ARTIST, AeRosol Trapping In the Steam generaTor

Aerosol Trapping In a Steam Generator (ARTIST) was an international project to investigate aerosol and droplet retention in a model steam generator. The project was carried out in two phases, ARTIST in 2003-2007, and ARTIST-II in 2009-2011. More than 20 partners from 10 countries participated in the two phases of the project. In the ARTIST and ARTIST II projects, aerosol retention in the steam generator was investigated during steam generator tube rupture incidents under severe accident conditions. Aerosol retention in the steam generator was investigated by: i) integral experiments for aerosol retention in the ARTIST facility, ii) separate effect tests, iii) analytical work to determine the boundary conditions for SGTR events, and, additionally, iv) model development to address aerosol retention in the steam generator under both dry and flooded secondary side conditions. In addition to aerosol retention, in one experimental set-up droplet retention in the separator and dryer sections under dry conditions was determined. This set-up dealt with Design Basis Accident (DBA) phenomena, i.e. the potential for “primary bypass”, whereby a break at the top of the tube bundle sprays fine primary liquid droplets that might find their way to the environment through, for example, a stuck-open safety valve.

Based on ARTIST and ARTIST II projects we conclude that a considerable fraction of the aerosols are deposited in the steam generator, and that the release to the environment is significantly smaller than previously estimated. The main results can be summarized as following:
  • Significant aerosol retention takes place in the steam generator. Even in the dry secondary side, aerosols are efficiently deposited and retained. Most of the aerosol retention takes place relatively close to the break in the high velocity region of the tube bundle. The aerosol particle size and the gas flow rate through the break are the main factors determining the magnitude of retention. Break geometry also influences the retention, but the dependence is not straightforward. Models have been developed to calculate the retention, but further work is needed to be able to capture all the factors affecting the retention. Particle bounce and resuspension from the surfaces play a critical role on particle retention in the dry secondary side and these two phenomena are not included in generally used severe accident codes
  • The presence of water in the secondary side of the failed steam generator is one of the most im-portant factors influencing the retention of aerosol particles carried by the incoming gas. Even at low submergence of the break, very small particle release from the flooded secondary side was experimentally determined. The particle inertia, i.e., break flow rate and particle size, is the main factor determining the efficiency of aerosol retention. The interaction of the flow and aerosols with the U-tube bundle structures was found to be of significant importance for aerosol retention, as the aerosol retention in the flooded secondary side of a steam generator is much higher than in bare pools. Existing models for bare pools were found not to be able to capture all the phenomena involved.

Publications


Key Findings from the Artist Project on Aerosol Retention in a Dry Steam Generator