Radiation Damage in Nanoporous Nuclear Materials

Lead Research Organisation: University of Surrey
Department Name: ATI Electronics

Abstract

Materials in nuclear reactors are bombarded by neutrons. This can result in atoms being knocked off their lattice sites creating crystalline defects and in transmutation events which can create helium atoms. These processes can cause the physical properties of the material to deteriorate. In order to run a nuclear reactor safely it is vital to have materials which can perform under these extreme conditions. Furthermore, it is important to understand the physics behind the response of materials to radiation in order to predict how they will behave in-service and to develop new technologies.

One way to control the defects and helium which are created by neutron irradiation is to engineer a material with features which are designed to safely store them. The perfect such feature is a surface because it can never become saturated. Nanoporous materials have a structure like a nanoscale sponge and so have very high surface-area-to-volume ratios. Recently, nanoporous materials have been shown to have very good radiation tolerance and so have been proposed as candidates for use in nuclear applications. However, research so far has been limited to materials which are not suitable for use in nuclear reactors.

This research project will investigate nanoporous iron, nickel, zirconium, molybdenum, tungsten, silicon carbide and zirconium carbide. These materials all have properties which means they can be used in nuclear reactors. In order to explore the effects of irradiation, the Microscope and Ion Accelerator for Materials Investigations (MIAMI) facility at the University of Huddersfield will be used. The MIAMI facility incorporates a transmission electron microscope which allows materials to be observed on the nanoscale and an ion accelerator so the sample can be irradiated at the same time. The experiments will be combined with computer simulations to help explain the results in terms of the fundamental underlying atomistics.

The knowledge and understanding acquired from the experiments and the computer modelling will then allow nanoporous materials to be designed which are ideally suited for use in nuclear applications.

Publications

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Description A new mechanism for why nanoporous materials have enhanced stability to radiation damage has been identified. It has been noted that cascade can be "de-focused" when they interact with a void. What starts as a dense cascade becomes spread across the surface of a void which has the effect of lowering the density of the cascade of moving particles initiated by a primary knock on. The lower density cascade does not produce the same number of surviving defects as the higher density cascade and so the material can with stand a higher degree of irradiation We are still waiting for the very delayed experimental part of the program to verify our initial findings. The much delayed start of the experimental side of this project has caused substantial delays in being able to move forward on the modelling and simulation side.
Exploitation Route Presentations in papers and conferences have been made or are in progress. We are working with our collaborators in the experimental part of the project to find ways of demonstrating experimentally what has been observed computationally. We are also working with a group in Belgium to take the simulations to longer timescales so that better comparison with experiemnt might be made.
Sectors Energy