NtAction

note

This action sets up ONLY the variables, kernels, and BCs for neutron diffusion, NOT the variables, kernels, and BCs for precursor tracking. To generate these, see PrecursorAction.

Overview

NtAction greatly reduces input file length and complexity by automatically setting up variables, kernels, and BCs for the neutron diffusion equations. When including only the required input parameters, this action constructs the neutron group variables and their associated kernels: SigmaR, GroupDiffusion, InScatter, and CoupledFissionKernel. With account_delayed set to True, DelayedNeutronSource is also constructed, otherwise this kernel is not constructed and the simulation does not consider the delayed neutron precursor effects on the neutron flux distributions.

For more information regarding the use of NtAction please refer to the tutorials located here, specifically the Multiphysics Reactor Simulations section.

Example Input File Syntax

An example input file without the NtAction, showing only the portion affected by the action:

[Variables]
  [group1]
    order = FIRST
    family = LAGRANGE
  []
  [group2]
    order = FIRST
    family = LAGRANGE
  []
[]

[Kernels]
  #---------------------------------------------------------------------
  # Group 1 Neutronics
  #---------------------------------------------------------------------
  [sigma_r_group1]
    type = SigmaR
    variable = group1
    group_number = 1
  []
  [diff_group1]
    type = GroupDiffusion
    variable = group1
    group_number = 1
  []
  [inscatter_group1]
    type = InScatter
    variable = group1
    group_number = 1
  []
  [fission_source_group1]
    type = CoupledFissionKernel
    variable = group1
    group_number = 1
    block = '0'
    extra_vector_tags = 'eigen'
  []
  [delayed_group1]
    type = DelayedNeutronSource
    variable = group1
    block = '0'
    group_number = 1
  []

  #---------------------------------------------------------------------
  # Group 2 Neutronics
  #---------------------------------------------------------------------
  [sigma_r_group2]
    type = SigmaR
    variable = group2
    group_number = 2
  []
  [diff_group2]
    type = GroupDiffusion
    variable = group2
    group_number = 2
  []
  [fission_source_group2]
    type = CoupledFissionKernel
    variable = group2
    group_number = 2
    block = '0'
    extra_vector_tags = 'eigen'
  []
  [inscatter_group2]
    type = InScatter
    variable = group2
    group_number = 2
  []
[]

[BCs]
  [vacuum_group1]
    type = VacuumConcBC
    boundary = 'fuel_bottom fuel_top mod_bottom mod_top right'
    variable = group1
  []
  [vacuum_group2]
    type = VacuumConcBC
    boundary = 'fuel_bottom fuel_top mod_bottom mod_top right'
    variable = group2
  []
[]

And then the same information created with the NtAction:

[Nt]
  var_name_base = group
  vacuum_boundaries = 'fuel_bottom mod_bottom right fuel_top mod_top'
  pre_blocks = '0'
  create_temperature_var = false
  eigen = true
[]

Input Parameters

account_delayedFalseWhether to account for delayed neutrons.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether to account for delayed neutrons.
num_groupsThe total number of energy groups.
C++ Type:unsigned int
Unit:(no unit assumed)
Controllable:No
Description:The total number of energy groups.
num_precursor_groupsspecifies the total number of precursors to create
C++ Type:unsigned int
Unit:(no unit assumed)
Controllable:No
Description:specifies the total number of precursors to create
sss2_inputFalseWhether the input follows sss2 form scattering matrices.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether the input follows sss2 form scattering matrices.
temperatureName of temperature variable
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Name of temperature variable
use_exp_formFalseWhether concentrations should be in an exponential/logarithmic format.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether concentrations should be in an exponential/logarithmic format.
var_name_basespecifies the base name of the variables
C++ Type:std::string
Unit:(no unit assumed)
Controllable:No
Description:specifies the base name of the variables

