RADON INHALATION EXPERIMENTS TO TEST RADON EXHALATION KINETICS

Three experiments were conducted with a volunteer to test the kinetics of the 222Rn exhalation after a short-time exposure to an elevated 222Rn air concentration. Radon concentration in an exhaled air was measured, complemented by whole body counting of 222Rn decay products in a body. Exhaled activities are compared with the prediction of the recent ICRP biokinetic model for radon. While a rapid equilibration of the exhaled radon activity concentration with that in the air inhaled corresponded with the model, the measured 222Rn exhalation rate was significantly less than modelled. Five hours after termination of the inhalation phase, the radon concentration in the exhaled air decreased to levels expected for non-elevated indoor radon activity concentration. Whole body activities of the 222Rn decay products were found higher than expected. Inhalation of the unattached fraction or residual activity of decay products in the air inhaled may be the explanation.

Eurados review of retrospective dosimetry techniques for internal exposures to ionising radiation and their applications

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.

The valley system of the Jihlava river and Mohelno reservoir with enhanced tritium activities

The Dukovany nuclear power plant (NPP Dukovany) releases liquid effluents, including HTO, to the Mohelno reservoir, located in a deep valley. Significantly enhanced tritium activities were observed in the form of non-exchangeable organically bound tritium in the surrounding biota which lacks direct contact with the water body. This indicates a tritium uptake by plants from air moisture and haze, which is, besides the uptake by roots from soil, one of the most important mechanisms of tritium transfer from environment to plants. Results of a pilot study based on four sampling campaigns in 2011-2015 are presented and discussed, with the aim to provide new information on tritium transport in the Mohelno reservoir - Jihlava River - plants ecosystems.

MONTE CARLO SIMULATION OF THE BREMSSTRAHLUNG RADIATION FOR THE MEASUREMENT OF AN INTERNAL CONTAMINATION WITH PURE-BETA EMITTERS IN VIVO

Rapid measurement techniques are required for a large-scale emergency monitoring of people. In vivo measurement of the bremsstrahlung radiation produced by incorporated pure-beta emitters can offer a rapid technique for the determination of such radionuclides in the human body. This work presents a method for the calibration of spectrometers, based on the use of UPh-02T (so-called IGOR) phantom and specific (90)Sr/(90)Y sources, which can account for recent as well as previous contaminations. The process of the whole- and partial-body counter calibration in combination with application of a Monte Carlo code offers readily extension also to other pure-beta emitters and various exposure scenarios.

A simple physical phantom for an intercomparison exercise on 241Am activity determination in the skull

A simple hemispherical phantom has been designed and prepared for the EURADOS intercomparison exercise on (241)Am activity determination in the skull (2011-13). The phantom consists of three parts that substitute bone and soft tissues. (241)Am is deposited on the surfaces of the bone-substituting part. The design and assumed composition of phantom parts are discussed. A preparation of the voxel representation of the phantom is described. The spectrum of a real measurement of the physical phantom agrees well with the simulation. The physical phantom, and its voxel representation, is provided to the participants of the intercomparison exercise.

A case of occupational internal contamination with 241Am

An internal contamination with (241)Am was detected in a worker during a routine monitoring of workers from a company producing Am sources for smoke detectors and Am-Be neutron sources. During the 4-year period after the exposure, the number of urine and faecal samples from the worker were analysed; in vivo measurements were also performed. Specific values for absorption parameters of the human respiratory tract model and particle transport values were applied to improve the model fit to the measurement data. A good agreement of the bioassay data with the so-modified model predictions was obtained.

Reassessment of individual dosimetry of long-lived alpha radionuclides of uranium miners through experimental determination of urinary excretion of uranium

Urinary excretion of uranium of 40 uranium miners was determined by the high-resolution inductively coupled mass spectrometry method. The concentration of uranium in the urine of the miners was converted to daily excretion of (238)U either under the assumption that the daily urinary excretion is 1.6 l or daily urinary excretion of creatinine is 1.7 g and compared with the excretion of (238)U calculated with a biokinetic model. Input data to the excretion model were derived from personal three- component ALGADE dosemeters, using the component for the estimation of inhalation of long-lived alpha radionuclides. Experimentally found contents of uranium in the urine of uranium miners are generally lower than the modelled ones, which means that the dosimetric approach is conservative. The uncertainty of inhalation intakes, derived from the measurements of filters from personal dosemeters, and the uncertainty of the concentration of uranium in the urine are discussed.

Content of uranium in urine of uranium miners as a tool for estimation of intakes of long-lived alpha radionuclides

Uranium in the urine of 10 uranium miners (hewers), 27 members of general population and 11 family members of miners was determined by the High-Resolution ICP-MS method. Concentration of uranium in urine of the miners was converted to daily excretion of (238)U under the assumption that the daily excretion of urine is 2 l and compared with the modelled excretion of (238)U. Daily excretion of (238)U was modelled using input data from personal dosemeters from a component for measurement of intake of long-lived alpha radionuclides. A reasonable agreement between evaluated and measured values was found. The uncertainty of inhalation intakes, derived from measurements of filters from personal dosemeters, and uncertainty of concentration of uranium in urine are discussed.

Validation of environmental transfer models and assessment of the effectiveness of countermeasures using data on (131)I releases from Chernobyl

The studies undertaken by the (131)I Working Group, part of the International Atomic Energy Agency's EMRAS (Environmental Modelling for Radiation Safety) programme, were focused primarily on evaluating the predictive capability of environmental models. Particular emphasis was placed on applying models to evaluate the effectiveness of countermeasures.

Evaluation of committed effective doses from internal contamination of 241Am using experimentally determined parameters of the contaminant

Internal contamination of workers with 241Am has occurred a few times since the beginning of the 1970s, mainly in the workplace where radionuclide sources were produced, and later on, also during liquidation of radioactive waste. Contamination in workers was measured in vivo and bioassay was performed. Solubility of aerosol in lungs was studied by in vitro dissolution test with a simulant solution of the extracellular airway lining fluids. Model calculation for the estimation of intakes was done with the experimentally obtained parameters of aerosol, with modified times of intake, with scattering factors, including Types A and B errors, and with corrections on skull size for in vivo measurements. For most cases, an acceptable fit to the experimental data was obtained; for two cases with intakes taking place long time ago ( approximately 30 y), some changes in the model are necessary.

Radiation exposure to the population of Europe following the Chernobyl accident

On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of (131)I for children aged 1 y were found to vary from approximately 0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from approximately 0 in Portugal to approximately 10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each country.

Assessment of occupational doses from internal contamination with 241Am

A group of workers with occupational intakes of 241Am, which occurred a long time ago, has been followed for some time. Results of in vivo measurement and bioassay of excreta are compared with the values predicted by the ICRP Publication 78 model. The observed skeletal content is, as a rule, higher than the predicted one. The ratio of excreted activity in urine to that in faeces is in very good agreement with the model prediction. Another group of workers from a waste management department, who were internally contaminated in July 2001, has also been followed. In some cases, there is quite a large difference in calculated intake between excretion by urine and that by faeces. The contaminant was presumably the same as that in the group of workers with old intakes, but its physical and chemical form could be influenced by a fixating lacquer used to prevent the spread of contamination.