Comité de Rédaction

La contamination radioactive, qu’elle soit de nature surfacique ou atmosphérique, peutêtre la cause d’une exposition interne de l’individu. Les valeurs Limites pratiques deconcentration dans l’air (LPCA) permettent aux médecins du travail ainsi qu’aux Personnescompétentes en Radioprotection (PCR) de pré-évaluer les risques résultant d’unecontamination atmosphérique. Ces valeurs sont utilisées pour déterminer la conduite àtenir au poste de travail mais aussi comme outil d’optimisation de la protection despersonnes dans le cadre de l’application du principe ALARA (As Low As ReasonablyAchievable). Lors des analyses de poste, les PCR des laboratoires Pierre Fabre ont étéconfrontées à des valeurs de dose efficace engagée qui semblaient, de leur point de vue,anormalement élevées. Ces valeurs étaient en contradiction avec les résultats des examensde radiotoxicologie urinaire réalisés dans le cadre de la surveillance médicale renforcéedes manipulateurs, qui se sont toujours avérés négatifs (que ces examens soient effectuéspériodiquement ou de façon ponctuelle à la fin d’une série de manipulations radioactives).C’est pourquoi il a été jugé pertinent de louer des systèmes de barboteurs, équipementsutilisés pour la surveillance des faibles niveaux de concentration en tritium et carbone14. Les mesures réalisées ont permis de mettre en évidence des niveaux de contaminationatmosphérique en tritium négligeables, notamment lors des étapes de manipulation jugéesa priori pénalisantes. Ce travail, mené dans le cadre des études deposte, nous a permis d’abaisser la valeur du facteur de volatilité des composés tritiésintervenant dans le calcul de dose efficace engagée.

Indoor radon surveys were carried out in some of the Arabcountries through a Coordination Research Program (CRP) organizedby the Arab Atomic Energy Agency (AAEA). The objectives of the programaim at establishing a database on indoor radon concentration levelsin the region and investigating any anomalies, where they exist.The approach adopted by the survey teams to achieve public participationin accepting the radon detectors in dwellings is presented and discussed.Most of the participants in the CRP used the passive method (CR-39plastic detectors) for long-term radon measurements, while othersused charcoal detectors and E-Perm systems for short-term measurements.The results of the surveys showed that radon concentration levelsin most of the dwellings were low, whilst in some old cities andin an area close to a phosphate mine the levels were found to berelatively high.

The knowledge of the absorbed radiation dose is essential in order to interpret theresults of animal experiments with chronic ingestion of radionuclides by rodents. In orderto evaluate this absorbed dose, we applied the dose conversion factors proposed by ICRPpublication 108 to mouse chronic ingestion experiments with 20 kBq.L-1 137Cs-or 90Sr-contaminated water. The results indicated that whole-body absorbeddoses were 9 mGy and 10 mGy by the end of 20 weeks of 137Cs or 90Sringestion, respectively. These results of dose calculations were compared with resultsobtained with a more refined method using published organ-specific absorbed fractions ofenergy. There was good agreement between the two methods, indicating that, despite thesimple hypotheses used to apply the ICRP 108 dose conversion factors to our mouse model,this method allows one to calculate in a simple and reliable way the absorbed radiationdose received by the rodents during long-term experiments on chronic ingestion ofradionuclides.

The aim of our study was to distinguish the stress-related molecular response of thepulmonate mollusc Lymnaea stagnalis from the Chernobyl area in comparisonwith the consequences of other harmful effects, including the short-term effects ofradiation and heating. Specimens inhabiting ponds near the Chernobyl nuclear power plant,the cooling channel of the electric power station and the soil-reclamation channel (groupsR, T and C, correspondingly), and specimens adapted to laboratory conditions (a controlgroup (CL), a disposable group exposed to 2 mGy X-ray radiation over the body (RL), and agroup exposed to 25 °C for 4 days (TL)) were compared. Despite high variability ofresponses, Principle Component Analysis distinctly separated the laboratory and feralgroups into two sets. In the feral groups, low levels of the stress-related andmetal-binding protein metallothionein (MT), protein carbonyls and lactate dehydrogenase inthe digestive gland were indicated. The main separating criteria selected byclassification and regression tree analysis were the protein carbonyls, cholinesterase andMT. Molluscs from group R were clearly distinguished by the lowest levels of MT,Mn-superoxide dismutase and lactate dehydrogenase, and the highest level of glutathione,demonstrating that the oppression of the gene-determined stress-related response and itspartially metabolic compensation can be possible markers for chronic environmental effectsof irradiation.

The radioactivity concentrations of 226Ra, 232Th and 40Kwere measured using gamma-ray spectroscopy with NaI (Tl) detectors in four tantalitemining sites in the Oke-Ogun area, South-Western Nigeria. The measured values of theactivities of 40K, 226Ra and 232Th in the soil sampleswere found to lie in the ranges 123.7 ± 3.8 – 1372.3 ± 8.6, 16.8 ± 1.6 – 71.1 ± 2.53 and3.0 ± 0.7 – 31.9 ± 1.0 Bq kg–1, respectively. These samples were also found to have radiumequivalent activity in the range 74.2–121.0 Bq kg-1. Values of 0.2–0.3 for the externaland 0.3–0.4 for the internal hazard indices were estimated for the samples and the annualeffective dose varied from 70.3 ± 13.5 to 100.8 ± 42.8 µSv with a mean of 87.5 ± 18.6 µSvy–1. The annual effective dose is higher than the world average.

