At present, most of the contamination detection equipments for small items in domestic nuclear power plants are manually putting in and taking out the testing items, and the operation time is long and the steps are relatively tedious. According to the on-site demand of nuclear power and feedback on the use of similar imported equipment, contamination detection equipment based on the conveyor belt can effectively solve these drawbacks.

This study aims to design a small item γ pollution measuring instrument that can be used to transmit items with a conveyor belt, hence effectively improve the detection efficiency and save the cost of manual operation.

Semi-automatic two-channel control design scheme was adopted, one through the motor driver to control the conveyor belt motor running mode, the other control the digital circuit of the radiation detector and the corresponding electrical parts through the main control board. Linkage of contamination monitoring status and item convey was achieved by the status control board associated with the motor drive. The background counting rate of the equipment in the background environment, the counting rate of the radioactive source at rest in the center of the measuring chamber and the dynamic counting rate of the radioactive source moving through the measuring chamber with the conveyor belt were tested and analyzed.

The results show that the minimum net count value of the detector is 81.6% of the average count in the static state. The net value of the minimum peak value of the detector at motion state is 89.3% of the average peak count, and the minimum detectable limit is 111 Bq.

The test performance of prototype is better than the reference standard and meets the design requirements.