Optically stimulated luminescence (OSL) for retrospective and prospective dosimetry after a radiological emergency

A radiological or nuclear (R/N) accident involves several stages that requires different methods and approaches to mitigate the consequences in terms of health detriments of exposed individuals e.g. workers and members of the public. The accident management stages can be divided into three phases: i) the initial phase after the start of the radiation exposure that may include triage and emergency treatment of exposed individuals which will heavily rely on retrospective dose assessments; ii) the recovery and clean-up phase, which, depending on the severity of the accident, may require extensive individual prospective dose assessments, and iii) the long-term phase when measures are done to restore life conditions to pre-accident conditions in affected areas, during which a system for individual dosimetry in combination with stationary and mobile assessments will be required to ascertain the involved stakeholders.

During these three phases, there are different demands on the decision makers, as well as expectations on their response time. Of importance during all three stages is knowledge on the radiation exposure of unintentionally exposed individuals and to enable them to make informative based decisions. Workers with ionizing radiation are expected to wear dosemeters, but the majority of the exposed individuals after a severe R/N accident or antagonistic act is the un-monitored public. For those that are not monitored during the initial phase it is possible to reconstruct the individual doses, either by biological- or physical measurements or by mathematical calculations (based on in situ radiation measurements). Of these retrospective methods the most rapid and sensitive one is based on physical measurements of personal belongings or common place materials using optically stimulated luminescence (OSL) or electron paramagnetic resonance (EPR) assessments. There are a number of previously identified materials that are sensitive to ionizing radiation when read by OSL, and in particular common household salt (NaCl). At the Medical Radiation Physics group in Malmö, Lund University, we have studied the applicability of NaCl for retrospective dosimetry and recently also for prospective dosimetry using the improved dosimetric properties achievable when compressing the NaCl to pellets.

In this Ph.D. project we will further improve the use of NaCl and other materials in OSL dosimetry during the different phases after a radiological emergency, i.e. by means of retrospective- and prospective approaches. Special focus will be to explore the potential of NaCl pellets and other common household and workplace materials as personal/individual monitors in areas that are restored or resettled after evacuation. There may be a niche for dose-accumulating sensors that can be manufactured within hours, that do not require external power and batteries, and can be easily worn as a ring or necklace. Other relevant and OSL sensitive materials will be identified, known and fortuitous, and studied in parallel for improving the potential with OSL dosimetry during the various phases, especially the initial one that require retrospective dosimetry methods (accident dosimetry). The work during the Ph.D. programme and its outcome will improve and maintain the national competence in the area and be of high relevance to the international community. The system for OSL dosimetry in emergency preparedness, that would be the overarching outcome of the project, will be a solid basis and of importance when communicating risks etc. with unintentionally exposed individuals of the public and other stakeholders.