JAEA-Conf 2021-001
INDC(JPN)-207
DOI:10.11484/jaea-conf-2021-001

Proceedings of the 2020 Symposium on Nuclear Data
November 26-27, 2020,
RIKEN Nishina Center,
RIKEN Wako Campus, Wako, Saitama, Japan(Eds.) Nobuaki IMAI and Hideaki OTSU

Nuclear Science and Engineering Center
Sector of Nuclear Science Research

March 2022
Japan Atomic Energy Agency

日本原子力研究開発機構

本レポートは国立研究開発法人日本原子力研究開発機構が不定期に発行する成果報告書です。
本レポートの転載等の著作権利用は許可が必要です。
本レポートの入手並びに成果の利用（データを含む）
は、
下記までお問い合わせ下さい。
なお、本レポートの全文は日本原子力研究開発機構ウェブサイト（https://www.jaea.go.jp）
より発信されています。
国立研究開発法人日本原子力研究開発機構〒 319-1195

JAEA イノベーションハブ

研究成果利活用課

茨城県那珂郡東海村大字白方 2 番地 4

電話 029-282-6387, Fax 029-282-5920, E-mail:ird-support@jaea.go.jp
This report is issued irregularly by Japan Atomic Energy Agency.
Reuse and reproduction of this report (including data) is required permission.
Availability and use of the results of this report, please contact
Institutional Repository and Utilization Section, JAEA Innovation Hub,Japan Atomic Energy Agency.
2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 Japan
Tel +81-29-282-6387, Fax +81-29-282-5920, E-mail:ird-support@jaea.go.jp© Japan Atomic Energy Agency, 2022

JAEA-Conf 2021-001
INDC(JPN)-207
Proceedings of the 2020 Symposium on Nuclear Data
November 26-27, 2020,
RIKEN Nishina Center,
RIKEN Wako Campus, Wako, Saitama, Japan(Eds.) Nobuaki IMAI*1 and Hideaki OTSU*2
Nuclear Science and Engineering Center, Sector of Nuclear Science Research,
Japan Atomic Energy Agency
Tokai-mura, Naka-gun, Ibaraki-ken(Received November 17, 2021)
The 2020 Symposium on Nuclear Data was held on-site at RIBF Conference Hall in RIKEN Wako
campus on November 26 to 27, 2020, combined with on-line connection conference. The symposium wasorganized by the Nuclear Data Division of the Atomic Energy Society of Japan (AESJ) in cooperation with
Sigma Investigative Advisory Committee of AESJ, Nuclear Science and Engineering Center of Japan Atomic
Energy Agency (JAEA), RIKEN Nishina Center, Center for Nuclear Study, The University of Tokyo (CNS),
KEK Wako Nuclear Science Center (WNSC), School of Science, The University of Tokyo. In the symposium,
six sessions were proposed and held: “Reactor theory and experiments” as a tutorial, “Accelerator Facilities
and Nuclear Data’’, “Deep/Machine Learning and Nuclear Physics, Application to Nuclear Data’’, “Nuclear
Medicine and Nuclear Pharmacy’’, “Fission, Heavy Ion Nuclear Spectroscopy’’, and “Nuclear Reaction Data’’as lecture and discussion sessions. In addition, recent research progress on experiments, nuclear theory,
evaluation, benchmark and applications were presented in the poster session. The total number of participants
was 119, of which 62 were on-site participants.

Each oral and poster presentation was followed by an active

question and answer session. This report consists of total 40 papers including 15 oral and 25 poster
presentations.
Keywords: Nuclear Data Symposium 2020, Experiments, Nuclear Theory, Nuclear Data Evaluation,
Benchmark Test, Nuclear Data Applications＊1 Center for Nuclear Study, The University of Tokyo(CNS)＊2 RIKEN Nishina Center
Organizers: Hideaki OTSU (Chair, RIKEN), Shin-ichro MEIGO (Vice-chair, JAEA),
Tatsuya KATABUCHI(Tokyo Tech.), Toshiya SANAMI (KEK), Atsushi KIMURA (JAEA),
Katsuhisa NISHIO (JAEA), Go CHIBA (Hokkaido Univ.), Takanori KITADA (Osaka Univ.),
Satoshi KUNIEDA (JAEA), Futoshi MINATO (JAEA), Nobuhiro SHIGYO (Kyushu Univ.),
Yukinobu WATANABE (Kyushu Univ.)ii

JAEA-Conf 2021-001
INDC(JPN)-207
2020 年度核データ研究会報告集
2020 年 11 月 26 日～27 日
理化学研究所

和光キャンパス

日本原子力研究開発機構 原子力科学研究部門（編）今井伸明*1、大津埼玉県和光市
原子力基礎工学研究センター
秀暁*2（2021 年 11 月 17 日受理）2020 年度核データ研究会は、2020 年 11 月 26 日～27 日に、埼玉県和光市にある理化学研究所
和光キャンパスの RIBF 大会議室にて、オンライン併用の形式で開催された。本研究会は、日本原
子力学会核データ部会が主催、日本原子力学会「シグマ」調査専門委員会、日本原子力研究開発
機構（原子力機構）原子力基礎工学研究センター、理化学研究所仁科加速器科学研究センター（理研仁科センター）、東京大学原子核科学研究センター（CNS）、高エネルギー加速器研究機構和光原子核科学センター（KEK-WNSC）、東京大学理学部が共催した。今回、チュートリアルとして「原子炉の理論と実験」を、講演・議論のセッションとして、「加速器施設と核データ」、「深層/機械学
習と原子核物理、核データへの応用」、「核医学、核薬学」、「核分裂、重イオン核分光」、「原子核反応データ」の 5 セッションを企画し実施した。さらに、ポスターセッションでは、実験、理論、
評価、ベンチマーク、応用等、幅広い研究内容について発表が行われた。参加者総数は 119 名でそのうち現地参加は 62 名であった。それぞれの口頭発表及びポスター発表では活発な質疑応答が行われた。本報告集は、本研究会における口頭発表 15 件、ポスター発表 25 件の論文を掲載している。
キーワード： 2020 年度核データ研究会、実験、原子核理論、核データ評価、ベンチマークテス
ト、核データ応用
原子力科学研究所：〒319-1195

茨城県那珂郡東海村大字白方 2-4＊1 東京大学原子核科学研究センター＊2 理化学研究所仁科加速器科学研究センター
2020 年度核データ研究会実行委員会：
大津秀暁（委員長、理研仁科センター）、明午伸一郎（副委員長、原子力機構）、片渕竜也（東京工業大学）、佐波俊哉（高エネルギー加速器研究機構）、木村敦（原子力機構）、西尾勝久（原子力機構）、千葉豪（北海道大学）、北田孝典（大阪大学）、国枝賢（原子力機構）、湊太志（原子力機構）、執行信寛（九州大学）、渡辺幸信（九州大学）

iiii

JAEA-Conf 2021-001

Contents
1.

2020 Symposium on Nuclear Data – Programme ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ1
Papers presented at Oral sessions

2.

Nuclear data activities in Nishina Center ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ7
Hiroyoshi SAKURAI (RIKEN Nishina Center)3.

Nuclear data study for Accelerator Driven System at J-PARC ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ13
Shin-ichiro MEIGO (J-PARC Center, JAEA)

4.

Proposal of a 1 amper class deuteron single-cell linac for nuclear transmutationꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ19
Hiroki OKUNO et al., (RIKEN Nishina Center)

5.

Unified description of the fission probability for highly excited nuclei ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ24
Hiroki IWAMOTO (J-PARC Center, JAEA)

6.

Nuclear spectroscopy at KISS ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ30
Yoshikazu HIRAYAMA et al., (KEK Wako Nuclear Science Center)7.

Production and applications of radioisotopes at RIKEN RI Beam Factory- Chemistry of new elements through diagnosis and therapy of cancer - ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ36
Hiromitsu HABA (RIKEN Nishina Center)8.

Measurements of production cross sections of medical radioisotopes via charged-particleinduced reactions ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ42
Masayuki AIKAWA (Hokkaido University)

9.

Development of radioisotopes production method by accelerator-based neutron:
activity at Kyushu University 2020 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ47
Tadahiro KIN (Kyushu Univ.)

10. Isotope production in spallation reaction of 93Zr and 93Nb induced by proton and deuteron ꞏꞏꞏꞏꞏꞏꞏ53
Keita NAKANO (J-PARC Center, JAEA)
11. Development of energy-degraded RI beam and expansion of nuclear reaction studies- Recent results obtained by the OEDO-SHARAQ system -ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ59
Shin’ichiro MICHIMASA (CNS, The Univ. of Tokyo)
12. Theoretical analysis of deuteron-induced reactions and development of deuteron nuclear databaseꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ65
Shinsuke NAKAYAMA (JAEA)
13. Roles and current status on reactor physics experiment in research reactors ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ71
Cheol Ho PYEON (KUTL, Kyoto Univ.)
14. Data-driven approaches for nuclear shell-model calculations ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ77
Noritaka SHIMIZU et al., (CNS, The Univ. of Tokyo)iii

JAEA-Conf 2021-001

15. Nuclear data generation using machine learning ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ83
Hiroki IWAMOTO (J-PARC Center, JAEA)
16. Exploration of automated data processing for mass production of nuclear data at RIBF ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ88
Shoichiro KAWASE (Kyushu Univ.)
Poster Session
17. Study of the fission path energy of U-236 using microscopic mean-field model ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ91
Kazuki FUJIO et al., (Tokyo Inst. Tech.)
18. Three ﬁssion modes in 258Md studied by Langevin model ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ97
Shoma ISHIZAKI et al., (Kindai Univ.)
19. The origin of correlation between mass and angle in quasi-fission ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ102
Shota AMONO et al., (Kindai Univ.)
20. Neutron emission during fission process by dynamical model ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ108
Ryota YAMASAKI et al., (Kindai Univ.)
21. Fission fragment distributions of neutron-rich nuclei based on Langevin calculations: r-process
nucleosynthesis simulations ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ114
Mizuki OKUBAYASHI et al., (Kindai Univ.)
22. Extended Migdal-Watson formula to evaluate background strength in binary breakup reactions ꞏꞏꞏ120
Riu NAKAMOTO et al., (Kansai Univ.)
23. Evaluation of Neutron Nuclear Data on Cobalt-59 for JENDL-5 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ126
Nobuyuki IWAMOTO (JAEA)
24. SCALE6.2 ORIGEN library produced from JENDL/AD-2017 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ132
Chikara KONNO et al., (JAEA)
25. Experimental plan for displacement damage cross sections using 120-GeV protons at Fermi National
Accelerator Laboratory ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ138
Yosuke IWAMOTO et al., (JAEA)
26. Comparison of photon spectra emitted from fuel debris using different decay data libraries ꞏꞏꞏꞏꞏꞏꞏ144
Taichi MATSUMURA et al., (JAEA)
27. Experimental program of nuclear data for accelerator-driven nuclear transmutation systemusing FFAG accelerator – First subprogram: spallation neutron measurement ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ150
Keita NAKANO et al., (JAEA)
28. Neutron filtering system for fast neutron cross-section measurement at ANNRI ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ156
Gerard Rovira LEVERONI et al., (JAEA)
29. A new method to reduce systematic uncertainties of capture cross section measurement
using a sample rotation system ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ162
Yu KODAMA et al., (Tokyo Inst. Tech.)iv

JAEA-Conf 2021-001

30. Development of a neutron beam monitor for nuclear data measurement
using spallation neutron source ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ166
Hideto NAKANO et al., (Tokyo Inst. Tech.)
31. Development of absolute epi-thermal and fast neutron flux intensity detectors for BNCT ꞏꞏꞏꞏꞏꞏꞏꞏꞏ171
Kazushi AOKI et al., (Osaka Univ.)
32. Optimization of activation detector for benchmark experiment of large-angle elastic scattering
reaction cross section by 14MeV neutrons ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ177
Ryohei TAKEHARA et al., (Osaka Univ.)
33. Nondestructive determination of water content in concrete
using Am-Be neutron source - experimental verification ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ183
Yoshihiro MIYAJI et al., (Osaka Univ.)
34. Comparison of double-differential cross sections between JENDL/PD-2016.1 and experimental datafor photo-neutron production of medium-heavy nuclei at 16.6 MeV ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ189
Kim Tuyet TRAN et al., (KEK)
35. Development of evaluation method of uncertainty of radioactivity by propagating nuclear data
covariance for clearance verification in decommissioning of nuclear power plants ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ195
Tatsuki AMITANI et al., (Tokyo Inst. Tech.)
36. Study on characteristics of neutron and γ-ray fields at compact neutron source RANS-II facility bysimulation by the PHITS code ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ201
Kenta SUGIHARA et al., (Kyushu Univ.)
37. Nuclide production cross sections of natLu target irradiated with 0.4-, 1.3-, 2.2-, 3.0-GeV protons ꞏ207
Hayato TAKESHITA et al., (Kyushu Univ.)
38. Estimation of Flux and Residual Radioactivity for the COMET Phase-I Experiment ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ213
Naoki TOKUNAGA et al., (Kyushu Univ.)
39. Measurement of neutron total cross sections of Sn-Pb alloys in solid and liquid states ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ219
Takuya UEMURA et al., (Kyoto Univ.)
40. Research for nuclear transmutation path of high-radiotoxic nuclide 90Sr via proton- and deuteroninduced reactions ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ225
Riku MATSUMURA et al., (RIKEN/Saitama Univ.)
41. Detection of gamma ray from short-lived fission products at KUCA and KURNS-LINAC ꞏꞏꞏꞏꞏꞏꞏꞏꞏ231
Yasushi NAUCHI et al., (CRIEPI)v

JAEA-Conf 2021-001

目次
1.

2020 年度核データ研究会プログラム ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 1
口頭発表論文2.

仁科センターの核データ活動 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 7
Hiroyoshi SAKURAI (理研仁科センター)

3.

J-PARC における核変換に関連した核データ研究 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 13
Shin-ichiro MEIGO (原子力機構 J-PARC センター)

4.

大強度重陽子加速器 ImPACT2017 の提案ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 19
Hiroki OKUNO 他 (理研仁科センター)

5.

高励起原子核の核分裂確率の統一的な記述 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 24
Hiroki IWAMOTO (原子力機構 J-PARC センター)

6.

KISS での核分光実験 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 30
Yoshikazu HIRAYAMA 他 (KEK 和光原子核科学センター)

7.

理研 RI ビームファクトリーにおける RI の製造と応用~新元素の探索からがんの診断、治療まで~ ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 36
Hiromitsu HABA (理研仁科センター)

8.

荷電粒子入射反応による医療用 RI 生成断面積測地実験 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 42
Masayuki AIKAWA (北海道大学)

9.

九州大学における加速器中性子源を用いた RI 製造研究の進捗 2020 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 47
Tadahiro KIN (九州大学)

10.

93

Zr 及び 93Nb に対する陽子・重陽子入射核反応からの同位体生成 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 53

Keita NAKANO (原子力機構 J-PARC センター)
11. 減速 RI ビームによる原子核物理の展開 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 59
Shin’ichiro MICHIMASA (東京大学 CNS)
12. 重陽子入射反応の理論解析と重陽子核反応データベースの開発 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 65
Shinsuke NAKAYAMA (原子力機構)
13. 研究炉における炉物理実験の役割と現状について ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 71
Cheol Ho PYEON (京都大学複合原子力科学研究所)
14. 原子核殻模型におけるデータ駆動型アプローチ ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 77
Noritaka SHIMIZU 他 (東京大学 CNS)
15. 機械学習を用いた核データの生成 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 83
Hiroki IWAMOTO (原子力機構 J-PARC センター)
16. 核データ量産化を目指した RI ビーム実験データ自動校正手法の探求 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 88
Shoichiro KAWASE (九州大学)

vi

JAEA-Conf 2021-001

ポスター発表論文
17. 微視的平均場模型を用いた U-236 の核分裂経路の研究ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 91
Kazuki FUJIO 他 (東京工業大学)
18.

258

Md 原子核による核分裂過程の理論解析 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 97

Shoma ISHIZAKI 他 (近畿大学)
19. 準核分裂における質量と角度の相関の起源 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 102
Shota AMONO 他 (近畿大学)
20. 動力学模型による核分裂過程での中性子放出 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 108
Ryota YAMASAKI 他 (近畿大学)
21. 動力学模型による中性子過剰核の核分裂計算：r プロセスシミュレーションに向けて ꞏꞏꞏꞏ 114
Mizuki OKUBAYASHI 他 (近畿大学)
22. 二体分解反応における非共鳴バックグラウンドの理論的評価 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 120
Riu NAKAMOTO 他 (関西大学)
23. JENDL-5 のためのコバルト 59 に対する中性子核データの評価 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 126
Nobuyuki IWAMOTO (原子力機構)
24. JENDL/AD-2017 から作成した SCALE6.2 の ORIGEN ライブラリ ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 132
Chikara KONNO 他 (原子力機構)
25. 米国フェルミ国立加速器研究所(FNAL) における 120 GeV 陽子を用いた弾き出し損傷断面積の実験計画 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 138
Yosuke IWAMOTO 他 (原子力機構)
26. 異なる崩壊データライブラリを用いた燃料デブリから放出される光子スペクトルの比較 144
Taichi MATSUMURA 他 (原子力機構)
27. FFAG 加速器を用いた加速器駆動核変換システムのための核データ測定: 核破砕中性子測定
ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 150
Keita NAKANO 他 (原子力機構)
28. ANNRI での高速中性子断面積測定のための中性子フィルターシステムの開発 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 156
Gerard Rovira LEVERONI 他 (原子力機構)
29. 試料回転法を用いた中性子捕獲断面積の高精度化のための新たな手法ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 162
Yu KODAMA 他 (東京工業大学)
30. 高強度中性子ビームを用いた核データ測定のための中性子検出器の開発ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 166
Hideto NAKANO 他 (東京工業大学)
31. BNCT のための絶対熱外・高速中性子束強度測定検出器の開発 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 171
Kazushi AOKI 他 (大阪大学)
32. 14MeV 中性子による大角度弾性散乱反応断面積ベンチマーク実験のための放射化検出器の最適化 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 177
Ryohei TAKEHARA 他 (大阪大学)

vii

JAEA-Conf 2021-001

33. Am-Be 中性子線源を用いたコンクリートの含水量非破壊測定法の実験的検証 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 183
Yoshihiro MIYAJI 他 (大阪大学)
34. 16.6MeV における中重核の光中性子生成に対する JENDL/PD-2016.1 と実験データの二重微
分断面積の比較 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 189
Kim Tuyet TRAN 他 (KEK)
35. 原子炉廃止措置におけるクリアランス検認に必要な放射化放射能量の核データに由来する不確かさ評価手法の開発 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 195
Tatsuki AMITANI 他 (東京工業大学)
36. PHITS による p-Li 反応を用いた中性子源 RANS-II の放射線場特性に関する研究 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 201
Kenta SUGIHARA 他 (九州大学)
37.

nat

Lu 標的に対する 0.4, 1.3, 2.2, 3.0 GeV 陽子入射による核種生成断面積 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 207

Hayato TAKESHITA 他 (九州大学)
38. COMET Phase-I 実験のための粒子線束と残留放射能の評価 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 213
Naoki TOKUNAGA 他 (九州大学)
39. 固体と液体状態での Sn-Pb 合金の全断面積測定 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 219
Takuya UEMURA 他 (京都大学)
40. 高放射性核種 90Sr の陽子及び重陽子誘起反応による核変換に向けた研究 ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 225
Riku MATSUMURA 他 (理化学研究所/埼玉大学)
41. 京都大学臨界集合体実験装置と KURNS-LINAC 施設での短寿命 FPγ 線の検出ꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏꞏ 231
Yasushi NAUCHI 他 (電力中央研究所)

viii

JAEA-Conf 2021-001

1. 2020 Symposium on Nuclear Data - ProgrammeThursday 26 November 2020
Opening/Welcome - RIBF201 (10:30-10:40)- Presenter: SANAMI Toshiya (KEK)

Facility - RIBF201 (10:40-12:20)-Conveners: MIYATAKE Hiroari (IPNS, KEK)

Time

Title

Presenter

10:40

ோ⛉ࢭࣥࢱ࣮ࡢ᰾ࢹ࣮ࢱάື/
Nuclear Data Activities in Nishina Center

11:20

J-PARC ࡟࠾ࡅࡿ᰾ኚ᥮࡟㛵㐃ࡋࡓ᰾ࢹ࣮ࢱ◊✲/Nuclear data study for Accelerator
Driven System at J-PARC
኱ᙉᗘ㔜㝧Ꮚຍ㏿ჾ ImPACT2017 ࡢᥦ᱌/Proposal of 1 A class deuteron single cell linac

11:50

SAKURAI Hiroyoshi(RIKEN Nishina Center for
Accelerator-Based Science)
IMAI Nobuaki(CNS, Univ. of Tokyo)
MEIGO Shin-ichiro(J-PARC/JAEA)OKUNO Hiroki(RIKEN Nishina &enter for$ccelerator-%ased 6cience)

Lunch - RIBF201 (12:20-13:30)
NuclearPhysics1 - RIBF201 (13:30-15:00)-Conveners: Aritomo, Yoshihiro (Kindai University)

Time

13:30

Title

Presenter

14:00

KISS ࡛ࡢ᰾ศගᐇ㦂/
Nuclear spectroscopy at KISSIWAMOTO Hiroki(JAEA)MEIGO Shin-ichiro(J-PARC/JAEA)HIRAYAMA Yoshikazu(IPNS, KEK)

14:30

JAEA ࢱࣥࢹ࣒ຍ㏿ჾ࡛ࡢ࢔࢖ࣥࢫࢱ࢖ࢽ࣒࢘ࢆ
⏝࠸ࡓ᰾ศ⿣ᐇ㦂

HIROSE Kentaro(JAEA)

㧗ບ㉳ཎᏊ᰾ࡢ᰾ศ⿣☜⋡ࡢ⤫୍ⓗ࡞グ㏙/
Unified description of the fission probability forhighly excited nuclei

Coffee - RIBF201 (15:00-15:20)
Conference Photo - RIBF201 (15:00-15:10)


-1-

JAEA-Conf 2021-001

NuclearMedicine - RIBF201 (15:20-16:50)-Conveners: MINATO Futoshi (JAEA)

Time

15:20

15:50

16:20

Title

Presenter⌮◊ RI ࣅ࣮࣒ࣇ࢓ࢡࢺ࣮ࣜ࡟࠾ࡅࡿ RI ࡢ〇㐀࡜ᛂ⏝ 㹼᪂ඖ⣲ࡢ᥈⣴࠿ࡽࡀࢇࡢデ᩿࣭἞⒪ࡲ࡛㹼/
Production and Applications of Radioisotopes at RIKEN
RI Beam Factory - Search for New Elements throughDiagnosis and Therapy of CancerⲴ㟁⢏Ꮚධᑕ཯ᛂ࡟ࡼࡿ་⒪⏝ RI ⏕ᡂ᩿㠃✚ ᐃᐇ㦂/
Measurements of production cross sections of medical
radioisotopes via charged-particle induced reactions஑ᕞ኱Ꮫ࡟࠾ࡅࡿຍ㏿ჾ୰ᛶᏊ※ࢆ⏝࠸ࡓ RI 〇㐀◊✲ࡢ㐍ᤖ 2020/
Development of Radioisotopes Production Method byAccelerator-based Neutron: Activity at Kyushu University
2020

HABA Hiromitsu(Nishina Center for
Accelerator-Based Science,
RIKEN)AIKAWA Masayuki(Hokkaido University)
KINTadahiro(Kyushu University)

Poster - RIBF201 (16:50-20:30)
Title

Presenterᚤどⓗᖹᆒሙᶍᆺࢆ⏝࠸ࡓ U-236 ࡢ᰾ศ⿣⤒㊰ࡢ◊✲/ Study ofthe fission path energy of U-236 using microscopic mean-fieldmodel
258Md ཎᏊ᰾࡟ࡼࡿ᰾ศ⿣㐣⛬ࡢ⌮ㄽゎᯒ/
Theoritical analysis of the fission process by 258Md‽᰾ศ⿣࡟࠾ࡅࡿ㉁㔞࡜ゅᗘࡢ┦㛵ࡢ㉳※/The origin of correlation between mass and angle in quasifissionືຊᏛᶍᆺ࡟ࡼࡿ᰾ศ⿣㐣⛬࡛ࡢ୰ᛶᏊᨺฟ/Neutron emission during fission process by dynamical model

FUJIO Kazuki(Tokyo Institute ofTechnology)ືຊᏛᶍᆺ࡟ࡼࡿ୰ᛶᏊ㐣๫᰾ࡢ᰾ศ⿣ィ⟬㸸r ࣉࣟࢭࢫࢩ࣑ࣗ
࣮ࣞࢩࣙࣥ࡟ྥࡅ࡚/The fission fragments of neutron-rich nuclei by the Langevinmethod toward application to r-process calculations஧యศゎ཯ᛂ࡟࠾ࡅࡿ㠀ඹ㬆ࣂࢵࢡࢢࣛ࢘ࣥࢻࡢ⌮ㄽⓗホ౯/Theoretical evaluation of non-resonant background strength inbinary breakup reaction

OKUBAYASHI Mizuki(Kindai University)

JENDL-5 ࡢࡓࡵࡢࢥࣂࣝࢺ 59 ࡟ᑐࡍࡿ୰ᛶᏊ᰾ࢹ࣮ࢱࡢホ౯/
Evaluation of Neutron Nuclear Data on Cobalt-59 for JENDL-5,:$0272NREX\XNL(JAEA)JENDL/AD-2017 ࠿ࡽసᡂࡋࡓ SCALE6.2 ࡢ ORIGEN ࣛ࢖ࣈࣛ
ࣜ/
SCALE6.2 ORIGEN library produced from JENDL/AD-2017

KONNO Chikara(JAEA)-2-

ISHIZAKI Shoma(Kindai University)
AMANO Shota(Kindai University)
YAMASAKI Ryota(Kindai University)

NAKAMOTO Riu(Kansai University)

JAEA-Conf 2021-001⡿ᅜࣇ࢙࣑ࣝᅜ❧ຍ㏿ჾ◊✲ᡤ(FNAL) ࡟࠾ࡅࡿ 120 GeV 㝧Ꮚࢆ⏝࠸ࡓᙎࡁฟࡋᦆയ᩿㠃✚ࡢᐇ㦂ィ⏬/Experimental plan for displacement damage cross sections
using 120-GeV protons at FNAL
␗࡞ࡿᔂቯࢹ࣮ࢱࣛ࢖ࣈࣛࣜࢆ⏝࠸ࡓ⇞ᩱࢹࣈࣜ࠿ࡽᨺฟࡉࢀ
ࡿගᏊࢫ࣌ࢡࢺࣝࡢẚ㍑/
Comparison of photon spectra emitted from fuel debris using
different decay data libraries
FFAG ຍ㏿ჾࢆ⏝࠸ࡓຍ㏿ჾ㥑ື᰾ኚ᥮ࢩࢫࢸ࣒ࡢࡓࡵࡢ᰾ࢹ
࣮ࢱ ᐃ: ᰾◚○୰ᛶᏊ ᐃ/
Experimental program of nuclear data for accelerator-driven
nuclear transmutation system using FFAG accelerator – First
subprogram: spallation neutron measurement
ANNRI ࡛ࡢ㧗㏿୰ᛶᏊ᩿㠃✚ ᐃࡢࡓࡵࡢ୰ᛶᏊࣇ࢕ࣝࢱ࣮ࢩ
ࢫࢸ࣒ࡢ㛤Ⓨ/
Neutron Filtering System for Fast Neutron Cross-Section
Measurement at ANNRI
ヨᩱᅇ㌿ἲࢆ⏝࠸ࡓ୰ᛶᏊᤕ⋓᩿㠃✚ࡢ㧗⢭ᗘ໬ࡢࡓࡵࡢ᪂ࡓ࡞ᡭἲ/A New Method to Reduce Systematic Uncertainties of Capture
Cross Section Measurement Using a Sample Rotation System㧗ᙉᗘ୰ᛶᏊࣅ࣮࣒ࢆ⏝࠸ࡓ᰾ࢹ࣮ࢱ ᐃࡢࡓࡵࡢ୰ᛶᏊ᳨ฟჾࡢ㛤Ⓨ/
Development of a neutron detector for nuclear datameasurement using high-intensity
neutron beam
BNCT ࡢࡓࡵࡢ⤯ᑐ⇕እ࣭㧗㏿୰ᛶᏊ᮰ᙉᗘ ᐃ᳨ฟჾࡢ㛤Ⓨ/
Development of Absolute Epi-thermal and Fast Neutron Flux
Intensity Detectors for BNCTIWAMOTO Yosuke(JAEA)

14MeV ୰ᛶᏊ࡟ࡼࡿ኱ゅᗘᙎᛶᩓ஘཯ᛂ᩿㠃✚࣋ࣥࢳ࣐࣮ࢡᐇ
㦂ࡢࡓࡵࡢᨺᑕ໬᳨ฟჾࡢ᭱㐺໬/
Optimization of Activation Detector for Benchmark Experiment ofLarge-angle Elastic Scattering Reaction Cross Section by
14MeV Neutrons
Am-Be ୰ᛶᏊ⥺※ࢆ⏝࠸ࡓࢥࣥࢡ࣮ࣜࢺࡢྵỈ㔞㠀◚ቯ ᐃἲࡢᐇ㦂ⓗ᳨ド/Nondestructive Determination of Water Content in Concrete
Using Am-Be Neutron Source - Experimental Verification 16.6MeV ࡟࠾ࡅࡿ୰㔜᰾ࡢග୰ᛶᏊ⏕ᡂ࡟ᑐࡍࡿ JENDL/PD2016.1 ࡜ᐇ㦂ࢹ࣮ࢱࡢ஧㔜ᚤศ᩿㠃✚ࡢẚ㍑/
Comparison of double-differential cross sections between
JENDL/PD-2016.1 and experimental data for photo-neutron
production of medium-heavy nuclei at 16.6 MeV
ཎᏊ⅔ᗫṆᥐ⨨࡟࠾ࡅࡿࢡࣜ࢔ࣛࣥࢫ᳨ㄆ࡟ᚲせ࡞ᨺᑕ໬ᨺᑕ
⬟㔞ࡢ᰾ࢹ࣮ࢱ࡟⏤᮶ࡍࡿ୙☜࠿ࡉホ౯ᡭἲࡢ㛤Ⓨ/
Development of Evaluation Method of Uncertainty ofRadioactivity by Propagating Nuclear Data Covariance for
Clearance Verification in Decommissioning of Nuclear Power
Plants7$.(+$5$R\RKHL(Osaka Univ.)-3-

MATSUMURA Taichi(JAEA)NAKANO Keita(JAEA)ROVIRA LEVERONI Gerard(JAEA)

KODAMA Yu(Tokyo Institute of Technology)

NAKANO Hideto(Tokyo Institute of Technology)

AOKI Kazushi(Osaka Univ.)

MIYAJIYoshihiro
Yoshihiro
MIYAJI(OsakaUniv.)
Univ.)(OsakaTRAN Kim Tuyet(SOKENDAI/KEK)

AMITANI Tatsuki(Tokyo Institute of Technology)

JAEA-Conf 2021-001

PHITS ࡟ࡼࡿ p-Li ཯ᛂࢆ⏝࠸ࡓ୰ᛶᏊ※ RANS-II ࡢᨺᑕ⥺ሙ≉ᛶ࡟㛵ࡍࡿ◊✲/
Study on characteristics of neutron and γ-ray fields at compact
neutron source RANS-II facility by simulation by the PHITS code
natLu ᶆⓗ࡟ᑐࡍࡿ 0.4, 1.3, 2.2, 3.0 GeV 㝧Ꮚධᑕ࡟ࡼࡿ᰾✀⏕ᡂ᩿㠃✚/
Nuclide production cross sections of natLu target irradiated with
0.4-, 1.3-, 2.2-, 3.0-GeV protons
COMET Phase-I ᐇ㦂ࡢࡓࡵࡢ⢏Ꮚ⥺᮰࡜ṧ␃ᨺᑕ⬟ࡢホ౯/Estimation of Flux and Residual Radioactivity for the COMET
Phase-I Experimentᅛయ࡜ᾮయ≧ែ࡛ࡢ Sn-Pb ྜ㔠ࡢ඲᩿㠃✚ ᐃ/
Measurement of neutron total cross sections of Sn-Pb alloys insolid and liquid states

SUGIHARA Kenta(RIKEN Nishina Center,
Kyushu University)㧗ᨺᑕᛶ᰾✀ 90Sr ࡢ㝧Ꮚཬࡧ㔜㝧Ꮚㄏ㉳཯ᛂ࡟ࡼࡿ᰾ኚ᥮࡟ྥ
ࡅࡓ◊✲/Research for nuclear transmutation of high-radiotoxic nuclide
90Sr via proton- and deuteron-induced reactions
natLu(p,xn)࠾ࡼࡧ natLu(d,xn)཯ᛂ࡟ࡼࡿ 175Hf ࡢ⏕ᡂ᩿㠃✚ࡢᐃ/Production cross sections of 175Hf in the natLu(p,xn) andnatLu(d,xn) reactionsி㒔኱Ꮫ⮫⏺㞟ྜయᐇ㦂⿦⨨࡜ KURNS-LINAC ᪋タ࡛ࡢ▷ᑑ࿨FPγ ⥺ࡢ᳨ฟ/Detection of Gamma Ray from Sort-Lived Fission Products at
KUCA and KURNS-LINAC

MATSUMURA Riku
(Saitama University)

,


-4-

TAKESHITA Hayato(Kyushu University)

TOKUNAGA Naoki(Kyushu University)
UEMURA Takuya(Kyoto University)

KOMORI Yukiko(RIKEN Nishina Center)

NAUCHI Yasushi(Central Research Institute ofElectric Power Industry)JAEA-Conf 2021-001

Friday 27 November 2020
NuclearPhysics2 - RIBF201 (09:00-10:30)-Conveners: Terada Kazushi (Kyoto University)

Time

09:00

09:30

10:00

Title

Presenter

93Zr ཬࡧ 93Nb ࡟ᑐࡍࡿ㝧Ꮚ࣭㔜㝧Ꮚධᑕ᰾◚○཯ᛂ࠿ࡽࡢྠ఩య⏕ᡂ/
Isotope production in spallation reaction of 93Zr
and 93Nb induced by proton and deuteronῶ㏿ RI ࣅ࣮࣒࡟ࡼࡿཎᏊ᰾≀⌮ࡢᒎ㛤/Development of energy-degraded RI beam andexpansion of nuclear reaction studies㔜㝧Ꮚධᑕ཯ᛂࡢ⌮ㄽゎᯒ࡜㔜㝧Ꮚ᰾཯ᛂࢹ࣮ࢱ
࣮࣋ࢫࡢ㛤Ⓨ/
Theoretical analysis of deuteron-induced reactions
and development of deuteron nuclear database

NAKANO Keita(JAEA)MICHIMASA Shin'ichiro(CNS, 7KHUniv. of Tokyo)
NAKAYAMA Shinsuke(JAEA)

Coffee - RIBF201 (10:30-10:50)
Tutorial - RIBF201 (10:50-12:20)-Conveners: Chiba Go (Hokkaido University)

Time

10:50
11:40

Title

PresenterཎᏊ⅔⌮ㄽࡢධ㛛/
Introduction to Nuclear Reactor Theory

ENDO Tomohiro(Nagoya University)◊✲⅔࡟࠾ࡅࡿ⅔≀⌮ᐇ㦂ࡢᙺ๭࡜⌧≧࡟ࡘ࠸࡚/Roles and current status of reactor physics
experiment in research reactors

PYEON Cheol Ho(Kyoto University)

Lunch - RIBF201 (12:20-13:30)
DeepLearning - RIBF201 (13:30-15:30)-Conveners: Hiroyuki Koura

Time

13:30

Title

Presenter῝ᒙᏛ⩦࡜ᇶ♏⛉Ꮫ◊✲࡬ࡢᛂ⏝࡟ࡘ࠸࡚/Deep Learning for Basic Science

TAKI Masato(Rikkyo University)

14:00ཎᏊ᰾Ẇᶍᆺ࡟࠾ࡅࡿࢹ࣮ࢱ㥑ືᆺ࢔ࣉ࣮ࣟࢳ/Data-driven approaches for nuclear shell-model
calculations

SHIMIZU Noritaka(7KHUniversity of Tokyo)

14:30

ᶵᲔᏛ⩦ࢆ⏝࠸ࡓ᰾ࢹ࣮ࢱࡢ⏕ᡂ/
Nuclear data generation using machine learning

IWAMOTO Hiroki(JAEA)

-5-

JAEA-Conf 2021-001

15:00

᰾ࢹ࣮ࢱ㔞⏘໬ࢆ┠ᣦࡋࡓ RI ࣅ࣮࣒ᐇ㦂ࢹ࣮ࢱ⮬
ື㍑ṇᡭἲࡢ᥈ồ/
Exploration of automated data processing formass production of nuclear data at RIBF

KAWASE Shoichiro(Kyushu University)

Closing Remarks - RIBF201 (15:30-16:00)-Presenters: SANAMI Toshiya (KEK); WATANABE Yukinobu (Kyushu University)

FacilityTour - RIBF201 (16:00-17:30)

-6-

JAEA-Conf 2021-001

 Nuclear Data Activities in Nishina Center
Hiroyoshi SAKURAI †RIKEN Nishina Center for Accelerator-Based Science2-1 Hirosawa, Wako, Saitama, 351-0198, Japan†
Email: sakurai@ribf.riken.jp

The nuclear data activities at the heavy-ion accelerator facility Radioactive Isotope Beam Factory”operatedbyRIKENNishinaCenterforAccelerator-BasedScienceareintroduced. Theactivities
extending throughoutawholeofnuclearchartarecategorized intonuclearphysics andnuclearengineering. For each of them, present status is reported and special emphasis would be given to recent
highlights selected. Future directions of the nuclear data programs are presented.

1 IntroductionIn 2006, RIKEN Nishina Center for Accelerator-Based Science (RNC) was established to organize theworld-prestigiousheavyionacceleratorfacilityRadioactiveIsotopeBeamFactory(RIBF)”[1].TheRIBF
facilitywasconstructedasoneofthethird-generationin-ﬂightfacilitiestoaimatthreegoals:1)todiscover
newquantumphenomenaunderalargeisospinasymmetrythroughinvestigatingnuclearstructureinvery
neutron-rich nuclei, 2) to elucidate the r-process path in explosive processes of the universe, and 3) to
developnewappliedsciencesbasedonhighenergyradioactiveisotope(RI)beam.SincetheRIBFstarted
operational in 2007, multitudes of data on the nuclear structure and reactions have been produced with
RIBFasanucleardatafactory.
TheRIBFfacilitydeliversavarietyofheavyionbeamsofhydrogentouraniumatanenergyrangingwidely from several MeV/u to 345 MeV/u, and unique experimental devices and spectrometers are
equipped [2]. As shown in Fig. 1, beams accelerated at three cyclotrons (AVF, RRC and SRC) and one
liniac (SRILAC) serve experimental programs at gas-ﬁlled recoil separators (GARIS-II, III), in-gas-cell
laserionsource(KISS),andin-ﬂightseparators(CRIB,RIPS,BigRIPS).RIbeamsproducedatBigRIPS
are delivered to three spectrometers (ZeroDegree, SAMURAI and SHARAQ), and to a storage ring for
mass measurement (Rare-RI Ring). The facility has a setup of SCRIT to realize electron-RI scattering,
where RIs are produced at an Isotope Separator On-Line (ISOL) based on electron induced-ﬁssion.
Nuclear data activities at the RIBF facility have extended throughout a whole of the nuclear chartfrom a light-mass to a super-heavy region and from stable to proton- and neutron-rich nuclei. The
data are in general categorized into reaction data and structure data. The reaction data at RIBF stemfrom RI productions, secondary reactions with RI beams, and electron-RI scattering. Concerning thestructure data, nuclear properties of ground and excited states are obtained at RIBF via spectroscopy
of mass, decay, missing-mass, invariant-mass and in-beam gamma. The data produced at the RIBF
have been compiled and evaluated by the world nuclear database activities guided by IAEA. JCPRG in
Hokkaido University and RNC have established an MoU to cooperate together in nuclear data activities
of charged-particle induced reactions.
Inthisarticle,thenucleardataactivitiesatRIBFarereviewed. Theactivitiesaredividedintonuclear
physicsandnuclearengineering,andforeachofthem,presentstatusandrecenthighlightsarepresented.
Future directions of the nuclear data activities at RIBF are discussed.

2 Nuclear Physics
Inthissection,veryrecenthighlightsandactivitiesinnuclearphysicswithRIBFaredemonstrated. First,
the activities of superheavy element physics are introduced and second, recent achievements in studying

7-7-

JAEA-Conf 2021-001

Figure 1: Facility layout of RIBF.
exotic nuclei are shown.

2.1 Superheavy ElementOneofthegreatachievementsatRIBFisdiscoveryofElement113,whichwasnamedNihonium”byK.
Morita and his colleagues in 2016. The superheavy element was produced and identiﬁed in three events
observed in 2004–2012. The last event in 2012 [3] showed successive alpha-decay down to 254 Md, and
gave a direct evidence that 278 Nh was produced.
The 278 NhisotopewasmadeviathecoldfusionreactionwithcombinationoftheRILAClinearacceleratorandthegas-ﬁlledrecoilseparatorGARIS.Toconductfurtherproductionofsuperheavyelements,
anewseparatorGARIS-II[4]wasdesignedandconstructedtoachieveahighertransmissioneﬃciencyinthe hot fusion reaction, compared with that of GARIS. A KEK-RIKEN collaboration has been formed
to measure mass of heavy elements via MR-TOF technique at GARIS-II, and has published results, for
example, around Z=100 [5]. The GARIS-II spectrometer was moved to accept heavy-ion beams from
RRC in 2017.
A new setup for production of new elements has been established. First, the intensity and energy
upgrade of the RILAC was completed in 2020 with 28GHz ECR ion source [6] and super conducting
rf-cavities [7], both newly installed. GARIS-III was newly constructed and installed to be coupled withthe upgraded RILAC. GARIS-III was designed to have the same performances as of GARIS-II. A newprogram to search for Element 119 started at the end of 2020.

2.2 Exotic Nuclei
Exotic nuclei with a large isospin-asymmetry have been produced as intense RI beams at RIBF. Highenergy heavy-ion beams accelerated at SRC are converted to unstable nuclei at production targets via
projectile-fragmentation or ﬁssion reactions and the nuclei of interest are collected and separated at
BigRIPS, then the RI beams are delivered to several experimental devices.
Since2007,morethan140newisotopeshavebeendiscoveredatBigRIPS.Oneofrecenthighlightsis
discovery of the particle stability of 60 Ca and other neighboring nuclei [8]. The neutron-drip line for theﬂuorine and neon isotopes was determined in 2019 [9], and the drip line has been extended for the ﬁrst
time in 20 years.
Shellevolutionhasbeeninvestigatedviain-beamgammaspectroscopy,decay-spectroscopyandmassspectroscopy. Very selected highlights are discovery of new magicity at N =34 in the neutron-rich Caisotopes [10], double magicity of 78 Ni [11], and exotic structure in 40 Mg [12]. Shell evolution and shape

8-8-

JAEA-Conf 2021-001

deformation was found in 75 Cu by employing a new technique of spin-aligned RI beams [13]. Mass
spectroscopy of neutron-rich Ca and Ti isotopes conﬁrmed the magicity of N =34 [14], and discovered adeformation region in the neutron-rich Ti isotopes [15]. Neuton-rich nuclei with respect to the double
magic nucleus 132 Sn have been investigated and all the data obtained so far indicate large shell gaps either
at Z=50 or at N =82, and no magicity loss has been found. In 2020, the ﬁrst high-resolution gamma
spectroscopy was carried out with germanium tracking detectors under the HiCARI collaboration.
RIBF has published bunch of half-life data for neutron-rich nuclei [16, 17, 18], which are necessary tounderstand the r-process nucleosynthesis. The abundance calculation with the new data could reproduce
reasonably the r-process abundance pattern, especially for A∼120 region and A∼140-160 region. The
third data set [18] has striking and large drops of half-lives at N =97 for Ce, Pr, Nd and Sm and at
N =105 for Eu, Gd, Tb and Dy, and has a direct impact in the r-process abundance calculations aﬀecting
almost all mass numbers between A=150 and 170.
The new form of nuclei have been found such as two deformed halo-nuclei, 31 Ne [19, 20] and 37 Mg [21,22], and two-neutron halo in 29 F [23], all of which are located in the deformation region of 9≤Z≤12
and 20≤N ≤28. Exotic particle-unbound nuclei have been investigated in a light neutron-rich region.
Candidate of ‘tetra’ neutron state was observed with missing mass spectroscopy [24]. This work has
made a great trigger to investigate very exotic few-body systems such as 7 H. Invariant mass spectroscopy
successfully observed the ground state and 2+ state in 26 O [25], and 26 O was found to be well-deformed
and a barely unbound system beyond the drip line.
Equation-of-State (EOS) in nuclear matter, especially at a high density and high isospin asymmetry,has been highly desired to understand the structure of neutron-stars and to analyze gravitation wave.
When the nuclear matter density is increased, many-body forces such as three nucleon force (3NF)
become signiﬁcant in EOS. At RIBF, polarized deuteron + proton elastic scattering has been studied toobtain T = 1/2 channel of 3NF [26]. The other works for EOS have been conducted such as a study ofGamow-Teller resonance in 132 Sn [27].

3

Nuclear Engineering

The incident of Fukushima Dai-ichi Unit in 2011 has given a trigger to nuclear physicists in Japan to consider possible contributions to nuclear engineering. In 2014, a reaction study with intense 137 Cs and 90 Srbeams at RIBF was conducted to seek for a transmutation path way to reduce radioactive waste [28, 29].
This experiment initiated a large project, which was awarded ImPACT grant [30] running in ﬁscal year of
2014-2018. The project focused accelerator-based transmutation for long-lived ﬁssion products (LLFPs)
in high-level radioactive waste, and conducted research and development for partitioning, reaction data
and theory, reaction database, and accelerator system. In the ImPACT project, RIKEN was in charge ofstudies for nuclear reactions, and also of accelerator developments.
As shown in Fig. 2, based on intense RI beams available at RIBF, a variety of reaction studies wereorganized with LLFPs such as 107 Pd and 93 Zr [31, 32, 33, 34, 35]. So called ‘inverse kinematics’ technique
was employed to obtain spallation reaction data. The advantage of the inverse kinematics technique gives
clear particle identiﬁcation for reaction products, and easy control of RI beam energies for study of energydependence. In addition, we do not have to prepare RI targets but stable-isotope targets such as protons
and deuterons. All these advantages of inverse kinematics lead to nice quality of the data at RIBF.
The reaction study in the ImPACT program was managed under a large domestic collaboration with
University of Tokyo, Tokyo Institute of Technology, Kyushu University, Miyazaki University and RIKEN.
All the major spectrometers at RIBF, ZeroDegree, SAMURAI and SHARAQ were utilized to identify
and analyze reaction products. Zerodegree is suitable for inclusive measurements with relatively heavy
fragments. SAMURAI has a wide acceptance in both momentum and scattering angle, hence exclusive
measurements were performed to detect reaction products as well as neutrons in projectile frame. At
SHARAQ spectrometer, CNS, University of Tokyo and RIKEN worked together to develop an eﬃcient
deceleration scheme for RI beams. Study at low energy reactions at ∼20 MeV/u [36, 37], and a new
device ”OEDO” was installed in the SHARAQ beam line. At the new setup, incomplete fusion reaction
data and (d, p) reaction data were obtained with combination of OEDO and SHARAQ, and the data arebeing prepared for submission.
All these data are very useful to stimulate theoretical works and to improve simulation tools. The
reaction data were evaluated by the JAEA nuclear data group and a new data library ‘JENDL/ImPACT-

9-9-

JAEA-Conf 2021-001ĞƌŽĞŐƌĞĞ
Ő^ƉĞĐƚƌŽŵĞƚĞƌ
Ɖ^ƉĂůůĂƚŝŽŶ
ϭϬϳWĚ ΛϱϬ͕ϭϬϬ͕ϮϬϬDĞsͬƵϵϯƌΛϱϬ͕ϭϬϬDĞsͬƵϳϵ^ĞΛϮϬϬDĞsͬƵϭϮϲ^ŶΛϮϬϬDĞsͬƵ^ƵƉĞƌŽŶĚƵĐƚŝŶŐZŝŶŐǇĐůŽƚƌŽŶ

^DhZ/^ƉĞĐƚƌŽŵĞƚĞƌ
^ƉĂůůĂƚŝŽŶ
ϳϵ^Ğ͕ϵϯƌΛϭϭϬ͕ϮϬϬDĞsͬƵŽƵůŽŵďďƌĞĂŬƵƉ;J͕ŶͿϳϵ͕ϴϬ^Ğ͕ϵϯ͕ϵϰƌΛϮϬϬDĞsͬƵ<сϮϲϬϬDĞshƌĂŶŝƵŵďĞĂŵʤϯϰϱDĞsͬƵʥ

>>&WďĞĂŵƐ

KKĞǀŝĐĞ

DĂƌĐŚϮϬϭϳĐŽŵƉůĞƚĞĚ

ϭϬϳWĚ͕ϵϯƌ͕ϳϵ^Ğ͕ϭϯϱƐĞƌǇůůŝƵŵƚĂƌŐĞƚ

/ŶͲĨůŝŐŚƚƐĞƉĂƌĂƚŽƌŝŐZ/W^/ŶĐŽŵƉůĞƚĞĨƵƐŝŽŶƌĞĂĐƚŝŽŶ
ϭϬϳWĚ ΛϮϬ͕ϯϬDĞsͬƵϵϯƌΛϮϬ͕ϯϬDĞsͬƵEĞƵƚƌŽŶͲĐĂƉƚƵƌĞ ;Ŷ͕JͿ
dƌŽũĂŶ ŚŽƌƐĞ ŵĞƚŚŽĚ ϳϳ͕ϳϵ^Ğ;Ě͕ƉͿΛϮϬDĞsͬƵ

Figure 2: Reaction study for long-lived ﬁssion products at RIBF in 2014–2017.
2018’ for proton- and neutron-induced reactions up to 200 MeV/u was released [38]. The data libraryhas been a package of the PHITS simulator [39].
The improved simulation tool gave a strategy for LLFP transmutation, and a new transmutation
scheme with high-energy neutron produced via deuteron breakup was considered, and a new accelerator
scheme delivering 1-ampere deuteron beams has been proposed [40]. In addition, the RIKEN accelerator
staﬀ members successfully developed a quarter-wave superconducting RF cavity for eﬃcient accelerationof charged particles [41]. The other transmutation scheme was discussed with 14 MeV neutron produced
via muon catalyzed fusion with MERIT [42], that requires negative pion production cross sections with
deuteron beams for further designing works.

4

Summary and Outlook

In summary, it would be emphasized that the RIBF facility is the nuclear data factory. Since 2007,
RIBF has produced bunch of data of nuclear reaction and structure in both nuclear physics and nuclear
engineering, especially for shell evolution, the r-process path, new form of nuclei, EOS and high-level
radioactive waste problem.
Unique features of RIBF would be demonstrated to give multitudes of opportunities adapting any
demands of nuclear data. RIBF delivers a variety of heavy-ion beams of hydrogen to uranium. Energyof the beams ranges several MeV/u to 345 MeV/u to be employed for any types of reactions. The
beams are intense enough to conduct reaction studies and to artiﬁcially produce RIs from light andsuperheavy elements. These powerful beams have been utilized to produce secondary beams of RIs.
Several experimental devices serve to separate, identify and analyze reaction products.
In future, the nuclear engineering community would be further encouraged to promote the LLFP
reaction data project, and if necessary, to study ﬁssion reaction and precise decay measurement for decay
heat and neutron-emission probability necessary in designing nuclear reactors, by utilizing RI beams. The
RIBF intensity upgrade is planned by installing new charge stripper rings [43]. More intense heavy-ion
beams would create more opportunities for reaction study such as (d, p) reaction with low energy RI
beams to study neutron-capture reaction, and for reaction study with minor actinides.

