Abstract
Background of the work is the loss of coolant accident (LOCA) with release of the insulation material in a nuclear power plant (NNP). The material can be transported into the reactor containment, the building sump of the containment and into the associated systems. To secure the heat dissipation from the reactor core and the containment the cooling systems transports the water from the sump to the condensation chamber and then into the reactor pressure vessel. The function of the pumps can be affected by a high allocation of the strainers with fractionated insulation material and the heat dissipation is not guaranteed. A prediction of the routes of transport of the material is necessary to get information on the quantity of the insulation material is settled down and not transported to the strainers. To simulate the transport of the material validated CFD models have to be developed. A joint research project to investigate the problem more in detail, particularly with the aim of CFD model development, is being performed in cooperation of the Institute of Process Technology, Process Automation and Measuring Technology (IPM) of the University in Zittau/Gorlitz with the Research Center Dresden (FZD) [1]. The main aim is the calculation of the mass of insulation material transported to the strainers. This information is the essential to affect the differential pressure on the strainers after a LOCA. The paper deals with the experimental and methodical work for the description of the transport of fragmented insulation material in a small channel. The work is divided into two steps. In the first step, the water flow was investigated on the test facility "Ring Channel" at the IPM. For this, different measurement techniques, such as ultrasonic sound for the mean velocity and an impeller sensor for the velocity in the middle of the channel (maximum velocity) as well as Particle Image Velocimetry (PIV) were used. The results were compared to theoretical calculation of the mean and maximum velocities in small channels found in the literature. Based on the geometry of the test facility, CFD-calculations of the water flow with the main focus on the turbulence model were performed. The simulation results were compared to the measured values of the experimental values. The second step was the investigation of the transport of insulation material in this channel. For this, a defined amount of material was inserted in the water flow at different water velocities. The transport of the material was captured by digital cameras followed up by the analysis using digital image processing. Algorithms for the analysis of the single particles and the particle collective behavior were developed. One of the results is a particle size distribution. Based on this the definition of the disperse phase in the CFD-Simulation is set and CFD-Simulations were performed. For the validation the volume fraction of the dispersed phase of the CFDSimulation in defined virtual planes and the particle collective behavior from the experiments were compared.
