Numerical Simulation of Bubble Dynamics in the Presence of Boron in the Liquid

Abstract

Abstract Deposition of boron on the fuel rod cladding during boiling of water containing boron can depress the neutron flux and lead to a decrease in nuclear reactor power output. There is practically little precise information on the temperature field, the gradients of chemical concentration and deposition of boron on the cladding surface. The objective of the present work is to simulate the nucleate boiling process along with velocity, temperature and concentration fields of aqueous boron in the vicinity of the cladding of a fuel rod. As a first step in solving the complete problem, two-dimensional numerical simulation of a bubble growth on a horizontal surface is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy and species concentration. The calculation domain is divided into macro and micro regions. In macro-region, the governing equations are used to calculate the distributions of velocity, temperature, and concentration. The Level Set method is used to capture the evolving liquid-vapor interface. For micro-region, lubrication theory is used, which includes the disjoining pressure in the thin liquid film. The solutions for micro-region and macro-region are matched at the outer edge of the micro-layer. A dilute aqueous Boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 0.003.