Abstract:

The process of lock-exchange and gravity-driven exchange flow for fluids of differing densities is of particular interest in the Depressurized Loss of Forced Convection (D-LOFC) condition for the Very High Temperature Gas-Cooled Reactor (VHTR). This scenario postulates a large break in the horizontal primary pipe or in a vertical maintenance standpipe, which induce the gravity-driven ingress of air into the helium filled reactor vessel. Ultimately, it may lead to an oxidation of graphite components inside the reactor vessel. Before performing a scaled experiment using helium and air, a scoping test using water-brine as simulant fluids is performed to assure that the pertinent phenomena can be accounted for correctly. The geometric effects of both the break orientation and the break length are investigated in a scaled test apparatus, which consists of two rectangular compartments connected via break pipes. The volumetric exchange rate is obtained by measuring the time rate of change of mixture density using a hydrometer. Both the geometric configurations of the break and the formation of the mixture interface inside the mixing compartments are found to be the major parameters in determining the exchange rate. In general, the present results show similar characteristic phenomena as those found in previous studies for the initial stage of ingress. As the ingress progresses, however, it is found that the mixing phenomena inside the compartment and the compartment geometry make significant impacts on the ingress rate. Unlike the previous studies, the present results show that the average exchange rate for the entire ingress event can be up to 70% lower than that obtained from the initial stage alone.

Brief Education and Career History:

2007-Present:    Assistant Professor, Department of MNE, The Pennsylvania State University
2003-2007:        Assistant Professor, Nuclear Engineering, University of Missouri-Rolla
2002-2003:        Visiting Assistant Professor, Nuclear Engineering, Purdue University
1999-2002:        Post Doctoral Research Associate, Nuclear Engineering, Purdue University
1994-1999:        Ph.D., Nuclear Engineering, Purdue University