Development and Optimization of a Photodiode-Based Wide-Range Gamma Dose Rate Monitor for Nuclear Applications

Accurate gamma dose rate measurement is essential for radiation protection, environmental monitoring, and process control in nuclear facilities operating under high-radiation conditions. One of the key requirements of a measurement system is operational flexibility, portability, and the capability to perform measurements over a wide range. In response to these requirements, this study presents the development and optimization of a compact photodiode-based gamma dose rate monitoring system with a wide dynamic range for high dose-rate applications. The work primarily focused on improving the detector energy response through the design and optimization of an energy-compensation filter using Monte Carlo simulations performed with the FLUKA radiation transport code. The uncompensated detector exhibited significant over-response at lower photon energies due to the energy dependence of photon interactions within the detector material. To mitigate this effect, a graded compensation filter comprising copper and stainless-steel layers was designed and optimized. Experimental characterization was carried out using ISO 4037 narrow-spectrum X-ray beam qualities of 80–250 kV, along with 137Cs and 60Co gamma-ray sources. The optimized detector configuration demonstrated a nearly energy-independent response over the photon-energy range from 100 keV to 1.3 MeV. Experimental measurements showed good agreement with simulation predictions, validating the proposed compensation methodology. Dose rate linearity measurements performed up to 10 000 R/h using a 60Co source demonstrated linear detector response with deviations within ±15% of reference values. The developed system offers a compact, lightweight, and low-power alternative to conventional ionization chamber-based monitors for wide-range gamma dose-rate measurements in nuclear fuel cycle facilities.