Nuclear Data Section
Atomic and Nuclear Data for Applications
Both the development and maintenance of nuclear technologies rely on the availability of atomic, molecular and nuclear data to provide accurate numerical representations of the underlying physical processes. Essential data include energy-dependent reaction probabilities (cross sections), the energy and angular distributions of reaction products for many combinations of target and projectile, and the atomic and nuclear properties of excited states, and their radioactive decay data.
The Nuclear Data Section of the Division of Physical & Chemical Sciences (NAPC) within the IAEA Department of Nuclear Sciences & Applications (NA) is responsible for undertaking Agency activities in the related areas of the development and dissemination of atomic and nuclear data for applications. Scientists in developing countries are assisted in their evolution of local capabilities for the generation and application of atomic and nuclear data through an active programme of technology transfer activities . All programme activities of the Nuclear Data Section are implemented as Projects within the Agency (see below).
Data for Applications
Modern nuclear facilities and applications have reached a high degree of sophistication. The safe and economical operation of these complex technologies require detailed and reliable design calculations. These calculations offer a valuable supplement to large-scale mock-up studies by providing very detailed information about system behaviour under both normal and off-normal conditions at a fraction of the cost of experiments. While simulation calculations are becoming more and more economical with the rapid advances in computer technology, the accuracy of these calculations is largely determined by the accuracy of the atomic and nuclear input data.
Within the field of fission reactor technology, one can identify the following specializations that rely on the availability of accurate atomic and nuclear data:
- Fission reactor design
- Nuclear fuel cycles
- Nuclear safety
- Nuclear safeguards
- Reactor monitoring and fluence determination
- Waste disposal and transmutation
Detailed data are required to design a modern nuclear reactor for electricity production and to make prudent decisions regarding the operation of the associated fuel cycle. These designs must conform with strict safety regulations and still remain cost effective. Accuracy requirements are very high, especially for the isotopes of uranium and plutonium and the major shielding and structural materials. There are also many nuclear applications outside the field of fission reactor technology that are of growing economic significance and require substantial data input:
- Accelerator shield design
- Fusion device design and plasma processing technologies
- Personnel dosimetry and radiation safety
- Production of radioisotopes for medical and industrial applications
- Cancer radiotherapy
- Radiation damage studies
- Environmental monitoring and clean-up
- Chemical analysis by activation methods
- Detection of concealed explosives and illegal drugs
- Exploration for oil and other minerals
Radiation therapy of cancer patients is an important example. Many patients are successfully treated with different types of nuclear radiation (photons, electrons, neutrons and charged particles). Accurate determinations of the dose delivered to a tumor and to the surrounding healthy tissue are crucial, and require extensive calibration calculations based on detailed and accurate atomic and nuclear data for the elements that comprise human tissue. The protection of medical personnel also requires the careful design of associated collimators and shields.
Much essential atomic and nuclear data have been obtained by direct measurement. These expensive and demanding measurements are performed within the Member States, using particle accelerators and sophisticated radiation detectors. Thus, approximately 11.8 million nuclear data points have been measured and compiled into computerized form. However, the high costs of such experiments and the large number of possible combinations of target, projectile, projectile energy, reaction product, and product energy and angle prevent comprehensive measurements and compilations of all the data needed for all applications. Data specialists are forced to concentrate on the important requirements for specific current applications. Hence, the experimental database is much more complete for fission power needs than for fusion and non-power applications.
After measurement, the resulting data need to be assembled into standardized computer databases, such as EXFOR and ALADDIN for further processing and application. The large task of data compilation is performed by staff members of the Nuclear Data Section in association with networks of co-operating data centres around the world.
After measurement and assembly, the compiled data require evaluation in order to produce tables of recommended values, which represent the primary information needed by data users. Evaluated data files must be complete (in terms of the intended use), and therefore available experimental data must often be supplemented with theoretical predictions (benchmarked against available experimental data where possible). As in the case of measurements, most data evaluation work is undertaken by specialists within Member States. The results of their work are made available to all other Member States by the Nuclear Data Section (see next paragraph) and co-operating data centres. Gaps in the experimental data can be very extensive for specific studies - for example, comprehensive calculations of neutron activation for fusion applications require neutron cross sections data for more than 65 000 individual activation reactions, and such data are directly available from experiments for less than 3% of the identified reactions.
