PERFORMANCE OF HANDHELD NAI(TL) SPECTROMETERS AS DOSIMETERS BY LABORATORY AND FIELD DOSE RATE MEASUREMENTS.

Area of Science:

• Nuclear Instrumentation and Radiation Detection
• Environmental Radiation Monitoring
• Dosimetry

Background:

• The International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) J02012 focuses on advancing radiation detection equipment for materials out of regulatory control.
• Commercial NaI(Tl) spectrometers are widely used, but their performance as dosimeters, particularly for ambient gamma dose equivalent rate (ADER), requires thorough evaluation.
• Understanding the capabilities of instruments like the InSpector 1000 and RIIDEYE M-G3 is crucial for effective radiation safety and security applications.

Purpose of the Study:

• To evaluate the performance of two commercial NaI(Tl) spectrometers (InSpector 1000 and RIIDEYE M-G3) as dosimeters for measuring Ambient gamma Dose Equivalent Rate (ADER).
• To assess the accuracy and reliability of these instruments through laboratory calibrations and field measurements under various conditions.
• To investigate the angular dependence and distance-related response of the spectrometers for ADER measurements.

Main Methods:

• Laboratory calibration of NaI(Tl) spectrometers using a 662 keV photon source at varying ADERs (0.17 to 100 μSv h⁻¹) and incidence angles (0° and 90°).
• Assessment of angular dependence (0-359°) and distance response (1-3 m) using a ¹⁵²Eu source.
• Field measurements in the Greek Early Warning System Network and on Northern Greece beaches, comparing spectrometer readings with HPGe detectors, Reuter-Stokes ionization chambers, and sand sample analysis.

Main Results:

• Spectrometer measurements of ADER were compared against reference values from the Ionizing Radiation Calibration Laboratory (IRCL).
• Angular dependence and distance-related response of the detectors were characterized and compared with theoretical predictions.
• Field studies demonstrated the application of these spectrometers in real-world scenarios, including comparison with established monitoring systems and environmental sampling.

Conclusions:

• The evaluated NaI(Tl) spectrometers show potential for ADER measurements, with performance influenced by factors like incidence angle and source distance.
• Laboratory and field data provide valuable insights into the practical application and limitations of these commercial instruments for radiation monitoring.
• The study contributes to the broader goal of enhancing radiation detection capabilities for nuclear security and environmental surveillance.