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Eurados-ideas guidelines (version 2) for the estimation of committed doses from incorporation monitoring data

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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 3H 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.
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... For bioassay data analysis, the IMBA Professional Plus ® internal dosimetry software (Birchall et al 2007), special research version 5.0.0, was used to simultaneously fit urine data and postmortem activities in this individual's liver and skeleton with maximum likelihood method (Castellani et al 2013). The USTUR version of the software allows for building and solving compartmental systemic models for radionuclides. ...
... For data fitting, a log-normal error distribution was used for urine measurements with the overall uncertainties assigned based on recommendations of the IDEAS Guidelines (Castellani et al 2013). IDEAS recommends calculating the overall uncertainty of the measurements in terms of the scattering factors (SF) as follows: ...
... Since no information on counting statistics was provided in the bioassay records except for the last urine measurement reported with approximately 40% relative uncertainty, this value was used to define the Type A component of the overall uncertainty (SF A = 1.4) for all urine data. The SF B of 1.6, recommended for 24 h simulated urine bioassay (Castellani et al 2013), was used for measurements greater than the MDA, while larger Type B uncertainties (SF B of 2) were assigned to the data points below the MDA. This resulted in total SF of 1.8 and 2.2 for data greater and less than the MDA, respectively. ...
Article
Contaminated wounds are a common route of internal deposition of radionuclides for nuclear and radiation workers. They may result in significant doses to radiosensitive organs and tissues in an exposed individual's body. The United States Transuranium and Uranium Registries' (USTUR) whole-body donor (Case 0303) accidentally punctured his finger on equipment contaminated with plutonium nitrate. The wound was surgically excised and medically treated with intravenous injections of Ca-DTPA. A total of 16 g Ca-DTPA was administered in 18 treatments during two months following the accident. Ninety-three urine samples were collected and analyzed over 14 years following the accident. An estimated 239Pu activity of 73.7 Bq was excreted during Ca-DTPA treatment. Post-mortem radiochemical analysis of autopsy tissues indicated that forty years post-accident 21.6±0.2 Bq of 239Pu was retained in the skeleton, 12.2±0.3 Bq in the liver, and 3.7±0.1 Bq in other soft tissues; 1.35±0.02 Bq of 239Pu was measured in tissue samples from the wound site. To estimate the plutonium intake, late urine measurements, which were unaffected by chelation, and post-mortem radiochemical analysis results were evaluated using the IMBA Professional Plus software . Application of the National Council on Radiation Protection and Measurements (NCRP) wound model with an assumption of intake material as predominantly strongly retained soluble plutonium compound with a small insoluble fraction adequately described the data (p > 0.05). The effective intake was estimated to be 49.9 Bq of plutonium nitrate and 1.5 Bq of fragment. The prompt medical intervention with contaminated tissue excision and subsequent Ca-DTPA decorporation therapy reduced 239Pu activity available for uptake and long-term retention in this individual's systemic organs by a factor of 38.
... According to the ICRP publication 78 that provides a method for evaluating the internal exposure of workers 2) , it is suggested that a single intake can be estimated by dividing the radioactivity measurement by the radioactivity prediction for a unit intake. Furthermore, in the IDEAS guidelines that describe the evaluation procedures for internal exposures 3) , it is suggested that a single intake can be estimated from multiple measurements in which the uncertainly of measurement is considered. Generally, the intake estimation is obtained by fitting the radioactivity prediction structured with a linear combination of radioactivity prediction for the unit intake and the unknown intake quantity to the radioactivity measurement in the body or excretions. ...
... To employ the least squares method, the number of intakes must be lower than the number of measurements. From the ICRP 2) and IDEAS 3) guidelines, only a single intake was considered, and the estimation of multiple intakes was not sufficiently conducted. Using the intake estimation method with singular-value decomposition in this research, estimation was possible regardless of the dimensional relationship between the number of intakes and the number of measurements. ...
... The likelihood function described in IDEAS Guidelines (57) was used for the interpretation of most of the measurement values ...
