Modern nuclear installations and nuclear instrumentation have reached a high degree of sophistication, their design and safe operation is only possible on the basis of accurate calculations using up-to-date nuclear constants, called nuclear and atomic data, as input. The amount of data needed for such calculations, can be enormous. For example, for the calculation of the physical behaviour of the core of a research reactor and its safe operation (Fig. 1) a collection of data for 130 nuclides with more than 10 000 numbers in it must be used. Another set of data of about the same size is used to calculate the radioactive inventory build up in the reactor and to develop an optimal waste management strategy for the spent fuel of such a reactor.
Even more detailed data are required to design a modern nuclear reactor for electricity production and to make decisions on the fuel cycle for today and for the near future. This design must conform with the strict safety regulations and still remain cost effective. The requirements for the quality and accuracy of data for this purpose are very high.
Another common example of application of nuclear techniques is radiation therapy of cancer patients. Only in the European Community countries there are more than 1 million new incident cases of cancer per year. About 18% of the patients are cured by radiotherapy. Different types of nuclear radiations, e.g. photons, electrons, neutrons and charged particles are used for this purpose. To minimize damage to surrounding normal tissues an accuracy of the dose delivery at the specified location should be better than 5%, Fig. 2. Again, comprehensive atomic, molecular and nuclear data are needed to determine the dose delivery with such precision.
Another important aspect is standardization of measurment techniques. The Nuclear Data Section maintains and updates several international standard data libraries. For example, in order to perform accurate measurements it is necessary to calibrate instruments. A specialist measuring environmental samples, performing activation analysis or other analytical measurements can immediately check the latest updates of standard data such as half-lives, energies of gamma rays etc., by logging on to the IAEA online database of X and gamma ray standards or by requesting the last version of data to be sent on diskette. This service is essential in supporting the high level of accuracy and consistency of measurements worldwide. These are only a few examples of the use of nuclear and atomic data. To satisfy the current demand in data the Nuclear Data Section of the IAEA maintains and permanently updates databases needed for such areas as
The process of measuring atomic and nuclear data requires the use of modern research reactors, neutron generators, charged particle accelerators, spectrometers and other unique scientific devices, see for example Fig. 3.
Such measurements are very costly. Billions of US$ have been spent on construction and operation of these devices and on data measurements in the Member States. But still not all the required data can be measured. For example, data for short lived isotopes must be obtained by theoretical calculations and evaluations.
Nuclear model calculations and evaluations make use of considerable computer resources and the theoretical results obtained require experimental testing and verification.
Nuclear data are generated in many Member States in a wide variety of research institutions. No single Member State whether developing or developed has enough resources to perform the immense task of providing nuclear and atomic data for applications alone. Recognizing this situation the IAEA initiated a continuing program to collect, analyze, recommend and disseminate such data particularly to developing countries and established the Nuclear Data Section in 1964. It started by developing, in co-operation with established national nuclear data programs, a world-wide systematic collection and exchange of nuclear data, and built up over time the dissemination services to users in the Member States.
The process of nuclear and atomic data generation is cyclic in nature and includes feedback from users on the basis of what the necessary corrections, improvements and additions to the data files are made. This scheme is shown in Fig. 4 as an example for nuclear data. A similar arrangement exists for atomic data.
The feedback information from users on the nuclear data needs worldwide is compiled and published as the World Request List for Nuclear Data Measurements (WRENDA) by the IAEA. The last edition of this document, WRENDA 93/94, contains 720 of such requests, including 468 requests which were newly added. In many Member States WRENDA serves as a basis for justification of funding for further nuclear data research.
The objectives and tasks of these Networks are:
This Network consists of four main service centers:
The Nuclear Structure and Decay Data Network is shown schematically on Fig. 6.
In areas where the existing data files are not accurate or substantial data is missing, the Nuclear Data Section organizes Co-ordinated Research Programs, Advisory Group and Consultants' meetings to initiate new data mesurements and evaluations. The output of these coordination efforts are international standard data files and data handbooks for specific applications published as the IAEA TECDOC series, Technical Report series or INDC documents. Thus, the data collection maintained by the IAEA is not static but continues to evolve.
Duplication of effort by scientists in different countries is minimized through international cooperation implemented by the NDS/IAEA, thereby maximizing the use of specialized expertise in each of the cooperating Member States.
In the past years the Agency's Nuclear Data Center received about 800 requests per year from scientists in 93 Member States resulting in an annual shipment of about 300 data files on magnetic tapes and diskettes, 100 related data processing computer codes and 2000 copies of printed materials.
In addition to these conventional request services in 1992 the Agency's Nuclear Data Center started the online access service via Internet. The number of retrievals from the online service is rapidly growing and totaled 4000 in 1995 (see Fig. 7). The distribution of our services by geographical region is shown in Table 1.
The IAEA Atomic Data Center Network publishes an annual supplement to the journal "Nuclear Fusion" on the subject of atomic and plasma-material interaction data for fusion. 350 copies of this document are distributed each year to specialists in the world fusion community.
Bibliographic index of new atomic and molecular data generated in the Member States is compiled by the Section and published by the IAEA biannually in "Atomic and Molecular Data Bulletin". 850 copies of this Bulletin are distributed to specialists in the Member States twice a year.
The Nuclear Data Section is also providing support to the International Thermonuclear Experimental Reactor (ITER) Engineering Design Activities, see Fig. 8, by supplying the required atomic, molecular and nuclear data and developing special data libraries.
In the future it is expected that the demand for the online services will grow fast and significant effort is being made to further widen and improve these services. In 1995 the Nuclear Data Section has put into operation an Alpha Server 2100 computer dedicated to nuclear databases and a RISC 6000 computer dedicated to atomic databases and online service.
The online database of the IAEA Nuclear and Atomic Data Center can be contacted on
the Internet: online@IAEAND.IAEA.ORG or on the World Wide Web: http://www-nds.iaea.org/
|Services by mail||Online Services|
|Region||No.of countries||Perc.of requests||No.of countries||Perc.of requests|
|Africa and Near East||26||13%||2||3%|