Analysis Of Flow Field And Debris Transport Fraction In Containment Sump

Containment as the last barrier in the nuclear power plant is designed to preventradioactivity products escape to the environment. The containment sump’s function is tocollect the coolant from pipe break and containment spray after the accident. Under loss ofcoolant accident (LOCA) or main steam line break (MSLB) accident scenario, thecontainment sump serves as the source of the emergency cooling core system (ECCS) andcontainment spray system (CSS) to provide the circulating cooling water for reactor’slong-team cooling. If LOCA or MLSB accident happens, there will be abundant of insulationfibers and debris, as well as a mass of high-speed coolant coming out from the break on thepipe line. Once recirculation signal is activated after LOCA, ECCS and spray flow is drawnfrom the recirculation sump, various insulations and coatings on pipe, equipment andstructures are transported to emergency recirculation sump by the break flow and spray flowdrainage. However, more debris will be accumulated on the strainer, and thus consequentlyreduce the filter area. The net positive suction head (NPSH) required by recirculation pumpswill be decreased and consequently the ECCS and CSS will have the risk that may not be ableto provide sufficient cooling water to the reactor core and remove decay heat.Pro/E software is used to build up three dimensional geometry of the containment. Therecirculation zone is well meshed with ICEM. The computational fluid dynamic softwareFluent is used to simulate the flowing characteristics of the recirculation cooling water incontainment sump under LOCA scenario. The performance and effects of interception baffleare also studied thoroughly through the comparison between two simulation results with andwithout interception baffle inside containment sump.In order to conservatively estimate the quantity of debris that could arrive at thestrainer(s) in the recirculation term, the velocity fields, the kinetic energy fields and the waterstreamline from the CFD simulation results are coupled together with debris-transportmechanism.Finally, new type interception baffle structure is designed and improved base on theprototype. CFD method is used to evaluate the properties of the new type interception baffleunder different structure, and then the optimum structure is recommended.