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Molecular Dynamics Simulation of Uranium Dioxide Fuel

Uranium dioxide (UO2 ) , as a common nuclear fissile fuel, is of great research interest due to its significant role in nuclear reactor. Nuclear fuel s are known to be exposed at a environment with high temperature, high pressure, and intens e radiation s , which might severely degrade UO 2 and eventually lead to the failure of reactor especially when we consider generation IV reactors running at higher temperature and burnup for the sake of energy saving and nuclear non-proliferation . Therefore, it is critical to thoroughly understand the properties of UO2 under various environmental conditions to evaluat e the potential failure mechanism . Experimentally, owing to the complications of reactor environment, it is difficult, maybe impossible, to evaluate the contribution from one specific factor or the combination of several chosen ones to the overall properties of UO2 . In this regard, molecular dynamics (MD) is an effective and preferable simulation tool because it is relatively easy to control any factors involved. Moreover, MD can deliver detailed structural evolution of UO2 at the scale of nanometer and picoseconds/nanoseconds.

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Neutron, X-ray, and Light Scattering Studies of Soft Matter

“Soft matter” refers to materials consisting of a variety of physical states which can easily de-formed by thermal stresses or thermal fluctuations, such as colloidal solutions, liquids, polymers, micelles, clay platelets, manmade nanoparticles, and a number of biological materials. Different from simple liquids, complex soft matter systems like colloidal solutions contain a suspension of nano-particles and solvent molecules with many orders of magnitude difference in size. The large spatial dissymmetry of colloid solutions has made it difficult for typical experimental techniques to be sensitive to particles other than the colloids. Scattering technique, such as neutron, X-ray, and light scattering, is one of the essential means to study the structure and associated dynamic processes of various soft matter systems.

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Monte Carlo Simulation in Nuclear Threat Detection

Nuclear threats are real and must be taken seriously. However, it is extremely difficult to detect nuclear materials that are shielded and typically hidden without generating false positive or false negative signals. A typical nuclear detection system consists of several components: radiation sources, objects to be detected, detectors, and imaging systems. Current research efforts focus on individual components but an integrated systemic model is lacking. We plan to develop a fully coupled multi-physics computational model of the nuclear detection system for nuclear threat detection, using existing nuclear data bases and building on existing experimental collaborations.

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Dynamics of Supercooled Water Confined in Nanoporous Materials

The understanding of the structure and dynamics of water confined in restricted geometries is important for many applications, such as the explanation of water-related phenomena in living cells, the active sites of proteins and membranes, catalysis, etc. We are currently working on the dynamics of supercooled water in nanoporous matrices, MCM-41-S, and Protein Lysozyme. The general properties we observed are now promising to be found in any hydrated proteins and DNAs. We will be testing out this hypothesis and hopefully to unclose the real relations between the hydration (or surface) water and the proteins (DNAs, as well).

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