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For monitoring radioactive contamination of water systems due to nuclear accidents or terrorist attacks, there is need of an in situ online measurement to assess alpha-, beta- and gamma-emitting radionuclide contaminants quickly and accurately. However, there is no well-established online monitoring system for permanent surveillance of drinking water systems. Therefore, a real-time measurement system was developed based on the readout of plastic scintillator sheets by a photomultiplier. Direct contact between scintillator and streaming water allows for the detection of both long- and short-ranged particles. Using a passive cooling system, detection limits of 141 Bq/L for $$^{241}$$ 241 Am, 20 Bq/L for $$^{60}$$ 60 Co and 17 Bq/L for $$^{137}$$ 137 Cs were achieved with measurements of 60 s counting time. The system has been designed to be operated safely without deep knowledge of radiation measurement technology. The detector can be connected as a bypass to a water system and be operated in a continuous online survey mode, making it applicable as an early warning system.

Since 2012, the European Radiation Dosimetry Group (EURADOS) has developed its Strategic Research Agenda (SRA), which contributes to the identification of future research needs in radiation dosimetry in Europe. Continued scientific developments in this field necessitate regular updates and, consequently, this paper summarises the latest revision of the SRA, with input regarding the state of the art and vision for the future contributed by EURADOS Working Groups and through a stakeholder workshop. Five visions define key issues in dosimetry research that are considered important over at least the next decade. They include scientific objectives and developments in (i) updated fundamental dose concepts and quantities, (ii) improved radiation risk estimates deduced from epidemiological cohorts, (iii) efficient dose assessment for radiological emergencies, (iv) integrated personalised dosimetry in medical applications and (v) improved radiation protection of workers and the public. This SRA will be used as a guideline for future activities of EURADOS Working Groups but can also be used as guidance for research in radiation dosimetry by the wider community. It will also be used as input for a general European research roadmap for radiation protection, following similar previous contributions to the European Joint Programme for the Integration of Radiation Protection Research, under the Horizon 2020 programme (CONCERT). The full version of the SRA is available as a EURADOS report (www.eurados.org).

The European Radiation Dosimetry Group (EURADOS) is a network of organizations and scientists promoting research and development in the dosimetry of ionizing radiation, contributing to harmonization in dosimetry practice across Europe, and offering education and training in areas relevant for dosimetry. As a registered non-profit association under German law, EURADOS is currently running eight active working groups (WGs): WG2 on “Harmonization of Individual Monitoring”, WG3 on “Environmental Dosimetry”, WG6 on “Computational Dosimetry”, WG7 on “Internal Dosimetry”, WG9 on “Dosimetry in Radiotherapy”, WG10 on “Retrospective Dosimetry”, WG11 on “Dosimetry in High-Energy Radiation Fields”, and WG12 on “Dosimetry in Medical Imaging”. This paper presents recent scientific results obtained within these working groups, and additionally highlights the role of EURADOS as an organization which contributes to the development of a systematic strategy of radiation protection research in Europe.

In contrast to external dosimetry, which can be based on measurement of operational quantities directly related to the effective dose (mSv), the assessment of doses due to intakes of radionuclides relies on the measurement of activities (Bq) and subsequent modelling. The methodology and the models are published by the International Commission on Radiological Protection (ICRP) and are later implemented in national regulations. This paper describes the general concepts for assessment of internal occupational exposure and diagnostic nuclear medicine applications using biokinetic and dosimetric models. The current changes in the models which are presented in the OIR series (Occupational Intakes of Radionucldes) of ICRP are outlined and information on the uncertainties in internal dose assessment are presented.

