Date: Thursday, Jan 12th
Presenter: Dr. Leland Barnard, Elysium Industries
A nuclear reactor is an extreme environment for structural materials, demanding performance in the face of damaging radiation, corrosive attack, and high temperatures through operational lifetimes that can last decades. These factors lead to material degradation and failure phenomena that are not observed in any other environment. Safe and economical use of nuclear power hinges on our ability to understand and predict material degradation, and this talk will discuss the use of atomistic modeling tools to gain key insights into the physical mechanisms of material degradation in nuclear power systems. Two particular phenomena will be discussed. The first is radiation induced segregation (RIS), which results in dramatic changes in alloy chemistry near extended crystal defects such as grain boundaries due to radiation induced defect migration. Atomistic simulations have revealed that self-interstitial defects, once thought to have only a secondary role in RIS, play a significant role in counterbalancing the effects of vacancy defects. The second phenomenon is stainless steel corrosion in high temperature, high pressure water, where TEM characterization and first principles calculations have been used to investigate the effect of S impurities on local oxidation. Both of these phenomena have significant implications for material failure through intergranular stress corrosion cracking (IGSCC), which has been perhaps the most pervasive material failure mechanism in nuclear power systems. The ability to forecast and mitigate IGSCC will remain a vitally important issue for the continued operation of our current nuclear infrastructure, and computational materials tools will play an increasingly important role in this effort.
Leland Barnard is a Principal Scientist for materials and chemistry at Elysium Industries, a nuclear reactor design firm developing safe and economical molten salt reactor technology. Dr Barnard received his PhD from the University of Wisconsin-Madison in 2013, and in the time since he has also worked at the Knolls Atomic Power Laboratory in Niskayuna, NY. Dr Barnards research has been devoted to the use of computational materials science tools to understand and predict material degradation in nuclear power systems.