ORNL Small-Break LOCA Heat Transfer Test Series I: Rod Bundle Heat Transfer Analysis

摘要

Under sponsorship of the U.S. Nuclear Regulatory Commission, Oak Ridge National Laboratory (ORNL) has experimentally investigated heat transfer and reflood under conditions similar to those expected in small-break loss-of-coolant accidents (SBLOCAs). Presented are results and analysis of the first of two series of uncovered bundle heat transfer tests. Specifically, a high-pressure high-temperature data base of experimental heat transfer coefficients and local fluid conditions has been compiled. In addition, a heat transfer model that accounts for forced convection and thermal radiation to steam has been developed to predict heat transfer coefficients under conditions typical of the subject tests. Experimental testing was performed at ORNL in the Thermal Hydraulic Test Facility (THTF), which is a large, high-pressure, electrically heated test loop configured to produce conditions similar to those expected in an SBLOCA. Design features of the THTF include a 64-rod bundle with an axially and radially uniform power profile. Bundle dimensions are typical of a 17 x 17 fuel assembly in a pressurized-water reactor. Experimental testing was performed in a steady-state mode with the inlet flow equal to the steaming rate. Generally about 20% to 30% of the heated bundle was uncovered, and data were taken during periods of time when the two-phase mixture level was stationary.