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Luu, V. N.; 中島 邦久; Rizaal, M.; 三輪 周平
Proceedings of International Topical Workshop on Fukushima Decommissioning Research 2024 (FDR2024) (Internet), 4 Pages, 2024/10
The trapping behavior of cesium (Cs) on concrete, such as pedestal and shield plugs, was assessed through multiple deposition tests of CsOH aerosols on concrete phase-CaCO within a temperature range of 170
C to 570C under humid conditions. The deposition rate of CsOH aerosols on CaCO as a function of temperature was examined. X-ray diffraction analysis revealed the presence of water-soluble Cs
CO on CaCO samples up to 420C, but negligible detection above this temperature. This finding is supported by quantitative analyses of Cs weight gain and chemical analysis, demonstrating an increase in deposition rate up to 420C, followed by a decline thereafter. The increased deposition rate is attributed to the chemical interaction between CsOH and CaCO, while the diminished rate beyond 420C may result from the decomposition of CaCO under steam, thereby reducing the available reactant for the chemical reaction with CsOH.
-CsOHRizaal, M.; Luu, V. N.; 中島 邦久; 三輪 周平
Proceedings of International Topical Workshop on Fukushima Decommissioning Research 2024 (FDR2024) (Internet), 4 Pages, 2024/10
Thermochemistry prevailing between gaseous CsOH and concrete main chemical phase CaCO at temperatures up to 570C was investigated with various scenarios using the thermogravimetric method. The aim was to elucidate the decreasing behavior of cesium (Cs) trapping on CaCO observed in the transpiration method. A quasi-two-compartment platinum crucible was developed to realize co-measurements of both CsOH and CaCO during thermal treatment. Post-test X-ray diffraction was conducted to identify the chemical compound formed on the CaCO precursor. The early presence (timely sensitivity) of CsOH near the heated surface of CaCO was found to play a key role in the trapping (in the form of CsCO). Such a factor is crucial because, otherwise, the Ca(OH) would predominate the surface upon CaCO decomposition where leading to no reaction with CsOH.
at temperature range 170 - 290CLuu, V. N.; 中島 邦久
Nuclear Engineering and Design, 426, p.113402_1 - 113402_7, 2024/09
被引用回数：3 パーセンタイル：49.06(Nuclear Science & Technology)A field assessment at the Fukushima-Daiichi Nuclear Power Station revealed high radioactivity on the concrete shield plugs, which is estimated above 20 PBq for Cs-137 at units 2 and 3. This leads to significant interest in the retention of Cs on concrete during severe accidents (SA). However, the interaction of CsOH, as one of the main Cs forms released in SA, with concrete surfaces at elevated temperatures remains poorly researched. In this study, we have experimentally investigated the deposition behavior of CsOH on CaCO, which is the primary phase existing on the surface of concrete, under humid atmosphere. As a result, the chemical reaction enhanced deposition rate (N), and increased linearly with CsOH concentration (C
), as following expression: N(
g/cm
s) = v
C, where v is temperature-dependent deposition velocity as given by ln v (cm/s) = -3785.8/T + 3.766, for T in the range of 170 and 290 C. This empirical model can be integrated into severe accident codes to quantify the chemical trapping of cesium on concrete surfaces during ex-vessel release. Moreover, it can contribute to understanding the reasons behind the high dose rate on concrete shield plugs at the Fukushima Daiichi Nuclear power stations and aid in developing effective decommissioning practices for concrete structures.
at temperature range 170 - 290 CLuu, V. N.; 中島 邦久
no journal, ,
A recent field survey revealed extremely high radioactivity on the concrete shield plugs, exceeding 20 PBq for Cs-137 at units 2, 3 of 1F. This leads to significant interest in the retention of Cs on concrete during severe accident. Despite this, the interaction of Cs vapors and/or aerosols in the gas phase with concrete surfaces at high temperatures remains inadequately explored. In this work, we investigated the deposition behavior of CsOH on CaCO, as a primary phase on the concrete surface, under humid atmosphere. As a result, the chemical reaction enhanced deposition rate, and increased linearly with CsOH concentration.
