Continuous running test of radiation resistance motor driving equipment under high gamma ray irradiation

Obara, Kenjiro; Kakudate, Satoshi; Yagi, Toshiaki; Morishita, Norio; Shibanuma, Kiyoshi

The components in the vacuum vessel of ITER (International Thermonuclear Experimental Reactor), e.g. blanket and divertor, are replaced using the dedicated remote handling systems. The environment conditions inside the vacuum vessel during the operation are temperature of 50C, gamma ray radiation and air or inert gas atmosphere at 1 atm. ; therefore multiple elements are required as durability of the remote handling systems. In addition, the remote handling system it is desired to be able to operate over a long time. The radiation resistance motor driving equipment, which comprises parts with different radiation resistance levels, was designed simulating mechanisms of the ITER remote handling systems. The equipment being the servomotor, turns the weight (dummy load) of 8 kgf and controls, and continuous running test under high gamma ray irradiation was started from March, 2000. Irradiation conditions on the test were the dose rate of 3.6 kGy/h, the target accumulation dose of 30 MGy at the minimum. The irradiation test was performed two stages which was divided by overhaul of the equipment. The achieved accumulation dose and running time in these stages were approximately 47.6 MGy/13,200 hours and 23.9 MGy/6,640 hours, respectively. As a result, it has been confirmed that sufficient radiation resistance of the equipment, which is required from the latest dose rate of 0.5 kGy/h inside the vacuum vessel was achieved. In this report, we describe design conditions of the equipment and the results of the 1st and 2nd irradiation tests and the overhaul after the 1st irradiation test.