Practical engineering problems often involve free surface flows, large-strain elastoplasticity, structural damage and fracture, phase change, and collision between complex continua. Smoothed particle hydrodynamics (SPH) inherently avoids numerical errors caused by mesh distortion due to its Lagrangian nature, making it particularly appealing for the industrial applications. Key requirements for the practical use of SPH include numerical accuracy and stability, computational efficiency, and ease of implementation. To satisfy these demands, this study proposes a simplified Explicit Incompressible SPH (EISPH) combined with Total Lagrangian SPH (TLSPH) to simulate thermo-fluid-structure interaction (FSI) phenomena. EISPH adopts a first-order projection method [1]. An intermediate velocity is initially computed using non-pressure forces and subsequently corrected by including pressure forces. The flow pressure is obtained by explicitly solving the pressure Poisson equation, removing the necessity for the iterative Jacobi method. Furthermore, an implicit viscosity solver is adopted, allowing to efficiently treat highly-viscous fluids and fluid freezing by abrupt increase in viscosity. In TLSPH, the conservation laws are formulated based on a reference (undeformed) configuration. It has superior stability since the approximations are performed by Lagrangian kernels with a constant neighbor list, eliminating tensile instabilities completely. A hyperelastic-based approach is used as a constitutive model, enabling to treat pure elasticity as well as thermo-elastoplasticity [2]. Furthermore, an isotropic damage model based on fracture energy is adopted for accurate predictions of potential structural failures. A staggered time integrator is utilized to couple fluid and structure domains, along with fluid-structure interface models that accurately enforce kinematic and dynamic boundary conditions [3]. To demonstrate the capability of the proposed model in analyzing real-scale engineering problems, comprehensive safety and performance analyses are performed for an accident mitigation strategy under nuclear reactor meltdown scenarios. These analyses capture key physical phenomena, including free-surface flows of high-temperature, highly viscous lava-like fluids, along with large elastoplastic deformation, damage, and fracture of structural components.