Hydrogen explosion mitigation in DEMO vacuum vessel pressure suppression system using passive recombiners

The Vacuum Vessel Pressure Suppression System (VVPSS), a key safety system of the ITER plant, is designed to protect the Vacuum Vessel (VV) from over pressure occurring in the case of LOCA (Loss Of Coolant Accident) or other pressurizing accidents such as LOVA (Loss Of Vacuum Accident). The steam condensation in the Suppression Tanks (main elements of the VVPSS system), occurs at sub-atmospheric pressure. The steam condensation, at pressures equal or greater than the atmospheric, has been numerically analyzed and experimentally investigated in the past in order to optimize the design of the pressure suppression system of boiling water nuclear reactors. However, very limited experimental data is available concerning the steam condensation in a water tank at sub-atmospheric pressure. In order to analyze the steam condensation in these operating conditions, an experimental study, funded by ITER Organization, is conducted at the Department of Civil and Industrial Engineering (DICI) of University of Pisa. The tests analyze the condensation of saturated or superheated steam at sub-atmospheric pressures (4.2 kPa and slightly above the water vapour saturation pressure), and pool temperature up to 50°C at several heights of water head. The experimental facility, to perform this study, has been set up with a significant scaling factor regarding the full size installation at ITER. In this paper the experimental rig, the conditions of the experiments, and the test matrix are presented. The temperature and pressure measurements with details of the data acquisition system are described. The tests were performed at different patterns of the sparger exit holes (1, 3 and 9) and for three steam mass flow rates per one hole. The results show very high efficiency of condensation for all examined conditions. Finally, a comparison between the condensation regimen at sub-atmospheric and at atmospheric pressure is discussed.

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Experimental results of functional performance of a vacuum vessel pressure suppression system in ITER

Fusion Engineering and Design ◽

10.1016/s0920-3796(02)00242-9 ◽

2002 ◽

Vol 63-64 ◽

pp. 217-222 ◽

Cited By ~ 4

Author(s):

Mitsuhiko Shibata ◽

Kazuyuki Takase ◽

Hironori Watanabe ◽

Hajime Akimoto

Keyword(s):

Functional Performance ◽

Experimental Results ◽

Vacuum Vessel ◽

Suppression System

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Experimental investigation of functional performance of a vacuum vessel pressure suppression system of ITER

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2017.09.010 ◽

2017 ◽

Vol 122 ◽

pp. 42-46 ◽

Cited By ~ 11

Author(s):

R. Lo Frano ◽

D. Mazed ◽

D. Aquaro ◽

D. Del Serra ◽

F. Orlandi

Keyword(s):

Experimental Investigation ◽

Functional Performance ◽

Vacuum Vessel ◽

Suppression System

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Concept of operation of the remote handling system for the ITER vacuum vessel pressure suppression system

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2021.112875 ◽

2021 ◽

Vol 173 ◽

pp. 112875

Author(s):

Chang-Hwan Choi ◽

Shanshuang Shi ◽

Taku Yokoyama ◽

Christopher Hall ◽

Keelan Keogh ◽

...

Keyword(s):

Vacuum Vessel ◽

Handling System ◽

Remote Handling ◽

Suppression System

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CFD Thermal Analysis of ITER Pressure Suppression Tanks

Volume 9: Student Paper Competition ◽

10.1115/icone26-82550 ◽

2018 ◽

Author(s):

Lorenzo Basili ◽

Rosa Lo Frano ◽

Marco Olcese ◽

Igor Sekachev ◽

Donato Aquaro

Keyword(s):

Thermal Insulation ◽

Fusion Reactor ◽

Thermal Conditions ◽

Vacuum Vessel ◽

Bottom Part ◽

Optimum Configuration ◽

Computational Fluid Dynamics Cfd ◽

Tank Pressure ◽

Important System ◽

Suppression System

The aim of the paper is to investigate the thermal conditions (temperature distribution, heat losses) in the support system of the Vapour Suppression Tank (VST) of the Vacuum Vessel Pressure Suppression System (VVPSS), a safety important system of ITER fusion reactor, protecting the Vacuum Vessel (VV) against overpressures. The VVPSS includes four VSTs of identical volume and mounted as two stacked assemblies. The study focuses on the optimization of the design of the thermal insulation of the bottom part of the VST, connecting each two-tank stack to the basement, and also on the identification of the thermal loads at the interface between the tank support and the tank pressure boundary. A Computational Fluid Dynamics (CFD) analysis of the VST has been performed for four different insulation configurations and considering both steady state and transient loads following accidental conditions. The results of the analysis are used to provide recommendation on the optimum configuration of the thermal insulation. Measures for minimization of the thermal gradient in the critical area of the joint between the tank hemispherical head and support skirt to limit the thermal fatigue on the welds are also suggested.