- 10
10 -

JAEA-Conf 2021-001

References[1] Yano, Y., The RIKEN RI Beam Factory Project: A status report, Nucl. Instrum. Methods Phys.
Res., Sect. B 261 (2007) 1009
[2] Introduction to RI Beam Factory and Users’ Information,
https://www.nishina.riken.jp/ribf/index.html BDDFTTFE [3] Morita, K., Morimoto, K., Kaji, D., et al., New result in the production and decay of an isotope,
278
113, of the 113th element, JPSJ 81 (2012) 103201
[4]Kaji,D.,Morimoto,K.,Sato,N.,etal.,Gas-ﬁlledrecoilionseparatorGARIS-II,Nucl.Instrum.
Methods Phys. Res., Sect. B 317 (2013) 311[5] Ito, Y., Schury, P., Wada, M., et al., First Direct Mass Measurements of Nuclides around Z=100
withaMultireﬂectionTime-of-FlightMassSpectrographPRL120(2018)152501
[6] Nagatomo,T.,Higurashi,J.,Ohnishi,A.,etal.,NEW28-GHzSUPERCONDUCTINGELECTRONCYCLOTRONRESONANCEIONSOURCEFORSYNTHESIZINGSUPER-HEAVYELEMENTS
WITH Z >118 Prof. of 23th Int. Workshop on ECR Ion Sources (ECRIS2018), TUA3, 53 (2018)
[7] Yamada, K., Dantsuka, T., Imao, H., et al., Construction of Superconducting Linac Boosterfor Heavy-Ion Linac at RIKEN Nishina Center, Prof. 19th Int. Conf. on RF Superconductivity(SRF2019), TUP037, 502 (2019).
[8] Tarasov, O.B., Ahn, D.S., Bazin, D., et al., Discovery of 60 Ca and Implications For the Stability of
70Ca, Phys. Rev. Lett. 121 (2018) 022501
[9]  Ahn, D.S., Fukuda, N., Geissel, H., et al., Location of the Neutron Dripline at Fluorine and Neon,
Phys. Rev. Lett. 123 (2019) 212501
[10] Steppenbeck, D., Takeuchi, S., Aoi, N., et al., Evidence for a new nuclear emagic numberf from thelevel structure of 54Ca Nature 502 (2013) 207[11] Taniuchi, R., Santamaria, C., Doornenbal, P., et al., 78Ni revealed as a doubly magic stronghold
against nuclear deformation Nature 569 (2019) 53
[12] Crawford,H.L.,Fallon,P.,Macchiavelli,O.,et al.,FirstSpectroscopyoftheNearDrip-lineNucleus
40
Mg, Phys. Rev. Lett. 122 (2019) 052501
[13] IchikawaY.,Nishibata,H.,Tsunoda,Y.,et al.,Interplaybetweennuclearshellevolutionandshapedeformation revealed by the magnetic moment of 75Cu Nature Physics 15 (2019) 321[14] Michimasa, S., Kobayashi, M., Kiyokawa, Y., et al., Magic Nature of Neutrons in 54Ca: First Mass
Measurements of 55−57 Ca, Phys. Rev. Lett. 121 (2018) 022506
[15] Michimasa, S., et al., Mapping of a New Deformation Region around 62Ti, Phys. Rev. Lett. 125(2020) 122501
[16]Nishimura,S.,Li,Z.,Watanabe,H.,etal.,β-DecayHalf-LivesofVeryNeutron-RichKrtoTc
Isotopes on the Boundary of the r-Process Path: An Indication of Fast r-Matter Flow, Phys. Rev.
Lett. 106 (2011) 052502
[17] Lorusso,G.,Nishimura,S.,Xu,Z.Y.,etal.,β-DecayHalf-Livesof110Neutron-RichNucleiacrossthe
N =82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process,
Phys. Rev. Lett. 114 (2015) 192501
[18] Wu, J., Nishimura, S., Lorusso, G., et al., 94 β-Decay Half-Lives of Neutron-Rich 55 Cs to 67 Ho:Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation, Phys. Rev.
Lett. 118 (2017) 072701
[19] Nakamura, T., Kobayashi, N., Kondo, Y., et al., Halo Structure of the Island of Inversion Nucleus
31
Ne, Phys. Rev. Lett. 103 (2009) 262501
[20] Takechi, M., Otsubo, T., Fukuda, M., et al., Interaction cross sections for Ne isotopes towards the      island of inversion and halo structures of 29Ne and 31Ne, Phys. Lett. B 707 (2012) 357[21] Kobayashi, N., Nakamura, T., Kondo, Y., et al., Observation of a p-Wave One-Neutron Halo Conﬁgurationin37Mg,Phys.Rev.Lett.112(2014)242501
[22] Takechi, M., Suzuki, S., Nishimura, D., et al., Evidence of halo structure in 37Mg observed via
reaction cross sections and intruder orbitals beyond the island of inversion, Phys. Rev. C 90 (2014)
061305(R)

11- 11 -

JAEA-Conf 2021-001[23] Bagchi,S.,Kanungo,R.,Tanaka,Y.K.,etal.,Two-NeutronHaloisUnveiledin 29F,Phys.Rev.Lett.
124 (2020) 222504
[24] Kisamori, K., Shimoura, S., Miya, H., et al., Candidate Resonant Tetraneutron State Populated bythe 4He(8He,8Be) Reaction, Phys. Rev. Lett. 116 (2016) 052501
[25] Kondo, Y., Nakamura, T., Tanaka, R., et al., Nucleus 26O: A Barely Unbound System beyond theDrip Line, Phys. Rev. Lett. 116 (2016) 102503
�[26] Sekiguchi, K., Witala, H., Akieda, T., et al., Complete set of deuteron analyzing powers from dp
elastic scattering at 190 MeV/nucleon Phys. Rev. C 96 (2017) 064001
[27] Yasuda, J., Sasano, M., Zegers, R. G. T., et al., Extraction of the Landau-Migdal Parameter fromthe Gamow-Teller Giant Resonance in 132Sn, Phys. Rev. Lett. 121 (2018) 132501
[28]Wang,H.,Otsu,H.,Sakurai,H.,etal.,Spallationreactionstudyforﬁssionproductsinnuclear
waste: Cross section measurements for 137 Cs and 90 Sr on proton and deuteron Phys. Lett. B 754(2016) 104[29] Sun, X. H., Wang, H., Otsu, H., et al., Spallation and fragmentation cross sections for 168      MeV/nucleon 136Xe ions on proton, deuteron, and carbon targets Phys. Rev. C 101 (2020) 064623
[30] ImPACT: “Reduction and Resource Recycling of High-level Radioactive Waste through Nuclear
Transmutation”, https://www.jst.go.jp/impact/hp fjt/en/ BDDFTTFE [31]Wang,H.,Otsu,H.,Sakurai,H.,etal.,Spallationreactionstudyforthelong-livedﬁssionproduct107
Pd, Prog. Theor. Exp. Phys. 2017 (2017) 021D01
[32] Kawase, S., Nakano, K., Watanabe, Y., et al., Study of proton- and deuteron-induced spallation
reactions on the long-lived ﬁssion product 93 Zr at 105 MeV/nucleon in inverse kinematics, Prog.
Theor. Exp. Phys. 2017 (2017) 093D03
[33] Nakano,K.,Watanabe,Y.,Kawase,S.,etal.,Isotopeproductioninproton-,deuteron-,andcarboninduced reactions on 93Nb at 113 MeV/nucleon Phys. Rev. C 100 (2019) 044605
[34] Takeuchi, S., Nakamura T., Shikata, M., et al., Coulomb breakup reactions of 93,94Zr in inverse
kinematics Prog. Theor. Exp. Phys. 2019 (2019) 013D02
[35] Wang, H., Otsu, H., Chiga, N., et al., Enhancement of element production by incomplete fusion
reaction with weakly bound deuteron Comm. Phys. 2 (2019) 78
[36]Michimasa,S.,Imai,N.,Dozono,M.,etal.,Newenergy-degradingbeamlineforin-ﬂightRIbeams,
OEDO, Nucl. Instrum. Methods Phys. Res., Sect. B 463 (2020) 143[37]Sumikama,T.,Ahn,D.S.,Fukuda,N.,etal.,Energy-controlandnovelparticle-identiﬁcationmethodscombinedwithrangeinamulti-samplingionizationchamberforexperimentsusingslowed-down
RI beams Nucl. Instrum. Methods Phys. Res., Sect. A 986 (2021) 164687
[38] Kunieda, S., Furutachi, N., Minato, F., et al., JENDL/ImPACT-2018: a new nuclear data libraryforinnovativestudiesontransmutationoflong-livedﬁssionproducts,J.ofNucl.Sci.andTech.52,
1073(2019)
[39] Sato, T., Niita, K., Matsuda, N., et al., Particle and Heavy Ion Transport code System, PHITS,
version 2.52, J. of Nucl. Sci. Technol. 50, 913 (2013).
[40] Okuno, H., Sakurai, H., Mori, Y., et al., Proposal of a 1-ampere-class deuteron single-cell linac fornuclear transmutation, Proc. Jpn. Acad. Ser. B 95 430-439 (2019)
[41] Yamada,K.,Ozeki,K.,Kamigaito,O.,etal.,FirstverticaltestofsuperconductingQWRprototypeat RIKEN, Prof. of LINAC2016, TUPLR061, 598 (2016).
[42] Mori, Y., Taniuchi, A., Kuriyama, Y., et al.., Intense Negative Muon Facility with MERIT ring for
Nuclear Transmutation, JPS Conf. Proc.21,011063 (2018).
[43] Imao, H., Charge Stripper Ring for RIKEN RI Beam Factory, J. of Instrum. 15, P12036 (2020)

Acknowledgments
IwouldliketothanktheorganizersofSND2020forthesafeorganizationandattractiveprogram.Because
of COVID-19 pandemic, they smartly introduced a hybrid meeting, where in-person and on-line
participations were eﬀectively arranged and managed.

12- 12 -

JAEA-Conf 2021-001

 Nuclear data study for Accelerator Driven SystematJ-PARC
Shin-ichiroMEIGO†1
1

J-PARC Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai, Ibaraki, 319-1195,
Japan†
Email: meigo.shinichiro@jaea.go.jp

Abstract
To decrease the toxic waste produced at the nuclear reactor, studies of the Accelerator
Driven System (ADS) are developing worldwide. Since the neutron production target at
ADS is designed to be irradiated by protons in several GeV kinetic energy, a study with thehigh-energy particles in the kinetic energy region around GeV is essential for the researchand development of ADS. However, many accelerator facilities using several GeV-protons
built in the 1970s have been shut down due to their lifetime. Eventually, the facilities tobe able to use protons with several GeV are scarce in the world. In Japan, J-PARC can
only apply for the sake of ADS using the hadron, including proton. Using the 3-GeV proton
synchrotron, some studies are going at J-PARC aimed at obtaining the nuclear data of ADS.
In this paper, some experiments related to nuclear data for ADS are introduced, such as
nuclide production cross section induced by proton and displacement cross section.

1

Introduction

To reduce the hazards associated with the radioactive waste produced in a nuclear reactor, Japan
Atomic Energy Agency (JAEA) proposed an accelerator-driven system (ADS) that comprises
extremely high-power accelerators (30 MW) with proton kinetic energy of 1.5 GeV [1]. Since
the neutron production target at ADS is designed to be irradiated by protons in several GeV
kinetic energy, a study with the high-energy particles in the kinetic energy region around GeV
is essential for the research and development of ADS. However, many accelerator facilities using
several GeV-protons, such as SATURNE at CEA, established for nuclear physics in the 1970s,
have been shut down due to their lifetime. Eventually, the facilities to be able to use protons
with several GeV, such as AGS at BNL, PS at CERN, and U-10 at ITEP, are scarce in theworld. In Japan, J-PARC can only apply for the sake of ADS using the hadron, including
proton. Therefore, our group conducted nuclear data studies for ADS at the 3-GeV proton
synchrotron (RCS) facility and the beam transport line.
In this paper, some experiments carried out at J-PARC for the nuclear data for ADS using several GeV-protons are introduced, such as nuclide production cross section induced byprotons [2, 3] and displacement cross section [4, 5].

2

Displacement cross section

In ADS, Lead–bismuth eutectic (LBE) is used as a target material, and it simultaneously plays
the role of a coolant. While designing ADS, damage to the beam-intercepting material is one of13- 13 -

JAEA-Conf 2021-001

the critical issues. In other high-intensity accelerator facilities, the beam–intercepting material
also plays essential roles. To conﬁdently operate a high-power accelerator, damage estimation of
the target material is essential. For quantitative speciﬁcation of the damage to the target material, the displacement per atom (dpa) index is generally employed. A dpa is widely used for theestimation of the damages caused to nuclear reactors and fusion reactors. The dpa is estimatedusing the particle ﬂuence multiplied with displacement cross section. The cross section is usually obtained using the Norgertt–Robinson–Torrens (NRT) model [6]. In the low-energy region
below 20 MeV, the displacement cross section for a proton can be reliably predicted because the
Coulomb force mainly causes the displacement. The calculation method for the displacement
cross section has been established for the low-energy regions where nuclear reactions produce noparticles. However, for the protons in the high-energy region above 20 MeV, the experimental
data of the displacement cross section are scarce. Therefore, the displacement cross section has
not been adequately studied. Since many reaction channels open (above 20 MeV), calculation
codes based on the intra-nuclear cascade model are used to obtain the cross section. Althoughiron materials play essential roles, such as the beam window for the ADS and target vessels of
the spallation neutron source, the experimental data of the displacement cross section have notbeen observed in the energy region above 20 MeV. For validation and improvement of the dpa
evaluation, the experimental data are crucial.

2.1

Experiment of displacement cross section

For the displacement cross-section measurement, we conducted experiments at 3-GeV proton
beam transport (3NBT) line at the J-PARC. A vacuum chamber with a cryocooler was installedat the front of the beam dump of the 3-GeV rapid cycling synchrotron (RCS). At the RCS, thekinetic energy of the extracted proton can vary from 0.4 to 3 GeV, altering the timing of theextraction kicker magnet. With the change in the rigidity of the following magnets, the beam
was introduced to the sample.
Since there was no space in the beamline introduced to the beam dump, the experimental
equipment was installed in the beamline, where the high-intensity proton beam could be delivered to the spallation neutron source in the MLF. Although the low-intensity proton beam
was irradiated to sustain the cryogenic temperature of the sample, an additional interlock of theaccelerator was required for the experiment owing to safety reasons, which changed the licensingof the RCS described in Japanese law of act concerning prevention from radiation hazards due
to radioisotopes.
At the RCS, the kinetic energy of the extracted proton can vary from 0.4 to 3 GeV, altering
the timing of the extraction kicker magnet. With the change in the rigidity of the following
magnets, the beam was introduced to the sample. For observation of the damage in the sample,
the irradiated sample is required to be cooled at a cryogenic temperature (around 10 K), where
the recombination of Frenkel pairs is well suppressed owing to thermal motion. With the observation of the resistivity change Δρ due to the irradiation at the cryogenic temperature, theexperimental displacement cross section σexp (E), is given by the following,
σexp (E) = Δρ/(φ(E)ρF P ),(1)

where φ(E) is the average proton ﬂuence at the sample over irradiation time, ρF P is the resistivity
change per Frenkel-pair density for a particular metal, which has an uncertainty of 20%.
A vacuum chamber was installed in front of the 3-GeV beam dump. The chamber thatwas installed at the beam transport line maintained vacuum pressure less than 10−5 Pa using
the sputter-ion pumps. The chamber was equipped with a Giﬀord–McMahon (GM) (Sumitomo
Heavy Industries RDK-408D2) cryocooler. The GM cryocooler cooled the sample using an
14- 14 -

JAEA-Conf 2021-001

oxygen-free high-conductivity copper rod and sample holder made of aluminum that was placedat the tip of the copper rod, as shown in Fig. 1. The GM cooler comprises two structures:the 1 st and 2 nd stages. At the 1 st and 2 nd stages, the temperatures can reach 40 K and
4 K, respectively. For the measurement of the thermal recovery of the sample, a heater was
attached to the copper rod. The assembly of the GM cryocooler and a sample wire was placedon a movable stage to control the irradiation. Since the RCS kicks the beam horizontally forthe extraction, the stability of the beam position in the vertical direction is better than in thehorizontal.
To obtain the beam window material data used at the ADS, we selected iron as the sample.
Before installation, the sample was annealed just less than the melting point to eliminate thedefect of the lattice. Each sample was sandwiched between electrical insulation sheets of analuminum nitride ceramic and held by the holder made of aluminum. To minimize the beaminteraction on the holder, we made an aperture with 40-mm diameter for the sample holder. The
resistance of the sample was measured using a voltmeter and current source. The sample wire
was connected through terminals to both the current source and voltmeter for the compensationof the cable resistance between the sample and instruments. The precision of this resistancemeasurement was ±0.01 μΩ, corresponding to a resistivity of ±3 fΩm.
The resistance thermometer on the sample holder was calibrated in the temperature rangeof 4 –100 K, and a silicon thermometer on the copper column was calibrated between 4 K andthe room temperature. The resistance decreased with the temperature. It was observed thatthe resistance was saturated around the cryogenic temperature (∼4 K).
The electrical resistivity of the sample ρ is expressed as follows: ρ = RA/L, where R [Ω] isthe measured electrical resistance, A is the area of the sample (4.9×10−8 m2 ) with a diameter of
250 μm, and L is the length between two potential points (40 mm). To avoid heat introduction
to the sample owing to radiation to the sample, the sample was surrounded using double-walledradiation thermal shields made of aluminum. The outer and inner shields with a thickness of 2
and 1 mm, were directly connected to the1 st and 2 nd stage of the GM cooler, respectively. To
minimize the scattering of the proton beam on the shields, we placed thin aluminum foils witha thickness of 5 μm and at the beam entrance and exit holes (with a diameter of 40 mm) for
both thermal shields. After 6 h of cooling, the temperature of the sample holder was less than
4 K. Note that, in the early period of the experiment, the temperature was not 4 K, but ∼20
K. With some trials changing the conditions, the heat was introduced through the measurement
cables for the resistance and temperature.
To ﬁt the beam position on the sample precisely, the beam was vertically scanned with thesteering magnet placed upstream of the sample along the beam direction. With the observationof the change in resistivity during the scan, the beam position given by the proﬁle monitor
was conﬁrmed to be the center of the wire owing to the precious beam control developed at JPARC [7, 8]. During the beam irradiation, the resistance of the iron sample was observed withthe temperature of the sample holder determined using the attached thermometer. Although
the sample temperature was not directly observed, it can be expected to be ∼4 K. During theirradiation of the sample, the temperature slightly increased. The observed temperature of theholder increased by 0.2 K. After irradiation, the sample resistance was increased by about 0.2
μΩ from the start of the beam irradiation, which was produced due to the displacement.

2.2

Results of displacement cross section

Using Eq(1), the displacement cross sections of iron are obtained. In this work, the resistivity
change per Frenkel-pair ρF P was deﬁned as 2.46×10−6 ± 0.57 Ωm for iron, obtained fromanother study [9]. It should be mentioned that the error of the present cross-section data wasdominated by the one of the resistivity change per Frankel-pair. To obtain high-precision results,
15- 15 -

JAEA-Conf 2021-001

the uncertainties of the resistivity change by Frankel-pair creation need to be improved, whichis expected to be achieved using an electron beam.
Figure 2 shows the calculation results using PHITS [10] with intra-nuclear cascade model of
INCL-4.6 [11], which are shown as black single-dot and solid red lines. In Fig. 2, the evaluateddata were given by the Karlsruhe Institute of Technology (KIT) [12] shown as blue dashed andorange two-dotted lines. To PHITS calculation and KIT evaluation, the NRT model, which
is widely utilized for evaluation of dpa, and the athermal–recombination–corrected dpa (arcdpa) model based on molecular dynamics (MD) were applied. The parameters for the arc-dpa
given by Nordlund [13] was applied to PHITS. KIT used the binary collisional approximation(arc-dpa-BCA) model for evaluation. The displacement cross section of iron (red solid circles)
compared with the previous experimental data by Jung [14] (black solid circles). The current
data of iron were found to be lower than the calculation with the NRT model with PHITS andKIT evaluation by about 2 times.

Figure 1: Schematic of the sample, vacuum
chamber, and GM cryocooler used for thepresent experiment.

3

Figure 2: Comparison of the present experimental data for iron with previous experimental
data [14], calculation data using PHITS [10] andKIT evaluations [12].

Production cross section induced by several GeV-protons

To estimate the residual nuclei in the beam window and the target, the production cross section
is required. However, the data are not enough to validate the calculation models. For validationof the calculation model, we have been carried out the production cross section using several
GeV-protons. For the experiment, sample changers with sample holders were installed at 3NBT.
After irradiation, the sample was observed by the high-pure Germanium detector. With the
gamma spectrometry, the production cross section was derived.
As an example, the experimental results of nat Fe(p,x)7 Be is shown in Fig. 3 compared withthe various calculation models and the evaluation data of JENDL/HE-2007. It is shown that
INCL++/ABLA07 and INCL/GEM show remarkable underestimation for the kinetic energy
range above 1 GeV region. The nuclide of 7 Be is mainly produced by the statistical decay16- 16 -

JAEA-Conf 2021-001

and partially produced by the multifragmentation. On the other hand, the previous calculation model of Bertini/GEM shows good agreement in the energy range above 2 GeV. Although
JENDL/HE-2007 shows a good agreement with the experimental results, it shows a slight overestimation for energies above 2 GeV. Using the present experimental results, the evaluation will
be improved.
Just the same cross section for 56 Fe was measured by the GSI using the inverse-kinematics
method, which is also shown in Fig. 3. The present data disagree with the data measured at the
GSI [15], which is pointed out by the other study [16]. It can be concluded that another study
using inverse kinematics has worth to reveal the detailed production process for the improvementof the model.

4

Summary

To evaluate the target materials used in highintensity proton accelerators, particularly in
ADS, experiments for displacement and nuclei production cross-sections measurements
were carried out in J-PARC. The displacement
cross section of iron irradiated using protons
having kinetic energies in the range 0.4 and 3
GeV was successfully obtained. It should be
mentioned that the present data for iron is theﬁrst experimental data in the projectile energy region above 400 MeV, which is essential
for the research and development of ADS. The
present experimental data of the displacement
cross sections were compared with the calculation using the PHITS and the data evalu- Figure 3:
Production cross section of
ated by KIT. The present results showed an nat Fe(p,x)7 Be as a function of kinetic enoverestimation of the cross section using the ergy of projectile protons.
widely employed NRT model by a factor of 2,
this model was preferred for the proton projectile with lower energy than 10 MeV. In contrast,
the arc-dpa model shows remarkably good agreement with the present data. For the nuclei
production cross section induced by several GeV-protons, further improvements to the model
are required to reproduce the cross section. For this sake, we will continue the experiment at
J-PARC.

Acknowledgment
This paper partially contains the results of “Measurement of displacement cross section at JPARC for structural material utilized at ADS” entrusted to JAEA by the Ministry of Education,
Culture, Sports, Science, and Technology of Japan.

References[1] Tsujimoto K, Oigawa H, Ouchi N, et al. Research and development program on accelerator driven subcritical system in JAEA  Journal of Nuclear Science and Technology  2007;
44(3):483–490.
17- 17 -

JAEA-Conf 2021-001[2] MatsudaH,MeigoS,IwamotoH Proton-inducedactivationcrosssectionmeasurementforaluminum with proton energy range from 0.4 to 3 GeV at J-PARC  Journal of Nuclear
Science and Technology  2018;55(8):955–961.
[3] MeigoS,NishikawaM,IwamotoH,etal. Measurementofaluminumactivationcrosssection
andgasproductioncrosssectionfor0.4and3-GeVprotons.EPJWebConf.2017;146:11039.
[4] Meigo S, Matsuda H, Iwamoto Y, et al.  Measurement of Displacement Cross Section ofStructuralMaterialsUtilizedintheProtonAcceleratorFacilitieswiththeKinematicEnergy
above 400 MeV; 2020.
[5] Matsuda H, Meigo S, Iwamoto Y, et al.  Measurement of displacement cross-sections ofcopper and iron for proton with kinetic energies in the range 0.4 – 3 GeV  Journal of
Nuclear Science and Technology  2020;57(10):1141–1151.
[6] Norgett M, Robinson M, Torrens I  A proposed method of calculating displacement dose
rates  Nuclear Engineering and Design  1975;33(1):50 – 54.
[7] Meigo S, Ohi M, Kai T, et al.  Beam commissioning for neutron and muon facility at JPARC  Nuclear Instruments and Methods in Physics Research Section A: Accelerators,
Spectrometers, Detectors and Associated Equipment  2009;600(1):41 – 43.
[8] MeigoS,OoiM,FujimoriH Two-parametermodelforoptimizingtargetbeamdistribution
with an octupole magnet  Phys Rev Accel Beams  2020 Jun;23:062802.
[9]BroedersC,KonobeyevA Defectproductioneﬃciencyinmetalsunderneutronirradiation
Journal of Nuclear Materials  2004;328(2):197 – 214.
[10] IwamotoY,NiitaK,SawaiT,etal. ImprovementofradiationdamagecalculationinPHITS
andtestsforcopperandtungstenirradiatedwithprotonsandheavy-ionsoverawideenergy
range NuclearInstrumentsandMethodsinPhysicsResearchSectionB:BeamInteractionswith Materials and Atoms  2012;274:57 – 64.
[11] BoudardA,CugnonJ,DavidJC,etal. Newpotentialitiesoftheliègeintranuclearcascade
modelforreactionsinducedbynucleonsandlightchargedparticles PhysRevC 2013Jan;
87:014606.
[12] KonobeyevA,FischerU,SimakovS Improvedatomicdisplacementcross-sectionsforprotonirradiationofaluminium,iron,copper, andtungstenatenergiesupto10GeV Nuclear
InstrumentsandMethodsinPhysicsResearchSectionB:BeamInteractionswithMaterials
and Atoms  2018;431:55 – 58.
[13] NordlundK,ZinkleSJ,SandAE,etal. Improvingatomicdisplacementandreplacementcalculationswithphysicallyrealisticdamagemodels NatureCommunications 2018;9(1):1084.
[14] JungP Atomicdisplacementfunctionsofcubicmetals JournalofNuclearMaterials.1983;
117:70 – 77.
[15] Napolitani P, Schmidt KH, Botvina AS, et al.  High-resolution velocity measurements onfullyidentiﬁedlightnuclidesproducedin56Fe+and56Fe+titaniumsystems PhysRevC 
2004 Nov;70:054607.
[16] TitarenkoYE,BatyaevVF,TitarenkoAY,etal. Crosssectionsfornuclideproductionina
56 Fe target irradiated by 300, 500, 750, 1000, 1500, and 2600 MeV protons compared withdata on a hydrogen target irradiated by 300, 500, 750, 1000, and 1500 MeV/nucleon 56 Fe
ions. Phys Rev C. 2008 Sep;78:034615.
18- 18 -

JAEA-Conf 2021-001

 Proposal of a 1 ampere class deuteronsingle-celllinac for nuclear transmutation
Hiroki OKUNO†1 , Hiroyoshi SAKURAI 1 , and Yoshiharu MORI2
1

2

Nishina Center for Accelerator-Based Science
Institute for Integrated Radiation and Nuclear Science, Kyoto University†
Email: okuno@riken.jp

A 1 ampere class high-intenisty deuteron linac (ImPACT2017 model) is proposed forthe mitigation of the long-lived ﬁssion products (LLFPs) by nuclear transmutation. This
accelerator consists of single-cell rf cavities with magnetic focusing elements to accelerate
deuterons beyond 1 A up to 200 MeV/u.

1

Introduction

Figure 1: Schematic of a single-cell linac, model ImPACT2017.
High-level radioactive waste from nuclear power plants has been posing a number of inherent
problems, including the lack of progress in considering disposal sites [1], possible vulnerabilities
in counter-terrorism measures, or so. To address these problems, research and development ofpartitioning and transmutation technologies are essentially important to determine the mosteﬃcient methods for the reduction of radioactivity in waste material [2]. We hereby proposea reasonably feasible transmutation scheme with high-energy neutrons produced by a deuteronbeam, where liquid lithium is utilized for the production target [3]. To realize the transmutation
scheme, design of a 100-200 MeV/u deuteron accelerator with an intensity of 1 A is highly
desired for the transmutation of LLFP nuclides.
We consider a linac that can accelerate deuterons to such a high current. Most modern
high-power linacs [3, 4, 5, 6] use a radio frequency quadrupole (RFQ) as a front-end accelerator,
19- 19 -

JAEA-Conf 2021-001

which performs adiabatic rf capture of a direct current (DC) beam from an ion source, transverse
focusing, and acceleration. The typical aperture of an RFQ is 1 cm. However, the expected sizeof the 1-A beam from an ion source amounts up over 10 cm in diameter. It is therefore evident
that an RFQ cannot accommodate such large beams with 1 A. In this study, we propose a novel
linac that consists of single-cell cavities with magnetic focusing elements to accept a 1-A beamwith a large bore. The single-cell linac (SCL) has the following advantages for the accelerationof high-intensity beams:• Low-frequency rf cavities with a large bore can be used to mitigate strong space charge
forces owing to lower beam current density.
• Voltage and phase of each cell can be independently selected to compensate for the spacecharge eﬀects, and also to implement an eﬃcient bunching function for a DC beam like an
RFQ entrance section.

Table 1: Basic parameters of the single-cell linac ImPACT2017. QWR stands for quarter wave
resonator.
Ion Source and LEBTEnergy range (MeV/u) 0.1
Type of IS
Cusp ion source
Particledeuteron
Beam current (A)1
Emittance (normalized) 25π mm·mrad
Low-βsection
Energy range (MeV/u) 0.1-5
Number of cell
90
Cell length (m)0.25
rf cavity
Normal conducting
Single gap
Focusing
SolenoidMedium-β section
Energy range (MeV/u) 5-40
Number of cell
44
Cell length (m)1.38
rf cavity
Superconducting
QWR, Double gaps
Focusing
Quadrupole magnet
High-β section
Energy range (MeV/u) 40-200
Number of cell
200
Cell length (m)0.8
rf cavity
Superconducting
Single gap
Focusing
Quadrupole magnet

20- 20 -

JAEA-Conf 2021-001

2

SchemeThe 1-A deuteron SCL (ImPACT2017 model) consists of four sections: (1) the ion source section,(2) the low-β section, (3) the medium-β section, and (4) the high-β section. Figure 1 showsa schematic layout of this system and the typical parameters of each section are presented inTable 1. In this scheme, a large transverse normalized RMS emittance of 25π mm·mrad is
assumed at the injection of the SCL, which is suﬃcient for relaxing the space charge eﬀect in
the beam dynamics. A relatively low rf frequency acceleration system is suitable for a largebore.
In the SCL, the fundamental mode of the longitudinal space charge force could be compensated cell by cell through individual ﬁne rf detuning to beam bunches. The SCL also facilitates
individual strong beam focusing against the transverse space charge force with external magnetic
focusing elements, such as solenoids and quadrupole magnets.
The ion source produces a current of deuterons, with a magnitude above 1 A. A cusp-ﬁeldconﬁnement-type ion source with a large extraction area was chosen because a multi-hole beam
extraction system is inevitable for the extraction of such large beam currents. Such ion sources
are used for NBI (neutral beam injector) in Tokamak fusion reactors. The structure of the ion
source can be seen, for example, in [7]. The Child-Langmuir law estimates that a current of
20 mA/cm2 can be extracted at maximum through one hole with a diameter of 14 mm whenan extraction voltage of 6 kV is applied to the gap of 3 mm. At least 37 holes are required to
extract 1 A assuming that the ratio of D+ to the total current including D+
2 , etc. is 85%. The
low-energy beam transport (LEBT) section consists of a series of beam focusing solenoids.
The low-β section is composed of approximately 90 single cells, and each cell includes asingle rf cavity with a 25 MHz resonant frequency and a focusing solenoid. The rf cavity has
a capacitive plate to maintain the outer diameter under ∼2 m and the maximal rf voltage isapproximately 300 kV, which is approximately 1.2 KL , where KL is discharge limit given as
a function of the frequency by Kilpatrick [8]. The transit time factor at 5 MeV/u exceeds
0.95. The rf power except the beam power dissipated by the entire single-cell cavity system isapproximately 5 MW.
The rf voltage and phase of every single cavity were appropriately selected to optimize thebeam capture and acceleration. The optimization was performed by evaluating the adiabatic
parameter, as shown in the following [9] [10] [11]:1  dA 
Ωs >>   ,
A dt




(1)

where A is a rf bucket area and Ωs is the phase (synchrotron) oscillation frequency, and fromthis criterion, an adiabatic parameter is deﬁned as,
na =

Ωs Ts
.
1 − [Vi /(Vi + ΔV )]1/2(2)Here, Vi is rf voltage, ΔV increment of rf voltage per cell and Ts transit time per cell.
Good adiabaticity is achieved when the value of the adiabatic parameter na exceeds 10
and the DC beam from the ion source can be well-captured by the rf bucket and consequently
accelerated. The phase and rf voltage variations should be appropriately optimized to preserve
the adiabaticity of the beam capture and acceleration, following the condition shown in eq.(1).
The longitudinal beam behavior was simulated for these conditions and the results are plottedin Fig. 2. Evidently, the beam is well captured and is accelerated adiabatically. This rf captureof the DC beam was successfully simulated by a 3D PIC code.
21- 21 -

JAEA-Conf 2021-001

  

All_Phase_Energy
 


5



 

Energy [MeV/u]

4
3
2






1
0




−3

−2

−1

0

1

2




3

Phase [Rad]









 



Figure 2: Beam capture and acceleration: left panel shows the entire longitudinal beam motionin the low-β section, while right plot shows the initial phase of the beam capture and acceleration.
The deuteron beam from the low-β section is accelerated up to 40 MeV/u via the medium-β
section that consists of 44 superconducting quarter wave resonators (QWRs) at 50 MHz andquadruple magnets between the resonators. The superconducting and/or permanent magnets
act as the quadrupole magnet. The schematic layout of the QWR is shown in Fig. 3. The
height and diameter of the outer cylinder are 1.62 m and 1.16 m, respectively and the maximal
rf voltage is 1.24 MV. The transit time factor is approximately 0.74 at 40 MeV/u and the gap
distance is 0.58 m, which corresponds to βλ/2 at 18 MeV/u.

Figure 3: Structure of QWR (left) for the medium β and Reentrant cavity(right) for the highβ section. The arrows in the cavities show electric ﬁeld. Size of the arrow is proportional tostrength of the electric ﬁeld.
The deuteron beam from the medium-β section is accelerated up to 100–200 MeV/u throughthe high-β section that consisted of 200 superconducting reentrant cavities at 100 MHz andquadruple magnets between the resonators. The superconducting and/or permanent magnets
serve as the quadrupole magnet. The schematic layout of the reentrant resonator is shown in
Fig. 3. The diameter and the length of the cavity are 1.25 m and 0.6 m, respectively and the
maximal rf voltage is 2.3 MV. The transit time factor is approximately 0.96 at 200 MeV/u.

22- 22 -

JAEA-Conf 2021-001

2.1

Summary

A 1 ampere class deuteron linac (ImPACT2017 model) was proposed for the mitigation of thelong-lived ﬁssion product (LLFP) by nuclear transmutation. This model consists of single-cellrf cavities with magnetic focusing elements to accelerate deuterons beyond 1 A. The beam
dynamics and conceptual design for each section were presented and discussed.

References[1] http://www.scj.go.jp/ja/info/kohyo/pdf/kohyo-22-k159-1.pdf[2] IAEA Technical Reports Series (2004) No. 435.
[3] Knaster, J., (2017) Overview of the IFMIF/EVEDA project, Nucl. Fusion 57, 102016.
[4] Henderson, S., et al., (2014) The Spallation Neutron Source accelerator system design, Nucl
Instrum Meth A, vol. 763, pp. 610-673.
[5] Ed. Peggs, S., (2013) ESS Technical Design Report, ESS-DOC-274.
[6] Pan, W. M., (2012) Chinese ADS Project and Proton accelerator development, Proc. of
LINAC2012, TU1A03, Tel-Aviv, Israel.
[7] Kuriyama, M. et al., (1987) The Design, Research and Development of JT-60 Neutral Beam
Injector, JAERI-M 87-169 (in Japanese).
[8] Kilpatrick, W. D. (1957) Criterion for Vacuum Sparking Designed to Include Both RF and
DC. Rev. Sci. Instr. 28, 824-826.
[9] Montague, B. W. (1977) Single-particle dynamics - RF Acceleration. Proc. of the ﬁrst courceof the Int. School of Particle Accelerators. CERN 77-13, 63-81.
[10] Lilliequis, C. G. and Symon, K. R. (1959) Deviations from adiabatic behavior during captureof particles into an rf bucket. MURA-491, 1-9.
[11] Ng, K.Y. (2012) Adiabatic capture and debunching. FNAL Report, FERMILAB-FN-0943APC, 1-11.

23- 23 -

JAEA-Conf 2021-001

 Uniﬁeddescriptionoftheﬁssionprobability
for higIlyexcited nuclei
HirokiIWAMOTO†1
1

NuclearScienceandEngineeringCenter,Japan AtomicEnergyAgency†

Email: iwamoto.hiroki@jaea.go.jp

This paper describes a summary of the spallation reaction and its theoretical model, focusing
on the spallation product yields, and then our research work about the improvement of the ﬁssion
probability model is presented.

1

Introduction

Recently, spallation neutrons produced from the spallation reactions have been utilized for thematerial and fundamental sciences as well as industrial applications in the spallation neutron
source facilities (e.g. MLF at J-PARC [1, 2, 3], ISIS [4], and SNS [5]). In these facilities, Monte
Carlo particle transport codes such as PHITS [6], MCNP [7], GEANT4 [8], FLUKA [9] play asigniﬁcant role in the assessment of radiation dose and inventory of radioactive materials.
In this paper, we brieﬂy describe the spallation reaction and its theoretical spallation model,
focusing on spallation product yields; then, our research work on this title is presented.

2

Spallation reaction

2.1

Spallation reaction process

Figure 1 schematizes a process of the spallation reaction. The spallaion reaction starts with acollision between an incident particle and a nucleon which is a constituent of a nucleus. The
bombarded nucleon emits solely from the nucleus, hit other nuclons several times, or emits
binding to nucleons in the nuclear surface; this process is referred to as the intranuclear cascade
process. After this process, the remaining energy is uniformly distributed by repeating soft
collisions, which results in a quasi-stable, highly-excited state.
This highly-excited nucleus de-excites by statistically emitting neutrons, charged particles
and photons; this process is referred to as the de-excitation process; this process is also known
as the evaporation process. For heavy targets such as gold, lead, and uranium, ﬁssion occurrs
competing with the evaporation.

2.2

Distribution of spallation products and spallation model

Figure 2 compares the mass number distribution of the spallation products produced from the1-GeV proton-induced 208 Pb reaction between the experimental data [10] and calculation resultswith four major spallation models (i.e. INCL++/ABLA07 [11, 12], INCL++/GEMINI++ [13],INCL4.6/GEM [14], and CEM03.03 [15]). Three humps observed in this ﬁgure are referred to as
evaporation residues (ER), ﬁssion fragments (FF), intermadiate mass fragments (IMF), and light24- 24 -

JAEA-Conf 2021-001

Figure 1: Process of the spallation reaction.

Figure 2: Mass number distribution of the 1-GeV proton-induced 208 Pb target reaction.

charged particles (LCP) in order of decreasing mass number. While all models explain the featureof the mass number distribution, they are not very good in terms of the prediction accuracy.
For example, INCL4.6/GEM, which is a default spallation model of PHITS, underestimatesthe ﬁssion fragment yields by at most 50%. Because the ﬁssion fragments contains volatile
radioactive materials such as radioactive kripton, xenon, and iodine, this underestimation may
involve a signiﬁcant problem in terms of the radiation safety of the spallation neutron source
facilities. These discrepancies were discussed in detail in our previous work [16].

3Improvement of ﬁssion probability

3.1

Description of ﬁssion probability

A recent benchmark analysis of the PHITS code revealed that INCL4.6/GEM implemented
in PHITS underestimates the ﬁssion fragment yields. This underestimation indicates that theﬁssion probability should be enhanced within the framework of the de-excitation model GEM.
The GEM describes the ﬁssion probability as follows.
P =

Γf
,
Γn + Γf25- 25 -(1)

JAEA-Conf 2021-001

where Γf and Γn represent the decay widths of ﬁssion and neutron evaporation, respectively.
Although parameters of these decay widths need to be sophisticated as a straightforward method,
this approach requires a signiﬁcant amount of time spent in tuning the model parameters. To
avoid this, we modiﬁed the ﬁssion probability itself instead of the decay widths, which are
deduced from a systematics of proton-induced ﬁssion cross sections.
The ﬁssion cross section σﬁs and non-elastic cross section σnonel are linked to the following
equation:
σﬁs
,
(2)
P=
σnonelwhere P indicates a total ﬁssion probability, which can be calculated from the systematics ofthe proton-induced ﬁssion cross sections (Prokoﬁev systematics [17]) and that of the non-elastic
cross sections (Pearlstein–Niita systematics [18]); both are functions of incident proton energy
and mass and proton numbers of the target nucleus. However, what we are interested in here is
the ﬁssion probability which is a function of excitation energy, mass number, and proton numberof the highly excited nuleus. To resolve this discrepancy, relationships among information ofprojectile, target nuclei, and highly-excited nuclei are deduced statistically from the intranuclear
cascade model calculation, and the ﬁssion probability was determined by multiplying the totalﬁssion probability with a function g:
P = g · P(�Ep �, �Zt �, �At �),(3)where �Ep �, �Zt �, and �At � are the corresponding incident proton energy, proton number, andmass number, respectively. The function g is expressed as
1
g = max 0, γ 0
,
(4)
− γ3
1 + e−γ 1 (E−γ 2 )where γi (i = 0, 1, 2, 3) is adjustable parameters to account for the proton-induced ﬁssion crosssections, which are expressed as
γ 0 = 0.46,

γ 1 = 0.10,

γ 2 = 57

X208 Pb
�Xt �

5.5
,

1
γ3 =
2



X208 Pb
�Xt �

3
,

(5)

where X208 Pb and �Xt � are the ﬁssility parameter for 208 Pb and the corresponding ﬁssility parameter for the highly-excited nucleus.

3.2
3.2.1

Results
Fission cross sections

Figure 3 shows examples of the proton-induced and neutron-induced ﬁssion cross sections calculated by the proposed model. It is seen that the proposed model reproduces the experimental
data fairly well, in contrast to the conventional model. Furthermore, even though this model isconstructed by the proton-induced systematics, it is applicable the neutron-induced reactions.
It was demonstrated that our model reproduces the experimental ﬁssion cross sections over awide range of subactinide targets for proton-, neutron-, and deuteron-induced reactions. Details
can be seen in Iwamoto et al. [19].
3.2.2

Fission fragment production cross sections

Figure 4 presents the proton-induced ﬁssion fragment production cross sections for the 1-GeV
208 Pb(p, X), 800-MeV 197 Au(p, X), and 500-MeV 208 Pb(p, X) reactions. Note that both the26- 26 -

JAEA-Conf 2021-001

Figure 3: Proton-induced and neutron-induced ﬁssion cross sections.

calculated and experimental cross sections indicate independent yields. Although our proposedmodel can provide the ﬁssion cross sections, namely the total ﬁssion fragment production crosssections, with markededly improved accuracy, it is observed from this ﬁgure that each peak forelement uniformly shifts to heavy mass numbers. This means that the ﬁssion fragments werecomputationally produced as uniformly neutron-rich states. The left panels of Figure 5 showN /Z distributions for the three reactions, comparing between the conventional and proposedmodels, in which the modiﬁed model becomes worse with respect to the N /Z distributions.
As shown in the right panels of Figure 5, we found that this discrepancy is reduced by emitting
three neutrons (ν = 3) from the ﬁssioning system. Because the neutron emission is considered
to be driven by the excitation energy, we investigated how much excitation energy is required
to account for the N /Z distributions. As a result, it was suggested that excitation energy ofabout 30–50 MeV is required, which would be consistent with a value deduced from the neutron
separation energy; if the separation energy is assumed to be 8 MeV, the minimum energy of thethree neutron emission becomes 24 MeV.

4

Conclusions

We have described the spallation reaction and its theoretical spallation model, focusing on
spallation product yields, and our research work have been presented. Recently, experimental
studies on the spallation reaction have become active in Japan [20, 21, 22]. We hope thatthe combination of our theretical work and these experiemntal activities will lead to a deeper
understanding of the spallation reaction mechanism.

References[1] Takada, H, et al., Quant. Beam Sci. 1(2), 2017, pp.8-1–8-26.
[2] Nakajima, K, et al., Quant. Beam Sci. 1(3), 2017, pp.9-1–10-59.
27- 27 -

JAEA-Conf 2021-001

Figure 4: Proton-induced ﬁssion fragment production cross sections. Experimental data weretaken from Enqvist et al. [10]<> Sakasai, K, et al., Quant. Beam Sci. 1(2), 2017, pp.10-1–10-35.
<> Thomason, J.W.G., Nucl. Instr. Meth. Phys. Res. A 917, 2019, pp.61–67.
<> Mason, T.E., et. al., Phys. B Condens. Matter 385–386(2), 2006, pp.955–960.
<> Sato, T., et al., J. Nucl. Sci. Technol. 55;12, 2018, pp.529–533.
<> Werner, C.J., et al. Los Alamos National Laboratory report LA-UR-17-29981, 2018.
<> Allison, J., et al., Nucl. Instr. Meth. Phys. Res. A 835, 2016, pp.186–225.
<> Böhlen, T.T., et al., Nucl. Data Sheets 120, 2014, pp.211–214.
<> Enqvist, T., et al. Nucl. Phys. A. 686, 2001, pp.481–524.
<> Leray, S., et al., J. Phys.: Conf. Series 420, 2013, 012065.
<> Kelic̀, A., et al., INDC(NDS)-0530, IAEA, 2008.
<> Charity, R.J., Phys. Rev. C 82, 2010, 014610.
<> Furihata, S., et al., JAERI-Data/Code 2001-015, 2001.
<> Mashnik, S.G., Nucl. Phys. A 568, 1994, pp.703–726.
<> Iwamoto, H., et al., EPJ Web of Conf. 239, 2020, pp.06001.
<> Prokoﬁev,A.V.,Nucl.Instr.Meth.Phys.Res.A463,2001,pp.557–575.
<> Niita, K., et al., Nucl. Instr. Meth. Phys. Res. B 184, 2001, pp.406–420.
<> Iwamoto, H., Meigo, S., J. Nucl. Sci. Technol. 56;2, 2018, pp.160–171.
<> Matsuda, H., et al., J. Nucl. Sci. Technol. 55;8, 2018, pp.955–961.
<> Matsuda, H., et al., Nucl. Instr. Meth. Phys. Res. A 483, 2020, pp.33–40.
<> Wang, H., et al., Phys. Lett. B 754, 2016, pp.104–108.
28- 28 -

JAEA-Conf 2021-001

Figure 5: N /Z distributions as a function of Z number. The left panels show comparison between the conventional and proposed models; the right panels show comparison of the calculation
results between ν = 0 and ν = 3, where ν is the number of neutron emission.

Acknowledgements
The author would like to acknowledge many helpful discussions with the co-author of thiswork [19], Dr. S. Meigo, and Drs. K. Nihsio, T. Sato, T. Ogawa, S. Hashimoto, Y. Iwamoto,T. Fukahori, and T. Kawano. This work was supported by Japan Society fort the Promotion of
Science (JSPS) Grants-in-Aid for Young Scientists B [grant number 17K14916].

29- 29 -

JAEA-Conf 2021-001

 Nuclear spectroscopy at KISS
Yoshikazu HIRAYAMA†1 ,YutakaWATANABE1 , Momo MUKAI2,1,3 ,Hyunsuk CHOI4 ,Murad AHMED ∗2,1 , HironobuISHIYAMA1,2 , Sunchan JEONG1,5 , SotaKIMURA2,1,3 ,Junyoung MOON5 ,Michihiro OYAIZU1 , Jinhyung PARK5 , Peter SCHURY1 ,Michiharu
WADA1 ,and HiroariMIYATAKE1
1
Wako Nuclear Science Center (WNSC), Institute ofParticle andNuclear Studies(IPNS), High Energy Accelerator Research Organization (KEK),Saitama 351-0198,
Japan
2

GraduateSchool ofPure and Applied Sciences, University ofTsukuba, Ibaraki
305-0006,Japan
3
Nishina Center forAccelerator-Based Science, RIKEN, Wako, Saitama351-0198,Japan
4
Department ofPhysics andAstronomy, Seoul National University, Seoul 08826,
Republic ofKorea
5
Rare Isotope Science Project, Institute forBasic Science (IBS), Daejeon, 305-811,
Republic ofKorea†
Email: yoshikazu.hirayama@kek.jp

Abstract
We developed the KEK Isotope Separation System (KISS) for the nuclear spectroscopy ofthe nuclei in the vicinity of N = 126. The spectroscopy is important not only to study
the nuclear structure but also to understand the explosive astrophysical environment for
the formation of the third peak in the observed solar r-abundance pattern. We report theexperimental results of β-γ spectroscopy and in-gas-cell laser ionization spectroscopy for the
nuclei in this heavy region.

1

Introduction

The study of the β-decay half-lives and nuclear masses of waiting-point nuclei with N = 126
is crucial to understand the explosive astrophysical environment for the formation of the third
peak in the observed solar abundance pattern, which is produced by a rapid neutron capture
process (r-process) [1]. For the nuclear spectroscopy in this heavy region, we have developed theKEK Isotope Separation System (KISS) [2, 3]. The KISS is an argon-gas-cell-based laser ion
source combined with an on-line isotope separator [4]. The nuclei around N = 126 are producedby multi-nucleon transfer reactions (MNT) [5] of 136 Xe beam and 198 Pt target [6]. For β-γ decay
spectroscopy to deduce the half-lives, we developed high-eﬃciency detector system, which consists of new gas counter (MSPGC) [7, 8] and Super Clover Ge detectors (SCGe). For precise massmeasurement, we installed a multi-reﬂection time-of-ﬂight mass spectrograph (MRTOF-MS) [9].
The KISS facility enabled us to perform in-gas-cell laser ionization spectroscopy from radiation
measurements by using the β-γ decay detectors and from ion counting particle-identiﬁed byusing the MRTOF-MS. Here, we report the present status and experimental results at KISS.
∗

Present address: Department of Physics, Bangladesh University of Textiles, Dhaka 1208, Bangladesh30- 30 -

JAEA-Conf 2021-001

2

KISS

Figure 1 shows a schematic layout of KISS installed at the RIBF facility in RIKEN. It
consists of the gas-cell system shown in the red box in Fig. 1, the laser system, the massseparator system, the detector station for decay spectroscopy, and the MRTOF-MS for massmeasurements.

