The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Tritiated water detection in the 2.17 µm spectral region by cavity ring down spectroscopy

International audienceNuclear waste containers are intended to be stored in dedicated disposals sites. For the inside and environmental safety of the disposals site, the tiny outgassing rates leaking out the containers are measured. The radioactive HT gas is actually measured by liquid scintillation, however an alternative method, cavity ring down spectroscopy, is currently developed for tritium measurement in its oxidized form HTO and evaluated. The HTO molecule concentration is determined by the measurement of spectroscopic parameters from transitions on its harmonic 21 (R) transitions between 4590 and 4600 cm-1. Two tritiated water standards are measured with a dedicated CRDS set-up. Compared to the theoretical database, the line positions are correct (-0.067 to -0.128 cm-1), their relative intensities is in agreement with the database, but their absolute intensities are 30% weaker. Among the seven intense lines, the 4596.485 cm-1 line (intensity 8.22 10-22 cm/molecule) and the 4592.407 cm-1 line (intensity 9.83 10-22 cm/molecule) are isolated and intense for a sensitive detection. The HTO detection limit with the present set-up is 3 kBq (10 min), equivalent to 1.8 1012 molecules in the 111 cm3 CRDS cell. This detection limit could improve by a factor 3 (at least) by reducing the detection noise

Fissile mass quantification in radioactive waste packages using photofission delayed gamma rays

International audienceThis paper reports a feasibility study, performed by numerical simulation with MCNPX, of fissile mass characterization in dense, large volume, long-lived and medium activity radioactive waste packages, using photofission delayed gamma rays. High-energy photon interrogation with a 15 MeV LINAC has been modelled for a 1.18 m3 cemented waste package, coupled to high resolution spectroscopy with a HP Ge detector. The study was carried out by assessing the passive and active backgrounds respectively due to the waste package gamma emission, and to material activation during irradiation, in view to determine the detection limits for the main delayed gamma rays of interest. The obtained detection limits are lower than the expected uranium mass in the waste package. On the other hand, as the photofission signal results from both fissile 235U and fertile 238U isotopes, a method for uranium isotopes discrimination based on gamma-ray ratios has been evaluated, showing that photofission delayed gamma rays could be used to assess the fissile mass as well as the total uranium mass

A Photofission Delayed γ-ray Spectra Calculation Tool for the Conception of a Nuclear Material Characterization Facility

The photon interrogation analysis is a nondestructive technique allowing to identify and quantify fissile materials in nuclear waste packages. This paper details an automatic procedure which has been developed to simulate the delayed γ-ray spectra for several actinide photofissions. This calculation tool will be helpful for the fine conception (collimation, shielding, noise background optimizations, etc.) and for the on-line analysis of such a facility

A Photofission Delayed γ\gamma-ray Spectra Calculation Tool for the Conception of a Nuclear Material Characterization Facility

International audienceThe photonic interrogation analysis is a nondestructive technique allowing to identify and quantify nuclear fissile materials in nuclear waste packages. This paper details an automatic procedure which has been developed to simulate the delayed $\gamma$-ray spectra for several actinide photofissions. This calculation tool will be helpful for the fine conception (collimation, shielding, noise background optimizations, etc.) and for the on-line analysis of such a facility

A Photofission Delayed γ-ray Spectra Calculation Tool for the Conception of a Nuclear Material Characterization Facility

The photon interrogation analysis is a nondestructive technique allowing to identify and quantify fissile materials in nuclear waste packages. This paper details an automatic procedure which has been developed to simulate the delayed γ-ray spectra for several actinide photofissions. This calculation tool will be helpful for the fine conception (collimation, shielding, noise background optimizations, etc.) and for the on-line analysis of such a facility

Metrology for decommissioning nuclear facilities: partial outcomes of joint research project within the European Metrology Research Program

Decommissioning of nuclear facilities incurs high costs regarding the accurate characterisation and correct disposal of the decommissioned materials. Therefore, there is a need for the implementation of new and traceable measurement technologies to select the appropriate release or disposal route of radioactive wastes. This paper addresses some of the innovative outcomes of the project “Metrology for Decommissioning Nuclear Facilities” related to mapping of contamination inside nuclear facilities, waste clearance measurement, Raman distributed temperature sensing for long term repository integrity monitoring and validation of radiochemical procedures.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard