PROBLEM neutron_diffusion DIM 1 GROUPS 2 MESH reflected.msh

MATERIAL fuel {
  D1=1.5
  D2=0.4
  Sigma_s1.2=0.02
  Sigma_a1=0.01
  Sigma_a2=0.08
  S1=0.05
}

MATERIAL left_refl {
  D1=2.0
  D2=0.3
  Sigma_s1.2=0.04
  Sigma_a1=0.00
  Sigma_a2=0.01
}

MATERIAL right_refl {
  D1=2.0
  D2=0.3
  Sigma_s1.2=0.05
  Sigma_a1=0.00
  Sigma_a2=0.005
}

BC left null
BC right null

SOLVE_PROBLEM 

PRINT %.4f phi1(100) phi2(100) SEP " "