Steam generator tube rupture in lead-cooled fast reactors: Estimation of impact on neighboring tubes

Abstract

Abstract Lead-cooled fast reactors have several advantages in comparison to thermal neutron reactors and sodium-cooled fast reactors. Despite the considerable interest of international nuclear power community to this technology, safety issues associated with possible chain rupture of steam generator tubes initiated by rupture of a single tube in the tube bundle have not been completely resolved so far. Such initiating events can cause large dynamic loads on the neighboring tubes, and methods for evaluation of their consequences are to be developed. In this work, approaches are proposed for the estimation of forces acting on neighboring tubes at the initial stage of an accident initiated by tube rupture in a lead-heated steam generator. The forces considered include the shock impact caused by pressure wave propagating in liquid lead, and subsequent hydrodynamic impact caused by high-speed flow of heavy lead around the neighboring tubes. The shock impact is calculated from a model for water droplet evaporation and expansion in liquid lead based on the assumptions that two-phase water mixture is in thermodynamic and mechanical equilibrium, while liquid lead is an inviscid compressible fluid. The hydrodynamic impact is estimated using a simplified model with incompressible liquid lead and volume-averaged two-phase water-vapor mixture properties. Both models are implemented in 1D spherical coordinates. Estimates for the shock and hydrodynamic impact of tube rupture on the neighboring tubes are obtained for the conditions of BREST-OD-300 steam generator.