Gas cell system
Z selection

Detector station
4 Super Clover Ge for γ-rays
Gas counter for β-ray
Tape transport system

Dipole magnet
Beam deflector
A selection :Concrete wall
m/Δm = 900

Reaction
products
High purity
Ar gasBeam ON (T1/2)

La

se

136

rs

Beam OFF (mass)

MR-TOF-MS

Xe beamArgon gas cell for the accumulation of reaction products
Doughnut-shaped gas cell

Argon gas laminar flow
Water cooledbeam dump

In-gas-cell laser ionization
In-gas-jet laser ionization

λ2
λ1

+
+

Primary beam
136
Xe

+
+

Polyimide foil

TLFs
Rotating target
198
Pt

Mirror
S-shape
pseudo-RFQ

+

Prism

+
+

SPIG

Figure 1: Schematic view of KISS (top), and the KISS gas cell shown in the red box (bottom).

2.1

KISS gas cell system

A primary beam of 136 Xe20+ (∼7 MeV/nucleon, 50 pnA) irradiated production targets suchas enriched 198 Pt (purity 91.63% and thickness 12.5 mg/cm2 ), nat Pt, and nat W [6]. Then, theprimary beam passed through the beam pipe of the doughnut-shaped gas cell [3] (see Fig. 1)
without entering the gas cell, where reaction products of interest are stopped. Finally, the beam
was stopped at a water cooled beam dump, which was placed far from the KISS gas cell.
For increasing the production yield, the doughnut-shaped gas cell (see Fig. 1) was developed to avoid the primary beam passing through the gas cell, otherwise plasma eﬀects [18]signiﬁcantly reduce the eﬃciency to extract the reaction products from the gas cell. Only thetarget-like fragments (TLFs) can be implanted into the gas cell with high eﬃciency, owing to
the characteristic large emission angles of TLFs [2]. Then, the TLFs neutralized in the argon
gas were transported toward the exit by a optimized argon gas laminar ﬂow [3]. We employed
two kinds of two-color two-step laser resonance ionization techniques for selecting the atomic
number Z. By applying the in-gas-cell and in-gas-jet laser ionization techniques, we can produce31- 31 -

JAEA-Conf 2021-001

singly charged ions in this heavy region with Z = 70-78 for β-γ spectroscopy, hyperﬁne structure(HFS) and mass measurements even though these elements are refractory. The in-gas-cell laser
ionization technique is applied for the spectroscopic work which requires higher yields. On theother hand, in-gas-jet laser ionization technique [19], which can selectively ionize ground andisomeric states of the nuclei, is used for much more precise nuclear spectroscopic works.
The laser-produced singly charged (q = 1) ions were transported through a S-shaped pseudoRFQ (S-RFQ) and sextupole ion guide (SPIG), and were accelerated with an energy of 20
kV. Their mass-to-charge ratio (A/q) was selected by a dipole magnet with A/ΔA = 900.
Finally, one kind of isotope was transported to the detector station placed at the neighboring
experimental hall for the nuclear spectroscopy.

2.2

Detector station and MRTOF-MS

The detector station has a tape transport device to avoid accumulation of the radioactivity
from the daughter nuclei of the separated nuclides under the pulsed beam operation of KISS. An
aluminized Mylar tape was moved at the end of each measurement cycle to remove unwanted
radioactivity from the detection area. We developed high-eﬃciency and low-background gas
counter, named multi-segmented proportional gas counter (MSPGC) [7, 8], in order to perform
β-γ and laser spectroscopic studies by detecting β-particles, X-rays, and internal conversion
electrons emitted from rare reaction products. Four Super Clover Ge detectors were installed
to detect β-delayed γ-rays and γ-rays of de-excitation transitions from isomeric states. The
absolute detection eﬃciency for γ-rays with an energy of 400 keV and 1000 keV was measured ashigh as 14% and 10%, respectively, owing to the close setup geometry of approximately 50 mm
from the implantation position on the tape.
We can transport KISS beam to the MRTOF-MS by using an electric deﬂector for producing
pulsed beam during the decay curve measurement at the decay station. Half-lives and masses canbe simultaneously measured in one experiment as shown in Fig. 1. The measured mass resolving
power Rm is more than 200,000 which indicates that only 100-ion accumulation is suﬃcient todetermine a nuclear mass with the mass precision δm/m = 10−6 (δm ≈ 100 keV). The value ofδm ≈ 100 keV satisﬁes with an astrophysical requirement to study the explosive astrophysicalenvironment. The MRTOF-MS has been successfully developed and applied not only to massmeasurements [9] but also to the particle identiﬁcations for further nuclear spectroscopy suchas hyperﬁne measurements.

3

Experimental results

Due to the diﬃculties in the production and ion-extraction of the refractory nuclei in thisheavy region (Z = 70-78 and N ≤ 126), spectroscopic study has been scarcely carried out,
especially, no laser spectroscopic data for the neutron-rich nuclei (limited to stable nuclei andneutron-deﬁcient nuclei). However, we can access the neutron-rich nuclei of these refractoryelements by selecting appropriate production targets at the KISS facility. By using enriched
198 Pt, natural platinum and tungsten targets, we extracted 17 neutron-rich nuclei from the KISS
gas cell for nuclear spectroscopic works. We have successfully performed decay spectroscopyof 195,196,197,198 Os [10, 11, 12], high-K isomer 187 Ta [13] and 192 Re [14], and also perform ingas-cell laser ionization spectroscopy of 199g,199m Pt [15], 196,197,198 Ir [16], and 194,196 Os [17] for
determining the magnetic moments and the change of the charge-radii (deformation parameters).
We plan to perform the laser spectroscopy for these nuclei as well as the β-γ spectroscopy andmass measurements intensively and systematically.
In the following sections, we introduced experimental results of the laser spectroscopy for32- 32 -

JAEA-Conf 2021-001

196,197,198 Ir [16] and the 194,196 Os [17]. In the case of in-gas-cell laser ionization spectroscopy, themeasured laser resonance spectrum is generally broadened by a pressure broadening due to theatomic collision with argon atoms in the gas cell (the gas pressure ∼75 kPa). However, we candeduce an isotope shift value from the measured center of gravity frequency of atomic transitions
and magnetic dipole moment which governs the resonance width and structure. These physics
quantities are very important to discuss the nuclear deformation and structure including a wavefunction.

3.1

Laser spectroscopy of 196,197,198 Ir isotopes

We successfully performed in-gas-cell laser ionization spectroscopy of 196,197,198 Ir [16] for
determining the magnetic moments and the change of the charge-radii (deformation parameters).
Figure 2 shows the measured HFS spectra by detecting the β-rays emitted from each isotope(T1/2 ∼ 10 min) as a function of laser wavelength.
π

−

196

I =1

197

I = 3/2(a) Ir
(T1/2 = 52 s)(b) Ir
(T1/2 = 5.8 m)

198(c) Ir
(T1/2 = 8 s)

π

(d)

+

(e)

π

−

I =1

Figure 2: Measured HFS spectra of (a) 196 Ir, (b) 197 Ir, and (c) 198 Ir. The red lines indicate thebest ﬁt lines with each spin-parity value. (d) Evaluated change of charge radii, and (e) deduced
deformation parameters.
By ﬁtting the measured HFS spectra, we can evaluate the change of charge radii and deformation parameters as shown in Figs. 2-(d) and (e), respectively, from the measured isotope
shifts, and discuss the systematic trend [16]. The magnetic moments (μexp ) with spin-parity
I π can be extracted from the measurements as shown in Table 1, and we can suggest thewave-function of each isotope from the theoretical μcalc calculated by applying strong-coupling
model [20]. In order to determine the magnetic moments with spin-parity and wave-functions
33- 33 -

JAEA-Conf 2021-001

more precisely and explicitly, we have been developing an in-gas-jet collinear laser ionization
spectroscopy technique [19].
Table 1: Results of the in-gas-cell laser ionization spectroscopy of 196,197,198 Ir [16].
NuclideIπμexp (μN ) μcalc (μN ) suggested wave-function
196 Ir−1+0.31+0.04+0.15+0.09
π3/2+ [402] ⊗ ν1/2− [501]
−0.20
−0.03
+0.05
+0.11
−
2
+0.34−0.14 +0.39−0.04 π3/2+ [402] ⊗ ν1/2− [501]197 Ir
3/2+ +0.23+0.10+0.23+0.04
π3/2+ [402]
−0.03
−0.04
+0.10
+0.09
198 Ir−+1+0.13−0.02 +0.16−0.04 π3/2 [402] ⊗ ν1/2− [510]3.2

Laser spectroscopy of 194,196 Os isotopes with the assist of MRTOF-MS

Although we have measured the HFS spectra of short-lived (T1/2 ∼ 10 min) isotopes bydetecting the β- and γ-rays at the KISS facility successfully, it was diﬃcult to measure the HFS
spectra of isotopes with T1/2 > 1 h by detecting the decay radiations in a limited beam time.
However, we can eﬃciently measure the laser resonance spectra of these isotopes thanks to an
ion counting by using the MRTOF-MS without waiting for the radiation decays. The MRTOFMS can identify clearly the isotopes from the mass-dependent time-of-ﬂight (TOF) spectrum asshown in Fig. 3-(a).
(a)
194

196

2+

(b) OsT1/2 = 34.9 m

Pt

194

2+

Os

194

(c) OsT1/2 = 6.0 y

Figure 3: (a) Measured TOF spectrum of laser-induced 194 Os2+ (doubly charged in the MRTOFMS system) with survived ion of non laser-resonant 194 Pt2+ emitted from the platinum production target. Measured laser resonance spectra of (b) 196 Os and (c) 194 Os.
To study the nuclear structures, we successfully measured the laser resonance spectra of=0+ , T1/2 = 34.9 m) and 194 Os (I π =0+ , T1/2 = 6.0 y), as shown in Figs. 3-(b)and (c) respectively, to determine the change in charge radii and the deformation parameters

196 Os (I π34
- 34 -

JAEA-Conf 2021-001

by using the in-gas-cell laser ionization spectroscopy technique assisted by MRTOF-MS [17].
By comparing the evaluated deformation parameters with theoretical values, we found that
194 Os nucleus is oblately deformed and 196 Os nucleus would not be pure axially deformed rotor.
Further systematic measurements of osmium isotopes are planed.

4

Summary

The KEK Isotope Separation System (KISS) was installed at RIKEN to perform nuclear
spectroscopy of neutron-rich isotopes with neutron numbers around 126 for applications in astrophysics. We can successfully extract the neutron-rich isotopes produced by the MNT reactions
from the KISS gas cell. We performed decay spectroscopy of 195,196,197,198 Os, 187 Ta, and 192 Re
isotopes. By using in-gas-cell laser ionization spectroscopy technique, we measured the HFS
spectra of 199g,199m Pt, 196,197,198 Ir, and 194,196 Os isotopes. As the further spectroscopic studies
at KISS, we plan to perform mass measurements by using MRTOF-MS and precise in-gas-jet
laser ionization spectroscopy additionally.

Acknowledgments
This experiment was performed at the RI Beam Factory operated by RIKEN Nishina Centerand CNS, University of Tokyo. The authors acknowledge the RIKEN accelerator staﬀ for theirsupport. This work was supported by JSPS KAKENHI Grant Nos. JP23244060, JP24740180,
JP26247044, JP15H02096, JP17H01132, JP17H06090, and JP18H03711.

References[1] Burbidge E.M. et al., Rev. Mod. Phys., 1957;29:547.
[2] Hirayama Y. et al., Nucl. Instrum. Method B, 2015;353:4.
[3] Hirayama Y. et al., Nucl. Instrum. Method B, 2017;412:11.
[4] Kudryavtsev Yu. et al., Nucl. Instrum. Method B, 1996;114:350.
[5] Dasso C.H. et al., Phys. Rev. Lett., 1994;73:1907.
[6] Watanabe Y.X. et al., Phys. Rev. Lett., 2015;115:172503.
[7] Mukai M. et al., Nucl. Instrum. Method A, 2018;884:1.
[8] Hirayama Y. et al., Nucl. Instrum. Method A, 2021;997:165152.
[9] Schury P. et al., Phys, Rev. C, 2017;95:011305(R).
[10] Hirayama Y. et al., Phys. Rev. C, 2018;98:014321.
[11] Watanabe Y.X et al., Phys. Rev. C, 2020;101:041305(R).
[12] Ahmed M. et al., Phys. Rev. C, 2021;103:054312.
[13] Walker P.M. et al., Phys. Rev. Lett, 2020;125:192505.
[14] Watanabe H. et al., submitted to Phys. Lett. B.
[15] Hirayama Y. et al., Phys. Rev. C, 2017;96:014307.
[16] Mukai M. et al., Phys. Rev. C, 2020;102:054307.
[17] Choi, H. et al., Phys. Rev. C, 2020;102:034309.
[18] Huyse H. et al., Nucl. Instrum. Method B, 2002;187:535.
[19] Kudryavtsev Yu. et al., Nucl. Instrum. Method B, 2013;297:7.
[20] Bohr A, Mottelson B.R., Nuclear structure:volume II Nuclear deformations. Massachusetts(US):W.A. Benjamin, Inc.;1975.
35- 35 -

JAEA-Conf 2021-001

 Production and applications of radioisotopes at RIKEN RI Beam Factory– Chemistry of new elements through diagnosis and therapy of cancer –Hiromitsu HABA*
Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0198, Japan*Email: haba@riken.jp

We are developing production technologies of radioisotopes (RIs) for application studies at RIKEN
RI Beam Factory (RIBF). More than 100 RIs produced at the AVF cyclotron, RIKEN Linear Accelerator,
and RIKEN Ring Cyclotron have been used in research fields of physics, chemistry, biology, engineering,
medicine, pharmaceutical and environmental sciences. In this paper, RIs for superheavy element
chemistry and targeted alpha therapy at RIBF are emphasized. Purified RIs such as 65Zn, 67Cu, and 109Cd
are delivered to universities and research institutes through Japan Radioisotope Association. Short-lived
RIs such as 88Zr, 175Hf, and 211At are also distributed to researchers through the platform for short-lived
RI distribution, supported by JSPS KAKENHI.

1. Introduction
Due to its high sensitivity, the radioactive tracer technique has been successfully applied forinvestigations of the behavior of elements in the fields of physics, chemistry, biology, engineering,
medicine, pharmaceutical and environmental sciences. At RIKEN RI Beam Factory (RIBF), we havebeen developing production technologies of radioisotopes (RIs) for application studies using the AVF
cyclotron (AVF), RIKEN Linear Accelerator (RILAC), and RIKEN Ring Cyclotron (RRC). In this paper,
the production and applications of RIs at RIBF are reported with focus on RIs for superheavy element
chemistry and targeted alpha therapy. Distributions of RIs through Japan Radioisotope Association and
Supply Platform of Short-lived Radioisotopes for Fundamental Research are introduced.

2. Production of RIs at RIBF
First of all, reliable excitation functions are necessary to effectively and quantitatively produce RIsof interest and to reduce contamination of undesired by-products. We have been systematicallyinvestigating the excitation functions especially for the d- and α-induced reactions on various targets at
AVF in collaboration with Sunway University, Malaysia, International Atomic Energy Agency, Austria,
Hokkaido University, and Institute for Nuclear Research (ATOMKI), Hungary. The excitation functions
are compared in detail with the previous ones as well as the theoretical model calculations such as the
TALYS code taken from the TENDL online database [1]. Then, we develop RI production apparatuseson the beam lines of AVF, RRC, and RILAC. We also develop chemical separation procedures to obtain
RIs with high radionuclidic purity, specific radioactivity, and chemical purity. Finally, radioactivity andchemical purity of RIs are specified by γ-ray/α-particle spectrometry and Inductively Coupled Plasma36- 36 -

JAEA-Conf 2021-001

Mass Spectrometry (ICP-MS), respectively.
RIKEN RIs developed for application studies since 2002 are summarized in Table 1. With light- to
heavy-ion beams from the AVF cyclotron, we produce more than 100 RIs from 7Be (atomic number Z =4) to 262Db (Z = 105) [2,3]. RIs for superheavy element chemistry such as 265a,bSg (Z = 106) and 266Bh (Z= 107) are produced using a gas-jet transport system coupled to the GAs-filled Recoil Ion Separator(GARIS) at RILAC [4]. On the other hand, RIs of a large number of elements, called multitracer, aresimultaneously produced from metallic targets such as natAg and 197Au irradiated with a 135 MeV/u 14N
beam from RRC [5].

3. Application studies with RIKEN RIs
The RIKEN RIs have been used in the application studies in collaboration with many researchers in
the world as annually reported in RIKEN Accelerator Progress Reports [6] (See the section “Nuclear
chemistry and Radiochemistry”.) and the references therein. In this paper, we focus on RIs used inchemistry of superheavy elements and targeted alpha therapy.
3.1. Superheavy element chemistry
Chemical characterization of newly-discovered superheavy elements (SHEs, atomic numbers Z ≥104) is an extremely interesting and challenging subject in modern nuclear and radiochemistry [7]. To
start up the SHE chemistry at RIBF, we installed a gas-jet transport system to the focal plane of GARIS[4]. This system is a promising approach for exploring new frontiers in the SHE chemistry: thebackground radiations from unwanted products are strongly suppressed, the intense primary heavy -ionbeam is absent in the gas-jet chamber, and hence the high gas-jet extraction yield is attained. Furthermore,
the beam-free condition makes it possible to investigate new chemical systems. Long-lived SHE RIs of
261a,bRf (Z = 104),

262

Db,

265a,bSg, and266

Bh were produced in the248

Cm(18O,5n)261a,bRf,

Cm(19F,5n)262Db, 248Cm(22Ne,5n)265a,bSg, and 248Cm(23Na,5n)266Bh reactions, respectively, and theirdecay properties were investigated in detail using a rotating wheel apparatus for α and SF spectrometry[8–11]. The decay properties determined for 261a,bRf, 262Db, 265a,bSg, and 266Bh are shown in Figure 1.
Using the GARIS gas-jet system, the first chemical synthesis and gas-chromatogrphic analysis of

248

Sg(CO)6 were successfully conducted under an international collaboration lead by GSI Helmholtzzentrum
für Schwerionenforschung GmbH, Helmholtz Institute Mainz, and University of Mainz, Germany [12].
A detailed experiment to investigate the stability of the metal carbon bond in Sg(CO) 6 is in progress witha thermal decomposition setup developed by Paul Scherrer Institute, Switzerland [13]. Also, syntheses
and properties of Tc, Ru, Rh, and Re carbonyls are under study at Institute of Modern Physics (IMP),
China and RIBF for future studies on Bh, Hs (Z = 108), and Mt (Z = 109) carbonyls [14–16]. To realize
aqueous chemistry studies of Sg and Bh, we have been developing a continuous and rapid solvent
extraction apparatus which consists of a continuous dissolution apparatus Membrane DeGasser (MDG),a Flow Solvent Extractor (FSE), and a liquid scintillation detector for α/SF-spectrometry [17].
A conventional target/gas-jet system for the production of SHE RIs is also available at AVF [18].
The automated batch-type solid-liquid extraction apparatus for repetitive experiments of transactinides(AMBER) was developed by Osaka University, and distribution coefficients of Rf were determined in
HCl [19]. Reversed-phase extraction behavior of Rf with thenoyltrifluoroacetone in HF/HNO3 wasinvestigated using Automated Rapid Chemistry Apparatus (ARCA) developed by Japan Atomic Energy
Agency [20]. Recently, co-precipitation of Rf in basic solutions containing NH 3 or NaOH was37- 37 -

JAEA-Conf 2021-001

investigated in collaboration with Osaka University using a semiautomatic suction filtration apparatus,
CHIN [21].
Table 1. List of radioisotopes developed for application studies at RIBF since 2002.
Nuclides
7

Z

Be

24
28

Na

Reactions

AVF
AVF

nat

AVF

27

nat,43,44

20.91 hNuclidesnat

53.29 d14.9590 h

12Mg

Accelerator

T 1/2

4
11

Li(p,xn)Ce141

Al(α,3p)

Ce

42,43

K

19

12.360 h, 22.3 h

AVF

44m,g

Sc

21

58.6 h, 3.927 h

AVF

Ti

22

49 y

AVF

45

23

15.9735 d

AVF

nat

146

24

21.56 h, 27.702 d

48

V

48,51

Cr

48

Cr

52g,54

Mn

56,57,58

Co

61

AVF

61

265 d

AVF

141

Ca(d,x)

143

*

62

66 s

AVF

144

Sc(d,3n)143,144Eu63

2.63 min, 10.2 s

AVF

144

64

48.27 d

AVF

144

*

70

18.87 min, 11.05 min*Ndnat,44Sm

Ti(p,xn)

Gd

AVF

nat

12

163,164

W74

2.75 s, 6.0 s

RILAC

144

24

169

Hf

*

72

3.24 min

AVF/RILAC

nat

27

77.27 d, 271.79 d, 70.82 d

170

Ta

*

73

6.76 min

AVF/RILAC

nat

RILAC

152

AVF

Yb

nat

AVF

AVF

Fe(d,xn)nat

Zn(d,x)170

nat

Cu(p,xn)

173

nat

173

Zn

30

13.76 h

AVF

74

As

33

17.77 d

AVF

nat

34

119.779 d

AVF

75

Zn(d,x)40

7.86 min

AVF/RILAC

39

106.65 d

AVF

89m

Zr*

40

4.18 min

AVF

*

75

2.40 min

RILAC

nat

Hf

72

70 d

AVF
AVF

90

AVF

nat

2.36 h

AVF

nat

nat

179m

*

74

6.40 min

AVF

nat

nat

180

*

75

2.44 min

AVF

nat

181

W

74

121.2 d

AVF

nat

181

*

75

19.9 h

AVF

nat

nat

Sr(d,xn)

182

Ta

73

114.43 d

AVF

nat

nat

Rb(α,xn)

182a,183,184m,184g

75

12.7 h, 70.0 d, 169 d, 38.0 d

AVF

nat

89

Y(p,xn)

183

AVF

nat

Y(d,xn)

185

W

Re

nat

18

Ge( O,xn)

Re

75

Re
Re

188,189,191

5.67 h

AVF/RILAC

41

10.15 d, 34.975 d

AVF

*

43

4.23 min, 293 min

AVF

Tc

93m

Mo*

Pb

42

6.85 hAVF

Bi

Ge( Ne,xn)

206

*

nat

209

nat

211

22

nat

2.75 h, 293 min

AVF

93

20.0 h, 4.28 d

AVF

nat

20.0 min

AVF

206,207,208,nat

89

8.2 s

RILAC

197

89

10.0 dRRC

232

Bi(α,2n)Th(14N,xnyp)

232

91

1.50 d93

1.54×10 y

*

100

4.2 s

*

102

*

103

22 s

RILAC

209

Lr*

103

0.646 s

AVF

248

No

43

61 d

AVF

42

65.94 h

AVF

nat

257

99

259

*

Mo(d,xn)

255

Lr

AVF

3.1 min

11

Pb( B,x)Au(22Ne,5n)

Np

5

18

Au( O,6n)255

Tc

Th(p,4n)

AVF

232

7

RILAC

208

40

AVF/RILAC

238

AVF

248

Th( Li,3n)

Pb( Ar,3n)U(22Ne,5n)
12

Cm( C,5n)
48

Bi( Ca,2n)Cm(14N,5n)16.1 d

AVF

103

6.3 s

AVF

248

*

46

4.696 min

AVF

nat

Pd(d,x)261a,bRf*

104

68, 1.9 s

AVF/RILAC

248

Ag

*

47

33.5 min, 69.2 min

AVF

nat

Pd(d,xn)

262

*

105

34 s

AVF/RILAC

248

19

Ag

47

7.45 d

AVF

nat

Pd(d,xn)

265a,bSg*

106

8.5, 14.4 s

RILAC

248

Cm( Ne,5n)

22

nat

Ag(p,xn)

266

*

107

10.0 sRILAC

248

Cm( Na,5n)

<22

RRC

nat

45

Rh

109m

Pd

104m,g109

40

Tm( Ar,3n)

245

Mo

111

Tl(p,n)Pb(d,xn)

87

Pa

Zr(α,xn)Ir(d,xn)Pb(p,xn)

nat

*

Fm

Nb(α,2n)

AVF

Ac*

99

93

6.243 d

209

236

nat

83

W(d,2n)Os(α,xn)

203

197

95m

99

AVF

AVF

Ac

Mo(p,n)51.873 h87

229

Mo(d,xn)

82

Re(p,xn)

nat

RILAC

Fr

Nb(α,xn)

95

186

RILAC

225

43

AVF
AVF

93.6 d15.9 sNb(d,2n)4390.64 h10.2 d, 10.87 h, 2.802 d

50.0 s

212

*

AVF

75
78

7.214 h

214

Tc

Tc

95,96

Hf(α,x)W(d,xn)Ta(α,xn)87

Nb(p,n)Zr(α,xn)

93g,94W(d,xn)85

Mo(d,xn)nat

Ta(d,xn)*

93
9370.0 dTa(p,xn)

At

Fr

Zr(d,xn)Ta(d,xn)

nat

169

Fr

Zr(p,xn)

Hf(d,xn)Ta(α,xn)nat

206

Zr(d,xn)

Hf(d,xn)

Hf(α,xn)

nat

Pt

203

Zr(p,xn)

42

92,94

Ge(19F,xn)

nat

Nb

Mo

92m,95

nat

nat

nat

76

Os

186

Y(p,n)

Y(d,2n)

nat

Ta

nat

Re

nat

*

Hf(p,xn)

135 min73

Ta

Sr(α,xn)

AVF

nat

56.56 h, 2.36 h, 1.82 y74

89

18.81 s, 14.60 hLu(d,xn)

73

89

41

Lu(p,xn)

*

W

nat

*

23

Gd( Na,xn)

nat

*

89

AVF/RILAC

22

177

Rb(d,xn)

7.8, 14.5 min

Yb(α,xn)

Gd( Ne,xn)

178a

nat

41

23

Gd( Na,5n)

nat

nat

177,178a,179

Sr(p,xn)

AVF

nat

As(p,n)Rb(p,xn)

AVF

83.4 d, 78.41 h

AVF/RILAC

As(d,2n)Ge(α,xn)

64.84 d40

AVF

7.6 minGa(α,x)38

Zr

23.6 h

74

175

nat

75

88,89

72

Re

Zn(p,α)Zn(d,αn)

69m

75

174

Zn(d,xn)

70

19

Gd( F,xn)

*

9.2 s

18

Gd( O,xn)

*

Hf
W

nat

Gd( C,xn)Sm( Mg,xn)*Re

Cu(d,xn)70

NbPr(α,x)Sm(α,2n)162,163

61.83 h90m,90gPr(d,2n)Sm(d,xn)

Ti(α,xn)

9.49 h, 3.2612 d

Nb**

Sm(d,p2n)Ti(α,2n)29

88m,88gBa(α,x)62.0 sPm

Cr(p,xn)

31

Y

La(d,xn)60

143

Ca(d,x)

46

Ga

88

La(p,xn)

nat

Cu

*

nat

nat

67

Zr

AVF

141

Ti(d,x)

AVF

66,67

85g

32.501 d

AVF

AVF

Sr

58
*

AVF

AVF

85

Reactionsnat

21.56 h3.333 hSe

AVF

5.591 d, 312.3 d244.26 d75

Accelerator

24

29

Zn

T 1/2
137.640 d

25

30

Cu

65

141m

nat

44

Z
58

nat

139

Mg(d,x)

Cd

124

48

462.6 dAVF

51

60.20 d

AVF

52

154 d

AVF

I

53

4.1760 d

AVF

Ba

56

28.7 h

AVF

Sb

121m

Te

124

135m

Ru(p,n)

Lr

nat

Db
Bh

Ag(d,xn)

Multitracer

15

Cm( N,4n)18

Cm( O,5n)Cm( F,5n)23

14Ti( N,xnyp)nat

Sn(d,x)Multitracer*

<29

RRC

nat

nat

Sn(α,xn)

Multitracer

<47

RRC

nat

nat

Multitracer

<72

RRC

nat

14

*

<73

RRC

nat

14

197

Sb(d,xn)

124

Te(d,2n)Multitracer

Cu(14N,xnyp)
14

Ag( N,xnyp)
Hf( N,xnyp)
Ta( N,xnyp)

133

Cs(α,x)Multitracer

<79

RRC

nat

La(d,x)Multitracer*

<83

RRC

209

Multitracer

<90

RRC

232

Au(14N,xnyp)
Bi(14N,xnyp)
14

Th( N,xnyp)* RIs produced with the gas-jet system.

3.2. Production of 211At for Targeted Alpha Therapy
In recent years, the needs for α-particle-emitting RIs for targeted alpha therapy (TAT) is rapidly
increasing in the world. The α particles have a shorter range (40–100 μm) in living tissues than β particles(0.05–12 mm), and have a high linear energy transfer (Ң80 keV/μm), so they are highly cytotoxic. Thus,
medicines labeled with α-particle-emitting RIs are considered to be effective in treating disseminatedcancer, blood cancer, micrometastasis cancer, and microcancer remaining in a postoperative site. 211At(a)

248Cm(22Ne,5n)265a,bSg

α (bα = 100%)

(b)

265Sg

248Cm(23Na,5n)266Bhab
8.5 s 14.4 s

α (bα = 100%)

8.84 MeV (Iα = 91/9%)

248Cm(18O,5n)261a,bRf

α (bα = 100%)

261Rf

10.0 s

8.62–9.40 MeV (Iα = ?)α (bα = 100%)

8.69 MeV (Iα = 20/80%)ab
68 s 2.6 s

248Cm(19F,5n)262Db

α (bα = 48%)

8.46 MeV (Iα = 70%)

8.28 MeV (Iα = 100%)

257No

266Bh

262Db
34 s

8.68 MeV (Iα = 30%)α (bα =
18%)

SF (bSF = 82%)

EC
(bEC = 2.6%)

8.51 MeV (Iα = 100%)

24.5 s258Lr

SF(bSF = 52%)

3.5 s

258No

α (bα = 100%)

8.222 MeV (Iα = 83%)

α (bα = 97.4%)

8.323 MeV (Iα = 17%)~1.2 ms

8.565 MeV (Iα = 20%)8.595 MeV (Iα = 46%)8.621 MeV (Iα = 25%)8.654 MeV (Iα = 9%)SF(bSF = 100%)

Figure 1. Decay pattern for the chains (a) 265a,bSg Ѝ 261a,bRf Ѝ 257No Ѝand (b) 266Bh Ѝ 262Db Ѝ 258Lr Ѝ 258No Ѝ [8–11].
38- 38 -

JAEA-Conf 2021-001

decays to the stable nuclide 207Pb by emitting an α particle with the half-life of 7.214 h. 211At is producedin the 209Bi(α,2n)211At reaction by irradiating a metallic 209Bi target with α particles accelerated by acyclotron. The optimum incident beam energy for the production is Ң28 MeV in order to minimalize theproduction of 210At in the 209Bi(α,3n)210At reaction: 210At decays to the long-lived and toxic 210Po by anelectron capture. Since the half-life of 211At is very short, it is difficult to import 211At from abroad anddomestic production is essential. In order to realize the radionuclide therapy with 211At in Japan, it isnecessary to establish a platform for the production and supply of 211At among domestic accelerator
facilities that have large accelerators. Since 2015, we have been developing a production technology of
211At at AVF and distributing it to 16 research groups in Japan [22].

Figure 2 shows a schematic and photos of the 211At production system developed at RIBF. The
metallic 209Bi target is irradiated with α particles accelerated to 29.0 MeV by AVF. The beam energy iscontrolled with an accuracy of ±1% using a time-of-flight (TOF) beam energy measuring device. The
metallic 209Bi target in 20 mg/cm2 thickness is prepared by a vacuum evaporation method on an Al plate.
Since the melting point of the Bi metal is low (271.5 °C), the target placed at an angle of 15° with respect
to the beam axis is effectively cooled by water (1.5 L/min) and He (30 L/min). In addition, the beam axis
is rotated at 120 rpm by an electromagnet (beam wobbler) to reduce heat load on the target. The current
setup can accept a beam intensity up to 40 μA to produce 2 GBq of 211At in 1 h. After irradiation, as
shown in Figure 2 (c), the Bi target is placed on a Cu boat in a quartz tube (i.d. 30 mm  L180 mm),and O2 is passed through the tube (20 mL/min). The quart tube is heated up to 850 °C with an electric
furnace. 211At sublimated from the 209Bi target is transported to a PFA tube (i.d. 1 mmL1000 mm)
bound in a spiral and cooled to –100 °C with a chiller. After collecting 211At, the inside of the PFA tube
is washed with a few hundred μL of pure water, methanol, chloroform, etc. to recover 211At. The chemicalyield is >80%. The purified 211At is shipped to universities and research institutes in Japan to develop
novel nuclear medicines for cancer therapy [23–25].

(a)
29-MeV α beam

Cooling He (30 L/min)
209Bi target‫ق‬20 mg/cm2‫ك‬

Be window(10 μm)Beam wobbler(120 rpm) Beam energy monitor(TOF detector)

Cooling water(1.5 L/min)
0(b)

50 [mm](c)

Figure 2. (a) Schematic of the target chamber for 211At production. (b) Photo of the target chamber. (c)Photo of a dry distillation apparatus for 211At separation.
225Ac is also one of the most promising α-particle-emitting RIs for TAT. However, a stable supply

39- 39 -

JAEA-Conf 2021-001

system of 225Ac has not yet been established in Japan even at the basic research scale (~100 MBq). Thus,
we started to develop the production technologies of226

Ra(p,2n)

225

225Ac

in the232Th(14N,xnyp)225Ac

andAc reactions using RRC and AVF, respectively.

4. Distributions of RIKEN RIs
Since 2007, the purified RIs of 65Zn, 67Cu, 85Sr, 88Y, and 109Cd are delivered to Japan Radioisotope
Association for fee-based distribution to more than 40 universities, research institutes, and companies inJapan. More than 150 deliveries have been conducted until March, 2020. The RIKEN RIs such as 88Zr,
95Nb, 175Hf, 179Ta, and 211At are also available under the JSPS KAKENHI program “Supply Platform of

Short-lived Radioisotopes for Fundamental Research” in collaboration with Research Center for Nuclear
Physics, Osaka University, Cyclotron and Radioisotope Center and Research Center for Electron Photon
Science, Tohoku University, National Institute of Radiological Sciences and Takasaki Advanced
Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology[26]. Until March, 2020, RIBF accepted a total of 99 orders for 23 research projects.

5. Summary
Present status of the production and applications of RIs at RIBF is briefly reviewed. RIs for SHE
chemistry and TAT are highlighted. Very recently, the RILAC facility was upgraded as SRILAC with a
28 GHz superconducting ECR ion source, a super-conducting quarter-wavelength resonator, and a newgas-filled recoil ion separator (GARIS III) being installed. The SRILAC facility is expected to open thenext generation RI applications at RIBF with an order of magnitude larger production yields. Using
Superconducting Ring Cyclotron and the fragment separator BigRIPS, RIBF can generate more than
3,000 RI beams with the world’s highest intensity. In near future, the RI beams will be used for application
studies by implanting them into various materials such as water and pharmaceuticals.

References[1] TALYS-based evaluated nuclear data library, https://tendl.web.psi.ch/tendl_2019/tendl2019.html(accessed 2021-02-25).
[2] Haba, H. et al., Tracer technique in Handbook of Nuclear Chemistry (2nd ed.), edited by A. Vértes,
S. Nagy, Z. Klencsár, R. G. Lovas, and F. Roesch, vol. 3, Springer, 2010, pp. 1761–1792.
[3] Haba, H., Production of radioisotopes for application studies at RIKEN RI Beam Factory, J. Part.
Accel. Soc. Jpn., 2015; 12: 206–212 (in Japanese).
[4] Haba, H. et al., RIKEN gas-filled recoil ion separator GARIS as a promising interface forsuperheavy element chemistry –Production of element 104, 261Rf, using the GARIS/gas-jet
[5]
[6]
[7]
[8]

system–, Chem. Lett., 2009; 38: 426–427.
Haba, H. et al., Development of a gas-jet-coupled multitarget system for multitracer production,
Radiochim. Acta, 2005; 93: 539–542.
RIKEN Accel. Prog. Rep., https://www.nishina.riken.jp/researcher/APR/index_e.html (accessed2021-02-25).
Haba, H., A new period in superheavy-element hunting, Nat. Chem., 2019; 11: 10–13.
Haba, H. et al., Production and decay properties of the 1.9-s isomeric state in 261Rf, Phys. Rev. C,
2011; 83: 034602.
40- 40 -

JAEA-Conf 2021-001[9] Haba, H. et al., Production of 265Sg in the 248Cm(22Ne,5n)265Sg reaction and decay properties of
two isomeric states in 265Sg, Phys. Rev. C, 2012; 85: 024611.
[10] Haba, H. et al., Production of 262Db in the 248Cm(19F,5n)262Db reaction and decay properties of262
Db and 258Lr, Phys. Rev. C, 2014; 89: 024618.
[11] Haba, H. et al., Production of 266Bh in the 248Cm(23Na,5n)266Bh reaction and its decay properties,
Phys. Rev. C, 2020, 102: 024625.
[12] Even, J. et al., Synthesis and detection of a seaborgium carbonyl complex, Science, 2014; 345:
1491–1493.
[13] Usoltsev, I., Decomposition studies of group 6 hexacarbonyl complexes. Part 1: Production anddecomposition of Mo(CO) 6 and W(CO)6, Radiochim. Acta, 2016; 104: 141–151.
[14]Wang, Y. et al., Gas-phase chemistry of technetium carbonyl complexes, Phys. Chem. Chem. Phys.,2015; 17: 13228–13234.
[15] Cao, S. et al., Gas-phase chemistry of ruthenium and rhodium carbonyl complexes, Phys. Chem.
Chem. Phys., 2016; 18: 119–125.
[16] Wang, Y. et al., The study of rhenium pentacarbonyl complexes using single-atom chemistry ingas phase, Phys. Chem. Chem. Phys., 2019; 21: 7147–7154.
[17] Haba, H., Superheavy element chemistry at GARIS, EPJ Web Conf., 2016; 131: 07006.
[18] Haba, H., Startup of superheavy element chemistry at RIKEN, Eur. Phys. J. D, 2007; 45: 81–86.
[19] Yokokita, T., Observation of the chemical reaction equilibria of element 104, rutherfordium: Solidliquid extraction of Rf, Zr, Hf and Th with Aliquat 336 resin from HCl, Dalton Trans., 2016; 45:
18827–18831.
[20] Yokoyama, A. et al., Extraction behavior of rutherfordium as a cationic fluoride complex with a
TTA chelate extractant from HF/HNO 3 acidic solutions, Radiochim. Acta, 2019; 107: 27–32.
[21] Kasamatsu, Y. et al., Co-precipitation behaviour of single atoms of rutherfordium in basic solutions,Nat. Chem., 2021, DOI: 10.1038/s41557-020-00634-6.
[22] Haba, H., Production of radioisotopes for targeted radionuclide therapy at RIKEN, Drug Delivery
Syst., 2020; 35: 114–120 (in Japanese).
[23] Fujiki, K. et al., 211At-labeled immunoconjugate via a one-pot three-component double click
strategy: Practical access to α-emission cancer radiotherapeutics, Chem. Sci., 2019; 10: 1936–1944.
[24] Ohshima, Y. et al., Preclinical evaluation of new α-radionuclide therapy targeting LAT1: 2[211At]astato-α-methyl-L-phenylalanine in tumor-bearing model, Nucl. Med. Biol., 2020; 9091:15–22.
[25] Takashima, H. et al., Radioimmunotherapy with an 211At-labeled anti-tissue factor antibody
protected by sodium ascorbate, Cancer Sci. (in press).
[26] Supply Platform of Short-lived Radioisotopes for Fundamental Research (in Japanese),https://www.rcnp.osaka-u.ac.jp/~ripf/, (accessed 2021-02-25).

41- 41 -

JAEA-Conf 2021-001

 Measurements of production cross sections of medical radioisotopes
via charged-particle-induced reactions

Masayuki AIKAWA1*
1 Faculty of Science, Hokkaido University
N10W8, Kita-ku, Sapporo 060-0810, Japan*Email: aikawa@sci.hokudai.ac.jp

Production reactions of medical radioisotopes are studied for nuclear medicine. One of such
radioisotopes is 169Yb and its production cross sections of four charged-particle-induced reactions wereexperimentally determined. Physical yields were derived from the measured cross sections. The
comparison of the physical yields indicates that the deuteron-induced reaction on 169Tm is preferable forthe 169Yb production.

1. Introduction
Radioisotopes can be used for a variety of applications, e.g., radiotherapy and diagnosis in nuclear
medicine. There are basically several reactions on stable nuclei to produce each radioisotope.
Investigations of such reactions are necessary to find better reactions with less byproducts and with higher
cost effectiveness. Production cross sections of the radioisotopes are thus important nuclear data.
However, there still exist a lack of data and data with large errors [1]. It is indispensable to obtain moreaccurate and reliable data for the application. Recent technical development of accelerators and detectors
enables us to reach such data.
We study charged-particle-induced reactions among the possible reactions for the production. The
charged-particle-induced reactions have an advantage to be able to produce radioisotopes with atomic
numbers different from those of targets. We expect chemical separation of the products from the targets
and obtain the objective radioisotopes with high specific activity.
One of the medical radioisotopes we focused on is 169Yb(T1/2 = 32.018 d, EC = 100%). It is an Auger electron and Xray emitter and suitable for brachytherapy [2]. To produce
169Yb, there are several reactions, such as proton-, deuteron-and alpha-induced reactions on thulium and alpha-induced
reaction on erbium (Fig. 1). We performed experiments todetermine cross sections of the four reactions [3–5]. The
production cross sections were compared with previous
studies and theoretical model calculation in the TENDL
library [6]. Physical yields of the products for practical use
42- 42 -

167

Yb

17.5 min166

Tm

7.70 h
165

Er10.4 h168

Yb

Stable167

Tm

9.25 d166

ErStable169

Yb

32.0 d168

Tm

93.1 d167

ErStable170

Yb

Stable169

Tm

Stable168

ErStableFig. 1. Nuclear chart around 169Yb.

JAEA-Conf 2021-001

were also derived from the measured cross sections. The results are expected to contribute to nuclear
medicine.

2. Method
The experiments were performed at RIKEN, Japan and ATOMKI, Hungary. The well-developed
methods, stacked-foil activation technique and high-resolution gamma-ray spectrometry, were adopted.
The targets consisted of thin metallic foils for objective and monitor reactions. The stacked targets were
irradiated with beams of the charged particles. The beam intensities were measured by a Faraday cup.
Gamma rays emitted from the irradiated foils without chemical separation were measured by HPGe
detectors. Nuclear data required for deduction of cross sections were retrieved from online databases [7,8].
The cross sections of the monitor reactions were compared with the IAEA recommended values [9]to assess the beam parameters and target thicknesses. According to the comparison of the monitor
reactions, only the beam intensities were corrected within the uncertainties. The corrected intensities andmeasured thicknesses were used to deduce the production cross sections of 169Yb.
The production cross sections of 169Yb were derived from measured net counts of the 177.21-keV
gamma line (IJ = 22.28%). The more intense gamma lines at 63.12 (IJ = 43.62%) and 197.96 keV (I J =35.93%) were unselected because of possible interference with X rays and the 198.25-keV gamma linefrom the 168Tm decay (T1/2 = 93.1 d).

3. Result and discussion
We measured cross sections of the four reactions, proton- [3], deuteron- [5] and alpha-induced
reactions on 169Tm and alpha-induced reaction on natEr [4]. Physical yields were derived from themeasured cross sections and compared with each other. The most appropriate reaction for the 169Yb
production among them was discussed based on the comparison.
3.1. 169Tm(p,n)169Yb reaction
The cross sections of the 169Tm(p,n)169Yb reaction were determined as shown in Fig. 2 [3]. The result
is compared with the previous experimental data [10–12] and the TENDL-2019 values [6]. The peak
amplitude and position are consistent with Birattari et al. [10]. The data of Spahn et al. [11] are two times
larger than ours. The shape of the TENDL-2019 data is different from the experimental data.
3.2. 169Tm(d,2n)169Yb reaction
The excitation function of the 169Tm(d,2n) 169Yb reaction was measured [5]. The result is shown in
Fig. 3 together with the earlier measured experimental data [13,14] and the TENDL-2019 values [6]. The
peak position is in good agreement with the previous experimental data and theoretical calculation
although our result shows slightly higher than the other experimental data.
3.3. 169Tm(D,x)169Yb reaction
We performed two experiments to measure the cross sections of the 169Tm(D,x)169Yb reaction. The
cooling times were longer than 86.9 d and 36.5 d for the first and the second experiments. During thecooling times, the co-produced parent nucleus 169Lu (T1/2 = 34.06 h) had entirely decayed to 169Yb.
43- 43 -

JAEA-Conf 2021-001

Fig. 2. Excitation function of the
169Tm(p,n)169Yb reaction with the previous

Fig. 3. Excitation function of the 169Tm(d,2n) 169Yb

data [13,14] and the TENDL-2019 values [6].

TENDL-2019 values [6].

Fig. 4. Excitation function of the
169Tm(D,x)169Yb reaction with the TENDL-

Fig. 5. Excitation function of the natEr(D,x)169Yb
reaction with the previous data [15–18] and the2019 values [6].

TENDL-2019 values [6].

reaction with the previous data [13,14] and theTherefore, the cumulative cross sections could be obtained. The results are shown in Fig. 4 with the
TENDL-2019 values [6]. The TENDL-2019 values are very different from our result. There is no previous
study found in a literature survey.
3.4. natEr(D,x)169Yb reaction
The cross sections of the natEr(D,x)169Yb reaction were experimentally determined [4]. The result isshown in Fig. 5 in comparison with the previous studies [15–18] and the TENDL-2019 values [6]. Bothdata of Király et al. [17] and TENDL-2019 have nearly the same peak position as ours at around 35 MeV
while the amplitudes are different. The other experimental data differ significantly in both the shape a nd
amplitude from our results.
3.5. Physical yield of 169Yb
Physical yields of 169Yb in the proton-, deuteron-, alpha-induced reactions on 169Tm and alphainduced reaction on natEr were derived from the measured cross sections. The results are shown in Fig. 6and found that the deuteron-induced reaction on 169Tm is preferable to produce 169Yb. We can obtain
169Yb without any radioactive impurities using chemical separation because co-produced 168Yb and 170Yb
are stable.
44- 44 -

JAEA-Conf 2021-001

Fig. 6. Physical yields derived from the measured cross sections.

4. Conclusion
The production reactions of the medical radioisotope 169Yb were investigated. The cross sections offour charged-particle-induced reactions were measured in RIKEN, Japan and ATOMKI, Hungary.
Physical yields were determined from the measured cross sections and compared with each other.
According to the comparison, the deuteron-induced reaction on 169Tm is the most appropriate for the
production.

References







Capote R, Nichols AL, Nortier FM, et al. IAEA coordinated research project on nuclear data
for charged-particle monitor reactions and medical isotope production EPJ Web Conf.
2017;146:08007.
Leonard KL, DiPetrillo TA, Munro JJ, et al. A novel ytterbium-169 brachytherapy source and
delivery system for use in conjunction with minimally invasive wedge resection of early-stage
lung cancer Brachytherapy 2011;10:163–169.
Saito M, Aikawa M, Murata T, et al. Production cross sections of 169Yb by the proton-induced
reaction on 169Tm Nucl Instruments Methods Phys Res Sect B 2020;471:13–16.
Saito M, Aikawa M, Sakaguchi M, et al. Production cross sections of ytterbium and thulium
radioisotopes in alpha-induced nuclear reactions on natural erbium Appl Radiat Isot






2019;154:108874.
Saito M, Aikawa M, Komori Y, et al. Production cross sections of 169Yb and Tm isotopes in
deuteron-induced reactions on 169Tm Appl Radiat Isot 2017;125:23–26.
Koning AJ, Rochman D, Sublet J, et al. TENDL: Complete Nuclear Data Library for Innovative
Nuclear Science and TechnologyNucl Data Sheets 2019;155:1–55.
International Atomic Energy Agency LiveChart of Nuclides [Internet] 2009 Available from:https://www-nds.iaea.org/livechart/>FLWHG-DQ@
National Nuclear Data Center Nuclear structure and decay data on-line library Nudat 2.845- 45 -

JAEA-Conf 2021-001[Internet]. 2019 Available from: http://www.nndc.bnl.gov/nudat2/>FLWHG-DQ@

Hermanne A, Ignatyuk A V., Capote R, et al. Reference Cross Sections for Charged-particle
Monitor Reactions Nucl Data Sheets 2018;148:338–382.



Birattari C, Gadioli E, Gadioli Erba E, et al. PRE-EQUILIBRIUM PROCESSES IN (p,n)
REACTIONS Nucl Phys A 1973;201:579–592.



Spahn I, Takács S, Shubin YN, et al. Cross-section measurement of the 169Tm(p,n) reaction for
the production of the therapeutic radionuclide 169Yb and comparison with its reactor-based

generation Appl Radiat Isot 2005;63:235–239.
 Tárkányi F, Hermanne A, Takács S, et al. Activation cross-sections of proton induced nuclear
reactions on thulium in the 20-45MeV energy range Appl Radiat Isot 2012;70:309–314.
Hermanne A, Tárkányi F, Takács S, et al. Excitation functions for production of medically
relevant radioisotopes in deuteron irradiations of Pr and Tm targets Nucl Instruments Methods
Phys Res Sect B 2009;267:727–736.



Tárkányi F, Hermanne A, Takács S, et al. Activation cross sections of the 169Tm(d,2n) reaction
for production of the therapeutic radionuclide 169Yb Appl Radiat Isot 2007;65:663–668.



Homma Y, Sugitani Y, Matsui Y, et al. Cyclotron production of 167Tm from natural erbium and
natural holmium Appl Radiat Isot 1980;31:505–508.



Sonzogni AA, Romo ASMA, Ozafran MJ, et al. Alpha-induced reactions on natural erbium J
Radioanal Nucl Chem Lett 1992;165:295–303.



Király B, Tárkányi F, Takács S, et al. Excitation functions of alpha-induced nuclear reactionson natural erbium Nucl Instruments Methods Phys Res Sect B 2008;266:549–554.

Archenti A, Wasilevsky C, De La Vega Vedoya M, et al. (α,xn) Reactions on Natural ErbiumRadiochim Acta 1985;38:65–68.

Acknowledgements
This work was carried out at RI Beam Factory operated by RIKEN Nishina Center and CNS,
University of Tokyo, Japan. A part of this work was supported by JSPS KAKENHI Grant Number
17K07004.

46- 46 -

JAEA-Conf 2021-001

 Development of Radioisotopes Production Methodby Accelerator-based Neutron-$ctivity at Kyushu 8niversity 2020 -Tadahiro KIN 1*
1Department of Advanced Energy Engineering Science, Kyushu University
1-6 Kasuga-koen Kasuga-shi., Fukuoka-ken, 816-8580, Japan

Radioisotopes (RIs) production using deuteron accelerator-based neutrons has been studying at
Kyushu University. We primarily focus on neutrons generated via the C or Be(d, n) reactions in a target
whose thickness is thicker than the deuteron range. These reactions are selected because (1) high intense
neutrons having high kinetic energy can generate by the elastic and non-elastic breakup reaction of
deuterons, and (2) neutron energy spectrum has a maximum of around a half incident deuteron energy,i.e., varying deuteron energy guides the spectrum shape adjustment. The two approaches have conducted
the study: proposal of new production routes and new RIs with the accelerator-based neutron method andsystematic measurements of double-differential thick-target neutron yields (DDTTNYs) up to 40 MeV.
The present paper shows some examples of past works ( 92Y production for biodistribution assessment
and 132Cs production for alternative environment tracer as 137Cs), and current status (systematic DDTTNY
measurement results) of our project.

