[en] ''High flux'' diodes offer advantages over other dosimetric methods in X-ray beams of very high instantaneous intensity: linear accelerators and flash generators. They allow the measurement of pulsed doses and dose rates up to 10¹⁰r.s.^-1, and give an immediate reading of the dose or peak dose rate by means of simple electronic devices

[en] Volcanic gases are very rich in long-lived radon daughters, especially in ²¹⁰Po. Thus more than 50 x 10³ Ci per year of ²¹⁰Po are injected into the troposphere by a normal volcanic activity, and more than 1 x 10³ Ci per year into the stratosphere by volcanic explosions. These fluxes should account for one half of the ²¹⁰Po content in both of these reservoirs. On the contrary the volcanic sources of ²²²Rn and ²¹⁰Pb are generally negligible with regard to the soil production. This new result could explain most of the discrepancies observed by comparing the activity ratios of the different radon daughters, including the existence of ²¹⁰Po/²¹⁰Pb figures superior to one (overequilibriums). Stratospheric aerosol residence times calculated on this basis are found to be shorter than the previous figures

[en] A comprehensive program is currently in progress at several laboratories for the development of sensitive, practical, non-destructive assay techniques for the quantification of low-level transuranics (TRUs) in bulk solid wastes. This paper describes the method being developed to assay high density TRU waste packages using photon interrogation. The system uses a pulsed electron beam from an electron linear accelerator to produce high-energy photon bursts from a metallic converter. The photons induce fissions in a TRU waste package which is inside an original neutron separating and counting cavity (NS2C). When fission is induced in trace amounts of TRU contaminants in waste material, it provides 'signatures' from fission products that can be used to assay the material before disposal. We give here the results from counting photofission-induced delayed neutrons from ²³⁹Pu, ²³⁵U and ²³⁸U in sample matrices. We counted delayed neutrons emitted after each pulse of the LINAC by using the sequential photon interrogation and neutron counting signatures (SPHINCS) technique which had been developed in the present framework. The SPHINCS method enhances the available counts by a factor of about 20 compared with the counting of delayed neutrons only, after the irradiation period. Furthermore, the use of SPHINCS measurement technique coupled with the NS2C facility improves the signal-to-noise ratio by a factor of about 30. This decreases the detection limit. The electron linear accelerator operates at 15 MeV, 140 mA, and 2.5 μs wide pulse at a 50 and 6.25 Hz rate. The dynamics of photofission and delayed neutron production, NS2C advantages and performances, use of an electron linear accelerator as a particle source, experimental and electronics details, and future experimental works are discussed

[en] This paper presents comparisons between photoneutron production measurements in tungsten, copper, praseodymium and beryllium, and calculated data resulting from the ELEPHANT (ELEctron, PHoton And Neutron Transport) code. Measurements were made using the DGA/ETCA linear electron accelerator located at Arcueil, France. Bremsstrahlung endpoints varying in the 15-25 MeV energy range were used. Detectors were positioned at different angles with respect to the electron beam axis. Each measured value is compared with the corresponding calculated value

[en] The simultaneous photon and neutron interrogation experiment (SIMPHONIE) method, applied to radioactive waste drum characterization, has already been treated in [F. Jallu, A. Lyoussi, C. Passard, E. Payan, H. Recroix, G. Nurdin, A. Buisson, J. Allano, Nucl. Instr. and Meth. B 170 (2000) 489]. First experimental results carried out with U and Pu bare samples were presented, that showed the feasibility of quantifying fissile (²³⁵U, ^239,241Pu, ...) and non-fissile (^234,236,238U, ^238,240Pu, ...) elements separately in only one measurement, using both active neutron interrogation and induced photofission interrogation techniques simultaneously. This paper presents new experimental results carried out with U samples embedded in a concrete matrix. These results have been obtained using the DGA/ETCA MiniLinatron pulsed linear electron accelerator located at Arcueil, France. Mass detection limits of less than 2 g of matter have been obtained with the preliminary setup used in these experiments

