One-Dimensional Activation Analysis of Vacuum Vessel of JT-60U with Deuterium Gas Discharges.

Abstract Identification of radionuclides and evaluation of dose rate level around a vacuum vessel of JT-60U tokamak device have been made. A one-dimensional calculation code was employed in this work. Radionuclides of 56Mn (High-Mn steel of toroidal field coil case), 58Co (Inconel-625 vessel) and 60Co (SS-316 material of first wall) appeared after shutdown of operation with deuterium gases. Cobalt-58 and 60Co with long half-life time contribute to the dose rate on the vessel by 7 to 3 proportion. The one-dimensional calculation provided a sufficient prediction for the dose rate on Inconel vessel of JT-60U, in which the activation property is mainly determined by 58Co generated via threshold neutron reactions. The results calculated for the vessel dose rate showed a good agreement with data measured for the first 80 D-D operation weeks. KEYWORDS: JT-60U tokamakdeuterium operationcobalt 60cobalt 58manganese 56radioactivitydose ratesone-dimensional codeANISNTHIDACINAC