Optimisation of monitoring programme of internal contamination by the study of uncertainty related to the dose assessment

En vue d optimiser la protection des travailleurs vis-à-vis des rayonnements ionisants, la réglementation française impose des limites de dose et une démarche de réduction progressive de l exposition, dans la continuité des recommandations de la Commission Internationale de Protection Radiologique. Afin de vérifier le respect des limites et contraintes de dose lorsqu un risque de contamination interne existe, des programmes de surveillance sont mis en place par des mesures radiotoxicologiques périodiques. Cependant, des incertitudes dans l interprétation dosimétrique de ces mesures sont introduites par leur variabilité propre et par la connaissance incomplète des conditions de contamination. Ces incertitudes ont été prises en compte par des techniques statistiques classique, bayésienne et possibiliste. La méthodologie développée a été appliquée à l évaluation de l exposition potentielle lors de la fabrication du combustible nucléaire et dans les mines d uranium, ainsi qu à l analyse du programme de surveillance des travailleurs des ateliers de purification du plutonium du site AREVA NC de La Hague.A partir du seuil de décision du comptage nucléaire, la dose minimale détectable (DMD) par le programme avec un niveau de confiance donné peut être calculée à l aide du logiciel Optimisation des Programmes de Surveillance de la Contamination Interne (OPSCI). Elle s avère un support utile à l optimisation des programmes de surveillance, en recherchant le meilleur compromis entre leur sensibilité et leur coût.To optimise the protection of workers against ionizing radiations, the International Commission on Radiological Protection recommends the use of dose constraint and limits. To verify the compliance of the means of protection with these values when a risk of internal contamination exists, monitoring programmes formed of periodic bioassay measurements are performed. However, uncertainty in the dose evaluation arises from the variability of the activity measurement and from the incomplete knowledge of the exposure conditions. This uncertainty was taken into account by means of classical, Bayesian and possibilist statistics. The developed methodology was applied to the evaluation of the potential exposure during nuclear fuel preparation or mining; and to the analysis of the monitoring programme of workers purifying plutonium in AREVA NC La Hague reprocessing plant.From the measurement decision threshold, the minimum dose detectable (MDD) by the programme with a given confidence level can be calculated through the software OPSCI. It is shown to be a useful support in the optimisation of monitoring programmes when seeking a compromise between their sensitivity and their costs.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Optimisation of monitoring programme of internal contamination by the study of uncertainty related to the dose assessment

En vue d optimiser la protection des travailleurs vis-à-vis des rayonnements ionisants, la réglementation française impose des limites de dose et une démarche de réduction progressive de l exposition, dans la continuité des recommandations de la Commission Internationale de Protection Radiologique. Afin de vérifier le respect des limites et contraintes de dose lorsqu un risque de contamination interne existe, des programmes de surveillance sont mis en place par des mesures radiotoxicologiques périodiques. Cependant, des incertitudes dans l interprétation dosimétrique de ces mesures sont introduites par leur variabilité propre et par la connaissance incomplète des conditions de contamination. Ces incertitudes ont été prises en compte par des techniques statistiques classique, bayésienne et possibiliste. La méthodologie développée a été appliquée à l évaluation de l exposition potentielle lors de la fabrication du combustible nucléaire et dans les mines d uranium, ainsi qu à l analyse du programme de surveillance des travailleurs des ateliers de purification du plutonium du site AREVA NC de La Hague.A partir du seuil de décision du comptage nucléaire, la dose minimale détectable (DMD) par le programme avec un niveau de confiance donné peut être calculée à l aide du logiciel Optimisation des Programmes de Surveillance de la Contamination Interne (OPSCI). Elle s avère un support utile à l optimisation des programmes de surveillance, en recherchant le meilleur compromis entre leur sensibilité et leur coût.To optimise the protection of workers against ionizing radiations, the International Commission on Radiological Protection recommends the use of dose constraint and limits. To verify the compliance of the means of protection with these values when a risk of internal contamination exists, monitoring programmes formed of periodic bioassay measurements are performed. However, uncertainty in the dose evaluation arises from the variability of the activity measurement and from the incomplete knowledge of the exposure conditions. This uncertainty was taken into account by means of classical, Bayesian and possibilist statistics. The developed methodology was applied to the evaluation of the potential exposure during nuclear fuel preparation or mining; and to the analysis of the monitoring programme of workers purifying plutonium in AREVA NC La Hague reprocessing plant.From the measurement decision threshold, the minimum dose detectable (MDD) by the programme with a given confidence level can be calculated through the software OPSCI. It is shown to be a useful support in the optimisation of monitoring programmes when seeking a compromise between their sensitivity and their costs.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Evaluating uncertainty on lifetime occupational dose from uranium through a EURADOS intercomparison

