Fusion Engineering and Design 81 (2006) 1347–1351 Dust mobilization by high-speed vapor flow under LOVA K. Matsuki a , S. Suzuki a,∗ , S. Ebara b , T. Yokomine b , A. Shimizu b a Department of Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Japan b Division of Energy Engineering and Science, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Japan Received 1 February 2005; received in revised form 27 September 2005; accepted 27 September 2005 Available online 20 December 2005 Abstract In the safety analysis on the International Thermonuclear Experimental Reactor (ITER), the ingress of coolant (ICE) event and the loss of vacuum (LOVA) event are considered as one of the most serious accident. On the assumption of LOVA occurring after ICE, it is inferable that activated dusts are under the wet condition. Transport behavior of in-vessel activated dusts under the wet condition is not well understood in comparison with the dry case. In this study, we experimentally investigated the entrainment behavior of dust under LOVA after ICE. We measured dust entrainment by high-speed humid airflow with phase change. Graphite dusts and glass beads are used as substitutions for mobile inventory. The relations among the relative humidity, the entrainment of particles in the exhaust gas flow and the adhesion rate of dust particles on the pipe wall have been made clear, as has the distribution profile of dust deposition on the pipe wall. The entrainment ratio decreased as the relative humidity increased and increased as the initial pressure difference increased. © 2005 Elsevier B.V. All rights reserved. Keywords: Dust mobilization; LOVA; Dust entrainment 1. Introduction A vacuum vessel of a Tokamak fusion reactor like the International Thermonuclear Experimental Reac- tor (ITER) consists of the first confinement barrier, which includes a large amount of radioactive materi- ∗ Corresponding author at: Department of Advanced Energy Engi- neering Science, Interdisciplinary Graduate School of Engineering Sciences, Kysuhu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580, Japan. Tel.: +81 92 583 7603; fax: +81 92 583 7601. E-mail address: Suzuki@aees.kyushu-u.ac.jp (S. Suzuki). als, such as tritium and activation products. The loss of vacuum event (LOVA) is considered as an indepen- dent design basis event. In the ICE event the cooling tubes installed into plasma-facing components are bro- ken and the cooling water enters into the vacuum vessel. Then the cooling water boils and evaporates because of the high temperature of the in-vessel components and the low pressure in the vacuum vessel. Consequently, the pressure in the vacuum vessel increases rapidly. Then some safety devices such as the vacuum vessel pressure suppression system (VVPSS) are suppose to start. However, we should consider the LOVA event as 0920-3796/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2005.09.058