Development of the VESUVIUS Code for Steam Explosion Analysis

Part 1: Molten Jet Breakup Modeling

Abstract

With steam explosions in the reactor pressure vessel now considered to pose an acceptably small risk to the safety of a nuclear light water reactor, steam explosions in the containment vessel are being given considerable attention. In these hypothesized events, molten nuclear fuel is ejected into the containment vessel as a high-temperature jet surrounded by molten particles. The jet undergoes breakup in the coolant pool and, as it mixes with coolant, explosively high evaporation rates may arise. Herein, a jet breakup model for containment vessel scenarios, with the primary breakup mechanism being the Kelvin-Helmholtz instability, is described.The one-dimensional jet breakup model solves mass and energy conservation equations for the vapor film surrounding the jet and for jet fragmentation and returns these results back to the VESUVIUS code for analysis of jet dynamics and the entire steam explosion process. In the companion Part 2 paper, comparisons of VESUVIUS calculation results against experimental data are discussed.