Decorporation therapy with salts of diethylenetriamine-pentaacetic acid binds actinides, thereby limiting uptake to organs and enhancing the rate at which actinides are excreted in urine. International Commission on Radiological Protection reference biokinetic models cannot be used to fit this enhanced exertion simultaneously with the baseline actinide excretion rate that is observed prior to the start of therapy and/or after the effects of therapy have ceased. In this study, the Coordinated Network on Radiation Dosimetry approach, which was initially developed for modeling decorporation of plutonium, was applied to model decorporation of americium using data from a former radiation worker who agreed to donate his body to the US Transuranium and Uranium Registries for research. This individual was exposed to airborne Am, resulting in a total-body activity of 66.6 kBq. He was treated with calcium-diethylenetriamine-pentaacetic acid for 7 y. The time and duration of intakes are unknown as no incident reports are available. Modeling of different assumptions showed that an acute intake of 5-μm activity median aerodynamic diameter type M aerosols provides the most reasonable description of the available pretherapeutic data; however, the observed Am activity in the lungs at the time of death was higher than the one predicted for type M material. The Coordinated Network on Radiation Dosimetry approach for decorporation modeling was used to model the in vivo chelation process directly. It was found that the Coordinated Network on Radiation Dosimetry approach, which only considered chelation in blood and extracellular fluids, underestimated the urinary excretion of Am during diethylenetriamine-pentaacetic acid treatment; therefore, the approach was extended to include chelation in the liver. Both urinary excretion and whole-body retention could be described when it was assumed that 25% of chelation occurred in the liver, 75% occurred in the blood and ST0 compartment, and the chelation rate constant was 1 × 10 pmol d. It was observed that enhancement of urinary excretion of Am after injection of diethylenetriamine-pentaacetic acid exponentially decreased to the baseline level with an average half-time of 2.2 ± 0.7 d.

International audience; European Radiation Dosimetry Group (EURADOS) Working Group 7 is a network on internal dosimetry that brings together researchers from more than 60 institutions in 21 countries. The work of the group is organised into task groups that focus on different aspects, such as development and implementation of biokinetic models (e.g. for diethylenetriamine penta-acetic acid decorporation therapy), individual monitoring and the dose assessment process, Monte Carlo simulations for internal dosimetry, uncertainties in internal dosimetry, and internal microdosimetry. Several intercomparison exercises and training courses have been organised. The IDEAS guidelines, which describe – based on the International Commission on Radiological Protection’s (ICRP) biokinetic models and dose coefficients – a structured approach to the assessment of internal doses from monitoring data, are maintained and updated by the group. In addition, Technical Recommendations for Monitoring Individuals for Occupational Intakes of Radionuclides have been elaborated on behalf of the European Commission, DG-ENER (TECHREC Project, 2014–2016, coordinated by EURADOS). Quality assurance of the ICRP biokinetic models by calculation of retention and excretion functions for different scenarios has been performed and feedback was provided to ICRP. An uncertainty study of the recent caesium biokinetic model quantified the overall uncertainties, and identified the sensitive parameters of the model. A report with guidance on the application of ICRP biokinetic models and dose coefficients is being drafted at present. These and other examples of the group’s activities, which complement the work of ICRP, are presented. © 2018, The International Society for Prosthetics and Orthotics.

International audience; European Radiation Dosimetry Group e. V. (EURADOS) survey on individual monitoring data and dose assessment has been carried out for 550 foreigners returning home after being exposed in Japan to intakes of radionuclides (mainly 131I, 132I, 132Te, 134Cs and 137Cs) as a consequence of the Fukushima Daiichi NPP accident. In vivo and in vitro measurements were performed in their respective countries at an early stage after that accident. Intakes of radionuclides were detected in 208 persons from Europe and Canada, but the committed effective dose E(50) was below the annual dose limit for the public (andlt;1 mSv) in all the cases. Lessons learned from this EURADOS survey are presented here regarding not only internal dosimetry issues, but also the management of the emergency situation, the perception of the risk of health effects due to radiation and the communication with exposed persons who showed anxiety and lack of trust in monitoring data and dose assessments. © The Author 2015. Published by Oxford University Press. All rights reserved.