1. Introduction
Recently, the accelerator-based neutron has been widely applied in various fields. In this decade,medical radioisotopes (RIs) production using the neutron has been proposed by Nagai et al. First in the
research, the production method of 99Mo, which is the mother nuclide of the most used medical RI, 99mTc,
was proposed [1,2]. In the study, deuterons are accelerated to around 100 keV and bombarded on a tritium
target to obtain neutrons by DT fusion reactions. Generated neutrons have nearly monoenergetic around
14 MeV, where the 99Mo production reaction 100Mo(n,2n) has a large cross section. The study reveals thatthe production method can generate a sufficient amount of 99Mo of the world demand. We have also
proposed the 64Cu and 67Cu production methods for other applications by using accelerator-based neutron
via the C(d,n) reaction [3]. These copper RIs are new promising candidates of theranostics, which means
combining therapy and diagnosis. In the proposed route, 40-MeV deuterons are used to generate
accelerator-based neutrons to obtain intense flux. The amount of the RIs is estimated to be sufficient forclinical use (a few hundreds of MBq for diagnosis, a few GBq for therapy). The accelerator-based neutron
method by deuterons was summarized as a GRAND system in Ref.[4].
We started studying the RI production method by the accelerator-based neutron in 2012 when I
moved from Prof. Nagai’s group at JAEA to Prof. Watanabe’s laboratory at Kyushu University. At that47
- 47 -

JAEA-Conf 2021-001

time, Kyushu University already gets started a nuclear data study on deuteron-induced reactions[5,6].
Thus, our research has not only been a part of the GRAND project but also combined with the nuclear
data study[7–12].
In our study, the C or Be(d,n) reactions havebeen used to produce the accelerator-based neutron
because the neutron energy distribution can be
adjusted by incident deuteron energy. It means
users can roughly control the radioactive andisotopic purity of produced RIs. Some of RIs havebeen investigated to find the appropriate deuteronenergy to obtain sufficient quantity with high purity.
Moreover, for clinical use, the chemical separation
Fig. 1 Objectives of radioisotopes production
by the accelerator-based neutron method.

process has also been studied. In this paper, first,
two RI (92Y and 132Cs) production routes proposedin our study are reviewed[7,12].

Second, I introduce the latest publication of systematic measurement of thick -target neutron-yieldof C(d,n) [10]. Third, the preliminary result of uncertainty propagation in neutron spectra [13]. Finally, I
summarize the paper and show prospects.

2. New Route to Produce 92Y and 132Cs
2.1. Yttrium-92 production for Assessment of Biodistribution of 90Y-labeled ibritumomab tiuxetan
This section reviews a proposal of 92Y to improve the precision of assessment for metabolic
distribution of 90Y ibritumomab tiuxetan (see Ref. [7] for detail).
Yttrium-90 ibritumomab tiuxetan is the first radio immune therapy agent approved by the US Foodand Drug Administration (USFDA) and followed by more than 40 other countries, including Japan. Until
November 2011, biodistribution is assessed using a single photo emission computed tomography(SPECT) scan by administering 111In-ibritumomab tiuxetan before 90Y-ibritumomab tiuxetan therapy was
required in the United States, Japan, and Switzerland to predict radiation dose to normal tissues andorgans. The FDA, however, removed this procedure based on a clinical study. The main reason was“analysis of data in 253 patients showed that the In-111 imaging was not a reliable predictor of altered
Y-90 Zevalin (the trade name of ibritumomab tiuxetan) bio-distribution”. Suppose a yttrium isotope thatemits gamma rays labels the ibritumomab tiuxetan that emits positron or suitable gamma rays. In thatcase, such a procedure will constitute a reliable monitor by the adoption of positron emission tomography(PET) or gamma-ray imaging. Two radioactive yttrium isotopes have been proposed by Rösche et al. [14]and Nagai et al. [15]. In the present study, we have proposed gamma-emitter, 92Y, which can be produced
only by accelerator-based neutrons, for precise assessment of biodistribution (see Fig. 2).

48- 48 -

JAEA-Conf 2021-001

Fig. 2 Production routes of radioactive
yttrium isotopes. The 92Y proposed in the present
study can only be produced via the fast neutroninduced method.

Fig. 3 Neutron excitation functions of 92Zr
stored in JENDL-4.0u.

The production route is 92Zr(n,p) reactions, and its theoretical neutron excitation function is shown in
Fig. 3 together with other ones of byproduct for 92Zr (note that the functions are available in JENDL-4.0u[16]). We have conducted a thick-target neutron yield (TTNY) measurement of C(d,n) reactions for 20MeV deuterons at Cyclotron and Radioisotope Center (CYRIC) at Tohoku University to estimate theproduction amount and isotopic purity of 92Y product. We adopted the multiple foils activation methods
to derive the TTND. As shown in Fig. 4, deuterons were accelerated up to 20 MeV by AVF930 cyclotron
and guided to the thick carbon target installed in the 32 course to irradiate multiple foils made of Al, Fe,
Co, Ni, Zn, Zr, Mo at the irradiation point for 19 hours. The average beam current on the carbon target
was 2 μA.

Fig. 4 AVF930 type accelerator used to measure the thick-target neutron yield of C(d,n) reactions
using the multiple foils activation methods at the 32 course. Neutrons emitted around 0 degrees
concerning the beam axis were collimated and bombarded on the multiple foils at the irradiation point.
The TTNY was derived from activities induced by the neutron irradiation by unfolding process using
GRAVEL code [17]. For the next step, using the derived TTNY, a production simulation was conducted
for 20 g of enriched 92Zr target irradiation to estimate the production amount and purity. As a result, wefound 1.32 GBq of high isotopic purity (94.9%) 92Y can be produced by a 2-mA deuteron beam on the
carbon target for 7.5-h irradiation. This amount can be used for around ten patients of biodistribution
assessments.
2.2. Environment tracer Cs-132, the alternative of Cs-137
In the environment study of radioactive cesium, 137Cs (T1/2 = 30 y) has been well used to know
49
- 49 -

JAEA-Conf 2021-001

environmental dynamics even if some studies are focused on the short period (around from a few days toa few weeks) dynamics. The half-life is too long for the task, and management of the tracer after anexperiment has been a heavy load of research works. To improve this situation, we have proposed 132Cs
as an alternative tracer of 137Cs for studies of the short period dynamics, e.g., a few days dynamics(dominant period for absorption into the soil) of radioactive cesium released by the Fukushima Daiichi
Nuclear Power Plant Accident. The radioactive material management is straightforward because it has adrastically shorter half-life (6.5 d) than 137Cs. In the present study, we conducted a production experimentof the 132Cs using an accelerator-based neutron method to investigate production amount and radioactive
purity. The accelerator-based neutron irradiated a 12-g Cs2CO3 sample via the C(d,n) reactions by 1.2 μA
of 30-MeV deuterons as a similar irradiation system in Fig. 4. As a result, 102 kBq/g of 132Cs was obtainedwith higher than 98.5% radioactive purity. Following that, a feasibility study of cesium distribution
measurement in andosol soil, which is a typical species of soil in Japan, was performed. The NaI(Tl)detector was placed through a lead collimator having a 1-cm window, as shown in Fig. 5 (left). First, weflow cesium aqueous into the soil and measure the initial distribution (the blue line in Fig. 5 (right)).
After 8-h adsorption time, distilled water was flowed to remove free cesium. Finally, adsorbed
distribution was measured as shown in the red line in Fig. 5 (right). We found almost all of the cesium isadsorbed in andosol soil in a short period, 8 hours. The property is well known, but we concluded the
produced 132Cs tracer could be an alternative to environment tracer 137Cs.

Fig. 5 Setup of measurement of radioactive cesium distribution (left) and its results. The blue line
shows the initial allocation, and the red line shows the distribution after water flow with an 8-hour
adsorption time.

3. Systematic Measurement of Double-differential Thick-target Neutron Yield ofC(d,n) reaction
The neutron generation by the C(d,n) reaction on a thick target is promising for radioisotope
production by accelerator-based neutron method. As mentioned above, an intense neutron field is possible
coincidently with adjustment of neutron energy distribution by incident deuteron energy. For thisapplication, the thick-target neutron yield of wide neutron emission angles (0-90degs) from 10 to 40MeV incident deuterons is necessary to estimate production amount and isotopic purity. However, the50- 50 -

JAEA-Conf 2021-001

nuclear data has not been systematically measured by a single facility with the same irradiation conditions.
To improve this situation, we have conducted a series of double-differential thick-target neutron yieldmeasurements for C(d,n) reaction at 12, 20, and 30 MeV deuterons for neutron emission angles 0, 10, 20,
30, and 45 degrees at Tandem accelerator facility of JAEA. The experimental results are compared withclose deuteron energy and neutron emission angles. See Ref. [10] for the results and details.

4. Summary
We have proposed new radioisotopes (RIs) or new production routes possible by accelerator-based
neutron methods. Experiments of RIs production to know production amounts and find appropriate
chemical separation methods. Also, double-differential thick-target neutron yields (DDTTNYs) of the
proposed route have been measured to estimate isotopic purity, including stable isotope byproducts.
Furthermore, the DDTTNYs have been systematically (in neutron emission angle and incident
deuteron energy) measured for storing nuclear data of deuteron-induced reactions. The experiments havebeen conducted at Cyclotron and Radioisotope Center at Tohoku University and Tandem accelerator at
Japan Atomic Energy Agency. At this moment, we conclude the DEURACS model [18] gives precise
DDTTNYs for C(d,n) reactions in the measured incident energy range from 12 to 35 MeV, especially ataround 0 degrees.
The effort to find the new route or RIs will be continued in the future. Moreover, we will analyze
nuclear data uncertainty contributions in the unfolding process by random sampling method using
covariance for worthful nuclear data measurement.

References>@ Nagai Y, Hatsukawa Y. Production of 99Mo for nuclear medicine by 100Mo(n, 2n) 99Mo J Phys SocJapan 2009;78:12–15.
>@ Nagai Y, Hatsukawa Y, Kin T, et al. Successful labeling of 99mTc-MDP using 99mTc separated from99

Mo produced by 100Mo(n,2n)99Mo J Phys Soc Japan. 2011;80:4–7.

>@ Kin T, Nagai Y, Iwamoto N, et al. New production routes for medical isotopes 64Cu and 67Cu using
accelerator neutrons J Phys Soc Japan. 2013;82:1–8.
>@ Nagai Y, Hashimoto K, Hatsukawa Y, et al. Generation of radioisotopes with accelerator neutrons
by deuterons J Phys Soc Japan 2013;82:1–7.
>@ Araki S, Watanabe Y, Kitajima M, et al. Systematic measurement of double -differential neutron
production cross sections for deuteron-induced reactions at an incident energy of 102 MeV Nucl
Instruments Methods Phys Res Sect A Accel Spectrometers, Detect Assoc Equip [Internet]

2017;842:62–70, Available from: https://doi.org/10.1016/j.nima.2016.10.043.
2017;842:62–70
http://dx.doi.org/10.1016/j.nima.2016.10.043.
>@ Nakayama S, Kouno H, Watanabe Y, et al. Theoretical model analysis of (d,xn) reactions on
Be and 12C at incident energies up to 50 MeV PhysRevC94014618.

9>@ Kin T, Sanzen Y, Kamida M, et al. Production of 92Y via the 92Zr(n, p) reaction using the C(d, n)
accelerator neutron source EPJ Web Conf 2017;146:0–3.
>@ Kin T, Kawagoe T, Araki S, et al. Production of high-purity medical radio isotope 64Cu with
accelerator-based neutrons generated with 9 and 12 MeV deuterons J Nucl Sci Technol54
1123–1130.
>@ Watanabe Y, Kin T, Araki S, et al. Deuteron nuclear data for the design of accelerator -based51- 51 -

JAEA-Conf 2021-001

neutron sources: Measurement, model analysis, evaluation, and application EPJ Web Conf 2017.
>@

Patwary MKA, Kin T, Aoki K, et al. Measurement of double-differential thick-target neutronyieldsof the C(d,n) reaction at 12, 20, and 30 MeV J Nucl Sci Technol 2021;58:252 –Available from:https://doi.org/10.1080/00223131.2020.1819908.

>@

Patwary MKA, Kin T, Araki N, et al. Feasibility study of radioisotope132Cs production using
accelerator-based neutrons Evergreen 2019;6.

>@

Kin T, Araki N, Patwary MKA, et al. Production method of environmental tracer 132Cs by
accelerator-based neutron. EPJ Web Conf 2020;239:20002.

>@

Aoki K, Kin T, Patwary MKA, et al. Development of MC-based uncertainty estimation techniqueof
unfolded neutron spectrum by multiple-foil activation method EPJ Web Conf 2020;239:01021.

>@Rösch F, Qaim SM, Stöcklin G Production of the positron emitting radioisotope 86Y for nuclear
medical application Appl Radiat Isot 1993;44:677–681.

>@

Nagai Y, Iwamoto O, Iwamoto N, et al. Production of an isomeric state of 90Y by fast neutrons fornuclear diagnostics J Phys Soc Japan 2009;78:113201.

>@

Shibata K, Iwamoto O, Nakagawa T, et al. JENDL-4.0: A new library for nuclear science andengineering J Nucl Sci Technol 2011;48:1–30.

>@Matzke M Unfolding of Pulse Height Spectra: The HEPRO Program System Rep PTB-MN-19
1994;

>@

Nakayama S, Kouno H, Watanabe Y, et al. Development of a code system DEURACS for
theoretical analysis and prediction of deuteron-induced reactions EPJ Web Conf 2017;146:100–103.

52- 52 -

JAEA-Conf 2021-001

 *TPUPQF QSPEVDUJPO JO TQBMMBUJPO SFBDUJPO PG ;S/C JOEVDFE CZ QSPUPO BOE EFVUFSPO
BOE,FJUB/","/0p+1"3$ $FOUFS  +BQBO"UPNJD&OFSHZ"HFODZ 5PLBJNVSB *CBSBLJ +BQBOp&NBJM OBLBOPLFJUB!KBFBHPKQ

Nuclear transmutation technology has been attracting attention as a method for treating
high-level radioactive waste. One of the candidates is the spallation reaction using highenergy particles, especially for the nuclides with relatively small neutron-capture cross sections such as long-lived ﬁssion product (LLFP) 93 Zr. The accumulation of nuclear reaction
data and the development of nuclear reaction models based on the data are indispensable forthe accurate prediction of the amount of conversion of 93 Zr to stable nuclides and/or shortlived nuclides and residual long-lived nuclides after the transmutation. Therefore, underthe ImPACT program (Period: 2014 − 2018), we have measured isotope-production crosssections in proton- and deuteron-induced spallation reactions on LLFP 93 Zr and adjacentnuclide 93 Nb at RIKEN RIBF. In the experiment, a 93 Zr beam at 50 MeV/nucleon anda 93 Nb beam at 113 MeV/nucleon were produced by inﬂight-ﬁssion of 238 U. These beams
were irradiated to secondary targets containing hydrogen and deuterium to induce spallation
reactions, and the product yields were analyzed by ZeroDegree Spectrometer to determine
the product cross sections. The results are compared with the nuclear reaction models.

1

Introduction

The problem of the high-level radioactive waste disposal is one of the most important issues in
the nuclear energy ﬁeld. In order to reduce the long-term risk of the high-level radioactive waste,research and development of transmutation technologies have been carried out. However, while
the transmutation of minor actinoids has been studied by fast reactors and accelerator-driven
nuclear transmutation systems [1], the transmutation of long-lived ﬁssion products (LLFPs),
which also have a long-term risk, has not been widely studied. Therefore, transmutation studiesof the LLFPs with half-lives longer than 100,000 years were conducted in the ImPACT program [2]. Among the LLFPs, 93 Zr has a very long half-life of 1.5 million years and a relatively
high ﬁssion yield of approximately 6%. On the other hand, since 93 Zr has a relatively smaller
neutron-capture cross section than other long-lived ﬁssion products [3], it was necessary to explore a new method other than transmutation using a nuclear reactor. Therefore, transmutationof 93 Zr by spallation reactions using high-energy protons and deuterons has been proposed. Inorder to evaluate the performance of this method, isotope-production cross sections for protonand deuteron-induced reactions on 93 Zr, which are the most important data to estimate theamount of transmutation and the radioactivity after irradiation activity, are required.
In this study, we measured the isotope-production cross sections of 50 MeV/nucleon protonand deuteron bombardment on 93 Zr in order to improve nuclear reaction models which will
be used for the study of the LLFP transmutation. The newly measured data are also useful
to discuss the energy dependence of the isotope-production cross sections by combining with53
- 53 -

JAEA-Conf 2021-001

experimental data at 105 and 209 MeV/nucleon [4, 5]. In addition, we measured the isotopeproduction cross sections in 113-MeV/nucleon proton- and deuteron-induced reactions on 93 Nb.
The proton and neutron numbers in 93 Nb are Z = 41 and N = 52, respectively, whereas they
are Z = 40 and N = 53 in 93 Zr. It is interesting to see how the diﬀerence of a single nucleon
in the initial proton and neutron numbers inﬂuences the reproducibility of the nuclear reaction
models by comparing the results with the previous 93 Zr data at 105 MeV/nucleon [4].

2Experiment

Both the 93 Zr and 93 Nb experiments were performed at the RIKEN Radioactive Isotope Beam
Factory (RIBF) using a cocktail beam containing secondary beams of 93 Zr and 93 Nb. Since theexperimental procedures and setups for the 93 Zr and 93 Nb experiments were similar, only thedetails of the 93 Zr experiments will be described here.
In the 93 Zr experiment, the BigRIPS [6] and the ZeroDegree Spectrometer (ZDS) [6] wereused to analyze secondary beams and reaction products, respectively. First, a 238 U primary beam
accelerated up to 345 MeV/nucleon impinged onto a 7-mm-thick 9 Be primary target installedat the entrance of BigRIPS. The secondary beam containing 93 Zr ions was produced throughinﬂight-ﬁssion of the 238 U primary beam. The secondary beam was identiﬁed using beamline
detectors placed in the second-half of the BigRIPS. Then the secondary beam impinged onto asecondary target, cooled gaseous H2 and D2 [7], at the entrance of the ZDS. The residual nuclei
produced in the nuclear reactions with the secondary targets were also identiﬁed by beamline
detectors at ZDS. Seven diﬀerent magnetic-ﬁeld settings Δ (Bρ) /Bρ = −6%, −4%, −2%, 0%,+2%, +4%, and +6% were adopted to measure wide ranges of mass numbers and charge statesof the reaction products. The typical current of the primary beam was approximately 400 enA.

3

Data Analysis

Same as the experimental procedure, since the main procedures of the data analysis of the 93 Zr
and 93 Nb experiments are almost the same, the data analysis only for the 93 Zr will be presented
here.
Particle identiﬁcation of the secondary beam was performed based on the TOF−Bρ − ΔE
method [8] using signals from the beamline detectors. Left panel of Figure 1 shows a twodimensional identiﬁcation plot of the secondary beam by the atomic number Z and the massto-charge ratio A/Q. As shown in the left panel of Figure 1, the secondary beam contains onlyisotones of 93 Zr. Each nuclide was clearly separated with resolutions of 0.45 (FWHM) in Z and
0.28 (FWHM) in A, which are suﬃcient to identify the 93 Zr beam. The events in the ranges
39.6 ≤ Z ≤ 40.4 and 2.319 ≤ A/Q ≤ 2.333 were selected as the 93 Zr beam. The purity, which is
calculated as a ratio of the number of 93 Zr beam in the above-mentioned ranges to the numberof total events, and the typical count rate of 93 Zr were 57.8% and 980 counts per second, respectively. The energy of the 93 Zr beam were 51 and 52 MeV/nucleon at the centers of the H2 andD2 targets, respectively, calculated from the magnetic rigidity of the secondary beam before thesecondary target considering the energy loss in beamline materials using the LISE++ code [9].
The energy spreads in the secondary targets were calculated as ±10 MeV/nucleon.
Same as the particle identiﬁcation of secondary beam, that of the reaction products was
performed based on the TOF−Bρ − ΔE method. Right panel of Figure 1 indicates the identiﬁcation plot of the reaction products from the H2 secondary target at the 0% ZDS Bρ setting
after selecting the 93 Zr beam.
The isotope-production cross sections were determined from the number of incident 93 Zr ionsand the number of each isotope. A systematic uncertainty was estimated to be 4.6% including
54- 54 -

JAEA-Conf 2021-001

Figure 1: Left: Particle identiﬁcation plot of the secondary beam by the atomic number Z
and the mass-to-charge ratio A/Q in the 93 Zr experiment. Right: Particle identiﬁcation plot of
the reaction product from the H2 secondary target after selecting the 93 Zr beam in the 0% Bρ
setting.
uncertainties of the thickness of the secondary target, multiple reactions in the secondary target,
and the energy spread in the secondary target.

4

Results and Discussion on 93 Zr data

Figure 2 shows the measured isotope-production cross sections in the proton- and deuteroninduced reactions on 93 Zr at 50 MeV/nucleon together with those at 105 and 209 MeV/nucleon [4,5]. The black circles are the measured isotope-production cross sections in the proton case, andthe red triangles in deuteron case. The black solid and red dashed lines correspond to calculated
cross sections by PHITS [10] in the proton- and deuteron-induced reactions, respectively. The
upper, middle, and lower panels show the data at 209, 105, and approximately 50 MeV/nucleon,
respectively. The error bars include only the statistical uncertainties. Jumps at the neutron
magic number N = 50, which is pointed out in the previous works [4, 5], are seen in the Zrisotopic chain for both the proton- and deuteron-induced reactions and in the Y-isotopic chain
for the deuteron-induced reaction even in the data at 50 MeV/nucleon. In the Y-isotopic chain,
87 Y has a noticeble large production cross section. This corresponds to the ﬁrst peak of an
excitation function of the 93 Zr(p, x)87 Y reaction around 50 MeV/nucleon.
The PHITS calculations are in good agreement with the measured data even with the newly
measured data. In particular, the trend around 87 Y in the 51-MeV proton-induced reaction was
successfully reproduced by the PHITS calculation. However, discrepancies as seen in the previous works are still observed in the data at 50 MeV/nucleon: one-mass-shifts to the heavy sidein the distribution of the Nb-isotopic chain, underestimations of the production cross sectionsin the neutron-deﬁcient region of Nb- and Y-isotopic chains, overestimations of the production cross sections near the target nucleus 93 Zr, and an exaggerated even-odd staggering in the
Sr-isotopic chain. In terms of the energy dependence of the reproducibility of the PHITS calculations, the ratio of calculation to experimental (C/E) of the 92 Zr and 92 Y production cross55- 55 -

JAEA-Conf 2021-001

Nb (Z = 41)

Zr (Z = 40)

Y (Z = 39)

Sr (Z = 38)

E = 209 MeV/nucleon

102

101

Cross Section [mb]

100

10

E = 105 MeV/nucleon

2

101

100
exp p
exp d
PHITS pPHITS dEp = 51 MeV
Ed = 52 MeV/nucleon

102

101

10

0

75

80

85

90

75

80

85

90

75
80
Mass Number

85

90

75

80

85

90

Figure 2: Isotope-production cross sections for the proton- and deuteron-induced reactions on
93 Zr.
sections are getting worse as the decrease of the incident energy in the proton-induced cases. In
the deuteron-induced cases, on the other hand, the C/E of those have the largest value in thedata at 105 MeV.

5

Results and Discussion on 93 Nb data

Figure 3 shows the measured isotope-production cross sections in the proton- and deuteroninduced reactions on 93 Nb at 113 MeV/nucleon. The black circles and red triangles correspondto the measured data in the proton- and deuteron-induced reactions, respectively. The PHITS
calculations are also plotted by the black solid lines for the proton-induced case and by the reddashed lines for the deuteron-induced case. Although discontinuous jumps at the neutron magic
number N = 50 are observed in the Zr-isotopic chains for both the proton- and deuteron-induced
reactions because of the closed-shell structure, no clear jump appeared in the Nb-isotopic chain.
The PHITS calculations well reproduce the measured isotope-production cross sections as
does the 93 Zr data. Also, the four discrepancies seen in the 93 Zr data are also found in the
93 Nb data. In particular, the underestimations of the production cross sections in the neutrondeﬁcient region of the Nb- and Y-isotopic chains are observed for the both 93 Zr and 93 Nb data.
If the atomic number of the target nuclide increases by one, it might be expected that the atomic
number of the underestimated nuclide also increases by one, that is, cross sections of the Mo- andZr-isotopic chains are expected to be underestimated in 93 Nb data. However, the underestimatedisotopic chains remained the same for both 93 Nb and 93 Zr targets. This demonstrates that the
reproducibility of the calculation is largely inﬂuenced by the ﬁnal nuclides rather than thereaction.
56- 56 -

JAEA-Conf 2021-001

Mo (Z = 42)

Nb (Z = 41)

Zr (Z = 40)

Sr (Z = 38)

Rb (Z = 37)

E = 113 MeV/nucleon

102

Cross Section [mb]

101

10

0

Y (Z = 39)

exp p
exp d
PHITS pPHITS d

2

10

101

0

10

75

80

85

90

75

80

85

90

75

80

85

90

Figure 3: Isotope-production cross sections for the proton- and deuteron-induced reactions on
93 Nb.

6 Summary
Isotope-productioncrosssectionsfortheproton-anddeuteron-inducedreactionson 93 Zratapproximately 50 MeV/nucleon and 93 Nb at 113 MeV/nucleon were measured at RIKEN RIBF.
The measured data are useful to discuss the reaction energy and target nucleus dependences ofthe isotope-production cross sections. The comparison of the 93 Zr data at the three diﬀerent
reaction energies with the PHITS calculations revealed that the four discrepancies are identically seen in the isotope-production cross sections at the reaction energies ranging from 50 to200 MeV/nucleon. In particular, the overestimations of the production cross sections near thetarget nucleus become more serious at the lower reaction energy. The comparison between themeasred93 NbdataandthePHITScalculationsdemonstratesthatthediscrepanciesareobserved
despite the changes of the atomic and mass number by one. Also, the underestimations in theneutron deﬁcient-region are seen in the Nb- and Y-isotopic chains for the both 93 Zr and 93 Nbdata regardless of the diﬀerence of the atomic number of the target nuclei 93 Zr and 93 Nb.

References[1] TsujimotoK,OigawaH,OuchiN,etal. ResearchandDevelopmentProgramonAccelerator
Driven Subcritical System in JAEA  J Nucl Sci Technol  2007;44(3):483-490.
[2] ImPACT Program  https://www.jst.go.jp/impact/program/08.html BDDFTTFE [3] ShibataK,IwamotoO,NakagawaT,etal. JENDL-4.0: ANewLibraryforNuclearScienceand Engineering  J Nucl Sci Technol  2011;48(1):1-30.

57- 57 -

JAEA-Conf 2021-001[4] KawaseS,NakanoK,WatanabeY,etal. Studyofproton-anddeuteron-inducedspallation
reactionsonthelong-livedﬁssionproduct93Zrat105MeV/nucleonininversekinematics
Prog Theor Exp Phys  2017;2017:093D03.
[5] KawaseS,WatanabeY,NakanoK,etal. Measurementofisotopicproductioncrosssectionsof proton- and deuteron-indued reactions on 93Zr at 200 MeV/nucleon  JAEA-Conf
2018-001. 2018;2018:111.
[6] Kubo T, Kameda D, Suzuki H, et al.  BigRIPS separator and ZeroDegree spectrometer at
RIKEN RI Beam Factory  Prog Theor Exp Phys  2012;2012:03C003.
[7] Ryuto H, Kunibu M, Minemura T, et al.  Liquid hydrogen and helium targets for radioisotope beams at RIKEN  Nucl Instrum Meth A  2005;555:1-5.
[8]FukudaN,KuboT,OhnishiT,etal. Identiﬁcationandseparationofradioactiveisotope
beams by the BigRIPS separator at the RIKEN RI Beam Factory  Nucl Instrum Meth B 
2013;317:323-332.
[9] TarasovOBandBazinD LISE++: Exoticbeamproductionwithfragmentseparatorsandtheir design  Nucl Instrum Meth B  2016;376:185-187.
[10] Sato T  Features of Particle and Heavy Ion Transport code System (PHITS) version 3.02
J Nucl Sci Technol  2018;55:684-690.

Acknowledgments
I would like to thank ImPACT-RIBF collaborators for their contributions to the experiment,
advice on data analysis, and fruitful discussion. I would like to thank the accelerator staﬀ
of the RIKEN Nishina center for providing high-quality 238 U primary beam. This works was
funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Oﬃce,
Government of Japan).

58- 58 -

JAEA-Conf 2021-001

 Development of energy-degraded RI beam and expansion of nuclear
reaction studies– Recent results obtained by the OEDO-SHARAQ system –Shin’ichiro MICHIMASA1*
1Center for Nuclear Study, the University of Tokyo
2-1 Hirosawa, Wako, Saitama 351-0198, Japan*Email: mitimasa@cns.s.u-tokyo.ac.jp

The OEDO beamline was developed to promote measurements of nuclear reactions induced byradioactive isotope beams at several tens of MeV/u and to clarify the properties of radioactive nuclei withrespect to their structures and reactions. This report introduces the performance of the OEDO beamline
to produce energy-degraded RI beams and recent experimental studies using the OEDO-SHARAQ system.
In the last section, planned experiments at OEDO are discussed.

1. Introduction
Radioactive isotope (RI) beams are an essential tool to explore the properties of short-lived nuclei.
Recent developments of the RI production are strongly promoting the progress of modern nuclear physics
and especially providing various opportunities to obtain nuclear data of RI’s. Such intense RI beams aremainly provided by two types of RI production schemes: isotope separator on-line (ISOL) method andin-flight method. With the ISOL method, RIs are produced from fission or spallation of a target of heavy
elements induced by electron, proton, or
deuteron beams; once produced, the RIs are
extracted from the production target and reaccelerated ready for the nuclear reaction
studies. In contrast, the in-flight method
produces an RI beam by using the fragments
ejected from the production target. One majordifference between these methods is the beamenergy provided for the measurements. Figure
1 illustrates the characteristics of RI produced
by ISOL or in-flight methods on the massand-energy plane. While these two methods
widely cover the mass-and-energy region,
there exists a blank spot of medium mass
nuclei and several tens of MeV/u.

Figure 1: Characteristics of RI production methods onthe mass-and-energy plane.
59- 59 -

JAEA-Conf 2021-001

The OEDO beamline [1] was designed to access to this blank region. The energy range of several tensof MeV/u is attractive because nuclear transfer and/or energy-dissipation reactions at this energy range
are powerful tools to make clear the structures in exotic nuclei. This article describes the outline of the
OEDO device, involved experiments, and physics topics expected to be explored by OEDO.
1.1. OEDO beamline
Coupled with an in-flight RI separator the OEDO beamline enables us to produce energy-degraded RI
beams. For low-energy reaction studies with short-lived nuclei, beamlines should provide good beamfocusing, improved energy compression, and efficient transmission. The OEDO beamline balances theseproperties by exploiting a time-dependent radiofrequency (RF) ion-optical element installed into thebeamline. At the secondary target OEDO achieved a focus of about 30-mm diameter, a beam energy
spread of 10%, and a good transmission (~30%). This performance of OEDO is appropriate for nuclear
reaction studies with exotic nuclei far from the E-decay stability line.
A schematic layout of the OEDO beamline from BigRIPS to the SHARAQ spectrometer is shown in
Fig. 2. The inset photograph displays the main components of the OEDO beamline, where a RF deflector(RFD) and two superconducting triplet quadrupole (STQ) magnets were recently installed. The BigRIPS
and upstream section of the OEDO beamline are used to produce and purify the RI beam of interest. The
section from FE9 to FE11 in the OEDO beamline serves to degrade the energy of the RI beam. The section
from FE11 to S0 serves to tag the beam for RI-induced reactions.

Figure 2: Schematic layout of the OEDO beamline with the BigRIPS and SHARAQ Spectrometer.
In the energy-degrading section, the beam is tuned to a moderate momentum dispersion of about 15
mm/% at the FE9 focus. At this location a recently developed angle-tunable wedge degrader [2] isinstalled as a monoenergetic degrader, which serves two primary functions The first is to control the beamenergy by selecting a suitable degrader thickness, the second is to minimize the energy spread of outgoing
RI particles by utilizing a position-energy correlation of the dispersive focus. The system consists of twoaligned aluminum plates with quadratically changing thicknesses of the same magnitude, but one concave
the other convex. In the overlapping region, the quadratic component of the total thickness is canceled.
To achieve the monoenergetic condition, the remaining linear component is tuned by adjusting the60- 60 -

JAEA-Conf 2021-001

overlapping region. The ion optics in the FE9-FE10 and FE10-FE11 sections are designed to be point-toparallel and parallel-to-point transport modes, respectively. The RFD, installed at FE10, uses an RF
electric field to provide time-dependent focusing of the beam at FE11 or S0 depending on experimental
requirements. The applied RF high voltage deflects the beam in the horizontal direction. The phase of the
RFD is synchronized with the acceleration phase of the superconducting ring cyclotron (the final stageof the RIBF sequence of accelerators). A secondary target for reaction measurements can be installed at
FE11 or S0. However, during previous experiments, all magnets in the FE10-S0 section were used toestablish point-to-parallel ion-optics to achieve acceptance matching with the SHARAQ spectrometer.
The SHARAQ spectrometer analyses reaction products at the reaction target and identifies beam-likeparticles outgoing from the target. The reaction channel at the target is determined by coupling particle
identification of incoming and outgoing nuclei on an event-by-event basis.
The performance of OEDO beamline was demonstrated through experimental studies. Figure 3 showsa typical performance in energy compression and beam focusing of the OEDO beamline. Figure 3(a)Figure 3: Demonstration of (a) energy compression and (b) beam focusing in the OEDO beamline.
demonstrates the energy compression from 173 MeV/u to 46 MeV/u by using the angle-tunable wedge
degrader system at FE9. The system successfully reduces the beam energy spread from 3.4 MeV/u to 2.7
MeV/u. Figure 3(b) shows position distributions of a 50-MeV/u 77Se beam at FE11 when the OEDO RFD
is on (off) as a red (black) histogram. This demonstrates the excellent focusing potential of the OEDO
beamline. The colored histograms shown in Fig. 3(a) and (b) are from simulations of a beam transport
along the beamline. The consistency between simulated and experimental distributions shows the OEDO
beamline is performing to the designed capability.
1.2. Experimental opportunities with the OEDO-SHARAQ system.
The low-energy RI beams produced by the OEDO beamline are used to induce a nuclear reaction on asecondary target located at FE11 or S0 (see Fig. 2). Beam energies of a few tens of MeV/u are suitable
to populate nucleon- and/or alpha-transfer reactions. Additionally, in this energy range of the beams, themechanism of nuclear reactions smoothly changes from a direct process to pre-equilibrium process, andthus many-quasiparticle states will be produced via inelastic channels. By using such features, OEDO
provides various experimental opportunities to research nuclear structure on short-lived nuclei.
In preparation for reaction measurements, the FE11 and S0 focal planes feature open spaces ofapproximately 1.5 m along the beam axis. These spaces accommodate not only the location of the61- 61 -

JAEA-Conf 2021-001

secondary target but also installation of particle detector arrays to surround the secondary target. The
standard experimental setup is designed for inverse-kinematics reaction measurements on an event-byevent basis. The secondary reaction target is a probe for the interested reaction. For example, solid foils,
confined gases, or confined liquid target are used frequently. For RI beams produced by the OEDO
beamline, a set of tracking detectors installed upstream of the secondary target measures an incident
trajectory. Downstream of the reaction target the beam-like reaction products are analyzed by the
SHARAQ spectrometer to determine their momentum vectors. At the final focal plane of SHARAQ, a'E-E detector array is installed by default to identify the nuclear species. In each reaction event, the data
set of momentum vectors and nuclear species of both incident and outgoing particles enable us to identify
the induced reaction channel and to measure the scattering angle of the reaction products. In addition to
the default detector setup, one may install additional detectors to measure recoil particles around thesecondary target position. As an example of a performed experiment, a particle detector array was
installed to surround the target and it successfully determined excitation energies of the outgoing particles
using the missing-mass spectroscopic technique [4].

2. Recent achievements by using the OEDO-SHARAQ system
This section describes two recent achievements at OEDO, the first being proton-induced reaction
measurements on 93Zr and 107Pd at ~25 MeV/u [5,6], and the second a surrogate (d,p) measurement toestimate (n,J) cross sections on 79Se [4].
2.1. Proton-induced reactions on 107Pd and 93 Zr
A series of proton-induced reaction studies at around 25 MeV/u were performed by using 107Pd and
93 Zr beams. Through the JST-ImPACT program [7], the transmutation cross sections of these nuclei forthe proton- and deuteron-induced reaction cross sections were measured at various incident energies [811]. The cross sections were measured at the lowest incident energy to date and contributed to thesystematic data set. The detector setup was similar to that described in the section 1.1, where the reaction
target was a cooled hydrogen gas target of 5-8 mg/cm2 thickness. Figure 4 shows the energy dependenceof transmutation cross sections of the proton-induced reactions on 107Pd. The present experiments
provided the data in between 20 and 30 MeV/u. In the figure, each color represents a different isotope ofAg or Pd. The solid lines show theoretical estimations of the production cross sections for each isotope.
The predictions reproduce the data within 1 sigma. The enhancement of Ag production is noticeable in
the energy region of 20 MeV/u
and the Ag production amounts
to 80% of the total crosssection. The enhancement is
considered to be caused bycompound nuclear decay of
108Ag *

produced by a protonand 107

Pd. A similar trend wasobserved in proton-induced
reactions on 93Zr, the detailed
reports of which will beavailable soon.

Figure 4: Systematics of transmutation cross sections for Ag and Pd
isotopes.
62- 62 -

JAEA-Conf 2021-001

2.2. Evaluation of the neutron-capture reaction on 79Se by using the (d,p) reaction
We measured the (d,p) reactions on 77,79Se to evaluate the 79Se(n,J) cross section by the surrogate ratio
method [12,13]. For the reaction measurement, a deuterated-polyethylene film of 4 mg/cm2 was selected
as the reaction target. A Si-CsI(Tl) array named TiNA was installed in a geometry surrounding the target
to measure recoil protons. The populated excitation energy of 78,80Se was determined from the proton
momenta on an event-by-event basis, and therefore the J-emission probability distributions were
determined as a function of the excitation energy. The surrogate ratio method enabled estimation ofneutron-capture cross sections of 79Se from the previously measured (n,J) cross sections of 77Se [14], themeasured J-emission distributions, and the formation cross sections of the 78,80Se compound nuclei. The
formation cross sections of 78,80Se were obtainedusing the optical model calculations. The (n,J)
cross sections on 79Se evaluated by the present
J-emission probability are shown in Fig. 5. Thelines in the figure show several of the nuclear
data

evaluations.

The

ENDF/B-VII

canreproduce the current results within theexperimental errors. The report on thisexperiment is in the final stage for publication
and will be available soon [15].

3. Future program

Figure 5: Evaluated (n,J) cross sections on 79Se by
the surrogated 79Se(d,p) reaction at 20 MeV/u.

The production of low-energy RI beams in therange of 10-50 MeV/u has the unique opportunity to excite bombarded nuclei into multi-quasiparticle
states. This feature can possibly enable a new type of nuclear measurement to investigate reaction
mechanisms and nuclear structures. We are planning new experimental studies via such pre-equilibrium
and/or compound nuclear reactions. Since compound nuclear reactions can provide various nucleon
configurations, this method may be useful for experimental studies on shape evolutions including shapecoexistence in RI’s far from the beta stability. Also, we plan to apply the surrogate ratio method used inprevious experimental studies to improve quantitative evaluations of astrophysical (n,J) reaction rates
which strongly affect nucleosynthesis in astrophysical sites [16].

4. Summary
The new beamline OEDO successfully provides suitable energy-degraded RI beams around 20-50
MeV/u for inverse-kinematics reaction measurements by using a new ion-optical scheme. The beam spot
size at FE11 is typically 15 mm (FWHM).
Two series of experiments were performed using the OEDO-SHARAQ system. In the measurement of
the proton-induced transmutation cross sections, new nuclear data on radioactive nuclei 107Pd and 93Zr at
20-30 MeV/u were provided for the first time. 77,79Se beams at 20 MeV/u were used for neutron-transfer
reaction measurements via the (d,p) transfer reaction, and consequently the first experimental evaluationof neutron-capture cross sections on 79Se was provided.

63- 63 -

JAEA-Conf 2021-001

References>@ Michimasa, S., Hwang, J.W., Yamada, K., et al.: OEDO, the energy-degrading beamline at RI
Beam Facility, Prog. Theo. Exp. Phys. 2019, 043D01 (2019).
>@ Hwang, J.W., Michimasa, S., Ota, S., et al.: Angle-tunable wedge degrader for an energydegrading RI beamline, Prog. Theo. Exp. Phys. 2019, 043D02 (2019).
>@ Michimasa, S., Imai, N., Dozono, M., et al.: New energy-degrading beamline for in-flight RI
beams, OEDO, Nucl. Instrum. Methods Phys. Res. B 463, 143 (2020).
>@ Imai, N.: Nuclear reaction data of low-energy LLFP produced by OEDO, Proc. 2017 Symp. On
Nuclear Data, JAEA-Conf 2018-001, 39 (2018).
>@ Dozono, M., Imai, N., Michimasa, S. et al.: Proton- and deuteron-induced reactions on 107Pd
and 93Zr at 20 – 30 MeV/nucleon, RIKEN Accel. Prog. Rep. 52 (2019).
>@ Hwang, J.W., Iribe, K., Dozono, M. et al.: Proton/deuteron-induced reactions of 93Zr using theslow RI beam, CNS annual report 2018, CNS-REP-98, 17 (2020).
>@ ImPACT program “Reduction and Resource Recycling of High-level Radioactive Wastes
through Nuclear Transmutation”, http://www.jst.go.jp/impact/en/program/08.html
DFFHVVHG >@ Wang, H., Otsu, H., Sakurai, H., et al.: Spallation reaction study for the long-lived fission
product 107Pd, Prog. Theo. Exp. Phys. 2017, 021D01 (2017).
>@ Wang, H., Otsu, H., Chiga, N., et al.: Enhancement of element production by incomplete fusion
reaction with weakly bound deuteron, Commun. Phys. 2, 78 (2019).
>@ Kawase, S., Nakano, K., Watanabe, Y., et al.: Study of proton- and deuteron-induced spallation
reactions on the long-lived fission product 93Zr at 105 MeV/nucleon in inverse kinematics, Prog.
Theo., Exp., Phys., 2017, 093D03 (2017).
>@ Nakano, K., Watanabe, Y., Kawase S., et al.: Isotope-production cross sections of residual
nuclei in proton- and deuteron-induced reactions on 93Zr at 50 MeV/u, EPJ Web Conf., 239,
20006 (2020).
>@ Chiba, S., Iwamoto, O.: Verification of the surrogate ratio method, Phys. Rev. C 81, 044604(2010).
>@ Escher, J.E., Dietrich, F.S: Cross sections for neutron capture from surrogate measurements:
An examination of Weisskopf-Ewing and ratio approximations, Phys. Rev. C 81, 024612 (2010).
>@ Kawada, S., Igarashi, M., Katabuchi T., et al.: Measurements of keV-Neutron Capture Cross
Sections and Capture Gamma-Ray Spectra of 77Se, J. Nucl. Sci. Tech. 47, 643 (2010).
>@ Imai, N., Dozono, M., Michimasa, S. et al.: to be submitted.
>@ Mumpower, M.R., Surman, R., McLaughlin, G.C., et al.: The impact of individual nuclear
properties on r-process nucleosynthesis, Prog. Part. and Nucl. Phys. 86, 86 (2016).

Acknowledgements
We thank the RIKEN Nishina Center and the CNS, the University of Tokyo accelerator staff for the
excellent beam delivery. The work was funded by ImPACT Program of Council for Science, Technology
and Innovation (Cabinet Office, Government of Japan).

64- 64 -

JAEA-Conf 2021-001

 Theoretical analysis of deuteron-induced reactions
and development of deuteron nuclear database
Shinsuke NAKAYAMA
Nuclear Data Center, Japan Atomic Energy Agency
2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
Email: nakayama.shinsuke@jaea.go.jp
Intensive fast neutron sources using deuteron accelerators have been proposed for various
applications. Toward evaluation of deuteron nuclear data, we have developed a code system dedicatedfor deuteron-induced reactions, named DEURACS. In this paper, we present the results of theoreticalanalysis for (d,xn) reactions with DEURACS and discuss how important it is to consider the breakup
processes for accurate prediction of deuteron-induced reaction cross sections. Moreover, we have recently
developed deuteron nuclear database JENDL/DEU-2020 by employing DEURACS. The validation
results of JENDL/DEU-2020 are also presented.

1. Introduction
Since deuteron is a weakly bound system whose binding energy is 2.225 MeV, it easily breaks up
and emits a neutron through interaction with a target nucleus. Utilizing this property, intensive fastneutron sources using deuteron accelerators have been proposed for not only science and engineering
fields [1, 2] but also medical applications [3]. In the above-mentioned accelerator-based neutron sources,(d,xn) reactions on Li, Be, or C are employed to generate neutron beams. Thus, for design studies of suchneutron sources, accurate and comprehensive nuclear data of deuteron-induced reactions especially on Li,
Be, and C isotopes are indispensable.
Under these circumstances, we have developed a code system dedicated for deuteron-induced
reactions toward deuteron nuclear data evaluation. The code system was named DEURACS, and it wasso far successfully applied to analyses of production of nucleons [4, 5], composite particles up to A = 4[6, 7], and residual nuclei [8]. From these results, it is expected that DEURACS describes the mechanismof deuteron-induced reaction well and is suitable for completing deuteron nuclear data throughinterpolation and extrapolation of available experimental values. Thus, we have recently developed adeuteron nuclear database up to 200 MeV for 6,7Li, 9Be, and 12, 13C by employing DEURACS. The new
database was named JENDL/DEU-2020 [9] as one of the series of JENDL special-purpose files.
In this paper, we first present the brief overview of DEURACS and the results of analysis for theLi(d,xn) reactions as an example of the theoretical analysis with DEURACS. Through the analysis, we
discuss how important it is to consider the breakup processes of incident deuteron. Next, the outline of
JENDL/DEU-2020 is given and then the validation results of JENDL/DEU-2020 through comparison
with experimental data are presented.

2. Theoretical analysis of deuteron-induced reactions
2.1. Overview of DEURACS
DEURACS consists of several calculation codes based on theoretical models to describe each65
- 65 -

JAEA-Conf 2021-001

reaction process characteristic of deuteron-induced reactions. In the following, we briefly outline thetheoretical models and methods in DEURACS to calculate the double differential cross section (DDX)of (d,xn) reaction that is a fundamental quantity in terms of neutron production. More details about themodels and methods in DEURACS are described for (d,xn) reaction in Ref. [9] and for other reactions in
Refs. [6-8].
In DEURACS, the DDXs of (d,xn) reactions are expressed by incoherent summation of the following
components:݀ ଶ ߪሺௗǡ௫௡ሻ ݀ ଶ ߪ୉୆ ݀ ଶ ߪ୒୉୆ ݀ ଶ ߪ୔୉ାେ୒ൌ൅൅ǡሺͳሻ
݀‫݀ܧ‬ȳ
݀‫݀ܧ‬ȳ
݀‫݀ܧ‬ȳ
݀‫݀ܧ‬ȳ
where ݀ ଶ ߪ୉୆ Ȁሺ݀‫݀ܧ‬ȳሻ, ݀ ଶ ߪ୒୉୆ Ȁሺ݀‫݀ܧ‬ȳሻ, and ݀ ଶ ߪ୔୉ାେ୒ Ȁሺ݀‫݀ܧ‬ȳሻ correspond to the DDXs for elastic
breakup, nonelastic breakup, and pre-equilibrium and compound nucleus processes, respectively.
First, the elastic breakup component is directly calculated by the continuum-discretized coupled-channels (CDCC) method [10]. Next, the nonelastic breakup component is calculated by the Glaubermodel with the noneikonal approach described in Ref. [11]. In this approach, the eikonal S matrices usedin the Glauber model are replaced by the quantum S matrices given by the optical model calculations.
However, the Glauber model cannot properly calculate the (d,n) transfer reactions to the specific boundstates in the residual nucleus, which is a part of nonelastic breakup. To deal with this problem, we
separately calculate the transfer reaction by a conventional zero-range distorted wave Born approximation(DWBA) using the DWUCK4 code [12].
In addition to the breakup processes, the pre-equilibrium and the compound nucleus processes arecalculated using the two-component exciton model and the Hauser-Feshbach model implemented in the
CCONE code [13]. In deuteron-induced reactions, three types of composite nuclei can be formed by theabsorption of either neutron or proton in the incident deuteron or the incident deuteron itself. In
DEURACS, a calculation taking these effects into account is performed by combining the Glauber modeland the models in CCONE. Moreover, DEURACS was recently modified to take into account thecontribution of sequential particle decay from discrete levels in residual light nuclei [e.g., 9Be(Ex = 2.43
MeV)] and unstable ones (e.g., 5He) [9].
2.2. Theoretical analysis of (d,xn) reactions
To understand the relations among the reaction processes, we first perform a component -bycomponent analysis of DDXs of (d,xn) reactions. The results for the Li(d,xn) reactions at 40 MeV arepresented in Figure 1. The DDXs of the 7Li(d,xn) reactions calculated with DEURACS are decomposed
into three components as expressed in the right-hand side of Equation (1). To make the analysis clearer,
the target in the calculation is assumed to be 100% 7Li. In the figure, each component and the sum of thethree components are shown and compared with the experimental data [14]. Note that the experimental
data are those for natural lithium (92.5% 7Li and 7.5% 6Li). As presented in the figure, the sums of thethree components well reproduce both the shape and magnitude of the experimental data regardless ofthe emission angles.
The sharp peak observed around 50 MeV at 0ι is attributed to the (d,n) transfer reaction, which is apart of nonelastic breakup. The experimental small peak seen around 40 MeV at 0 ι is a contribution fromthe 6Li(d,n)7Be transfer reaction, which is not considered in the calculation presented in Figure 1. As forthe broad peaks seen around half the deuteron incident energy at forward angles, they are formed by thebreakup processes, namely, elastic and nonelastic breakup. The nonelastic breakup component is66- 66 -

JAEA-Conf 2021-001

dominant at 0 ι but it has a stronger angle dependence than the elastic breakup component, andconsequently the former is smaller than the latter at 30ι. This result demonstrates that it is necessary toconsider the two breakup components for the accurate prediction of the DDXs of the (d,xn) reaction at
various angles.

Figure 1. Calculated and experimental DDXs for the Li(d,xn) reactions at 40 MeV.
The number at the top of each plot denotes the emission angle.
The target in the calculation is 7Li but that in the experiment is natural lithium.
On the other hand, almost all of low-energy components below 10 MeV are due to the preequilibrium and compound nucleus processes. Especially at 90ι, the breakup components become verysmall and almost all spectra are explained by the contributions from the pre-equilibrium and compound
nucleus processes. This indicates that the calculation method taking into account the formation of three
types of composite nuclei and the particle decay from discrete levels works well.

