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TOSQAN facility

​TEST STATION FOR SIMULATION AND QUALIFICATION IN AIRBORNE CONDITIONS]

The TOSQAN facility is used to simulate thermo-hydraulic conditions representative of accident scenarios likely to occur in the containment of a nuclear reactor. In particular, it can be used to evaluate the influence of steam condensing on the wall or of a spray device or to study the behavior of aerosols. Its use extends to other situations requiring study, in addition to pressurized water reactors, such as the safety of tokamaks.

TOSQAN facility

The

TOSQAN facility

​TEST STATION FOR SIMULATION AND QUALIFICATION IN AIRBORNE CONDITIONS]

The TOSQAN facility is used to simulate thermo-hydraulic conditions representative of accident scenarios likely to occur in the containment of a nuclear reactor. In particular, it can be used to evaluate the influence of steam condensing on the wall or of a spray device or to study the behavior of aerosols. Its use extends to other situations requiring study, in addition to pressurized water reactors, such as the safety of tokamaks.

Background and objectives of the facility

​The TOSQAN experimental facility was commissioned in the early 2000s to study the main phenomena governing hydrogen distribution in the containment of a reactor (condensation on the wall, exchanges of mass and heat caused by the sump or the containment spray system) and the associated formation of flammable mixtures. For the last ten years, the facility’s scope of application has been extended to other areas of nuclear safety such as studying the risk of aerosol dispersion during corium removal from the Fukushima reactors and loss of vacuum accidents through water or air ingress into the vacuum vessel of the future ITER fusion facility. The experimental data acquired in TOSQAN contribute to the validation of computer codes used in nuclear safety.

​View of the central part of the TOSQAN facility vessel
@ Francesco Acerbis / Médiathèque IRSN

Background and objectives of the facility

Background and objectives of the facility
​View of the central part of the TOSQAN facility vessel
@ Francesco Acerbis / Médiathèque IRSN

​The TOSQAN experimental facility was commissioned in the early 2000s to study the main phenomena governing hydrogen distribution in the containment of a reactor (condensation on the wall, exchanges of mass and heat caused by the sump or the containment spray system) and the associated formation of flammable mixtures. For the last ten years, the facility’s scope of application has been extended to other areas of nuclear safety such as studying the risk of aerosol dispersion during corium removal from the Fukushima reactors and loss of vacuum accidents through water or air ingress into the vacuum vessel of the future ITER fusion facility. The experimental data acquired in TOSQAN contribute to the validation of computer codes used in nuclear safety.

Principle and description

​TOSQAN consists of a closed cylindrical vessel (volume 7 m3, height 4 m, internal diameter 1.5 m) in which controlled injections of steam and various non-radioactive and non-explosive gases and aerosols are performed to simulate the thermo-hydraulic conditions of a core melt accident affecting a nuclear reactor (maximum design basis pressure and temperature: 6bar –160°C).

 

 

Instrumentation associated with the TOSQAN vessel
@ ​Seignette Olivier - Lafontan Mikaël / Médiathèque IRSN

Principle and description

Principle and description
Instrumentation associated with the TOSQAN vessel
@ ​Seignette Olivier - Lafontan Mikaël / Médiathèque IRSN

​TOSQAN consists of a closed cylindrical vessel (volume 7 m3, height 4 m, internal diameter 1.5 m) in which controlled injections of steam and various non-radioactive and non-explosive gases and aerosols are performed to simulate the thermo-hydraulic conditions of a core melt accident affecting a nuclear reactor (maximum design basis pressure and temperature: 6bar –160°C).

 

 

 

 

 

 

Schematic diagram of TOSQAN facility vessel

 

 

 Modifications made for the study on dust resuspension in the ITER fusion installation

​Instrumentation associated with the TOSQAN vessel
(c) Francesco Acerbis / IRSN Médiathèque
​Instrumentation associated with the TOSQAN vessel
(c) Francesco Acerbis / IRSN Médiathèque

 

 

 

 

Schematic diagram of TOSQAN facility vessel

 

 

 Modifications made for the study on dust resuspension in the ITER fusion installation

TOSQAN instrumentation

​TOSQAN’s instrumentation is designed for the characterization of multiphase flows under hostile experimental conditions. The facility has a high level of instrumentation in terms of both density and diversity, as a result of specific developments with partner universities (CNRS CORIA). These means of measurement, mostly based on innovative optical methods, can locally and non-intrusively characterize multiphase flows consisting of gaseous mixtures (air, water vapor and helium used to simulate the presence of hydrogen), water droplets and aerosols simulating a release of fission products.

