NEA Mandates and Structures

Joint Evaluated Fission and Fusion (JEFF) Nuclear Data Library Co-ordination Group

Chair(s): Arjan PLOMPEN, Belgium
Secretary:  Franco MICHEL-SENDIS
Vice-Chair(s): Robert W. MILLS, United Kingdom
Member(s): Argentina, Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, Japan, Korea (Rep. of), Mexico, Netherlands, Norway, Poland, Portugal, Romania, Russia, Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom
Full participant(s): European Commission
Under the NEA Statute
Observer(s)(International Organisation): International Atomic Energy Agency (IAEA)
By agreement
Date of creation:01 October 1981
End of mandate:30 June 2021

Mandate (Document reference):

  • Established at the meeting of the NEA Steering Committee in October 1981
  • Prolonged at the 15th meeting of the Executive Group on the Nuclear Science Committee [NEA/SEN/NSC/EG(2006)4]
  • Progress Report for 2005, Work in Hand in 2006 and Programme of Work for 2007 [NEA/SEN/NSC/EG(2006)2]
  • Approved at the 18th Meeting of the Executive Group of the Nuclear Science Committee, [NEA/SEN/NSC/EG(2009)4]
  • Prolonged at the 19th Meeting of the Executive Group of the Nuclear Science Committee [NEA/SEN/NSC/EG(2010)4]
  • Mandate extended at the 22nd Meeting of the Executive Group of the Nuclear Science Committee [NEA/SEN/NSC/EG(2013)4]
  • Mandate extended at the 23rd Meeting of the Executive Group of the Nuclear Science Committee [NEA/SEN/NSC/EG(2014)8]
  • Mandate extended at the 24th Meeting of the Executive Group (Data Bank Management Committee) of the Nuclear Science Committee [NEA/SEN/NSC/EG(2015)6]
  • Mandate extended at the 5th Meeting of the Management Board for the Development, Application and Validation of Nuclear data and Codes (MBDAV) [NEA/SEN/MBDAV(2018)2]
  • Mandate of the Joint Evaluated Fission and Fusion (JEFF) Nuclear Data Library Co-ordination Group [NEA/SEN/MBDAV(2018)3]

Mandate (Document extract):

Extract from document NEA/SEN/MBDAV(2018)3


The purpose of the JEFF Co-ordination Group (JEFF CG) is to develop, compile, verify, validate, document, distribute and promote high-quality sets of evaluated nuclear data in standard formats for a wide range of scientific and technical applications, with an emphasis on fission and fusion applications, under the “Joint Evaluated Fission and Fusion (JEFF) Nuclear Data Library” label.

The JEFF CG assesses the needs for nuclear data improvements and addresses those needs by initiating the necessary measurements, evaluation and benchmarking efforts in participating institutions. The results of these efforts are contributed to the JEFF libraries. The JEFF CG aims at catering to the widest possible range of applications in NEA Data Bank participating countries with modern tools of development and dissemination.

The NEA Data Bank participating countries involved in JEFF will actively engage nuclear data users and evaluators from their national institutions to provide feedback on JEFF libraries, improved nuclear data evaluations and services.


The JEFF CG is responsible for giving the final approval of all updates to the JEFF Nuclear Data Library and for scheduling their official release.

The JEFF CG will collaborate with other similar national initiatives or projects aimed at improving evaluated nuclear data and with the NEA Working Party on International Nuclear Data Evaluation Co-operation (WPEC).

The JEFF CG will also co-operate with major international nuclear data projects and institutions, in particular:

  • The Joint Research Centre of the European Commission;
  • The International Atomic Energy Agency (IAEA), through the International Nuclear Data Committee (INDC) and the Nuclear Data Section (NDS);
  • EURATOM-funded activities, such as the nuclear data projects of the European Union Framework Programme for Research and Innovation HORIZON2020, including the fission and fusion activities;
  • The TENDL Nuclear Data Library initiative.


The NEA Data Bank Secretariat shall provide the following services to the JEFF CG:

  • Organisation of JEFF meetings and Nuclear Data Weeks in consultation with the JEFF CG;
  • Publication and distribution of JEFF CG documents, updating the corresponding web pages, and producing official summary records of each JEFF CG meeting;
  • Assemble, release and distribute the official versions of the JEFF Nuclear Data Library. It is also responsible for collecting users’ feedback, maintaining up-to-date information, and archiving past file versions and records;
  • Implement and co-ordinate a comprehensive quality assurance (QA) process involving verification, testing and benchmarking tasks according to well-defined criteria;
  • As part of broader nuclear data services to the NEA Data Bank participating countries, provide a number of testing, processing and benchmarking services for evaluated nuclear data files.


Following the successful release of the JEFF Nuclear Data Library 3.3 version (referred to as JEFF-3.3) , JEFF CG is now focusing at the demands for a JEFF-4 library with increased requirements in completeness, accuracy, uncertainties/margins, benchmarking/validation, processing & code interfacing, a quality assurance process and modern software developments that are to be implemented. The range of applications of a nuclear data library is wide and the corresponding needs are varied. This is clearly witnessed by the contributions presented by participants at the technical sessions organised by the JEFF CG and by the discussions at the WPEC that reflect the interests of the contributing institutes and organisations. Advances in our understanding of how to tackle such issues with increased automation, computer power, new data formats and software interfaces surfaced during the development of the JEFF-3.2 and 3.3 versions of the JEFF Nuclear Data Library. However, the methods and means proposed were too revolutionary and the implications for ensuring performance in important areas of interest and past effort remained unclear. The JEFF CG will take these important developments on board and set new standards for a data library and the methods by which it is developed and tested.

The completion of this endeavour will require following a two-step approach, spanning over the period of two JEFF CG mandates (i.e. 6 years). In the first step, standards and methods for the JEFF Nuclear Data Library and its methods of production, testing and maintenance will be developed. This period will culminate in a test-library that is the vehicle for establishing proof of principle of the different aspects for development of the final library JEFF-4.0 and for increasing its range of applications and users. In the second step, the new methods will be applied to produce a new library with a full set of uncertainties and covariance matrices, and a clear link to the experimental database underlying the estimates, uncertainties and covariances. The JEFF Project aims at a clear specification of the role of the basic microscopic reaction database and the role of the included integral benchmarks in the production of the library and its testing.

Ultimately, the JEFF-4.0 version and its successors aim to become a fully consistent general purpose library, which will contain all needed data (neutrons and other incoming particles, incident energies, target nuclides, reaction types, outgoing products and properties) and associated covariance information, which can be reliably used for a large spectrum of applications, and which has a proven performance level equal or better than that of JEFF-3.3.

This long-term goal requires that the JEFF file evaluation and benchmarking process be revised in order to be made coherent and efficient. Completeness, version management, internal consistency, storage format and interaction with user code systems will be thoroughly reviewed to comply with modern software, database management and data visualisation tools. The aim is to ensure flexibility and enhanced quality control for JEFF users in a modern computational setting.

The released JEFF libraries are publicly available to all without restrictions and distributed by the Data Bank in the form of computer files through a dedicated webpage.


  • Definition of a system for nuclear data library generation that combines completeness with high quality, effectively combining best available scientific and technical know-how;
  • Development of a test library to demonstrate feasibility;
  • Definition of an enlarged suite of benchmarks covering physics interests of the community;
  • Definition of the requirements for the content of the new library;
  • Specifications for the quality assurance system that is desired for the new library.

These deliverables will aim at consolidating the achievements in the JEFF Nuclear Data Library version 4.0 (JEFF-4.0) in the subsequent period (2021-2024).

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