Tritium contamination and decontamination study on materials for ITER remote handling equipment

Several materials, lenses, dry bearings and cables were exposed to a tritia ted moisture environment to study the behavior of tritium contamination on candidate materials for ITER remote handling equipment. To optimize the tri tium removal procedure, decontamination experiments using a gas purge with three different moisture concentrations were also performed. The surface tr itium concentrations of CeO2 containing alkaline barium glass (NB), CeO2 co ntaining lead glass (LX) and synthetic quartz (Quartz) after the exposure e xperiments were 7.80, 10.94 and 0.67 Bq/cm(2), respectively. It was found t hat the tritium concentration was influenced by the compositions of the mat erials. The concentrations of tritium on type 831 (solid lubrication materi al: graphite) and type 237 (solid lubrication material: tungsten disulfate) dry bearings after the exposure experiments were 89.80 and 31.78 Bq/cm(2), respectively. The tritium concentration in an electric cable tested was 50 14 Bq/g after HTO moisture exposure. The tritium concentrations of lenses, LX, as typical experimental results, decreased to 2.72, 4.42 and 3.89 Bq/cm (2) by purging with the moist air, dry air and dry N-2, respectively. The t ritium concentrations of dry bearing, type 831 dropped to 6.61, 9.42 and 10 .16 Bq/cm(2) by the same three decontamination treatments, respectively. A large decontamination factor of 13.6 was achieved in the case of type 831 d ry bearing with a moist air purge. The tritium concentration in the electri c cable was 3236 Bq/g after a moist air purge, and the decontamination fact or was as low as 1.6. Therefore, decontamination with a moist air purge is not so effective for the electric cable. (C) 2001 0Elsevier Science B.V. Al l rights reserved.