... For urine and lung data, we used S values (see eq. 2) of 0.5 and 0.35, respectively, consistent with the recommendation in the IDEAS guidelines (57) . For most post-mortem measurements, an S of 0.1 was used, except for the LN TH measurement for Case 0269 where an S of 0.3 was used following Puncher et al. (3) . ...
Article
The respiratory tract tissues of four former nuclear workers with plutonium intakes were radiochemically analyzed post mortem by the United States Transuranium and Uranium Registries. Plutonium activities in the upper respiratory tract of these individuals were found to be higher than those predicted using the most recent biokinetic models described in publications of the International Commission on Radiological Protection. Modification of the model parameters, including the bound fraction, was not able to explain the data in one of the four individuals who had inhaled insoluble form of plutonium. Literature review points to the presence of—and a significant retention of—plutonium in the scar tissues of the lungs. Accordingly, an alternate model with scar-tissue compartments corresponding to larynx, bronchi, bronchioles, alveolar-interstitium and thoracic lymph nodes was proposed. The rates of transfer to the scar tissue compartments were determined using Markov Chain Monte Carlo analysis of data on urinary excretion, lung counts and post-mortem measurements of liver, skeleton and individual respiratory tract compartments, as available. The posterior models predicted that 20–100%—depending on the solubility of the material inhaled—of the activities retained in the respiratory tract were sequestered in the scar tissues.
... In general, the uncertainties due to both calibration and the variation of background signal could be controlled within 5%. 49 However, it is noted that all calibrations were performed with reference thyroid phantoms, and its uncertainty due to calibration should be further considered for individual monitoring. On the other hand, it was also pointed out that although uncertainties due to the variation of background signal could be relatively easily controlled by shielding or deducting the background, the MDA would significantly increase with the increase of environmental background signal especially in the case of nuclear accidents. ...
... For more accurate assessments of the internal dose, the EURADOS-IDEAS has established a guide. 49 Table 1 lists its general requirements on the typical scattering factors for in vivo measurement of radionuclides emitting photons with energy higher than 100 keV. Based on a previous review, it is still difficult to accomplish all the requirements in the in vivo monitoring of 131 I in the thyroid by using portable gamma spectrometers at present. ...
Article
Iodine-131 is a highly toxic and volatile artificial radionuclide that is easily inhaled or ingested by the human body and selectively accumulates in thyroid tissue. With the development of nuclear medicine and nuclear power plants, the unintended release of ¹³¹I has been widely studied, and the in vivo measurement of ¹³¹I in the thyroid has become a research hotspot in the field of radiation protection. In recent decades, several methods and devices have been developed for in vivo measurements with respect to different measurement purposes and requirements. In this work, for more accurate determinations of individual ¹³¹I activity in the thyroid in the field, the uncertainties of measurements by using portable gamma spectrometers were reviewed and analyzed, and monitoring strategies for improving the accuracy were proposed and prospected.
... It can be useful in detecting and quantifying an inhalation exposure to a relatively insoluble form of radionuclide, because clearance via feces is the predominant excretion mode in such a situation (17). Nevertheless, this method carries significant uncertainty as stated by EURADOS where it described that the transit time through the alimentary tract is subject to large inter/intra subject variations (21). ...
... assumed to be distributed lognormally with a geometric standard deviation (GSD) of 3.0 for measurements before 1949, a GSD of 2.0 for measurements between 1949 and 1957, and a GSD of 1.6 for measurements after 1957 [45]. The less than MDA/2 urine bioassay measurements were replaced by MDA/2 and marked as '<LOD' in IMBA. ...
Article
Full-text available
Purpose Radiation dose estimates in epidemiology typically rely on intake predictions based on urine bioassay measurements. The purpose of this article is to compare the conventional dosimetric estimates for radiation epidemiology with the estimates based on additional post-mortem tissue radiochemical analysis results. Methods The comparison was performed on a unique group of 11 former Manhattan Project nuclear workers, who worked with plutonium in the 1940s, and voluntarily donated their bodies to the United States Transuranium and Uranium Registries. Results Post-mortem organ activities were predicted using different sets of urine data and compared to measured activities. Use of urinalysis data collected during the exposure periods overestimated the systemic (liver+skeleton) deposition of ²³⁹ Pu by 155±134%, while the average bias from using post-exposure urinalyses was –4±50%. Committed effective doses estimated using early urine data differed from the best estimate by, on average, 196±193%; inclusion of follow-up urine measurements in analyses decreased the mean bias to 0.6±36.3%. Cumulative absorbed doses for the liver, red marrow, bone surface, and brain were calculated for the actual commitment period. Conclusion On average, post-exposure urine bioassay results were in good agreement with post-mortem tissue analyses and were more reliable than results of urine bioassays collected during the exposure.
