Abstract-The Finite-Difference Time-Domain (FDTD) method in cylindrical coordinates is used to describe electromagnetic wave propagation in a cold magnetized plasma. This enables us to study curvature effects in toroidal plasma. We derive the discrete dispersion relation of this FDTD scheme and compare it with the exact solution. The accuracy analysis of the proposed method is presented. We also provide a stability proof for nonmagnetized uniform plasma, in which case the stability condition is the vacuum Courant condition. For magnetized cold plasma we investigate the stability condition numerically using the von Neumann method. We present some numerical examples which reproduce the dispersion relation, wave field structure and steady state condition for typical plasma modes.

79Se is a critical radionuclide concerning the safety of deep geological disposal of certain radioactive wastes in clay-rich formations. To study the fate of selenium oxyanions in clayey rocks in the presence of a selenium reducing microbial community, in situ tests were performed in the Opalinus Clay at the Mont Terri Rock Laboratory (Switzerland). Furthermore, biotic and abiotic batch tests were performed to assess Se(VI) and Se(IV) reactivity in the presence of Opalinus Clay and/or stainless steel, in order to support the interpretation of the in situ tests. Geochemical modeling was applied to simulate Se(VI) reduction, Se(IV) sorption and solubility, and diffusion processes. This study shows that microbial activity is required to transform Se(VI) into more reduced and sorbing Se species in the Opalinus Clay, while in abiotic conditions, Se(VI) remains unreactive. On the other hand, Se(IV) can be reduced by microorganisms but can also sorb in the presence of clay without microorganisms. In situ microbial reduction of Se oxyanions can occur with electron donors provided by the clay itself. If microorganisms would be active in the clay surrounding a disposal facility, microbial reduction of leached Se could thus contribute to the overall retention of Se in clayey host rocks.

To explore the behavior of electromagnetic waves in cold magnetized plasma, a three-dimensional cylindrical hybrid finite-difference time-domain (FDTD) model is developed. The full discrete dispersion relation is derived and compared to the exact solutions. We establish an analytical proof of stability in the case of nonmagnetized plasma. We demonstrate that in the case of nonmagnetized cold plasma the maximum stable Courant number of the hybrid method coincides with the vacuum Courant condition. In the case of magnetized plasma the stability of the applied numerical scheme is investigated by numerical simulation. In order to determine the utility of the applied difference scheme we complete the analysis of the numerical method demonstrating the limit of the reliability of the numerical results.

In order to fulfil its mission, the Belgian Regulatory Body (constituted in Belgium by FANC and Bel V) has set up its own Research & Development programme, independent from the Waste Management Organisation's one. The Regulatory Body's Research & Development programme is mostly intended to investigate safety issues with the objective to be able to assess if the safety concept developed by the Waste Management Organisation fulfils the defined safety requirements. It includes the development and the follow-up of in situ experiments in Underground Research Laboratories (e.g. in the Mont Terri project in Switzerland and at Tournemire in France). Such activities are essential to maintain and improve the scientific and technical skills, to strengthen the independence from the Waste Management Organisation and to build public confidence in the regulatory function. More generally, Research & Development in Underground Research Laboratories is important to the Regulatory Body as it allows investigating processes, technologies and activities important to safety under in situ conditions. In particular, it is essential to accurately identify and characterise the processes upon which the safety functions of a disposal system rely, as well as processes which may affect the system performance. It is also necessary to demonstrate that construction and operational methods and technologies are technically feasible and can be implemented as assumed in the safety case. Such Research & Development activities are of great importance to properly manage some of the key uncertainties associated with a disposal programme and in particular to identify, characterize and reduce them where needed.