Contribution of the French society for radiation protection to the current reflections onthe possible improvements of the radiological risk management system.Following the invitation from IRPA to comment on the article written by Professor Roger Clarke entitled"Control of Low Level Radiation Exposure: Time for a Change?", the Board of the French Society forRadiation Protection (SFRP) decided to set up a working group on "controllable dose". The latter, whichworked from April 1999 to July 2000, consisted of some twenty members representing the stakeholdersinvolved in radiological protection in France: authorities, experts and professionals from nuclear,medical and research fields as well as associative movement. The present article, which has been approvedby the Board of SFRP, summarises the findings of the WG presented during the IRPA-10 Congress in May 2000.The WG first examined the current hypothesis on radiological risk and noted their relevance for apractical management of such a risk. Then, a list of the different exposure situations and theirassociated characteristic was elaborated in a table form, followed by a discussion on the situations whenthe system of radiological protection fits well, less well or bad, particularly through the implementationof the general principles of radiological protection. The WG finally made proposals to ICRP for anevolution of the system towards a more operational way.

Le polonium 210 naturel, de période relativement courte (138 jours) et issu de la famille de l'uranium, devrait retenir davantage l'attention en radioprotection car il entraîne des doses chroniques plus élevées que les traces de césium 137 et de plutonium (238, 239 et 240) présentes dans l'environnement. Dans la croûte terrestre, l'uranium est accompagné du radium, du radon et de ses descendants, à des concentrations de l'ordre de 40 000 Bq t-1. Par le jeu de l'exhalaison du radon 222 des sols sur une couche métrique et des retombées du plomb 210 (descendant du radon), la couche superficielle des sols s'enrichit par rapport à la teneur en radium, d'un facteur variant de 2,7 à 8,8 en plomb 210 et en polonium 210 selon des mesures faites dans l'environnement. L'exposition de l'homme au polonium 210 par ingestion est notable. Elle est permanente et 30 à 70 fois plus importante que l'exposition au césium 137 des retombées de Tchernobyl à Helsinki en 1986, qui décroît selon la période radioactive de 30 ans. La toxicité par ingestion du polonium 210 est 500 à 2 000 fois plus élevée que celle du plutonium pour un même nombre de becquerels déposés au sol. Des “ points chauds ” peuvent se former dans certains compartiments de l'environnement : le polonium 210 se concentre particulièrement dans la faune marine, comme le montrent plusieurs campagnes de mesures dans la zone nord-est de l'Atlantique.

Treatment with thrombopoietin of the hematopoietic syndrome induced by lethal irradiation.The therapeutical efficacy of thrombopoietin, an haematopoietic cytokine, has been evaluated on improvement of haematopoietic syndrome, haematopoietic recovery and survival in C57BL6J mice following total body irradiation with a 60Co source (7-10 Gy). A single administration of 0.3 μg thrombopoietin 2 h after an irradiation of 9 Gy increased the 30-day survival. The survival enhancement was related to an accelerated haematopoietic recovery for all lineages and a decrease in bacterial infections. However, when the administration was delayed to 24 h after irradiation, thrombopoietin had a lower efficiency on both survival and haematopoietic recovery. We observed that half of the thrombopoietin-treated mice died between the 2nd and the 6th month after irradiation. This long-term mortality was likely to be due to thrombosis formation. In fact, we have demonstrated that thrombopoietin activates platelets which in turn enhance thrombosis formation in irradiated mice. In order to avoid thrombosis, we administered ticlopidine, an antagonist of platelet activation, to mice before irradiation. Almost all of the 9 Gy irradiated mice which received both thrombopoietin and ticlopidine survived up to 6 months, reaching the same efficiency than a bone marrow graft. In summary, we have shown that thrombopoietin treatment enhances survival of lethally irradiated mice in relation with protection from haematopoietic syndrome. Nonetheless, an anti-platelet drug might be associated with thrombopoietin to avoid thrombosis formation which might be lethal on a long-term basis.

