Serpent distribution

Serpent has been in public distribution since 2009. A new base version 2.2 was released in May 2022, making the previous versions (1.1 and 2.1) obsolete. Contrary to common misconception, Serpent is not open source software. The distribution is managed by two data centers and VTT. The current license options are as follows:

1) Single-user research license issued by the OECD/NEA Data Bank or the Radiation Safety Information Computational Center (RSICC). Applications are limited to non-commercial research and educational use. No license fees are applied, but RSICC may charge a one-time processing fee for their services. An agreement between the NEA and the International Atomic Energy Agency (IAEA) enables distribution to some non-member countries as well. The contract between VTT and RSICC has not yet been finalized, but the distribution should open soon.
2) Academic group license ("Professor License") issued by VTT. Applications are limited to educational purposes and academic research. No license fee, but VTT charges a one-time processing fee to cover the expenses.
3) Commercial license issued by VTT. No limitations regarding commercial use, but the detailed terms and conditions are negotiated on a case-by-case basis. License fee depends on the term length and number of users.

The single-user research licenses should be requested directly from either of the two data centers. Organizations in NEA Data Bank member countries usually have a nominated liaison officer, who is handling all requests collectively. Academic group licenses and commercial licenses can be obtained by contacting the Serpent developer team. The contact information is found at the top right corner of this page.

Export control

Serpent is export control software. Distribution to all foreign countries therefore requires an export license from the Finnish authorities. The procedure depends on the license type and the country from which the request was made.

The NEA Data Bank is pre-approved to distribute Serpent to the following countries: EU member states, Australia, South Korea, Canada, Iceland, Japan, New Zealand, Norway, Switzerland, United Kingdom and the United States. Applications from other countries are handled separately, and the process may require some additional steps.

Negotiations between VTT and RSICC are still pending, and more information will follow when the RSICC distribution is opened. It is likely that similar pre-approval procedure will be applied to export control, enabling distribution to the United States, Canada, Australia, Argentina, Brazil, South Africa, Japan, South Korea, and member countries of the European Union.

Bilateral agreements (options 2 and 3 above) are negotiated between VTT and the licensee organization. The export license application is handled by VTT as part of the procedure. For most countries this requires no actions from the licensee organization, but the paperwork may take some time.

Serpent cannot be distributed at all to the following countries: Belarus, China, Iran, North Korea, Russia, Sudan and Syria.

Commercial and non-commercial use

Serpent can be used for non-commercial research and educational purposes without a license fee, but which applications fall under this category is subject to some interpretation. What is considered to be unquestionably non-commercial work is as follows:

Basic scientific research and educational use:

Demonstration, exercises, etc. performed as part of university coursework
Thesis work (when not carried out as part of other commercial work)
Publicly funded and other research explicitly specified as non-commercial work (e.g. research carried out as part of Euratom projects)

Evaluation of feasibility for commercial use:

Testing, benchmarking, etc. for the purpose of evaluating the practical feasibility of Serpent for its intended commercial use
Familiarizing and learning to use the code

Any non-commercial work can be carried out using the code versions sub-licensed by the OECD/NEA Data Bank and RSICC (option 1 above).

The single-user license may not be ideal for all types of educational use, for example, when Serpent is used for exercises on a reactor physics course or a student project. For this purpose VTT offers a group license for teachers and professors (option 2 above), that also enables more temporary use of the code by a group of students. This license type is intended for coursework and thesis projects. Long-term research carried out at universities by post-docs, faculty members, etc. requires the standard personal license from the NEA or RSICC.

What is considered to be unquestionably commercial work is as follows:

Any use generating direct revenue:

Consulting, contract work for a third party
Training provided for a third party (excluding basic educational use)

Any use where Serpent forms a key part of the design, operation or maintenance process for operating reactors, fuel cycle or experimental facilities:

Core design, criticality safety, radiation protection, etc. carried out for a commercial or research reactor
Design of experimental facilities or individual experiments
Verification / validation of production tools used for commercial work

Any use where Serpent forms a key part of the design process of new technology with TRL > 1:

Design of new reactor types beyond the pre-conceptual design stage
Design of components for fusion reactors, other experimental facilities and other technology beyond the pre-conceptual stage

Any use within the listed categories requires a commercial license (option 3 above). Applications that cannot be clearly categorized under commercial or non-commercial work are evaluated on a case-by-case basis. For questions and more information, contact the Serpent developer team (contact information is found at the top of this page).

