Fluid Dynamics and Scrubbing Behavior of Radionuclides in a Venturi Scrubber

Abstract

In instances of severe accident in a nuclear reactor, the reactor containment gets pressurized and this may lead to release of hazardous radionuclides to the environment. To prevent this, containment filtered venting system (CFVS) have been envisaged in advanced reactors. One of the efficient designs in this regards is a manifold of venturi scrubber submerged in alkaline liquid and housed in a scrubber tank. A concept design of FCVS has been made using empirical models available in literature. The sizing is based on pressure and flow conditions from the containment and radioactive inventory to be scrubbed for reactor conditions. The manifold is calculated to have 30 number of venturi scrubbers submerged in alkaline pool. An experimental setup comprising of single venturi scrubber is fabricated and detailed instrumentation is provided. The flow scaling ratio is kept as 1:30. The effect of various parameters namely, gas flow rate, upstream pressure conditions, and the submergence depth is studied on hydrodynamics and the scrubbing behavior of iodine. A new CFD model having an Eulerian-Lagrangian framework is implemented for the current analysis. This model accounts for the drag forces and inertial effect of entrained jet on the continuous gas phase. The model predicts the size, velocity, and distribution of the droplets based on its interaction with the high speed gas. The retention of iodine is calculated from the gas droplet mass transfer coefficient given by Steinberg and Treybal correlation. The model is found to predict the experimental findings accurately and hence it was further employed to assess the performance of venturi scrubber under flow conditions expected in FCVS during accidental situations. The numerical model predicted that the proposed design is adequate for advanced Indian nuclear reactor.