Brookhaven Science Associates U.S. Department of Energy 1 Multi-Physics Simulation of Fuel Rod Failure during Accidents in Sodium Fast Reactors Roman Samulyak

Brookhaven Science AssociatesU.S. Department of Energy 1

Multi-Physics Simulation of Fuel Rod Failure during Accidents in Sodium Fast Reactors

Roman Samulyak

AMS Department, Stony Brook Universityand

Computational Science CenterBrookhaven 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)


23/4/19 NERI PROJECT NO. 08-033 2

Project ObjectivesProject Objectives

NERI consortium of Rensselaer Polytechnic Institute, Stony Brook University, Columbia University, and Brookhaven National Laboratory

The overall objective is to develop a multiple computer code platform for advanced multiscale/multiphysics simulations of Generation IV reactors

Apply proposed methodology to accident analysis for Sodium Fast Reactor (SFR)


Fuel degradation and transport in SFR during fuel rod failure accidents


23/4/19 NERI PROJECT NO. 08-033 4

Project Work Scope Project Work Scope MD simulations of reactor fuel

Multicomponent material (gas, solid, melt) distribution inside fuel elements and ejection through cladding breach

Cladding heatup and failure

Gas (volatile fission products) and fuel particle injection into liquid metal coolant

Multicomponent/multiphase fluid transport inside coolant channels

Computational issues: development, implementation and testing of higher order solution algorithms

Development of multiple-code computational platform for Blue Gene


Project OverviewProject 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

23/4/19 5NERI PROJECT NO. 08-033


Interaction between component-codesInteraction between component-codesDetermines 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

NPHASE-CMFD

PHASTAPHASTA

FronTierFronTier

Molecular Dynamics

Molecular Dynamics

fuel, , ,k Dρ φ

fission gas U, shape

of melted

cladding

U,k,ε,α

CU

Lin

ear

Solv

er

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)

FronTierdomain

MD

fission gas

P

P

04/19/23 6NERI PROJECT NO. 08-033


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 mesh2. An unstructured codimension-1

Lagrangian mesh to represent interface

Main Ideas of Front Tracking

Major components:1. Front propagation and redistribution2. Wave (smooth region) solution


• 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: 2DRight: 3D (fragment of the interface)


Role of FronTier Code in Fuel Rod SimulationsRole 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 rod2. 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

23/4/19 9NERI PROJECT NO. 08-033


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

04/19/23 10NERI PROJECT NO. 08-033


Calculations of normal operating conditions

Coolant

Cladding

Gas gap

Fuel

€

ΔTSurface

€

ΔTFuel

€

TCenter€

ΔTGap

€

ΔTClad

• 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

04/19/23 11NERI PROJECT NO. 08-033


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)

04/19/23 12NERI PROJECT NO. 08-033


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

04/19/23 13NERI PROJECT NO. 08-033


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

04/19/23 14NERI PROJECT NO. 08-033


04/19/23 NERI PROJECT NO. XX-XXX 15

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


Ejection of the gas jet into sodium poolEjection of the gas jet into sodium pool

PHASTA simulation

04/19/23 16

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are needed to see this picture.

FronTier simulation


PHASTA/NPHASE LinkPHASTA/NPHASE Link

High Rek-ε model

Low Rek-ε model

Channel flow DNS at Reτ = 180, Rehd = 11,200

17NERI PROJECT NO. 08-03304/19/23


23/4/19 18

Simulation of processes in materials at extreme conditions in other energy applications


• 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 D2 pellets

Our contribution to ITER science:


• 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


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

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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


New Ideas in Nuclear Fusion: MTF

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Mercury Jet Target for Neutrino Factory / Muon Collider

Jet disruptionsTop: experiment Bottom: simulationTarget 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

Documents

Brookhaven Science Associates U.S. Department of Energy 1 Multi-Physics Simulation of Fuel Rod Failure during Accidents in Sodium Fast Reactors Roman Samulyak