Inhalation of indoor radon has been recognized as thelargest contributor to the total effective dose received by humanbeings. Indoor radon data were collected from the dwellings lyingon the sedimentary rocks (sandstones, siltstones and clays) ofthe Murree Formation, Nagri Formation, Dhok Pathan Formation, Mirpurconglomerate and surficial deposits of the Kotli area in Azad Jammuand Kashmir, Pakistan. Radon measurements were made using the passivetime-integrated method using Kodak CN-85 Solid-State Nuclear Track Detectors.The radon concentration in dwellings varied from 13 ± 6 Bq.m-3 to185 ± 23 B. qm-3, with an average of 73 ± 15 Bq.m-3.Theradon concentration in the Murree Formation, Nagri Formation, riverterrace and Dhok Pathan Formation were 89.7 ± 16.5, 72 ± 15, 68.5and 69 Bq.m-3, respectively. The average value of allthe measured concentrations (73 ± 15 Bq.m-3) within theframework of this study is more than the world average value of40 Bq.m-3 given by UNSCEAR (United Nations ScientificCommittee on the Effects of Atomic Radiation, report to the GeneralAssembly, United Nations, New York, 2000) and is within the actionlevel of 200-600 Bq.m-3 fixed by the ICRP(InternationalCommission on Radiological Protection, ICRP publication65, Protectionagainst radon at home and at work, 1993). The ambient gamma doserates both indoors and outdoors in different parts of Kotli werealso measured. The average value of gamma absorbed dose rates prevailingin the indoor environment was 131.2 ± 16.6 nGy/h. The gamma exposurerates recorded outdoors were 35% lower than in the indoor environment.The measured gamma dose rates have a weak positive correlation withindoor radon concentration. The annual effective dose for inhabitantsin Kotli due to radon ranged from 0.32 to 4.7 mSv.y-1,with an average value of 1.8 mSv.y-1. This dose is relativelyhigher than the world mean dose of 1.15 mSv/y. That is explainedby the particular geology of the state of Azad Jammu and Kashmir,and the method of construction of the dwellings.

Calculations are presented of the effective dosesper unit neutron fluence according to the ICRP publications 60 and 103.Monte Carlo N-Particle (MCNPX) code was used for six geometricalconditions of irradiation (Anterior-Posterior, Posterior-Anterior,Left-Lateral, Right-Lateral, Rotation and Isotropic) on Oak RidgeNational Laboratory (ORNL) modified mathematical adult phantomsfor monoenergetic neutrons from 10-9 MeV to 20 MeV. The conversioncoefficients were compared with the results of an analytical phantom(Medical Internal Radiation Dose (MIRD-5)) and some voxel model(ICRP/ICRU Reference Voxel Phantom (ICRP/ICRU RVP), HANAKO, TAROand Visible Human Project (VIPMAN)). From these comparisons, one canconclude that large discrepancies between data sets appear whenwR and different sizes of the phantoms have been used for calculations.Furthermore, the differences in applied Monte Carlo codes or simulatedbody models could make some discrepancies less than 15%.

The assessment of the radiological impact of a decommissionednuclear power plant is presented here through the results of anenvironmental monitoring survey carried out in the area surroundingthe Garigliano Power Plant. The levels of radioactivity in soil,water, air and other environmental matrices are shown, in whichα, β and γ activity and the γ equivalent dose rate are measured.Radioactivity levels of the samples from the Garigliano area areanalyzed and then compared with those from a control zone situatedmore than 100 km away. Moreover, a comparison is made with a previous surveycarried out in 2001. The analyses and comparisons show no significantalteration in the radiological characteristics of the area surroundingthe plant, with the overall radioactivity depending mainly on theglobal fallout and natural sources.

En France, les effluents générés par des personnes traitéeset hospitalisées en médecine nucléaire doivent être collectés dansdes cuves de décroissance avant leur rejet dans le réseau d’assainissement,en accord avec les limites règlementaires définies. Un modèle utilisantune série d’exponentielle décroissante a été mis au point permettantde simuler l’évolution de l’activité volumique dans les cuves de décroissance.Ainsi son utilisation permet d’optimiser le nombre et la capacitédes cuves par rapport à l’activité médicale actuelle ou future.En outre, ce modèle est très modulable puisqu’il intègre comme variables :la période physique du radioélément, le volume total de chaque cuve,l’activité excrétée par patient, le volume total d’effluents généréspar patient durant son séjour en chambre blindée, le nombre de patientspris en charge lors de chaque semaine et le nombre de semaines avantla mise en décroissance de la cuve. Par ailleurs, les simulationsavec ce modèle montrent qu’à activité médicale équivalente, il estpossible de travailler soit avec 2 grandes cuves soit avec 3 cuvesayant une capacité réduite de 50 %. L’utilisation de plusieurs petitescuves permet en outre de maintenir la rotation des cuves de décroissanceen cas de mise hors service d’une d’entre elles.