Monte Carlo Fundamentals

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Cross-Code Reference (Rosetta Stone)

When switching between Monte Carlo codes, equivalent concepts often use different syntax. This page maps common operations across MCNP, OpenMC, Serpent, and SCONE so you can translate input decks and Python scripts quickly.

For a searchable, filterable version with 15+ concepts, try the Interactive Rosetta Stone — pick a concept and see all four codes side by side.

UO₂ Fuel Material (4.5% enriched)

Defining UO₂ at 10.96 g/cm³ with 4.5 wt% U-235. Negative density in MCNP/Serpent = g/cm³. SCONE uses atomic densities in atoms/(cm·barn).

MCNP

text
m1  92235.80c  -0.045   92238.80c  -0.955
    8016.80c   -2.0
     den=-10.96

OpenMC (Python)

python
uo2 = openmc.Material(material_id=1, name='UO2')
uo2.add_nuclide('U235', 0.045)
uo2.add_nuclide('U238', 0.955)
uo2.add_element('O', 2.0)
uo2.set_density('g/cm3', 10.96)

Serpent

text
mat fuel  -10.96
    92235.80c  0.045
    92238.80c  0.955
    8016.80c   2.0

SCONE

plaintext
nuclearData {
  materials {
    fuel { temp 600; composition {
      92235.06  7.22e-04;
      92238.06  2.23e-02;
      8016.06   4.59e-02;
    } }
  }
}

Atomic densities atoms/(cm·barn). ZAID.TT: 06 = 600 K

Cylinder Surface (R=0.4 cm, axis along Z)

A right circular cylinder. MCNP uses C/Z; Serpent uses cyl; OpenMC uses Python API.

MCNP

text
1  c/z  0 0 0.4

OpenMC (Python)

python
cyl = openmc.ZCylinder(r=0.4)

Serpent

text
sur 1  cyl  0 0 0.4

SCONE

plaintext
surfaces {
  pinSurf { id 1; type zCylinder; radius 0.4; origin (0 0 0); }
}

Criticality (k-eff) Calculation

Running a criticality search. Active cycles, inactive cycles, and particles per cycle.

MCNP (kcode)

text
kcode 10000 1.0 50 250

250 total cycles, 50 inactive, 10000 particles/cycle

OpenMC (Python)

python
settings.batches = 250
settings.inactive = 50
settings.particles = 10000

Serpent

text
set pop 10000 250 50

10000 neutrons/cycle, 250 cycles, 50 inactive

SCONE

plaintext
pop 100000;
active 250;
inactive 50;

100000 particles/cycle, 250 active, 50 inactive

Thermal Scattering (Light Water)

S(α,β) data for H in H₂O. MCNP uses mt numbers; OpenMC/Serpent use library names.

MCNP

text
mt1  lwtr.20t

OpenMC (Python)

python
water.add_s_alpha_beta('c_H_in_H2O', '71t')

Serpent

text
therm lwtr lwtr.20t

SCONE

plaintext
moder { 1001.06 (h-h2o.42); }

Inside nuclearData materials block

Related Topics

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