The consequences of a severe nuclear accident on the agricultural environment, releasing 137Cs and 90Sr-enriched aerosols, have been studied within an original lysimetric facility driven in controlled conditions. Focal point of a research scope widely open to European collaborations, this facility has hosted several scientific programmes spread over about a decade (RESSAC and PEACE, notably), the principal achievements of which are provided in the form of a synthetic overview. After a brief reminder of the historical context strongly challenged by the Chernobyl accident within which this project has evolved, the originality of the instrumental set up used for simulating a nuclear accident at a small scale is presented. The addressed scientific aspects concern the clarification of radioecological mechanisms governing the behaviour of these two radionuclides in the soil-plant system. A particular focus is placed on foliar transfers and the resulting translocation, soil in-depth migration, chemical composition of the soil interstitial water, the influence of the later on root absorption which determines the soil-to-plant transfer, all aspects being stressed over a representative spectrum of plants, soil and climates. Based on a strategy of synergy between experiments and modelling developments, the achievements obtained are used to improve the predictive radioprotection tools.

An efficient but little known tool for the application of the ALARA principle: ISOE (Information System on Occupational Exposure).The Information System on Occupational Exposure to ionizing radiation (ISOE) is a program launched by the Nuclear Energy Agency (NEA) in 1992. It was developed to address the needs of nuclear power plants and safety authorities as a comparison and information tool on practices in terms of optimization (ALARA principle), in NEA member countries. To date, more than 90% of the operating nuclear power plants in the world are participating in this program, which is organized in a decentralized form, with a steering group and four technical centers (Europe, Asia, north America and IAEA). The ISOE program includes an occupational exposure database and an information exchange and communication network. The databases permit the preparation of studies and comparisons of practices, either in a factual or analytical way. Thus, the ISOE program favors exchanges to the benefit of all participants and helps to bring operational radiation protection ever closer towards the "achievable" of ALARA.

En cas d'accidents nucléaires, les iodes radioactifs, dont l'iode 131, peuvent être rejetés dans l'atmosphère. Par mesure de sécurité, une instruction du Premier ministre de 1997 ordonne la distribution préventive des comprimés d'iode stable (KI) aux populations voisines des installations nucléaires afin que celle-ci soit déjà effective en situation accidentelle. Auparavant, les comprimés étaient stockés par Électricité de France (EDF) et mis à disposition des pouvoirs publics. Les comprimés distribués en 1997 arrivant à leur date de péremption, EDF a dû mettre en place cette année une nouvelle campagne de distribution dans un rayon de dix kilomètres autour de ses 20 sites en fonctionnement correspondant à 58 réacteurs nucléaires. Lors des réunions d'information, les questions sur l'efficacité de cette mesure de protection, la nature et la fréquence des éventuels effets secondaires tout en mesurant sa durée d'action selon les conditions d'administration, ont été abordés. Une étude bibliographique sur la cinétique de l'iode dans l'organisme humain a permis d'établir indications et mode d'emploi. L'efficacité du blocage de l'incorporation d'iode radioactif dans la thyroïde et la survenue d'un dysfonctionnement thyroïdien dépendent de facteurs externes (apports alimentaires d'iode) et individuels (état fonctionnel de la thyroïde, âge du sujet...). Si l'exposition à l'iode radioactif devait durer plusieurs jours, et dans l'objectif d'une protection maximale, l'éventualité d'une deuxième prise d'iode stable pourrait se poser. Ce travail présente l'impact des campagnes d'information (1997 et 2000) et de mise à disposition des populations des comprimés d'iode stable, l'implication des populations, et les réactions des professionnels de santé.

Radiological impact assessment of very low-level radioactive waste management pathways.Two approaches are currently being adopted for the management of very low-level waste (VLLW): disposal insurface facilities and, for some categories of VLL waste, the implementation of treatment and utilisationchannels. In this paper, the orders of magnitude of the radiological consequences which may result fromthese two options are discussed, in a matter of a description rather than a comparison. As regards disposal, radiological impact is presented through a generic case, along with the uncertainties stemmingfrom the variability of the parameters associated with its design, as well as those associated with thegeosphere and the biosphere. In the case of treatment and utilisation channels, such as disposal orrecycling of VLL waste oils or VLL wastes containing asbestos, the assessment of radiological consequencesdeals with the public exposure and with the occupational exposure on the basis of a stage-by-stagebreakdown of the industrial process.

