Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 49 (2016)

Cross section measurement for the spallation reaction of long-livedfission products
H. Wang,∗1 H. Otsu,∗1 H. Sakurai,∗1 D. Ahn,∗1 M. Aikawa,∗2 T. Ando,∗3 S. Araki,∗4,∗1 H. Baba,∗1 S. Chen,∗1N. Chiga,∗1 P. Doornenbal,∗1 N. Fukuda,∗1 T. Isobe,∗1 T. Ichihara,∗1 S. Kawakami,∗5,∗1 S. Kawase,∗6,∗4T. Kin,∗4 Y. Kondo,∗7,∗1 S. Koyama,∗3 S. Kubono,∗1 Y. Maeda,∗5 A. Makinaga,∗8 M. Matsushita,∗6T. Matsuzaki,∗1 S. Michimasa,∗6 S. Momiyama,∗3 S. Nagamine,∗3 T. Nakamura,∗7,∗1 K. Nakano,∗4,∗1M. Niikura,∗3 Y. Ozaki,∗7,∗1 A. T. Saito,∗7,∗1 T. Saito,∗3 H. Sato,∗1 Y. Shiga,∗1,∗9 M. Shikata,∗7,∗1 Y. Shimizu,∗1S. Shimoura,∗6 T. Sumikama,∗1 P.-A. Söderström,∗1 H. Suzuki,∗1 H. Takeda,∗1 S. Takeuchi,∗7,∗1R. Taniuchi,∗1,∗3 Y. Togano,∗7,∗1 J. Tsubota,∗7,∗1 M. Uesaka,∗1 Ya. Watanabe,∗1 Yu. Watanabe,∗4K. Wimmer,∗3,∗1 T. Yamamoto,∗5,∗1 and K. Yoshida∗1TOF, Bρ, ∆E, and the total kinetic energy in theZeroDegree spectrometer6) with the large acceptancemode. In order to cover a broad range of spallation
products, several diﬀerent Bρ settings were appliedin the ZeroDegree spectrometer. An example of theparticle identiﬁcation (PID) for the reaction residues
detected by the ZeroDegree spectrometer is shown inFig. 1. The PID plot was obtained in the 107 Pd setting
at 220 MeV/nucleon with the CD2 target.

∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9Atomic number Z

Long-lived ﬁssion products (LLFPs) are one of themajor components in the nuclear waste from nuclear
reactor systems. LLFP nuclei are highly radioactive
and have long half lives. In order to reduce the quantity of high-level radioactive waste, partitioning andtransmutation technology has been introduced in recent years1) . For LLFP transmutation, the possibility of proton-induced spallation reaction has been discussed2) ; however, experimental data are insuﬃcient.
For a systematic study on LLFP transmutation, we report on the spallation reactions for 90 Sr, 93 Zr, 107 Pd,
and 135 Cs with protons and deuterons at diﬀerent reaction energies, following the study for 90 Sr and 137 Csin 20143) .
Secondary beams were produced by the in-ﬂight ﬁssion of a 238 U primary beam at 345 MeV/nucleon ona beryllium target with a thickness of 1 mm. The
momentum acceptance of BigRIPS was set as 0.1%.
Several secondary beam settings were applied in BigRIPS and optimized for 90 Sr, 93 Zr, 107 Pd, and 135 Cs.
Note that the secondary 90 Sr and 93 Zr beams wereproduced with the same BigRIPS setting. The beamenergies for 90 Sr, 93 Zr, 107 Pd, and 135 Cs were approximately 115 MeV/nucleon in front of the secondarytargets. In addition, another setting was used for107
Pd to study the reaction at a high reaction energy of 220 MeV/nucleon. Secondary cocktail beams
were identiﬁed event-by-event via the TOF – Bρ − ∆E
method by using standard BigRIPS diagnosis detectors4) .
To induce the secondary reactions, CH2 , CD2 5) , and
12C targets were used. Their thicknesses were 179.2,
217.8, and 226.0 mg/cm2 , respectively. In order to obtain the background contribution, data were accumulated using the target holder with no target inserted.
Reaction residues were identiﬁed by measuring

107AgPreliminary
47

10100Pd4645

1444310-14241
2.125 2.15 2.175 2.2

2.225 2.25 2.275 2.3

10-2

Mass-to-charge ratio A/QFig. 1. Particle identification plot of Z versus A/Q in theZeroDegree spectrometer for the reaction residues produced from the 107 Pd beam at 220 MeV/nucleon.

The analysis of the proton- and deuteron-induced
cross sections for the LLFP nuclei is currently inprogress. This work was supported by ImPACT program of Council for Science, Technology and Innovation (Cabinet Oﬃce, Government of Japan).
References
1) IAEA Technical Reports Series No. 435 (2004).
2) A. Hermanne, J. Nucl. Sci. Technol. 39, Suppl. 2, 1202
(2002).
3) H. Wang et al. RIKEN Accel. Prog. Rep. 48, 6 (2015).
4) N. Fukuda et al. Nucl. Instrum. Methods B 317, 323(2013).
5) Y. Maeda et al. Nucl. Instr. Meth. A 490, 518 (2002).
6) T. Kubo et al. Prog. Theor. Exp. Phys. 2012, 03C003(2012).

RIKEN Nishina Center
Faculty of Science, Hokkaido University
Department of Physics, University of Tokyo
Kyushu University
University of Miyazaki
CNS, University of Tokyo
Tokyo Institute of Technology
JEin institute for fundamental science, NPO Einstein
Department of Physics, Rikkyo University-8-