3. Development of deuteron nuclear database
3.1. Outline of JENDL/DEU-2020
Based on the evaluation results employing DEURACS, we have developed JENDL/DEU-2020, thedeuteron nuclear database for 6,7Li, 9Be, and 12,13C at incident energies up to 200 MeV [9]. JENDL/DEU2020 is compiled according to the ENDF-6 format. In addition to the original ENDF-6 formatted files,
we have developed application libraries based on JENDL/DEU-2020 for use in the Monte Carlo transport
calculation codes such as MCNP [15] and PHITS [16]. An ACE format file is available in MCNP but thepresent version of PHITS (version 3.20) cannot treat the ACE file for deuteron. To deal with this problem,
we have developed ACE formatted files for MCNP and “Frag-Data” formatted ones for PHITS,
respectively. Frag-Data is the format uniquely defined in the PHITS code. The details about the two
application libraries are described in Ref. [9].
3.2. Validation results of JENDL/DEU-2020
As an example of the validation results of JENDL/DEU-2020, those for the DDXs of the (d,xn)
67- 67 -

JAEA-Conf 2021-001

reactions on natural lithium are illustrated in Figure 2. In the figure, the calculated and experimental
DDXs at 0ι are compared for the incident energies up to 200 MeV. Experimental data are taken from
Refs. [14, 17-19]. As for JENDL/DEU-2020, we obtained the DDXs from the MCNP calculation for athin lithium target using the ACE file of JENDL/DEU-2020. This is because the effect of deuteron energy
loss in the target is seen in the experimental data. The thickness of the target is set to be the same as thatused in each experiment. For comparison, we also present the calculation results with the models
implemented in the PHITS code. In the PHITS calculation, the approach combining the Intra-Nuclear
Cascade of Liège (INCL) [20] and DWBA proposed by Hashimoto et al. [21] is adopted. The values
stored in the deuteron sub-library of TENDL-2017 [22] are also plotted.

Figure 2. Calculated and experimental DDXs at 0ι for the natLi(d,xn) reactions.
Incident energies are 25, 40, 102, and 200 MeV.
As shown in the figure, the calculation results based on JENDL/DEU-2020 reproduce experimental
data better than the results with the models in PHITS and the values of TENDL-2017 in a wide range ofincident energies. As for the calculation with the models in PHITS, the magnitudes and positions of thebroad peaks around half the deuteron incident energies are different from the experimental ones especiallyin the low incident energies. On the other hand, TENDL-2017 underestimates the experimental values
considerably at all incident energies. This indicates that the empirical model by Kalbach [23] adopted in
TENDL to evaluate the breakup components does not work well for light target such as lithium.
To evaluate the results in Figure 2 more quantitatively, we calculate a relative deviation fromexperimental value by the following equation:σหߪ௜௘௫௣Ǥ െ  ߪ௜௖௔௟௖Ǥ หο‫ܧ‬௜‫ݏ‬ൌǡሺʹሻσ ߪ௜௘௫௣Ǥ ο‫ܧ‬௜௘௫௣Ǥ

is experimental DDX at i-th neutron energy point, ߪ௜௖௔௟௖Ǥ is calculated DDX at the energy
where ߪ௜௘௫௣Ǥ௘௫௣Ǥpoint corresponding to ߪ௜ , and ο‫ܧ‬௜ is energy bin of ߪ௜ . Figure 3 illustrates the deviations
obtained from the three calculations presented in Figure 2.
Since TENDL-2017 significantly underestimates the experimental DDXs, the deviations are almost
100% in each incident energy. As for the models in PHITS, the deviations become smaller as the incident
68- 68 -

JAEA-Conf 2021-001

energy increases. This is because the picture of the INC model becomes more appropriate as the incident
energy increases. The deviations obtained from JENDL/DEU-2020 are less than 15% for all incident
energies. In addition to that, we have confirmed that the prediction accuracy of JENDL/DEU-2020 forberyllium and carbon targets is as good as that for lithium target [9]. From these results, it is expectedthat neutron production data of JENDL/DEU-2020 are reliable and it makes a large contribution to design
studies of neutron sources with deuteron accelerator.

Figure 3. Relative deviations from experimental values defined by Equation (2)in terms of DDXs at 0ι for the natLi(d,xn) reactions.

4. Summary
We have presented the results of theoretical analysis for the Li(d,xn) reactions with DEURACS,
which is the code system dedicated for deuteron-induced reaction we have developed. From the analysis,
it has been shown that consideration of the breakup processes is essentially important for accurate
prediction of deuteron-induced reaction cross sections. Based on the evaluation results employing
DEURACS, we have developed JENDL/DEU-2020, the deuteron nuclear database for 6,7Li, 9Be, andC at incident energies up to 200 MeV. From the comparison with experimental data, it has been
demonstrated that the calculation results based on JENDL/DEU-2020 reproduces the measured neutron
12,13

production data well at incident energies from a few tens of MeV to 200 MeV. JENDL/DEU-2020 is
expected to make a large contribution to diverse design studies of deuteron accelerator neutron sources.
References







Ledoux X, Aiche M, Avrigeanu M, et al. The neutrons for science facility at SPIRAL-2 Nucl
Data Sheets 2014;119:353-356.
Moeslang A, Heinzel V, Matsui H, et al. The IFMIF test facilities design Fusion Eng Des
2006;81:863-871.
Nagai Y, Hashimoto K, Hatsukawa Y, et al. Generation of radioisotopes with accelerator
neutrons by deuterons J Phys Soc Jpn 2013;82:064201.
Nakayama S, Watanabe Y Systematic investigation of spectroscopic factors from (d,p)
reactions for deuteron nuclear data evaluation J Nucl Sci Technol 2016;53:89-101.
Nakayama S, Kouno H, Watanabe Y, et al. Theoretical model analysis of (d,xn) reactions on
9Be and 12C at incident energies up to 50 MeV Phys Rev C 2016;94:014618.
Nakayama S, Kouno H, Watanabe Y, et al. Development of a code system DEURACS for69- 69 -

JAEA-Conf 2021-001
























theoretical analysis and prediction of deuteron-induced reactions EPJ Web Conf
2017;146:12025.
Nakayama S, Iwamoto O, Watanabe Y Consistent description of light composite particle
emission in deuteron-induced reactions Phys Rev C 2019;100:044603.
Nakayama S, Furutachi N, Iwamoto O, et al. Role of breakup processes in deuteron-induced
spallation reactions at 100–200 MeV/nucleon Phys Rev C 2018;98:044606.
Nakayama S, Iwamoto. O, Watanabe Y, et al. JENDL/DEU-2020: deuteron nuclear data libraryfor design studies of accelerator-based neutron sources J Nucl Sci Technol 2021;DOI:
10.1080/00223131.2020.1870010.
Yahiro M, Ogata K, Matsumoto T, et al. The continuum discretized coupled-channels method
and its applications Prog Theor Exp Phys 2012;2012:01A206.
Ye T, Hashimoto S, Watanabe Y, et al. Analysis of inclusive (d,xp) reactions on nuclei from
9Be to 238U at 100 MeV Phys Rev C 2011;84:054606.
Kunz P, Rost E The distorted-wave Born approximation. In: Computational nuclear physics 2
Springer; 1993. p. 88-107.
Iwamoto O, Iwamoto N, Kunieda S, et al. The CCONE code system and its application to
nuclear data evaluation for fission and other reactions Nucl Data Sheets 2016;131:259-288.
Hagiwara M, Itoga T, Kawata N, et al. Measurement of neutron emission spectra in Li(d,xn)
reaction with thick and thin targets for 40-MeV deuterons Fusion Sci Technol
2005;48:1320-1328.
Goorley T, James M, Booth T, et al. Initial MCNP6 release overview Nucl Technol
2012;180:298-315.
Sato T, Iwamoto Y, Hashimoto S, et al. Features of particle and heavy ion transport code system(PHITS) version 3.02 J Nucl Sci Technol 2018;55:684-690.
Hagiwara M, Itoga T, Oishi T, et al. Experimental studies of neutron emission spectra inLi(d,xn) reactions for IFMIF J Nucl Mater 2011;417:1284-1287.
Araki S, Watanabe Y, Kitajima M, et al. Systematic measurement of double-differential neutron
production cross sections for deuteron-induced reactions at an incident energy of 102 MeV
Nucl Instrum Methods A 2017;842:62-70.
Watanabe Y, Sadamatsu H, Araki S, et al. Study of the Li(d,xn) reaction for the development
of accelerator-based neutron sources EPJ Web Conf 2020;239:20012.
Boudard A, Cugnon J, David JC, et al. New potentialities of the Liège intranuclear cascade
model for reactions induced by nucleons and light charged particles Phys Rev C
2013;87:014606.
Hashimoto S, Iwamoto Y, Sato T, et al. New approach to description of (d,xn) spectra at
energies below 50 MeV in Monte Carlo simulation by intra-nuclear cascade code with distortedwave Born approximation Nucl Instrum Methods B 2014;333:27-41.
Koning A, Rochman D, Sublet JC, et al. TENDL: complete nuclear data library for innovative
nuclear science and technology Nucl Data Sheets 2019;155:1-55.
Kalbach C Preequilibrium reactions with complex particle channels Phys Rev C
2005;71:034606.

Acknowledgements
The author is grateful to O. Iwamoto, Y. Watanabe, and K. Ogata for fruitful discussions. This work
was partially funded by JSPS KAKENHI Grant Number 19K15483.
70- 70 -

JAEA-Conf 2021-001

 Roles and Current Status on Reactor Physics Experiment in
Research Reactors

Cheol Ho PYEON
Institute for Integrated Radiation and Nuclear Science, Kyoto University
Asashiro-nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
Email: pyeon.cheolho.4z@kyoto-u.ac.jp

Nuclear reactors are mainly categorized as a commercial power reactor and a test and research
reactor for generating electric power and conducting research of radiation utilization, respectively. Main
roles of the test and research reactor are to conduct the research and development of nuclear engineeringand radiation detection fields with the use of radiation, including neutron and J-ray, and to contributeto the education of young generation. Another part of this paper is to contain the feasibility study on theaccelerator-driven system (ADS) conducted for nuclear transmutation analyses with the combined use of
the solid-moderated and solid-reflected core and the fixed-field alternating gradient accelerator, at the
Kyoto University Critical Assembly (KUCA). Through the experimental analyses, static and kinetic
parameters of reactor physics are interestingly revealed for nuclear transmutation of minor actinides(237Np and 241Am) and uncertainty quantification of a coolant material (lead and bismuth), with respect
to ADS. Additionally, experimental education programs for domestic and overseas students conducted at
KUCA are introduced in the paper.

1. Introduction
Nuclear reactors are mainly categorized as two parts: a commercial power reactor; a test andresearch reactor for generating electric power and conducting research of radiation utilization,
respectively. Of two reactors, main roles of the test and research reactor are to conduct the research anddevelopment of nuclear engineering and radiation detection fields with the use of radiation, including
neutron and J-ray, and to contribute to the education of young generation. Many research reactors
are importantly equipped with experimental facilities to research objectives, including irradiation holes,
neutron beams and spectrum shift changers, although the commercial reactors insufficiently meet theitems. An index of classification of research reactors is to provide a wide range of neutron spectrum andthermal reactor power, with the combined use of nuclear fuel, moderators, reflectors and coolantmaterials by varying the kinds, the geometries, the configurations and the utilization purposes.
The experimental studies on the accelerator-driven system (ADS) were conducted fornuclear transmutation analyses with the combined use of the Kyoto University Critical Assembly [1]-[3](KUCA; A-core: solid-moderated and -reflected core) and the fixed-field alternating gradient (FFAG) [4]accelerator. The ADS experiments with 100 MeV protons obtained from the FFAG accelerator had
been carried out to investigate the neutronic characteristics of ADS, and the static and kinetic parameters
were accurately analyzed
71- 71 -

JAEA-Conf 2021-001

through both the measurements and the Monte Carlo simulations of reactor physics parameters, including thereaction rates, the neutron spectrum, the neutron multiplication, the neutron decay constants and thesubcriticality. The neutronic characteristics of Pb-Bi are considered importantly and analyzed experimentallyfrom the viewpoint of reactor physics: neutron yield and neutron spectrum by the Pb-Bi target; uncertainties of
Pb-Bi cross sections in the core. Furthermore, irradiation experiments of the minor actinides (237Np and 241Am)
was conducted in hard spectrum core at KUCA to examine the feasibility of reaction rate analyses (237Np and
241Am fission and capture reactions) of nuclear transmutation. Finally, in this paper, the joint laboratory course
for students in the KUCA C-core was mentioned with a short history of the course and textbooks by multi
languages (Japanese, English and Korean).

2. Roles of Test and Research Reactors

Test and research reactors are designed for generating neutrons with a wide variety of energy, including
new type power reactors and critical assemblies in research and development phase. Basically, utilization targets
are focused on the research of nuclear science and engineering, the development of industrial application andtraining and education for young generation of students and engineers. Main role of test and research reactors
is to conduct the research and development of basic, industrial and educational utilizations by neutrons with awide variety of energy, and main objectives of these are categorized by several reactor components, including
the neutron energy, reactor power, nuclear fuel, moderator, reflector and coolant material. Domestic test andresearch reactors are listed as shown in Table 1.
Table 1 List of domestic test and research reactors
Reactor

Power

Fuel

Moderator

Coolant

Objective

JRR-3 (JAEA)NSRR (JAEA)
Joyo (JAEA)JMTR (JAEA)

20 MW
300 kW
140 MW
50 MW

U3Si2-Al
U-ZrH
U-Pu
U3Si2-Al

H2O
H2O
H2O

H2O
H2O
Liquid Na
H2O

HTTR (JAEA)

30 MW

UO2

GraphiteHe gasKUR (Kyoto U.)
UTR-KINKI(Kindai)

5 MW

U3Si2-Al

H2O

H2O

Beam utilization
Accident research
Fast reactor
Material test
R&D of High-temp.
reactorMulti purposes

1W

U-Al

H2O

-

Training and education

KUCA (Kyoto U.)

100 W

U-Al

H2O (Poly.)-

Basic research
reactor physics

3. Kyoto University Critical AssemblyofA critical assembly is a nuclear facility for conducting mock-up and benchmark experiments in the fieldof nuclear reactor physics field, such as KUCA shown in Figure 1. It is also one of the most effective facilities
for the education related to nuclear engineering and technology, especially that students and engineers grasp thebasic concepts of nuclear reactors by conducting experiments on and operating the reactor in person. Current
computation technology of reactor simulator systems for reactor operation has made rapid progress, and mostreactor operators at nuclear power stations have been trained through simulators, all of which contribute to safe
operation of reactors. It follows, therefore, that for the education of students majoring in nuclear engineering,72- 72 -

JAEA-Conf 2021-001

conducting experiments on actual reactors is a prerequisite to understanding the reactor itself. Furthermore,experiments on a critical assembly provide students and engineers valuable opportunities to appreciate safety
regulations related to reactor facilities and the handling of nuclear materials.

MEASUREMENTMEASUREMENTCONDITIONER PANELMEASUREMENT

Figure 1 Horizontal cross section of the KUCA (Ref. [1])3.1. Accelerator-Driven System
At KUCA, A and B are polyethylene-moderated and -reflected cores, and C is a light water-moderated
and -reflected one. The three cores are operated at a low mW power in the normal operating state, whereas the
maximum power is 100 W. The accelerator-driven system (ADS) experiments were carried out in the A-core(Figure 2) composed of the HEU fuel and polyethylene reflector rods, with the combined use of the FFAG
accelerator (high-energy proton accelerator; Figure 3) that has the main characteristics: 100 MeV energy, 0.1
nA intensity (at most), 20 Hz repetition rate, 100 ns pulsed width and 1.0×107 1/s neutron yield.

Figure 3 FFAG accelerator (Ref. [4])Figure 2 KUCA A-core (Ref. [1])To investigate the neutron characteristics of external neutron sources, ADS experiments with 100 MeV
protons was carried out by varying a heavy metal target at the location of target. As unique attempt, thecombination of materials tungsten (W) and beryllium (Be) was selected as plural targets for the aim foraccomplishment of the neutron spectrum in high-energy region and the neutron yield of high-energy neutrons
in the core. The combined use of the heavy- (W, Pb and Bi) and the light-nuclide (Be and lithium) was
considered useful for accomplishment of the research objectives relating the neutron spectrum and the neutron73- 73 -

JAEA-Conf 2021-001

yield. Here, the plural targets with the combined use of heavy- and light-nuclide were called “two-layer target”
in this study. From the numerical results (Figure 4) by MCNP calculations, the neutron spectrum was observedhigh in high-energy region with the combined use of W and Be. In the design of two-layer target, the proton
beams could be actually penetrated into Be target, and inversely stopped inside W target, and the dimensions of
two-layer target were determined to be in W (50 mm diameter and 9 mm thick) and Be (50 mm diameter and 6
mm thick). Also, the effects of specific target (two-layer target) were confirmed through the measured results

10-6

W

Normalized reaction rates [Arbitrary units]

Neutron flux per energy bin [1/cm2/eV/source]of 115In(n, J)116mIn reaction rate distributions in the core, as shown in Figure 5.
Pb-Bi

10-7

W-Be

10-8

W target
W-Be target

10-9

Pb-Bi target

10-10
10-2

10-1

100

101

102

40.0

Polyethylene
regionAir region

30.0Core region

W target
W-Be target
Pb-Bi target

20.0

10.0

0

0

10

20

30

40

50

60

70

Distance from location of original target [cm]

Neutron energy [MeV]

Figure 4 Neutron spectra of external neutron
sources by varying heavy metal target in ADS
experiments (Ref. [5])Figure 5Comparison between measured
reaction rate distributions in ADS experiments(Ref. [5])Furthermore, nuclear transmutation of 237Np and 241Am by ADS soundly implemented by combining the
subcritical core and the 100 MeV proton accelerator, and the use of a Pb-Bi target, was demonstrated throughthe experimental results of fission and capture reaction events, as shown in Figures 6 and 7, when irradiation
experiments were conducted in hard spectrum core at KUCA.
600

104
235

103

235

U

241

Am

237

U

102
241

101
100

1.0

1.5

Am

2.0

2.5

Np

500

Counts [Arbitrary units]

Counts [Arbitrary units]105

984.45 keV
1028.53 keV
4001025.87 keV

300

200

3.0

960

980

1000

1020

1040

Energy [keV]

Pulsed height [V]Figure 6 Measured pulsed-height signals of
241Am and 235U fission reaction events by the ADS
irradiation (Ref. [6])Figure 7 Measured J-ray spectrum of 237Np capture
reaction events by the ADS irradiation (Ref. [6])3.2 Training and Education Programs
74- 74 -

JAEA-Conf 2021-001

The joint reactor-laboratory course [1]-[3] for Japanese and overseas students at KUCA was launched in 1975
and various experiments on reactor physics have been conducted since: approach to criticality, control rod
calibration, measurement of neutron flux and power calibration, subcriticality measurements by the Feynman-D
and the pulsed neutron methods, and instruction in reactor operation. These experiments were conducted in the
KUCA C-core, which is a water-moderated- and -reflected-core with a plate-type fuel consisted of U-Al alloy.
Until fiscal year 2019, over three thousand and six hundred undergraduate and graduate students all over Japanattended this course. The same course for Korean undergraduate students in the Kyoto University Critical
Assembly (KUGSiKUCA) program was launched from 2003 to 2009 and founded by the Korean government. In
addition to the Swedish students ranging between 2007 and 2009, the Reactor Physics Asia Experiment Program(RPHA-XP) was launched newly in 2012 for graduate students in Korea and China. From 2003 to 2019, a totalof three hundred foreign students in overseas, including Korea, Sweden and China, took part in this program.
For the foreign students, in April 2010, Kyoto University Press published a textbook in English [2], which
was transcribed from the Japanese course work [1] comprising lectures, experiments, discussions and reports that
had been prepared from English textbooks on nuclear reactor physics, as shown in Figure 8. Preceding thatpublication, a textbook translated into Korean [3] was published in Korea on March 2010.

Figure 8 Textbooks by multi languages (Japanese, English and Korean) of the joint reactor-laboratory course
conducted at KUCA

4. Summary

Main role and objectives of test and research reactors were described in this paper, indicating the kind,reactor power and core components in domestic. Also, another part with respect to the critical assembly as oneof test and research reactors was contained, such as the ADS experiments with 100 MeV protons carried out
with the combined use of the KUCA A-core and the FFAG accelerator. In the ADS experiments, the effects of
two-layer target composed of W and Be were found apparently well on the neutron multiplication. Furthermore,
nuclear transmutation of 237Np and 241Am by ADS soundly implemented by combining the subcritical core andthe 100 MeV proton accelerator, and the use of a Pb-Bi target, was demonstrated through the experimental
results of fission and capture reaction events. Finally, as important utilization of the KUCA facility, the joint
reactor-laboratory course for Japanese and overseas students at KUCA launched in 1975 was introduced,
containing interestingly the experimental textbooks with the multi languages.
75- 75 -

JAEA-Conf 2021-001

References>@ Misawa T, Unesaki H and Pyeon CH, 1XFOHDU5HDFWRU3K\VLFV([SHULPHQWV, Kyoto University
Press,Kyoto, Japan 2010.
>@ Misawa T, Unesaki H and Pyeon CH, 1XFOHDU5HDFWRU3K\VLFV([SHULPHQWV, Kyoto University
Press,Kyoto, Japan 2010. [in Japanese]>@ Moon JH, Kim S, Kim GT and Pyeon CH, 1XFOHDU5HDFWRU3K\VLFV([SHULPHQWV, Dongguk
UniversityPress, Gyeongju, Korea 2010. [in Korean]>@ Lagrange JB, Planche T, Yamakawa E, et al. Straight scaling FFAG beam line. Nucl. Instrum
Methods A.2013; 691: 55-63.
>@ Pyeon CH, Nakano H, Yamanaka M, et al. Neutron characteristics of solid targets in acceleratordrivensystem with 100 MeV protons at Kyoto University Critical Assembly Nucl. Technol. 2015; 192:
181-190.
>@ Pyeon CH, Yamanaka M, Oizumi A, et al. First nuclear transmutation of 237Np and 241Am byaccelerator-driven system at Kyoto University Critical Assembly J. Nucl. Sci. Technol 2019; 56:
684-689.

76- 76 -

JAEA-Conf 2021-001

 Data-driven approaches in nuclear shell-model
calculations
Noritaka SHIMIZU†1 , Sota YOSHIDA2 , andTakahiro MIZUSAKI3
1

CenterforNuclearStudy,theUniversityofTokyo,Hongo,Bunkyo-ku,Tokyo113-0033,
Japan
2
Institute for Promotion of Higher Academic Education, Utsunomiya University,
Tochigi, Japan
3
Institute of Natural Sciences, Senshu University, 3-8-1 Kanda-Jinbocho, Chiyoda-ku,
Tokyo 101-8425, Japan†
Email: shimizu@cns.s.u-tokyo.ac.jp

We brieﬂy review some applications of machine learning and its related techniques tonuclear shell-model calculations. As an example, we quantiﬁed uncertainty caused by theparameters of the shell-model Hamiltonian utilizing Bayesian statistics. It enables us toquantify the uncertainty of the theoretical predictions and their agreement with experimental
data in a statistical manner. Moreover, we point out that a large deviation of the conﬁdence
interval for the energy in shell-model calculations from the corresponding experimental data
can be used as an indicator of some exotic property, e.g., alpha clustering. Besides, we
brieﬂy introduce a recent eﬀort to use the restricted Boltzmann machine to describe nuclear
shell-model wave functions.

1

Introduction

As computational power has been increasing recently, machine learning and its peripheral techniques are intensively developed in the prevalence of artiﬁcial-intelligence (AI) techniques. The
applications of these techniques are expected to accelerate the progress of natural science, including nuclear structure physics. Among the theoretical models in nuclear structure physics, nuclear
shell model calculation is one of the most powerful tools to investigate the ground and low-lying
excited states of nuclei, since it can describe any many-body correlations inside the valenceshell on equal footing by conﬁguration mixing. In this paper, we brieﬂy review two applicationsof these techniques to the shell-model calculations as follows. The uncertainty quantiﬁcation
utilizing the Bayesian statistics in shell-model calculations [1] is discussed in Sect. 2. The introduction of the restricted Boltzmann machine (RBM) to the Variational Monte Carlo (VMC)
formulation in shell-model calculations is discussed in Sect. 3. This paper is summarized andsome other applications are mentioned in Sect. 4.

2

Uncertainty quantiﬁcation by Bayesian analysis

2.1

Bayesian analysis

We here show the uncertainty quantiﬁcation of the shell-model study of p-shell nuclei by applying
the Bayesian analysis. In this study, we take the 0p3/2 and 0p1/2 single-particle orbits with 4 He
77
- 77 -

JAEA-Conf 2021-001

being an inert core. While the traditional shell-model Hamiltonian by S. Cohen and D. Kurath[2] is well-known for this model space, we construct the ensemble of the parameters of the
Hamiltonian to estimate the uncertainty.
We consider the probability distribution of the interaction parameters which reproduce theexperimental data with reasonable uncertainty. In the Bayesian analysis, it is described by
the posterior distribution, i.e., the conditional probability under the observation of data. This
posterior probability is obtained exploiting Bayes’ theorem,
P (θ|D) =P (D|θ)P (θ)∝ P (d|θ)P (θ).
P (D)

(1)

In this work, θ is a set of 17 parameters, which consist of the 2 single-particle energies and 15
two-body matrix elements and deﬁnes the shell-model Hamiltonian in the p-shell model space.
The D is a set of the physical observables, which are taken as 33 data of energies and excitationenergies in this work. In the present work, the likelihood function is taken as
P (D|θ) = exp[−χ2 (θ)/2](2)

with the squared errors,2
exptth [θ]
O
−
O
n
n
2
⎝
⎠ .
χ (θ) =
ΔO
n=1
ND
�

⎛

⎞

(3)

expt
where the On
and Onth denote the n-th experimental data and theoretical data, respectively.
The ND is the number of data and, in this case, we take ND = 33 binding and excitationenergies of the p-shell nuclei. ΔO denotes the typical error, 0.35 MeV, containing experimental
and theoretical ones although the experimental error is negligible for these energies.
For simplicity, the prior probability is taken as the uniform distribution, namely P (θ) ∝ 1.
In this case, the maximum a posteriori (MAP) estimation becomes with the minimization of theχ2 ﬁt. Note that the denominator in Eq.(1) is absorbed to the normalization factor and does
not need to be considered.
We generate sets of the Hamiltonian parameters θ whose frequency distribution obeys theprobability P (D|θ) to estimate the uncertainty of the theoretical results caused by the parameter ﬁtting. For that purpose, we adopted the Laplace approximation [1], since we found it
numerically diﬃcult to obtain the parameter sets using the Markov Chain Monte Carlo method
without this approximation.

2.2

Results

We prepared 50,000 samples of θ whose frequency distribution obeys the posterior probability,
Eq.(1), and performed shell-model calculations to estimate the uncertainty of the shell-model
results. Figures 1(a) and (b) show the excitation energies and energy expectation values andtheir uncertainties of the low-lying states of 12 C. In the ﬁgures, the violin plots with error bars
show the theoretical results and their uncertainties. The shell-model results well reproduce theexperimental values, which means that the experimental values are inside the 1σ uncertainty+
ranges except for the 0+
2 state. It indicates that the 02 state cannot be described by p-shell shellmodel calculation, which is reasonable since this state is known as three α-cluster state, or called
the Hoyle state and its structure is considered to be far from shell-model wave functions. The
result of the valence-shell in-medium similarity renormalization group (VS-IMSRG), in which
the eﬀective interaction is given in an ab initio way, is also shown for comparison.
78- 78 -

JAEA-Conf 2021-001

18

12

(a)

C

14
12
10
8
6
4
2

−72
(b)
−74 12
−76
−78
−80
−82
−84
Exp.
−86
LA samples (states in ﬁt)−88
LA samples (not in ﬁt)−90−92
IMSRG(500/400)
−94
CKtb1
−96
(0+ 0, 1) (2+ 0, 1) (0+ 0, 2) (1+ 0, 1) (4+ 0, 1) (1+ 1, 1) (2+ 1, 1)(J π T, NJT )C

16Energy (MeV)

Excitation energy (MeV)20(2+ 0, 1) (0+ 0, 2) (1+ 0, 1) (4+ 0, 1) (1+ 1, 1) (2+ 1, 1)(J π T, NJT )Figure 1: (a) Excitation energies and (b) energy expectation values of the ground and lowlying states of 12 C. The labels (J π , T, NJT ) denote the total angular-momentum and parity J π ,isospin T , and N -th lowest state of (J π , T ). The violin plots with error bars show the theoreticalvalues and their uncertainties. Red dotted lines, orange triangles, and blue triangles denote theexperimental values, the traditional shell-model results [2], and the VS-IMSRG results [3]. Taken
from Ref. [1].

3Variational Monte Carlo in nuclear shell-model calculations
and the restricted Boltzmann machine

In general, the shell-model calculation is diﬃcult to be applied to heavy-mass nuclei since thedimension of the Hamiltonian matrix often becomes too huge to be diagonalized. As an attempt
to solve this problem, we propose to introduce the Restricted Boltzmann Machine (RBM),
one of the artiﬁcial neural networks, to the Variational Monte Carlo (VMC) framework. The
introduction of the artiﬁcial neural network to solve quantum many-body problems was ﬁrstly
succeeded in condensed matter physics [4, 5].

3.1

Formulation

We start with the framework of the VMC in shell-model calculations [6]. The VMC trial wave
function with even A particles, |φ�, is deﬁned as�m|φ� = N (m)�m| fij c†i c†j

A/2

(4)

|−�

where i and j denote single-particle states, and fij is a set of variational parameters to describe
pair correlation. |m� = c†m1 c†m2 · · · c†mA |−� is the M -scheme conﬁguration [6, 7] speciﬁed by the
A-particle occupation of the single-particle states m = (m1 , m2 , · · · mA ).






 

  




 







 



Figure 2: Schematic view of the restricted Boltzmann machine.
79- 79 -

JAEA-Conf 2021-001

The N (m) is given by the RBM and deﬁned as [5]⎛�

N (m) =
=

⎞
�

exp ⎝

a i ni +{hk =±1}i��

2 cosh(bk +k�

wik ni hk +�i,kwik ni ) exp(ibk hk ⎠k

�a i ni )(5)

iwhere ai , bk , and wik denote the bias of visible nodes, the bias of hidden nodes, and weights
between the visible node i and the hidden node k, respectively. ni = 1 for the occupied states(nma = 1 for a = 1, 2, ..., A) and ni = 0 for the unoccupied states. The schematic view of the
RBM is shown in Fig. 2. Note that the weights of the RBM are restricted only between thevisible and hidden nodes, from which the second line of Eq.(5) is deduced.
The energy expectation values of this trial wave function is evaluated statistically by�ψ|H|ψ�
�ψ|ψ�

=

�

�
�
1
2 �m|H|ψ�|�m|ψ�|p(m)El (m),
=
2
�m|ψ�
m |�m|ψ�| mm(6)

where the local energy is deﬁned as El (m) = �m|H|ψ�/�m|ψ�. The summation m p(m) in
Eq. (6) is computed statistically by preparing a set of the M -scheme conﬁgurations |m� whose
frequency distribution obeys the probability p(m) ∝ |�m|ψ�|2 exploiting the Markov Chain
Monte Carlo method [6]. Thus, we avoid to store the whole possible |m�, the number of which
may be too huge. The variational parameters, fij , ai , bk and wik are determined to minimize theenergy expectation value by the stochastic reconﬁguration method [8], which can be considered
as one of the machine-learning techniques.
�

3.2

Benchmark test



 

As a benchmark test, we performed the VMC calculation to evaluate the ground-state energyof 28 Si with the sd-shell model space and the USD interaction [9]. In this case, 24 visible nodes
are used to describe each occupation of the single-particle states in sd shell for the RBM.








             !" #Figure 3: Shell-model energies of the ground state of 28 Si obtained by the exact diagonalization,
the VMC results with the 80 RBM hidden nodes, 24 RBM hidden nodes, 12 RBM hidden nodes,
and the VMC result without the RBM.
80
- 80 -

JAEA-Conf 2021-001

Figure 3 shows the shell-model energies obtained by the VMC without the RBM, with theRBM 12 hidden nodes, the 24 hidden nodes, the 80 hidden nodes. The exact energy is also
shown in the left-hand side of Fig. 3. The statistical errors of the VMC are small enough andnot shown in the ﬁgure. While the VMC without the RBM shows 2.2-MeV deviation from theexact one, the introduction of the RBM factor ﬁlls this gap to some extent. As increasing thenumber of the RBM hidden nodes, the description power of the RBM is enhanced and the energy
approaches the exact value, although the 1-MeV gap remains even with the 80 hidden nodes.
Further study is expected to ﬁll this gap by applying the angular-momentum projection [6].

4Summary and perspectives

We brieﬂy reviewed some applications of the machine-learning techniques to nuclear shell-model
calculations. Bayesian analysis was applied to the shell-model calculations and we demonstrated
that uncertainty quantiﬁcation is feasible with p-shell nuclei as an example. The statisticalanalysis of the sd-shell nuclei is found in Ref. [10]. As another application, we introduced theRBM to the VMC approach in the framework of the shell-model calculations and performed
the benchmark test, which shows promising features to overcome the numerical diﬃculty inshell-model calculations.
Many more promising attempts have been done to apply the AI-related methods to shellmodel calculations, which cannot be described in this paper. For example, we exploit a clustering
algorithm to divide the basis states of the no-core Monte Carlo shell model [11] into a small
number of groups in order to discuss the α-clustering structure of 12 C. Besides, Gaussian Process
and artiﬁcial neural network are exploited to the extrapolation of the energy eigenvalue to inﬁnite
model space in the no-core shell model approach [12, 13]. We expect that such AI-related
approaches will drastically open the frontiers of nuclear structure physics.

Acknowledgment
Numerical calculations were performed on Oakforest-PACS supercomputer (hp200130, hp190160,
hp180179, hp170230, hp160146, xg18i035) and CX400 supercomputer of Nagoya University(hp160146). NS acknowledge valuable supports by “Priority Issue on post-K computer” (Elucidation of the Fundamental Laws and Evolution of the Universe) and “Program for Promoting
Researches on the Supercomputer Fugaku” (Simulation for basic science: from fundamental lawsof particles to creation of nuclei), MEXT, Japan.
NS and SY acknowledge T. Togashi and T. Otsuka for our collaboration about the uncertainty quantiﬁcation of shell-model studies.

References[1] S. Yoshida, N. Shimizu, T. Togashi, and T. Otsuka, Phys. Rev. C 98, 061301(R) (2018).
[2] S. Cohen and D. Kurath, Nucl. Phys. 73, 1 (1965).
[3] S. R. Stroberg, A. Calci, H. Hergert, J. D. Holt, S. K. Bogner, R. Roth, and A. Schwenk,
Phys. Rev. Lett. 118, 032502 (2017).
[4] G. Carleo and M. Troyer, Science 355, 602 (2017)[5] Y. Nomura, A. S. Darmawan, Y. Yamaji, and M. Imada, Phys. Rev. B 96, 205152 (2017);
L. Huang, and L. Wang, Phys. Rev. B 95, 035105 (2017); G. Carleo, Y. Nomura, and M.
Imada, Nat. Comm. 9, 5322 (2018).
81- 81 -

JAEA-Conf 2021-001[6] T. Mizusaki and N. Shimizu, Phys. Rev. C 85, 021301(R) (2012); N. Shimizu and T.
Mizusaki, Phys. Rev. C 98, 054309 (2018).
[7] N. Shimizu, T. Mizusaki, Y. Utsuno, and Y. Tsunoda, Comp. Phys. Comm. 244, 372(2019).
[8] S. Sorella, Phys. Rev. B 64, 024512 (2001).
[9] B. A. Brown and B. H. Wildenthal, Ann. Rev. Nucl. Part. Sci. 38, 29 (1988).
[10] J. M. R. Fox, C. Johnson, and R. N. Perez, Phys. Rev. C 101, 054308 (2020).
[11] T. Yoshida, N. Shimizu, T. Abe and T. Otsuka, J. Phys.: Conf. Ser. 569, 012063 (2014).
[12] S. Yoshida, Phys. Rev. C 102, 024305 (2020)[13] W. G. Jiang, G. Hagen, and T. Papenbrock, Phys. Rev. C 100, 054326 (2019) G. A. Negoita
et al., Phys. Rev. C 99, 054308 (2019).

82- 82 -

JAEA-Conf 2021-001

 Nuclear data generation using machine learning
HirokiIWAMOTO†1
1

NuclearScience andEngineeringCenter,JapanAtomicEnergy Agency†
Email: iwamoto.hiroki@jaea.go.jp

Gaussian processes are used as a Bayesian machine learning technique to solve regressionand classiﬁcation problems. This paper reviews this technique, and presents some merits andissues for the nuclear data generation.

1 Introduction
Gaussian processes [1, 2] are used as a Bayesian machine learning technique to solve the regression and classiﬁcation problems. Because a regression model based on Gaussian processes(GPR) gives predictive distributions for regression problems, this technique may be a powerfultoolnotonlyforevaluatingnucleardatabutalsofordeterminingthecorrespondinguncertainty.
Inthepreviousstudy,amethodtogeneratenucleardatafromexperimentaldatawasproposed
basedonGPR[3],anditwasdemonstratedthatourmethodcangeneratereasonableregression
curves and their uncertainties from experimental data. This paper reviews this technique, andsome merits and issues for the nuclear data generation are presented.

2 Gaussian process regression
Suppose that we have N measured data points (measurement energy points xN ∈ RN and
corresponding cross sections with uncertainties [one standard deviation, 1σ], tN ±δtN ∈ RN)
for a certain nuclear reaction and that we aim to generate a set of cross-sections for certain M
energy points xM ∈ RM. GPR expresses the conditional probability distribution of tM ∈ RM
given by tN, p(tM|tN), as a Gaussian distribution with mean μM and covariance ΣM,M:p(tM |tN ) = N (tM | μM , ΣM,M ),(1)−1
μ M = C�N M C N N tN ,(2)

−1
Σ M M = CM M − C �
N M CN N CN M .

(3)

The (i, j)-th element of the covariance CN N is expressed as
C(xi , xj ) = k(xi , xj ) + δti δij δtj ,(4)where k(xi , xj ) represents the kernel function, and the δij is the Kronecker delta. The (i, j)-thelements of N × M matrix CN M , M × N matrix CM N (= C�N M ), and M × M matrix CM M areof the form:C(xi,xj)=k(xi,xj).
(5)83- 83 -

JAEA-Conf 2021-001

For the kernel function, this study used the following radial basis function:θ22k(xi , xj ) = θ1 exp − ||xi − xj || ,2

(6)

where Θ = (θ1 , θ2 ) is a set of hyperparameters, which is optimized by ﬁnding a solution thatmaximizes the marginal log likelihood p(tN |CN N , Θ):Θopt = argmax ln p(tN |CN N , Θ)
Θ


1
1
N
−1 �
ln(2π) .
= argmax − ln |CN N | − tN CN N tN −
2
2
2
Θ

3

Generated cross-sections

3.1

Nuclide-production cross-sections

(7)
(8)

Figure 1 compares the generated nuclide production cross-sections for the 27 Al(p, X)4 He and
27 Al(p, X)10 Be reactions with physics models of INCL++/ABLA07 [4, 5] and INCL4.6/GEM [6,7] and evaluated nuclear data libraries of ENDF/B-VIII.0 [8], JENDL-4.0/HE [9], and TENDL2019 [10]. The experimental data, which were measured with the activation method, were takenfrom the experimental nuclear database, EXFOR [11]. The blue dashed line with uncertainty
band indicates the cross-sections generated by GPR. Although the physics models and evaluatednuclear data account for the trends of the production cross-sections as a function of incident
energy, it fails to agree with the experimental data. These discrepancies would be solved by
improving the phyicis model or model parameters. In contrast, since GPR draws smooth curves
to ﬁt the experimental data without the need for physics models, the curves agree in principlewith the experiments.

Figure 1: Comparisons of nuclide production cross-sections for the 27 Al(p, X)4 He reaction (left panel) and the 27 Al(p, X)10 Be reaction (right panel) with physics models of
INCL++/ABLA07 [4, 5] and INCL4.6/GEM [6, 7] and evaluated nuclear data libraries of
ENDF/B-VIII.0 [8], JENDL-4.0/HE [9], and TENDL-2019 [10]. The dashed blue line andthe light blue band present the mean of the generated predictive distribution and ±2σ about
the mean, respectively. The experimental data were taken from EXFOR [11].

84- 84 -

JAEA-Conf 2021-001

3.2

GPR as a random sampler

Figure 2 shows generated nuclide-production cross-section for the nat N(p, X)10 Be reaction andthe generated correlation matrix. In the left panel of Figure 2, the 10 colored lines indicate
random samples of the cross sections, which can be easily generated according tM |tN ∼ N (tM |μM , ΣM M ). These random samples would be of signiﬁcant beneﬁt to subsequent uncertainty
propagation analyses by the random sampling technique in research ﬁelds such as neutronics,
reactor physics, and shielding analyses.

Figure 2: Generated nuclide-production cross-section (left panel) and the generated correlation
matrix (right panel) for the nat N(p, X)10 Be reaction. For the left panel, the dashed blue line andthe light blue band present the mean of the generated predictive distribution and ±2σ about
the mean, respectively. The 10 colored lines present random samples generated according totM |tN ∼ N (tM | μM , ΣM M ). The experimental data were taken from EXFOR.

3.3

Case of small experimental dataset

Figure 3 illustrates the nuclide-production cross-section for the 27 Al(p, pn)26 Al reaction. In theleft panel, the cross-section was generated from the experimental data by Sisterson, et al. [12]and Schneider, et al. [13]. Here, since the threshold energy can be deduced from the mass of
the reaction system (xth = 11.3 MeV), it was considered as training data (i.e. {xth , tth , δtth } ={11.3 MeV, 10−3 mb, 10−4 mb}). Although its exact position including its uncertainty cannot be
determined, a reasonable curve in this energy range seems to be obtained, and we conﬁrmed thatthe generated uncertainty did not strongly depend on the additional training data. However,an unacceptably large uncertainty band is still observed at the GeV range, which is owing to
the lack of experimental data. Such uncertainty information would be useful for motivating toconduct new experiments in terms of enhancing the prediction acuracy.
As one possible way to resolve such problems, it may be necessary to give some physicalknowledge as training data. In this case, from the total proton-neutron cross-section systematics [14], the (p, pn) cross-sections in the GeV range is expected to be constant. In the rightpanel of Figure 3, auxiliary constant cross-section value points are added in the GeV range totake into account this knowledge. However, this ad hoc solution need to be improved in future.

85- 85 -

JAEA-Conf 2021-001

Figure 3: Left panel: nuclide production cross-section for the 27 Al(p, pn)26 Al reaction generated
from the experimental data. Right panel: same as the left panel but with the inclusion of
auxiliary points infered from the total proton-neutron cross-section systematics at the GeV
range.

4

Summary

We have applied the GPR technique to generate nuclear data, focusing on proton-induced nuclide
production cross-sections. Reasonable curves with corresponding uncertainties were obtained
and the results indicate that this approach is eﬀective for generating nuclear data.

References[1] Rasmussen, C.F., Williams, C.K.I., Gaussian process for machine learning, The MIT press,
Cambridge, 2006.
[2] Bishop, C.M., Pattern recognition and machine learning, Springer, New York, 2006.
[3] Iwamoto, H., Generation of nuclear data using Gaussian process regression, J. Nucl. Sci.
Technol., vol.57, no.8, 2020, pp.932–938.
[4] Leray, S., et al., Extension of the Liège Intra Nuclear Cascade model to light ion-induced
collisions for medical and space applications. J. Phys.: Conf. Series, vol.420, 2013, pp.
012065.
[5] Kelić, A., et al., ABLA07 – Towards a complete description of the decay channel of a
nuclear system from spontaneous ﬁssion to multifragmentation. INDC(NDS)-0530, IAEA,
2008, pp.181–221.
[6] Boudard, A., et al., New potentialities of the Liège intranuclear cascade model for reactions
induced by nucleons and light charged particles. Phys. Rev. C, 2013, 014606.
[7] Furihata, S., Statistical analysis of light fragment production from medium energy protoninduced reactions. Nucl. Instrum. Meth. B, vol.171, 2000, pp.251–258.
[8] Brown, D.A., ENDF/B-VIII.0: The 8th major release of the nuclear reaction data librarywith CIELO-project cross sections, new standards and thermal scattering data. Nucl. Data
Seets, vol.148, 2018, pp.1–142.

86- 86 -

JAEA-Conf 2021-001[9] Kunieda, S., et al., Overview of JENDL-4.0/HE and benchmark calculations. Proceedingsof the 2015 Symposium on Nuclear Data, Tokai-mura, 2015, JAEA-Conf 2016-004, 2016,
pp.44–46.
[10] Koning, A.J., et al., TENDL: Complete nuclear data library for innovative nuclear scienceand technology. Nucl. Data Sheets, vol.155, 2019, pp.1–55.
[11] Otuka, N., et al., Towards a more complete and accurate experimental nuclear reaction
data library (EXFOR): International collaboration between nuclear reaction data centres(NRDC). Nucl. Data Sheets, vol.120, 2014, pp.272–276.
[12] Sisterson, J.M., et al., Measuring excitation functions needed to interpret cosmogenic nuclide production in lunar rocks. Conf. on Appl. of Accel. in Res. and Ind., Denton, USA,1996, pp.811.
[13] Schneider, R.J., et al., Measurement of cross sections for aluminum-26 and sodium-24 induced by protons in aluminum. Nucl. Instrum. Meth. B, vol.29, 1987, pp.271–274.
[14] Cugnon, J., et al., Simple parametrization of cross-sections for nuclear transport studies up
to the GeV range Nucl. Instrum. Meth. B, vol.111, 1996, pp.215–220.

87- 87 -

JAEA-Conf 2021-001

 Exploration of automated data processing for mass production of
nuclear data at RIBF
Shoichiro KAWASE1,2
1 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University

6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
2
RIKEN Nishina Center for Accelerator-Based Science
Email: kawase@aees.kyushu-u.ac.jp
Since the secondary beam produced by the RIBF generally contains various nuclides, it is possible
to acquire data on non-rare events systematically. However, systematic nuclear data acquisition at RIBF
has not been realized due to the lack of data acquisition capability and workforce for data analysis. If datacalibration can be automated, the latter will be solved. For the automation of data calibration, advanced
statistical inference methods could be used. In this study, the Markov chain Monte Carlo method was
employed for a part of particle identification analysis in a secondary beam experiment, and the results
were comparable to those of the conventional analysis method.

1. Introduction
Data-intensive science has been proposed as the fourth paradigm of scientific research following
experimental, theoretical, and computational sciences. In data-intensive science, a large amount of data,obtained by advanced data acquisition and processing and simulation techniques, are aggregated , andstatistical inference is used to develop data-driven scientific research.
The RI beam experiment at RIBF1) has the advantage of developing such a data-intensive science.
The secondary beam used in RIBF generally contains many different nuclides. Therefore, in principle, it
is possible in an experiment at RIBF to obtain rare events that the experimental proposer aims for andsystematically obtain non-rare nuclear reaction data simultaneously. Such non-rare data may include
isotope production and elastic scattering cross sections. The systematic acquisition of such data and thedevelopment of scientific research based on the aggregated data is consistent with the direction of dataintensive science.
However, in practice, the data acquisition and data processing capacity of RIBF is limited in two
aspects: data acquisition systems and workforce. First, to measure rare events efficiently, data from non rare events are usually excluded from the acquisition at the trigger level. Also, data on common events
that cannot be excluded are rarely published because the data alone have little academic impact, despite
the effort required to analyze it. Even if a non-collaborator would like to analyze the data and extractsystematic features from them, it is not easy to actually analyze the data because of the need for detailed
information on the experimental conditions, such as the operating conditions of the detector and themagnetic field settings of the electromagnets, which vary from experiment to experiment.
The latter of these two limitations can be overcome by automating the data calibration. In order torealize the automation of data calibration in RIBF, modern statistical inference methods could be applied.
88- 88 -

JAEA-Conf 2021-001

In this report, an attempt to apply the Markov chain Monte Carlo method (MCMC) to the particle
identification analysis for secondary beams is introduced.

2. Data Analysis
At the BigRIPS particle separator2) at RIBF, secondary beam particles are identified on an event-byevent basis from time-of-flight (TOF), magnetic rigidity ( ‫ߩܤ‬ሻ , and energy loss ሺȟ‫ܧ‬ሻ information
obtained by using beamline detectors (the TOF-‫ߩܤ‬-ȟ‫ ܧ‬method)2). In this study, MCMC was applied tothe determination of ion-optical transfer matrix elements, which is the part of the ‫ ߩܤ‬analysis. The firstorder ion-optical transformation between two focal planes is given by‫ݔ‬௙ሺ‫ݔ‬ȁ‫ݔ‬ሻ ሺ‫ݔ‬ȁܽሻ ሺ‫ݔ‬ȁߜሻ ‫ݔ‬௜൭ܽ௙ ൱ ൌ ൭ሺܽȁ‫ݔ‬ሻ ሺܽȁܽሻ ሺܽȁߜሻ൱ ቆܽ௜ ቇ Ǥ
ߜ
ߜ
Ͳ
Ͳ
ͳ

ሺͳሻ

Here, ሺ‫ݔ‬௜ ǡ ܽ௜ ሻ and ሺ‫ݔ‬௙ ǡ ܽ௙ ሻ are the positions and angles in the horizontal plane at the initial and the final

focal planes, and ߜ is the deviation of ‫ ߩܤ‬from the central value ‫ߩܤ‬଴ and defined by the following
equation:ߜሺʹሻ൰ ‫ߩܤ‬଴ ǤͳͲͲThe coefficients ሺ‫ݔ‬ȁ‫ݔ‬ሻǡ ሺ‫ݔ‬ȁܽሻǡ ሺ‫ݔ‬ȁߜሻǡ ሺܽȁ‫ݔ‬ሻ , ሺܽȁܽሻ , and ሺܽȁߜሻ are referred to as first-order transfer
matrix elements. In the conventional method, first-order transfer matrix elements are determined by linear‫ ߩܤ‬ൌ ൬ͳ ൅ fitting procedure, and the effect of higher-order transfer matrix elements are adjusted by the empiricalmethod so as to improve the resolution of mass-to-charge ratio (‫ܣ‬Ȁܳ). On the other hand, the new method
using MCMC has the potential to determine higher-order transfer matrix elements directly frommeasurement data.
In this study, a dataset taken in the spallation reaction measurement on ଽଷ was used for the
analysis. In this dataset, beam particles distribute only in limited phase-space. At first, ‫ݔ‬ிହ and  ଷହ

Figure 1 Correlation between ࢞૞ and TOF and clustering result using GMM.
89

- 89 -

JAEA-Conf 2021-001

Figure 2 Correlation of ࢾ obtained using MCMC (vertical axis) and a conventional analysis
method (horizontal axis).

distributions were fitted with the Gaussian mixture model (GMM) implemented in scikit-learn3), an opensource machine learning library, and the events corresponding to ଽଷ was extracted. Figure 1 shows theclustering result using GMM. Then, the first-order matrix elements were estimated using MCMC with aprobabilistic programming language Stan4). Finally, ߜ’s for all events in the dataset were calculated using
the estimated matrix elements. Figure 2 shows the correlation of ߜ’s obtained using MCMC to thatobtained in a conventional analysis method.

3. Summary
An analysis method employing MCMC was applied to the ‫ ߩܤ‬analysis with a limited dataset, andsimilar results to the conventional analysis method were obtained. In the future, further development,such as the introduction of higher-order matrix elements and application to more general datasets, will bedone to achieve automated data calibration.