Haomin SUN, researcher at JAEA (Japan), is hosted by the laboratory for several months to work on aerosol spraydown in a containment in a severe accident situation and on the MITHYGENE project
(c) Francesco Acerbis / ​IRSN Médiathèque

TOSQAN instrumentation

TOSQAN instrumentation
Haomin SUN, researcher at JAEA (Japan), is hosted by the laboratory for several months to work on aerosol spraydown in a containment in a severe accident situation and on the MITHYGENE project
(c) Francesco Acerbis / ​IRSN Médiathèque

​TOSQAN’s instrumentation is designed for the characterization of multiphase flows under hostile experimental conditions. The facility has a high level of instrumentation in terms of both density and diversity, as a result of specific developments with partner universities (CNRS CORIA). These means of measurement, mostly based on innovative optical methods, can locally and non-intrusively characterize multiphase flows consisting of gaseous mixtures (air, water vapor and helium used to simulate the presence of hydrogen), water droplets and aerosols simulating a release of fission products.

Optical diagnostics, a specialism of TOSQAN

For measuring droplet velocity:

Laser Doppler Velocimetry (LDV)Particle Image Velocimetry (PIV)

For measuring droplet size:

out-of-focus imaging (interferometrics laser imaging for droplet sizing (ILIDS)), which is used to measure diameter by analyzing the interference fringes created by the interaction of a laser and a droplet. See video below.
 

For measuring droplet temperature:

rainbow refractometry
 

For measuring concentrations of gases:

Spontaneous Raman Scattering (SRS) spectrometry, which uses the inelastic interaction between an incident photon from the laser and a polyatomic molecule.
 

Other measurements performed

Gases: concentration, temperature (K), velocity, turbulence, pressure

Droplets: diameter, velocity, temperature

Aerosols: diameter, concentration

​Emmanuel Porcheron, researcher at the Aerosol Physics and Metrology Laboratory (LPMA) fo the IRSN, in front of the out-of-focus imaging analysis equipment. On the screen, droplets showing the interference created by interaction with the laser.
(c) Francesco Acerbis / IRSN Médiathèque
​Emmanuel Porcheron, researcher at the Aerosol Physics and Metrology Laboratory (LPMA) fo the IRSN, in front of the out-of-focus imaging analysis equipment. On the screen, droplets showing the interference created by interaction with the laser.
(c) Francesco Acerbis / IRSN Médiathèque

Optical diagnostics, a specialism of TOSQAN

For measuring droplet velocity:

Laser Doppler Velocimetry (LDV)Particle Image Velocimetry (PIV)

For measuring droplet size:

out-of-focus imaging (interferometrics laser imaging for droplet sizing (ILIDS)), which is used to measure diameter by analyzing the interference fringes created by the interaction of a laser and a droplet. See video below.
 

For measuring droplet temperature:

rainbow refractometry
 

For measuring concentrations of gases:

Spontaneous Raman Scattering (SRS) spectrometry, which uses the inelastic interaction between an incident photon from the laser and a polyatomic molecule.
 

Other measurements performed

Gases: concentration, temperature (K), velocity, turbulence, pressure

Droplets: diameter, velocity, temperature

Aerosols: diameter, concentration

​Interior view of the vessel at the TOSQAN facility during a spray experiment, with the laser used to perform the size and velocity measurements by ILIDS and PIV
(c) Francesco Acerbis /​ IRSN Médiathèque
​Interior view of the vessel at the TOSQAN facility during a spray experiment, with the laser used to perform the size and velocity measurements by ILIDS and PIV
(c) Francesco Acerbis /​ IRSN Médiathèque

Linked research programs

​The research programs carried out in TOSQAN were initially part of research being conducted at IRSN on severe accidents likely to affect nuclear reactors. TOSQAN was designed in particular for studies of hydrogen distribution: the violent hydrogen combustion generated by reactor core degradation can damage the reactor containment or cause the loss of its safety systems. Today, the facility’s scope of application has been expanded to areas involving the characterization and analysis of similar physical mechanisms.

