SERPENT Monte Carlo Code

Master Serpent - The continuous-energy Monte Carlo code for reactor physics and burnup calculations. Free comprehensive tutorials developed at VTT Technical Research Centre of Finland.

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Last Updated: February 2026

Why engineers choose Serpent

Serpent is a continuous-energy Monte Carlo code optimized for reactor physics and fuel cycle analysis. Developed by VTT, it blends high-fidelity transport with fast burnup, perturbation, and lattice-physics tooling.

Burnup-ready

Integrated depletion solver with detailed isotopic tracking and group constant generation for core simulators.

Efficient engine

Optimized algorithms and parallelism enable large lattice and core models without massive compute budgets.

Lattice physics output

Produce cross sections, diffusion coefficients, and perturbation data directly for deterministic workflows.

Flexible geometry

Rich CSG modeling with pin/lattice helpers plus CAD-based mesh imports for advanced studies.

Frequently Asked Questions

How do I obtain a Serpent license?

Licensing is handled by VTT. Academic institutions can request access through the official Serpent site, while commercial entities purchase supported seats that include updates and user support.

Which operating systems support Serpent?

Serpent compiles on Linux and runs on Windows via WSL2. Most production teams build on Linux clusters to take advantage of MPI scaling.

How does Serpent differ from MCNP or OpenMC?

Serpent specializes in reactor physics with integrated burnup, lattice physics, and perturbation capabilities. MCNP remains the general-purpose transport standard, and OpenMC focuses on a Python-first API.

Sample Serpent Input

Here's a basic 17×17 PWR fuel assembly model demonstrating Serpent's input structure:

serpent

% --- Simple PWR fuel assembly model ---

% --- Materials:
mat fuel -10.4
92235.03c -0.04
92238.03c -0.96
8016.03c  -0.12

mat clad -6.55
40090.03c 1.0

mat water -1.0 moder lwtr 1001
1001.03c 2.0
8016.03c 1.0

% --- Geometry:
pin 1
fuel  0.4096
clad  0.4750
water

pin 2
water 0.6120

lat 10 1 0.0 0.0 17 17 1.26
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 2 1 1 2 1 1 2 1 1 1 1 1
1 1 1 2 1 1 1 1 1 1 1 1 1 2 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 2 1 1 1 1 1 1 1 1 1 2 1 1 1
1 1 1 1 1 2 1 1 2 1 1 2 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

cell 10 0 fill 10 -20
cell 20 0 outside      1

% --- Run parameters:
set pop 10000 100 40

Key Features Shown

Material definitions with ENDF/B identifiers
Pin cell geometry with fuel, clad, and water
Lattice structure for assembly layout
Population settings for Monte Carlo

Try Modifications

Change fuel enrichment (U-235 fraction)
Modify pin pitch in lattice definition
Add burnable absorber pins
Increase population for better statistics

Advanced capabilities

Burnup & depletion

Create montage burnup chains, branch cases, and depletion histories for realistic cycle studies.

Group constant generation

Export homogenized constants for nodal or diffusion solvers directly from Serpent tallies.

Serpent applications

Reactor physics

k-effective benchmarking and lattice physics
Control rod worth & temperature coefficient analysis
SMR and advanced reactor concept evaluation
Fuel performance coupling via homogenized data

Fuel cycle analysis

Isotopic depletion and radiotoxicity tracking
Waste characterization and storage planning
Burnable absorber optimization
Cycle length and reload strategy studies

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