulate the in-situ conditions of the thermocouple column. The CONOSEAL sealing surface is repaired to achieve a surface roughness of Ra 1.712 μm and pressure tests according to RCC-M standard and thermal cycling tests are both performed on the thermocouple column. For the pressure tests, the measured pressure drops do not exceed 0.2 MPa during a 10 min pressure maintenance. In the thermal cycling tests, the pressure is maintained for 10 min under the pressure of 15.5 MPa and the temperature is 310 ℃ and there are no leaks. The test results show that the dimensions and roughness of the sealing surface after repairing by the repair device meet the requirements of the in-situ operation conditions. This verifies the capability of the CONOSEAL sealing surface repairing equipment.