Fig. 1. Architecture schematic of online monitoring system for γ radioactivity in a body of water

Fig. 2. Schematic diagram (a) and photograph (b) of the detector unit

Fig. 3. Schematic diagram of the networking mode and order flow of the 4G-RTU communication unit

Fig. 4. Schematic diagram (a) and photograph (b) of the floating body unit

Fig. 5. System software design framework

Fig. 6. Flowchart of software implementation method (a) and actual operating interface (b)

Fig. 7. Two measured spectra of the ¹³⁷Cs energy resolution

Fig. 8. Two measured spectra of the energy spectrum peak drift test

Fig. 9. Liner fitting line and equation of the energy linearity test

Fig. 10. YM2 model test photograph (a) and measured spectrum (b)

Fig. 11. System working temperature test photograph (a) and measured window data curves (b)

Fig. 12. Photograph of ¹³⁷Cs volume source and lead chamber (a) and spectrum with removed background (b)

Fig. 13. Actual on-site photograph of the measured field in the Taiping river of Shijiazhuang city

Fig. 14. TC, K, U, and Th window count rate curves for every 300 s of sampling time