High prevalence of HPV infection in the remote villages of French Guiana: an epidemiological study.

Cervical cancer is the second most frequent cancer in women in French Guiana. Studies have shown that populations living in the remote areas of the interior have early sexual debut and that multiple sexual partnerships are common. The objective of the present study was thus to determine the prevalence of human papillomavirus (HPV) infection in these areas. A study was conducted in women aged 20-65 years with previous sexual activity. Women were included on a voluntary basis after using local media and leaders to inform them of the visit of the team. HPV infection was defined by the detection of HPV DNA using the Greiner Bio-One kit. In addition to HPV testing cytology was performed. The overall age-standardized prevalence rate was 35%. There was a U-shaped evolution of HPV prevalence by age with women aged >50 years at highest risk for HPV, followed by the 20-29 years group. Twenty-seven percent of women with a positive HPV test had normal cytology. Given the high incidence of cervical cancer in French Guiana and the high prevalence of HPV infections the present results re-emphasize the need for screening for cervical cancer in these remote areas. Vaccination against HPV, preferably with a nonavalent vaccine, also seems an important prevention measure. However, in this region where a large portion of the population has no health insurance, this still represents a challenge.

[Dengue virus infection in neotropical forest mammals: incidental hosts or potential reservoirs?]. / Infection par le virus de la dengue de mammifères sauvages en région néotropicale: hôtes accidentels ou réservoirs potentiels?

The arboviral disease with the highest human incidence in South America is dengue fever. In French Guiana, where all four dengue serotypes, i.e., DENV-1, DENV-2, DENV-3 and DENV-4, are present, the disease is endemic with epidemic outbreaks. Though previous serological studies have suggested a sylvatic cycle, involvement of wild mammals in the dengue cycle in the neotropics has never been confirmed. The purpose of this study was to search for the presence of DENV in wild animals captured at two different sites between 2001 and 2007. About 10,000 trap/nights were performed leading to the capture of 464 non-flying mammals (rodents and marsupials). In addition, mistnests placed in the same zone yielded 152 bats. Reverse transcription-polymerase chain reaction amplification to detect infection by any of the four dengue serotypes demonstrated viral RNA in the livers and/or sera of 92 captured animals. Sequence analysis of amplification products revealed that the DENV-1, DENV-3 and DENV-4 serotypes were distinct from those circulating in humans at the same periods. Analysis for DENV-2 showed that some strains were divergent from concurrent human strains but that others were identical. The latter finding suggests that wild neotropical mammals living in periurban area can be infected by dengue virus strains circulating in humans. However, further investigation will be needed to determine if neotropical mammals are incidental hosts or potential reservoirs of dengue virus.

Analysis of the CONRAD computational problems expressing only stochastic uncertainties: neutrons and protons.

Within the scope of CONRAD (A Coordinated Action for Radiation Dosimetry) Work Package 4 on Computational Dosimetry jointly collaborated with the other research actions on internal dosimetry, complex mixed radiation fields at workplaces and medical staff dosimetry. Besides these collaborative actions, WP4 promoted an international comparison on eight problems with their associated experimental data. A first set of three problems, the results of which are herewith summarised, dealt only with the expression of the stochastic uncertainties of the results: the analysis of the response function of a proton recoil telescope detector, the study of a Bonner sphere neutron spectrometer and the analysis of the neutron spectrum and dosimetric quantity H(p)(10) in a thermal neutron facility operated by IRSN Cadarache (the SIGMA facility). A second paper will summarise the results of the other five problems which dealt with the full uncertainty budget estimate. A third paper will present the results of a comparison on in vivo measurements of the (241)Am bone-seeker nuclide distributed in the knee. All the detailed papers will be presented in the WP4 Final Workshop Proceedings.

Design of a new IRSN thermal neutron field facility using Monte-Carlo simulations.

