A robust multi phase model to investigate molten material relocation during total flow blockage in SFR fuel subassembly. (November 2019)

• Record Type: Journal Article
• Authors: Panigrahi, Prasant Kumar; Velusamy, K.
• Is Part Of: Annals of nuclear energy. Volume 133(2019)
• Page Start: 59
• Page End: 72
• Publication Date: 2019-11
• Subjects: Sodium-cooled fast reactor -- Flow blockage -- Multi-phase model -- Enthalpy formulation -- Subassembly -- Freezing; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2019.05.007
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: A robust multi-phase thermal hydraulic model for molten fuel relocation is developed. Movement of molten fuel in a sodium cooled fast reactor subassembly is analysed. Penetration length of melt front in sub-channels of fuel subassembly is determined. Amount of fuel relocated out of core before melt front freezing is quantified. Design measures to enhance fuel relocation to the core catcher are proposed. Abstract: A transient, multi-phase enthalpy based computational model is developed to analyse the streaming and freezing characteristics of the molten fuel in a blocked fuel subassembly (SA) during Total Flow Blockage (TFB) at the foot of the SA. During TFB accident progression, a molten material pool is formed following the meltdown of fuel pins. The molten fuel has the potential to relocate axially through the available subchannels in the downward direction. The mathematical model comprises of two modules; a Fluid Dynamics module and a Heat Transfer module. The model adopts both implicit and explicit type of finite difference techniques employing a variable grid system for boundary tracking. The mathematical model has been validated against benchmark experimental data and SIMMER III code prediction reported in open literature. The developed model is employed to simulate the relocation of molten fuel in a prototype fast reactor fuel SA under accident condition. The simulation results indicate that the molten fuel is unable to penetrate the axial blankets in fuel SA without freezing and forming a blockage mainly owing to the rapid freezing of melt. Further, a parametric analysis is carried out to ascertain the influence of critical parameters on the relocation and freezing characteristics. It is observed that the design of the fuel SA has a potential effect on the streaming behaviour and enhancement in fuel relocation is substantially achieved by dwindling the fuel pin size, especially axial length and diameter of the pin, thus preventing the accident progression to the neighbouring SAs.