... where k is the coverage factor, equal to 1.645 for a confidence level of 95%, t the acquisition time (equal to 180 s), P the number of channels for the peak region, n m the number of channels in the sidebands regions, n 0 the total number of counts in the sidebands regions (see Fig. 3), ε the measured efficiency and u(ε) the efficiency uncertainty, which is taken equal to 20% for all energies [14]. ...
Article
In a nuclear or radiological accident scenario, where members of the public can potentially take up anthropogenic radionuclides released in atmosphere, verified methods to fast screen for internal contamination a large number of individuals directly on the field can play a major role to adopt appropriate countermeasures. At the ENEA Casaccia Research Centre (Rome, Italy), a spectrometric monitoring method, based on a portable HpGe detector Trans-Spec-DX-100, has been developed. In this work, the results of the 2019 measurement campaign, where the method sensitivity was tested, in terms of detection limits (DL) for common fission and (some) activation products by acquiring gamma spectra on 102 uncontaminated volunteers (57 adults, 45 children between 7 and 12 years of age) are presented. The spectra, collected with acquisition time of 180 s, have been analysed according to the Standard ISO 28218 for the activity detection limit (Bq) calculations and according to ICRP Publications 134, 137, and 141 for the related minimum measurable committed effective dose. The measurements were taken in open field on a paved surface, in the presence of an environmental radiation background, given in term of ambient dose equivalent rate, H˙*(10), equal to 0.230 ± 0.020 μSv/h, in order to study both the potentiality and the limitation of the technique with a significant statistic. The results are presented and discussed particularly focusing on the specific characteristics of the technique, in respect to features reported by the European Council Directive 2013/59/Euratom and the International Atomic Energy Agency (IAEA) document STI/PUB/1708 (2015), and to techniques described in the current literature.
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After nuclear accidents, people can be contaminated internally via ingestion, inhalation and via intact skin or wounds. The assessment of absorbed, committed doses after internal exposure is based on activity measurement by in vivo or in vitro bioassay. Estimation of dose following internal contamination is dependent on understanding the nature and form of the radionuclide. Direct counting methods that directly measure γ-rays coming from within the body or bioassay methods that measure the amount of radioactive materials in urine or feces are used to estimate the intake, which is required for calculating internal exposure doses. The interpretation of these data in terms of intake and the lifetime committed dose requires knowledge or making assumptions about a number of parameters (time, type of exposure, route of the exposure, physical, biological and chemical characteristics) and their biokinetics inside the body. Radioactive materials incorporated into the body emit radiation within the body. Accumulation in some specific organs may occur depending on the types of radioactive materials. Decorporation therapy is that acceleration of the natural rate of elimination of the contaminant will reduce the amount of radioactivity retained in the body. This article presents an overview of treatment of radiological contamination after internal contamination.
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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.
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The PLUTO software package was developed at Sellafield to make optimum use of the analysis data from plutonium in urine samples in arriving at the best estimate of intake/uptake. The program prompts the assessment parameters required to fit the data to the excretion function using the maximum likelihood method. A critical appraisal is given of the relative strengths and weaknesses of this assessment package.
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Thorium is a natural radioactive element and has numerous applications. The extremely low annual limits on intake of national and international regulations and the extreme difficulties in detecting thorium in the body or excreta makes high demands on the techniques used for the monitoring of exposed workers. In addition, there are problems resulting from a lack of information on the biokinetics of thorium and its radioactive decay products. A programme for monitoring thorium intakes on the basis of new regulations in Germany, is described.
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