The TOSQAN experimental vessel is a large stainless steel cylindrical enclosure (volume of 7 m3, height of 4 m, internal diameter of 1.5 m) with double walls. A coolant circulates in between the walls to regulate the wall temperature from 60 °C to 160 °C.
Non radioactive aerosols, steam and non explosive gases can be injected at different controlled flow rates via diverse injection pipes located at different locations of the enclosure. Thus, thermal-hydraulic conditions representative of a severe accident in nuclear reactors can be simulated (sizing pressure: 7 bar – wall temperature: 160 °C).
General view of the TOSQAN facility
The experiment is meant to study the physical phenomena that affect hydrogen distribution in the reactor containment such as: steam wall condensation, heat mass and momentum exchanges with the sump or with the containment spray systems. These different phenomena have been studied during specific test phases.
Schematic view of the TOSQAN facility
(D: diameter, C: concentration, T: temperature, V: velocity)
This facility is highly instrumented both in terms of measurement density and diversity; this instrumentation has required specific developments in collaboration with academic partners (CNRS CORIA). Most of this instrumentation is based on innovative optical diagnostics. It allows characterizing accurately and non-intrusively the multiphase flow composed of various gases (air, steam, and helium used as a surrogate of hydrogen), water droplets, and aerosols simulating the fission products.
Thus, different instrumentations are used: PIV (particle image velocimetry), LDV (laser doppler velocimetry), rainbow refractometry, out of focus imaging and SRD (spontaneous Raman diffusion) spectrometry.
Optical system for characterising a spraying nozzle