Speaker
Description
A liquid mercury target system for the pulsed spallation neutron source is in operation at the Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). During the operation, mercury itself act as a coolant and circulates through the system consisting of the target vessel, heat exchanger and pump to remove the heat from the high-energy proton beam injection. In May 2024, the MLF achieved its operational goal of 1 MW at 25 Hz for two months in user operation. During the FY2024 summer outage period, in addition to the routine damage inspection of the beam entrance portion of the used target vessel by target cutting, the pump in the mercury circulation system was replaced by remote handling for the first time due to a decrease in insulation resistance. Replacement work was completed successfully, however, after resuming operation, we found the tiny leakage of radioactive gas from the 150A pump flanges. The issue was solved by replacing the metal seal of flanges again by optimized procedure based on mockup tests with suspending user operation.
In the presentation, details of the pump replacement work and optimization of the procedure for the metal seal replacement by remote handling will be reported.