Updates and data libraries

Serpent development has reached a stage where updates are no longer frequently required. Development is nevertheless an on-going process, and an up-to-date version of the code is planned to be released after every six or twelve months. The new version is submitted to the NEA Data Bank and RSICC for distribution. Users with a bilateral contract (options 2 and 3 above) will receive the updates directly from VTT.

Serpent uses ACE format cross section libraries for neutron and photon transport physics. Radioactive decay, fission yield and isomeric branching data is read from unprocessed ENDF format data files. The Serpent 2.2 installation package includes only the source code, and the physics data (several gigabytes) can be downloaded from a separate repository.

The most recent neutron cross section libraries are based on the ENDF/B-VII.1, JEFF-3.2, JENDL-4.0 and FENDL-3.0 evaluated nuclear data files, but the repository also contains older libraries distributed with the Serpent 1 installation package based on ENDF/B-VI.8, ENDF/B-VII, JEF-2.2, JEFF-3.1 and JEFF-3.1.1. The contents of the repository will be updated separate from the source code.

ACE format data is also used by other Monte Carlo codes, such as MCNP, OpenMC and Geant4. Cross section libraries and other nuclear data can also be found on-line at:

The OECD/NEA Joint Evaluated Fission and Fusion (JEFF) project website:
Los Alamos National Laboratory Nuclear Data Libraries website:
TENDL data libraries at the TALYS-code website:
The US National Nuclear Data Center:
The IAEA Nuclear Data Center:

The "xsdir" directory files used by MCNP can be converted to Serpent format using the utility script. More information on setting up the data libraries is found in Serpent Wiki.

System requirements

Serpent is distributed in source code form. The development is carried out under 64-bit PC Linux operating systems, using the GNU and Intel C compilers. Serpent has also been tested to be fully functional in macOS (Catalina 10.15). Installation on a Windows platform is not recommended or officially supported, but some users have managed to run Serpent with Cygwin or WSL (see more information at the Serpent discussion forum).

Parallelization with the Message Passing Interface (MPI) may require installation of additional libraries, and graphical output produced by geometry and mesh plotters requires installation of the GD open source graphics library. Instructions for installing GD in various systems can be found at the discussion forum. The source code can also be compiled without MPI and GD.


The methodology used in Serpent is documented in scientific publications, the most important of which are listed on the publications tab. User manual has been moved to the on-line Serpent Wiki. Recommended Wiki-pages for first-time users include:

Installing and running Serpent
Input syntax manual
Hands-on tutorial
Collection of example input files
Pitfalls and troubleshooting

The old Serpent 1 user manual is still available online, but it should be noted that the contents have been largely outdated. On-line user support is available at the Serpent discussion forum.

International Serpent community

Serpent has been in public distribution since 2009. User statistics are no longer actively maintained, but by 2020 the Serpent community had grown to more than 1000 users in 250 universities and research organizations in 44 countries around the world. International user group meetings are organized annually in different locations. The meetings held so far are:

2011 1st International Serpent User Group Meeting in Dresden, Germany, September 15-16 2011
2012 2nd International Serpent User Group Meeting in Madrid, Spain, September 19-21 2012
2013 3rd International Serpent User Group Meeting in Berkeley, California, USA, November 6-8 2013
2014 4th International Serpent User Group Meeting in Cambridge, UK, September 17-19, 2014
2015 5th International Serpent User Group Meeting in Knoxville, Tennessee, USA, October 13-16, 2015
2016 6th International Serpent User Group Meeting in Milan, Italy, September 26-29, 2016
2017 7th International Serpent User Group Meeting in Gainesville, Florida, USA, November 6-9, 2017
2018 8th International Serpent User Group Meeting in Espoo, Finland, May 29 - June 1, 2018
2019 9th International Serpent User Group Meeting in Atlanta, Georgia, USA, October 14-19, 2019
2020 10th International Serpent User Group Meeting, on-line event organized by TUM, October 27-30, 2020
2021 No meeting because of the COVID-19 pandemic
2022 11th International Serpent User Group Meeting in Garching, Germany, August 29 - September 1, 2022

Version history

The updates to Serpent 2 since the release of the current base version 2.2.0 are listed below:
2.2.0May 23, 2022
 Release of base version 2.2.0


Contact developer team:


User organizations:

