​The purpose of this work is to assist in the management of emergency situations following accidental exposition to ionizing radiation. The earlier absorbed doses are quantified following exposure, the more efficient the medical team will be able to handle and treat the victims. In most of radiological accidents, irradiation is localized and especially to the hands. Up to now, no techniques exist to estimate these doses with sufficient accuracy. IRSN is implementing a dosimetry technique based on the quantification of radiation induced free radicals using Electron Paramagnetic Resonance (EPR) spectroscopy in fragments human nails. However, the analysis of irradiated nails by EPR spectroscopy remains extremely complicated. A first step was to characterize the nature of radicals at the origin of the endogenous and radio-induced signals and to study their physicochemical properties. We also study the variability of these signals, and we identified a stable UV-induced signal that definitely contributes to the endogenous signal. Two approaches to measure low doses have been proposed: one is based on the behavior of radiation-induced signals with the microwave radiation power; the other is based on the selective regrowth of the radio-induced signal after its total elimination by means of chemical treatment. We have also raised the issue of spectral analyses that is operator-dependent. To avoid manual adjustements, we proposed a uniform EPR data processing approach. Traditional EPR procedures have been vastly improved through simple, repeatable and automatic functional processing of EPR spectra.