In the case of accidental exposure to ionising radiation, estimation of the absorbed dose in the organismis an important indicator for evaluating the biological consequences. To complete the clinical andbiological investigations, physical dosimetry methods can be used to provide an estimate of the absorbeddose and its distribution in the organism. This article describes the development of calculation tools inphysical dosimetry, in particular a numerical anthropomorphic phantom which can be adapted to eachindividual. A standard model was developed from the data available in the ICPR Publication 23. A set oftests was carried out with the model dimensions being modified to study the effect of morphology on thedose calculation. A comparison was made with another standard model used in internal dosimetry. Thesestudies highlight the parameters to be taken into account in the model, depending on whether the accidentis local or global.

Procedure for direct determination of uranium in urine by ICP-MS.Estimation of the internal exposure of personnel by radioactive substances, especially actinides, is one of the subjects of great importance in human radiological protection. Because of constant changes in industrial processes in the nuclear fuel cycle and new radiological protection regulations, means to perform routine individual monitoring and to estimate internal exposure of workers in an accident situation must be high-efficient. The method described here is the determination of uranium in urine by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry), directly after a simple 20-fold dilution of the urine samples. Optimisation of the operational parameters has led to propose an analytical procedure that allows the determination of mass concentration for each uranium isotope. Calculations of associated uncertainties and corresponding detection limits are detailed.

Plasma Flt3-ligand as a prognostic bio-indicator of radiation-induced bone marrow damage.Following an accidental irradiation, the choice between different therapeutic strategies mainly depends upon the estimated radiation-induced bone marrow damage. It was shown recently that the serum concentration of Flt3-ligand (FL), a cytokine mainly acting on immature haemopoietic cells, is highly elevated in either acquired or induced bone marrow aplasia. This suggested to us that FL measurement could be used as a bio-indicator of radiation-induced bone marrow damage. In order to verify this hypothesis, studies were conducted in a non human primate model as well as in humans undergoing radio and/or chemotherapy. Results showed that the increase in FL concentration on day 5 after irradiation is predictive of the evolution of the haemopoietic syndrome. Similar results were obtained in humans. Overall these results suggested that FL measurement could be used as a reliable bio-indicator of radiation-induced bone marrow damage in accidental irradiation situations.

Les accidents causés par les rayonnements ionisants sont rares et possèdent leur propre spécificité. Ils ont des effets indirects, particulièrement importants dans les accidents de grande ampleur. La gamme des accidents est large et variée : il existe des accidents qui ne posent pas de problèmes particuliers, des accidents dont la gestion médicale est délicate et des accidents qui mobilisent des moyens très importants. Dans chacune de ces classes on peut distinguer les accidents qui sont diagnostiqués d'emblée et ceux qui sont découverts tardivement et qui auraient pu être ignorés. Certains accidents sont gardés secrets pour des raisons militaires ou politiques. Cette classification permet de tirer un enseignement général, qui devrait contribuer à la prévention et à la gestion des situations accidentelles, tant en ce qui concerne la sûreté que le domaine médical.

Although great efforts had been made to improve the physical phantoms used for calibrating in vivo measurement systems, for technical reasons they can only provide a rough representation of humantissue.Substantial corrections must therefore be made to calibration factors obtained with suchcalibration phantoms for extrapolation to a given individual. These corrections are particularly crucialand delicate in low-energy in vivo measurement when absorption in tissue is significant. To improvecalibration for such special conditions, the possibility has been raised of using voxelised numericalphantoms associated with Monte Carlo computing techniques. In the method described below, a mathematicalphantom, consisting of a voxelised representation derived from scanner images is used, with aspecially-designed interface making it possible to not only reconstruct widely-differing contaminationconfigurations and specify associated tissue compositions, but also automatically create an MCNP4b inputfile. After validation of the different sources and geometries, the complete procedure of reconstructionof the phantom and simulation of 241Am lung measurement was carried out using a tissue equivalentcalibration phantom of the type commonly used for lung calibration for actinides. The purpose of this workwas to extend the use of this principle to the reconstruction of numerical phantoms on the basis ofphysiological data of individuals obtained from magnetic resonance and scanner images. The resultsobtained and the current limitations of this approach in the context are discussed.