The Institute for Radiological Protection and Nuclear Safety owns a graphite-moderated AmBe neutron field facility, SIGMA, that has to be reconstructed. Monte-Carlo simulations were performed to study the design of a new thermal facility based on IRSN existing facilities. Studies related to an update version of SIGMA concerned the enhancement of the thermal neutrons contribution to the dose equivalent. Calculations were mainly performed for a (252)Cf neutron source distribution located at the centre of a graphite moderator block. A quasi-pure thermal neutron field was obtained with a 2.4 x 2.4 x 2.4-m(3) block of graphite. A second acceptable neutron field was obtained with 3.3-MeV mono-energetic neutrons created by a 400-kV accelerator coupled to a graphite assembly of 1.5 x 1.5 x 1.5 m(3). The characteristics of the studied thermal fields with the requirement for a reference calibration field are compared, and the advantages and drawbacks of the different producing methods are discussed.

Monte Carlo simulation of the operational quantities at the realistic mixed neutron-photon radiation fields CANEL and SIGMA.

The Institute for Radiological Protection and Nuclear Safety owns two facilities producing realistic mixed neutron-photon radiation fields, CANEL, an accelerator driven moderator modular device, and SIGMA, a graphite moderated americium-beryllium assembly. These fields are representative of some of those encountered at nuclear workplaces, and the corresponding facilities are designed and used for calibration of various instruments, such as survey meters, personal dosimeters or spectrometric devices. In the framework of the European project EVIDOS, irradiations of personal dosimeters were performed at CANEL and SIGMA. Monte Carlo calculations were performed to estimate the reference values of the personal dose equivalent at both facilities. The Hp(10) values were calculated for three different angular positions, 0 degrees, 45 degrees and 75 degrees, of an ICRU phantom located at the position of irradiation.

Neutron spectrometry around the VENUS reactor using Monte Carlo simulations and Bonner spheres measurements.

This paper presents the assessment of the neutron field near the VENUS reactor, particularly in areas near the reactor shielding where operators are frequently present during a reactor run. To obtain reference spectra in the area of interest, MCNPX simulations were performed. Reference spectrometry was also performed using a Bonner spheres system. The outcome of both calculations and measurements is compared.

Investigation of the neutron energy distribution of the IRSN 241Am-Be(alpha,n) source.

The neutron energy distribution of the IRSN standard 241Am-Be(alpha,n) source was measured using a proton recoil liquid scintillator, BC501A, >1.65 MeV. The experimental data were compared with the ISO recommended neutron energy distribution for an Am-Be source and some significant discrepancies were observed. Monte Carlo simulations were then performed to investigate on the neutron source term in order to consider the different parameters between the IRSN Am-Be source and the one used to establish the neutron emission spectrum recommended by the ISO standard. The variation of the parameters of the source did not explain the remaining discrepancies. A good agreement with the experimental results was observed when the theoretical neutron energy distribution from Geiger and Van der Zwan was introduced in the study as new source term. These investigations showed that the ISO recommended Am-Be distribution might not be well suited to represent the neutron energy distribution of all Am-Be sources, and that the manufacturing of the sources might play a major role in the neutron fluence energy distribution.

Set-up of a passive Bonner sphere system for neutron spectrometry at mixed fields with predominant photon component based on activation detector.

A passive Bonner sphere system (BSS), based on thermal neutron activation detectors, was developed to perform neutron spectrometry in pulsed and very intense (n-gamma) fields with predominant photon component, as those produced by high energy (>10 MV) medical linear electron accelerators. In this paper, a description of the new system is presented together with an experimental characterisation of a portable Sodium Iodide (NaI) detector and a fixed high-purity Germanium one, both used to measure the induced gamma-activity of the activated materials, respectively, in situ and in the laboratory. The choice of the activated materials is justified according to pre-established practical considerations and physical criteria. The response functions of the entire passive BSS were calculated using the MCNPX code. A preliminary experimental validation with a bare (252)Cf source is given as well.

Energy and direction distribution of neutrons in workplace fields: implication of the results from the EVIDOS project for the set-up of simulated workplace fields.

Workplace neutron spectra from nuclear facilities obtained within the European project EVIDOS are compared with those of the simulated workplace fields CANEL and SIGMA and fields set-up with radionuclide sources at the PTB. Contributions of neutrons to ambient dose equivalent and personal dose equivalent are given in three energy intervals (for thermal, intermediate and fast neutrons) together with the corresponding direction distribution, characterised by three different types of distributions (isotropic, weakly directed and directed). The comparison shows that none of the simulated workplace fields investigated here can model all the characteristics of the fields observed at power reactors.

