Research and design of non-radioactive ash meter with multiple γ-ray detectors

To address the limitations of non-radioactive meter with single γ-ray detectors —including inadequate counting rates for low natural radioactivity coal ash measurement, inability to cover the full cross section of wide conveyor belts, and susceptibility to environmental background fluctuations—a non-radioactive meter with multiple γ-ray detector is developed to enhance system performance and applicability. A 2 L NaI (Tl) scintillation detector is selected as the core detection component; each unit can be configured with up to 4 main detectors and 1 environmental background detector. The main detectors are flexibly arranged in transverse linear arrays or longitudinal area arrays, while the environmental detector is used to compensate for background interference. Transverse linear arrays cover 1800～2200 mm bandwidth, and longitudinal area arrays extend the measurement zone. TEC semiconductor temperature control technology ensures detector temperature fluctuations remain below 0.5 °C within 24 hours. Dynamic regulation of high-voltage power supply improves the stability of the non-radioactive meter, stabilizing the 1460 keV characteristic energy peak around channel 256 in the multi-channel spectrum. Comparative single/double-detector tests are conducted on low-radioactivity coal samples from Eastern Inner Mongolia, and measurement resolution, precision, and long-term stability evaluations are performed on clean coal samples from Guangwang Mining Area. Results indicate that compared with single detector systems, dual detector meters achieve effective measurements. For low-radioactivity coal samples, the counting rate of dual detectors is approximately twice that of single detectors, the random error is reduced to 70%. In clean coal measurements, the unit load counting rate is 0.75 cps, with a 5.4 cps increase per 1% ash content rise. Measurement precision reaches 0.19%, and linear correlation (R²) is 0.96. Regarding long-term stability, the range of 24-hour continuous measurements is lower than 0.18%, fully meeting on-site application requirements. By enhancing counting rates, expanding detection coverage, and optimizing environmental compensation, the non-radioactive meter with multiple γ-ray detectors satisfies measurement demands for low-radioactivity coal and high-precision clean coal, demonstrating significant performance advantages and considerable market potential with promising application prospects.