In 1983, a young man inhaled accidentally a large amount of plutonium and americium. This case was carefully followed until 2013. Since no decorporation measures had been taken, the undisturbed metabolism of Pu and Am can be derived from the data. First objective was to determine the amount of inhaled radionuclides and to estimate committed effective dose. In vivo and excretion measurements started immediately after the inhalation, and for quality assurance, all types of measurements were performed by different labs in Europe and the USA. After dose assessment by various international groups were completed, the measurements were continued to produce scientific data for model validation. The data have been analysed here to estimate lung absorption parameter values for the inhaled plutonium and americium oxide using the proposed new ICRP Human Respiratory Tract Model. As supplement to the biokinetic modelling, biological data from three different cytogenetic markers have been added. The estimated committed effective dose is in the order of 1 Sv. The subject is 30 y after the inhalation, of good health, according to a recent medical check-up.

A goal of whole body counting (WBC) is the estimation of the total body burden of radionuclides disregarding the actual position within the body. To achieve the goal, the detectors need to be placed in regions where the photon flux is as independent as possible from the distribution of the source. At the same time, the detectors need high photon fluxes in order to achieve better efficiency and lower minimum detectable activities. This work presents a method able to define the layout of new WBC systems and to study the behaviour of existing ones using both detection efficiency and its dependence on the position of the source within the body of computational phantoms.

One important parameter for biokinetic plutonium modelling is the ratio between the contents of plutonium in liver and skeleton. Autopsy data show a vast inter-individual variation in the partitioning between these organs. The capacity of recent biokinetic models for plutonium to reproduce these variations was studied. Autopsy data for plutonium amounts in liver and skeleton for both (238)Pu and (239)Pu isotopes can be merged into a single data set following several statistical tests. Simulations with different parameter values generate a mapping between the autopsy values and the model parameters. The observed partitioning distribution can be transformed into a distribution of transfer rates, which would result in the observed data. Besides, the variation in the partitioning between liver and skeleton leads via biliary pathway to a variation in the excretion ratio. This can be used to estimate an individual partitioning factor, which can be used in individual case assessments.

The basic idea of Voxel2MCNP is to provide a framework supporting users in modeling radiation transport scenarios using voxel phantoms and other geometric models, generating corresponding input for the Monte Carlo code MCNPX, and evaluating simulation output. Applications at Karlsruhe Institute of Technology are primarily whole and partial body counter calibration and calculation of dose conversion coefficients. A new generic data model describing data related to radiation transport, including phantom and detector geometries and their properties, sources, tallies and materials, has been developed. It is modular and generally independent of the targeted Monte Carlo code. The data model has been implemented as an XML-based file format to facilitate data exchange, and integrated with Voxel2MCNP to provide a common interface for modeling, visualization, and evaluation of data. Also, extensions to allow compatibility with several file formats, such as ENSDF for nuclear structure properties and radioactive decay data, SimpleGeo for solid geometry modeling, ImageJ for voxel lattices, and MCNPX's MCTAL for simulation results have been added. The framework is presented and discussed in this paper and example workflows for body counter calibration and calculation of dose conversion coefficients is given to illustrate its application.

International audience; 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. © Crown copyright 2015.

International audience; Monte Carlo (MC) methods are numerical simulation techniques that can be used to extend the scope of calibrations performed in in vivo monitoring laboratories. These methods allow calibrations to be carried out for a much wider range of body shapes and sizes than would be feasible using physical phantoms. Unfortunately, nowadays, this powerful technique is still used mainly in research institutions only. In 2013, EURADOS and the in vivo monitoring laboratory of Karlsruhe Institute of Technology (KIT) organized a 3-d training course to disseminate knowledge on the application of MC methods for in vivo monitoring. It was intended as a hands-on course centered around an exercise which guided the participants step by step through the calibration process using a simplified version of KIT's equipment. Only introductory lectures on in vivo monitoring and voxel models were given. The course was based on MC codes of the MCNP family, widespread in the community. The strong involvement of the participants and the working atmosphere in the classroom as well as the formal evaluation of the course showed that the approach chosen was appropriate. Participants liked the hands-on approach and the extensive course materials on the exercise. © The Author 2016. Published by Oxford University Press. All rights reserved.

