A framework for exposure characterization and gamma dosimetry at the NMBU FIGARO irradiation facility

<p><b>Purpose</b>: The FIGARO low dose <sup>60</sup>Co gamma irradiation facility at the Norwegian University of Life Sciences, Ås, Norway, is dedicated to the study of effects on living organisms from acute or chronic ionizing radiation exposures, either alone or in combination with other stressors such as UV radiation, metals or radionuclides. Here, we present a framework of working guidelines and computer software for characterization of absorbed dose rates and accumulated doses to organisms exposed within the continuous gamma field at FIGARO. The aims of the framework are to ensure gamma exposures are well characterized, that results from exposures are correctly interpreted in terms of absorbed dose rates and accumulated doses, and that sufficient information is available so that exposures can be reproduced later or at other facilities.</p> <p><b>Methods</b>: The software of the framework includes a Geant4 application for Monte Carlo radiation transport simulations and tools for dose planning, recording and reporting. The working guidelines are prepared for expert users who provide simulated, calculated or estimated absorbed dose rates and for regular users who conduct exposure experiments and are responsible for record keeping. To demonstrate the developed framework, we use a case study where 14 freshwater microcosms are exposed to four levels of gamma dose rates at FIGARO.</p> <p><b>Conclusion</b>: The framework guides users towards good dosimetry practices. Lessons learned could be transferable to other gamma irradiation facilities.</p>