I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Isotopic production of high-radiotoxic nuclide 90 Sr via proton- anddeuteron-induced reactions†
R. Matsumura,∗1,∗2 H. Otsu,∗1 H. Wang,∗1 N. Chiga,∗1 S. Kawase,∗3 K. Nakano,∗3 H. Sakurai,∗1,∗4M. Shikata,∗5 S. Takeuchi,∗5 and Y. Togano∗5 for the ImPACT-RIBF Collaboration
210(a) Y (Z = 39)(b) Sr (Z = 38)

σp Exp.
σd Exp.
σp PHITS
σd PHITS

101
010-1

Cross section σ [mb]The processing of spent fuels from nuclear power
plants is a worldwide problem. The by-products of
the reprocessing of spent fuels are high-level radioactive wastes, which contain minor actinides and ﬁssion
products. In this study, we focus on 90 Sr, which is themost radiotoxic nuclide in ﬁssion products.1) There is astrong desire to develop nuclear transmutation technology using accelerator facilities to reduce these harmful
nuclides. The simplest method is to irradiate the radioactive waste with a neutron beam. However, it is
not well known how much and into which nuclide 90 Sr
is transmuted in this reaction. Therefore, it is essential
to study the reaction cross sections to each nuclide from90
Sr in advance. From this perspective, the inverse kinematics, i.e., incident 90 Sr beam on light-particle targets,is an eﬀective method for identifying reaction productsin the forward direction.
The experiment was performed at RIBF. A secondary
beam including 90 Sr was produced by the in-ﬂight ﬁssion of 238 U at 345 MeV/nucleon on a 3-mm-thick 9 Be
production target, selected and identiﬁed event-by-event
using the TOF-Bρ-∆E method.2) Beam particles at
104 MeV/nucleon bombarded CH2 , CD2 , and C reaction targets placed at the entrance of ZDS. The residual
nuclei produced in reactions were identiﬁed in ZDS withthe same method as BigRIPS. Because the momentum
acceptance of ZDS is limited to ±3%, the experiment
was conducted using ﬁve diﬀerent momentum settings(∆ (Bρ) /Bρ = −9, −6, −3, 0, and +3%) for each target to accept a wide range of the mass-to-charge ratio
A/Q. The reaction cross sections were deduced from thenumber of incident 90 Sr nuclides, the number of residual
particles of each species, and the thickness of the target.
The backgrounds of carbon from CH2 and CD2 targets
and beam-line materials were subtracted using empty
and carbon target runs.
The data points above 1 mb were obtained with good
statistics. These were compared with the calculations
using the Particle and Heavy Ion Transport code System(phits),3) as shown in Fig. 1. The Liége Intranuclear
Cascade model (incl4.6) and the Generalized Evaporation Model (gem) were employed in the calculations. It
is observed that the calculation results were overestimated around the mass number of the projectile. Few-10210(c) Rb (Z = 37)(d) Kr (Z = 36)(e) Br (Z = 35)(f) Se (Z = 34)

1

100

10-1

10102
101
100

10-17580859075Mass number A

808590Fig. 1. Isotopic-production cross sections of proton- (circles)
and deuteron-induced (diamonds) reactions and those obtained from the phits calculations (proton for solid anddeuteron for dotted lines).

nucleon removal reactions are not interpreted properly
in incl because momentum distributions of the nuclear
surface are treated in a semiclassical way.4) In addition,even-odd staggering eﬀects appeared excessively for nuclides produced by emitting many nucleons. This may
be controlled to some extent by considering the competition between particle and γ-ray emissions, as well as
the discrete energy levels, in the gem.
In the lower energy deuteron-induced reaction, it
has been observed that the initial reaction mechanism
changes drastically due to the breakup into proton andneutron during the reaction.5) Thus, we would also liketo obtain the reaction data for 90 Sr in the near future.
References†∗1∗2∗3∗4∗5Condensed from the proceedings in JAEA-Conf 2021-001
RIKEN Nishina Center
Department of Physics, Saitama University
Department of Advanced Energy Engineering Science, Kyushu
University
Department of Physics, The University of Tokyo
Department of Physics, Tokyo Institute of Technology

1) K. Nishihara, JAEA-Data/Code 2010-012 (2010).
2) N. Fukuda et al., Nucl. Instrum. Methods Phys. Res. B
317, 323 (2013).
3) T. Sato et al., J. Nucl. Sci. Technol. 55, 684 (2018).
4) D. Mancusi et al., Phys. Rev. C 91, 034602 (2015).
5) H. Wang et al., Commun. Phys. 2, 78 (2019).

- S24 -1