[en] Measuring α-emitters such as (^{234,235,236,238}U, ^{238,239,240,242,244}Pu, ²³⁷Np, ^241,243Am, ...), in solid radioactive waste allows us to quantify the α-activity in a drum and then to classify it. The simultaneous photon and neutron interrogation experiment (SIMPHONIE) method dealt with in this paper, combines both active neutron interrogation and induced photofission interrogation techniques simultaneously. Its purpose is to quantify fissile (²³⁵U, ^239,241Pu, ...) and non-fissile (^236,238U, ^238,240Pu, ...) elements separately in only one measurement. This paper presents the principle of the method, the experimental setup, and the first experimental results obtained using the DGA/ETCA Linac and MiniLinatron pulsed linear electron accelerators located at Arcueil, France. First studies were carried out with U and Pu bare samples

[en] After some generalities about the ²²²Rn and its daughters' behaviour in the troposphere, and the difficulties encountered with usual calculations of concentrations ratio between ²²²Rn and daughters made in different local points of the atmosphere, another point of view is introduced by comparing the global activities of these nuclides in the whole atmosphere instead of their local concentrations. This implies working out a two-box model, since the residence times of the aerosols and air masses are different in the troposphere and in the stratosphere. Such a model has been established by assuming the existence of a steady state for the whole atmosphere. Therefore, in each reservoir, the production of a nuclide by radioactive decay of its precursor is balanced simultaneously by its own radioactivity by the flux of atoms transferred to or from the other reservoir, and in the case of the troposphere, by scavenging. The model considers an unknown emanation of ²²²Rn from the soil of the continents and also the existence of possible volcanic extra sources for each nuclide. By using our original data and most of the results already published, it has been possible to evaluate independently the tropospheric reservoirs of ²²²Rn, ²¹⁰Pb, ²¹⁰Bi, ²¹⁰Po. On the contrary, the small content of ²²²Rn in the stratosphere seems to be variable and cannot be evaluated directly with the requested accuracy. Consequently, some of the results computed in this model are only given by a range of values which depend essentially on the intensity of ²¹⁰Po direct injections into the stratosphere by the volcanic explosions. So have been measured, with this model, the ²²²Rn emanation rate from soil of the continents, the percentage of that flux which reach the atmosphere, the mean residence time of the submicronic aerosols in the troposphere and the flux of air exchanged across the tropopause

[en] A comprehensive program is currently in progress at several laboratories for the development of sensitive, practical, non-destructive assay techniques for the quantification of low-level transuranics (TRU) in bulk solid wastes. This report describes the method being developed to assay high density TRU waste packages using photon interrogation. The system uses a pulsed electron beam from a linear accelerator (LINAC) to produce high-energy photon bursts from a metallic converter. The photons induce fissions in TRU. When fission is induced in trace amounts of TRU contaminants in waste material, it provides ''signatures'' from fission products that can be used to assay the material before disposal. The authors give here the results from counting photofission-induced delayed neutrons from ²³⁹Pu, ²³⁵U and ²³⁸U in sample matrices. They counted delayed neutrons emitted after each pulse of the LINAC. This enhances the available counts by a factor about 20 compared with the counting of delayed neutrons only after the irradiation period. The electron linear accelerator operates at 15 MeV, 140 mA, and 2.5 μs wide pulse at a 50 Hz rate. The dynamics of photofission and delayed neutron production, use of an electron linear accelerator as a particle source, experimental and electronics details, and a future experimental works are discussed

No abstract available

[en] In France radioactive waste inspection is doing in progress with several programs to quantify fertile and fissile isotopes and to follow their time evolution. The non destructive methods used on original techniques such as the Instrumental Photon Interrogation Assay (IPAA) and the Instrumental Neutron Interrogation Assay (INAA) are the most interesting. Presently we point out the performances got with an energy beam more than 6 MeV. The photonuclear reactions occur in waste nucleus give specific radioactive radiation easy to detect (specific gamma rays or fission neutrons). The photon radiation is produced by Bremsstrahlung process following the interaction electrons on heavy metal target. DGA firm has two electron linear accelerators which operate with range from 6 to 40 MeV. The present paper describes the potentialities of these radiation facilities and the associated instrumentation. (author)