Recent fuel-coolant interaction experiments conducted in the FITS [Fully Instrumented Test Site] vessel

The US Nuclear Regulatory Commission has been sponsoring research at Sandia National Laboratories to investigate the interaction of molten core materials with water. These interactions play an important role during severe core-melt accidents inside a pressurized light water reactor. They influence the rates and magnitudes of hydrogen and steam generated, the characteristics of the debris bed created in the lower plenum after melt-relocation, the transient pressurization of the primary system, and the fission product release characteristics and timimg. Furthermore, since the core is cooled with water, an understanding of the parameters that control the behavior of these fuel-coolant interactions (FCIs) is necessary to make correct accident-management decisions. In an effort to assist in the understanding of these and other FCI-related issues, as well as provide important data for model development and validation, six FCI experiments were conducted at Sandia. Results discussed include the transient gas-phase pressures, the rate and magnitude of hydrogen generation and the post-test debris characteristics