Dose assessment after intakes of radionuclides requires application of biokinetic and dosimetric models and assumptions about factors influencing the final result. In 2006, a document giving guidance for such assessment was published, commonly referred to as the IDEAS Guidelines. Following its publication, a working group within the European networks CONRAD and EURADOS was established to improve and update the IDEAS Guidelines. This work resulted in Version 2 of the IDEAS Guidelines, which was published in 2013 in the form of a EURADOS report. The general structure of the original document was maintained; however, new procedures were included, e.g. the direct dose assessment method for (3)H or special procedure for wound cases applying the NCRP wound model. In addition, information was updated and expanded, e.g. data on dietary excretion of U, Th, Ra and Po for urine and faeces or typical and achievable values for detection limits for different bioassay measurement techniques.

Administration of diethylene triamine pentaacetic acid (DTPA) can enhance the urinary excretion rate of plutonium (Pu) for several days, but most of this Pu decorporation occurs on the first day after treatment. The development of a biokinetic model describing the mechanisms of decorporation of actinides by administration of DTPA was initiated as a task of the coordinated network for radiation dosimetry project. The modelling process was started by using the systemic biokinetic model for Pu from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiation Protection Publication 53. The chelation of Pu and DTPA to Pu-DTPA was treated explicitly and is assumed to follow a second-order process. It was assumed that the chelation takes place in the blood and in the rapid turnover soft tissues compartments of the Pu model, and that Pu-DTPA behaves in the same way as administered DTPA. First applications of this draft model showed that the height of the peak of urinary excretion after administration of DTPA was determined by the chelation rate. However, repetitions of DTPA administration shortly after the first one showed no effect in the application of the draft model in contrast to data from real cases. The present draft model is thus not yet realistic. Therefore several questions still have to be answered, notably about where the Pu-DTPA complexes are formed, which biological ligands of Pu are dissociated, if Pu-DTPA is stable and if the biokinetics of Pu-DTPA excretion is similar to that of DTPA. Further detailed studies of human contamination cases and experimental data about Pu-DTPA kinetics will be needed in order to address these issues. The work will now be continued within a working group of EURADOS.

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The TECHREC project, funded by the European Commission, will provide Technical Recommendations for Monitoring Individuals for Occupational Intakes of Radionuclides It is expected that the document will be published by the European Commission as a report in its Radiation Protection Series during 2016. The project is coordinated by the European Radiation Dosimetry Group (EURADOS) and is being carried out by members of EURADOS Working Group 7 (Internal Dosimetry). This paper describes the aims and purpose of the Technical Recommendations, and explains how the project is organised.

This work presents an overview of the applications of retrospective dosimetry techniques in case of incorporation of radionuclides. The fact that internal exposures are characterized by a spatially inhomogeneous irradiation of the body, which is potentially prolonged over large periods and variable over time, is particularly problematic for biological and electron paramagnetic resonance (EPR) dosimetry methods when compared with external exposures. The paper gives initially specific information about internal dosimetry methods, the most common cytogenetic techniques used in biological dosimetry and EPR dosimetry applied to tooth enamel. Based on real-case scenarios, dose estimates obtained from bioassay data as well as with biological and/or EPR dosimetry are compared and critically discussed. In most of the scenarios presented, concomitant external exposures were responsible for the greater portion of the received dose. As no assay is available which can discriminate between radiation of different types and different LETs on the basis of the type of damage induced, it is not possible to infer from these studies specific conclusions valid for incorporated radionuclides alone. The biological dosimetry assays and EPR techniques proved to be most applicable in cases when the radionuclides are almost homogeneously distributed in the body. No compelling evidence was obtained in other cases of extremely inhomogeneous distribution. Retrospective dosimetry needs to be optimized and further developed in order to be able to deal with real exposure cases, where a mixture of both external and internal exposures will be encountered most of the times.