Required Parameters

active__all__ If specified only the blocks named will be visited and made active
Default:__all__
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:If specified only the blocks named will be visited and made active
blockThe block id where this variable lives
C++ Type:std::vector<SubdomainName>
Unit:(no unit assumed)
Controllable:No
Description:The block id where this variable lives
create_temperature_varTrueWhether to create the temperature variable.
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether to create the temperature variable.
dg_for_temperatureTrueWhether the temperature variable should use discontinuous basis functions.
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether the temperature variable should use discontinuous basis functions.
eigenFalseWhether to run an eigen- instead of a transient- simulation.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether to run an eigen- instead of a transient- simulation.
eigenvalue_scaling1Artificial scaling factor for the fission source. Primarily for introducing artificial reactivity to make super/subcritical systems exactly critical or to simulate reactivity insertions/withdrawals.
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Artificial scaling factor for the fission source. Primarily for introducing artificial reactivity to make super/subcritical systems exactly critical or to simulate reactivity insertions/withdrawals.
familyLAGRANGESpecifies the family of FE shape functions to use for this variable
Default:LAGRANGE
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:LAGRANGE, MONOMIAL, HERMITE, SCALAR, HIERARCHIC, CLOUGH, XYZ, SZABAB, BERNSTEIN, L2_LAGRANGE, L2_HIERARCHIC, NEDELEC_ONE, LAGRANGE_VEC, MONOMIAL_VEC, RAVIART_THOMAS, RATIONAL_BERNSTEIN, SIDE_HIERARCHIC, L2_HIERARCHIC_VEC, L2_LAGRANGE_VEC, L2_RAVIART_THOMAS
Controllable:No
Description:Specifies the family of FE shape functions to use for this variable
inactiveIf specified blocks matching these identifiers will be skipped.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:If specified blocks matching these identifiers will be skipped.
init_nts_from_fileFalseWhether to restart simulation using nt output from a previous simulation.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether to restart simulation using nt output from a previous simulation.
init_temperature_from_fileFalseWhether to restart simulation using temperature output from a previous simulation.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether to restart simulation using temperature output from a previous simulation.
jac_testFalseWhether we're testing the Jacobian and should use some random initial conditions for the precursors.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether we're testing the Jacobian and should use some random initial conditions for the precursors.
nt_ic_functionAn initial condition function for the neutrons.
C++ Type:FunctionName
Unit:(no unit assumed)
Controllable:No
Description:An initial condition function for the neutrons.
orderFIRSTSpecifies the order of the FE shape function to use for this variable (additional orders not listed are allowed)
Default:FIRST
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:CONSTANT, FIRST, SECOND, THIRD, FOURTH
Controllable:No
Description:Specifies the order of the FE shape function to use for this variable (additional orders not listed are allowed)
pre_blocksThe blocks the precursors live on.
C++ Type:std::vector<SubdomainName>
Unit:(no unit assumed)
Controllable:No
Description:The blocks the precursors live on.
pre_concsAll the variables that hold the precursor concentrations. These MUST be listed by increasing group number.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:All the variables that hold the precursor concentrations. These MUST be listed by increasing group number.
scaling1Specifies a scaling factor to apply to this variable
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Specifies a scaling factor to apply to this variable
temp_scalingThe amount by which to scale the temperature variable.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The amount by which to scale the temperature variable.
vacuum_bc_typemarshakWhether to apply Marshak, Mark, or Milne vacuum boundary conditions. Defaults to Marshak.
Default:marshak
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:marshak, mark, milne
Controllable:No
Description:Whether to apply Marshak, Mark, or Milne vacuum boundary conditions. Defaults to Marshak.
vacuum_boundariesThe boundaries on which to apply vacuum boundaries.
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:The boundaries on which to apply vacuum boundaries.

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.

Advanced Parameters

(tutorial/eigenvalue/nts.i)

[GlobalParams]
  num_groups = 2
  num_precursor_groups = 6
  use_exp_form = false
  group_fluxes = 'group1 group2'
  pre_concs = 'pre1 pre2 pre3 pre4 pre5 pre6'
  temperature = 900
  sss2_input = true
  account_delayed = true
[]

[Mesh]
  coord_type = RZ
  [mesh]
    type = FileMeshGenerator
    file = 'mesh.e'
  []
[]

[Problem]
  type = EigenProblem
  bx_norm = bnorm
[]

[Variables]
  [group1]
    order = FIRST
    family = LAGRANGE
  []
  [group2]
    order = FIRST
    family = LAGRANGE
  []
[]

[Precursors]
  [pres]
    var_name_base = pre
    family = MONOMIAL
    order = CONSTANT
    block = 0
    outlet_boundaries = 'fuel_top'
    constant_velocity_values = true
    u_def = 0
    v_def = 18.085
    w_def = 0
    nt_exp_form = false
    loop_precursors = false
    transient = false
    eigen = true
  []
[]

