Experimental and Analytical Study on the Behavior of Cesium Iodide Aerosol/Vapor Deposition onto Inner Surface of Pipe Wall under Severe Accident Conditions

Abstract

The WAVE experiments have been performed a t JAERI to investigate the CSI deposition onto the inner surface of pipe wall under typical severe accident conditions. It was shown that relatively large amount of CsI was deposited a t the upstream floor of the pipe and that larger amount of CsI was deposited on the ceiling than the floor a t the downstream. Analyses of the experiments have also been conducted with the three-dimensional thermohydraulic code. SPRAC, and the radionuclide transport analysis code, ART. The experimental results were well reproduced with ART by using peripherally subdivided pipe cross section and associated representative thermohydraulic information from SPRAC prediction. It was clarified through the present experiment and analyses that major deposition mechanisms for the chemical form of CsI are thermophoresis and condensation. Accordingly, the coupling of the FP behavior and the detailed thermohydrau!ic analyses was found to be essential in order to accurately predict the CsI deposition in the pipe, to which little attention has been paid in the previous studies.W.4 V E experiment, cesium iodide, aerosol. deposition. severe accident,

Revaporization Behavior of Cesium and Iodine Compounds from Their Deposits in the Steam–Boron Atmosphere

“…The deposition fraction is defined as the ratio of respective elements at a certain location to the total amount of such an element collected in TGTs, filters, and gas trapping. In the deposition phase, 16 a noticeably large amount of Cs and I was deposited in the regions with a temperature range of 870− 830 K and 820−780 K. This deposition was a result of cesium iodide condensation (903 K 34 ), which is similar to that in the report by Sato et al, 21 who indicated that the highest deposition occurred in the mid-part of "Area A" in their study (i.e., corresponded to approximately 840−790 K in the vertical tube), and in another report by Hidaka et al 35 with the study of CsI deposition under a nitrogen gas flow where they observed the highest deposition on coupon nos. 2 and 3 (930− 790 K).…”

Chemical stability of caesium iodide deposits in air/steam atmosphere

“…This suggests the presence of a larger amount of aerosols, which in turn prevent a reliable measurement of I 2 . 1 wt% wrt the total collected Cs and I at the end of test 2 As measured by UV-Visible spectroscopy 3 As measured by ICP-MS 4 As measured by TGA…”

“…It is the case with the re-vaporization of FPs deposits from the surface of the RCS. FPs will form deposits on the surface of the RCS by different mechanisms, the most important of which are vapour condensation and thermophoresis as predicted by Hidaka et al [4] and Maruyama et al [5], as well as gravity deposition. The Phébus-FP experimental program has shown that Cs and I can significantly deposits in the RCS [6].…”