Last update on December 2011
Study of wind effect on accidental contamination releases from a nuclear facility
Wind creates positive and negative pressure effects on buildings faces; those effects depend on the orientation of the face with respect to the wind direction. In the event of an accident situation leading to the emission of pollutant, and if the ventilation network is modified or even fails completely, the effects of the wind can alter the pollutants transfers inside the facility and the releases into the environment. At present, the modelling of the wind effect on pollutant releases is relatively rudimentary because the calculation codes used have not been sufficiently qualified. The aim of the TIVANO program is to improve this modelling by acquiring new experimental data.
Challenges and objectives
The TIVANO program (from the French acronym meaning "Transfers Induced by Wind in Accident and Nominal Operating Conditions) aims more particularly at qualifying the CFX calculation codes and the SYLVIA software
programs to better integrate the effects of wind in the release calculations, and improve certain models if necessary. CFX is a commercial fluid mechanics code (CFD) that allows the prediction of a fluid flow (air in this case) by resolving the Navier-Stokes equations. SYLVIA is a 0D software system developed by the IRSN to model the behaviour of industrial ventilation networks when accidental disturbances occur. The experimental data to qualify these tools (wind pressure coefficients Cp on buildings faces and chimneys) are acquired in a wind tunnel on scale models representing nuclear facilities. Thanks to this program, it will be possible to improve the realism of contamination release calculations in safety evaluations or emergency situations, and that of contamination transfers inside the facilities.
Project description and methodology
In the first two phases of the program, tests in a wind tunnel enabled the Cp coefficients to be evaluated on "reactor" and "laboratory and factory" scale models. The good results obtained from the comparison of the measured Cp's with those calculated by CFX means that predictive Cp calculations can be run for other geometries. The third phase, carried out in the framework of a thesis started at october 2008, involves wind tunnel tests to determine wind effects on a complex scale model of a facility with a ventilation network and accidental disturbances (ventilation stopped, gas emission, increase in temperature). These tests will also serve to qualify the SYLVIA software products system.