Dosimetric control: report of French submarine forces from 1989 to 1999.We report on the Ile Longue strategic site and describe the medical and dosimetric monitoring of nuclear submarine crews. Over the past eleven years, dosimetric results of nuclear submarine crews have been gathered. We have compared these results to those of workers employed by outside enterprises and the directorate of naval constructions. During this period, neither the crew members nor the workers have been over-exposed. Considering each group, we show a more or less distinct diminution of equivalent doses.

Accidental exposure to ionising radiation may occur during such catastrophic events as the Chernobyl accident in 1986 or for days and weeks as in Goiania in 1987 and in the military camp during the training of soldiers in Lilo/Georgia in 1997 as well as in medical institutions. The cutaneous symptoms after radiation exposure are based on a combination of inflammatory processes and alteration of cellular proliferation as a result of a specific pattern of transcriptionally activated proinflammatoric cytokines and growth factors. They follow a time course consisting of prodromal erythema, manifestation, chronic stage, late stage and they are referred to as Cutaneous Radiation Syndrome. The time course depends on several factors such as the applied radiation dose, radiation quality, individual radiation sensitivity, the extent of contamination and absorption and volume of the skin. For diagnostics of the cutaneous radiation syndrome the following procedures are used: 7.5 MHz to 20 MHz-B-scan-sonography, thermography, capillary microscopy, profilometry, nuclear magnetic resonance imaging, bone scintigraphy and histology. Based on the results of experimental and clinical research of the last years pharmacotherapy of the cutaneous radiation syndrome includes topic or systemic application of corticosteroids, gamma-interferon, pentoxifylline and vitamin E and superoxide dismutase. The treatment depends on the stage of the cutaneous radiation syndrome. Due to the complexity of the clinical manifestations of radiation disease in most patients an interdisciplinary treatment in specialised centres is necessary. Dermatologists are asked to perform in most cases life-long therapy and follow-up of the patients.

At the end of July 1998, three 137Cs sources (between 0.17 and 150 GBq) were found in the vicinity of the village of Matkhoji, located at 300 km to the west of Tbilissi. This site was a former Russian military base, abandoned since 1992 and used now as pasture and a playground for the children. The Georgian Environment Ministry requested assistance from IAEA which sent a mission to the site. This established that a predominantly chronic exposure of part of the population of the village has occurred. The IAEA requested technical assistance from IPSN. A mission, made up of 4 people from IPSN and a representative of the IAEA went to the site from 12 to 17 October 1998. This mission collected information on the circumstances of the exposure and selected a potentially explored cohort of 112 people, in three groups: children of more than five years and adults of less than 50 years attending the site and members of a family who had a source in their cattle shed. An analysis of hematologic parameters was performed on these people and 85 blood samples were taken for biological dosimetry. The hematologic analysis carried out on the spot did not show any particular anomaly. The biological dosimetry by scoring of unstable chromosome aberrations (dicentric, rings centric, fragments) in blood peripheral lymphocytes was performed on blood samples after air transportation to the specialised laboratory (LDBM) of the IPSN Two successive procedures were initiated. The first was a quick phase of triage not very precise but intended to check if some of these people presented obvious signs of irradiation. Only 50 cells per subject were scored. Seven days were needed to complete this phase. Dicentrics were found in three people only indicating a whole-body dose not exceeding 0.5 Gy on average. This triage was followed of a more complete but longer examination, where chromosome aberrations were scored in 250 cells. Six weeks were necessary to score 22 000 cells from the 85 people. In total, 30 dicentrics were scored among only 17 Georgian patients. The highest dose to the whole body estimated from a reference calibration curve was 0.3 Gy The majority of these dicentrics was found in the children having played on several occasions in the former military camp. Unfortunately, the information provided by the population was too fragmentary to permit an effective reconstruction of the individual doses.