International audience; In 2011 a measurement intercomparison was launched by EURADOS WG7, with the objective of providing the participants with the tools to calibrate their detection systems for detection of 241Am in the skull bone, and evaluate the variability due to the used of the different calibration phantoms. Three skull phantoms were used in this intercomparison the USTUR Case 0102 skull phantom, the BfS skull phantom and the CSR skull phantom. Very good agreement was found between the results of the twelve participating laboratories, with relative deviations of less than 15% for the BfS phantom and less than 17% for the USTUR phantom when measurement efficiency in defined positions was compared. However, the phantoms' measured absolute 241Am activities showed discrepancies of up to a factor of 3.4. This is mainly due to the physical differences between the standard calibration phantoms used by the participants and those used in this intercomparison exercise. © 2015 Elsevier Ltd. All rights reserved.

The in vivo monitoring Lab at KIT uses two phoswich detectors for routine lung counting. A simplified model of one of them has been implemented in the two Monte Carlo codes EGSnrc and MCNPX. The active part of the detector consists of a crystal of NaI(Tl) and one of CsI(Tl): the energy deposited in both the crystals have been studied to consider the effect of the anticoincidence logic, present in the read-out electronics of the detectors and not yet studied with Monte Carlo simulations. Only the NaI(Tl) crystal has then been used to study the escape peaks at several energies, which are more prominent at low energies. The results from the two codes have been compared. The comparison of the codes predictions for the escape peaks has been then extended using the model of a germanium detector.

EURADOS working group on 'Internal Dosimetry (WG7)' represents a frame to develop activities in the field of internal exposures as coordinated actions on quality assurance (QA), research and training. The main tasks to carry out are the update of the IDEAS Guidelines as a reference document for the internal dosimetry community, the implementation and QA of new ICRP biokinetic models, the assessment of uncertainties related to internal dosimetry models and their application, the development of physiology-based models for biokinetics of radionuclides, stable isotope studies, biokinetic modelling of diethylene triamine pentaacetic acid decorporation therapy and Monte-Carlo applications to in vivo assessment of intakes. The working group is entirely supported by EURADOS; links are established with institutions such as IAEA, US Transuranium and Uranium Registries (USA) and CEA (France) for joint collaboration actions. © The Author 2010. Published by Oxford University Press. All rights reserved.

The position of detectors used for partial-body counters relative to a measured person has considerable influence on the counting efficiency of low-energy photon emitters. To minimise reading errors and enhance reproducibility of position data, an electronic position recording system was installed in the partial-body counter chamber at KIT. Phoswich detectors have been equipped with electronic sensors to determine the position and axes of the detectors. Additionally, a laser measurement system determines the position of arbitrary landmarks, e.g. point sources, anatomical features of phantoms and test persons. A network interface enables the reading of the position data on any connected computer. The system was successfully used to validate Monte Carlo simulations of partial-body counting scenarios for the numerical determination of counting efficiencies.

Modelling Pu/Am decorporation by DTPA. A new tool has been developed to optimize DTPA efficacy as concerns reduction of effective dose after 239 Pu wound. For example, the simulations show, for moderately soluble compounds (type M), a 1/3 decrease of effective dose is obtained after repeated early treatment (24 i.v. for 4 months), whereas a decrease by a factor 5 can be reached if treatments continue for 5 years at 2 week interval. By contrast, for poorly soluble compounds (type S), negligible efficacy is observed after early treatments, and a 3 time decrease of dose is obtained for treatments performed at 2 week interval for 50 years. Some of the hypotheses retained for modelling DTPA decorporation are validated from new experimental data published recently, and structure of a new model which can be applied both to Pu and Am is reported, taking into account urinary and faecal excretion, structure being suitable for different doses of DTPA and using various galenic forms.

