Investigation of advanced gaseous effluent treatment methods for severe accident consequence management

Abstract

After Fukushima accident, containment filtered venting systems (CFVS) are being considered as an effective way to protect the integrity of containment against over pressurization. Currently the price of CFVS is relatively high. Even if CFVS is implemented, if an accident involves radioactivity release through containment bypass scenario, a separate system is needed to deal with such release. And for NPPs without CFVS, there is a need for a system to effectively capture the released radioactive materials under severe accident. In all of the cases, a need for a system to treat the captured source term exists. As such, research and development into an alternative effluent treatment system with versatility of design and reasonable cost is necessary. A conceptual design of a new gaseous effluent treatment system is proposed in this research. The system uses cyclone separators with novel absorbent materials integrated with a commercialized Cesium Removal System (CRS). An initial evaluation of the efficiency of the system was made with an assumption that the aerosols and gases, after separation, can be separately absorbed/treated to meet regulations. Thus the entire system efficiency relies on the performance of cyclone separator. For the analysis of cyclone performance, a Reynolds average Navier-Stokes (RANS) k-$\varepsilon$ model was used as the turbulent model in a computational fluid dynamics (CFD) approach. Using the open source Field Operation And Manipulation (OpenFOAM) software as a simulation tool, the flow field inside the cyclone was analyzed and the efficiency of the cyclone was calculatedevaluated. Also, a theoretical calculation of novel absorbent’s mass was conducted. Results showed that this gaseous effluent treatment system can separate and treat the gaseous and aerosol parts. Further analyses, based on the result obtained, were performed to increase the cyclone separation efficiency, thus to enhance the whole system performance. The presented conceptual design could serve as an alternative or complementary technology for effluent treatment, in an emergency, prior to atmospheric discharge, and can be the basis for system cost evaluation.