Revaporization of a CsI Aerosol in a Horizontal Straight Pipe in a Severe Accident Condition

Aerosol revaporization in piping is being investigated in the WIND project at the Japan Atomic Energy Research Institute. The objectives of this study are to characterize the aerosol revaporization from piping surfaces under various thermal-hydraulic conditions and to obtain insights applicable to the validation of analytical models. Cesium iodide aerosol was introduced into the test section with a carrier gas. After quantifying the deposited mass of cesium and iodine, the test section was reheated to realize the revaporization. The revaporized materials were deposited onto another test section with an axial temperature gradient located downstream. Two runs (WAV1 and WAV2) were conducted. In WAV2, the influence of metaboric acid was examined. Most of the deposited cesium and iodine in the test section was revaporized and transported downstream. In WAV2, deposition density of cesium was much larger than that of iodine. It was supposed that a part of the cesium iodide that was deposited in the upstream test section reacted with boric oxide to form cesium metaborate.