Suchergebnisse

The assessment of hydrogen release, distribution, and mitigation measures in the containment of a nuclear power plant is increasingly based on code calculations. These calculations require state-of-the-art experiments to benchmark the codes against them. Two of these experiments are presented in this paper. These experiments were conducted in the PANDA facility (Switzerland) in the framework of the OECD/NEA HYMERES project. The experiments consider natural circulation flow in a two-room type containment where flow loops can form between the inner and the outer zones. During normal operation these zones are separated and in the case of an accident they become either connected by the opening of rupture disks, convective foils, and dampers or connected by bursting of doors and opening of other connections between compartments. For the experiments considered here one lower PANDA-vessel represents the steam generator (SG) tower and the inaccessible area whereas the other vessel represents the outer room area. The lower vessels are isolated from one another except for a small aperture that represents the damper. The two upper vessels—representing the containment dome—are connected to the lower vessels through tubes. The scenario consisted of four phases. In phase 1, a high steam mass flow rate was injected in the vessel representing the SG tower. After the relaxation phase 2, helium (representing hydrogen) was injected in the same vessel (phase 3). Finally in phase 4 no active interventions were done until the end of the test. Two tests were conducted to evaluate the developing helium transport by the natural circulation flow: one with and one without damper (by closing the aperture). The results showed that a two-room containment (TRC) mixing scenario can be well represented with the PANDA facility. It is found that, with the mixing damper open, a global natural circulation loop develops over all four vessels, whereas with closed damper the natural circulation loop is established only between the three vessels representing the inner zone and the upper dome. It is shown that the presence of the damper has a strong effect on the resulting helium content in the inner zone with 3 times less helium at the end of the test compared with the configuration without damper. The formation of a stable helium stratification in the upper vessels was observed in the presence of the open damper.

The NURESIM Project of the 6th European Framework Program initiated the development of a new‐generation common European Standard Software Platform for nuclear reactor simulation. The thermal‐hydraulic subproject aims at improving the understanding and the predictive capabilities of the simulation tools for key two‐phase flow thermal‐hydraulic processes such as the critical heat flux (CHF). As part of a multi‐scale analysis of reactor thermal‐hydraulics, a two‐phase CFD tool is developed to allow zooming on local processes. Current industrial methods for CHF mainly use the sub‐channel analysis and empirical CHF correlations based on large scale experiments having the real geometry of a reactor assembly. Two‐phase CFD is used here for understanding some boiling flow processes, for helping new fuel assembly design, and for developing better CHF predictions in both PWR and BWR. This paper presents a review of experimental data which can be used for validation of the two‐phase CFD application to CHF investigations. The phenomenology of DNB and Dry‐Out are detailed identifying all basic flow processes which require a specific modeling in CFD tool. The resulting modeling program of work is given and the current state‐of‐the‐art of the modeling within the NURESIM project is presented.

International audience ; In case of a severe accident in a light water nuclear reactor, hydrogen would be produced duringreactor core degradation and released into the reactor building. The stratification of the released hydrogen in the reactor containment could lead to local pockets of gas mixtures of high hydrogen concentration and, in case ofcombustion, to high pressure loads which might challenge the containment structural integrity.The objectives of ERCOSAM and SAMARA projects, co-funded by the European Union and the Russia, are to investigate hydrogen concentration build-up and break-up due to safety components operations, as sprays, coolers and Passive Auto-catalytic Recombiners (PARs).For this purpose, various experiments addressing accident scenarios scaled down from existing plant calculations to different thermal-hydraulics facilities (TOSQAN, MISTRA, PANDA, SPOT) are considered. This paper describes the work performed in framework of the workpackage WP1 of the ERCOSAM project and presents theadopted methodology to scale down the real plant calculations results, provided by the projects partners, to the experimental facilities.

International audience ; In case of a severe accident in a light water nuclear reactor, hydrogen would be produced duringreactor core degradation and released into the reactor building. The stratification of the released hydrogen in the reactor containment could lead to local pockets of gas mixtures of high hydrogen concentration and, in case ofcombustion, to high pressure loads which might challenge the containment structural integrity.The objectives of ERCOSAM and SAMARA projects, co-funded by the European Union and the Russia, are to investigate hydrogen concentration build-up and break-up due to safety components operations, as sprays, coolers and Passive Auto-catalytic Recombiners (PARs).For this purpose, various experiments addressing accident scenarios scaled down from existing plant calculations to different thermal-hydraulics facilities (TOSQAN, MISTRA, PANDA, SPOT) are considered. This paper describes the work performed in framework of the workpackage WP1 of the ERCOSAM project and presents theadopted methodology to scale down the real plant calculations results, provided by the projects partners, to the experimental facilities.

International audience ; In case of a severe accident in a light water nuclear reactor, hydrogen would be produced duringreactor core degradation and released into the reactor building. The stratification of the released hydrogen in the reactor containment could lead to local pockets of gas mixtures of high hydrogen concentration and, in case ofcombustion, to high pressure loads which might challenge the containment structural integrity.The objectives of ERCOSAM and SAMARA projects, co-funded by the European Union and the Russia, are to investigate hydrogen concentration build-up and break-up due to safety components operations, as sprays, coolers and Passive Auto-catalytic Recombiners (PARs).For this purpose, various experiments addressing accident scenarios scaled down from existing plant calculations to different thermal-hydraulics facilities (TOSQAN, MISTRA, PANDA, SPOT) are considered. This paper describes the work performed in framework of the workpackage WP1 of the ERCOSAM project and presents theadopted methodology to scale down the real plant calculations results, provided by the projects partners, to the experimental facilities.