This PhD position involves modeling the physical and chemical properties of radionuclides in irradiated nuclear graphite from dismantled French UNGG reactors using molecular modeling techniques. The modeling will determine the chemical stability and mobility of chlorine-36 and tritium intercalated in graphite sheets, and at graphite surfaces, to inform potential decontamination treatments for the 23,000 tons of graphite waste. The PhD will use density functional theory, molecular dynamics, and Monte Carlo simulations to study the structural, electronic, vibrational and electronic properties of radionuclides in various graphite configurations and compare to experimental results from an R&D project on graphite storage alternatives.

1. PhD Position 2014
Laboratory : EDF Lab -- Department Materials and Mechanics of
Components (MMC) and Laboratory of Physics of Interfaces (LPCIM –
Ecole Polytechnique)
Co-supervisors : Philippe Baranek (EDF) and Holger Vach (LPCIM)
e-mail: philippe.baranek@edf.fr and vach@leornardo.polytechnique.fr
Molecular modeling of the physical and chemical properties of radionuclides in nuclear
graphite UNGG
Scientific project:
The graphite has a number of properties that make it a material of choice for the nuclear power industry : we know
how to produce it at the industrial scale , it has a good chemical inertness and a good temperature stability and, when
purified , it is a relatively effective neutron moderator whose low capture cross section allows the use of non- nuclear
fuel enriched fissile material. It has been widely used since the first atomic pile called "Fermi" built in 1942 in the
United States , to more recent prototypes qualified as reactors for future HTR (high temperature reactor) type, or
VHTR (very high temperature reactor) . Graphite has been used as a moderator and reflector of neutrons in nuclear
reactors French first generation: UNGG (Natural Uranium Graphite Gas). The UNGG last operating reactor Bugey 1
was finalized in 1994. The dismantling of nine French UNGG will lead to the production of 23,000 tons of irradiated
graphite which about 80 % comes from six reactors operated by EDF. The first graphite bricks from the heart of the
seeded dismantling of UNGG reactor Bugey 1, should be removed from the reactor chamber by 2022 . Graphite
during its operation in the reactor was subjected to combined effects of temperature, neutron flux and its chemical
environment. Impurities it contained were activated. The irradiated graphite nuclear waste is classified as low-level
waste activity (FA), which contains some long-lived radionuclides (VL) as the chlorine-36, tritium and carbon-14.
An R&D project financed by EDF, CEA and ANDRA has been launched since 2011 in order to evaluate various
treatment options and alternatives to graphite storage. The proposed PhD period fits into this framework. It aims to
use different methods of molecular modeling (DFT, MD, MC) of the intercalation of chlorine 36 and tritium in graphite
sheets to determine its chemical stability, mobility or on the surface of graphite sheets in view to a possible future
treatment of decontamination and to understand the influence of grain boundaries on the dynamics of radionuclides.
For each point, the structural, electronic and spectroscopic (vibrational and electronic) properties of the various
configurations of the material will be studied and compared with various experimental results obtained in this project.
The PhD will take place in the group "Chemistry and Materials for the Energy Efficiency" of the Department of
Materials and Mechanical Components (MMC) from the center of research and development of EDF Lab in Moret -
sur- Loing (77, near Fontainebleau ) , and in Laboratory of Physics of Interfaces at Ecole Polytechnique (91, Palaiseau
) .
Techniques in use : first-principles calculation (ab initio and DFT), molecular dynamic (and Monte Carlo)
Applicant skills : Structural and electronic properties of condensed matter, computer modeling and simulation.