Residual thermoluminescence for sun-bleached quartz: dependence on pre-exposure radiation dose.

thermoluminescence, à paraître dans Quaternary GeochronologyQuartz grains zeroed by heat and subsequently irradiated - either in the laboratory, or naturally in volcanic deposits - were exposed to sunlight for several months prior to TL measurements. As a result, the residual TL, either Blue or Red, appeared to grow significantly with the radiation-dose experienced by the grains since zeroing. In another experiment, un-heated sedimentary quartz grains, sampled at the very surface of a coastal sand-dune, were irradiated and subsequently exposed to sunlight before TL measurements. The residual Red-TL still exhibited a strong dose-dependence, but at a level which was higher than the natural signal. Finally, it was concluded that the so-called “un-bleachable TL” is not a constant, intrinsic data, for a given quartz sample. Because the residual TL is strongly correlated to the radiation dose experienced since the last zeroing by heat, it can theoretically be quoted in terms of “dose”, as sometimes done. However, this raises the question of its correct evaluation, and, on the other hand, there is a risk of misinterpretation of its physical meaning in the case of un-heated sediments. In the context of sediment dating, the experimentally-estimated residual signal that is routinely subtracted from the total signal for palaeodose estimation is therefore higher than the signal that would have been measured prior to burial. Such effect induces an error which can be significant for Red TL. It can be corrected for, at least roughly, from experimental exploration of the dose-dependence of the residual T

Uncertainty on radiation doses estimated by biological and retrospective physical methods

Biological and physical retrospective dosimetry are recognised as key techniques to provide individual estimates of dose following unplanned exposures to ionising radiation. Whilst there has been a relatively large amount of recent development in the biological and physical procedures, development of statistical analysis techniques has failed to keep pace. The aim of this paper is to review the current state of the art in uncertainty analysis techniques across the ‘EURADOS Working Group 10— Retrospective dosimetry’ members, to give concrete examples of implementation of the techniques recommended in the international standards, and to further promote the use of Monte Carlo techniques to support characterisation of uncertainties. It is concluded that sufficient techniques are available and in use by most laboratories for acute, whole body exposures to highly penetrating radiation, but further work will be required to ensure that statistical analysis is always wholly sufficient for the more complex exposure scenarios

Realising the European network of biodosimetry: RENEB-status quo

Creating a sustainable network in biological and retrospective dosimetry that involves a large number of experienced laboratories throughout the European Union (EU) will significantly improve the accident and emergency response capabilities in case of a large-scale radiological emergency. A well-organised cooperative action involving EU laboratories will offer the best chance for fast and trustworthy dose assessments that are urgently needed in an emergency situation. To this end, the EC supports the establishment of a European network in biological dosimetry (RENEB). The RENEB project started in January 2012 involving cooperation of 23 organisations from 16 European countries. The purpose of RENEB is to increase the biodosimetry capacities in case of large-scale radiological emergency scenarios. The progress of the project since its inception is presented, comprising the consolidation process of the network with its operational platform, intercomparison exercises, training activities, proceedings in quality assurance and horizon scanning for new methods and partners. Additionally, the benefit of the network for the radiation research community as a whole is addressed

Determinants of Refusal of A/H1N1 Pandemic Vaccination in a High Risk Population: A Qualitative Approach

International audienceBackground: Our study analyses the main determinants of refusal or acceptance of the 2009 A/H1N1 vaccine in patients with cystic fibrosis, a high-risk population for severe flu infection, usually very compliant for seasonal flu vaccine.Methodology/Principal Findings: We conducted a qualitative study based on semi-structured interviews in 3 cystic fibrosis referral centres in Paris, France. The study included 42 patients with cystic fibrosis: 24 who refused the vaccine and 18 who were vaccinated. The two groups differed quite substantially in their perceptions of vaccine- and disease-related risks. Those who refused the vaccine were motivated mainly by the fears it aroused and did not explicitly consider the 2009 A/H1N1 flu a potentially severe disease. People who were vaccinated explained their choice, first and foremost, as intended to prevent the flu’s potential consequences on respiratory cystic fibrosis disease. Moreover, they considered vaccination to be an indirect collective prevention tool. Patients who refused the vaccine mentioned multiple, contradictory information sources and did not appear to consider the recommendation of their local health care provider as predominant. On the contrary, those who were vaccinated stated that they had based their decision solely on the clear and unequivocal advice of their health care provider.Conclusions/Significance: These results of our survey led us to formulate three main recommendations for improving adhesion to new pandemic vaccines. (1) it appears necessary to reinforce patient education about the disease and its specific risks, but also general population information about community immunity. (2) it is essential to disseminate a clear and effective message about the safety of novel vaccines. (3) this message should be conveyed by local health care providers, who should be involved in implementing immunization

Datation par luminescence : recherches méthodologiques et applications au volcanisme dans l'environnement de Laschamp

N° d'ordre : DU 1739, EDSF : 528The aim of this work was to date lava flows from the Chaîne des Puys (Massif Central, France) which were chronologically situated during the period of the Laschamp paleomagnetic event (30-50 ka). The methods used were thermoluminescence and optically stimulated luminescence applied to quartz grains and quartz pebbles extracted from sediments baked by the lava flows. These minerals often emit luminescence signals exhibiting erratic behaviour. Thus, their palaeodoses were tentatively determined by various methods to select those which were most likely to yield reliable results. These intercomparisons highlighted a dispersion of results beyond what could be expected from the uncertainties usually associated with each measurement. In the majority of cases, these observations forced us to propose a relatively wide interval in which the most probable age of the sample is included.L'objectif de ce travail était de dater des coulées volcaniques de la Chaîne des Puys (Massif Central, France) situées chronologiquement dans la période de l'événement paléomagnétique de Laschamp (30-50 ka). Les méthodes utilisées étaient la thermoluminescence et la luminescence stimulée optiquement appliquées à des grains de quartz et à des galets quartzeux extraits de sédiments cuits par ces coulées. Ces minéraux émettent des signaux de luminescence dont le comportement est souvent irrégulier. Leur paléodose a donc été déterminée par différentes méthodes pour choisir celles qui seraient les plus appropriées à l'obtention de résultats fiables. Ces intercomparaisons ont mis en évidence une dispersion des résultats supérieure à ce qui pouvait être attendu au regard des incertitudes habituellement associées à chacune d'entre elles. Dans la plupart des cas, ces observations ont conduit à proposer un intervalle assez large dans lequel est compris l'âge probable de l'échantillon

Radiation accident dosimetry on plastics by epr spectrometry

In case of acute exposure to ionizing radiation, the dose absorbed by the victims has to be rapidly and accurately assessed in order to choose an appropriate medical treatment. Tooth enamel and bone biopsies measured by EPR spectrometry are often used as dose indicators, due to the good radiation sensitivity and the stability of EPR radiation-sensitive signals. Nevertheless, the invasive sampling of teeth and bones limits the application of this technique to retrospective dosimetry. Therefore, we have investigated an alternative non-invasive methodology. We have surveyed with EPR spectrometry the dosimetric properties of the plastics that can be found in personal effects such as glasses (CR-39, polycarbonate), mobile phones (PMMA, polycarbonate), watches and buttons. Dose response, signal stability and effects of storage conditions were investigated. Significant signal fading limits the use for radiation accident dosimetry. Few plastics present the required characteristics to be used in case of a radiation accident. © 2010 Health Physics Society