New dosimetry methods for radiological and nuclear emergency management: mapping radiation fields using NaCl and portable OSL readers

In the aftermath of a nuclear or radiological incident, rapid and reliable dose assessment is critical for medical triage, exposure evaluation, and emergency management. This study investigates the use of household salt with portable Optically Stimulated Luminescence (OSL) systems as a potential dosimetry system to enhance methods for mapping radiation fields with data available during the measurement period. Previous studies have shown that unprepared commercial salt demonstrated a linear dose response in the 0–500 µGy range, with detection limits as low as 7 µGy using portable OSL. Signal stability studies revealed an initial brief decrease in luminescence post-irradiation, followed by relative stability between 8–64 days, enabling dose estimation during early and late emergency phases. Light and moisture caused rapid signal loss, which was mitigated by encapsulating sachets of salt in sealed heat-shrink sleeving. In this work, three experiments were conducted to confirm salt’s utility. Controlled lab tests mapped the radiation field in close proximity to a known activity 60-Co source. A dosimetry array was used outdoors at SUERC, in combination with portable gamma ray spectrometry, to map background radiation with and without a source present. Thirdly a network of dosimeters was used to map the complex and time varying radiation fields within an accelerator mass spectrometry laboratory at SUERC. In the controlled lab experiment, fading-corrected doses matched theoretical inverse-square values within <3% on average. In the outdoor experiments average dose rates agreed with backpack gamma measurements within 3–15%. In the accelerator laboratory the salt effectively separated the spatial variations in the local radiation background of the laboratory from those associated with enhanced radiation during beam alignment and tuning operations. Results thus aligned with theoretical doses, gamma-system measurements, and the configuration of radiation fields within a complex laboratory confirming salt’s potential for low-dose dosimetry and spatial field mapping. Protocols for fading correction, ambient conditions, and zeroing are essential for practical deployment. The work presented here has demonstrated that the field validation of using salt with portable OSL systems is capable of delivering dose estimates in the range from a few µGy to several mGy in field measurements, complementing existing techniques. To optimize this approach, comprehensive protocols should be developed for both testing exercises and evaluations, which could lead to wider acceptance of these approaches offering a robust, low-cost solution for rapid dose assessment for both emergency response and environmental dosimetry.