The CONRAD Project is a Coordinated Network for Radiation Dosimetry funded by the European Commission 6th Framework Programme. The activities developed within CONRAD Work Package 5 ('Coordination of Research on Internal Dosimetry') have contributed to improve the harmonisation and reliability in the assessment of internal doses. The tasks carried out included a study of uncertainties and the refinement of the IDEAS Guidelines associated with the evaluation of doses after intakes of radionuclides. The implementation and quality assurance of new biokinetic models for dose assessment and the first attempt to develop a generic dosimetric model for DTPA therapy are important WP5 achievements. Applications of voxel phantoms and Monte Carlo simulations for the assessment of intakes from in vivo measurements were also considered. A Nuclear Emergency Monitoring Network (EUREMON) has been established for the interpretation of monitoring data after accidental or deliberate releases of radionuclides. Finally, WP5 group has worked on the update of the existing IDEAS bibliographic, internal contamination and case evaluation databases. A summary of CONRAD WP5 objectives and results is presented here.

Current calibration methods for body counting offer personalisation for lung counting predominantly with respect to ratios of body mass and height. Chest wall thickness is used as an intermediate parameter. This work revises and extends these methods using a series of computational phantoms derived from medical imaging data in combination with radiation transport simulation and statistical analysis. As an example, the method is applied to the calibration of the In Vivo Measurement Laboratory (IVM) at Karlsruhe Institute of Technology (KIT) comprising four high-purity germanium detectors in two partial body measurement set-ups. The Monte Carlo N-Particle (MCNP) transport code and the Extended Cardiac-Torso (XCAT) phantom series have been used. Analysis of the computed sample data consisting of 18 anthropometric parameters and calibration factors generated from 26 photon sources for each of the 30 phantoms reveals the significance of those parameters required for producing an accurate estimate of the calibration function. Body circumferences related to the source location perform best in the example, while parameters related to body mass show comparable but lower performances, and those related to body height and other lengths exhibit low performances. In conclusion, it is possible to give more accurate estimates of calibration factors using this proposed approach including estimates of uncertainties related to interindividual anatomical variation of the target population.

The partial-body counter currently installed at KIT is under redesign to add whole-body counting capabilities and replace the current phoswich detectors with HPGe ones, capable of detecting low energy photons ( 210 Pb, 241 Am). Different configurations for the positioning of the subject have been tested with the aid of Monte Carlo simulations and the performances attainable with a sitting and a lying configuration were compared. The optimal placement of the detectors was also defined. The simulations were used to estimate the counting efficiencies and also to estimate the Compton scattering produced by 40 K, in turn used to calculate the minimum detectable activities.

Purpose: To develop a physiologically based compartmental approach for modeling plutonium decorporation therapy with the chelating agent Diethylenetriaminepentaacetic acid (Ca-DTPA/Zn-DTPA). Materials and methods: Model calculations were performed using the software package SAAM II (©The Epsilon Group, Charlottesville, Virginia, USA). The Luciani/Polig compartmental model with age-dependent description of the bone recycling processes was used for the biokinetics of plutonium. Results: The Luciani/Polig model was slightly modified in order to account for the speciation of plutonium in blood and for the different affinities for DTPA of the present chemical species. The introduction of two separate blood compartments, describing low-molecular-weight complexes of plutonium (Pu-LW) and transferrin-bound plutonium (Pu-Tf) respectively, and one additional compartment describing plutonium in the interstitial fluids was performed successfully. Conclusions: The next step of the work is the modeling of the chelation process, coupling the physiologically modified structure with the biokinetic model for DTPA. Results of animal studies performed under controlled conditions will enable to better understand the principles of the involved mechanisms.

International audience; Parameter uncertainties for the biokinetic model of caesium (Cs) developed by Leggett et al. were inventoried and evaluated. The methods of parameter uncertainty analysis were used to assess the uncertainties of model predictions with the assumptions of model parameter uncertainties and distributions. Furthermore, the importance of individual model parameters was assessed by means of sensitivity analysis. The calculated uncertainties of model predictions were compared with human data of Cs measured in blood and in the whole body. It was found that propagating the derived uncertainties in model parameter values reproduced the range of bioassay data observed in human subjects at different times after intake. The maximum ranges, expressed as uncertainty factors (UFs) (defined as a square root of ratio between 97.5th and 2.5th percentiles) of blood clearance, whole-body retention and urinary excretion of Cs predicted at earlier time after intake were, respectively 1.5, 1.0 and 2.5 at the first day; 1.8, 1.1 and 2.4 at Day 10 and 1.8, 2.0 and 1.8 at Day 100; for the late times (1000 d) after intake, the UFs were increased to 43, 24 and 31, respectively. The model parameters of transfer rates between kidneys and blood, muscle and blood and the rate of transfer from kidneys to urinary bladder content are most influential to the blood clearance and to the whole-body retention of Cs. For the urinary excretion, the parameters of transfer rates from urinary bladder content to urine and from kidneys to urinary bladder content impact mostly. The implication and effect on the estimated equivalent and effective doses of the larger uncertainty of 43 in whole-body retention in the later time, say, after Day 500 will be explored in a successive work in the framework of EURADOS. © The Author 2014.