References
1)
2)

Yano, Y., The RIKEN RI Beam Factory Project: A status report, Nucl. Instrum. Meth. Phys.
Res. B, vol.261, 2007, pp.1009-1013.
Fukuda, N., Kubo, T., Ohnishi, T., Inabe, N., Takeda, H., Kameda, D., Suzuki, H., Identificationand separation of radioactive isotope beams by the BigRIPS separator at the RIKEN RI Beam

3)
4)

Factory, Nucl. Instrum. Meth. Phys. Res. B, vol.317, 2013, pp.323-332.
Pedregosa, F., et al, Scikit-learn: Machine Learning in Python, J. Mach. Learn. Res., vol.12,
2011, pp.2825-2830.
Stan Development Team, Stan Modeling Language Users Guide and Reference Manual, 2.25,
https://mc-stan.org

Acknowledgments
This work is supported in part by the Education and Research Support Program on Mathematicaland Data Science funded by Education and Research Center for Mathematical and Data Science, Kyushu
University.
90- 90 -

JAEA-Conf 2021-001

 StudyoftheﬁssionpathenergyofU-236using
microscopic mean-ﬁeld model
Kazuki FUJIO†1 , ShuichiroEBATA2 , Tsunenori INAKURA1 , and Satoshi CHIBA1
1

Tokyo Institute of Technology, Ookayama2-12-1, Meguro, Tokyo, 152-8850, Japan
2
Saitama University, Shimo-Okubo255, Sakura-ku, Saitama, 338-8570, Japan†
E-mail: fujio.k.aa@m.titech.ac.jp

Abstract
To study a ﬁssion path, we investigated the potential energy surface of U-236 with respect
to its quadrupole and octupole deformations, using the microscopic theoretical model with
Skyrme-type eﬀective interactions. We divided the potential energy surface into 7 terms toinvestigate their contributions to the ﬁssion barrier height. Although the height is decided
from the competition among the terms, we found the Coulomb term and a combination ofothers excluding the spin-orbit and pairing energy terms have a relatively small interaction
dependence. It indicates that the amplitudes of spin-orbit and pairing energy will aﬀect thebarrier height.

1

Introduction

Minor Actinides (MA) are produced through a sequence of neutron-capture, β-, and α-decays
in nuclear reactors. The MAs aﬀect the performance of nuclear reactors and the compositionof nuclei in the radioactive waste. Therefore, nuclear data such as the ﬁssion product yieldof MA is necessary for reactor technology and to deal with the radioactive waste eﬀectively.
However, the data is insuﬃcient and its uncertainty is large, due to the diﬃculty of experiments
using highly radioactive materials. A theoretical approach is one of the eﬀective techniques toprepare unmeasured data or to predict unmeasurable data. The macro-micro models [1, 2] thatconsist of the liquid drop model [3] and a quantum correction have been employed widely for theﬁssion study. The liquid drop model is employed to describe the bulk property of the nucleus,
and the quantum correction is introduced for the nuclear shell eﬀects. The parameters in themodel and correction are phenomenologically determined to reproduce the nuclear properties
well. Although the model works well to explain and reproduce the known data, its prediction
power might be small for unknown data. To supply and predict the data of MA or unmeasured,
we should have a more fundamental approach in which the empirical methods are excluded as
far as possible. Therefore we employ a microscopic mean-ﬁeld model that can describe nuclei
from the degree of freedom of nucleon to investigate the ﬁssion phenomena. Our model employs
the Skyrme eﬀective interaction [4], which has been developed to describe the basic nuclear
properties in the vicinity of ground states: nuclear binding energy, nuclear matter parameters,
radius, deformation, and shell structure. We should investigate carefully the applicability ofthese eﬀective interactions to be applied to nuclear ﬁssion because the nuclei become muchdeformed in the way to scission hence they are far from their ground states. In this study, we
calculate the potential energy surface (PES) of the U-236 assuming the compound nucleus ofn + U-235 reaction, and investigate the diﬀerence among the PES given by existing Skyrme
eﬀective interactions.
91- 91 -

JAEA-Conf 2021-001

2

MethodWe employ the Skyrme-Hartree-Fock+BCS model [5] and impose constraints on the nuclear
shape [6] of U-236. To describe any nuclear deformation in this work, the wave function isrepresented in the three-dimensional coordinate space. The three Skyrme eﬀective interactions(SkM∗ , SLy4, SkI3) are employed. The Skyrme eﬀective interaction is written with the delta
function of a space r, as follows:


1


v̂(i, j) = t0 (1 + x0 Pσ ) δ (r) + t1 (1 + x1 Pσ ) k2 δ (r) + δ (r) k 2 + t2 (1 + x2 Pσ ) k · δ (r) k21
α ri + r j
δ (r) + iW (σ i + σ j ) · k × δ (r) k ,+ t3 (1 + x3 Pσ ) ρ(1)62
where t0 , x0 , t1 , x1 , t2 , x2 , t3 , x3 , α, W are parameters, σ is the Pauli matrix, Pσ is the spin
→ −
−
→
←
−


exchange operator, k and k are relative momentums. The k (k ) is formed ( ∇ i − ∇ j )/2i (( ∇ i −←−∇ j )/2i) which acts on the right (left) side. These parameters are adjusted to reproduce nuclear
properties according to the protocol of each parameter set. The SkM∗ parameter set is toreproduce the ﬁssion barrier height of the Pu-240 [7], the SLy4 is designed to deduce the nucleon
matter properties [8], and the SkI3 is prepared to reproduce the single-particle states of Pb-208
which the relativistic mean-ﬁeld model deduces [9]. We can calculate the energy of a system fromthe expectation value of the Skyrme interaction by the many-body wave function. Normally,
Skyrme interaction is divided into the central force and spin-orbit force. However, it is divided
into the four forces because we want to investigate the behavior of each term in detail. The ﬁrst
term in Eq.(1) is named volume term which works as the attractive force, the second and thirdterms are reﬂected the nuclear surface properties due to including the diﬀerential operators. The
fourth term is named density-dependent term which works as a repulsive force. The last termmeans the spin-orbit force. The many-body wave function formed as BCS-type [10] is employedin which the single-particle states and the pairing correlation are determined self-consistently.
We calculate the PES of U-236 in which the ﬁssion reaction of U-235 induced a thermal neutron
is assumed. The constraints on nuclear shape are expressed with the radial direction r and thespherical harmonics Ylm . The quadrupole Q̂20 and octupole Q̂30 operators are applied to express
the elongation and mass asymmetry of the nucleus, respectively. Their forms are:
5 2
2Q̂20 = r Y20 =r (3 cos2 θ − 1),
16π

7 3
3
r (5 cos3 θ − 3 cos θ).
(2)
Q̂30 = r Y30 =16π
For the investigation of the ﬁssion path, the PES is calculated with these constraints. The
constraints are introduced to the Hamiltonian Ĥ, such as Lagrange multiplier:2Ĥ = Ĥ −λl0 Q̂l0 − Ql0 ,
(3)
l=2,3

where λl0 is the Lagrange multiplier and Ql0 is the expectation value �Q̂l0 � with the many-bodywave function. The procedure to calculate the PES is 1) to prepare the ground state, 2) toelongate the nucleus with using Q̂20 , and 3) to add the octupole moment using Q̂30 for the
expression of mass asymmetry.

3

Results and discussion

Figure 1 shows the PES with respect to Q20 and Q30 using SkI3 parameter set. The PES dE
can be calculated as the diﬀerence between the ground state energy EG.S. and the energy at the92- 92 -

JAEA-Conf 2021-001

Table 1: Calculation results for EG.S. , Binner , Bouter (Q30 = 0) and Bouter (Q30 �= 0) using
diﬀerent Skyrme interactions together with experimental values
SLy4
SkI3
exp.
Force
SkM∗
EG.S. (MeV)−1796.97 −1796.46 −1799.85 −1790.41
Binner (MeV)
8.4
10.4
8.7
4.9
13.1
18.1
14.2
Bouter (Q30 = 0) (MeV)
Bouter (Q30 �= 0) (MeV)
7.2
10.2
6.3
5.8
each point E(Q20 , Q30 ), and as follows;dE = E(Q20 , Q30 ) − EG.S. .

(4)

The dashed line shows the symmetry ﬁssion path corresponding to Q30 = 0, and the solid line
shows a path following a valley of the PES in Figure 1. Nucleon densities at some important
points are given in this ﬁgure, additionally, it is clear that the path written by the solid line iseasier to undergo ﬁssion than the dashed one. Figure 2 shows the results of dE along the two
ﬁssion paths. The dashed and the solid line are the same as in Figure 1. All of interactions havethe ground state, the 2nd minimum, the inner ﬁssion barrier Binner and the outer ﬁssion barrier
Bouter . The two-humped barrier structure can be seen for the three eﬀective interactions and themass asymmetric deformation allows the decreasing the Bouter . Our results and the experimental
data for EG.S. [12] and for the ﬁssion barrier heights are shown in Table 1. This result reveals
that our calculation overestimates the experimental data of the ﬁssion barrier height [11]. To
elucidate the reason for this overestimation, we investigate which terms contribute to and whichmanner to the ﬁssion barrier in the following. The total binding energy Etot of each interaction

Figure 1: The PES of SkI3 with respect to Q20 and Q30
can be divided into 7 terms which are Et0 , Et1,t2 , Et3 , Els , the kinetic energy Ekinetic , the93- 93 -

JAEA-Conf 2021-001

Figure 2: The ﬁssion path with respect to Q20
Coulomb energy ECoulomb , and the pairing energy Epair :Etot = Et0 + Et1,t2 + Et3 + Els + Ekinetic + ECoulomb + Epair= ESkyrme + Ekinetic + ECoulomb + Epair .

(5)

The Skyrme energy ESkyrme is composed of the volume energy Et0 , the surface energy Et1,t2 ,the density dependence energy Et3 , and the spin-orbit energy Els . It is diﬃcult to specify theircontributions to the ﬁssion barrier because they have a complicated competition. To extract the
major characterizing the barrier, we search a combination of the energy terms which have a smallinteraction-dependence, namely, the non-characteristic parts of the PES on all interactions.
Figure 3 shows the result of them. These energies is calculated as the same way of Eq.(4).
The solid line shows SkM∗ , the dashed one is SLy4 and the dotted one is SkI3. The left panel
represents the sum of Et0 + Et1,t2 + Et3 + Ekinetic . This summation increases with increasing
Q20 for the three eﬀective interactions. On the other hand, ECoulomb decreases with increasing
Q20 , because the Coulomb force is inversely proportional to the distance of the charge. There
are small interaction dependences on the sum of Et0 + Et1,t2 + Et3 + Ekinetic and ECoulomb ,
which indicates that the Els and Epair have a very important role to form the ﬁssion barrier.
The behavior of the Els and Epair are compared with the ﬁssion path in Figure 4. The upper
left (right) shows Els (Epair ) and the lower left shows the ﬁssion path. The solid (dotted) arrow
indicates a bump (valley) of the ﬁssion path. These results show that Els has in-phase and, Epair
has the out-of-phase with the ﬁssion path. The phase relationship between the spin-orbit force94- 94 -

JAEA-Conf 2021-001

Figure 3: The contributions for dE: (left) Et0 + Et1,t2 + Et3 + Ekinetic , and (right) ECoulomb
and the pairing correlation has been known for the previous nuclear structure study [13]. We
point out that there are small interaction dependences on the sum of Et0 + Et1,t2 + Et3 + Ekinetic
and ECoulomb . Therefore, the Els and Epair might have an important role to decide the ﬁssion
barrier height.

4

Conclusion

We investigate the PES of U-236 by the constraint Skyrme-Hartree-Fock+BCS with respect
to the quadrupole Q20 and octupole Q30 momentums. Our calculation reproduces the twohumped barrier structure on the ﬁssion path, shows also that the degree of freedom for themass asymmetry on ﬁssion products, namely, Q30 eﬀects, allows the decreasing the outer barrierheight. The calculated ﬁssion barriers overestimate the experimental data. In order to elucidate
the reason for the overestimation, the ﬁssion path is decomposed into 7 terms. The sum of
Et0 + Et1,t2 + Et3 + Ekinetic , and the ECoulomb have a small interaction-dependence. Thus, theEls and Epair might aﬀect the ﬁssion barrier height.

Acknowledgement
This work is supported by the Leading initiative for Excellent Young Researchers, MEXT,
Japan, and by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number
JP20K03943.

References[1] V. M. Strutinsky, Shell eﬀects in nuclear masses and deformation energies, Nucl. Phys.
A95, 1967, pp.420–442.
[2] V. M. Strutinsky, “Shells” in deformed nuclei, Nucl. Phys. A122, 1968, pp.1–33.
[3] N. Bohr and J. A. Wheeler, The Mechanism of Nuclear Fission, Phys. Rev. 56, 1939,
pp.426–450.
[4] D. Vautherin and D. M. Brink, Hartree-Fock Calculations with Skyrme’s Interaction. 1.
Spherical Nuclei, Phys. Rev. C5, 1972, pp.626-647.
[5] S. Ebata and T. Nakatsukasa, Octupole deformation in the nuclear chart based on the 3D
Skyrme HartreeFock plus BCS model, Phy. Scr. 92, 2017 pp.064005
95- 95 -

JAEA-Conf 2021-001

Figure 4: The behavior of the Els and Epair[6]G.ScampsandC.Simenel,Impactofpear-shapedﬁssionfragmentsonmass-asymmetricﬁssioninactinides,Nature.564,2018,382385.
[7]J.Barreletal.,TowardsabetterparametrisationofSkyrme-likeeﬀectiveforces:Acritical
study of the SkM force, Nucl. Phys. A386, 1982, 79-100.
[8] E. Chabanat et al., A Skyrme parametrization from subnuclear to neutron star densities
Part 2. Nuclei far from stabilities, Nucl. Phys. A635, 1998, 231-256.
[9] P.-G. Reinhard and H. Flocard, Nuclear eﬀective forces and isotope shifts, Nucl. Phys.
A584, 1995, 467-488.
[10] Bardeen et al., Theory of Superconductivity, Phys. Rev. 108, 1957, 1175-1204.
[11] T. Belgya et al., Handbook for Calculations of Nuclear Reaction Data RIPL-2,
     IAEA TECDOC-1506., 2006.
[12] AMDC-Atomic Mass Data Center -IAEA-NDShttps://www-nds.iaea.org/amdc/(accessed:2021
BDDFTTFE

-11-17).
[13] S. G. Nilsson and I. Ragnarsson, SHAPES AND SHELLS IN NUCLEAR STRUCTURE,
CAMBRIDGE UNIVERSITY PRESS, 1995.

96- 96 -

JAEA-Conf 2021-001

 Threeﬁssionmodesin258MdstudiedbyLangevinmodel
IshizakiShoma
Shoma Ishizaki †1 , Yoshihiro Aritomo1 , Mizuki Okubayashi1 , KatsuhisaNishio2 , and
KentarouHirose2
1

FacultyofScience andEngineering, KindaiUniversity Higashi-Osaka, Osaka577-8502,
Japan
2
Advanced Science Research Center, Japan Atomic Energy Agency Tokai, Ibaraki
319-1195, Japan†
Email: uthorium232@gmail.com

Abstract
Recently, ﬁssion-fragment mass properties of 258 Md was measured in JAEA. The data
indicates a mixture of ﬁssion modes. We tried to calculate the ﬁssion properties of 258 Md
using the Langevin model.

1

Introduction

It has been shown that ﬁssion has multiple modes, characterized by mass asymmetric ﬁssion
and mass symmetric ﬁssion [1-7]. In neutron-rich heavy element region, it is argued that several
ﬁssion modes coexist, with a signiﬁcant change of their yields in accordance with the numberof neutrons contained in the ﬁssionig nucleus. A typical example is found in the fermium
isotopes. The dominant mode transition is from the asymmetric splitting for 257 Fm to theshape symmetric one for 258 Fm [8]. This transitions was interpreted as due to the lowering of
the ﬁssion barrier for symmetric ﬁssion toward heavier mass isotopes. Its important to know
the potential energy surface structure and nuclear’s deformation process to understand ﬁssion
mechanism in neutron-rich heavy element region [9].
At the JAEA tandem facility, ﬁssion of an exited compound nucleus 258 Md was studied in
the reaction of 4 He+254 Es. Based on the systematics of the spontaneous ﬁssion [8], the nucleus
are located in the region where mass-symmetric ﬁssion dominates.
For the discussion of the experimental data, we made a calculation of ﬁssion using theLangevin model. For the later discussion, we deﬁne three types of ﬁssion paths (modes); massasymmetric ﬁssion (standard mode), symmetric ﬁssion with high total kinetic energy TKE(supershort), and symmetric ﬁssion with low TKE (superlong).

2

Framwork

We use the ﬂuctuation-dissipation model and employ the Langevin equations[10] to investigate the ﬁssion process. The nuclear shape is deﬁned by the two-center parametrization [11,12],
which has three deformation parameters, z0 , δ, and α to serve as collective coordinates: z0 is
the distance between two potential centers, α is a mass-asymmetry parameter deﬁned by (A1 A2 )/(A1 +A2 ) using fragment masses, A1 and A2 . The symbol δ denotes the deformation of the97- 97 -

JAEA-Conf 2021-001

fragments deﬁned as δ = 3(R� R⊥ )/(2R� +R⊥ ), where R� and R⊥ are the half length of the axesof an ellipse in the z0 and ρ directions of the cylindrical coordinate, respectively, as shown in
Figure 1 in Ref. [10].
We adopted the neck parameter ε=0.55 following the empirical relation in Ref. [9]. The
three collective coordinates are abbreviated as q, q = z,δ,α. For a given value of a temperatureof a system T , the potential energy is deﬁned as a sum of the liquid-drop (LD) part, a rotationalenergy and a microscopic (SH) part:2 l(l + 1)
+ VSH (q, T ),2I(q)VLD (q) = Es (q) + Ec (q),V (q, l, T ) = VLD (q) +0(q)Φ(T ),VSH (q, T ) = Eshell


aT 2

Φ(T ) = exp −

Ed

.

(1)
(2)
(3)
(4)

Here, VLD is the potential energy calculated with the ﬁnite-range liquid drop model, given
as a sum of the surface energy ES [12] and the Coulomb energy EC . VSH is the shell correctionenergy evaluated by the Strutinski method from the single-particle levels of the two-center shellmodel. The shell correction has a temperature dependence expressed by a factor Φ(T), in which
Ed is the shell damping energy chosen to be 20 MeV [13] and a is the level density parameter.
At the zero temperature (T = 0), the shell correction energy reduces to that of the two-center0
shell model values Eshell. The second term on the right-hand side of Eq. (1) is the rotationalenergy for an angular momentum l [10], with a moment of inertia at q, I(q).
The multidimensional Langevin equations [10] are given as
dqi  −1 
= m ij pi ,
dt


dpi
1 ∂  −1 ∂Vm jk pj pk − γij m−1 jk pk + gij Rj (t),
−
=−
dt
∂qi
2 ∂qi

(5)
(6)

where i ={z,δ,α} and pi = mij dqj /dt is a momentum conjugate to coordinate qi . The summation is performed over repeated indices. In the Langevin equation, mij and γij are theshape-dependent collective inertia and the friction tensors, respectively. The wall-and-window
one-body dissipation [14-16] is adopted for the friction tensor which can describe the pre-scission
neutron multiplicities and total kinetic energy of fragments simultaneously [17]. A hydrodynamical inertia tensor is adopted with the Werner-Wheeler approximation for the velocity ﬁeld [18].
The normalized random force Ri (t) is assumed to be that of white noise, i.e., Ri (t)=0 and(t)=2δij δ(t1 − t2 ). The strength of the random force gij is given by the Einstein relation
Ri (t)Rj
γij T = k gij gjk .

3

Results and discussion

Figure 1 shows the calculated results of the FFMDs and TKE distributions of 258 Md. FFMDs
show mass symmetric splitting. The peak of the TKE distribution is about 235 MeV. Fromfeatures, the supershort mode was dominant in the calculation results.
Figure 2 shows the evolution of each ﬁssion modes as a function of excitation energy of 258 Md(in this work, ﬁssion modes was deﬁned in the range of mass numbers and TKE in Table 1).
Here, the count as the vertical axis means the number of events in the Langevin calculation.
The calculation shows that the standard mode decreases with excitation energy. It is considered98- 98 -

JAEA-Conf 2021-001

Figure 1: Calculation result of FFMDs(left) and TKE distribution(right) at excitation energy
E ∗ = 18M eVthat this is because the shell structure responsible for mass-asymmetry decreases with excitationenergy.
Figure 3 shows the ﬁssion pathways of each mode in the z − δ plane. From the 1st local
minimum(around {z,δ}∼{0.0,0.2}) to the 2nd local minimum(around {z,δ}∼{1.0,0.2}), the threemodes behave very similarly. But it can be seen that the standard mode branches ﬁrst at z ≈ 1.3
and then the superlong mode branches at z ≈ 1.8.
Figure 4 shows the energy of the ﬁssioning nucleus at each shape plotted as a function ofz. In Figure 4, the saddle point is located at z ≈ 1.3 in the standard mode, z ≈ 1.8 in the
superlong mode, and z ≈ 2.0 in the supershort mode, so it was found that the branch point
shown in Figure 3 is located at the saddle point. In particular, the saddle point of superlong
mode is close to that of supershort mode, the trajectory is very similar up to the saddle pointof superlong mode.
Table 1: Mass and TKE region of each mode
mode
Mass
TKE
supershort 114Mass144
TKE>220MeV
superlong 114Mass144
TKE220MeV
standard 114>Mass,144<Mass TKE220MeV

4

Conclusion

In this work, the ﬁssion mode of 258 Md was studied by trajectory calculation using a Langevinequations. As a result, it was found that the investigated three modes bifurcate around the exit
point of the 2nd local minimum on potential energy surface. Also, since the saddle point ofsuperlong mode is close to that of supershort mode, the trajectory is very similar up to thesaddle point of superlong mode.

Acknowledgements
The Langevin calculations were performed using the cluster computer system (Kindai-VOSTOK)
which is supported by Research funds for External Fund Introduction by Kindai University.
99- 99 -

JAEA-Conf 2021-001

Figure 2: The counts of each mode as a function excitation energy E ∗Figure 2: The counts of each mode as a function excitation energy E ∗Figure 3: Each mode trajectory in z − δ planeon α = 3:0 potential
energysurfacein z − δ plane Figure 4: Each mode trajectory in z − V plane
FigureEach mode
trajectory
(The
white
square inenergy
the ﬁgureindicates the sec- Figure 4: Each mode trajectory in z − V planeonα=0 potential
surfaceondminimum
point)(The white square in the ﬁgure indicates the second minimum point)

References
References[1] E. K. Hulet, J. F. Wild, R. J. Dougan, R. W. Lougheed, J. H. Landrum, A. D. Dougan,
et al.,
Phys. Rev.
56,
(1986).
[2] E.
P.
A.
M.
Henderson,
R. J. R.
Dupzyk,
R. L. Hahn,
Schdel, K.
and[1]
K. Baisden,Hulet,
J.C.
F.Lett.,Wild,
R.313
J. Dougan,
W. Lougheed,
J. H.M.
Landrum,
A.Smmerer,
D. Dougan,
G.A.
R.Baisden,Bethune,C.
Phys.
Rev. C  40,R.
770
[2] P.
M. Henderson,J.(1989).
Dupzyk, R. L. Hahn, M. Schdel, K. Smmerer, and[3] V.
Calabretta,Itkis,
et al., Phys. Rev. C  60, 041304
G. Pokrovsky,
R. Bethune,L.
Phys.
Rev. C M.
 40,G.
770
(1989).
[4]E.K.Hulet,R.W.Lougheed,J.H.Landrum,J.F.Wild,D.C.Hoﬀman,J.Weber,and[3] V. Pokrovsky, L. Calabretta, M. G. Itkis, et al., Phys. Rev. C  60, 041304
[4]E.K.Hulet,R.W.Lougheed,J.H.Landrum,J.F.Wild,D.C.Hoﬀman,J.Weber,and    J. B. Wilhelmy, Phys. Rev. C  21, 966 (1980).
[5]
    J.F.Wild,J.vanAarle,W.Westmeier,R.Lougheed,E.K.Hulet,K.J.Moody,R.J.Dougan,J. B. Wilhelmy, Phys. Rev. C  21, 966 (1980).
Koop, R.E. Glaser, R. Brandt and P. Patzelt, Phys. Rev.C  41, 640 (1990).
[5] E.-A.
J.F.Wild,J.vanAarle,W.Westmeier,R.Lougheed,E.K.Hulet,K.J.Moody,R.J.Dougan,[6] S.
Cwiok
P. Rozmej,
A. Sobiczewski,
andP.
Z.Patzelt,
Patyk, Nucl.
A41,
491,
281
(1989).
E.-A.
Koop,
R.E. Glaser,
R. Brandt and
Phys.Phys.
Rev.C
640
(1990).
[7] S.
U.CwiokBrosa,P.
S.Rozmej,
Grossmann,
and A. Muller,Rep. Nucl. 197,167
(1990).
[6]
A. Sobiczewski,
andPhys.
Z. Patyk,
Phys.
A  491, 281 (1989).
[8] U.
D.C.
Hoﬀmanet al., Phys.
Rev.
21, 1980
(637)
[7]
Brosa,
S. Grossmann,
and
A.C,
Muller,Phys.
Rep.  197,167 (1990).
[9] D.C.
Y. Miyamoto[8]
Hoﬀmanet
etal.,
al.,Phys.
Phys.Rev.
Rev.C,
C,99,
21,051601(R)
1980
(637)(2019).
637 (1980).
[10]
and
M. Ohta,
Phys.
A  744, 3 (2004).
[9] Y. AritomoMiyamoto
et al.,Phys. Nucl.
Rev. C,99, 051601(R)
(2019).
[10] Y. Aritomo and M. Ohta, Nucl. Phys. A  744,
1003 (2004).
- 100
100

[5] J.F.Wild,J.vanAarle,W.Westmeier,R.Lougheed,E.K.Hulet,K.J.Moody,R.J.Dougan,
E.-A. Koop, R.E. Glaser, R. Brandt and P. Patzelt, Phys. Rev.C  41, 640 (1990).
[6] S. Cwiok P. Rozmej, A. Sobiczewski, and Z. Patyk, Nucl. Phys. A  491, 281 (1989).
[7] U. Brosa, S. Grossmann, and A. Muller,Phys.
Rep.  197,167 (1990).
JAEA-Conf
2021-001[8] D.C. Hoﬀman et al., Phys. Rev. C, 21, 1980 (637)[9] Y. Miyamoto et al., Phys. Rev. C, 99, 051601(R) (2019).
[10] Y. Aritomo and M. Ohta, Nucl. Phys. A  744, 3 (2004).
[11] K. Sato, A. Iwamoto, K. Harada, S. Yamaji,
and S. Yoshida, Z. Phys. A  288, 383 (1978).
100[12] H. J. Krappe, J. R. Nix, and A. J. Sierk, Phys. Rev. C  20, 992(1979).
[13] A. V. Ignatyuk, G. N. Smirenkin, and A. S. Tishin, Sov. J.Nucl. Phys.  21, 255 (1975).
[14] J. Blocki, Y. Boneh, J. R. Nix, J. Randrup, M. Robel, A. J. Sierk, and W. J. Swiatecki,
Ann. Phys.  113, 330 (1978).
[15] J. R. Nix and A. J. Sierk, Nucl. Phys. A  428, 161c (1984).
[16] H. Feldmeier, Rep. Prog. Phys.  50, 915 (1987).
[17] T.Wada,Y.Abe, and N. Carjen,Phys. Rev. Lett.  70, 3538 (1993).
[18] K. T. R. Davies, A. J. Sierk, and J. R. Nix, Phys. Rev. C 13, 2385 (1976).

- 101
101

JAEA-Conf 2021-001

 Theoriginofcorrelationbetweenmassandangleinquasi-ﬁssion
S. Amano† , Y. Aritomo, S. Ishizaki, M. Okubayashi, and S. Okugawa
Kindai University 3-4-1Kowakae, Higashi-Osaka, Osaka-hu 577-8502, Japan†

Email: amano shota@kindai.ac.jp

Mass-angle distribution (MAD) measurement of heavy and superheavy element fragmentation reactions is one of the powerful tools for investigating the mechanism of ﬁssion andfusion process. MAD shows a strong correlation between mass and angle when the quasiﬁssion event is dominant. It has characteristic that appears diagonal correlation as long as
the quasi-ﬁssion event is dominant. This diagonal correlation could not be reproduced inprevious our model before the introduction of the parameters.
In this study, we systematically evaluate the unknown model parameters contained in
our model and clarify those model parameters to reproduce the diagonal correlation thatappears in MAD. Using a dynamical model based on the ﬂuctuation dissipation theorem
that employs Langevin equations, we calculate MADs of two reaction systems 48 Ti+186 W
and 34 S+232 Th which are dominated by quasi-ﬁssion. We were able to clarify the eﬀects
of unknown model parameters on the MAD. In addition, we identiﬁed the values of model
parameters that can reproduce the correlation between mass and angle. As a result, it was
found that the balance of tangential friction and moment of inertia values is important forthe correlation between mass and angle.

1

Introduction

Currently, superheavy element synthesis is limited to the success of element Z = 118. The
production of new superheavy elements will foot in the 8th period of the periodic table, andwill provide insight into the existence of island of stability. In addition, neutron-rich nuclei
far from the valley of stability are important for understanding the r-process in astronomical
nuclear physics. The supernova explosion is one of the origins of the elements along with theevolution of the stars. During a supernova explosion, a large amount of new elements are
created and spread around. After those elements create the new star, the new star eventuallydie, leading to an explosion again. The elements in the universe and the solar system is createdthrough such an evolution cycle of stars and elements. Superheavy elements and neutron-richnuclei create in the process of that element synthesis scenario. Production of those nuclei are
signiﬁcant to elucidate element synthesis scenario but, extremely diﬃcult. In recent years, themethod using the nucleon transfer reaction for the synthesis of new superheavy elements andneutron-rich nuclei has been proposed [1, 2], but a quantitative prediction model has not been
established. The mechanism of the nucleon transfer reaction has been studied for many years
in many models, including semiclassical models such as GRAZING [3] and Langevin [1], andmicroscopic models such as time-depent Hartree-Fock (TDHF) [4]. In this study, we analyze
the relationship between mass and angle obtained by the nucleon transfer reaction. Mass-angle
102- 102 -

JAEA-Conf 2021-001

distribution (MAD) is the emission angle on the vertical axis and the mass ratio MR on theAhorizontal axis. MR is represented by MR = A1i=1,2+A2 . A1 and A2 represent the mass number of the
projectile-like fragment and the target-like fragment, respectively. When the projectile nucleus
collides with the target nucleus, the projectile nucleus receives nucleons from the target nucleus
while rubbing around the target nucleus, increases the mass number, and ﬁnally leaves fromthe target nucleus in a certain direction. There is a correlation between the number of nucleon
transferred (mass) and the emission angle, and the characteristic is depends on the projectile
nucleus and the target nucleus. By analyzing this correlation, we are trying to elucidate thefusion process. MAD shows a strong correlation between mass and angle when the quasi-ﬁssion
reaction is dominant [5]. This correlation could not be reproduced with the dynamical model
developed in the previous research. In this study, we evaluated MADs of the two reaction
systems 48 Ti + 186 W and 34 S + 232 Th dominated quasi-ﬁssion using a dynamical model. This
paper contain as follows Sec. 2 describes the details of the model framework. Sec. 3 discusses
the parameter dependence of MAD. The last section describes conclusion.

2

Framework

2.1

Potential energy surface

We adopt the dynamical model which similar to uniﬁed model [7]. First, the initial stage ofthe nucleon transfer reactions consists of two parts: (1) the system is placed in the groundstate of the projectile and target because the reaction proceeds is too fast for nucleons toreconﬁgure a single particle state (2) The part where the system relaxes to the ground stateof the entire composite system which changes the potential energy surface to an adiabatic one.
Therefore, we consider the time evolution of potential energy from the diabatic one Vdiab (q)to adiabatic one Vadiab (q). Here, q denotes a set of collective coordinates representing nuclear
deformation. The diabatic potential is calculated by a folding procedure using eﬀective nucleonnucleon interaction [6–8]. However, the adiabatic potential energy of the system is calculatedusing an extended two-center shell model [8]. Then, we connect the diabatic and the adiabatic
potentials with a time-dependent weighting function as follows:
V = Vdiab (q) f (t) + Vadiab (q) [1 − f (t)] ,tf (t) = exp − .
τ(1)Where t is the interaction time and f (t) is the weighting function included the relaxation
time τ . We use the relaxation time τ = 10−21 s proposed in [9–11]. We use the two-centerparameterization [12,13] as coordinates to represent nuclear deformation. To solve the dynamical
equation numerically and avoid the huge computation time, we strictly limited the number ofdegrees of freedom and employ three parameters as follows: z0 (distance between the centersof two potentials), δ (deformation of fragment), and α (mass asymmetry of colliding nuclei);
1 −A2 )
α = (A(A1 +A2 ) , where A1 and A2 not only stand for the mass numbers of the target and projectile,
respectively [6,14] but also are then used to indicate mass numbers of the two ﬁssion fragments.
As shown in Fig. 1 in Ref. [12], the parameter δ is deﬁned as δ = 3(a−b)(2a+b) , where a and b represent
the half length of the ellipse axes in the z0 and ρ directions, respectively. We assume thateach fragment has the same deformation as a ﬁrst step. In addition, we use scaling to savez0
computation time and use the coordinate z deﬁned as z = (RCN
B) , where RCN denotes the(3+δ).
radius of the spherical compound nucleus and the parameter B is deﬁned as B = (3−2δ)103- 103 -

JAEA-Conf 2021-001

2.2

Dynamical equations

We perform trajectory calculations of the time-dependent uniﬁed potential energy [6, 7, 14] byLangevin equation. We start trajectory calculations from a suﬃciently long distance between
both nuclei [14]. So, we use the model which takes into account the nucleon transfer for slightly
separated nuclei [6]. Process for the separated nucleon transfer use the procedure described inRefs. [6, 7]. When both nuclei has been changed the mononucleus state that window of thecontact nuclei is suﬃciently opened, the evolution process of the mass asymmetry parameter α
switches from the master equation to Langevin equation according to the procedure describedin Ref. [14]. We use the multidimensional Langevin equation [6, 14, 15] uniﬁed following: −1 
dqi
ij pj ,
dt = m −1 
 −1 dpi∂V1 ∂jk pj pk γ −ij mjk pk + gij Rj (t) ,dt = − ∂qi − 2 ∂qi mdθ�dt = μR R2 ,dϕ1
L1
dt = �1 ,dϕ2
L2
dt = �2 ,
L1
L2
�
−�
a1 − �
a2
μR R 2
1
2



dL1
∂V
dt = − ∂ϕ1 − γtana1 − a1 gtan Rtan (t) ,dL2∂Vdt = − ∂ϕ2 + γtana2 − a2 gtan Rtan (t) .

d�∂Vdt = − ∂θ − γtan



L1
L2
�
−�
a1 − �
a2
μR R 2
1
2

L1
L2
�
−�
a1 − �
a2
μR R 2
1
2

R + Rgtan Rtan (t) ,(2)

The collective coordinates qi represent z, δ, and α, the symbol pi denotes momentum conjugatedto qi , and V is the multidimensional potential energy. : The symbols θ and � indicates therelative orientation of nuclei and relative angular momentum respectively. ϕ1 and ϕ2 stand forthe rotation angles of the nuclei in the reaction plane (their moment of inertia and angular2)
momenta are �1,2 and L1,2 , respectively), a1,2 = R2 ± (R1 −R
is the distance from the center of2
the fragment to the middle point between the nuclear surfaces, and R1,2 is the nuclear radii. The
symbol R is distance between the nuclear centers. The total angular momentum L = � + L1 + L2
is preserved. The symbol μR is reduced mass, and γtan is the tangential friction force of thecolliding nuclei. Here, it is called sliding friction. The phenomenological nuclear friction forces
F for sliding friction using the Woods-Saxon
for separated nuclei are expressed in terms of γtanradial form factor described in Refs. [6, 7]. The sliding friction are described as γtan = γt0 F (ζ),


−1

F)
0
, ζ = (ξ−ρ
where the radial form factor F (ζ) = 1 + expζaF . γt denote the strength of thetangential friction, respectively. ρF ∼ 2 fm and aF ∼ 0.6 fm are the model parameters, and ξ isthe distance between the nuclear surfaces ξ = R − Rcontact , where Rcontact = R1 + R2 [6]. The
symbols separated by mij and γij stand for the shape-dependent collective inertia and friction
tensors elements, respectively. We adoped the hydrodynamic inertia tensor mij in WernerWheeler approximation for the velocity ﬁeld [24]. The normalized random force Ri (t) is assumed
to be white noise: �Ri (t)�=0 and �Ri (t1 )Rj (t2 )� = 2δij δ(t1 − t2). According to Einstein relation,the strength of the random force gij is given γij T = k gij gjk , where T is the temperature of thecompound nucleus calculated from the intrinstic energy of the composite system. The adiabatic
potential energy is deﬁned as
2

L(L+1)+ VSH (q, T ) ,Vadiab (q, L, T ) = VLD (q) + h̄ 2I(q)VLD (q) = ES (q) + EC (q) ,0
VSH (q, T ) = Eshell(q) Φ (T ) ,Φ (T ) = exp (−E ∗ Ed ) .
104- 104 -

(3)

JAEA-Conf 2021-001

Here, I (q) represents the moment of inertia of the rigid body with deformation q. The centrifugalenergy generated from the angular momentum L of the rigid body is also taken into account.
VLD and VSH are the potential energy of the ﬁnite range liquid drop model and the shellcorrection energy that takes into account temperature dependence, respectively. The symbol
0Eshellindicates the shell correction energy at T =0. The temperature dependence factor Φ (T )is explained in Ref. [14], where E ∗ indicates the excitation energy of the compound nucleus.
E ∗ is given E ∗ = aT 2 , where a is the level density parameter. The shell damping energy Ed isselected as 20 MeV. This value is given by Ignatyuk et al. [25]. The symbols ES and EC standfor generalized surface energy [26] and Coulomb energy, respectively.
In this study, the calculation MADs was performed by changing two parameters (γt0 andfina ). γt0 is the tangential friction correction factor, fina is shown the correction factor in the2
L(L+1). I (q) represents the moment of inertia of a rigid body.
form of h̄2I(q)fina

3

Results

Figure 1 shows the calculation MADs for 48 Ti+186 W at Ec.m. =187.87MeV and their dependence
on fina and γt0 parameters in the range of fina =1.5-5.0 and γt0 =0.5-10.

Figure 1: The calculation MADs for 48 Ti+186 W at Ec.m. =187.87MeV and their dependence onfina and γt0 parameters in the range of fina =1.5-5.0 and γt0 =0.5-10. The result of (a)(d)(g)(j),(b)(e)(h)(k) and (c)(f)(i)(l) adopt fina =1.5, and fina =3.0 and fina =5.0, respectively. (a)-(c),(d)-(f), (g)-(i) and (j)-(l) adopt γt0 =0.5, γt0 =1.0, γt0 =5.0 and γt0 =10, respectively.
For example, in Fig. 1(k), there is no correlation in MAD, which means that the emitted
nuclei are emitted in all directions of 360 degrees, which is characteristic of the dominant fusionﬁssion process. Moreover, it is considered that the situation of quasi-ﬁssion process is reproduce
because Fig. 1(a) has a correlation between angle and mass. Fig. 1(a) and 1(d) can reproduce
the characteristics of the experimental values [5] well. When fina was large, the two bodies
after contact tended to be diﬃcult to move. It was found that when γt0 is large, the correlation105- 105 -

JAEA-Conf 2021-001

between mass and angle is lost. It is considered that this is because the emission angle overs 2
and is fragments are emitted in all directions due to the dominant fusion-ﬁssion reaction.
Next, Figure 2 shows the calculation results of 34 S+232 Th MAD at Ec.m. =168.75MeV when
γt0 and fina are changed. For instance, in Fig. 2(j), there is no correlation between mass andangle to dominate fusion-ﬁssion. On the other hand, since Fig. 2(l) has a correlation between
angle and mass, it is considered that we reproduce the situation of quasi-ﬁssion process. Fig.
2(i) and 2(l) can reproduce the characteristics of the experimental values [5] well. The inﬂuencefor MAD does not change even if the moment of inertia for rigid body and the tangential frictionchange respectively. But, the correlation originated from quasi-ﬁssion between mass and angle
show when both γt0 and fina are large. This is unlike 48 Ti+186 W case.

Figure 2: The calculation MADs for 34 S+232 Th at Ec.m. =168.75MeV and their dependence onfina and γt0 parameters in the range of fina =1.5-5.0 and γt0 =0.5-10. The result of (a)(d)(g)(j),(b)(e)(h)(k) and (c)(f)(i)(l) adopt fina =1.5, and fina =3.0 and fina =5.0, respectively. (a)-(c),(d)-(f), (g)-(i) and (j)-(l) adopt γt0 =0.5, γt0 =1.0, γt0 =5.0 and γt0 =10, respectively.
In this study, it was found that the tangential friction and the moment of inertia for rigid bodythat can reproduce the correlation between mass and angle depends on the reaction system. In
the reaction system with a small mass asymmetry of the incident system such as 48 Ti+186 W, thecalculation result could reproduce the correlation originated quasi-ﬁssion like the experimental
values by the small value of the tangential friction and the moment of inertia for the rigid body.
On the other hand, the calculation result could reproduce the characteristic originate from quasiﬁssion when the value of the tangential friction and the moment of inertia for the rigid bodylarge in the reaction system that the initial mass asymmetry is large such as 34 S+232 Th. Fromthese results, it is considered that the value of the tangential friction and the moment of inertia
for reproducing the experimental value depend on the initial mass asymmetry.

106- 106 -

JAEA-Conf 2021-001

4Conclusion

It was found that the tangential friction and the moment of inertia for the rigid body are strongly
relate to the correlation which originates from quasi-ﬁssion in the heavy element region. It
was also found that the balance of these physical quantities shows the characteristic whether
quasi-ﬁssion is dominant or fusion-ﬁssion reaction is dominant. It was possible to reproduce
the characteristics of the experimental results which quasi-ﬁssion is dominant by changing the
unknown model parameters. We need to calculate systematically to specify what unkown model
parameters depend on. Furthermore, it is necessary to ﬁnd the correlation between the values ofthese unknown model parameters and other physical quantities to reduce unknown parameters.
In the future, we will investigate the dependence of tangential friction and the moment of inertia
for the rigid body on mass asymmetry.

References[1] A.V. Karpov and V.V. Saiko, Phys. Rev. C 96, 024618 (2017).
[2] V.I. Zagrebaev, et al., Phys. Rev. C 73, 122701 (2008).
[3] A. Winther, Phys. A 572, 191 (1994).
[4] S. Ayik, et al., Phys. Rev. C 96, 024611 (2017).
[5] R.du Riez, et al., Phys. Rev. C 88, 054618 (2013).
[6] V. Zagrebaev and W. Greiner, J. Phys. G 31, 7, 825 (2005).
[7] V. Zagrebaev and W. Greiner, J. Phys. G 34, 11, 2265 (2007).
[8] V.I. Zagrebaev, et al., Phys. Part. Nuclei 38, 469 (2007).
[9] G.F. Bertsch, Z. Phys. A 289, 103 (1978).
[10] W. Cassing and W. Nörenberg, Nucl. Phys. A 401, 467 (1983).
[11] A. Diaz-Torres, Phys. Rev. C 69, 021603 (2004).
[12] J. Maruhn and W. Greiner, Z. Phys 251, 431 (1972).
[13] K. Sato, A. Iwamoto, K. Harada, S. Yamaji and S. Yoshida, Z. Phys. A 288, 383 (1978).
[14] Y. Aritomo and M. Ohta, Nucl. Phys. A 744, 4 (2004)[15] Y. Aritomo, Phys. Rev. C 80, 064604 (2009)[16] J. Blocki, et al., Ann. Phys 113, 330 (1978).
[17] J.R. Nix and A.J. Sierk, Nucl. Phys. A 428, 161c (1984).
[18] J. Randrup and W.J. Swiatecki, Nucl. Phys. A 429, 105 (1984).
[19] H. Feldmeier, Rep. Prog. Phys 50, 915 (1987).
[20] N. Carjan, A.J. Sierk, and J.R. Nix, Nucl. Phys. A 452, 381 (1986).
[21] M. Carjan, et al., AIP Conference Proceeding No.250 (AIP, New York, 1992).
[22] T. Wada, Y. Abe and N. Carjan, Phys. Rev. Lett 70, 3538 (1993).
[23] T. Asano, T. Wada, M. Ohta, S. Yamaji and H. Nakahara, J. Nucl. Radio Sci 7, 7 (2006).
[24] K.T.R Davies, A.J. Sierk and J.R. Nix, Phys. Rev. C 13, 2385 (1976).
[25] A.N. Ignatyuk, G.N. Smirenkin and A.S. Tishin, Sov. J. Nucl. Phys 21, 255 (1975).
[26] H.J. Krappe, J.R. Nix and A.J. Sierk, Phys. Rev. C 20, 992 (1979).

Acknowledgments
The Langevin calculation were perfomed using the cluster computer system (Kindai-VOSTOK)
which is supported by JSPS KAKENHI Grant Number 20K04003.
107- 107 -

JAEA-Conf 2021-001

 Neutron emission during fission process by dynamical model
R.Yamasaki1, S.Tanaka1,3, Y.Aritomo1,2, K.Nishio3
1
Graduate School of Science and Engineering, Kindai University
2
Faculty of Science and Engineering, Kindai University
Higashi-Osaka, Osaka 577-8502, Japan
3

Advanced Science Research Center, Japan Atomic Energy Agency
Tokai, Ibaraki 319-1195, Japane-mail: ryoutayamasaki.dia0101@gmail.com

Through joint research by the Japan Atomic Energy Agency and Kindai University, it has revealed that theyield distribution of fission products (fission fragments) changes significantly depending on the neutrons
emitted from the compound nucleus. This multichance fission (MCF) effect is particularly important to treat
high energy fissions, such as transmutation of long lived minor actinide nucleus by fission using ADS. In thiswork, we have introduced the neutron evaporation during fission process in the Langevin model and aimed
to describe the entire reaction process in a unified manner. The calculated results also reproduced
experimental data of the fission-fragment mass distribution.

1. Introduction and Background
Since Japan’s energy self-sufficiency rate is as low as 8%, energy diversification is being
promoted at each electric power company, and it is expected that the nuclear power generation
will continue to play a part of power sources. Long lived minor actinides accumulated in areactor, is one of the important issues in the nuclear power generation. Therefore, a method oftransmuting the long lived minor actinides to short lived minor actinides using Acceleratordriven System (ADS) is considered as a feasible option. ADS applies a proton beam generated
by a proton accelerator to a spallation target such as lead and bismuth to generate spallation
neutrons. This spallation neutron is used to transmute the long lived minor actinides by fission
from highly excited states. From these things, it is important to understand fission from highly
excited states.
From the above, through joint research by the Japan Atomic Energy Agency (JAEA) andKindai University, it has become clear that fission fragment mass distributions (FFMDs) change
significantly depending on the neutrons emitted from the compound nucleus. In the so-called
multichance fission (MCF) concept, fission takes place after emitting several neutrons. Because108- 108 -

JAEA-Conf 2021-001

the emitted neutrons bring out excitation energy corresponding to neutron binding energy andits kinetic energy, this revives the shell structure of a nucleus responsible for mass-asymmetricfission, thus change the FFMDs. The effect of MCF is particularly important to treat high energy
fissions, such as fission process in ADS. Until now, the MCF calculation was performed by
combining a fission model calculation (Langevin equation) and a statistical model using a codesuch as GEF [1,2]. However, this method does not introduce neutron emission during the fission
process.
In the conventional method using the GEF code, only neutron emission from the compound
nucleus was considered as shown in Fig. 1. Therefore, in this work, we have introduced theneutron evaporation during fission process in the Langevin model as shown in Fig. 2. For this,a change of the potential energy in each neutron evaporation step is treated.

Figure 1 It is a diagram that considers only neutron emission from the compound nucleus, andis a diagram in which a fission path is projected on the potential energy surface.
The saddle points are marked by the symbol “+”.

Figure 2 It is a diagram that considers neutron emission in all the processes of fission, and is adiagram in which a fission path is projected on the potential energy surface.
The saddle points are marked by the symbol “+”.
109
- 109 -

JAEA-Conf 2021-001

2. Theory and Method
A simple neutron decay width Ȟ௡ based on detailed balance is adopted, and the Gilbert andCameron equation is used for the level density ߩ [3-5]. The Ȟ௡ and ߩ are given as
Ȟ௡௃ ൌ
‫כ‬

ா೑
ͳ
න ෍ ෍ ܶ௟ ሺߝሻߩ൫‫ܧ‬௙ െ ߝǡ ‫ ܫ‬ᇱ ൯݀ߝ‫כ‬ʹߨߩሺ‫ܧ‬஼ேǡ ‫ܬ‬ሻ ଴ᇲᇲߩሺܷ ǡ ‫ܬ‬ሻ ൌ

ξߨ

௟

௦

൫ʹξܷܽ ‫ כ‬൯ ൈሺ‫ ܬ‬൅ ͳΤʹሻଶ݁‫ ݌ݔ‬ቈെ቉ʹߪ ଶʹξʹߨߪ ଷʹ‫ ܬ‬൅ ͳ

ሺͳሻ

ሺʹሻ
ͳʹܽଵΤସ ܷ ‫ כ‬ହΤସ‫כ‬and ܷ ‫ כ‬are the excitation energy of the compound nucleus and the effective
where ‫ܧ‬஼ே
excitation energy of the compound nucleus, respectively. The effective excitation energy of the‫כ‬intermediate nucleus ‫ܧ‬௙ can be expressed by ‫ܧ‬௙ ൌ ‫ܧ‬஼ேെ ‫ܤ‬௡ െ ‫ܧ‬௞ ( ‫ܤ‬௡ : neutron binding
energy, ‫ܧ‬௞ : emitted neutron kinetic energy). ߪ is the spin cut-off parameter.
density parameter a is given asܽ ൌ ܽ଴ ൜ͳ ൅

The level‫ܧ‬௦௛௘௟௟
‫כ‬൫ͳ െ ݁ ି௥ா ൯ൠ ǡ‫ ݎ‬ൌ ‫ݎ‬଴ ‫ିܣ‬ଵΤଷ ሺ͵ሻ‫כ‬‫ܧ‬where ‫ܧ‬௦௛௘௟௟ is the shell correction energy at temperature of the compound nucleus T=0. In
the Langevin model adopted in this study, random number determines the ratio of theLangevin’s time step to the neutron decay width.
In this work, the three-dimensional two-center parametrization was adopted to describe

nuclear shape. z is the distance between two potential centers, ߜ is the deformation of thefragment, ߙ is the mass asymmetry of the two fragments. The advantage of this model is thatit can represent both the fusion and the fission with a relatively small number of parameters.

