JAEA-Conf 2011-002 - 日本原子力研究開発機構

JAEA-Conf 2011-002
10. Exciton model and quantum molecular dynamics in inclusive
nucleon-induced reactions
Riccardo BEVILACQUA 1,† , Yukinobu WATANABE 2 , Stephan POMP 1
1 Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 751 21 Uppsala, Sweden
2 Department of Advanced Energy Engineering Science, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
† email: riccardo.bevilacqua@physics.uu.se
We compared inclusive nucleon-induced reactions with two-component exciton model calculations and
Kalbach systematics; these successfully describe the production of protons, whereas fail to reproduce the
emission of composite particles, generally overestimating it. We show that the Kalbach phenomenological model
needs to be revised for energies above 90 MeV; agreement improves introducing a new energy dependence for
direct-like mechanisms described by the Kalbach model. Our revised model calculations suggest multiple preequilibrium
emission of light charged particles. We have also compared recent neutron-induced data with
quantum molecular dynamics (QMD) calculations complemented by the surface coalescence model (SCM); we
observed that the SCM improves the predictive power of QMD.
1. Introduction
Nuclear power plants for the production of electricity have been in operation since 1954, when the
Obninsk facility, in the former Soviet Union, was connected to the grid on the evening of June 26th. Today
nuclear energy plays a key role in the global economy. Japan and South Korea have a leading position in the
nuclear sector. Third country in the world for nuclear power capacity, Japan is currently operating 55 nuclear
reactors; these nuclear reactors generate 30% of the electricity produced in the country. South Korea is producing
40% of its electricity with a network of 20 nuclear reactors. To reduce CO2 emission and to meet an increasing
need for energy, governments of Japan and South Korea are considering an expansion of nuclear power capacity,
however the issue of nuclear waste disposal needs to be addressed and solved [1].
A possible approach to the nuclear waste issue follows the idea of Carlo Rubbia and his group at CERN; they
proposed in 1990’s the concept of Energy Amplifier [2], a device composed by a hadron accelerator coupled to a
subcritical reactor. This device would produce energy with a very small production of minor actinides and longlived
fission products. In the same years, Charles D. Bowman and coworkers at Los Alamos National Laboratory
proposed a transmutation facility for nuclear waste [3]. Accelerator Driven Systems (ADS) are a direct evolution
of these two concepts. The present leading technology in ADS consists in a subcritical core coupled to a proton
accelerator and a spallation target. Hence, transmutation techniques in ADS involve high-energy neutrons, with
energies up to 2 GeV created in the proton-induced spallation process. Although a large majority of the neutrons
will be below 20 MeV, the effects on the system of the relatively small fraction at higher energies has to be
characterized. Above 200 MeV theoretical descriptions, like the intranuclear cascade model, work well and can
be used to estimate the needed cross sections, whereas experimental data are required in the energy region
between 20 and 200 MeV. Since the beginning of the decade, a large set of neutron-induced double differential
cross sections (DDX) were measured in this energy range at the quasi-monoenergetic neutron (QMN) beam line
of the The Svedberg Laboratory (TSL), Uppsala (Sweden). Data for light-ion production [4,5,6,7] at 96 MeV
QMN have been published for several target materials and are available. New measurements at 175 MeV QMN
for production of light charged particles from C, O, Si, Fe, Bi and U have been performed since 2007 and are now
under analysis. Proton induced data for production of light-ions in the 20 to 200 MeV region were more
extensively measured and are available to scientific community. In the present study we focus on the pre-