[en] This paper describes a number of incidents involving the detection of radioactive materials which have occurred at Spanish steel plants in the period since the Protocol came into effect. The incidents illustrate the procedures followed in Spain for their management and the interaction of the government organizations and private companies as a result of the Protocol. The lessons learned from the incidents and the resulting changes brought about in procedures are described. (author)

[en] Polarimetry is the method of recording the state of polarization of light. Imaging polarimetry extends this method to recording the spatially resolved state of polarization within a scene. Imaging-polarimetry data have the potential to improve the detection of manmade objects in natural backgrounds. We have constructed a midwave infrared complete imaging polarimeter consisting of a fixed wire-grid polarizer and rotating form-birefringent retarder. The retardance and the orientation angles of the retarder were optimized to minimize the sensitivity of the instrument to noise in the measurements. The optimal retardance was found to be 132(degree) rather than the typical 90(degree). The complete imaging polarimeter utilized a liquid-nitrogen cooled PtSi camera. The fixed wire-grid polarizer was located at the cold stop inside the camera dewar. The complete imaging polarimeter was operated in the 4.42-5(micro)m spectral range. A series of imaging experiments was performed using as targets a surface of water, an automobile, and an aircraft. Further analysis of the polarization measurements revealed that in all three cases the magnitude of circular polarization was comparable to the noise in the calculated Stokes-vector components

[en] The Spanish Environmental Surveillance Radiological Network (REVIRA) has about 25 automatic stations and several associated laboratories (normally universitary labs) distributed over the state. The automatic network has been designed to measure dose rate and alpha, beta, radon and iodine air concentration. The measurement equipments consist of a ZnS(Ag) plastic scintillator, a NaI(T1) cristal detector and a GM detector. The automatic stations are connected with a Control center sited in the Nuclear Safety Council headquarter in Madrid. The connection uses the National Telephonic Network and the central software is able to call from the Control Center to each local station, call from the stations if a setpoint is reached and call from the Control Center to set up the microprocessor governing the local stations. (author)

[en] The CSN has been assigned with several functions in the management of nuclear or radiologic emergencies, such as the technical assessment to the authorities for the decision making on the forgoing steps and measures. The article describes the emergency reply organization prepared by the CSN with the description of a practical example: the tracking from the SALEM of an internal emergency rehearsal in the Asco nuclear power station. (Author) 6 refs

[en] When a wave propagates in a non homogeneous fluctuating plasma part of the incident energy is scattered out to the nonlinear interaction between the wave and the oscillating modes perturbing the plasma. The possibility of enhanced scattering at the cutoff layer, where reflection of the incident wave occurs, has been recently suggested as the basis of a reflectometric experiment to determine the spatial location of small scale fluctuations in a fusion plasma. Here we report on the development of a theoretical model to evaluate the flux of energy scattered by fluctuations, in order to give insight about the interpretation of measurements using a microwave reflectometry diagnostic in a tokamak. The scattered field is obtained through the resolution of a (non-homogeneous) wave propagation equation where the source term is related with the nonlinear current due to the interaction between the incident wave and local fluctuations. We use a slab model for the plasma, and an ordinary (0) wave propagation along the density gradient is considered. The amplitude of the scattered wave at the border of the plasma is estimated. In order to know the contributions to the energy scattered both from the propagation region and the reflecting layer, an approach was used where perturbations are modelled by spatial step functions at several layers. The main contribution to the scattered power comes from the cutoff region, where the electric field amplitude swells as compared with the incident value. Considering the reflectometric system recently installed on the ASDEX tokamak, and using typical density profiles, expected values of the 'swelling factor' have been numerically evaluated. The role of incoherent scattering due to drift wave activity is discussed as well as the coherent scattering due to fluctuations induced by lower hybrid (LH) waves. (author) 2 refs., 4 figs

[en] The loosely bound structure of halo nuclei is predicted to affect the collisions with heavy targets at energies around the Coulomb barrier. We report here on the results on a series of experiments done at different facilities to study the behaviour of the scattering of the archetype of the halo nuclei: "6He, "1"1Li, and "1"1Be on heavy targets at energies below and around the Coulomb barrier. The results are interpreted in the framework of Continuum-Discretized Coupled-Channel calculations (CDCC). The departure from Rutherford scattering is larger than expected. In first approximation the effect certainly scales with the loosely bound character of the projectile. (author)

[en] The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction process such as, elastic scattering, fusion and direct reactions when comparing collision induced by the ⁶He and ¹¹Be halo nuclei with the ones induced by their cores ⁴He and ¹⁰Be. Collisions induced by the stable weakly bound nuclei ⁶Li, ⁷Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. We have shown that, in collisions induced by halo nuclei, a strong suppression of the elastic scattering cross-section and, correspondingly, a large enhancement of the total reaction cross-section has been observed. Core excitation effects and coupling with the 1n-transfer channel are also found to be important in the elastic scattering with halo nuclei. In elastic scattering with weakly bound stable nuclei coupling to continuum effects are found to be very important. Fusion excitation functions in collisions induced by halo nuclei suggest the presence of a fusion cross-section enhancement around the barrier which is due mainly (but not only) to static effects

[en] We present some recent applications of the Continuum-Discretized Coupled-Channels (CDCC) and Coupled-Reaction-Channels (CRC) methods to the study of reactions induced by weakly-bound nuclei on stable targets. The methods are applied to the scattering of the Borromean nucleus ⁶He at energies around the Coulomb barrier. Elastic scattering data are very well described by four-body CDCC calculations (based on a three-body description of the ⁶He nucleus) but also by simpler three-body CDCC calculations, using a suitable two-body model for ⁶He. By contrast, inclusive data are better described using the CRC approach, which treats the breakup within the transfer to the continuum picture and, unlike the CDCC method, allows the inclusion of transfer to bound states of the target. We have also explored the possibility of calculating fusion cross sections within the CRC method. As in other works, the complete fusion cross section is estimated as the absorption of a short-range imaginary potential added to the bare interaction. We have applied this method to the ⁶He+²⁰⁸Pb and ⁶He+⁶⁴Zn reactions. In both cases, the calculation indicates that the inclusion of the transfer/breakup channels produces a significant suppression of the fusion probability at energies above the Coulomb barrier, improving the agreement with the data. (authors)

[en] The stopping power for "1"6O ions in "4He gas from 1 to 31 MeV is measured using an indirect method. The "1"6O beam of fixed energy entered a scattering chamber filled with "4He gas at different pressures and its residual energy is measured. The stopping power is determined by differentiating the thickness versus residual energy curve. The measured stopping power is compared with those calculated with the codes SRIM and MSTAR.

[en] We present an optical model (OM) analysis of the elastic scattering data of the reactions ⁶He + ²⁷Al and ⁶He + ²⁰⁸Pb at incident energies around the Coulomb barrier. The bare part of the optical potential is constructed microscopically by means of a double folding procedure, using the Sao Paulo prescription without any renormalization. This bare interaction is supplemented with a Coulomb dipole polarization (CDP) potential, which takes into account the effect of the dipole Coulomb interaction. For this CDP potential, we use an analytical formula derived from the semiclassical theory of Coulomb excitation. The rest of the optical potential is parametrized in terms of Woods-Saxon shapes. In the ⁶He + ²⁰⁸Pb case, the analysis confirms the presence of long range components, in agreement with previous works. Four-body Continuum-Discretized Coupled-Channels calculations have been performed in order to better understand the features of the optical potentials found in the OM analysis. This study searches to elucidate some aspects of the optical potential of weakly bound systems, such as the dispersion relation and the long range (attractive and absorptive) mechanisms.