Bonner sphere neutron spectrometry at nuclear workplaces in the framework of the EVIDOS project.

The Institute for Radiological protection and Nuclear Safety was engaged in the EC funded EVIDOS project to provide reference spectrometry data using its Bonner sphere system. The data were processed by means of two unfolding codes, NUBAY and GRAVEL, both provided by the Physikalisch-Technische Bundesanstalt. The NUBAY program, based on Bayesian parameter estimation methods, assumes a parameterised spectrum and provides posterior probability distributions for the parameters. The code GRAVEL, an iterative algorithm based on SAND-II, was used with various default spectra, among them the NUBAY solution. The BS measurements were used to establish the neutron fluence energy distributions and reference values for the neutron ambient dose equivalent. As this quantity depends strongly on the high energy neutrons, a sensitivity analysis was done by unfolding the BS data with GRAVEL using the NUBAY solution spectrum as default with various changes in the parameters of the high energy peak. This new method of analysing Bonner sphere data allowed the determination of reliable neutron spectra, as well as a very good estimate of the corresponding integral quantities with small associated uncertainties.

Photon contribution to ambient dose equivalent H(10) in the wide-spectrum neutron reference fields of the IRSN.

The photon contribution to ambient dose equivalent in several wide-spectrum reference neutrons fields of the Institute for Radiological Protection and Nuclear Safety were measured using a Geiger-Müller counter. For the investigated fields, the ratio of photon to neutron ambient dose equivalent ranged between 0.03 and 0.20. The results show that the Geiger-Müller tube is a versatile instrument for dosimetry in mixed photon-neutron fields if sufficient information for the calculation of corrections is available.

Monte Carlo calculations and validation of a gold foil-based Bonner sphere system.

The Grup de Física de les Radiacions (GFR) of the Universitat Autònoma de Barcelona (UAB), in collaboration with the Institute for Radiological Protection and Nuclear Safety (IRSN), has developed a passive Bonner sphere system (UAB-BSS), with gold foils as thermal neutron detectors, for application in pulsed neutron fields or in mixed neutron-photon fields with high photon intensities. In such fields, active devices suffer from saturation and dead-time effects. The MCNPX Monte-Carlo code has been used to determine the response to neutrons of different energies of each polyethylene sphere belonging to the BSS. The passive UAB-BSS system was characterised with the ISO (252)Cf reference source at the IRSN facilities. The energy distribution of the reference source neutron fluence was folded with the response functions for comparison with the experimental data. A good agreement between the experimental and calculated count rates was found.

Achievements in workplace neutron dosimetry in the last decade: lessons learned from the EVIDOS project.

The availability of active neutron personal dosemeters has made real time monitoring of neutron doses possible. This has obvious benefits, but is only of any real assistance if the dose assessments made are of sufficient accuracy and reliability. Preliminary assessments of the performance of active neutron dosemeters can be made in calibration facilities, but these can never replicate the conditions under which the dosemeter is used in the workplace. Consequently, it is necessary to assess their performance in the workplace, which requires the field in the workplace to be fully characterised in terms of the energy and direction dependence of the fluence. This paper presents an overview of developments in workplace neutron dosimetry but concentrates on the outcomes of the EVIDOS project, which has made significant advances in the characterisation of workplace fields and the analysis of dosemeter responses in those fields.

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: Scope and methods of the project.

