JAEA-Conf 2011-002 - 日本原子力研究開発機構

JAEA-Conf 2011-002
30. A Study of Pre-equilibrium Reaction Induced by
Neutron for Nickel
Myeonghwan Mun*, Young-Ouk Lee , Hyeong Il Kim
Korea Atomic Energy Research Institute,
Daeduk-daero 1045, Dukjin-dong, Yuseong-gu, Daejeon, Korea
e-mail: mhmoon@kaeri.re.kr
Nuclear reaction models play an important role in producing the reasonable nuclear data which is
needed not only for fundamental research in nuclear physics but also practical applications in the field
such as nuclear technology, medicine and industry. The reaction models can be divided into three parts,
direct, pre-equilibrium and compound reaction in terms of time scales. The direct and compound
models have been developed well so as to reproduce experimental data, but the pre-equilibrium model
is sometimes in discrepancies with the measurements available. With a focus on improvement of preequilibrium
models, we have performed nuclear reaction calculations for natural nickel induced by
neutron in the incident energy up to 20 MeV using the TALYS code and compared with the available
experimental data.
1. Introduction
The nuclear cross sections are essential for the simulation of nuclear related applications such as the
reactor core simulation, radiation shielding calculation in the accelerator, the spacecrafts and other
nuclear facilities, and radioisotope production for medical and industrial applications. Because nickel
is the important structural material almost omnipresent in any nuclear power reactor with iron, nuclear
reaction data with high accuracy on nickel are of considerable importance for testing nuclear reaction
models and for studying radiation damage.
Nuclear cross section data needed for those nuclear applications can be produced by fitting the
measured data or by nuclear model calculations. However, it is almost impossible to obtain the
measurements in a full energy region and for all physical quantities possible. The nuclear model
calculations can cover the shortcomings of the experiments and help for one to comprehend the
nuclear reaction mechanism. In these days, nuclear reaction codes employing the up-to-date nuclear
theory can describe the detail nuclear reaction mechanism through the rapid developments of modern
computing system.
This work aims at understanding a comprehensive nuclear reaction mechanism and producing the
more accurate nuclear data for nickel required at nuclear related fields. Especially this work focuses on
the pre-equilibrium reaction which shows some discrepancies with the measured data unlike direct and
compound ones. The employed nuclear reaction code is Talys [1] which provides a complete and
accurate simulation of nuclear reactions in the 1keV-200 MeV energy range.
2. Nuclear reaction models
Nuclear reactions are described by several models which are linked together to calculate nuclear
cross sections. An outline of the general theory and modeling of nuclear reactions can be given in
many ways. These can be distinguished as three main types of reaction mechanisms according to their
reaction times. A direct reaction happens after one or two collisions inside the target nucleus on a short
time scale (typically ~10 -22 s). On the other hand, the compound reaction that proceeds via the
formation of the compound nucleus occurs in the relatively long time (10 -16 ~10 -18 s). The preequilibrium
reaction takes place at intermediate time (10 -20 ~10 -22 s) between direct and compound