Investigation of core degradation (COBE)

In-Vessel Core Degradation

“…Although the specific evolution might depend, to some extent, on the type of transient being analyzed, the exponential increase with temperature of the Zircaloy oxidation rate produces very sharp temperature increases in the core as soon as it exceeds 1500 K. This is a characteristic feature of any SA experiment or plant simulation. As shown in the LOFT-FP-2 experiment [20] [21], the initial core heatup rate (less than 1 K/s due to decay heat) is rapidly increased by an order of magnitude, due to additional heat released by the Zircaloy oxidation. As a result, temperatures of the fuel rods and intact core structures increase rapidly above the melting point of Zircaloy (2100 K).…”

“…Although this is still an area of active research, a large number of reflooding experimental data, as well as data from TMI-2, has demonstrated these characteristic trends. In detail (the capital letters below, after the name of the experiments, refer to the Figure 2 Hungarian CODEX (X) tests [17] are performed in 3 Â 3 bundles; the rather recent Russian PARAMETER (P) tests in Podolsk [18], dedicated to top and bottom flooding, refer to 19 rods in VVER bundles; the reflooding experiments CORA (C) [19] and QUENCH (Q) [11] address bundle sizes between 21 and 31 rods; and the central fuel element in LOFT-LP-FP2 (L) [20] [21] amounts to 121 rods. Most of the experiments address PWR (P) conditions; there are only one BWR (B) and five VVER (V) reflooding experiments, one CODEX one QUENCH and three PARAMETR tests.…”

“…In particular, the relocation observed in TMI-2 showed a radial progression of the melt (molten pool), followed by an axial progression through the bypass, down to the lower plenum. Such relocation processes were studied in the frame of the EC project COBE [20], with an emphasis on the use of relevant material properties (density, viscosity) and advanced multidimensional flow models to predict melt relocation and progression.…”

Recombinación del hidrógeno en dispositivos autocatalíticos pasivos y sus implicaciones en la seguridad de las centrales nucleares

“…La generación de hidrógeno en estas condiciones no responde a las correlaciones de la generación metal-vapor conocidas, por lo que se ha insistido en la necesidad de realizar nuevos experimentos . Por ejemplo, la instalación QUENCH (Hofmann, 2000) en el FzK dentro del proyecto COBE (Sheperd, 1999) del IV Programa Marco de la UE.…”