Simulation of flow conditions in nuclear power plant reactor pressure vessel lower plenum experimental facilityKamenik, Blaž (Avtor) Marn, Jure (Mentor) Kljenak, Ivo (Komentor) nuclear power plantsevere accidentreactor core meltlower plenumheat flux focusing effectThe flow conditions during the experiment LIVE2D on reactor core melt behaviour in the lower plenum of a reactor pressure vessel, performed at the Karlsruhe Institute of Technology (Germany), were simulated with a Computational Fluid Dynamics computer code. In this hypothetical severe accident scenario in a pressurized water reactor nuclear power plant, the melt is divided into an oxidic layer and a metallic layer on top of it, and the oxidic layer is volumetrically heated due to decay heat. In the experiment, oil and salt were used as simulant materials for metallic and oxidic melt, respectively. The main goal of performed simulations was to investigate the so-called “focusing effect”, where a thin layer of the reactor vessel steel wall is exposed to high heat flux. Due to the length of experiment, which exceeds 100 hours, only intervals of the melt behaviour were simulated. Four cases were simulated. The first case investigated different boundary conditions for the oil layer behaviour for layer thickness 35 mm. The second case investigated the same conditions with added modelling of the reactor vessel steel wall and salt crust from the lower layer. The third case used similar modelling as the second case to investigate the oil layer behaviour for layer thickness 75 mm. The fourth case investigated both salt and oil layers for oil layer thickness 75 mm. Different analytical and numerical calculations were performed to determine heat losses from simulant liquids to the surroundings, which played an important part in the experiment.[B. Kamenik]20192019-08-23 17:48:19Magistrsko delo/naloga74340UDK: 621.318.43:621.311.25(043.3)COBISS_ID: 22761750NUK URN: URN:SI:UM:DK:V0PTRPKYsl