Amandine Nuboer

Study of Heat Transfer and Mass Transfer in a Spray for Containment Application: Analysis of the Influence of Spray Temperature at the Injection Point

Abstract During the course of a hypothetical severe accident in a nuclear power plant, spray may be activated in order to reduce static pressure in the containment. The Institut de Radioprotection et de Sûreté Nucléaire (IRSN) has developed the TOSQAN experiment to provide a better understanding of the heat transfer and mass transfer that take place between a spray and the surrounding confined gas in such a situation. This paper studies how the temperature of the spray at the injection point influences the dynamics of a test. To carry out this analysis, we performed two spray tests: spray test 101 (ST101), which served as a reference, and spray test 107 (ST107), which had exactly the same initial and boundary conditions except for the temperature of the spray at the injection point, which varied from 25°C to 58°C. First, we present the entire scenario for ST101 and ST107 and the results of the tests. We then focus our analysis on the intercomparison of the thermal-hydraulic behavior induced by the spray temperature at the injection point and the wall temperature. This intercomparison is divided into two parts: global and local.

SUMP INFLUENCE ON CONTAINMENT THERMAL HYDRAULIC: RESULTS OF THE TOSQAN TESTS

This paper presents the results of the TOSQAN tests performed in the field of the TOSQAN sump program undertaken by the Institut de Radioprotection et de Surete Nucleaire (IRSN). This work is devoted to study the heat and mass transfers induced by the water sump towards the containment atmosphere, for typical accidental thermal hydraulic conditions in PWR.Copyright

Influence of Sump on Containment Thermal Hydraulics: Synthesis of the TOSQAN Tests

During the course of a severe accident in a nuclear power plant, water can be collected in the sump containment through steam condensation on walls, cooling circuit leak, and by spray systems activation. Therefore, the sump can become a place of heat and mass exchanges through water evaporation and steam condensation, which influences the distribution of hydrogen released in containment during nuclear core degradation. The objective of this paper is to present the analysis of semi-analytical experiments on sump interaction between containment atmosphere for typical accidental thermal hydraulic conditions in a pressurized water reactor (PWR). Tests are conducted in the TOSQAN facility developed by the Institut de Radioprotection et de Surete Nucleaire in Saclay. The TOSQAN facility is particularly well adapted to characterize the distribution of gases in a containment vessel. A tests’ grid was defined to investigate the coupled effect of the sump evaporation with wall condensation, for air steam conditions, with noncondensable gases (He, SF6), and for steady and transient states (two depressurization tests).

Semi-Analytical Study of Aerosol Washout by Rain

The accidents of Chernobyl and Fukushima have shown the necessity to better understand all the mechanisms implied in the scavenging of aerosol particles released to the atmosphere during a nuclear accident.Among all the phenomena involved in the deposition of aerosol particles, we focus here on the aerosol particles scavenging by the raindrops below the clouds, also called washout (as opposed to the rainout, which concerns scavenging inside the clouds). The strategy of IRSN to enhance the knowledge and the modelling of any mechanism involved in the washout of aerosol particles by rain spans from environmental studies, to analytical ones.The semi-analytical approach chosen here is halfway between these two modes of reasoning. A companion paper is also submitted to the conference to present the microphysical approach chosen at IRSN.In order to perform this study, aerosol particles were dispersed in the TOSQAN chamber, which is a large cylindrical enclosure (4.8 m height with 1.5 m internal diameter). The aerosol particles once dispersed, synthetic rains of different kinds (from stratiform to convective rains) can be activated. Finally, the instantaneous spectral scavenging coefficients are determined from the spectral decrease of aerosol particles concentration in the chamber as a function of time.In order to be able to produce synthetic rains representative of any tropospheric events, a special generator has been designed; it is based on a vibro-rotative disk. This generator is able to produce monodispersed rains at the top of the TOSQAN chamber with rainfall rates from 7 to 15 mm/h and drops diameters from 0.5 to 2.5 mm injected at velocities close to their terminal one.During these tests, the spectral aerosol concentration is measured in line with the help of a Welas granulometer. This instrument is based on white light scattering.The results of these experiments highlight the influence of “meteorological” conditions inside the chamber on the washout of the chamber atmosphere, especially when the relative humidity is reaching saturation.Copyright