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.
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-controlled 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, Iceland, Japan, New Zealand, Norway, Switzerland and United Kingdom. Applications from other countries are handled separately, and the process may require some additional steps. Distribution to United States and Canada is handled by RSICC.

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:

Evaluation of feasibility for commercial use:

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:

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

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

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 "xsdir" directory files used by MCNP can be converted to Serpent format using the xsdirconvert.pl 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.

Documentation

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:

Contact developer team:

Habitat

User organizations: