Dose estimation using unconventional dosimeters during radiological/nuclear emergencies remains challenging and essential for medical triage. In this work, we have explored the potential of utilizing eggshells as an unconventional dosimeter using electron spin resonance (ESR) spectroscopy. Eggshell particle size was optimized (210 to 250 µm) to remove the angular dependence of ESR signal using a Goniometer setup. The radiation induced radicals in irradiated eggshells were identified as orthorhombic \({\text{CO}}_{2}^{-}\) , axial \({\text{CO}}_{2}^{-}\) , and axial \({\text{CO}}_{3}^{3-}\) radicals. Among them, \({\text{g}}_{\perp }=2.0020\) component of axial \({\text{CO}}_{2}^{-}\) radical and \({\text{g}}_{\parallel }=2.0011\) component of axial \({\text{CO}}_{3}^{3-}\) radical were used for dosimetry studies. Dose response was found to be linear up to 1 kGy with a minimum detectable dose of ~ 1 Gy. From fading studies, the signal was found to decay up to 55% within eight days due to ~ 93% fading of axial \({\text{CO}}_{3}^{3-}\) radicals. Single aliquot additive dose (SAAD) technique was used for dose reconstruction from irradiated eggshells, and the technique was validated with other standard dosimeters like alanine/ESR and TL (thermoluminescence) discs. The results of the detailed dosimetric investigations showed that eggshells can be potentially used for retrospective dose assessment in case of radiation emergencies by applying proper fading correction.