Aalto University, Finland
Alvel, Czech Republic
Air Force Institute of Technology, USA
AMEC NSS, Canada
Analytical Mechanics Associates, USA
Apollo fusion, USA
Argonne National Laboratory (ANL), USA
Areva, France
Atomic Alchemy, USA
Australian Nuclear Science and Technology Organisation (ANSTO)
AUSY-Group, France
Axpo AG - Kernkraftwerk BEZNAU, Switzerland
Belgoprocess, Belgium
Bangor University, UK
Ben Gurion University of the Negev, Israel
Binding Energy, Belgium
Brno University of Technology, Czech Republic
Brookhaven National Laboratory, USA
Budapest University of Technology and Economics, Hungary
BWX Technologies, Inc., USA
Canadian Nuclear Laboratories (CNL)
Candu Energy Inc., Canada
Catholic University of the Maule, Chile
Chilean Nuclear Energy Commission
Canadian Nuclear Safety Commission
Center for Space Nuclear Research (CSNR), USA
Centre for Energy Research, Hungary
Centro de Desenvolvimento da Tecnologia Nuclear (CDT), Brazil
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Spain
Centro Tecnico Aeroespacial (CTA), Brazil
Chalmers University of Technology, Sweden
Colorado School of Mines, USA
Comision Nacional de Energia Aatomica (CNEA)
Commissariat à l'Énergie Atomique (CEA), France
Czech Technical University in Prague, Czech Republic
Defence Academy of the United Kingdom
Delft Nuclear Consultancy, the Netherlands
École nationale supérieure d'ingénieurs de Caen (ENSICAEN), France
École Polytechnique de Montréal, Canada
École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
EDF Energy, UK
Électricité de France (EDF)
Elysium Industries, USA
ENEA, Italy
Energy Research Inc., USA
ENPRO Consult, Bulgaria
Eskom, South Africa
Federal University of State of Rio de Janeiro, Brazil
Fennovoima, Finland
Finnish Defence Forces
Flibe Energy, USA
Forschungszentrum Jülich, Germany
Fortum Nuclear Services, Finland
Framatome, France
Frazer-Nash Consultancy, UK
GDF Suez, Belgium
Georgia Institute of Technology, USA
Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH, Germany
Grenoble Institute of Technology, France
Hacettepe University, Turkey
Hanyang University, Republic of Korea
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany
Idaho National Laboratory (INL), USA
Idaho State University, USA
IDOM, Spain
Imperial College, London, UK
Institut de radioprotection et de sûreté nucléaire (IRSN), France
Institut de Physique Nucléaire d'Orsay, France
Institut Laue-Langevin, France
Institute for Energy Technology (IFE), Norway
Institut für Festkörper-Kernphysik (IFK), Germany
Institut Jožef Stefan, Slovenia
Institute of Nuclear Energy Research (INER), Taiwan
Institute for Nuclear Research (SCN), Romania
Institute for Nuclear Research of National Academy of Sciences of Ukraine
Instituto Peruano de Energia Nuclear, Peru
Instituto de Pesquisas Energéticas e Nucleares (IPEN), Brazil
Instituto Nacional de Investigaciones Nucleares, Mexico
International Atomic Energy Agency (IAEA)
INVAP, Argentina
Istanbul Technical University, Turkey
Japan Atomic Energy Agency (JAEA)
JRC Petten, the Netherlands
Kairos Power, USA
Kansas State University, USA
Karamanoglu Mehmetbey University, Turkey
Karlsruhe Institute of Technology (KIT), Germany
KEPCO Nuclear Fuel, Korea
Kernkraftwerk Gösgen-Däniken AG, Switzerland
Khalifa University of Science, Technology & Research (KUSTAR), UAE
Kinectrics, Canada
King Mongkut's University of Technology Thonburi, Thailand
Korea Advanced Institute of Science and Technology (KAIST)
Korea Atomic Energy Research Institute (KAERI)
Korea Hydro & Nuclear Power-Central Research Institute (KHNP-CRI)
Korea Institute of Nuclear Safety (KINS)
Kyung Hee University, Korea
Lappeenranta University of Technology (LUT), Finland
L'Ecole d'Application Maritime de l'Energie Atomique (EAMEA)
Los Alamos National Laboratory, USA
Nagra, Switzerland
Nagoya University, Japan
North Carolina State University, USA
North-West University, South Africa
Martingale Inc., USA
Massachusetts Institute of Technology (MIT), USA
Max Planck Institute for Plasma Physics, Germany
McMaster University, Canada
Milano Multiphysics, Italy
Missouri University of Science and Technology, USA
MPR Associates, USA
National Centre for Nuclear Research (NCBJ), Poland
National Institute of Standards and Technology (NIST), USA
National Nuclear Laboratory (NNL), UK
