In Tokamak-based fusion technology, a considered severe accident issue is inherent to a sudden overpressure inside the Vacuum Vessel (VV). Basically, this is due to a failure of a number of elements of the Tokamak Water Cooling System (TWCS), occurring in the case of LOCA (Loss Of Coolant Accident). In order to mitigate the structural damages, which could be induced by such an accident, a proposed solution consists to connect the VV through a Relief Line (RL) equipped by Rupture Discs (RD) to an auxiliary Pressure Suppression Water Tank (PSWT) system to allow a quick condensation of the released steam under vacuum conditions. The emergency facility, a key system from the safety point of view, is designed to protect the whole integrity of the VV. The Direct Contact Condensation (DCC) of steam in water is the considered process, used to lower the sudden overpressure within the VV. The DCC of steam has been extensively analyzed and experimentally investigated at atmospheric pressures in the past decades. These studies were mainly performed to optimize the design of the pressure suppression systems of boiling water nuclear reactors operating at atmospheric pressure. However, up to date. at subatmospheric pressure conditions, no explicit experimental data are available. To remedy to this lack, we carried out an extended experimental study of the DCC of steam at subatmospheric conditions and different water temperature. For this purpose, we performed numerous condensation tests (about 300 tests) in which the main influencing parameters, such as the steam mass flux (G), water temperature (T) and pool pressure (P) are combined. The tests analyze the condensation regime of steam injected into water at sub-atmospheric pressures, ranging from 4.2 up to 120 kPa and water pool temperature ranging from 10 up to 85°C. This experimental study is crucial for a better design of such facilities. It enables a precise prediction of the three-dimensional diagram (G,T,P,) of steam condensation regimes for different steam mass flux (G), water temperature (T) and pool pressure (P). It is the scope of this article to present and to discuss the main experimental results achieved through this work.

Three-dimensional condensation regime diagram for direct contact condensation of steam injected into water at subatmospheric conditions

MAZED, DAHMANE;DEL SERRA, DANIELE;AQUARO, DONATO;LO FRANO, ROSA
2016-01-01

Abstract

In Tokamak-based fusion technology, a considered severe accident issue is inherent to a sudden overpressure inside the Vacuum Vessel (VV). Basically, this is due to a failure of a number of elements of the Tokamak Water Cooling System (TWCS), occurring in the case of LOCA (Loss Of Coolant Accident). In order to mitigate the structural damages, which could be induced by such an accident, a proposed solution consists to connect the VV through a Relief Line (RL) equipped by Rupture Discs (RD) to an auxiliary Pressure Suppression Water Tank (PSWT) system to allow a quick condensation of the released steam under vacuum conditions. The emergency facility, a key system from the safety point of view, is designed to protect the whole integrity of the VV. The Direct Contact Condensation (DCC) of steam in water is the considered process, used to lower the sudden overpressure within the VV. The DCC of steam has been extensively analyzed and experimentally investigated at atmospheric pressures in the past decades. These studies were mainly performed to optimize the design of the pressure suppression systems of boiling water nuclear reactors operating at atmospheric pressure. However, up to date. at subatmospheric pressure conditions, no explicit experimental data are available. To remedy to this lack, we carried out an extended experimental study of the DCC of steam at subatmospheric conditions and different water temperature. For this purpose, we performed numerous condensation tests (about 300 tests) in which the main influencing parameters, such as the steam mass flux (G), water temperature (T) and pool pressure (P) are combined. The tests analyze the condensation regime of steam injected into water at sub-atmospheric pressures, ranging from 4.2 up to 120 kPa and water pool temperature ranging from 10 up to 85°C. This experimental study is crucial for a better design of such facilities. It enables a precise prediction of the three-dimensional diagram (G,T,P,) of steam condensation regimes for different steam mass flux (G), water temperature (T) and pool pressure (P). It is the scope of this article to present and to discuss the main experimental results achieved through this work.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/833414
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