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SERPENT (Package NEA-1923)


SERPENT is a three-dimensional continuous-energy Monte Carlo reactor physics burnup calculation code, specifically designed for lattice physics applications. The code uses built-in calculation routines for generating homogenized multi-group constants for deterministic reactor simulator calculations. The standard output includes effective and infinite multiplication factors, homogenized reaction cross sections, scattering matrices, diffusion coefficients, assembly discontinuity factors, point-kinetic parameters, effective delayed neutron fractions and precursor group decay constants. User-defined tallies can be set up for calculating various integral reaction rates and spectral quantities.

Internal burnup calculation capability allows SERPENT to simulate fuel depletion as a completely stand-alone application. Extensive effort has been put to optimizing the calculation routines and the code is capable of running detailed assembly burnup calculations similar to deterministic lattice codes within a reasonable calculation time. The overall running time can be further reduced by parallelization.

SERPENT can be used for various reactor physics calculations at pin, assembly and core levels. The continuous-energy Monte Carlo method allows the modelling of any critical reactor type, including both thermal and fast neutron systems. The suggested applications of SERPENT include group constant generation, fuel cycle studies, validation of deterministic lattice physics codes and educational, training and demonstration purposes.


Non-commercial license

The NEA Data Bank offers a single-user license that does not include commercial applications. Please read the terms of the license carefully and refer to the VTT website for more practical information.

Supplementary material

A collaborative repository with Serpent-2 models for International Criticality Safety Benchmark Evaluation Project (ICSBEP) experiments has been setup. These include more than 600 working models tested with the latest SERPENT-2 version available at the Data Bank. Some 3000 extra seed models are available that are conversions from other inputs and serve as a starting position for modelling. These are exclusively available to recipients of the latest ICSBEP Handbook, which can be requested at the link below. Users are encouraged to contribute back to the community any improvements through merge requests. If you have any questions about how to contribute, please contact us.



Leppänen, J., et al. (2015) "The Serpent Monte Carlo code: Status, development and applications in 2013." Annals of Nuclear Energy, 82 (2015) 142-150. DOI:10.1016/j.anucene.2014.08.024

A complete description of the project is found at the SERPENT website

Training materials

A collection of resources are available on the SERPENT Wiki, including a Getting started guide.

The NEA is working with the authors and partners on the creation of a new training course for SERPENT. You can find more information on the currently scheduled events online here.