The Nuclear Data Section provides data users in Member States with cost-free and convenient access to numerical data needed in their applications. Most of the data can be retrieved online via the Internet by the interested user from the IAEA Nuclear Data Section Web page (covering nuclear as well as atomic and molecular data). Users receive exactly the information needed when required. The Agency has established international networks of atomic and nuclear data centres that ensure a high degree of consistency of the activities of the major data centres around the world. Whenever necessary, online access is supplemented by custom data retrievals performed by the data-centre staff of the Nuclear Data Section, with the results distributed electronically or by post to the requester. Capabilities have also been developed to produce and distribute CD-ROM versions of all of the Agency’s main nuclear-data databases. Even users not connected to the Internet can have fast desktop access to the same data that are available from the nuclear data Web server at the time that the CD-ROM "master" was produced. The CD-ROM is also the dissemination method preferred by scientists working with large libraries of relatively static data. As shown in the table, users have responded positively to these services.
|Interactive Nuclear Data retrievals||91,146||114,502||128,368||149,672||
|Interactive Atomic Data retrievals||11,028||16,794||19,481||19,296||
|Data libraries distributed on request||1,841||1,297||1,425||768||820|
The extensive Agency activities to collect and disseminate the data needed in a wide range of applications results naturally in the identification of specific areas where data are either missing or inadequate. IAEA Co-ordinated Research Projects (CRPs) are effectively developed and used by the Nuclear Data Section to contribute significantly to the development of new and improved data to meet these demands. Through the CRP mechanism, the finite resources of the Member States in the fields of data measurement and evaluation can be focused on those needs with the highest priority in the most important applications. Thus, progress in data development is accelerated, while at the same time reducing the risk of duplication of effort. Numerical data files produced by CRPs provide new products for dissemination by the Agency, a good example being the Reference Input Parameter Library . An active programme of publications and written reviews, including recommendations by international experts regarding future directions, can be made available to all Member States.
The CRPs described above also help developing countries to introduce skills and local infrastructure in the generation and application of atomic and nuclear data within their countries. Another mechanism for technology transfer is on-the-job training of fellows from developing countries (by the staff of the Nuclear Data Section). Probably the most visible means of technology transfer in the Section is the annual series of IAEA/International Centre for Theoretical Physics (ICTP) Nuclear Data Workshops , with participation of around 50 scientists from 25 to 30 developing countries over an intensive period of five weeks per year.
Atomic and Nuclear Data Activities include the following areas of work:
Data Services, Data Networks and User Support -- establishment and maintenance of accurate and up-to-date atomic and molecular data libraries; collection and dissemination of all such data needed by the nuclear technologies of Member States; co-ordination of networks of national and regional data centres to promote the exchange of atomic and nuclear data needed for applications, and to maintain manuals and software for internationally-agreed database formats and exchange procedures.
Nuclear Data Standards and Evaluation Methods -- provision of know-how and facilities to enable users in Member States to produce evaluated nuclear data that satisfy the accuracy and consistency demanded by emerging nuclear technologies through the development of recommended evaluation methods and procedures.
Nuclear Data for Radiotherapy Using Radioisotopes or External Radiation Sources -- provision to Member States of nuclear data to quantify the production and use of radioisotopes and other radiation sources for cancer treatment.
Atomic and Molecular Data for Fusion Experiments -- enhancement of the competencies of Member States in their research into nuclear fusion through the provision of internationally-recommended atomic, molecular, plasma-material interaction and material properties databases.
Data for IBANDL -- The Ion Beam Analysis Nuclear Data Library contains most of the available experimental nuclear cross-sections relevant to Ion Beam Analysis
Nuclear Data for Reactor Dosimetry -- augmentation of nuclear data for dosimetry reactions by assessing the data needs of Member States, develop the appropriate data files, and formulate data files of consistent nuclear data constants for specific applications within Member States.
Nuclear Data Libraries for Advanced Nuclear Facilities -- enhancement of the capabilities of Member States in the use of internationally-recommended cross section libraries for intercomparison studies of advanced concepts for nuclear power generation.