1. Brookhaven Science Associates U.S. Department of Energy 1 Multi-Physics Simulation of Fuel Rod Failure during Accidents in Sodium Fast Reactors Roman Samulyak AMS Department, Stony Brook University and Computational Science Center Brookhaven National Laboratory Collaborators: Michael Podowski, Ken Jansen (RPI), Lap Cheng (BNL) James Glimm, Xiaolin Li, Shuqiang Wang, Lingling Wu (Stony Brook) Paul Parks (General Atomics)

2. Brookhaven Science Associates U.S. Department of Energy 2 2015-8-14NERI PROJECT NO. 08-0332 Project Objectives n NERI consortium of Rensselaer Polytechnic Institute, Stony Brook University, Columbia University, and Brookhaven National Laboratory n The overall objective is to develop a multiple computer code platform for advanced multiscale/multiphysics simulations of Generation IV reactors n Apply proposed methodology to accident analysis for Sodium Fast Reactor (SFR)

3. Brookhaven Science Associates U.S. Department of Energy 3 Fuel degradation and transport in SFR during fuel rod failure accidents

4. Brookhaven Science Associates U.S. Department of Energy 4 2015-8-14NERI PROJECT NO. 08-0334 Project Work Scope n MD simulations of reactor fuel n Multicomponent material (gas, solid, melt) distribution inside fuel elements and ejection through cladding breach n Cladding heatup and failure n Gas (volatile fission products) and fuel particle injection into liquid metal coolant n Multicomponent/multiphase fluid transport inside coolant channels n Computational issues: development, implementation and testing of higher order solution algorithms n Development of multiple-code computational platform for Blue Gene

5. Brookhaven Science Associates U.S. Department of Energy 5 Project Overview NPHASE-CMFD code uses Reynolds-Averaged Navier Stokes (RANS, e.g. k-ε model) approach to multiphase modeling Flow of liquid sodium coolant and fission gas around l reactor fuel rods PHASTA uses direct numerical simulation (DNS) with Level Set method to track the interface between gas and liquid phases Jet of high pressure fission gas entering coolant channels FronTier is a front tracking code capable of simulating multiphase compressible fluid dynamics Fuel rod overheating and melting of cladding in case of coolant-blockage accident Molecular Dynamics approach analyses the irradiated fuel properties Prediction of fuel properties evolution 2015-8-145NERI PROJECT NO. 08-033

6. Brookhaven Science Associates U.S. Department of Energy 6 Interaction between component-codes Determines the effects on the reactor fuel due to thermal loads and provides temperature- and irradiation-dependent thermal conductivity, density, effective porosity of fragmented/fractured fuel, diffusive properties of irradiated fuel Simulates the fuel rod heating and melting of stainless steel cladding. Computes the fission gas properties and escape velocity during the meltdown as well as the shape of the damaged cladding Performs a two-phase direct numerical simulation of fission gas jet entering the liquid sodium coolant. The fluctuating velocity field is post-processed to provide the two-phase flow turbulence parameters downstream of fuel rod: mean velocity, turbulent kinetic energy, turbulence dissipation rate and gas volume fraction Performs a multiphase RANS simulation of a coolant flow during the accident scenario around several fuel rods using the detailed information provided by PHASTA and FronTier NPHASE-CMFD PHASTA FronTier Molecular Dynamics fuel fission gas U, shape of melted cladding U,k,ε,α CU Linear Solver Improves the ability of NPHASE, PHASTA and FronTier to solve large systems of linear equation in parallel environments coolant PHASTA domain (DNS) NPHASE domain (RANS) FronTier domain MD fission gas P P 8/14/20156NERI PROJECT NO. 08-033

7. Brookhaven Science Associates U.S. Department of Energy 7 Front Tracking: A hybrid of Eulerian and Lagrangian methods Advantages of explicit interface tracking: No numerical interfacial diffusion Real physics models for interface propagation Different physics / numerical approximations in domains separated by interfaces Two separate grids to describe the solution: 1.A volume filling rectangular mesh 2.An unstructured codimension-1 Lagrangian mesh to represent interface Main Ideas of Front Tracking Major components: 1.Front propagation and redistribution 2.Wave (smooth region) solution

8. Brookhaven Science Associates U.S. Department of Energy 8 FronTier is a parallel 3D multiphysics code based on front tracking Being developed within DOE SciDAC program Adaptive mesh refinement Physics models include Compressible fluid dynamics, MHD Flows in porous media Phase transitions and turbulence models The FronTier Code Turbulent fluid mixing. Left: 2D Right: 3D (fragment of the interface)

9. Brookhaven Science Associates U.S. Department of Energy 9 Role of FronTier Code in Fuel Rod Simulations  Using material data from MD, simulate overheating scenarios in nuclear fuel rods and predict the shape and size of cracks in the steel clad and the fission gas and melted fuel flow into the coolant reservoir. Provide input to the PHASTA code.  Research tasks of the FronTier team: 1.Develop new algorithms for the phase transition (melting and vaporization) in the nuclear fuel rod 2.Develop algorithms for the crack formation and failure of solid materials 3.Perform simulations of the fuel rod failure and provide input to the PHASTA code 2015-8-149NERI PROJECT NO. 08-033