​General view of the TOSQAN facility
(c) Francesco Acerbis / IRSN Médiathèque

Linked research programs

Linked research programs
​General view of the TOSQAN facility
(c) Francesco Acerbis / IRSN Médiathèque

​The research programs carried out in TOSQAN were initially part of research being conducted at IRSN on severe accidents likely to affect nuclear reactors. TOSQAN was designed in particular for studies of hydrogen distribution: the violent hydrogen combustion generated by reactor core degradation can damage the reactor containment or cause the loss of its safety systems. Today, the facility’s scope of application has been expanded to areas involving the characterization and analysis of similar physical mechanisms.

Current programs

ITER: dust dispersion in the vacuum vessel of a fusion reactor

As part of the ITER project for fusion research, dust dispersion in the tokamak’s vacuum vessel is being studied. TOSQAN can simulate certain accident scenarios (loss of vacuum due to air or water ingress) that could occur in the ITER Tokamak, to acquire experimental data that will be used to validate computer codes.

Videos below:

view of flash-boiling and bubbles in the injection pipe of water at 6 kg/h in the FAAMUS facility under a pressure of 1 mBar and at 20°CDust resuspension under an air injection in TOSQAN
​The FAAMUS facility (flash atomization and aerosol mobilization under vacuum system) was developed during the thesis by Benjamin Blaisot to study water ingress into the containment under vacuum of the Tokamak at the ITER fusion facility.
(c) Francesco Acerbis / IRSN Médiathèque
​The FAAMUS facility (flash atomization and aerosol mobilization under vacuum system) was developed during the thesis by Benjamin Blaisot to study water ingress into the containment under vacuum of the Tokamak at the ITER fusion facility.
(c) Francesco Acerbis / IRSN Médiathèque

Current programs

ITER: dust dispersion in the vacuum vessel of a fusion reactor

As part of the ITER project for fusion research, dust dispersion in the tokamak’s vacuum vessel is being studied. TOSQAN can simulate certain accident scenarios (loss of vacuum due to air or water ingress) that could occur in the ITER Tokamak, to acquire experimental data that will be used to validate computer codes.

Videos below:

view of flash-boiling and bubbles in the injection pipe of water at 6 kg/h in the FAAMUS facility under a pressure of 1 mBar and at 20°CDust resuspension under an air injection in TOSQAN

​Fukushima decommissioning: characterization of aerosols from the laser cutting of corium

IRSN is involved in a project being run by the ONET group in collaboration with the CEA, to assess the feasibility of laser cutting to recover the core of the damaged reactors at the Fukushima plant, as part of the decommissioning process. IRSN is participating in this project by studying the problems related to the dispersion of the aerosols generated by cutting. By identifying the aerosol source term suspended during laser cutting and by proposing and assessing the effectiveness of strategies to contain the aerosols, IRSN is helping to evaluate the radiological risk to humans and the environment.

​Opening one of the ports in the TOSQAN facility vessel
(c) Francesco Acerbis / Médiathèque IRSN
​Opening one of the ports in the TOSQAN facility vessel
(c) Francesco Acerbis / Médiathèque IRSN

​Fukushima decommissioning: characterization of aerosols from the laser cutting of corium

IRSN is involved in a project being run by the ONET group in collaboration with the CEA, to assess the feasibility of laser cutting to recover the core of the damaged reactors at the Fukushima plant, as part of the decommissioning process. IRSN is participating in this project by studying the problems related to the dispersion of the aerosols generated by cutting. By identifying the aerosol source term suspended during laser cutting and by proposing and assessing the effectiveness of strategies to contain the aerosols, IRSN is helping to evaluate the radiological risk to humans and the environment.

​Study of the spraydown by precipitations of aerosols emitted into the environment in accident situations

This program, which is still running, used the TOSQAN facility between 2009 and 2012 to determine the phenomenological laws describing the deposition of aerosols by different types of rainfall, by means of highly controlled and heavily instrumented analytical experiments. The TOSQAN facility can simulate certain conditions representative of atmospheric deposition: millimeter-scale droplets, terminal fall velocity, rainfall intensity. A thesis directed by the Physical Meteorology Laboratory (LAMP) in Clermont Ferrand was carried out as part of this program (see the thesis of A. Quérel).

​Spray nozzle inside the TOSQAN vessel
(c) Francesco Acerbis / Médiathèque IRSN
​Spray nozzle inside the TOSQAN vessel
(c) Francesco Acerbis / Médiathèque IRSN

​Study of the spraydown by precipitations of aerosols emitted into the environment in accident situations

This program, which is still running, used the TOSQAN facility between 2009 and 2012 to determine the phenomenological laws describing the deposition of aerosols by different types of rainfall, by means of highly controlled and heavily instrumented analytical experiments. The TOSQAN facility can simulate certain conditions representative of atmospheric deposition: millimeter-scale droplets, terminal fall velocity, rainfall intensity. A thesis directed by the Physical Meteorology Laboratory (LAMP) in Clermont Ferrand was carried out as part of this program (see the thesis of A. Quérel).

