Woodruff School of Mechanical Engineering

NRE 8011/8012 and MP 6011/6012 Seminar

Nuclear & Radiological Engineering and Medical Physics Programs


ESBWR Thermal-Hydraulic Stability and TRACG Methodology


Dr. Jun J Yang


GE Hitachi Nuclear Energy Global Nuclear Fuel - Americas


Thursday, March 10, 2011 at 11:00:00 AM


Boggs Building, Room 3-47 (3rd floor)


Bojan Petrovic


Under certain conditions, Boiling Water Reactors (BWRs) may be susceptible to coupled neutronic/thermal-hydraulic instabilities. These instabilities are characterized by periodic power and flow oscillations and are the result of density waves (i.e., regions of highly voided coolant periodically sweeping through the core). If the flow and power oscillations become large enough, and the density waves contain a sufficiently high void fraction, the fuel cladding integrity safety limit could be challenged. In the Economic Simplified Boiling Water Reactor (ESBWR), the highest power to flow ratio (and hence the smallest stability margin) is encountered at rated operation. Thus, it is essential that the ESBWR operate with substantial margin to instability at rated power. This requirement is met by imposing very conservative design criteria on the decay ratio. Detect and Suppress solutions will also be implemented, but only to serve as a backup in the very unlikely event that oscillations are encountered. The TRACG computer code is used for the analysis of ESBWR stability margins. TRACG is a General Electric (GE) proprietary version of the Transient Reactor Analysis Code (TRAC). TRACG uses advanced one-dimensional and three-dimensional methods to model the phenomena that are important in evaluating the operation of BWRs. TRACG has been approved by the NRC for ESBWR LOCA (ECCS and containment), AOO/ATWS and Stability analysis. This seminar will discuss the ESBWR specific stability phenomena and the overall methodology of TRACG application for ESBWR stability analysis including the code qualification.


Dr. Yang is currently a member of Nuclear Analysis COE team at the GE Hitachi Nuclear Energy facility in Wilmington, NC. He received his M.S. (2002) and Ph.D. (2005) in Mechanical and Nuclear Engineering from Penn State University. Over the past five years at GE he has held lead engineering positions in both the ESBWR safety and system integration group and the Nuclear Safety analysis group.