10. Brookhaven Science Associates U.S. Department of Energy 10  Developed Embedded Boundary Elliptic Interface method for the heat transfer problem in nuclear fuel rods  Implemented and fully tested front-tracking-based solver of Stefan problem in FronTier  Applied the new solver to the phase transition problem in fuel rods (fuel and clad melting)  Developed algorithms for dynamic creation of boiling/vaporization nucleation centers in regions that exceed critical conditions New Phase Transition Algorithms for FronTier 8/14/201510NERI PROJECT NO. 08-033

11. Brookhaven Science Associates U.S. Department of Energy 11 Calculations of normal operating conditions Coolant Cladding Gas gap Fuel Performed calculations of normal operating conditions for metallic and oxide fuels Assumed empirical models for effective heat transfer coefficients in the gas gap and turbulent fuel flow Ideal (top) and real gas gap 8/14/201511NERI PROJECT NO. 08-033

12. Brookhaven Science Associates U.S. Department of Energy 12 Simulation of fuel rod melting  Performed calculations of the heat transfer and phase transitions (melting) in a nuclear fuel rod at Increased power production rate (transient overheating accident) Increasing coolant temperature (loss of coolant accident) 8/14/201512NERI PROJECT NO. 08-033

13. Brookhaven Science Associates U.S. Department of Energy 13 Development of mesoscale solid failure models for FronTier Finite element meshes conforming to interfaces of solid structures The medium is represented by a network of nodes connected by bonds satisfying some stress - strain relation Bonds are present with the probability p. The probability of initial defect is p-1 The process consists of the energy minimization and sequential breaking of bonds which exceed the critical stress threshold 8/14/201513NERI PROJECT NO. 08-033

14. Brookhaven Science Associates U.S. Department of Energy 14 Fuel clad failure Performed simulations of the failure of cladding The failure was caused by the increased pressure and fuel rod deformation. Thermal changes of clad properties were ignored Future work will focus on the implementation of more realistic stress-strain relations for bonds that include the plastic region and thermal changes of material properties 8/14/201514NERI PROJECT NO. 08-033

15. Brookhaven Science Associates U.S. Department of Energy 15 8/14/2015NERI PROJECT NO. XX-XXX15 Fission Gas Flow from Plenum to Sodium Pool  At the time of clad failure, fission gas transport inside fuel pin is first modeled using flow in porous medium equations  Then, FronTier calculations are performed to simulate pressure-driven ejection through cracked cladding wall of multiphase/ multicomponent mixture of fission gasses and molten/solid fuel into reactor coolant channel

16. Brookhaven Science Associates U.S. Department of Energy 16 Ejection of the gas jet into sodium pool PHASTA simulation 8/14/201516 FronTier simulation

17. Brookhaven Science Associates U.S. Department of Energy 17 PHASTA/NPHASE Link High Re k-ε model Low Re k-ε model Channel flow DNS at Re τ = 180, Re hd = 11,200 17NERI PROJECT NO. 08-0338/14/2015

18. Brookhaven Science Associates U.S. Department of Energy 18 2015-8-1418 Simulation of processes in materials at extreme conditions in other energy applications

19. Brookhaven Science Associates U.S. Department of Energy 19 ITER is a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power ITER will be constructed in Europe, at Cadarache in the South of France in ~10 years ITER Fueling by Pellet Injection Models and simulations of tokamak fueling through the ablation of frozen D 2 pellets Our contribution to ITER science:

20. Brookhaven Science Associates U.S. Department of Energy 20 ITAPS Front tracking was used for first systematic “microscale” MHD studies of pellet ablation physics Simulations revealed new propertied of the ablation flow: Supersonic rotation of the ablation channel Resolution of this phenomenon greatly improves the agreement with experiments Strong dependence of the ablation rate on plasma pedestal properties Simulations suggested that novel pellet acceleration technique (laser or gyrotron driven) are necessary for ITER Main results of ITER fuelling simulations Isosurfaces of the rotational Mach number in the pellet ablation flow

21. Brookhaven Science Associates U.S. Department of Energy 21 Striation instabilities: Experimental observation (Courtesy MIT Fusion Group) Current work focuses on the study of striation instabilities Striation instabilities, observed in all experiments, are not well understood We believe that the key process causing striation instabilities is the supersonic channel rotation, observed in our simulations Work in Progress

22. Brookhaven Science Associates U.S. Department of Energy 22 Inertial Confinement Fusion National Ignition Facility Construction started in 1997 Official opening ceremony: May 29, 2009 500 Terawatt flash of light within a few picoseconds 192 laser beams focused on the target

23. Brookhaven Science Associates U.S. Department of Energy 23 New Ideas in Nuclear Fusion: MTF

24. Brookhaven Science Associates U.S. Department of Energy 24 Mercury Jet Target for Neutrino Factory / Muon Collider Jet disruptions Top: experiment Bottom: simulation Target schematic Target is a mercury jet interacting with a proton pulse in a magnetic field Target converts protons to pions that decay to muons and neutrinos or to neutrons (accelerator based neutron sources) Understanding of the target hydrodynamic response is critical for design Studies of surface instabilities, jet breakup, and cavitation MHD forces reduce both jet expansion, instabilities, and cavitation