Melt dispersion and direct containment heating (DCH) experiments in the DISCO-H test facility
- Authors
- Publication Date
- Jan 01, 2004
- Source
- OpenGrey Repository
- Keywords
- Language
- English
- License
- Unknown
Abstract
The DISCO-H Test Facility at Forschungszentrum Karlsruhe was set up to perform scaled experiments that simulate melt ejection scenarios under low system pressure in Severe Accidents in Pressurized Water Reactors (PWR). These experiments are designed to investigate the fluid-dynamic, thermal and chemical processes during melt ejection out of a breach in the lower head of a PWR pressure vessel at pressures below 2 MPa with an iron-alumina melt and steam. In the past, a detailed study of pressure and geometry effects on the fluid dynamics of the melt dispersion process had been performed with cold model fluids in the facility DISCO-C. The main components of the facility are scaled about 1:18 linearly to a large European pressurized water reactor. Standard test results are: pressure and temperature history in the RPV, the cavity, the reactor compartment and the containment, post test melt fractions in all locations with size distribution of the debris, video film in reactor compartment and containment (timing of melt flow and hydrogen burning), and pre-and post test gas analysis in the cavity and the containment. The results of six experiments are presented here. All experiments were done with 10.6 kg of iron-alumina melt (scaling to 16 m"3 corium), and a hole of 56 mm diameter (1 m scaled) or 28 mm at the center of the lower head. For comparison with a similar experiment conducted in a larger scale (1:10), the basis experiment was performed with an open path from the reactor pit to the containment (open pit), with prototypical conditions concerning the steam driven ejection out of the RPV, and a containment atmosphere, that was part air and part steam at an elevated pressure, with 3 mole-% hydrogen. In this and other tests, hydrogen production and combustion occurred. In one experiment the hydrogen effect was excluded by using only nitrogen as driving gas and a pure air atmosphere in the containment. In some tests the direct path to the containment was closed (closed pit). The pressure rise in the containment is highest with an open pit and hydrogen combustion. With a closed pit the gas and the debris have to flow first into the subcompartment and then through relatively small cross sections into the containment. Considerable less hydrogen was produced and burned in this case. In the test without steam, no hydrogen effect was present, but, with the direct path to the containment open, a large amount of debris was dispersed into the containment, and efficiently transferred heat to its atmosphere. (orig.) / Available from TIB Hannover: ZA 5141(6988) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische Informationsbibliothek / SIGLE / DE / Germany