A virtual model of a Canberra HPGe detector was produced with the aid of MCNPX and of different point sources. The measured and expected count rates were compared. The initial results showed significant discrepancies, therefore additional parametric simulations have been used to improve the model. As a result, the agreement between theoretical and measured performances in the middle-upper part of the spectrum improved, while low energy photons still score the worst, due to incomplete knowledge of the inner structure of the housing that would require additional extensive measurements.

International audience; In vivo measurements are commonly used to determine the incorporated activity of radionuclides. However, for complex or old contaminations, the assessment of the activity distribution among organs is difficult to obtain from measurements only. A method is suggested to assess the activity of organs; it consists in separating the contribution of each contaminated organ in the experimental counts using organ-specific counting efficiencies. The feasibility of the method was first experimentally investigated using two torso phantoms containing radioactive organs. The first phantom contained two radioactive lungs and the second one two lungs and a liver. In the two cases the activity distribution was obtained using experimental specific efficiencies and the bias when compared with true activity was below 5%. The experiments were reproduced by Monte Carlo calculations in order to test the efficiency of the separation method with calculated organ-specific counting efficiencies instead of experimental ones. For the first experiment, the most contributing organ-specific counting efficiencies were correctly simulated but biases as large as 70% were found for the less contributing ones. Consequently, for one organ the activity was correctly assessed but for the other a 20% underestimate was found. For the second experiment, the calculated efficiencies were in better agreement with experimental values and the maximal difference between the calculated and the reference activity was 11%. The method's limits were investigated using perturbation point sources and considering wrong activity distribution hypothesis. The method gives correct results when the number of contaminated organs is overestimated by the startup hypothesis. The opposite situation can be identified only if more measurements than required by the startup hypothesis are carried out. © 2013 Elsevier Ltd. All rights reserved.

To fully characterize the front dead layer (DL) of an HPGe detector at low photon energy range, its intrinsic efficiency curve was measured using a 241 Am radioactive source in 10−60 keV energy range. A comparison between experimental efficiency and MCNPX results showed that the DL value of 0.4 μm initially quoted by the manufacturer has to be changed to 7.5 μm to reproduce measurements.

This paper describes new biokinetic and dosimetric models, especially those being developed by ICRP which will be used in the forthcoming documents on Occupational Intakes of Radionuclides. It also presents the results of a working group within the European project CONRAD which is being continued within EURADOS. This group is implementing the new models, performing quality assurance of the model implementation (including their description) and giving guidance to the scientific community on the application of the models for individual dose assessment. © The Author 2010. Published by Oxford University Press. All rights reserved.

The in vivo monitoring laboratory (IVM) at Karlsruhe Institute of Technology (KIT), with one whole body counter and three partial-body counters, is an approved lab for individual monitoring according to German regulation. These approved labs are required to prove their competencies by accreditation to ISO/IEC 17025:2005. In 2007 a quality management system (QMS), which was successfully audited and granted accreditation, was set up at the IVM. The system is based on the ISO 9001 certified QMS of the central safety department of the Research Centre Karlsruhe the IVM belonged to at that time. The system itself was set up to be flexible and could be adapted to the recent organisational changes (e.g. founding of KIT and an institute for radiation research) with only minor effort.