[Kernels]
  #---------------------------------------------------------------------
  # Group 1 Neutronics
  #---------------------------------------------------------------------
  [sigma_r_group1]
    type = SigmaR
    variable = group1
    group_number = 1
  []
  [diff_group1]
    type = GroupDiffusion
    variable = group1
    group_number = 1
  []
  [inscatter_group1]
    type = InScatter
    variable = group1
    group_number = 1
  []
  [fission_source_group1]
    type = CoupledFissionKernel
    variable = group1
    group_number = 1
    block = '0'
    extra_vector_tags = 'eigen'
  []
  [delayed_group1]
    type = DelayedNeutronSource
    variable = group1
    block = '0'
    group_number = 1
  []

  #---------------------------------------------------------------------
  # Group 2 Neutronics
  #---------------------------------------------------------------------
  [sigma_r_group2]
    type = SigmaR
    variable = group2
    group_number = 2
  []
  [diff_group2]
    type = GroupDiffusion
    variable = group2
    group_number = 2
  []
  [fission_source_group2]
    type = CoupledFissionKernel
    variable = group2
    group_number = 2
    block = '0'
    extra_vector_tags = 'eigen'
  []
  [inscatter_group2]
    type = InScatter
    variable = group2
    group_number = 2
  []
[]

[BCs]
  [vacuum_group1]
    type = VacuumConcBC
    boundary = 'fuel_bottom fuel_top mod_bottom mod_top right'
    variable = group1
  []
  [vacuum_group2]
    type = VacuumConcBC
    boundary = 'fuel_bottom fuel_top mod_bottom mod_top right'
    variable = group2
  []
[]

[Materials]
  [fuel]
    type = MoltresJsonMaterial
    block = '0'
    base_file = 'xsdata.json'
    material_key = 'fuel'
    interp_type = LINEAR
    prop_names = ''
    prop_values = ''
  []
  [graphite]
    type = MoltresJsonMaterial
    block = '1'
    base_file = 'xsdata.json'
    material_key = 'graphite'
    interp_type = LINEAR
    prop_names = ''
    prop_values = ''
  []
[]

[Executioner]
  type = Eigenvalue
  initial_eigenvalue = 1
  solve_type = 'PJFNK'
  petsc_options = '-snes_converged_reason -ksp_converged_reason -snes_linesearch_monitor'
  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'

  automatic_scaling = true
  compute_scaling_once = false
  resid_vs_jac_scaling_param = 0.1

  line_search = none
[]

[Postprocessors]
  [k_eff]
    type = VectorPostprocessorComponent
    index = 0
    vectorpostprocessor = k_vpp
    vector_name = eigen_values_real
  []
  [bnorm]
    type = ElmIntegTotFissNtsPostprocessor
    block = 0
    execute_on = linear
  []
  [tot_fissions]
    type = ElmIntegTotFissPostprocessor
    execute_on = linear
  []
  [powernorm]
    type = ElmIntegTotFissHeatPostprocessor
    execute_on = linear
  []
  [group1norm]
    type = ElementIntegralVariablePostprocessor
    variable = group1
    execute_on = linear
  []
  [group1max]
    type = NodalExtremeValue
    value_type = max
    variable = group1
    execute_on = timestep_end
  []
  [group1diff]
    type = ElementL2Diff
    variable = group1
    execute_on = 'linear timestep_end'
    use_displaced_mesh = false
  []
  [group2norm]
    type = ElementIntegralVariablePostprocessor
    variable = group2
    execute_on = linear
  []
  [group2max]
    type = NodalExtremeValue
    value_type = max
    variable = group2
    execute_on = timestep_end
  []
  [group2diff]
    type = ElementL2Diff
    variable = group2
    execute_on = 'linear timestep_end'
    use_displaced_mesh = false
  []
[]

[VectorPostprocessors]
  [k_vpp]
    type = Eigenvalues
    inverse_eigenvalue = true
  []
  [centerline_flux]
    type = LineValueSampler
    variable = 'group1 group2'
    start_point = '0 0 0'
    end_point = '0 150 0'
    num_points = 151
    sort_by = y
    execute_on = FINAL
  []
  [midplane_flux]
    type = LineValueSampler
    variable = 'group1 group2'
    start_point = '0 75 0'
    end_point = '69.375 75 0'
    num_points = 100
    sort_by = x
    execute_on = FINAL
  []
[]

