2-1	Nuclear Data Library Supporting the Basis of Nuclear Energy Research -Release of the Latest Version JENDL-3.3-

Fig. 2-1 Cross sections of 235U The figure on the left shows the elastic scattering cross section, capture cross section, fission cross section, and their sum, the total cross section. Peaks of the cross sections correspond to the structure of a compound nucleus (236U formed by a neutron-induced reaction on 235U, in this case). Experimental data are required to analyze such a complicated structure. Recently, following detector improvements, high-resolution and high-accuracy measurements have been performed. Consequently, the quality of evaluated nuclear data is improving.

Fig. 2-2 Benchmark tests for thermal reactors The figure on the right illustrates the ratios of calculations to measured neutron effective multiplication factors, which are important for the design of nuclear reactors. It is commonly accepted that the ratio should be predicted within a 0.5% uncertainty, namely, ranging from 0.995 to 1.005. The calculations using JENDL-3.3 are applicable to a variety of reactor types. TCA: Tank-type Critical Assembly STACY: Static Experiment Critical Assembly TRACY: Transient Experiment Critical Assembly JRR-4: Research Reactor (Swimming pool type)

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A nuclear reactor is a device that utilizes the energy of neutron-induced fission of materials such as 235U or 239Pu. The nuclear reactions that neutrons undergo with uranium and plutonium in fission reactors determine the operational characteristics of the reactors. The probabilities (cross sections) for these nuclear reactions are called "nuclear data." Nuclear data evaluation provides the most probable data set using experimental data, theoretical calculations, and statistics. The resultant database is called "an evaluated nuclear data library." Starting in the 1970s, we developed our own nuclear data library, JENDL (Japanese Evaluated Nuclear Data Library). The latest version, which includes neutron-induced reaction data for 337 nuclides, was released in May 2002. This is the result of nuclear data activities by JAERI in cooperation with Japanese research organizations and industries. Fig. 2-1 shows the cross sections of 235U. Since it is based on recent measurements and theoretical calculations, reactor performance can be predicted precisely by JENDL-3.3. The reliability of JENDL-3.3 was confirmed by application tests called "benchmark tests." Fig. 2-2 shows the results of a benchmark test for thermal reactors. As indicated by the figure, JENDL-3.3 is more accurate than JENDL-3.2 and the US library ENDF/B-VI.5. Covariances included in JENDL-3.3 make it possible to estimate uncertainties (arising from nuclear data) in design calculations. Being fundamental data of nuclear reactions, JENDL data are applicable to fields ranging from medical applications of nuclear reactions to research on nucleosynthesis in the primordial universe.

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Reference K. Shibata, JENDL-3.3: A New Version of JENDL General-purpose Library, Tran. Am. Nucl. Soc., Milwaukee 2001, 41 (2001).

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Persistent Quest Research Activities 2002 Copyright(c) Japan Atomic Energy Research Institute