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Prevention of hydrogen accumulation inside the vacuum vessel pressure suppression system of the ITER facility by means of passive auto-catalytic recombiners

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2018.07.039 ◽

2019 ◽

Vol 44 (17) ◽

pp. 8971-8980 ◽

Cited By ~ 5

Author(s):

P.-M. Steffen ◽

E.-A. Reinecke ◽

S. Kelm ◽

A. Bentaib ◽

N. Chaumeix ◽

...

Keyword(s):

Vacuum Vessel ◽

Hydrogen Accumulation ◽

Suppression System

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Computational Fluid Dynamics Thermal Analysis of ITER Pressure Suppression Tanks

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4048007 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Lorenzo Basili ◽

Rosa Lo Frano ◽

Marco Olcese ◽

Igor Sekachev ◽

Donato Aquaro

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Thermal Insulation ◽

Thermal Conditions ◽

Vacuum Vessel ◽

Optimum Configuration ◽

Computational Fluid Dynamics Cfd ◽

Tank Pressure ◽

Important System ◽

Suppression System

Abstract The aim of the paper is to present the results of the investigation of the thermal conditions (temperature distribution, heat losses) in the support system of the vapor suppression tank (VST) of the vacuum vessel pressure suppression system (VVPSS), a safety important system of ITER fusion reactor, protecting the vacuum vessel (VV) against overpressures. The VVPSS includes four VSTs of identical volume and installed as two stacked assemblies. The study focuses on the optimization of the design of the thermal insulation at the bottom of the VSTs, interfacing with the basement and also on the identification of the thermal loads at the interface between the tank support and the tank pressure boundary. A computational fluid dynamics (CFD) analysis of the VST has been performed for four different insulation configurations and considering both steady-state and transient loads following accidental conditions. The results of the analysis are used to provide recommendation on the optimum configuration of the thermal insulation. Measures for minimization of the thermal gradient in the critical area of the joint between the tank hemispherical head and support skirt to limit the thermal fatigue on the welds are also suggested.

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Deposition of Iter Vacuum Vessel Dust Inside the Pressure Suppression System During a Loss of Coolant Accident: Experimental and Numerical Analyses

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4050768 ◽

2021 ◽

Author(s):

Miriam Ibba ◽

Alessio Pesetti ◽

Michele Raucci ◽

Flavio Parozzi ◽

Roberta Lazzeri ◽

...

Keyword(s):

Numerical Simulations ◽

Numerical Analyses ◽

Water Tank ◽

Vacuum Vessel ◽

Dust Deposition ◽

Dust Mass ◽

Water Container ◽

Dust Distribution ◽

Experimental Rig ◽

Suppression System

Abstract This paper deals with an experimental and numerical analysis of the deposition of ITER dust simulant inside a reduced scale Vacuum Vessel Pressure Suppression System (VVPSS) of the International Thermonuclear Experimental Reactor (ITER). This research, funded by the ITER Organization, aims to analyse the dust deposition in a water container relevant for the ITER VVPSS, the dust removal by means of robotised apparatuses and their decontamination efficiency. The experimental rig, built at the Department of Civil and Industrial Engineering (DICI) of the University of Pisa (Italy), is described and the results of a preliminary experimental test are illustrated, underlining that 2 and 82% of dust mass was strongly and lightly bound to the water container surfaces, respectively, and 16 % were not deposited in the water tank. Furthermore, three numerical analyses were carried out implementing a model of the experimental rig in the Enel Code for Analysis of Radionuclide Transport (ECART) to determine the relevance of different parameters on the deposition, resuspension and removal of dust. The numerical simulations allowed to specify dust mass deposition on the different rig components, revealing a strong dust retention (about 66%) in the first part of the injection piping in case of coarse granulometry. Finest lognormal dust distribution was instead able to reach the water container (about 90%). Moreover, the numerical simulations permitted to define more precisely the test matrix and to analyse the experimental results.

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