problem: !SequentialCoupling
  description: Test12 - demonstration of unstability of reaction solver without CFL condition (exact solution (50+5*exp(-55*t))/55)
  mesh:
    mesh_file: ./input/sit_decay.msh
  primary_equation: !Unsteady_MH
    output_specific:
    input_fields:
      - r_set: BOUNDARY
        bc_type:  # :dirichlet  # Select either 'robin' or 'neumann' according to the value of 'bc_flux', 'bc_pressure', 'bc_sigma'.
        bc_piezo_head: 0
    output:
      output_stream:
        file: ./decay.pvd
        format: !vtk
          variant: ascii
        name: flow_output_stream
      output_fields:
        - pressure_p0
        - pressure_p1
        - velocity_p0
    balance: true
    solver: !Petsc
      a_tol: 1.0e-07
  secondary_equation: !TransportOperatorSplitting
    input_fields:
      - rid: 1
        init_conc:
          - 1
          - 0
      - r_set: BOUNDARY
        bc_conc:
          - 1
          - 0
    output_stream:
      file: ./transport_decay.pvd
      format: !vtk
        variant: ascii
      time_step: 2e+0
    substances:
      - A
      - B
    time:
      end_time: 10.0
    reaction_term: !RadioactiveDecay
      decays:
        - radionuclide: A
          half_life: 1.38e-1 # ~ ln(2)/5 -> k=5
          products: B
        - radionuclide: B
          half_life: 1.38e-2 # ~ ln(2)/50 -> k=50
          products: A
    balance:
      cumulative: true