International audienceRecently, several epidemiological studies were interested in identifying potential health effects of dose from occupationally incorporated radionuclides. The data available for dose reconstruction are bioassay analyses (mostly urine) and exposure conditions recorded in a Job-Exposure Matrix (JEM) . However, those data were collected for radiological protection purposes rather than for precise retrospective dose assessments. Consequently, the uncertainty on the lifetime doses is assumed to be important. The same uncertainty is expected on dose estimates for compensation claims.In order to quantify this uncertainty, three cases of lifetime uranium exposure from the nuclear industry were distributed inside the European Radiation Dosimetry Group (EURADOS) to a number of participants for the purposes of an intercomparison exercise aiming: - to compare dose assessment protocols of the different participants- to identify sources of uncertainty, and - to discuss the assessment of uncertainty on dose.16 participants estimated total committed effective dose, total equivalent doses to the lungs and to the kidneys for at least one of the three workers. Worker 1 presented a large number of bioassay results and several recorded incidents; for Worker 2 only one result out of 19 was higher than the DL and this result was obtained at a time when exposure was not possible according to the JEM; the 75 bioassay results of Worker 3 were all below the detection limit.The dispersion of the dose assessments is important, higher than the factor of three usually acknowledged for uncertainty of internal doses. From the description provided by the participants, the protocols to evaluate doses were reviewed in details and sources of uncertainty along with reasonable modelling assumptions were identified. This work is published as EURADOS Report 2017-03 and will be used as a basis for defining guidelines to reconstruct lifetime doses for epidemiological studies and for compensation claims

Patient-specific biokinetics evaluation based on multiple SPECT images or hybrid planar/SPECT technique using OEDIPE 3D personalized dosimetry software: development and application

International audienceBackground:With the development of targeted radionuclide therapy, it has become increasingly necessary to develop comprehensive tools to compute 3D personalized dosimetry accounting for patient-specific biokinetics. For that purpose new functionalities were developed in OEDIPE software, to insure compatibility with different sets of patient images (multiple 3D images, multiple planar/SPECT images).Materiel & Method:Two new processes of image analyses were implemented and adapted to multiple time-point 3D images (SPECT/CT or PET/CT), and multiple planar images associated to a single SPECT/CT. Both processes enable recovering time-activity data for each volume of interest (VOI). A biokinetic module was developed to fit time-activity curves (TACs) to the obtained data and to calculate the cumulated activity in the VOIs. To evaluate the robustness of these developments, multiple SPECT/CT and planar images of a JASZCZAK phantom containing I-131 were consecutively acquired at different time-points. Cumulated activity of I-131 was estimated in each sphere using: (i) the SPECT/CT images only, and (ii) the planar series associated to one SPECT/CT out of the six available images, to quantify the influence of the selected time-point at which the SPECT was acquired. Results were compared with the known cumulated activity. To test the clinical applicability of these developments, cumulated activities in lesions and in the lungs of a patient treated for differentiated thyroid cancer were estimated using four planar images and a SPECT/CT scan acquired after I-131 administration. Whole-body retention data combined with SPECT activities were used to generate biokinetic data to compare with.Results:Activities and cumulated activities estimated using OEDIPE in the phantom spheres agreed well with the reference values for both approaches. Results obtained for the patient were similar with those derived from the method based on the whole-body retention data combined with SPECT activities.Conclusion:These new features of OEDIPE allow automatic evaluation of patient-specific biokinetics from different series of patient images, enabling efficient patient-specific internal dosimetry without the need for external software to estimate the cumulated activities in different VOIs.Keywords:targeted radionuclide therapy (TRT); radiopharmaceutical therapy (RPT); patient-specific biokinetics; 3D personalized internal dosimetry; Monte Carlo-based radiation transport code; OEDIPE dosimetric software; hybrid planar-SPECT dosimetr