Analytical investigation and experimental application of the source modulation technique to measure ρ/βeff\rho/\beta_{eff}

In recent years great interest has been displayed, worldwide, for Accelerator Driven Sub critical reactors (ADS) to incinerate the minor actinides generated by the existing energy producing reactors. In sub critical systems, the effective neutron multiplication factor is lower than 1.0 and the neutrons otherwise required to maintain the chain reaction, can be put to other uses, in particular, the destruction of nuclear wastes such as minor actinides (MA). One of the major advantages of such ADS systems is that it can be operated with very high M.A content without jeopardizing the overall safety due to a small effective delayed neutron fraction, a small Doppler temperature coefficient and possibly also a large void coefficient depending on the chosen coolant. This enhanced safety however prerequisites at all time a sufficient subcriticality margin. Reliable reactivity monitoring techniques are hence required to achieve this goal. The MUSE-4 program is a series of low power experiments carried out at the CEA-Cadarache MASURCA facility to investigate the various methods leading to the measurement of the reactivity level and associated kinetic parameters such as the effective delayed neutron fraction. The aim of this paper is to present the results obtained with a method which directly gives the ratio, for a sub critical assembly, between the reactivity ρ and the effective delayed neutron fraction βeff. By combining these results to those obtained with the kp-method for the prompt neutron multiplication coefficient, we have access to the parameters which govern the prompt and the slow kinetics of a sub critical assembly. These parameters can be obtained without reference to any calibration measurement in critical configuration. It opens the way to the control of larger sub critical demonstrators which are operating with fuels which cannot be used in critical reactor, and, thanks to sub criticality, which are characterized by a deterministic safety

Analytical model for SiC based power converter optimization including EMC and thermal constraints

International audienceA Model dedicated to EMI prediction in a DC-DC converter is presented in this paper. The model is analytical to be used by a deterministic optimization algorithm. This model not only predicts EMI but also thermal effects of the converter. Numerical and experimental validation of the model are performed regarding EMC aspects and perspectives for the final optimization purpose are presented

Radiation protection, radiation safety and radiation shielding assessment of hie-isolde

The high intensity and energy ISOLDE (HIE-ISOLDE) project is an upgrade to the existing ISOLDE facility at CERN. The foreseen increase in the nominal intensity and the energy of the primary proton beam of the existing ISOLDE facility aims at increasing the intensity of the produced radioactive ion beams (RIBs). The currently existing ISOLDE facility uses the proton beam from the proton-synchrotron booster with an energy of 1.4 GeV and an intensity up to 2 mA. After upgrade (final stage), the HIE-ISOLDE facility is supposed to run at an energy up to 2 GeV and an intensity up to 4 mA. The fore-seen upgrade imposes constrains, from the radiation protection and the radiation safety point of view, to the existing experi-mental and supply areas. Taking into account the upgraded energy and intensity of the primary proton beam, a new assessment of the radiation protection and radiation safety of the HIE-ISOLDE facility is necessary. Special attention must be devoted to the shielding assessment of the beam dumps and of the experimental areas. In this work the state-of-the-art Monte Carlo particle transport simulation program FLUKAwas used to perform the computation of the ambient dose equiva-lent rate distribution and of the particle fluxes in the projected HIE-ISOLDE facility (taking into account the upgrade nominal primary proton beam energy and intensity) and the shielding assessment of the facility, with the aim of identifying in the existing facility (ISOLDE) the critical areas and locations where new or reinforced shielding may be necessary. The conse-quences of the upgraded proton beam parameters on the operational radiation protection of the facility were studied

Evaluation of the radiation field and shielding assessment of the experimental area of HIE-ISOLDE

The ISOLDE facility at CERN is one of the first facilities in the world dedicated to the production of the radioactive ion beams (RIB) and during all its working time underwent several upgrades. The goal of the latest proposed upgrade, ‘The High Intensity and Energy ISOLDE’ (HIE-ISOLDE), is to provide a higher performance facility in order to approximate it to the level of the next generation ISOL facilities, like EURISOL. The HIE-ISOLDE aims to improve significantly the quality of the produced RIB and for this reason the increasing of the primary beam power is one of the main objectives of the project. An increase in the nominal beam current (from 2 to 6 μA proton beam intensity) and energy (from 1.4 GeV to 2 GeV) of the primary proton beam will be possible due to the upgrade of CERN’s accelerator infrastructure. The current upgrade means reassessment of the radiation protection and the radiation safety of the facility. However, an evaluation of the existing shielding configuration and access restrictions to the experimental and supply areas must be carried out. Monte Carlo calculations were performed in order to evaluate the radiation protection of the facility as well as radiation shielding assessment and design. The FLUKA—Monte Carlo code was used in this study to calculate the ambient dose rate distribution and particle fluxes in the most important areas, such as the experimental hall of the facility. The results indicate a significant increase in the ambient dose equivalent rate in some areas of the experimental hall when an upgrade configuration of the primary proton beam is considered. Special attention is required for the shielding of the target area once it is the main and very intensive radiation source, especially under the upgrade conditions. In this study, the access points to the beam extraction and beam maintenance areas, such as the mass separator rooms and the high voltage room, are identified as the most sensitive for the experimental hall from the radiation protection point of view

Ultraviolet–visible–near-infrared optical properties of amyloid fibrils shed light on amyloidogenesis

Amyloid fibres attract considerable interest due to their biological role in neurodegenerative diseases and their potential as functional biomaterials. Here, we describe an intrinsic signal of amyloid fibres in the near-infrared range. When combined with their recently reported blue luminescence, it paves the way towards new blueprints for the label-free detection of amyloid deposits in in vitro and in vivo contexts. The blue luminescence allows for staining-free characterization of amyloid deposits in human samples. The near-infrared signal offers promising prospects for innovative diagnostic strategies for neurodegenerative diseases—to improve medical care and for the development of new therapies. As a proof of concept, we demonstrate direct detection of amyloid deposits within brains of living, aged mice with Alzheimer’s disease using non-invasive and contrast-agent-free imaging. Ultraviolet–visible–near-infrared optical properties of amyloids open new research avenues for amyloidosis as well as for next-generation biophotonic devices