Expansion of a radial jet from a guillotine tube breach in a shell-and-tube heat exchanger

Aerodynamics of a particle-laden gas jet entering the secondary side of a shell-and-tube heat exchanger from a tube guillotine breach, determines to a large extent radioactive retention in the break stage of the steam generator (SG) during hypothetical SGTR accident sequences in pressurized nuclear water reactors (PWRs). These scenarios were shown to be risk-dominant in PWRs. The major insights gained from a set of experiments into such aerodynamics are summarized in this paper. A scaled-down mock-up with representative dimensions of a real SG was built. Two-dimensional (2D) PIV technique was used to characterize the flow field in the space between the breach and the neighbor tubes in the gas flow range investigated (ReD = 0.8–2.7 × 105). Pitot tube measurements and CFD simulations were used to discuss and complement PIV data. The results, reported mainly in terms of velocity and turbulent intensity profiles, show that jet penetration and gas entrainment are considerably enhanced when increasing ReD. The presence of tubes was observed to distort the jet shape and to foster gas entrainment with respect to a jet expansion free of tubes. Turbulence intensity level close to the breach increases linearly with ReD. Account of this information into aerosol modeling will enhance predictive capability of inertial impaction and turbulent deposition equations.