A heat transfer and flow visualization experiment was conducted with a one-fifth scale model simulating a dry shielded canister (DSC) with 24 PWR spent fuel assemblies in order to elucidate the heat transfer characteristics and the velocity distribution for natural convection inside a DSC filled with air or water at atmospheric pressure. It was found that the average heat transfer coefficients were proportional to the onefourth power of the Rayleigh number despite the complicated geometry inside the DSC. Flow patterns inside the DSC were visualized clearly through a digital image processing system. The velocity distributions inside the DSC were obtained quantitatively from the Particle Tracking Velocimetry. In comparison with the results of a two-dimentional thermal hydraulic analysis, computed flow patterns were similar to the experimental results and the computational temperature distributions on the sleeve surfaces agreed well with the experiments within S%, except at the top point of the center gap. It was also found that the difference in the heat transfer coefficient was within 25% for air as the working fluid, while a satisfactory agreement was not obtained when water was the working fluid.
The aerosol deposition test series is being performed to investigate the deposition of FP vapor and aerosol onto the inner surface of reactor coolant piping during a severe accident of a light water reactor. Vapor and aerosol of Csl as an FP simulant was introduced into the horizontal test section pipes. No substantial decomposition of Csl was identified to occur both in the high temperature inert and superheated steam environments. The comparison between the results of the aerosol deposition test series and the thermofluiddynamic analysis with WINDFLO\Y implied that a profile of the Csl deposition due to vapor condensation and thermophoretic aerosol deposition was influenced by local thermo-fluiddynamic conditions. Deposition velocities were evaluated for Csl vapor and aerosol based on the deposition characteristics of CsI and the thermo-fluiddynamic analysis.
The aerosol deposition test series is being performed to investigate the deposition of FP vapor and aerosol onto the inner surface of reactor coolant piping during a severe accident of a light water reactor. Vapor and aerosol of Csl as an FP simulant was introduced into the horizontal test section pipes. No substantial decomposition of Csl was identified to occur both in the high temperature inert and superheated steam environments. The comparison between the results of the aerosol deposition test series and the thermofluiddynamic analysis with WINDFLO\Y implied that a profile of the Csl deposition due to vapor condensation and thermophoretic aerosol deposition was influenced by local thermo-fluiddynamic conditions. Deposition velocities were evaluated for Csl vapor and aerosol based on the deposition characteristics of CsI and the thermo-fluiddynamic analysis.
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