A radon exhalation rate control method, which is applied to a calibration device for a radon exhalation rate measuring instrument, comprising a diffusive solid radon source, a solid radon source containing chamber, a radon accumulation chamber, a diffusion medium and an air pressure balancing device, wherein
- the radon accumulation chamber is shaped as an inverted cone, a circular cone opening at a bottom of the radon accumulation chamber is connected with the solid radon source containing chamber, a top of the radon accumulation chamber is connected with the diffusion medium, the diffusion medium comprises a plasterboard and a high-density wood board, the plasterboard is located above the radon accumulation chamber, the high-density wood board is overlapped on the plasterboard, the air pressure balancing device is connected with the radon accumulation chamber, and configured to maintain air pressure dynamic balance between the radon accumulation chamber and ambient atmosphere;
- a radon exhalation rate of a surface of the diffusion medium is determined according to a diffusion coefficient of radon in the diffusion medium, a thickness of a diffusion medium layer, and an activity of a solid radon source in the solid radon source containing chamber;
- the radon exhalation rate is adjusted by changing the activity of the solid radon source in the solid radon source containing chamber and the thickness of the diffusion medium layer,
- the radon exhalation rate control method comprising:
- adjusting the radon exhalation rate of the calibration device by changing the activity of the solid radon source in the radon accumulation chamber and the thickness of the diffusion medium layer of the calibration device, and calibrating different verified radon exhalation rate measuring instruments by adjusting the radon exhalation rate of the calibration device;
- an adjustment process for a radon exhalation rate to be adjusted comprises:
- step 1:
- determining thicknesses of the plasterboard and the high-density wood board in the diffusion medium;
- step 2:
- determining a relationship among diffusive solid radon sources with different activities and radon exhalation rates and radon concentrations in the radon accumulation chamber;
- step 3:
- based on the relationship among the diffusive solid radon sources with different activities and the radon exhalation rates and the radon concentrations in the radon accumulation chamber, selecting a diffusive solid radon source according to the radon exhalation rate to be adjusted;
- step 4:
- determining a stable radon concentration in the radon accumulation chamber according to a selected diffusive solid radon source;
- step 5:
- placing the selected diffusive solid radon source in the solid radon source containing chamber, inflating the radon accumulation chamber with a predetermined amount of radon from a gas flow solid radon source, and waiting for the radon concentration in the radon accumulation chamber to reach a balance state;
- when the radon exhalation rate to be adjusted changes, if the thicknesses of the plasterboard and the high-density wood board in the diffusion medium do not change, repeating steps 3-5 to adjust the radon exhalation rate;
- when the radon exhalation rate to be adjusted changes, if the thicknesses of the plasterboard and the high-density wood board in the diffusion medium change, repeating steps 1-5 to adjust the radon exhalation rate.