Past programs

The ​flagship research behind TOSQAN: the study of hydrogen risks in the event of a severe accident at a nuclear reactor 

The mechanical effects resulting from combustion of the hydrogen emitted during reactor core degradation can damage the reactor containment or lead to the loss of its safety systems. The TOSQAN program, followed by the ERCOSAM program (FP7) (both run between 2000 and 2010), studied the main phenomena influencing hydrogen distribution in the containment of a reactor, which can lead to the formation of flammable mixtures. In particular, the TOSQAN spray program studied evaporation/condensation of the water droplets generated by the nozzles and the trapping of aerosols in water droplet sprays representative of the situation in a reactor. The experimental data acquired over a period of approximately 10 years, in more than 300 analytical experiments, helped to validate the different physical models embedded in the nuclear safety computer codes used or developed at IRSN (P2REMICS, Astec), and thus to verify the ability of the computer codes to simulate hydrogen distribution.

 

ALIDS, development of airborne optical instrumentation

The ALIDS project, coordinated by IRSN in the context of the FP7 EUFAR network, concerned the development of airborne optical instrumentation installed in aircraft to measure the drop size of water droplets in clouds. The ALIDS probe is based on the out-of-focus imaging optical diagnosis technique used in the TOSQAN facility to characterize the size of spray droplets.

​View, through a port in the TOSQAN vessel, of the spray lit by the optical diagnostic laser
(c) Francesco Acerbis / Médiathèque IRSN

Past programs

Past programs
​View, through a port in the TOSQAN vessel, of the spray lit by the optical diagnostic laser
(c) Francesco Acerbis / Médiathèque IRSN

The ​flagship research behind TOSQAN: the study of hydrogen risks in the event of a severe accident at a nuclear reactor 

The mechanical effects resulting from combustion of the hydrogen emitted during reactor core degradation can damage the reactor containment or lead to the loss of its safety systems. The TOSQAN program, followed by the ERCOSAM program (FP7) (both run between 2000 and 2010), studied the main phenomena influencing hydrogen distribution in the containment of a reactor, which can lead to the formation of flammable mixtures. In particular, the TOSQAN spray program studied evaporation/condensation of the water droplets generated by the nozzles and the trapping of aerosols in water droplet sprays representative of the situation in a reactor. The experimental data acquired over a period of approximately 10 years, in more than 300 analytical experiments, helped to validate the different physical models embedded in the nuclear safety computer codes used or developed at IRSN (P2REMICS, Astec), and thus to verify the ability of the computer codes to simulate hydrogen distribution.

 

ALIDS, development of airborne optical instrumentation

The ALIDS project, coordinated by IRSN in the context of the FP7 EUFAR network, concerned the development of airborne optical instrumentation installed in aircraft to measure the drop size of water droplets in clouds. The ALIDS probe is based on the out-of-focus imaging optical diagnosis technique used in the TOSQAN facility to characterize the size of spray droplets.

​TOSQAN vessel, overhead view
(c) Francesco Acerbis / Médiathèque IRSN
​TOSQAN vessel, overhead view
(c) Francesco Acerbis / Médiathèque IRSN

Tosqan caracteristics

Volume: 7 m³Height: 4.8 mDiameter: 1.5 mOptical access points: 14Pressure: 1 to 6 barTemperature: up to 160°CSteam injection: flow rate from 1 to 30 g/sSpray injection: flow rate from 1 to 40 g/sSpray water temperature: 20°C to 90°C

 
​Interior view of the facility during spraying and with the optical diagnostic laser
(c) Francesco Acerbis / IRSN Médiathèque
Tosqan caracteristics
​Interior view of the facility during spraying and with the optical diagnostic laser
(c) Francesco Acerbis / IRSN Médiathèque

Tosqan caracteristics

Volume: 7 m³Height: 4.8 mDiameter: 1.5 mOptical access points: 14Pressure: 1 to 6 barTemperature: up to 160°CSteam injection: flow rate from 1 to 30 g/sSpray injection: flow rate from 1 to 40 g/sSpray water temperature: 20°C to 90°C