seminar

Dr. Peter Yarsky, Senior Reactor System Engineer, will give a talk at the Nuclear Engineering Program, 3:30-5:00 pm, Oct 23, 2019.

October 23, 2019

Dr Yarsky will give a talk entitled Consequences of Anticipated Transients without SCRAM with Instability in Boiling Water Reactors with Expanded Operating Domains, October 23rd, 3:30-5:00 pm, 440 Goodwin Hall. See below the Abstract and Dr. Yarsky's bio. (Host: Dr. Juliana Duarte)

Abstract
Recently, boiling water reactor licensees have sought licensing permission from the Nuclear Regulatory Commission (NRC) to expand their operating domains to the so called Maximum Extended Load Line Limit Analysis Plus (MELLLA+) domain. This domain confers some benefits in terms of operational flexibility through a flow control window at high reactor power. However, certain postulated scenarios initiated from conditions of high power coincident with low flow rate can lead to reactor instability. Instability arises due to a confluence of interacting feedback mechanisms, such as void reactivity, density wave propagation, and heat transfer. Under certain conditions, such as natural circulation, the reactor may develop large amplitude, unstable power and flow oscillations. The NRC Office of Nuclear Regulatory Research has been conducting confirmatory analysis using state-of-the-art systems analysis tools such as TRACE to simulate certain anticipated transients without SCRAM (ATWS) scenarios where unstable conditions develop. In particular, these analyses were performed for a hypothetical MELLLA+ BWR to develop a better understanding of potential fuel damage mechanisms and consequences. As a result of these studies the NRC staff has identified a possible mechanism that can result in fuel damage. The NRC conducted full-scale testing on an electrically-heated, simulated BWR fuel assembly undergoing large amplitude power and flow oscillations to study this fuel heat-up mechanism, and, through this testing campaign, was able to confirm the predicted heat-up mechanism. An area of future work is to use these experimental data to improve TRACE predictions of consequences under unstable conditions and, thereby, enhance of value of the NRC analytical tools in the area of confirmatory analysis.

Bio
Dr. Peter Yarsky is a senior reactor systems engineer in the Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research. His current research interests include coupled thermal-hydraulic, neutronic, and fuel thermal-mechanical analysis and complex transient simulation methods. Prior to this appointment, Dr. Yarsky worked in the NRC Nuclear Performance and Code Review Branch for four years with a focus on boiling water reactor safety analysis methods. Dr. Yarsky holds a Ph.D. in Nuclear Engineering from the Massachusetts Institute of Technology (MIT) with research on gas-cooled fast reactor physics; a S.M. in Nuclear Engineering also from MIT with research on nuclear power for space applications; and a B.S. in Nuclear Engineering and Engineering Physics with a minor in Economics from Rensselaer Polytechnic Institute