Optimization of alarm settings for public exposure monitoring and control with low-resolution gamma spectrometry in the scenario of mobile facilities

The proliferation of mobile radiation-emitting systems—ranging from portable power generators to medical and industrial platforms—requires reliable real-time radiation monitoring to ensure public safety and regulatory compliance. This study aims to optimize alarm settings in low-resolution gamma spectrometry for mobile facilities by reducing false alarms while maintaining sensitivity to anomalous exposures. A dual-parameter monitoring framework was developed based on temporal variations of average gamma photon energy and ambient dose equivalent rate Ḣ*(10). Pulse Height Spectra (PHS) from a 2.5″×2.5″ NaI(Tl) detector were analyzed using G-function transformations to directly estimate radiological quantities without spectrum unfolding. Field validation was conducted through car-borne gamma spectrometry under variable conditions (dry, rainy) and simulated source maneuver scenarios. The combined use of dose rate and average photon energy significantly improved anomaly detection compared to single-parameter approaches. The method successfully identified low-strength 137Cs sources, gradual dose increases, and spectral deviations of ±2.5% relative to baseline, while reducing false alarms to below 2% in mobile and stationary monitoring. Simulations confirmed the robustness of alarm thresholds across scenarios of planned and existing exposures. The proposed dual-parameter method enhances alarm precision and situational awareness in dynamic environments, offering a practical, computationally efficient alternative for real-time radiation monitoring. Its integration into mobile systems strengthens compliance with radiation protection principles, particularly the public dose constraint of 0.3 mSv/year, and supports adaptive responses in complex exposure situations.