Supported by the European Commission, the EVIDOS project started in November 2001 with the broad goal of evaluating state of the art dosimetry techniques in representative workplaces of the nuclear industry. Seven European institutes joined efforts with end users at nuclear power plants, at fuel processing and reprocessing plants, and at transport and storage facilities. A comprehensive programme was devised to evaluate capabilities and limitations of standard and innovative personal dosemeters in relation to the mixed neutron-photon fields of concern to the nuclear industry. This paper describes the criteria behind the selection of dosimetry techniques and workplaces that were analysed, as well as the organisation of the measurement campaigns. Particular emphasis was placed on the evaluation of a variety of electronic personal dosemeters, either commercially available or previously developed by the partners. The estimates provided by these personal dosemeters were compared to reference values of dose equivalent quantities derived from spectrometry and fluence-to-dose equivalent conversion coefficients. Spectrometry was performed both with conventional multisphere and with some original instrumentation providing energy and direction resolution, based on silicon detectors and superheated drop detectors mounted on or in spherical moderators. The results were collected in a large, searchable database and are intended to be used in the harmonisation of dosimetric procedures for mixed radiation fields and for the approval of dosimetry services in Europe.

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part II: Conclusions and recommendations.

The paper presents the main conclusions and recommendations derived from the EVIDOS project, which is supported by the European Commission within the 5th Framework Programme. EVIDOS aims at evaluating state of the art neutron dosimetry techniques in representative workplaces of the nuclear industry with complex mixed neutron-photon radiation fields. This analysis complements a series of individual papers which present detailed results and it summarises the main findings from a practical point of view. Conclusions and recommendations are given concerning characterisation of radiation fields, methods to derive radiation protection quantities and dosemeter results.

The problems associated with the monitoring of complex workplace radiation fields at European high-energy accelerators and thermonuclear fusion facilities.

The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities. The paper provides an overview of the report, which will be available as CERN Yellow Report.

Characterisation of mixed neutron photon workplace fields at nuclear facilities by spectrometry (energy and direction) within the EVIDOS project.

Within the EC project EVIDOS, 17 different mixed neutron-photon workplace fields at nuclear facilities (boiling water reactor, pressurised water reactor, research reactor, fuel processing, storage of spent fuel) were characterised using conventional Bonner sphere spectrometry and newly developed direction spectrometers. The results of the analysis, using Bayesian parameter estimation methods and different unfolding codes, some of them especially adapted to simultaneously unfold energy and direction distributions of the neutron fluence, showed that neutron spectra differed strongly at the different places, both in energy and direction distribution. The implication of the results for the determination of reference values for radiation protection quantities (ambient dose equivalent, personal dose equivalent and effective dose) and the related uncertainties are discussed.

Direction distributions of neutrons and reference values of the personal dose equivalent in workplace fields.

Within the EC project EVIDOS, double-differential (energy and direction) fluence spectra were determined by means of novel direction spectrometers. By folding the spectra with fluence-to-dose equivalent conversion coefficients, contributions to H*(10) for 14 directions, and values of the personal dose equivalent Hp(10) and the effective dose E for 6 directions of a person's orientation in the field were determined. The results of the measurements and calculations obtained within the EVIDOS project in workplace fields in nuclear installations in Europe, i.e., at Krümmel (boiling water reactor and transport cask), at Mol (Venus research reactor and fuel facility Belgonucléaire) and at Ringhals (pressurised reactor and transport cask) are presented.

Application of workplace correction factors to dosemeter results for the assessment of personal doses at nuclear facilities.

Ratios of H(p)(10) and H*(10) were determined with reference instruments in a number of workplace fields within the nuclear industry and used to derive workplace-specific correction factors. When commercial survey meter results together with these factors were applied to the results of the locally used personal dosemeters their results improved and became within 0.7 and 1.7 of the reference values or better depending on the response of the survey meter. A similar result was obtained when a correction was determined with a prototype reference instrument for H(p)(10) after adjustment of its response. Commercially available survey instruments both for photon and neutron H*(10) measurements agreed with the reference instruments in most cases to within 0.5-1.5. Those conclusions are derived from results reported within the EC supported EVIDOS contract.

Neutron area survey instrument measurements in the EVIDOS project.

Neutron survey instruments have been exposed at all the measurement locations used in the EVIDOS project. These results have an important impact in the interpretation of the results from the project, since operationally the survey instrument will be used for an initial assessment of and routine monitoring of the ambient dose equivalent dose rate. Additionally, since the response of these instruments is in some cases very well characterised, their systematic deviations from the reference quantities provide an important verification of the determination of those quantities.