The Preparation and Welding of ⁸⁵Kr Thickness Gauge Source

In order to ensure the sealing quality of ⁸⁵Kr thickness gauge source, reasonable structural design, appropriate welding process and inspection processes are required. The connection between copper tube and shell is vacuum brazing, and the optimized vacuum brazing parameters are as follows: the temperature is about 900 ℃ and the time is about 30 min; the connection between source window and shell is electron beam welding, the optimized parameters are 7 mA and 13 mm/s for welding through experiment; the connection between source back cover and shell is laser welding, the parameters of laser welding are 180~185 W electric power and 2 mm/s speed. The inspection processes include helium mass spectrometry leak detection, radioactive active and leak method of radioactive gas. The results show that ⁸⁵Kr thickness gauge source has a leak mass detection rate of less than 1.0×10^-9 Pa·m³·s^-1, the radioactive gas inspection was not exceed 4 kBq /24 h, meeting the requirements of other radioactive gas inspection methods in GB/T 15849—1995. Through metallographic test analysis, no obvious welding defects such as crack, incomplete penetration and incomplete fusion were found in the welds with optimized parameters, and the maximum welding depth was about 0.73 mm.