1. Uranium speciation in a mining-affected wetland soil 2. Measurement of isolated photons in p–Pb collisions at sNN−−−−√ = 5.02 TeV with the ALICE experiment at LHC

jeudi 29 mars 2018, 14:00 → 15:30 Europe/Paris

Amphi GALOIS (Subatech - IMT Atlantique)

Chloé Therreau

1 Uranium speciation in a mining-affected wetland soil

Uranium mining in Europe played an important role for the supply of this resource, especially in the mid of the 20th century. Mine tailing storage sites with residual Uranium minerals can present a hazard for the environment by the potential release of radionuclides to the ecosystem. The data gained by studying the contaminant behavior in this context may be used to validate existing models predicting the migration of radionuclides.
The site subject to the study contains the remnants of a Uranium mineral processing plant which has been operated in the direct vicinity of several smaller mines in the 1950s. Recent gamma-ray surveys performed by ecologists in the surrounding area showed elevated radiation levels alongside a creek exiting the drainage of the storage site. Drill cores taken in a strongly marked wetland area some two hundred meters downstream showed Uranium concentrations up to 2000 ppm in the first 30 cm.
Sequential extraction, electron-microscopy and X-ray absorption spectroscopy have been used in order to determine the nature of the Uranium contamination. The identification of particulate Uranium strongly indicates that the contamination was created in the context of a flooding event during the mining period. Further investigations aim to determine if parts of the Uranium minerals in the soil have dissolved and subsequently precipitated in a different form or have been immobilized by other solid soil components.

Orateur: Andreas Fichtner (Radiochimie)

2 Measurement of isolated photons in p–Pb collisions at sNN−−−−√ = 5.02 TeV with the ALICE experiment at LHC

Within the Standard Model, the behaviour of matter at its fundamental scale is described by Quantum Chromodynamics (QCD). This theory formalises the strong interaction that exists between quarks and gluons, generically referred to as partons, and predicts their confinement within hadrons in normal temperature and density conditions. A very energetic context may lead to free the partons from their hadronic structure, resulting in a Quark-Gluon Plasma (QGP) predicted by the QCD theory and experimentally expected in ultrarelativistic heavy-ion collisions such as those provided by the lead-lead (Pb–Pb) system. The ALICE experiment (A Large Ion Collider Experiment) located at the CERN Large Hadron Collider (LHC) can observe such collisions as well as the proton-proton (pp) and proton-lead (p–Pb) systems for which the emergence of a QGP is not predicted, constituting therefore mandatory references to Pb–Pb studies.
In this presentation we are interested in direct photons produced at the earliest time of the collision in hard processes between partons, in the case of p–Pb collisions at √

Orateur: Masson Erwann (Plasma)