The two-center parametrization is described using two harmonic oscillators. ‫ݖ‬ଵ and ‫ݖ‬ଶ are
the distances from the origin of contact of the harmonic oscillator to the center of each harmonic
oscillator. The ‫ݖ‬଴ , ߜ and ߙ are given as‫ݖ‬଴ ൌ ȁ‫ݖ‬ଵ ȁ ൅ ȁ‫ݖ‬ଶ ȁሺͶሻ͵ሺܽ െ ܾሻሺͷሻʹܽ െ ܾ
‫ܣ‬ଵ െ ‫ܣ‬ଶȽ ൌሺ͸ሻ‫ܣ‬ଵ ൅ ‫ܣ‬ଶɁ ൌwhere ‫ܣ‬ଵ and ‫ܣ‬ଶ is the mass numbers of heavy and light fragments, and a and b are the half

length of the axes of an ellipse in the ‫ݖ‬଴ and ρ directions of the cylindrical coordinate,respectively. In order to shorten the calculation time of the computer when solving the equationof motion, we introduce z as‫ݖ‬଴‫ ݖ‬ൌ
ǡ‫ ܤ‬ൌ ሺ͵ ൅ ߜሻȀሺ͵ െ ʹߜሻሺ͹ሻܴ஼ே ‫ܤ‬where ܴ஼ே is the radius of the compound nucleus.
110- 110 -

JAEA-Conf 2021-001

In the two-center parametrization, the size of the connecting cross section (neck size) of eachfragment is described by the neck parameter ߝ. The ߝ is givens asߝሺ‫ܣ‬௖ ሻ ൌ ͲǤͲͳͲͲ͹‫ܣ‬௖ െ ͳǤͻͶሺͺሻ
where ‫ܣ‬௖ is the mass number of the compound nucleus [6].
In the fission process, the nuclear potential is described by the adiabatic potential ܸ௔ௗ௜௔௕ ሺ‫ݍ‬ሻ.
In this case, density of a nucleus is constant. The adiabatic potential is described by the sum of
the potential of the liquid drop model and the shell correction energy asܸ௔ௗ௜௔௕ ሺ‫ݍ‬ǡ ‫ܮ‬ǡ ܶሻ ൌ ܸ௅஽ ሺ‫ݍ‬ሻ ൅ଶα ‫ܮ‬ሺ‫ ܮ‬൅ ͳሻʹ‫ܫ‬ሺ‫ݍ‬ሻ൅ ܸௌு ሺ‫ݍ‬ǡ ܶሻሺͻሻܸ௅஽ ሺ‫ݍ‬ሻ ൌ ‫ܧ‬ௌ ሺ‫ݍ‬ሻ ൅ ‫ܧ‬஼ ሺ‫ݍ‬ሻሺͳͲሻܸௌு ሺ‫ݍ‬ǡ ܶሻ ൌ ‫ܧ‬௦௛௘௟௟ ሺ‫ݍ‬ሻȰሺܶሻ
ሺͳͳሻ
ଶ
ܽܶ
Ȱሺሻ ൌ  ቆെቇሺͳʹሻ‫ܧ‬ௗwhere I(q) is the inertial mass from a rigid body, and ܸ௅஽ is the potential of the liquid drop
model. The excitation energy can be expressed by ‫ כ ܧ‬ൌ ܽܶ ଶ (a: level density parameter). ܸௌுis shell correction energy considering temperature dependence. The shell damping energy ‫ܧ‬ௗof 20 MeV was used in this work. ‫ܧ‬ௌ and ‫ܧ‬஼ are the surface and coulomb energy, respectively.
At the high energy, the shell correction energy becomes extremely small, and the internal
structure of the nucleus disappears, resulting in mass symmetric fission.
In this work, the time evolution nuclear shape is described by the Langevin equation. The
Langevin equation is given as݀‫ݍ‬௜ൌ ሺ݉ିଵ ሻ௜௝ ‫݌‬௝  
ሺͳ͵ሻ
݀‫ݐ‬
߲ܸ ͳ ߲
݀‫݌‬௜ሺ݉ିଵ ሻ௜௞ ‫݌‬௝ ‫݌‬௞ െ ߛ௜௝ ሺ݉ିଵ ሻ௝௞ ‫݌‬௞ ൅ ݃௜௝ ܴ௝ ሺ‫ݐ‬ሻሺͳͶሻ
ൌെ
െ
݀‫ݐ‬
߲‫ݍ‬௜ ʹ ߲‫ݍ‬௜where ‫ݍ‬௜ = ሼ‫ݖ‬ǡ ߜǡ ߙሽ and ‫݌‬௜ is the conjugate momentum of ‫ݍ‬௜ . ݉௜௝ and ߛ௜௝ are the inertial

mass and the friction coefficient that depend on the shape of the nucleus, respectively, R is anormalized random variable according to the Gaussian distribution, and ݃௜௝ is the dimensionof the random force.

3. Result and Discussion

In this work, FFMDs of 236-238U, 238-240Np, and 240-242Pu are calculated in the initial excitationenergy range of ‫= כ ܧ‬15-55 MeV. Fig. 3 shows a comparison between the calculated results andthe experimental data measured at JAEA’s tandem accelerator [7-9]. From Fig. 3, the calculation
results when neutron emission was taken into consideration in the fission process showed thatthe mass asymmetric shape of FFMDs was maintained even at high excitation energies. The
111- 111 -

JAEA-Conf 2021-001

calculation results can reproduce the experimental data well.

Figure 3 Calculation results of FFMDs without (gray curves) and with (black curves) neutron
emission in the fission of 236-238U, 238-240Np, and 240-242Pu. Dependence on the
excitation energy of the initial compound nucleus (‫= כ ܧ‬15-55 MeV, see right handside of the figure) is shown. The calculation FFMDs are compared with theexperimental data (points with error bars) [7-9].
The average number of neutron emissions of 236-238U, 238-240Np, and 240-242Pu was calculated,
and the results are compared to the calculated neutron-emission before fission in the GEF code
[1,2]. Looking at the results in Table 1-3, our calculation agrees well with the GEF calculation
at high excitation energies. In addition, our calculation does not show any isotope dependence,in contrast to the GEF code, which exhibit a increasing trend of the neutron emission number
with the mass of isotope. In addition, at low excitation energies, the average number of neutron
emissions calculated by the present Langevin calculation is larger than the GEF result. In theconventional method, only the emission of the excitation energy of 15 MeV from the compound
nucleus shape was considered. In the model of this work, the initial value of excitation energyof 15 MeV changes from moment to moment, which may cause a difference. We need toinvestigate this difference in detail in the future.
Table 1 Average number of neutron emissionsof 236-238U [1,2]Table 2 Average number of neutron emissionsof 238-240Np [1,2]112- 112 -

JAEA-Conf 2021-001

Table 3 Average number of neutron emissionsof 240-242Pu [1,2]

4. Summary and Perspectives
We performed the fission calculation including neutron emission during fission process. The
calculated results reproduce well the experimental data of FFMDs. It was shown that themethod of this work can evaluate neutron emission during fission process. However, the change
in the number of neutron emission due to the mass number of the compound nucleus could not
be confirmed. We plan to improve the model. We will investigate the shape of the compound
nucleus when neutrons are emitted. Also we plan to calculate the fission probability as afunction of excitation energy to see if the step-like structure of the reaction cross-section
appears at the energy that multi-chance fission emerges.

ReferenceV[1] S. Tanaka, Y. Aritomo, Y. Miyamoto, et al., Phys. Rev. C 100, 064605 (2019).
[2] K.-H. Schmidt, B. Jurado, C. Amouroux, and C. Schmitt, Nucl. Data Sheets 131, 107(2016).
[3] A. Gilbert and A.G.W. Cameron, Can.J.Phys. 43, 269 (1965).
[4] V. Weisskopf, Phys. Rev. 52, 295 (1937).
[5] N. Bohr and J.A. Wheeler, Phys. Rev. 56, 426 (1939).
[6] Y. Miyamoto, Y. Aritomo, S. Tanaka, et al., Phys. Rev. C 99, 051601 (2019).
[7] R. Leguillon, K. Nishio, K. Hirose, et al., Phys. Lett. B 761, 125 (2016).
[8] K. Hirose, K. Nishio, S. Tanaka, et al., Phys. Rev. Lett. 119, 222501 (2017).
[9] M. Vermeulen, K. Nishio, K. Hirose, et al., Phys. Rev. C 102, 054610 (2020).

113- 113 -

JAEA-Conf 2021-001

 'JTTJPO GSBHNFOU EJTUSJCVUJPOT PG OFVUSPOSJDI
OVDMFJCBTFE PO -BOHFWJO DBMDVMBUJPOTSQSPDFTTOVDMFPTZOUIFTJT TJNVMBUJPOT.J[VLJ0,6#":"4)*∗ 4IPZB5"/","  :PTIJIJSP"3*50.0 
4IPNB*4)*;",* 4IPUB"."/0 BOE/PCVZB/*4)*.63"p (SBEVBUF4DIPPMPG4DJFODFBOE&OHJOFFSJOH3FTFBSDI ,JOEBJ6OJWFSTJUZ )JHBTIJ0TBLB +BQBO
"EWBODFE4DJFODF3FTFBSDI$FOUFS +"&" 5PLBJ +BQBO
"TUSPQIZTJDBM#JH#BOH-BCPSBUPSZ $13 3*,&/ 8BLP +BQBO%JWJTJPOPG
4DJFODF /"0+ .JUBLB 5PLZP+BQBO∗&NBJMNPLVCBZBTIJ!HNBJMDPNp&NBJM OPCVZBOJTIJNVSB!SJLFOKQ"CTUSBDU
The nuclear ﬁssion of very neuron-rich nuclei related the r-process are important for
the termination of nucleosynthesis ﬂows on the nuclear chart and the formation of ﬁnal
abundances. Nevertheless, most of available ﬁssion data for the r-process calculations are
based on the theory predictions, including phenomenological treatments. In this study, we
calculated a series of nuclear ﬁssion distribution for neutron-rich nuclei away from the βstability line. As most of these nuclei are experimentally unknown, we are based on theory
calculations based on the dynamical ﬁssion model with the Langevin method. We performed
ﬁssion distribution calculations for neutron-rich actinoid nuclei, which are important in the rprocess. In the present paper, we compared the obtained mass and charge distributions withexperimental data. We also show the results of the systematic behaviour of mass distribution
for neutron-rich U and Fm isotopes.

1

Introduction

Nucleosynthesis by the rapid-neutron-capture process, r-process, represents for cosmic origin of
the heaviest elements (e.g., gold and uranium) beyond the iron-group peak. Although several
astrophysical scenarios have been proposed, the mechanism of the r-process is not completely
understood (for a recent review, see [1, 2, 3]). One of main reasons is a large uncertainty in the
nuclear-physics properties of very neutron-rich nuclei, e.g., neutron captures rates and several
decay half-lives. To determine nucleosynthesis ﬂows on the r-process “path”, the β-decay andthe neutron capture (strongly depending on theoretical mass prediction) are signiﬁcant. The
nuclear ﬁssion is a key ingredient of the termination of and the ﬁnal abundance distribution if
r-processing is strong enough to reach actinoids.
Nuclear ﬁssion, therefore, plays an essential role under certain r-process conditions [4, 5, 6, 7],
in particular, in very neutron-rich environments, e.g., neutron star mergers. The nucleosynthesis
path goes into the very neutron-rich trans-uranium region. The eﬀects of ﬁssion are signiﬁcant
to shape the r-process abundances due to ﬁssion recycling, of which ﬁssion products become
seed nuclei (A < 200) for the next r-processing during a single nucleosynthesis process. Besides
114- 114 -

JAEA-Conf 2021-001

the abundance prediction, ﬁssion is also a key role as the heating source of kilonovae at latetimes (∼ 10 days to months) [8, 9], electromagnetic transients of neutron star mergers. A signof ﬁssion heating may have been observed in the light curve of the kilonova associated with thegravitational wave, GW170817. The precise understanding of ﬁssion becomes much crucial in
the era of gravitational astronomy.
In this study, we calculate the ﬁssion-fragment mass distributions of very neutron-rich nuclei.
Fission product distributions are important for the r-process, but experimental data are notavailable. We adopt the Langevin method [10, 11], widely adopted in the study of low-energy
ﬁssion. We found that the calculated ﬁssion mass distributions for uranium, of which the charge(Z) distribution is obtained by the UCD (unchanged charge distribution assumption), can well
reproduce experimental data in JENDL (232 U to 232 U). We also found that the ﬁssion fragment
distribution changes from the two peak feature (asymmetric ﬁssion) to the one-peak (symmetricﬁssion) with increasing the neutron number.
The present paper is structured as follows. In Section 2, we brieﬂy describe the basics of theLangevin calculations and the UCD assumption. The results of the mass and charge distribution
are shown in Section 3. Section 4 is dedicated to the conclusion.

2

Method

2.1

Dynamical ﬁssion calculations by the Langevin method

We calculate ﬁssion fragment distributions (FFD) following ﬁssion dynamics by solving theLangevin equations, based on the ﬂuctuation-dissipation model [11, 10]. In the ﬁssion calculations, deformation and ﬁssion processes are represented by the “motion” of trajectories on
the multi-dimensional deformation space. For the nuclear shape, we adopt the two-centre-shellmodel with three parameters (see, [11, 10] for the details), i.e., the distance of two nuclei (z0 ),the degree of deformation of a fragment (δ), and the mass asymmetry (α).
We calculate the dynamical process of ﬁssion by solving the multi-dimensional Langevinequations of motion, which are expressed as follows:dqi= (m−1 )ji Pj
dt

(1)

dpi
∂V
1 ∂
=−
−
(m−1 )jk Pj Pk − γij (m−1 )jk Pk + gij Rj (t) ,
dt
∂qi
2 ∂qi

(2)

where qi = {z, σ, α} and their momentum conjugate, pi = mij dqi /dt. V is the potential, andmij and γij are the inertia mass and friction coeﬃcient depending on the shape of the nucleus.
The last term of Eq. 2 corresponds to the random force with the normalized white noise
Rj (t). The gji is the strength of the random force, which is related with the friction tensor γji
by the classical Einstein relation,
gij gjk(3)
γji T =kwhere T is the temperature of the nucleus. Following this random property in the momentum
equation (Eq. 2), each event shows a diﬀerent trajectory on the potential energy space. We
repeat ﬁssion dynamics calculations to ﬁnd the convergence of ﬁssion distributions, e.g., the
FFD.

2.2

Charge distributions

Although the time evolution and the FFD are determined in our Langevin calculations, thecharge distribution of ﬁssion fragments cannot be obtained. However, the charge distribution
115- 115 -

JAEA-Conf 2021-001

Figure 1: (a) The calculated FFD on the N -Z plane for 236 U with the excitation energy: E ∗ =20MeV. (b) The experimental FFD (JENDL-4.0 [12]) for 235 U by the neutron-induced ﬁssion.
The N/Z line of compound nucleus (black), the N/Z = 50/82 line of a double-magic nucleus
132 Sn (blue), and the β-stability line (red) are plotted.
of ﬁssion products is a fundamental quantity for the determination of the production rate ofindividual isotopes. Thus, it is an essential nuclear data for the comparison of experiments
and r-process nucleosynthesis calculations. We calculate the charge distribution based on theassumption of unchanged charge distribution (UCD), where the charge distribution (charge
density) remains unchanged during the whole ﬁssion process, i.e., the charge density of thecompound nucleus is maintained.
Based on the UCD assumption, we can only calculate the charge (Z) distribution along to
the N/Z line, i.e., “projection” to the N/Z axis. For example, the calculated charge distributionof 236 U is shown in Fig. 1a. However, the distribution must be width on this line, as shown in
the experimental data (Fig. 1b) of the FFD for neutron-included ﬁssion of 236 U (the compound
nucleus is 236 U). Therefore, we adopt Gaussian distribution to calculated the width of FFD
with σ = 0.01, which is relatively well reproduce available experimental data in JENDL-4.0 [12].

3Results

In this section, we show the ﬁssion fragment mass and charge distributions for 236 U, of which
experimental data are available (Section 3.1). We see our ﬁssion model can reproduce experi-

12

24

8
6

Langevin Cal. ( 236U(E*=10MeV)

16
12

4

8

2

4

0

JENDL-4.0 ( 235U(nth, f) )20
Yield (%)

Yield (%)

10

28
JENDL-4.0 ( 235U(nth, f) )Langevin Cal. ( 236U(E*=10MeV)

020

60 80 100 120 140 160 180
Mass number, A

30

40

50

60

70

Atomic number, Z

Figure 2: The calculated mass distribution (left) and the charge distribution (right) of 236 U,
compared with the experimental data in JENDL-4.0 [12].
116- 116 -

JAEA-Conf 2021-001

ments well at least in the less neutron-rich U isotopes. Then, the results of ﬁssion calculations
for series of U and Fm isotopes are shown in Section 3.2.

3.1

Fission fragment mass and charge distributions

For the application to the r-process simulations, we need ﬁssion properties for very neutron-richnuclei far from the β-stability line. However, experimental data in such region are not available
yet. Therefore, we ﬁrstly carry out ﬁssion calculations for U isotopes near the β-stability line.
Fig. 2 shows the results of the mass and charge distribution of ﬁssion fragments for 236 U.
The ﬁssion calculation is performed with the excitation energy, E ∗ = 10 MeV. The distributions
are compared with experimental data in JENDL-4.0 [12]. The calculated mass distribution, afundamental variable of the Langevin equations, shows good agreement with experimental data.
The charge distribution with the current simple treatment, based on the UCD, also reproduce
the experiment.
70

Langevin Cal. ( 236U(E*=10MeV) ) Yield (%)

JENDL-4.0 ( 235U(nth, f) ) Yield (%)

70⋅

Atomic number, Z

Atomic number, Z

⋅

60
⋅

50
⋅

40
⋅

30

60

⋅

⋅

50

⋅

40

⋅

⋅

30

40 50 60 70 80 90 100

40 50 60 70 80 90 100

Neutron number, N

Neutron number, N

Figure 3: The ﬁssion fragment distribution on the N –Z plane. The calculation (left) andexperimental data (right) are plotted.
Fig. 3 shows the ﬁssion fragment distribution on the N-Z plane for 236 U. The calculationis compared to the neutron-induced ﬁssion with the same compound nucleus. The width along
the N/Z line is our systematic Gaussian ﬁtting (Section 2.2). As expected by Fig. 2, calculated
values reproduce basic properties of the JENDL data.

3.2

Neutron-rich isotopes for U and Fm

Yield (%)

We perform a series of ﬁssion calculations for the neutron-rich actinoid nuclei. We show theresults of U (Z = 92) and Fm (Z = 100) isotopes with 10–20 more neutron rich from the βstability line. It is experimentally known for Fm isotopes that the ﬁssion fragmentation becomes
250U

251U

252U

253U

254U

255U

256U

100

100

100

100

100

100

100

15
10
5
0

150

150

150

150

150

150

150

Mass number, A
Figure 4: The calculated FFD for neutron-rich U (Z = 92) isotopes, 250 U to 256 U.
117- 117 -

JAEA-Conf 2021-001

the asymmetric to symmetric as the neutron number increases. Thus, the number of peaks in
FFD changes from two to one in the neutron-rich nuclei.
We adopt lower excitation energy, E ∗ = 7 MeV, corresponding to low energy environments
the r-process occurs. The calculated FFD for 250 U to 256 U are shown in Fig. 5. We ﬁnd the
distribution changes between 252 U and 253 U. The number of peaks reduced from two to one, i.e.,
the FFD becomes symmetric from asymmetric.

Yield (%)

20

250Fm

251Fm

252Fm

253Fm

254Fm

255Fm

256Fm

100

100

100

100

100

100

100

15
10
5
0

150

150

150

150

150

150

150

Mass number, A
Figure 5: Same as Fig. 4, but for Fm (Z = 100) isotopes.
We also ﬁnd the transition of the symmetry in FFD for Fm isotopes. Fig. 5 shows mass
distributions of 250−256 Fm. A drastic change in the FFD is found between 254 Fm and 255 Fm.
As this set of Fm nuclei is less neutron-rich compared to U, this feature has been suggested byprevious experiments.
This transition was found by previous works in the trans-uranium region (see, [11] andreferences therein), but suggested boundary is A = 257 line. This disagreement may cause
uncertainties in the Langevin models (model parameters) and the diﬀerence of initial conditions.
Note that Langevin calculations, based on the same numerical code as the current study, canreproduce the experiments of Fm with speciﬁc input physical parameters [11].
The transition is commonly found in our calculations for U to Db isotopes (Tanaka et al., in
prep.). Such systematic behaviour can be signiﬁcant to shape the ﬁnal abundances of r-process
calculations. Conversely, the comparison of r-process calculations with ﬁssion distributions
can restrict the ﬁssion mechanism. In previous studies, such discussions have been done withsimpliﬁed ﬁssion models. Based on dynamical ﬁssion calculation, our approach can shed lighton the microscopic features of heavy nuclei.

4

Conclusion

In the present work, we have performed ﬁssion calculations of neutron-rich nuclei using a kinetic
model for application to r-process simulations, and have shown the unique property that themass number distribution changes dramatically with one or two diﬀerent mass numbers. Sucha change in the distribution aﬀects the production of elements in the synthesis of elementsin space, and our results, including further improvements, are expected to contribute to theunderstanding of the r-process.
As for the Fm region and the neutron-rich nuclides in the U region, experimental data
have been obtained by domestic research institutes including Japan Atomic Energy Agency
and RIKEN. It is expected to verify the theoretical calculations. As for the Fm region andthe neutron-rich nuclides in the U region, experimental data have been obtained by domestic
research institutes, including Japan Atomic Energy Agency and RIKEN RIBF. It is expected
to verify the theoretical calculations. To develop a complete theoretical set of ﬁssion data, thesupporters of such future experiments are desirable.

118- 118 -

JAEA-Conf 2021-001"DLOPXMFEHNFOUT
5IJTTUVEZJTmOBODJBMMZTVQQPSUFECZ+414,",&/)* ) , ) 5IFQBSUT
PGDPNQVUBUJPOTBSFQFSGPSNFECZDPNQVUFSGBDJMJUJFTJO$G$" /"0+BOE:*51 ,ZPUP6OJWFSTJUZ

3FGFSFODFT[1] C. J. Horowitz, A. Arcones, B. Côté, and et al.: Journal of Physics G Nuclear Physics 46(2019) 083001.
[2] M. Arnould and S. Goriely: Progress in Particle and Nuclear Physics 112 (2020) 103766.
[3] J. J. Cowan, C. Sneden, J. E. Lawler, A. Aprahamian, M. Wiescher, K. Langanke,
G. Martı́nez-Pinedo, and F.-K. Thielemann: Rev. Mod. Phys. 93 (2021) 015002.
[4] S. Goriely, J. L. Sida, J. F. Lemaı̂tre, S. Panebianco, N. Dubray, S. Hilaire, A. Bauswein,and H. T. Janka: Phys. Rev. Lett.111 (2013) 242502.
[5] M. Eichler, A. Arcones, A. Kelic, O. Korobkin, K. Langanke, T. Marketin, G. MartinezPinedo, I. Panov, T. Rauscher, S. Rosswog, C. Winteler, N. T. Zinner, and F. K. Thielemann: Astrophys. J. 808 (2015) 30.
[6] S. Shibagaki, T. Kajino, G. J. Mathews, S. Chiba, S. Nishimura, and G. Lorusso: Astrophys.
J. 816 (2016) 79.
[7] N. Vassh, M. R. Mumpower, G. C. McLaughlin, T. M. Sprouse, and R. Surman: Astrophys.
J. 896 (2020) 28.
[8] S. Wanajo: Astrophys. J. 868 (2018) 65.
[9] Y. Zhu, R. T. Wollaeger, N. Vassh, R. Surman, T. M. Sprouse, M. R. Mumpower, P. Möller,
G. C. McLaughlin, O. Korobkin, T. Kawano, P. J. Jaﬀke, E. M. Holmbeck, C. L. Fryer,
W. P. Even, A. J. Couture, and J. Barnes: Astrophys. J. Lett.863 (2018) L23.
[10] S. Tanaka, Y. Aritomo, Y. Miyamoto, K. Hirose, and K. Nishio: Phys. Rev. C100 (2019)064605.
[11] Y. Miyamoto, Y. Aritomo, S. Tanaka, K. Hirose, and K. Nishio: Phys. Rev. C99 (2019)051601.
[12] K. Shibata, O. Iwamoto, T. Nakagawa, N. Iwamoto, A. Ichihara, S. Kunieda, S. Chiba,
J. Katakura, and N. Otuka: Journal of Korean Physical Society 59 (2011) 1046.

119- 119 -

JAEA-Conf 2021-001

 Extended Migdal-Watson formula to evaluate
background strength in binary breakup reactions
RiuNAKAMOTO1 , MakotoITO †1 , Akito SAITO2 , andSusumuSHIMOURA3
1

DepartmentofPureandAppliedPhysics, KansaiUniversity,Yamatecho,3-3-35, Suita
564-8680, Japan2
Department of Radiation Oncology, Hiroshima University Hospital 1-2-3 Kasumi,
Minami, Hiroshima, Hiroshima 734-8551, Japan
3
Center for Nuclear Study, School of Science, Universityof Tokyo,7-3-1,The Universityof Tokyo,
7–3Hongo,–1, Hongo,
Bunkyo-ku, Tokyo, 113-0033, Japan†
Email: itomk@kansai-u.ac.jp

New formula to describe the background strength in the binary breakup, which is inducedby the direct breakup process, is considered on the basis of the Migdal-Watson (MW) formula. The strength of the direct breakup is calculated by the complex scaling method. We
have found that the extended MW formula, which is proposed in the present study, nicely
reproduces the strength of the direct breakup calculated by Complex Scaling Method.

1

Introduction

Inelastic scattering is a useful tool to explore the intrinsic structure of the excited states ofnuclei. In particular, the inelastic excitation of the nucleus to the resonant states above thethreshold for the particle decay, which is often called the breakup reaction, is very importantbecause we can pin down the intrinsic nuclear structure in the resonances by controlling thedetection of the exit channels, which are the combination of the emitted fragments. A typicaland good example about the inelastic scattering to the continuum can be seen in the breakup
reaction of 12 Be into the α + 8 He and 6 He + 6 He channels [1]. In this experiment, the carefulmulti-pole decomposition analysis (MDA) was performed, and the MDA analysis elucidates thatmany resonant states with a sharp width of ΓR ≤ 1 MeV exist in the spins from J π = 0+ to 8+[1]. The resonances in these channels appear in a close energy spacing with ΔE ∼ 0.5 MeV in
the lower energy region below Ex ≤ 15 MeV.
In determining the resonance parameters, such as the resonance energies and the decay
widths, the evaluation of the non-resonant background strength is indispensable because theresonant enhancements, which have a strong energy dependence, are embedded in the nonresonant background contribution.
In order to extract the information about the resonance parameters precisely, it is quite
important to propose the appropriate analytic function for describing the non-resonant background contribution in the breakup reaction. In this article, we investigate the structure of
the non-resonant background strength in the binary system, which is generated by the direct
breakup process, and propose a new formula to evaluate the background contribution by extending the Migdal-Watson (MW) formula [2, 3, 4]. In the calculation of the strength for the
direct breakup, we employ the complex scaling method (CSM) [6], which is a powerful tool to120- 120 -

JAEA-Conf 2021-001

describe the few-body continuum states. From the CSM calculation, we check the applicabilityof the extended MW formula to the evaluation of the background contribution for the binary
breakup. Here we consider the breakup of 20 Ne into α + 16 O because the 20 Ne nucleus is known
to be a typical example of the binary cluster system [7, 8]
The organization of this article is the following. In section 2, theoretical formulation is
explained. This section contains the explanation of CSM, the deﬁnition of the direct breakup andthe details of the computational setting. The original Migdal-Watson theory and its extension
are explained in section 3. In section 4, the strength function calculated by CSM is analyzed, andthe validity of the extended MW formula is discussed. The ﬁnal section is devoted to summary.

2

Theoretical framework

2.1

Complex scaling method

In the present study, the direct breakup is deﬁned by the one step transition from the initial
ground state to the ﬁnal excited state embedded in the continuum. The background strength
generated by the direct breakup process is evaluated by the complex scaling method (CSM) [6].
In CSM, the transformation of the complex rotation with the rotation angle θ3Û (θ)f (r) = e 2 iθ f (eiθ r) = f θ(1)

is introduced for the arbitrary function of f (r). Here the rotation on r should be read as thetransformation on the radial part of the coordinate and hence, r → reiθ . The Schrödinger
equation transformed by this complex rotation becomesĤ θ Ψθ = E θ Ψθ ,(2)where Ψθ is deﬁned by equation (1) and Ĥ θ = Û (θ)Ĥ Û (θ)−1 . In the rotated Hamiltonian Ĥθ ,the dynamical coordinates of r contained in Ĥ is complex rotated like Ĥ θ = Ĥ(eiθ r). The
amplitude of the resonant wave function, which originally diverges in the asymptotic region, isdamped in the large distant region by this complex rotation and hence, the usual computation
technique for the bound state problem, such as the basis expansion method, is possible to apply.
The energy eigenvalues calculated from the CSM plus basis expansion technique become thediscrete and complex eigenvalue, E θ → Eνθ labeled by the eigenvalue number ν. According to
the ABC theorem [6], the energy eigenvalues for the bound state are invariant, and the energy
eigenvalues for the resonances are clearly separated from the non-resonant continuum states in
the complex energy plane [6].
The CSM is possible to apply to the calculation of the strength function, which represents
the transition strength of the initial ground state (Ψi ) induced by the external ﬁeld of Ôλ withthe multi-polarity λ [8]. The deﬁnition of the strength function of Sλ (E) is given bySλ (E) =| < Ψf |Ôλ |Ψi > |2 δ(E − Ef ) ,(3)

fwhere Ψf denotes the ﬁnal state belonging to the f -th eigenstate excited by the external ﬁeld ofÔλ . By introducing the complex rotation given by equation (1) and the extended completeness
relation [6], the strength function is rewritten like1
� Rλ (E)πwith the response function of Rλ (E) deﬁned bySλ (E) = −Rλ (E) =(4)

 < Ψ̃θ |(Ô † )θ |Ψθν >< Ψ̃θν |Ô θ |Ψθ >
i

ν

λ

λ

E − Eνθ121- 121 -i.

(5)

JAEA-Conf 2021-001

Here the Ψθ is the solution of CSM, and the tilde in the bra-state means that the complex
conjugate is not taken for the radial part of the wave function [6].

2.2

Setting of theoretical calculation

In the present study, the direct breakup of 20 Ne into α + 16 O is considered because the 20 Ne isa typical example of the binary cluster system [9]. In the calculation of the α + 16 O system, thecomputational setting is the same as the setting in reference [7]. The interaction potential V is
composed of the nuclear (VN ) and Coulomb (VC ) potentials, and their explicit form is given by
V (R)

=

VN (R)=VC (R)=VN (R) + VC (R)(6)
2−154 · exp(−0.1102R )e2· erf(0.4805R)
16 ·
R

(7)
(8)

with the deﬁnition of the error function of2
erf(x) = √π xexp(−t2 )dt .

(9)0

The computational process to prepare the initial wave function (Ψi ) and the ﬁnal one (Ψf )for the α − 16 O relative motion is also the same as those in reference [7]. The pseudo potential
with the harmonic oscillator wave function is included to exclude the Pauli’s forbidden states insolving the Schrödinger equation with the potentials shown in equations (6), (7) and (8) [7, 8].
2.2.1

Operators for direct breakup

In the present analysis, the standard operator with the multi-polarity of λ = 2 is used as theexternal ﬁeld inducing the direct breakup. Namely, in the calculation of the matrix element inequation (3), we use Ôλ=2 exciting the relative wave function of two clusters, such as√Ôλ=2 = 4πR2 Y2,0 (R̂) ,(10)
where R denotes the relative coordinate of two clusters. In addition, we consider the higher
order operator for the monopole excitation, which is given by√Ôλ=0 =
4πR2 Y0,0 (R̂) .
(11)
The importance of the cluster excitation by this higher order operator has recently been pointed
out in references [12, 13].
A special treatment is required in the calculation of the monopole transition using equation (11). In the matrix element for the direct breakup in equation (3), the operation of themonopole operator on the initial wave function in the ground state generates the superpositionof a series of the wave functions, which contains both of the ground and excited states. Thus, theground state component must be extracted from the product of the monopole operator and theinitial wave function, which is called the initial wave packet [2]. This exclusion can be achievedby the replacement in the radial operator of R2 → R2 − < R2 >, in which < R2 > denotes the
expectation value of R2 with the ground wave function.

122- 122 -

JAEA-Conf 2021-001

3Migdal-Watson theory and its extension

In the s-wave breakup of the binary system composed of the charge neutral particles, the strength
function can be expressed by the closed formula in the case of the short range limit of the initialstate. This formula is called the Migdal-Watson (MW) theory [3, 4], which expresses the strength
function in terms of the eﬀective range theory [5]. The detailed explanation of the MW formulaand its application to the breakup of the di-neutron system is reported in reference [2]. Here
we explain the essence of the MW formula and extend the formula to the case of the binary
breakup reaction including the eﬀects of the the ﬁnite charge, the ﬁnite spin and the ﬁnite size.
In the MW theory, the monopole strength of the direct breakup with the relative energy E
for the binary fragments (Sλ=0 (E)) is given by√
E
S0 (E) ∝,(12)2
AE + BE + C
where the constants of A, B and C are function of the scattering length and the eﬀective range[2, 3, 4]. The MW formula in equation (12) must be valid for the breakup from the initial wave
packet strongly localized inside of the nuclear interaction.
The MW formula shown in equation (12) is valid for the s-wave breakup from the initialwave packet localized inside of the nuclear interaction, which corresponds to the tightly binding
system composed of the charge neutral fragments. Here we try to extend equation (12) so as todescribe the direct breakup reaction of the general binary systems, which have the ﬁnite charge,
the ﬁnite spin in the ﬁnal scattering state (Sλ�=0 (E)) and the ﬁnite size of the initial wave packet.
We extend equation (12) to the following function:
Sλ (E) ∝Pλ (ka)e−βE.
AE 2 + BE + C(13)In this function, Pλ (ka) denotes the penetration factor with the momentum k for the binary
decaying
fragments and the channel radius a. Pλ corresponds to the extension of the factor√ of√
E in equation (12). If we consider the limit of k → 0 and λ = 0, Pλ (ka) is reduced to E.
On the contrary, β in the exponential term simulates the eﬀect of the ﬁnite size of the initial
packet. β should be small in the case of the limit of the strong binding system, and vice versa.
We try to reproduce the background strength generated by the direct breakup by controllingthe ﬁve ﬁtting parameters: A, B, C, a, β.

4Results

The ﬁtting result using the extended MW formula in equation (13) is shown in the two panels ofﬁgure 1. The quadrupole and monopole strengths for 20 Ne → α + 16 O are shown in the left andright panels, respectively. The calculated strength functions (solid curves) are nicely reproducedby the extended MW formula (open circles). In both the panels, the solid circle with the error
bar means the resonance energy (ER ) with the decay width (ΓR ) of the potential resonance inthe ﬁnal state. The peak structure in the strength function nicely corresponds to the resonanceenergy and the width and hence, the enhancement is originated from the resonance formation.
In the ﬁtting analysis of the quadrupole transition, we do not use the original resonanceparameter (ER = 4.2 MeV and ΓR = 2.8 MeV) but the tuned parameters for the Breit-Wigner
part: A = 0.025, B = −0.21, C = 0.48, a = 5.5 fm and β = 0.015 MeV−1 in equation (13). In
the monopole transition,
the resonance parameter of the 0+ resonance is ER = 3.3 MeV and ΓR = 2.0 MeV. The
parameters used for the ﬁtting to the monopole transition are A = 0.029, B = −0.19, C = 0.33,
123- 123 -

JAEA-Conf 2021-001

a = 5.0 fm and β = 0.015 MeV−1 , in which (A, B, C) are modiﬁed from the original resonanceparameters.
25

quadrupole

monopole20

S 0( E ) [fm4/MeV]

S 2( E ) [fm4/MeV]

20

15

15

10

10

5

0

5

0

2

4

6

8

10

12

14

16

18

0

20

E [MeV]

0

2

4

6

8

10

12

14

16

18

20

E [MeV]

Figure 1: Comparison of the strength function of 20 Ne → α + 16 O with ﬁtting results by theextended Migdal-Watson formula in equation (13). The left panel shows the quadrupole (S2 (E))
transition, while the right one shows the monopole (S0 (E)) transitions. The α threshold energy
is set to the zero point in the abscissa. In both of the panels, the solid curve and the open
circles represent the strength function calculated from CSM and ﬁtting results by equation (13),respectively. The solid circle with the error bar shows the resonance energy with the decay
width.
In the monopole transition, the excitation energy of the peak position corresponds to about
10 MeV, and this energy is much lower than the excitation energy of the monopole single particle
excitation, which reaches about 30 MeV in this mass region [10]. One of the characteristic featurein the α cluster excitation is that the strong monopole strength appears at the lower excitationenergy region as pointed out in the previous calculations [10, 11]. Therefore, the extended
MW formula, which is developed by the present analysis, is important in the evaluation of the
low-lying strength of the monopole transition induced by the α cluster excitation.

5

Summary

In summary, we have investigated the feature of the strength function for the direct breakup
process, in which a bound nucleus dissociates into the binary fragments. The direct breakup
process is deﬁned by the direct and one-step transition from the speciﬁc component of the binary
channel in the many-body bound state to the distorted wave for this channel, which is generated
by the nuclear and Coulomb potentials in the ﬁnal scattering state. The transition strength ofthe direct breakup is considered to be the main component of the non-resonant backgroundstrength in the realistic breakup experiment.
In order to describe the background strength in the simple manner, we have considered theanalytic function by extending the Migdal-Watson (MW) formula [3, 4, 5], which has recently
been discussed in the s-wave breakup of the di-neutron system [2]. The MW formula gives√thefunction of the quadratic energy denominator times the square root of energy, such as E/(AE 2 + BE + C). This formula is valid for the s-wave binary breakup of the charge neutral
system, and the initial wave function is assumed to be strongly conﬁned inside of the short range
nuclear interaction.
We have extended the MW formula so as to include the eﬀects of the ﬁnite√ spins, the ﬁnite
charge and the ﬁnite size of the initial wave packet. First, the numerator of E is replaced by
124- 124 -

JAEA-Conf 2021-001

the penetration factor of Pλ (ka) to take into account the eﬀects of the ﬁnite spin (λ) and ﬁnite
charge.
Furthermore, we have introduced the exponential damping factor, exp(−βE), which is originated from the tunneling tail of the initial wave packet outside of the nuclear interaction.
The extended MW formula proposed for the direct breakup is
Pλ (ka) · exp(−βE).
AE 2 + BE + C(14)

We have tested the extended MW formula by ﬁtting the strength function obtained fromthe theoretical calculation of the direct breakup. Here we have evaluated the strength by the
direct breakup in 20 Ne → α + 16 O [7] on the basis of the formulation of the complex scaling
method (CSM) [6]. In the CSM calculation of the monopole and quadrupole transitions, we have
conﬁrmed that the resonant peak appears around E ∼ 5 MeV above the α threshold energy,
and the strength functions are nicely reproduced by the extended MW formula. Since we have
conﬁrmed the availability of the MW formula in the direct breakup in the binary system, it isimportant to apply the formula to other binary breakup reactions, such as 12 Be → α + 8 He [1].
The application to 12 Be is now under progress.

Acknowledgments
We would like to thank Ms. N. Nishida, Mr. R. Ikegawa, Mr. M. Matsushita, Mr. H. Yamada
and all the members of the Quantum Many-body Physics Laboratory at Kansai University for
their useful discussions and kind support. One of the authors (M. I.) thanks Prof. H. Otsu at
RIKEN for kind support and encouragement.

References[1] A. Saito et al., Mod. Phys. Lett. A, Vol. 25, No. 21−23, 2010, pp. 1858-1861.
[2] S. Shimoura, Eur. Phys. Jour. Plus 133, 2018, 463.
[3] A. Migdal, Sov. Phys. JETP 1, 1955, 2.
[4] K. Watson, Phys. Rev. C88, 1952, 1163.
[5] N. Austern, Nucl. Phys. 7, 1958, 195.
[6] S. Aoyama, T. Myo, K. Katō and K. Ikeda, Prog. Theor. Phys. 116, 2006, and references
therein, pp.1-35.
[7] A. T. Kruppa and K. Katō, Prog. Theor. Phys. 84, 1990, 1145.
[8] T. Myo, A. Ohnishi and K. Katō, Prog. Theor. Phys. 99, 1998, 801.
[9] H. Horiuchi et al., Prog. Theor. Phys. Suppl. 2012 Jan; 192: 1-238 , and references therein.
[10] T. Yamada, Y. Funaki, H. Horiuchi, K. Ikeda, and A. Tohsaki, Prog. Theor. Phys. 120,
2008, 1139.
[11] T. Yamada, Y. Funaki, T. Myo, H. Horiuchi, K. Ikeda, G. Röpke, P. Schuck, and A. Thosaki,
Phys. Rev. C85, 2012, 034315.
[12] Y. Chiba, M. Kimura, Y. Taniguchi, Phys. Rev. C93, 2016, 034319.
[13] Y. Chiba, Y. Taniguchi, M. Kimura, Phys. Rev. C95, 2017, 044328.

125- 125 -

JAEA-Conf 2021-001

 Evaluation of Neutron Nuclear Data on Cobalt-59 for JENDL-5
Nobuyuki Iwamoto
Nuclear Data Center, Nuclear Science and Engineering Center, Japan Atomic Energy Agency,
Tokai, Ibaraki 319-1195, Japane-mail: iwamoto.nobuyuki@jaea.go.jp

The neutron nuclear data of 59 Co were evaluated in the energy region of 10−5 eV to 20 MeV
for the development of JENDL-5. The resonance parameters and total cross sections were takenfrom the measurement by de Saussure et al. in the resolved and unresolved resonance regions, respectively. The thermal capture cross section was evaluated using available measured data. The
present data were consistent with the values in major evaluated libraries. In the fast neutronenergy region the evaluation was made with various types of measured data by the nuclear reaction calculation code CCONE. It is found that the present results well reproduce the measured
data.

1

Introduction

Cobalt is a monoisotope element, and the stable isotope is 59 Co. Cobalt is one of the important
structural materials and is contained in carbon steel and concrete as well as SUS304. Therefore,
the accurate nuclear data of 59 Co are requisite for analyses in nuclear and accelerator facilities;
speciﬁcally radioactivity estimation of 59 Fe (half-life 44.5 d), 58 Co (70.9 d) and 60 Co (5.27 y)related to decommissioning of the facilities.
The nuclear data of 59 Co [1] in the general purpose library JENDL-4.0 are based on theevaluation in 1988. Since the early evaluation, a partial revision was made at the JENDL-3.3
evaluation in 2001 [2]. After the release of JENDL-3.3, many measurements have been done for,e.g., capture, (n, 2n), (n, p), and (n, α) reactions. Therefore, the reconsideration of nuclear data
is required for the development of JENDL-5.

2

Evaluation methods and results

The evaluation of 59 Co was divided into three energy regions: resolved resonance region, unresolved resonance region and fast neutron energy region. Evaluation details and obtained results
will be explained below.

2.1

Resolved resonance region

The resonance parameters and scattering radius were taken from the data of de Saussure et al. [3],who made the detailed analysis of resonance parameters, using neutron transmission data with
diﬀerent sample thicknesses measured at ORNL. Figures 1 and 2 illustrate the present total crosssections and the data of JENDL-4.0, together with the measured data with sample thicknessesof 0.021, 0.075 and 0.301 atoms/barn and sample temperature of 293 K in the energy range of
10−5 eV to 100 keV.
The capture cross sections calculated by the resonance parameters were compared with thedata of Spencer & Macklin [4] in Figures 3 and 4. JENDL-4.0 has more resonances than thepresent result. They come from the resonance data [4, 5, 6], in which Spencer & Macklin [4]provided only capture kernel data for many resonances. The capture kernel data might be useful,
if average values of radiation widths, for example, were assumed. Nevertheless, the use of theirdata was ﬁnally rejected because reasonable values of neutron width were not obtained for many
resonances, assuming the average radiation width of 0.36 eV for p-wave resonances [3].
126

- 126 -

JAEA-Conf 2021-001

103

Present
JENDL-4.0
de Saussure+ (1992; 0.301 at/b)
de Saussure+ (1992; 0.075 at/b)
de Saussure+ (1992; 0.021 at/b)

102

Cross section (b)Cross section (b)

103

101

100

10-1

0

10

20

30

40

102

101

100

10-1

50

Present
JENDL-4.0
de Saussure+ (1992; 0.301 at/b)
de Saussure+ (1992; 0.075 at/b)
de Saussure+ (1992; 0.021 at/b)

50

60Incident energy (keV)

Figure 1: Comparison of the present total crosssection with measured data, together withJENDL-4.0, in the energy region of 10−5 eV
to 50 keV.

Cross section (b)Cross section (b)

90

100

Present
JENDL-4.0
Spencer+ (1976a)
Spencer+ (1976b)

101

100
10-1
10-2
10-3
10-4

80

Figure 2: Same as Figure 1, but in the energy
region of 50 to 100 keV.

Present
JENDL-4.0
Spencer+ (1976a)
Spencer+ (1976b)

101

70

Incident energy (keV)

100
10-1
10-2
10-3

0

10

20

30

40

10-4

50

Incident energy (keV)

50

60

70

80

90

100

Incident energy (keV)

Figure 3: Comparison of the present capture cross section with measured data, together with JENDL-4.0, in the energy regionof 10−5 eV to 50 keV.

Figure 4: Same as Figure 3, but in the energy
region of 50 to 100 keV.

Thermal capture cross section was evaluated with measured data. Most of the measurements
was made, based on the absorption cross section of natural boron, and capture cross sectionof gold as a monitor cross section. In the present evaluation, the two monitor cross section
values adapted in the published data were corrected with the IAEA Neutron Data Standards [7].
In addition, uncertainty estimation was made by the method in the report [8]. The obtained
result of capture cross section was 37.31(21) b. This value is almost consistent with the data of
JENDL-4.0 (37.20(524) b), ENDF/B-VIII.0 (37.17 b) [9] and JEFF-3.3 (37.17 b) [10] as shownin Figure 5. The neutron and radiation widths of negative resonance at −226 eV were revised
to reproduce the present value.

2.2

Unresolved resonance region

Resonances are hard to be resolved one by one due to physical nature of resonances and/or
experimental conditions as an incident energy increases. This region is called as unresolved
resonance region, where cross sections ﬂuctuate and are not smooth, in general. To keep theseshapes is important for shielding calculations in nuclear and accelerator facilities. In the present
evaluation, the data of thick sample (0.301 atoms/barn) of de Saussure et al. [3] were adopted
127- 127 -

JAEA-Conf 2021-001

Figure 5: Comparison of capture cross section at thermal energy with measured data,
together with evaluated data. The black open
circles indicate the original values by the authors; the orange ﬁlled circles stand for thevalues corrected with the latest standard crosssections.

Present

JENDL-4.0

Mughabghab (2018)

ENDF/B-VIII.0, JEFF-3.3

Gryntakis (1976)

Farina Arbocco+ (2013)

Silk (1970)

Deworm (1972)

Schuman+ (1969)

Merritt+ (1968)

Kim+ (1968)

Vaninbroukx (1966)

Berreth+ (1962)

Carre+ (1966)

Meadows+ (1961)

Wolf (1960)

Yae+ (1951)

34

Ailloud+ (1952)

38
36

Tattersall+ (1960)

40

Stefanescu+ (1961)

Corrected data
Original data

42

Pomerance (1951)

Thermal capture cross section (b)

44

32
30

101

Present
JENDL-5.0
de Saussure+ (1992; 0.401 at7b)de Saussure+ (1992; 0.0/ 3 at7b)

Present
JENDL-5.0
de Saussure+ (1992; 0.401 at7b)de Saussure+ (1992; 0.0/ 3 at7b)

Cross section (b)Cross section (b)

102

101

100

10-1
100

130

200

230

400

430

500

530

100

300

Incident energy (keV)

600

800

1000

1200

1500

1600

1800

2000

Incident energy (keV)

Figure 6: Comparison of total cross section
with measured data, together with JENDL-4.0,
in the energy region of 100 to 500 keV.

Figure 7: Same as Figure 6, but in the energy
region of 500 to 2000 keV.

from 100 keV to 1.5 MeV, above which the data of thin sample (0.075 atoms/barn) were taken
up to 5 MeV. The direct use of measured data have disadvantages because experimental eﬀects ofmultiple-scattering and resolution function are not corrected. Nevertheless, the measured data
were adopted without any changes, since we do not have proper ways to derive perfect crosssections in this region. The same choices were made in the past JENDL evaluation. The present
result is thus similar to JENDL-4.0 as shown in Figures 6 and 7. The diﬀerence can be seen
as deep valley of the resonances in JENDL-4.0. This might be due to improper interpolation of
measured data.

2.3

Fast neutron energy region

In the fast neutron energy region, neutron cross sections were calculated by using the nuclear
reaction calculation code CCONE [11], which composes of the coupled channels optical model
code CCOM and the Hauser-Feshbach statistical model code CCSM.
The CCOM code was used to calculate neutron transmission coeﬃcients of 59 Co. The opticalmodel potential was taken from a functional form of Kunieda et al. [12]. The coupled levels
were ground state (J π =7/2− ) and two excited levels (Ex , J π )=(1.19, 9/2− ) and (1.46, 11/2− ),where J π is the spin-parity and Ex is the excitation energy in MeV. The potential parameters
were modiﬁed to reproduce the total cross section and elastic scattering angular distributions.
In the use of total cross sections, the data of Abfalterer et al. [13] were taken into account up to
200 MeV, up to which the nuclear data will also be included in JENDL-5 with the form of the
production cross sections of residual nuclides.
128- 128 -

JAEA-Conf 2021-001

5000

Present
JENDL-4.0
Abfalterer+ (2001)
Abfalterer+ (2000)
Desaussure+ (1992f)
Desaussure+ (1992e)
Desaussure+ (1992d)
Desaussure+ (1992c)
Desaussure+ (1992b)
Desaussure+ (1992a)
Guenther+ (1974)
Fisher+ (1972)
Angeli+ (1971)
Foster Jr+ (1971)
exp. (before 1970)

4000
3500
3000
2500
2000
1500
1000

101

Smith+ (1988; 9.06MeV)
Velkley+ (1974; 8.97MeV)
Smith+ (1988; 5MeV
Simakov+ (1981;4.99MeV)
Kinney+ (1970; 5MeV)

105
Angular distribution (mb/sr)

Cross section (mb)

4500

104
103
102

En=5MeV101

En=9MeV (x0.05)

100
10-1
10-2

En=14MeV (x0.001)

10-3

102

20

40

Figure 8: Comparison of the present total
cross section with measured data, together
with JENDL-4.0.

Cross section (mb)

Cross section (mb)

25
20
15

Ikeda+ (1988)
Meadows+ (1987)
Garlea+ (1985)
Bahal+ (1985)
Agrawal+ (1984)
Berrada (1984)
Zhou+ (1981)
Ghorai+ (1980)
Zupranska+ (1980)
exp.(before 1980)

5
0

4

30
20

6

8

10

2

4

12

14

160

180

6

8

10

12

14

16

18

20

Present
JENDL-4.0
Kinney+ (1970): En=5.44MeV, Ang= 37.5deg
Kinney+ (1970): En=5.44MeV, Ang= 72.0deg (x10-1)
Kinney+ (1970): En=5.44MeV, Ang= 93.5deg (x10-2)
Kinney+ (1970): En=5.44MeV, Ang=114.0deg (x10-3)

103

10

140

Figure 11: Comparison of the present (n, p)
reaction cross section with measured data, together with JENDL-4.0.

DDX (mb/sr/MeV)

Cross section (mb)

30

40

104

Present
JENDL-4.0
Filatenkov (2016)
Mannhart+ (2007)
Doczi+ (1998)
Osman+ (1996)
Uno+ (1996)
Molla+ (1994)
Grallert+ (1993)
Garlea+ (1992)
Ercan+ (1991)
Litingyan+ (1990)
Ryves+ (1988)

120

Incident energy (MeV)

Figure 10: Comparison of the present capture cross section with measured data, together
with JENDL-4.0. The evaluated production
cross section of meta state of 60 Co is added.
35

50

0

101

Incident energy (MeV)

40

60

10
100

100

Present
JENDL-4.0
Majerle+ (2016)
Filatenkov (2016)
Simeckova+ (2011)
Mannhart+ (2007)
Shimizu+ (2004)
Semkova+ (2004)
Cezarsuita+ (1997)
Uno+ (1996)
Osman+ (1996)
Molla+ (1994)
Garlea+ (1992)
Ercan+ (1991)
Viennot+ (1991)
Litingyan+ (1990)
exp. (before 1990)

70

100

10-1
10-1

80

Figure 9: Comparison of the present elastic
scattering angular distribution with measured
data, together with JENDL-4.0.
80

Present,msPresent
JENDL-4.0
Paulsen (1967),ms
Johnsrud+ (1959),ms
Budnar+ (1979)
Spencer+ (1976)
Rigaud+ (1971)
Paulsen (1967)

101

60

Scattering angle (deg)Incident energy (MeV)

102

Present
JENDL-4.0
Fujita+ (1972; 14.1MeV)
Takahashi+ (1992; 14.1MeV)
St.Pierre+ (1959; 13.95MeV)

16

102
101
100
10-1
10-2
10-3

18

20

0

Incident energy (MeV)

1

2

3

4

5

6

Secondary energy in C.M. (MeV)

Figure 12: Comparison of the present (n, α)
reaction cross section with measured data, together with JENDL-4.0.