cited By 12; Diethylene Triamine Pentaacetic Acid (DTPA) is used for decorporation of plutonium because it is known to be able to enhance its urinary excretion for several days after treatment by forming stable Pu-DTPA complexes. The decorporation prevents accumulation in organs and results in a dosimetric benefit, which is difficult to quantify from bioassay data using existing models. The development of a biokinetic model describing the mechanisms of actinide decorporation by administration of DTPA was initiated as a task in the European COordinated Network on RAdiation Dosimetry (CONRAD). The systemic biokinetic model from Leggett et al. and the biokinetic model for DTPA compounds of International Commission on Radiological Protection Publication 53 were the starting points. A new model for biokinetics of administered DTPA based on physiological interpretation of C-labeled DTPA studies from literature was proposed by the group. Plutonium and DTPA biokinetics were modeled separately. The systems were connected by means of a second order kinetics process describing the chelation process of plutonium atoms and DTPA molecules to Pu-DTPA complexes. It was assumed that chelation only occurs in the blood and in systemic compartment ST0 (representing rapid turnover soft tissues), and that Pu-DTPA complexes and administered forms of DTPA share the same biokinetic behavior. First applications of the CONRAD approach showed that the enhancement of plutonium urinary excretion after administration of DTPA was strongly influenced by the chelation rate constant. Setting it to a high value resulted in a good fit to the observed data. However, the model was not yet satisfactory since the effects of repeated DTPA administration in a short time period cannot be predicted in a realistic way. In order to introduce more physiological knowledge into the model several questions still have to be answered. Further detailed studies of human contamination cases and experimental data will be needed in order to address these issues. The work is now continued within the European Radiation Dosimetry Group, EURADOS. Copyright © 2010 Health Physics Society.

A usercode for the EGSnrc Monte Carlo package has been developed for the simulation of whole-body counters with NaI(Tl) detectors in stretcher geometry. The geometry of the whole-body counter and the information about the detectors are specified in a plain text file, which enables users to easily adapt the codes to their installation. Bottle phantoms consisting of 1 and 2 l Cautex bottles filled with the radionuclide dissolved in water have been modelled as phantoms depicting the human body to be measured. These kind of phantoms can be defined by the users in the input file. Sets of efficiency factors for calculating activities from counts in measured spectra have been generated by two methods: 'direct simulation of nuclide decay' uses compiled data on photon energies and yields for all nuclides of interest and simulates a given number of decays of those nuclides for phantom masses from 10 to 100 kg while 'single-energy simulation' uses idealized 'nuclides' with single-energy emissions of 100 % yield to study the response of the systems over the energy range of interest (0-2000 keV in 20-keV steps). At University Hospital of Cologne and Karlsruhe Institute of Technology both methods have been successfully applied for the evaluation of spectra measured within intercomparison exercises.

Virtual models of real phantoms used with Monte Carlo methods facilitate the calibration and other studies associated with whole-body and partial-body counting systems. In this investigation, a voxel model of an LLNL torso phantom, available physically in the in vivo laboratory at KIT, was created from computed tomography scans. Series of measurements with a high-purity germanium detector and the real torso phantom, loaded with different radioactive organs, have been carried out. Computer simulations of these measurement setups were performed with the aid of MCNPX, using a coarsened voxel phantom and a validated model of the germanium detector. The results of simulations were compared with data from the measurements and an agreement within the uncertainties was found. The voxel model could therefore be validated. The results of the simulations were then used to quantify the activity of (241)Am impurities detected in the liver loaded with (239)Pu.

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. © The Author 2009. Published by Oxford University Press. All rights reserved.

The work of the Task Group 5.2 'Research Studies on Biokinetic Models' of the CONRAD project is presented. New biokinetic models have been implemented by several European institutions. Quality assurance procedures included intercomparison of the results as well as quality assurance of model formulation. Additionally, the use of the models was examined leading to proposals of tuning parameters. Stable isotope studies were evaluated with respect to their implications to the new models, and new biokinetic models were proposed on the basis of their results. Furthermore, the development of a biokinetic model describing the effects of decorporation of actinides by diethylenetriaminepentaacetic acid treatment was initiated.