RIKEN Accel. Prog. Rep. 50 (2017)

Ⅰ. HIGHLIGHTS OF THE YEAR

Spallation reaction study for the long-lived ﬁssion product 107 Pd†
H. Wang,∗1 H. Otsu,∗1 H. Sakurai,∗1 D. Ahn,∗1 M. Aikawa,∗2 T. Ando,∗3 S. Araki,∗4,∗1 S. Chen,∗1 N. Chiga,∗1P. Doornenbal,∗1 N. Fukuda,∗1 T. Isobe,∗1 S. Kawakami,∗5,∗1 S. Kawase,∗6,∗4 T. Kin,∗4 Y. Kondo,∗7,∗1S. Koyama,∗3 S. Kubono,∗1 Y. Maeda,∗5 A. Makinaga,∗8 M. Matsushita,∗6 T. Matsuzaki,∗1 S. Michimasa,∗6S. Momiyama,∗3 S. Nagamine,∗3 T. Nakamura,∗7,∗1 K. Nakano,∗4,∗1 M. Niikura,∗3 Y. Ozaki,∗7,∗1A. T. Saito,∗7,∗1 T. Saito,∗3 Y. Shiga,∗1,∗9 M. Shikata,∗7,∗1 Y. Shimizu,∗1 S. Shimoura,∗6 T. Sumikama,∗1P.-A. Söderström,∗1 H. Suzuki,∗1 H. Takeda,∗1 S. Takeuchi,∗7,∗1 R. Taniuchi,∗1,∗3 Y. Togano,∗7,∗1J. Tsubota,∗7,∗1 M. Uesaka,∗1 Ya. Watanabe,∗1 Yu. Watanabe,∗4 K. Wimmer,∗3,∗1T. Yamamoto,∗5,∗1 and K. Yoshida∗1In recent years, substantial research and development activity has been devoted to partitioning andtransmutation technology for the reduction in highlevel radioactive waste (HLW)1) as well as for resource
recycling from spent nuclear fuel. Fission products
in HLW contain useful materials, and one promising
metal is palladium. However, the palladium metal recovered from waste has a radioactive isotope, 107 Pd,
which is a typical long-lived ﬁssion product (LLFP)
with a half-life of 6.5 × 106 years2) . In considering a
possible mechanism for the reduction in the radioactivity of 107 Pd, we performed the studies for the protonand deuteron-induced spallation reaction on 107 Pd atboth 196 and 118 MeV/u using inverse kinematicstechnique.
A 238 U primary beam was accelerated to 345 MeV/uand impinged on a 1-mm thick beryllium target locatedat the entrance of the BigRIPS fragment separator3) .
Two settings were made in BigRIPS to make the 107 Pd
beams with the energies of 196 and 118 MeV/u in frontof the secondary targets, respectively. CH2 , CD2 4) and12C targets were used to induce the secondary reactions. The thicknesses for CH2 and CD2 were 179.2and 217.8 mg/cm2 , respectively. For the 12 C targets,the thicknesses were 317.2 and 226.0 mg/cm2 for 196
and 118 MeV/u, respectively. In order to measure thebackground contribution, addtional data were taken
by using the target holder with no target material inserted. Reaction residues were identiﬁed by the ZeroDegree spectrometer3) . The large acceptance mode
was used and ﬁve diﬀerent Bρ settings were applied inorder to cover a broad range of fragments.
The isotopic distribution of cross sections for thediﬀerent elements produced from 107 Pd on protons
and deuterons at both 196 and 118 MeV/u were suc†∗1∗2∗3∗4∗5∗6∗7∗8∗9Fig. 1. Isotopic production cross sections for 42 ≤ Z ≤ 47elements produced by 107 Pd on protons and deuterons
at diﬀerent reaction energies.

cessfully obtained. It was found that the protoninduced cross sections at 196 MeV/u are similar to thedeuteron-induced ones at 118 MeV/u for light products such as Ru, Tc and Mo, as shown in Fig. 1 d) - f).
The production of these light products depends on theenergy deposited. Because deuteron has two nucleons,the deuteron-induced reaction at 118 MeV/u dissipates
an energy that is similar to that of the proton-induced
reaction at 196 MeV/u in the evaporation process, resulting in a similar production. In addition, the results
are discussed by comparing them with the SPACS parameterization and the PHITS calculation including
both the intra-nuclear cascade and evaporation processes. Our data provide a design goal for the proton/deuteron ﬂux for the transmutation of 107 Pd via
spallation reactions.
This work was supported by ImPACT program ofCouncil for Science, Technology and Innovation (Cabinet Oﬃce, Government of Japan).

Condensed from the article in Prog. Theor. Exp. Phys.
2017, 021D01 (2017)
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Department of Physics, University of Tokyo
Department of Advanced Energy Engineering Science,Kyushu University
Department of Applied Physics, University of Miyazaki
CNS, University of Tokyo
Department of Physics, Tokyo Institute of Technology
JEin institute for fundamental science, NPO Einstein
Department of Physics, Rikkyo University

References
1) IAEA Technical Reports Series No. 435 (2004).
2) W. S. Yang et al., Nucl. Sci. Eng. 146, 291 (2004).
3) T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003(2012).
4) Y. Maeda et al., Nucl. Instr. Meth. A 490, 518 (2002).

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