Radioactivity Concentration Measurement of ⁸⁵Kr Using Length-compensated Internal Gas Proportional Counting Method

The radioactivity concentration absolute measurement of radioactive noble gas is the basis for the transmission of its quantity value. In order to determinate the value of ⁸⁵Kr radioactivity concentration, the absolute measurement of ⁸⁵Kr radioactivity concentration was carried out based on the length-compensated internal gas proportional counting method. The results show that the radioactivity concentration of ⁸⁵Kr is 10.64 Bq/mL at pressure of 56.15 kPa and working voltage of 1 675 V and 1 700 V, and the combined standard uncertainty is 0.60%. The combined standard uncertainty is equivalent to the result reported by the international advanced nuclide metrology laboratory.