National University of Mongolia
National University of Singapore
Nippon Advanced Information Service (NAIS), Japan
Nuclear-21, Belgium
Nuclear and Industrial Engineering S.r.l (N.IN.E), Italy
Nuclear Research & consultancy Group (NRG), The Netherlands
Nuclear Research Institute Rez, plc. (NRI), Czech Republic
Nucleoeléctrica Argentina S.A.
NUCLIC - Nuclear Innovation Consultancy, the Netherlands
Oak Ridge National Laboratory (ORNL), USA
OECD Nuclear Energy Agency (NEA)
Oklo, Inc., USA
Ontario Tech University, Canada
Orano, France
Oregon State University, USA
Pacific Northwest National Laboratory (PNNL), USA
Paul Scherrer Institute (PSI), Switzerland
Philippine Nuclear Research Institute
Penn State University, USA
Politecnico di Milano, Italy
Politecnico di Torino, Italy
Polytechnic University of Valencia, Spain
PreussenElectra GmbH, Germany
Princeton University, USA
Purdue University, USA
Radiant industries inc., USA
Radiation and Nuclear Safety Auhtority (STUK), Finland
Rensselaer Polytechnic Institute (RPI), USA
Royal Institute of Technology (KTH), Sweden
Royal Military College of Canada
RPA Impulse, Ukraine
RWTH Aachen University, Germany
Sandia National Laboratory, USA
Sapienza Università di Roma, Italy
Science and Technologies Facilities Council, UK
SCK•CEN, Belgium
Seaborg Technologies, Denmark
Service d'Etudes de Réacteurs et des Mathématiques Appliquées (SERMA), France
Sinop University, Turkey
Skoda JS a.s., Czech Republic
Slovak University of Technology in Bratislava, Slovakia
Sorbonne University, France
South African Nuclear Energy Corporation (NECSA)
State Scientific and Technical Center on Nuclear and Radiation Safety of Ukraine (SSTC NRS)
Studsvik Scandpower
Subatech - Ecole des Mines de Nantes, France
SungKyunKwan University, Korea
Svensk Kärnbränslehantering AB (SKB), Sweden
Technical University of Catalonia, Spain
Technical University of Delft, the Netherlands
Technical University Denmark (DTU)
Technical University of Dresden, Germany
Technical University of Munich, Germany
Technical University of Vienna, Austria
Teollisuuden voima (TVO), Finland
Terrapower, USA
Terrestrial Energy, Canada
Texas A&M University, USA
Tokyo University of Technology, Japan
Tractebel, Belgium
Transatomic Power Corporation, USA
TS Enercon Ltd., Hungary
TSO Turkey
Turkish Atomic Energy Authority (TAEA)
TUV SUD Industrie Service GmbH, Germany
Ulsan National Institute of Science and Technology, Korea
Ultra Safe Nuclear Corporation (USNC), USA
UMass Lowell, USA
United States Military Academy
United States Naval Academy
United Kingdom Atomic Energy Authority (UKAEA)
Universidad Complutense de Madrid, Spain
Universidad Politécnica de Madrid, Spain
Universidade Federal de Minas Gerais - UFMG, Brazil
Université Joseph Fourier, France
Universitas Gadjah Mada, Indonesia
University of Alabama, USA
University of Birmingham, UK
University of Bologna, Italy
University of California, Berkeley, USA
University of Cambdridge, UK
University of Florida, USA
University of Genova, Italy
University of Helsinki, Finland
University of Idaho, USA
University of Illinois, USA
University of Leeds, UK
University of Liverpool, UK
University of Manchester, UK
University of Michigan, USA
University of Milano-Bicocca, Italy
University of Missouri, USA
University of Neada, USA
University of New Mexico, USA
University of New South Wales, Australia
University of Ontario Institute of Technology, Canada
University of Oxford, UK
University of Pisa, Italy
University of Queensland, Australia
University of Sao Paulo, Brazil
University of Sharjah, UAE
University of Sofia, Bulgaria
University of Stuttgart, Germany
University of Tartu, Estonia
University of Tennessee, USA
University of Texas at Austin, USA
University of Tokyo, Japan
University of Utah, USA
University of West Bohemia, Czech Republic
University of Wisconsin-Madison, USA
University of York, UK
University of Zagreb, Croatia
Uppsala University, Sweden
US Nuclear Regulatory Commission (NRC)
Vanderbilt University, USA
Virginia Commonwealth University, USA
Virginia Tech., USA
Vattenfall, Sweden
Vietnam Atomic Energy Institute
VTT Technical Research Centre of Finland
VUJE, a.s., Slovakia
Warsaw University of Technology, Poland
Westinghouse Electric, USA
Wood, UK
Yellowstone Energy, USA
X-Energy, USA