Irradiation Tests of the Sleeve for the Telescopic Arm of the ITER Blanket Remote Handling System

The ITER blanket remote handling system (BRHS) must operate with high precision within the confines of the ITER vacuum vessel, which will become a gamma-ray environment filled with radioactive dust. The main structural component of the BRHS, a telescopic arm, will be covered with a sleeve that must prevent not only the radioactive dust from infiltrating into the system but also lubricant from leaking out into the vacuum vessel. Verifying the radiation resistance of this sleeve is crucial and will ultimately affect the operation scenarios and timing of preventive maintenance for the BRHS. Thermoplastic polyurethane was selected as a candidate material for the sleeve. This paper presents the results of gamma-ray irradiation tests up to either 1 MGy or 2 MGy for polyurethane sheets and the results of subsequent bending, tensile, and hardness tests. Based on the results of these tests, mock-ups of the sleeve were manufactured and were also irradiated up to either 1 MGy or 2 MGy, after which the mock-ups underwent expansion and contraction tests to simulate actual operations in ITER. We have concluded from conservative estimates that, although these polyurethane sleeve mock-ups have over 1 MGy of radiation resistance, the sleeves of the BRHS should be replaced at 1 MGy.