[Outputs]
  perf_graph = true
  print_linear_residuals = true
  [exodus]
    type = Exodus
  []
  [csv]
    type = CSV
  []
[]

(tutorial/eigenvalue/nts-action.i)

[GlobalParams]
  num_groups = 2
  num_precursor_groups = 6
  use_exp_form = false
  group_fluxes = 'group1 group2'
  pre_concs = 'pre1 pre2 pre3 pre4 pre5 pre6'
  temperature = 900
  sss2_input = true
  account_delayed = true
[]

[Mesh]
  coord_type = RZ
  [mesh]
    type = FileMeshGenerator
    file = 'mesh.e'
  []
[]

[Problem]
  type = EigenProblem
  bx_norm = bnorm
[]

[Nt]
  var_name_base = group
  vacuum_boundaries = 'fuel_bottom mod_bottom right fuel_top mod_top'
  pre_blocks = '0'
  create_temperature_var = false
  eigen = true
[]

[Precursors]
  [pres]
    var_name_base = pre
    family = MONOMIAL
    order = CONSTANT
    block = 0
    outlet_boundaries = 'fuel_top'
    constant_velocity_values = true
    u_def = 0
    v_def = 18.085
    w_def = 0
    nt_exp_form = false
    loop_precursors = false
    transient = false
    eigen = true
  []
[]

[Materials]
  [fuel]
    type = MoltresJsonMaterial
    block = '0'
    base_file = 'xsdata.json'
    material_key = 'fuel'
    interp_type = LINEAR
    prop_names = ''
    prop_values = ''
  []
  [graphite]
    type = MoltresJsonMaterial
    block = '1'
    base_file = 'xsdata.json'
    material_key = 'graphite'
    interp_type = LINEAR
    prop_names = ''
    prop_values = ''
  []
[]

[Executioner]
  type = Eigenvalue
  initial_eigenvalue = 1
  solve_type = 'PJFNK'
  petsc_options = '-snes_converged_reason -ksp_converged_reason -snes_linesearch_monitor'
  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'

  automatic_scaling = true
  compute_scaling_once = false
  resid_vs_jac_scaling_param = 0.1

  line_search = none
[]

[Postprocessors]
  [k_eff]
    type = VectorPostprocessorComponent
    index = 0
    vectorpostprocessor = k_vpp
    vector_name = eigen_values_real
  []
  [bnorm]
    type = ElmIntegTotFissNtsPostprocessor
    block = 0
    execute_on = linear
  []
  [tot_fissions]
    type = ElmIntegTotFissPostprocessor
    execute_on = linear
  []
  [powernorm]
    type = ElmIntegTotFissHeatPostprocessor
    execute_on = linear
  []
  [group1norm]
    type = ElementIntegralVariablePostprocessor
    variable = group1
    execute_on = linear
  []
  [group1max]
    type = NodalExtremeValue
    value_type = max
    variable = group1
    execute_on = timestep_end
  []
  [group1diff]
    type = ElementL2Diff
    variable = group1
    execute_on = 'linear timestep_end'
    use_displaced_mesh = false
  []
  [group2norm]
    type = ElementIntegralVariablePostprocessor
    variable = group2
    execute_on = linear
  []
  [group2max]
    type = NodalExtremeValue
    value_type = max
    variable = group2
    execute_on = timestep_end
  []
  [group2diff]
    type = ElementL2Diff
    variable = group2
    execute_on = 'linear timestep_end'
    use_displaced_mesh = false
  []
[]

[VectorPostprocessors]
  [k_vpp]
    type = Eigenvalues
    inverse_eigenvalue = true
  []
  [centerline_flux]
    type = LineValueSampler
    variable = 'group1 group2'
    start_point = '0 0 0'
    end_point = '0 150 0'
    num_points = 151
    sort_by = y
    execute_on = FINAL
  []
  [midplane_flux]
    type = LineValueSampler
    variable = 'group1 group2'
    start_point = '0 75 0'
    end_point = '69.375 75 0'
    num_points = 100
    sort_by = x
    execute_on = FINAL
  []
[]

[Outputs]
  perf_graph = true
  print_linear_residuals = true
  [exodus]
    type = Exodus
  []
  [csv]
    type = CSV
  []
[]

Overview
Example Input File Syntax
Input Parameters