Figure 13: Comparison of the present neutron
emission double diﬀerential cross section withmeasured data, together with JENDL-4.0.

129- 129 -

JAEA-Conf 2021-001

The CCSM code is employed to calculate the compound, pre-equilibrium and direct processes
in nuclear reaction. The pre-equilibrium and direct processes were considered by two-component
exciton and DWBA models, respectively. The contribution from the direct process to inelastic
scattering cross sections was determined to reproduce corresponding measured data.
Figure 8 shows the present total cross sections compared with measured data, together withJENDL-4.0 given by averaged values of de Saussure et al. [3] and Cierjacks [14]. The data of
JENDL-4.0 has cross sections smaller than the present results above 6 MeV. The calculated
total cross sections were illustrated below 5 MeV, for checking the reproducibility of the measured cross sections by the optical model. Figure 9 shows the angular distributions of neutron
elastic scattering at incident energies of 5, 9 and 14 MeV, where the contribution of compoundelastic scattering has negligible. The present data were in good agreement with measured data.
It is found that JENDL-4.0 has larger cross sections at the scattering angles between 60 and
180 degrees, compared to the measured data.
The present capture cross sections are compared with measured data and JENDL-4.0 in
Figure 10. The result was obtained to reproduce the data of Spencer & Macklin [4] below
1 MeV. The adjustment of direct/semi-direct capture contribution was done to reproduce thedata of Rigaud et al. [15] and Budnar et al. [16]. The evaluated production cross section formeta state (Ex = 58.59 keV) of 60 Co populated by capture reaction was also shown in Figure 10
and will be included in JENDL-5. The gamma-ray strength function (in unit of 10−4 ) of s-wave
resonances in the present evaluation is 2.53, which is small in comparison with 3.88(35) [17] and3.83 [3]. This fact might indicate that the radiation width (or resonance spacing) is smaller (orlarger) than that ever known in resonance analyses.
The present (n, p) reaction cross sections are illustrated in Figure 11. The result is diﬀerent
from the data of JENDL-4.0 above 8 MeV, especially, in the energy range between 8 and 14 MeV,
due to incorporation of new data measured by activation method [18].
Figure 12 represents the comparison of the present (n, α) reaction cross sections with theseveral measurements and JENDL-4.0. The present evaluation followed the data of Mannhart etal. [18] and Filatenkov [19] between 8 and 15 MeV, supplemented with the data published after
1980 above and below the energy region. JENDL-4.0 has a little bit higher cross sections thanthe present result above 13 MeV.
The comparisons of the present data with the data of Kinney et al. [20] were made fordouble diﬀerential cross sections of secondary neutrons at incident energy of 5.44 MeV andemission angles of 37.5, 72, 93.5 and 114 deg. in Figure 13. These secondary neutrons come frominelastic and elastic scattering. A discrepancy is evident when the present data below 1 MeV
are compared to JENDL-4.0 in Figure 13. The small contribution of low energy neutrons in thepresent evaluation may be attributed to low level density, characteristic of structural materials.

3

Summary

The evaluation of neutron induced reaction data of 59 Co was made in the energy range of 10−5 eV
to 20 MeV. The evaluation was separately done in the three energy regions: resolved and unresolved resonance regions and fast neutron energy region. For the resolved and unresolved
resonance regions the data derived by de Saussure et al. were adopted without including extra resonances appeared in JENDL-4.0. The thermal capture cross section was evaluated using
available cross section data, which were corrected, based on the latest standard cross sections.
The obtained value reasonably matches the data of ENDF/B-VIII.0 and JEFF-3.3. In the fastneutron energy region, the evaluations were performed for various types of nuclear data by using
the nuclear reaction calculation code CCONE. The potential parameters of the optical model
were ﬁxed with the measured total cross sections up to 200 MeV and elastic scattering angular
distribution. The evaluated results show good agreement with the measured data. These data
will be compiled into the next general purpose library JENDL-5.
130- 130 -

JAEA-Conf 2021-001

References[1] Shibata K, Iwamoto O, Nakagawa T, et al. JENDL-4.0: A New Library for Nuclear Scienceand Engineering. J. Nucl. Sci. Technol. 2010; 48:1-30.
[2] Shibata K, Kawano T, Nakagawa T, et al. Japanese Evaluated Nuclear Data Library Version
3 Revision-3: JENDL-3.3, J. Nucl. Sci. Technol. 2002;39:1125.
[3] De Saussure G, Larson NM, Harvey JA, et al. Multilevel resonance analysis of 59 Co neutrontransmission measurements, ORNL/TM-11762 (1991).
[4] Spencer RR, Macklin RL. Neutron Capture Cross Section of Cobalt-59 in the Energy Range
2.5 to 1000 keV, Nuclear Science and Engineering 1976;61:346-355.
[5] Garg JB, Rainwater J, Havens WW. Jr. Nucl. Sci. Eng. 1978;65:76.
[6] Mughabghab SF. Atlas of Neutron Resonances - Resonance Parameters and Thermal Cross
Sections Z = 1 − 100. Elsevier (2006).
[7] Carlson AD, Pronyaev VG, Capote R, et al. Evaluation of the Neutron Data Standards,
Nuclear Data Sheets, 2018;148:143-188.
[8] Improving Nuclear Data Accuracy of the 241 Am Capture Cross-section, NEA/WPEC SG-41(NEA/NSC/R(2020)2) (2020).
[9] Brown DA, Chadwick MB, Capote R, et al. ENDF/B-VIII.0: The 8th major release of thenuclear reaction data library with CIELO-project cross sections, new standards and thermal
scattering data, Nucl. Data Sheets 2018;148:1-142.
[10] Plompen AJM, Cabellos O, De Saint Jean C, et al. The joint evaluated ﬁssion and fusion
nuclear data library, JEFF-3.3, Eur. Phys. J. 2020;A56:181.
[11] Iwamoto O, Iwamoto N, Kunieda S, et al. The CCONE code system and its application to
nuclear data evaluation for ﬁssion and other reactions. Nucl. Data Sheets 2016;131:259-288.
[12] Kunieda S, Chiba S, Shibata K, et al. Coupled-channels Optical Model Analyses of Nucleoninduced Reactions for Medium and Heavy Nuclei in the Energy Region from 1keV to
200 MeV. J. Nucl. Sci. Technol. 2007;44:838-852.
[13] Abfalterer WP, Bateman FB, Dietrich FS, et al. Measurement of neutron total cross sections
up to 560 MeV, Phys. Rev. 2001;C63:044608.
[14] Cierjacks S, Forti P, Kopsch D, et al. High resolution total neutron cross sections for Na,
Cl, K, V, Mn and Co between 0.5 and 30 MeV, Kernforschungszentrum Karlsruhe Reports
No.1000, Vol.(SUPP.2) (1969).
[15] Rigaud F, Irigaray JL, Petit GY, et al. Gamma-ray spectra following the capture of 14 MeV
neutrons by Co-59, Nb-93 and Rh-103, Nuclear Physics, 1971:A173:551-560.
[16] Budnar M, Cvelbar F, Hodgson E, et al. Prompt gamma-ray spectra and integrated crosssections for the radiative capture of 14 MeV neutrons for 28 natural targets in the mass
region from 12 to 208, INDC(YUG)-6 (1976).
[17] Mughabghab SF. Atlas of Neutron Resonances (Sixth edition), Elsevier (2018).
[18] Mannhart W, Schmidt D. Measurement of Neutron Activation Cross Sections in the Energy
Range from 8 MeV to 15 MeV, PTB-N-53 (2007).
[19] Filatenkov AA. Neutron activation cross sections measured at KRI in neutron energy region
13.4-14.9 MeV, INDC(CCP)-0460 (2016).
[20] Kinney WE, Perey FG. Neutron elastic- and inelastic-scattering cross sections for Co in theenergy range 4.19 to 8.56 MeV, Oak Ridge National Lab. Reports No.4549 (1970).
131- 131 -

JAEA-Conf 2021-001

 SCALE6.2 ORIGEN library produced from JENDL/AD-2017

Chikara KONNO *, Mami KOCHIYAMA and Hirokazu HAYASHIJapan Atomic Energy Agency
2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan
Email: konno.chikara@jaea.go.jp*

A SCALE6.2 ORIGEN library was produced from JENDL Activation Cross Section File for
Nuclear Decommissioning 2017 (JENDL/AD-2017) with the AMPX-6 code in order to popularize
JENDL/AD-2017 widely. The produced ORIGEN library of JENDL/AD-2017 was tested with the
JPDR decommissioning data, which demonstrated that the library had no problems.

1. Introduction
The SCALE code system is a modeling and simulation tool complex for nuclear safety analyses anddesigns. The SCALE6.2 code system [1] was released in 2016 (the latest version is SCALE6.2.4). The
ORIGEN code [1] in SCALE6.2 used for activation calculations in decommissioning is completely
different from the previous ORIGEN-S code [2] until SCALE6.0 [2] and has the following features.
1) The input format of ORIGEN is easy to use and understand.
2) It is expected that the calculation accuracy is improved because ORIGEN uses one group crosssection data generated from multigroup neutron spectra in all calculation points with the COUPLE
code [1] in SCALE6.2, while the ORIGEN-S code uses three group cross section data generated witha multigroup neutron spectrum in a typical pressurized-water reactor.
3) The calculation time of ORIGEN including COUPLE is at most about twice of that of ORIGEN -Seven for 200 groups.
We expect that ORIGEN in SCALE6.2 will be mainly used for activation calculations in nuclear
facility decommissioning. JAEA released JENDL Activation Cross Section File for Nuclear
Decommissioning 2017 (JENDL/AD-2017) [3] in 2018. Thus we have produced a SCALE6.2 ORIGEN
library from JENDL/AD-2017 in order to popularize JENDL/AD-2017 widely.

2. Method
The nuclear data processing code AMPX-6 [4] in SCALE6.2.4 was used to produce the SCALE6.2
ORIGEN library of JENDL/AD-2017 because the format of SCALE6.2 ORIGEN library was not open.
The processing conditions are as follows.
z Group structure : 200 groups(the same as one of the ORIGEN libraries attached in SCALE6.2)
132- 132 -

JAEA-Conf 2021-001

9 We assume transport calculations with the multigroup library MATXSLIB-J40 (neutron : 199
groups) [5].
9 The 200 group structure is the same as the 199 group structure except for its first group.
z Temperature : 300 K
9 We assume activation calculations for bio-shield concrete.
z Weight function : Maxwell+1/E+Fission spectrum + 1/E (above 10 MeV)z Infinite dilution cross sections
Input data of AMPX-6 are very complicated. We used the ExSite code [4] in SCALE6.2.4 in orderto generate a typical template input file for AMPX-6. We produced an ORIGEN library from each file of
JENDL/AD-2017 with AMPX-6 and the template input and combined all the ORIGEN libraries to one
ORIGEN library with AMPX-6.
We encountered several problems during the processing of JENDL/AD-2017 with AMPX-6. Thus
we adopted the following coping strategies.
z We used the 0K MF10 version of JENDL/AD-2017 because AMPX-6 could not process the 0K MF9
version.
z We modified a metastable state level based on the decay data of SCALE6.2 (ex. 134mCs level : 3 in
JENDL/AD-2017, 1 in decay data of SCALE6.2).
z JENDL/AD-2017 includes resonance data which should not be used to re-construct cross section data.
However AMPX-6 re-constructs and adds cross section data with the resonance data in JENDL/AD2017 as shown in Fig. 1. Thus we removed the resonance data in JENDL/AD-2017.

3. Comparison with Continuous Energy Cross Section
Two hundred group cross sections of typical nuclei and reactions in the produced ORIGEN libraryof JENDL/AD-2017 were extracted with the graphical user interface code Fulcrum [1] for visualizing
SCALE libraries in SCALE6.2.4 because the format of the ORIGEN libraries is not open. Figures 1 to 4
plot them with continuous energy ones produced with the nuclear data processing code NJOY [6]. The
figures show that the processing of the modified JENDL/AD-2017 with AMPX-6 is adequate.

4. Test with JPDR Activation Calculation
We calculated radioactive inventories in bio-shield concrete of JAEA JPDR (Japan Power
Demonstration Reactor) [7], whose decommissioning completed in 1996, for validating the produced
ORIGEN library of JENDL/AD-2017. Neutron spectra inside the concrete are calculated with the Sn
DORT code [8], a 199 group library including up-scattering data from MATXSLIB-J40 and a partial
JPDR model shown in Fig. 5. Radioactive inventories were calculated in the concrete with COUPLE and
ORIGEN in SCALE6.2.4 and the calculated neutron spectra, where two activation libraries were used;the 200 group library produced from JENDL/AD-2017 and the 200 group library [1] attached in
SCALE6.2 (produced from JEFF-3.1/A [9]). “0.0” was added before 199 group neutron spectra because
the first group value of the 200 group structure was lack in the 199 group structure and negligibly small.
The elapsed time for 161 ORIGEN and COUPLE calculations was 4 minutes, which is not so longcompared with 2.5 minutes of 161 ORIGEN-S calculations. Figure 6 shows the calculated radioactivity
distribution at Z=340 cm (cooling time : 15 years). The calculation results with two libraries are almost
the same, which suggests that the ORIGEN library from JENDL/AD-2017 has no problems. The
133- 133 -

JAEA-Conf 2021-001

calculated results are different from the measured ones. This is considered to be due to reinforced steel
in the bio-shield concrete, which was not included in the calculations.

5. Summary
A 200 group SCALE6.2 ORIGEN library from JENDL/AD-2017 was produced with AMPX-6.
Radioactive inventories in bio-shield concrete of JAEA JPDR were calculated with ORIGEN in
SCALE6.2.4 for testing the library. As a result, it was demonstrated that the produced library had no
problems. The produced library will be released from JAEA.

References[1] Wieselquist, W.A., Lefebvre, R.A., Jessee, M.A., SCALE Code System, ORNL/TM-2005/39
Version 6.2.4, 2020.
[2] ORNL, SCALE: A Modular Code System for Performing Standardized Computer Analyses forLicensing Evaluation, ORNL/TM-2005/39 Version 6, 2009.
[3] https://wwwndc.jaea.go.jp/ftpnd/jendl/jendl-ad-2017.html (accessed 2021-01-08).
[4] Wiarda, D., Dunn, M.E., Greene, N.M., Williams, M.L., Celik, C., Petrie, L.M., AMPX-6: A
Modular Code System for Processing ENDF/B, ORNL/TM-2016/43, 2016.
[5] https://rpg.jaea.go.jp/main/ja/library_matxslibj40/ [in Japanese] (accessed 2021-01-08).
[6] MacFarlane, R.E., Muir, D.W., Boicourt, R.M., Kahler, A.C., Conlin, J.L., The NJOY Nuclear
Data Processing System, Version 2016, LA-UR-17-20093, 2016.
[7] Kocherov, N.P. (Ed.), International benchmark calculations of radioactive inventory for fission
reactor decommissioning, INDC(NDS)-355, 1996.
[8] ORNL RSICC, DOORS3.2a: One, two- and three-dimensional discrete ordinates
neutron/photon transport code system, CODE PACKAGE CCC-650, 2007.
[9] Sublet, J-Ch., Koning, A.J., Forrest, R.A., Kopecky, J., The JEFF-3.0/A Neutron Activation
File—New Features, Validation, and Usage, AIP Conference Proceedings, vol. 769, 2005,
pp.203-206.

134- 134 -

JAEA-Conf 2021-001

Fig. 1

Capture cross section of 238U in JENDL/AD-2017.

Fig. 2

Cross section of 59Co(n,J)60gCo in JENDL/AD-2017.

135- 135 -

JAEA-Conf 2021-001

Fig. 3

Cross section of 151Eu(n,J)152gEu in JENDL/AD-2017.

Fig. 4

Cross section of 153Eu(n,J)154gEu in JENDL/AD-2017.

136- 136 -

JAEA-Conf 2021-001

Z

air

liner
fuel2

steam

fuel1

liner

water1

vesselcladding

fuel2

136.5

shroudfuel3

airwater1chimney

510.0

vesselwater2

concreteconcreteairshielding

fuel1

air

R

136.5

Fig. 5

Unit : cm

Two-dimensional JPDR calculation model. Only the colored region was used in DORT
calculation.

Fig. 6

Radioactivity distribution at Z=340 cm (cooling : 15 years).
137- 137 -

JAEA-Conf 2021-001

 Experimental plan for displacement damage cross sections using
120-GeV protons at Fermi National Accelerator Laboratory

Yosuke IWAMOTO1,2*, Makoto YOSHIDA3, Shin-ichiro MEIGO2, Katsuya YONEHARA4,
Taku ISHIDA3, Keita NAKANO2, Shin-ichiro ABE1, Hiroki IWAMOTO1,2, T. SPINA4,
K. AMMIGAN4, N. MOKHOV4, Atsushi YABUUCHI5, and Toshimasa YOSHIIE 5
1

Nuclear Science and Engineering Center, Japan Atomic Energy Agency
2-4 Shirakata, Tokai, Naka, Ibaraki 319-1195, Japan
2J-PARC Center, Japan Atomic Energy Agency

2-4 Shirakata, Tokai, Naka, Ibaraki 319-1195, Japan
3J-PARC Center, High Energy Accelerator Research Organization

1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
4Fermi National Accelerator Laboratory
Batavia IL 60510-5011, U.S.
5Institute for Integrated Radiation and Nuclear Science, Kyoto University

2, Asashiro-Nishi, Kumatori, Sennan, Osaka 590-0494, Japan*

Email: iwamoto.yosuke@jaea.go.jp

For the validation of the number of displacements per atom (dpa) calculated by Monte Car lo codes,
an experimental program has been launched to measure displacement cross sections of metals with
120-GeV protons at Fermilab Test Beam Facility (FTBF) in Fermi National Accelerator Laboratory(FNAL). Experiments will be performed at the M03 beam line high-rate tracking area in FTBF in the US
fiscal year 2022 (October 2021 – September 2022). For the preparation of experiments, the sample
assembly with four-wire samples of aluminum, copper, niobium and tungsten with 250-Pm diameter havebeen developed. The sample assembly will be maintained at around 4 K by using a Gifford–McMahon(GM) cryocooler in a vacuum chamber. Then, changes in the electrical resistivity of samples will beobtained under 120-GeV proton irradiation. To obtain a sufficient resistance increase under the beamirradiation, approximately 40 hours is needed for all samples. Recovery of the accumulated defects
through isochronal annealing, which is related to the defect concentration in the sample, will also bemeasured after the cryogenic irradiation.

1. Introduction
To predict the operating lifetime of materials in high-energy radiation environment at accelerator
facilities, Monte Carlo codes such as PHITS[1,2,3], MARS[4], and FLUKA[5] are used to calculate thenumber of displacements per atom (dpa) related to the number of Frenkel pairs. The Norgertt–Robinson–
Torrens (NRT) model has been widely used to predict the number of the “initial” Frenkel pairs (NRT138- 138 -

JAEA-Conf 2021-001dpa) [6]. For more accurate estimation of the actual damage production, athermal-recombinationcorrected displacement damage (arc-dpa) was proposed [7]. For the validation of codes, it is necessary tomeasure displacement cross-sections of metals in relation to changes in electrical resistivity at cryogenic
temperature (around 4 K) where the recombination of Frenkel pairs by thermal motion is well suppressed.
To validate the code, we developed the cryogenic irradiation chamber and measured displacement
cross section of copper with 125 MeV protons [8], data of aluminum, copper and tungsten with 200 and
389 MeV protons [9,10], and data of copper and iron with 0.4 – 3 GeV protons [11], respectively. The
comparison of displacement cross sections between the data and calculated results indicates that the arcdpa results are in a good agreement with the data while the NRT-dpa results are larger than the data by
about a factor of three. The measurement of aluminum, copper, iron and tungsten with 30-GeV protons
will be performed at J-PARC. Since there is no experimental data with energy over 30 GeV, we havelaunched an experimental program to measure displacement cross sections of metals with 120-GeV
protons at Fermilab Test Beam Facility (FTBF) in Fermi National Accelerator Laboratory (FNAL). In
this paper, we introduce the experimental plan and the progress of the preparation.

2. Experimental plan and progress of the preparation
2.1. Experimental device
Experiments will be performed at the M03 beam line high-rate tracking area in FTBF in the US
fiscal year 2022 (October 2021 – September 2022). The beam consists of 120 GeV protons. The lengthof spill is 4.2 seconds and approximate repetition is 60 seconds. Figure 1 shows the layout of theexperimental area at M03 and picture of the irradiation chamber with the cold head of the GiffordMcMahon (GM) cooler (RDK-408D2, Sumitomo Heavy Industries, Ltd.) with 1.0 W cooling capacity at
4.2 K.

Figure 1: The experimental area at M03 (left) and an irradiation chamber with the GM cooler (right).
The irradiation chamber developed in our previous study [9,10] will be put on the beam line in theexperimental area. A data taking system and the helium gas compressor for the operation of the GM
cryocooler will be set at the data taking area. A segmented wire ionization chamber (SWIC) will be
installed for the beam profile at front and back of the irradiation chamber. Beam scan is possible in139- 139 -

JAEA-Conf 2021-001

horizontal and vertical directions with SWIC. An ion chamber operational in the upstream enclosure in
the same beamline will be used for the beam current measurement. Figure 2 shows layout of the irradiationchamber drawn by PHITS.

Figure 2: Layout of the irradiation chamber with the cold head of the GM cryocooler drawn by PHITS.
The sample assembly is connected with the cold head of the GM cryocooler and 1-mm-thick aluminum
shields cover the entire sample assembly to intercept any thermal radiation from the irradiation chamber.
Two 50.8 Pm thick titanium windows will be connected with the irradiation chamber as a vacuum
partition. Figure 3 shows the sample assembly connected with the cold head of the GM cryocooler in theirradiation chamber and the data taking system.

Figure 3: The sample assembly connected with the cold head of the GM cryocooler in the irradiationchamber (left) and the data taking system (right).
140- 140 -

JAEA-Conf 2021-001

The aluminum plate is a support plate of a wire sample with a beam hole open to the beam. A root meansquare (RMS) beam size can be 4 mm for protons. Since a 5-sigma of beam size or more is needed forthe beam clearance in this experimental area at M03, the diameter of the beam hole was set to 48 mm(6-sigma). Since beam loss permits less than 3 % of the interaction length at M03, which is 12 mm for
120 GeV proton on aluminum, we cannot use aluminum nitride plates and the aluminum plates covering
the sample wire in the beam line in the same way as our previous experiments at RCNP, Osaka university[9,10]. In the experiment at M03, four wire samples, aluminum, copper, niobium, and tungsten, with a
250-Pm diameter were attached as shown in Figure 3 to minimize a beam loss. Before attaching an
aluminum plate, wire samples were annealed with a vacuum electric furnace for aluminum and copperand an electron gun for niobium and tungsten. Table 1 lists the annealing temperature for these samples.
Table 1: Melting point, annealing temperature and annealing time for wire samples.
Melting point (K)Annealing temperature (K)Time (min.)

Al

933.5

840

30

Cu

1358

1289

30

Nb

2750

1923

15

W

3695

2473

15

Annealing under vacuum conditions (~10-4 Pa) was performed by heating the samples to the temperatures
shown in Table 1.
The electrical resistance of wire will be measured using an apparatus combining a current source(model 6221, Keithley Instruments Inc.) and a nano-voltmeter (model 2182A, Keithley Instrument Inc.).
This apparatus is based on four-point technique with cancel effects of thermal electromotive force. The
precision of the electrical resistance at 3 K was 0.001 P:. A CX1050-CU-HT Cernox resistancethermometer was attached in the aluminum plate near samples. A 48 : electrical heater was attached tothe copper block for the study of the recovery of accumulated defects through isochronal annealing after
the cryogenic beam irradiation. The measurement procedure of recovery of defect is as follows: thesample is warmed to the annealing temperature with a heater, and sample temperature holds with constantfor about 10 minutes. After the sample is cooled to 4 K by the GM cryocooler, electrical resistivity of thesample is measured [8-11].
2.2. Estimation of required beam time and heat load
The required beam time for this experiment was estimated from arc-dpa displacement cross sections
calculated by PHITS. The displacement cross section V can be related to the resistivity increase and thebeam fluence:ߪൌଵ οఘೞೌ೘೛೗೐

(1)

஺

(2)

ఘಷು

థ

οߩ௦௔௠௣௟௘ ൌ ௅ οܴ௦௔௠௣௟௘
141- 141 -

JAEA-Conf 2021-001

where UFP is the Frenkel pair resistivity of sample, I is the beam fluence, οߩ௦௔௠௣௟௘ is the electricalresistivity change of sample and οܴ௦௔௠௣௟௘ is the electrical resistance change under the beam irradiation.
Table 2 lists the estimation of the required beam fluence for samples.

Table 2: Estimation of required beam fluence.
Al

Cu

Nb

W

2.36 × 10-26

9.44 × 10-26

1.66 × 10-25

2.9 × 10-25

Frenkel pair resistivity UFP (P:m)

3.7

2.2

14

27

Length of two potential points (mm)

40

37.5

38.5

37.5

Geometry factor (A/L) (m)4.91 × 10-6

5.24 × 10-6

5.10 × 10-6

5.24 × 10-6

Resistance increase οܴ௦௔௠௣௟௘ (P:)

0.4

1.0

10

35

2.25 × 1019

2.52 × 1019

2.19 × 1019

2.34 × 1019

Calculated arc-dpa displacement
cross section V (m2)

Beam fluence I (1/m2)

In Table 2, the arc-dpa displacement cross section V was calculated by PHITS, UFP was obtained from
Ref. [12], and the geometry factor was obtained by the ratio of the area (A) of the cross section of thewire to the length of two potential points (L) of the wire. I was estimated with οܴ௦௔௠௣௟௘ , which is ameasurable value. On the other hands, the proton beam intensity is around 5 × 1011 (protons/minute) andestimated beam area is about 5 × 10-5 (m2) at M03. In this beam condition, the beam fluence on the wire
sample is 1.2 × 1019 (protons/m 2) for 20 hours irradiation, 2.4 × 1019 (protons/m2) for 40 hour irradiation,and 3.6 × 1019 (protons/m2) for 60 hours irradiation, respectively. To obtain the resistance increase listed
in Table 2, approximately 40 hour irradiation is needed.
Since the cold head of the GM cooler has 1.0 W cooling capacity at 4.2 K, we estimated the heatload of beam in the cold head and sample wires using PHITS. The heat load in the cold head was regarded
as a sum of the energy deposition in the cold head, the sample assembly including wire samples and the
1 mm thick aluminum shields as shown in Figure 2. Table 3 lists the heat loads in the wire samples andthe cold head calculated by PHITS.
Table 3: Heat load in wire samples and cold head calculated by PHITS.

Heat load
Wire samples
Cold head

J/proton
4.81 × 10-14
5.68 × 10-13

J/shot2.41 × 10-2
2.84 × 10-1

The beam intensity was estimated to be 5 × 1011 (protons/shot). Since the results are lower than 1 W, thecooling power of the cold head is enough to cool samples during the beam irradiation.

3. Summary
The paper describes the plan to measure displacement cross sections of aluminum, copper, niobium andtungsten with 120-GeV protons at FTBF in FNAL. Experiments will be performed at the M03 beam line142
- 142 -

JAEA-Conf 2021-001

high-rate tracking area. For preparation of experiments, we developed the sample assembly with four
wire sample with 250-Pm diameter. The sample assembly will be maintained at around 4 K by using theGM cryocooler in a vacuum chamber. Then, changes in the electrical resistivity of samples will beobtained under 120-GeV proton irradiation. To obtain the sufficient resistance increase under the beamirradiation, approximately 40 hours is needed for all samples. The cooling power of the cold head isenough to cool samples during the beam irradiation. Recovery of the accumulated defects throughisochronal annealing will also be measured after cryogenic irradiation.

References>@ Sato, T. et al., Features of Particle and Heavy Ion Transport code System (PHITS) version 3.02, J.
Nucl. Sci. Technol., vol.55, 2018, pp.684-690.
>@ Iwamoto, Y. et al., Calculation of displacement cross-sections for structural materials in accelerators
using PHITS event generator and its applications to radiation damage, J. Nucl. Sci. Technol., vol.51,
2013, pp.98-107.
>@ Iwamoto, Y. et al., Estimation of reliable displacements-per-atom based on athermal-recombinationcorrected model in radiation environments at nuclear fission, fusion, and accelerator facilities, J.
Nucl. Mater., vol.538, 2020, 152261.
>@ Mokhov, N.V. and James, C.C., The MARS code system user’s guide, version 15 (2016), Fermilab FN-1058-APC, 2017; https://mars.fnal.gov DFFHVVHG >@ Böhlen. T.T. et al., The FLUKA code: developments and challenges for high energy and medical
applications, Nucl. Data Sheets, vol.120, 2014, pp.211-214.
>@ Norgett, M.J. et al., A proposed method of calculating displacement dose rates, Nucl. Eng. Des.,
vol.33, 1975, pp. 50-54.
>@ Nordlund, K. et al., Primary radiation damage: a review of current understanding and models, J.
Nucl. Mater., vol.512, 2018, pp. 450-479.
>@ Iwamoto, Y. et al., Measurement of the displacement cross-section of copper irradiated with
125 MeV protons at 12 K, J. Nucl. Mater., vol.458, 2015, pp. 369-375.
>@ Iwamoto, Y. et al., Measurement of displacement cross sections of aluminum and copper at 5 K byusing 200 MeV protons, J. Nucl. Mater., vol.508, 2018, pp. 195-202.
>@ Iwamoto, Y. et al., Measurements of displacement cross section of tungsten under 389-MeV proton
irradiation and thermal damage recovery, Materials Science Forum, vol.1024, 2021, pp. 95-101.
>@ Matsuda, H. et al., Measurement of displacement cross-sections of copper and iron for proton with
kinetic energies in the range 0.4 – 3 GeV, J. Nucl. Sci. Technol., vol.57, 2020, pp.1141-1151.
>@ Broeders, C.H.M, and Konobeyev, A.Yu., Defect production efficiency in metals under neutron
irradiation, J. Nucl. Mater., vol.328, 2004, pp. 197-214.

Acknowledgements
The authors wish to express their gratitude to Dr. Adam C. Watts and the staff at FNAL for theirgenerous support. This work is supported by JSPS KAKENHI Grant Number JP19H02652 and performed
under the Radiation Damage In Accelerator Target Environments (RaDIATE) international collaboration.

143- 143 -

JAEA-Conf 2021-001

Comparison of photon spectra emitted from fuel debris using different decay
data libraries
Taichi MATSUMURA*, Keisuke OKUMURA, and Manabu FUJITA
Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy
Agency (JAEA),
790-1 Ootsuka, Motooka, Tomioka-machi, Futaba-gun, Fukushima, 979-1151, Japan
We compared the photon spectra calculated for the fuel debris using three recent decay datalibraries: JENDL/DDF-2015, the decay sub-libraries of ENDF/B-VIII.0 and JEFF-3.3. We found that X-ray
data for 137mBa, γ-ray data for 241Am at 60 keV, and γ-ray data for 106Rh in the energy region 3.0–3.4 MeV
are missing in JENDL/DDF-2015. In addition, we found that the 33 radioactive daughter nuclides are notdefined in the decay chains in JENDL/DDF-2015.
1.Introduction
Evaluated nuclear data has been used for the development of new sensors, non-destructive assay
technologies, and the optimization of radiation shielding in connection with the decommissioning of the
Fukushima Daiichi Nuclear Power Station (1F). We need reliably evaluated nuclear data in order todetermine the radiation characteristics of the fuel debris. However, different collections of evaluatednuclear data give different results, and it has been difficult to clarify the causes of the differences. This isbecause different decay calculation codes deal with so many different nuclides and their decay data in
different numerical solutions and different conditions. To overcome this problem, we have developed areliable new code for calculating the radiation decay and radioactive-source spectra, and it can accurately
treat large amounts of nuclides and all the decay modes in the decay data library.
In this study, we focused on the photon spectrum of the fuel debris, and we investigated thecauses of the differences in the photon spectra calculated by our new code using three evaluated decay datalibraries: JENDL/DDF-2015 [1], the decay sub-libraries of ENDF/B-VIII.0 [2] and JEFF-3.3 [3]. We
expect the results to be reflected in the next JENDL release (e.g., JENDL-5) and to be utilized as reliablenuclear data for Fukushima 1F R&D.
2.Method
In this study, we calculated the X-rays and γ-rays emitted from the Fukushima fuel debris using
JENDL/DDF-2015, ENDF/B-VIII.0, and JEFF-3.3 as follows. As shown in Fig.1, in the first step, we
performed a three-dimensional fuel-inventory calculation, taking into account the burnup and void
distributions in the core of unit-2. We also performed an activation calculation for the structural materials in
the core. Then we mixed all the nuclides so-obtained together to imitate the fuel debris. In the second step,
we calculated the amounts of all the nuclides remaining after the 10 years that have passed since the 1F
144- 144 -

JAEA-Conf 2021-001

accident. We used the Chebyshev rational-approximation method (CRAM), in which the complete
nuclear-transmutation matrix from each decay library can be considered. Finally, we evaluated the photon
spectrum using the photon-emission data from each decay data library. Since the photon spectrum of thefuel debris consists of many line spectra with different energies, for easy comparison we converted thephoton spectrum into the 18-energy-group structure (Table 1) used in the ORIGEN-S code [4].

Figure 1 Method used to calculate the photon spectrum.
Table 1 18-energy-group structure.
Group Energy (MeV)Group

Lower boundary

Upper boundary

Average

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

8.00E+00
6.50E+00
5.00E+00
4.00E+00
3.00E+00
2.50E+00
2.00E+00
1.66E+00
1.33E+00
1.00E+00
8.00E-01
6.00E-01
4.00E-01
3.00E-01
2.00E-01
1.00E-01
5.00E-02
1.00E-02

1.00E+01
8.00E+00
6.50E+00
5.00E+00
4.00E+00
3.00E+00
2.50E+00
2.00E+00
1.66E+00
1.33E+00
1.00E+00
8.00E-01
6.00E-01
4.00E-01
3.00E-01
2.00E-01
1.00E-01
5.00E-02

9.00E+00
7.25E+00
5.75E+00
4.50E+00
3.50E+00
2.75E+00
2.25E+00
1.83E+00
1.50E+00
1.17E+00
9.00E-01
7.00E-01
5.00E-01
3.50E-01
2.50E-01
1.50E-01
7.50E-02
3.00E-02

145- 145 -

JAEA-Conf 2021-001

3. Results
We compared the 18-energy-group photon spectra obtained by using decay data fromJENDL/DDF-2015, ENDF/B-VIII.0, and JEFF-3.3. The results are compared in Fig. 2. The ratio of
JENDL/DDF-2015 to ENDF/B-VIII.0 is 93% over the total energy range, and the actual shape of theenergy spectrum is important for purposes like the development of detectors or radiation shielding. In theenergy regions where there are differences, we confirmed the differences in the photon intensities of the
decay data library by each nuclide. We extracted nuclides that do not emit X-rays or γ-rays or those forwhich the intensity is smaller compared with other libraries, especially those that have a strong influence on
photon intensities in the 18-energy-group structure.

Intensity [photons/s/core]

1.E+181.E+16

1.E+14

1.E+12

ENDF/B-VIII.0
JENDL/DDF-2015
JEFF-3.3

1.E+10

0.01

0.10

1.00

10.00

Energy [MeV]

Figure 2 The different photon spectra obtained using recent decay data libraries for the Fukushima fueldebris 10 years after the 1F accident (using core-averaged values for unit-2 in 2021, for which there
was no volatile fission-product release).
In the energy region from 10–50 keV, X-rays from 137mBa are not defined in JENDL/DDF-2015 andare therefore underestimated. Figure 3 shows the photon intensities of the 137mBa line spectra evaluatedfrom JENDL/DDF-2015 and ENDF/B-VIII.0. In JENDL/DDF-2015, the X-ray intensities are defined formost of nuclides, but not for 137mBa. Although the half-life of 137mBa is short (about 2.6 min.), the X-rays
from 137mBa are not negligible because this (nuclear) state is produced by the β- decay of a large amount ofCs, which has a half-life of about 30 years.

137

146
- 146 -

2.E+172.E+172.E+172.E+17

Intensity[n/s/core]

Intensity[n/s/core]

JAEA-Conf 2021-001

1.E+178.E+16
4.E+16
0.E+000.01

1.E+178.E+16
4.E+16

0.10

Energy [MeV]

1.00

0.E+00
0.01

10.00

0.10

Energy [MeV]

1.00

10.00

Figure 3 Photon spectra of 137mBa using ENDF/B-VIII.0 (left) and JENDL/DDF-2015 (right)
In the energy region from 50–100 keV, JENDL/DDF-2015 underestimates the γ-rays from 241Am
because they are not defined in this library. Figure 4 shows the 241Am line spectra from JENDL/DDF-2015
and ENDF/B-VIII.0. The famous γ-ray line at 59.5 keV is defined in ENDF/B-VIII.0, but not in
JENDL/DDF-2015. In addition, photons with strong intensities are observed at lower energies only in

1.E+15

1.E+15

1.E+15

1.E+15

1.E+15

1.E+15Intensity[n/s/core]

Intensity[n/s/core]

ENDF/B-VIII.0.

8.E+14
6.E+14

4.E+142.E+140.E+000.01

8.E+14
6.E+14
4.E+142.E+14

0.10

Energy [MeV]

1.00

0.E+00
0.01

10.00

0.10

Energy [MeV]

1.00

10.00

Figure 4 Photon spectra of 241Am using ENDF/B-VIII.0 (left) and JENDL/DDF-2015 (right).
In the energy region from 3–3.4 MeV, JENDL/DDF-2015 underestimates the γ-rays from 106Rh,
because the γ-ray production is smaller in this energy region than is that obtained from ENDF/B-VIII.0.
Figure 5 shows the line spectra of photons above 1 MeV for 106Rh from JENDL/DDF-2015 and from
ENDF/B-VIII.0.

While

ENDF/B-VIII.0

defines

multiplephotonintensities

above

3

MeV,

JENDL/DDF-2015 defines only one photon intensity above 3 MeV. Although the photons from 106Rh may
be negligible in the fuel debris considered in this study, it is usually important as a photon source from theβ- decay of 106Ru, which has a half-life of 1.0 y, and the 106Rh is in radiation equilibrium.

147- 147 -

3.E+09

3.E+093.E+093.E+09Intensity[n/s/core]

Intensity[n/s/core]

JAEA-Conf 2021-001

2.E+092.E+09
1.E+092.E+09
1.E+095.E+085.E+080.E+001.00

2.E+09

1.50

2.00

2.50
3.00
Energy [MeV]

3.50

0.E+00
1.00

4.00

1.50

2.00

2.50
3.00
Energy [MeV]

3.50

4.00

Figure 5 Photon spectra of 106Rh using ENDF/B-VIII.0 (left) and JENDL/DDF-2015 (right).
Bycomparingthe

10-year-elapsed

photonspectraobtainedusing

JENDL/DDF-2015,

ENDF/B-VIII.0, and JEFF-3.3, we conclude that 137mBa, 241Am, and 106Rh are the main causes of thedifferences in the overall photon spectrum from JENDL/DDF-2015. To confirm this, we replaced the decay
data for these three nuclides in JENDL/DDF-2015 with those from ENDF/B-VIII.0. The 18-energy-group
spectrum obtained with the modified JENDL/DDF-2015 then agreed with those obtained using
ENDF/B-VIII and JEFF-3.3, as shown in Fig. 6. The differences in the energy-integrated photon intensities
became smaller, and the ratio of the modified JENDL/DDF-2015 to ENDF/B-VIII.0 improved to 99%.

Intensity [photons/s/core]

1.E+181.E+16

1.E+14

ENDF/B-VIII.0
JENDL/DDF-2015
JEFF-3.3

1.E+12

1.E+10

0.01

0.10

1.00

10.00

Energy [MeV]

Figure 6 Modified photon spectrum.
Unlisted daughter nuclides also exist in JENDL/DDF-2015. Table 2 shows the nuclides for which theparent nuclide is defined in JENDL/DDF-2015 but the daughter nuclide is not defined, together with theirmain production paths. Therefore, the decay chain breaks off. For example, the α-decay of 239Pu (T1/2㸻
2.4×104 y) is expressed as 239Pu Ѝ 235mU + α, but 235mU does not exist in this library. As a result, theamount of 235U and its daughter nuclides will be underestimated by about 20% after a long decay time suchas 1000 years, because the immediate decays from 235mU to 235U are not counted. We found 33 nuclides forwhich the daughter nuclides are not defined.
148- 148 -

JAEA-Conf 2021-001

Table 2 The unlisted daughter nuclides.

4. Conclusion
We need reliable nuclear data to evaluate the radiation characteristics of fuel debris appropriately
for the purpose of developing new sensors and non-destructive assay technologies and for optimizing
radiation shielding for use in decommissioning. This research revealed the following main points. We
found that X-ray data for 137mBa, γ-ray data for 241Am at 60 keV, and γ-ray data for 106Rh in the range 3.0–
3.4 MeV are missing from JENDL/DDF-2015. In addition, in JENDL/DDF-2015 we found that the 33
daughter nuclides are not defined. We anticipate that these problems will be corrected in the next JENDL
release.
5. References>@ J. Katakura and F. Minato “JENDL Decay Data File 2015, JAEA-Data/Code 2015-030 (2016).
>@ D.A. Brown, et al., ENDF/B-VIII.0: the 8th major release of the nuclear reaction data library with
CIELO-project cross sections, new standards and thermal scattering data. Nucl. Data Sheets, 148. 1-42
(2018).
>@ OECD/NEA Data Bank, JEFF-3.3, https://www.oecd-nea.org/dbdata/jeff/jeff33/index.html (2017).
>@ I. C. Gauld, O. W. Hermann, R. M. Westfall, Origen-S: Scale system module to calculate fuel depletion,
Actinide transmutation, fission product buildup and decay, and associated radiation source terms, Vol. II
(2009).

149- 149 -

JAEA-Conf 2021-001

 &YQFSJNFOUBM QSPHSBN PG OVDMFBS EBUB GPS
BDDFMFSBUPSESJWFO OVDMFBS USBOTNVUBUJPO TZTUFNVTJOH''"(BDDFMFSBUPS¦'JSTUTVCQSPHSBNTQBMMBUJPO OFVUSPO NFBTVSFNFOU,FJUB/","/0p )JSPLJ*8".050  4IJOJDIJSP.&*(0 ,BUTVIJTB/*4)*0 :PTIJIJSP*4)* ,FOUBSP)*304& :PTVLF*8".050 :BTVUPTIJ,63*:"." 'VKJP."&,"8" )JSPZVLJ.",** ,PUB0,"#& 3JDDBSEP03-"/%*
"LJUP0*;6.* %BJLJ4"50) 'VNJ46;",* ,B[VBLJ546,"%"
5PNPOPSJ6&46(* )JSPTIJ:"4)*." BOE:PTIJIBSV.03*+1"3$ $FOUFS +BQBO"UPNJD&OFSHZ"HFODZ 5PLBJNVSB *CBSBLJ +BQBO/VDMFBS4DJFODFBOE&OHJOFFSJOH$FOUFS +BQBO"UPNJD&OFSHZ"HFODZ 5PLBJNVSB *CBSBLJ +BQBO
"EWBODFE4DJFODF3FTFBSDI$FOUFS +BQBO"UPNJD&OFSHZ"HFODZ 5PLBJNVSB
*CBSBLJ +BQBO*OTUJUVUFGPS*OUFHSBUFE3BEJBUJPOBOE/VDMFBS4DJFODF ,ZPUP6OJWFSTJUZ ,VNBUPSJDIP 0TBLB +BQBOp&NBJM OBLBOPLFJUB!KBFBHPKQ"CTUSBDU
For accurate prediction of neutronic characteristics for accelerator-driven nuclear transmutation system (ADS) and a source term of spallation neutrons for reactor physics experiments for the ADS at Kyoto University Critical Assembly (KUCA), we have launched anexperimental program to measure nuclear data on ADS using the Fixed Field Alternating
Gradient (FFAG) accelerator at Kyoto University (Period: October 2019 – March 2023).
This program consists of two subprograms, focusing on two nuclear reaction mechanisms,(1) spallation reactions and (2) high-energy ﬁssion, for incident proton energies from several tens of MeV to 100 MeV. In the ﬁrst subprogram, we will measure double-diﬀerential
cross-sections (DDXs) and thick-target neutron-yields (TTNYs) for several targets (i.e., Pb,
Bi, and Fe); in the second subprogram, mass distribution of ﬁssion product and neutron
multiplicity in high energy ﬁssion of Pb and Bi will be measured. In this paper, the present
status of the ﬁrst subprogram is described.

1

Introduction

Accelerator-driven nuclear transmutation systems (ADSs) have attracted attention as one ofthe promising options to solve the nuclear issue of high-level radioactive waste management [1].
In terms of the neutronic design of the ADS, precise experimental nuclear data and reliable
theoretical nuclear models are required. So far, much eﬀort has been devoted to measure nuclear
data at incident proton energies from several hundred MeV to GeV range, and these experimental
nuclear data play a signiﬁcant role in the improvement of the nuclear models. However, it has
been pointed out that lack of nuclear data in the energy range from several tens of MeV to150- 150 -

JAEA-Conf 2021-001

Proton beam

NE213
TargetChamber

5m

Figure 1: Schematic drawing of a vacuum chamber and neutron detectors.
100 MeV makes it diﬃcult to improve the nuclear models, which results in large uncertainty inthe neutronic characteristics of the ADS. Satoh et al. demonstrated that recent nuclear models
such as the Liège Intranuclear Cascade model [2] failed to predict the measured spectra ofemitted neutrons in the most-forward direction at the incident proton energy below 78 MeV [3].
Therefore, accumulation of experimental data on important nuclides in ADS such as neutron
production cross sections in proton-induced reactions at incident energies from several tens of
MeV to 100 MeV and mass distribution of ﬁssion product and neutron multiplicity from highenergy ﬁssion are strongly desired.
In this circumstance, a new experimental campaign has been launched to measure nuclear
data related to ADS. The campaign consists of two subprograms: measurement of neutronenergy spectra from spallation reactions of Fe, Pb, and Bi by protons from several tens of MeV
to 100 MeV and that of mass distribution of ﬁssion product and ﬁssion multiplicity in high energy
ﬁssion of Pb and Bi. For the ﬁrst subprogram, the Double-Diﬀerential neutron production crosssections (DDXs) and Thick-Target Neutron Yields (TTNYs) for such materials will be measured
using a proton beam accelerated by Fixed Field Alternating Gradient (FFAG) accelerator at
Kyoto University. In this paper, the experimental plan of the ﬁrst subprogram and a detector
test performed for the experiment are described.

2

Plan of Experiment at FFAG Facility

The experiment of the ﬁrst subprogram will be conducted at FFAG Facility, Kyoto University. In
this experiment, proton-induced DDXs and TTNYs for Fe, Pb, and Bi targets will be measured
using the time-of-ﬂight method. Also, sensitivity check of a 237 Np ﬁssion chamber under the
spallation neutron ﬁeld will be investigated. Figure 1 shows a photo of the FFAG facility anda schematic drawing of a vacuum chamber and neutron detectors. One of the targets is placedat the center of the chamber. Target thicknesses for the DDX experiment are 2 mm for all
targets to achieve enough statistics, and those for the TTNY experiment are 30 mm for the Fe151- 151 -

JAEA-Conf 2021-001

Detector

Shadow bar

Beam port

Figure 2: Conﬁguration of the measurement geometry at FRS.
and Pb targets and 35 mm for the Bi target, which are designed so that 150-MeV protons stopin the targets. The range of incident protons was calculated by SRIM code [4]. Diameters of
the targets for both the DDX and TTNY experiments are 48 mm which is larger than beam
size of 40 mm calculated by beam optics. An NE213 liquid organic scintillator (size: 20 mm
in length and 8 mm in diameter) coupled with a photomultiplier tube (H3164, Hamamatsu
Photonics) will be placed 5 m far from the target to detect neutrons. Signals from the detector
will be fed to a digitizer (SIS3316). Current of the proton beam is planed to be 0.1 nA for the
TTNY measurement and 1 nA for the DDX measurement. To eliminate contribution of roomback neutrons to the DDX and TTNY experiments, room-back neutron measurements will also
be conducted with a shadow bar made of stainless steel (size: 1 m in length and 50 mm indiameter), whose length is designed to reduce the neutrons produced from the targets to several
percent. Measurements at several emission angles will be conducted by changing the position of
the detector. The 237 Np ﬁssion chamber (size: 25.4 mm in length and 6 mm in diameter) will
be used to check the reaction rate under the spallation neutron ﬁeld around the target vacuum
chamber. The activity of coated 237 Np is 31.3 kBq on June 30, 1982.

3

Detector test at Facility of Radiation Standard

In advance of the experiment at the FFAG facility, measurement of neutron detection eﬃciency
for the neutron detector (NE213 + H3164) and response of the 237 Np ﬁssion chamber wereconducted at Facility of Radiation Standard (FRS) [5], Japan Atomic Energy Agency (JAEA).
In this experiment, 14.8 MeV monoenergetic neutrons generated by T(d, n) reaction was used.
The RF repetition frequency was 4 MHz. Figure 2 shows a photo of the measurement geometry.
Neutrons generated at a production target directly irradiated to the neutron detectors suchas the NE213 and the 237 Np ﬁssion chamber placed at approximately 1 m downstream to thebeam port at 60 degree from the most-forward direction. The measurement with a shadow bar
was also performed in the NE213 measurement to estimate background neutrons. Scintillation
photons produced in the NE213 were converted to electric pulses by the photomultiplier tube
and fed to the digitizer after passing through a 40 meter-long low-attenuation cable. To determine the time-of-ﬂight, RF signals of the accelerator were used as start timing and the signals
from NE213 as stop timing. The 237 Np ﬁssion chamber was connected to a preampliﬁer and a152- 152 -

70000103

60000

Charge [ch]Charge [ch]JAEA-Conf 2021-001

50000

60000
50000

2

10

40000
30000

102

40000
30000

10

20000
10000
0
− 50

70000

10
20000
10000

0

50

100

150

200

250

300

350

1

Time-of-Flight [ns]

0
− 50

0

50

100

150

200

250

300

350

1

Time-of-Flight [ns]Figure 3: Two-dimensional plot of the obtained signal by the time-of-ﬂight and the charge
spectrum for the NE213 before (Left) and after (Right) the gamma-ray elimination.
spectroscopy ampliﬁer. Then signals from the spectroscopy ampliﬁer were fed to the digitizer
and a multichannel analyzer.

4

Results and Discussion

4.1

Result for NE213 Detector

Figure 3 shows two-dimensional plot by the time-of-ﬂight and the charge spectrum for the NE213
neutron detector. Three peaks at approximately 15, 30, and 50 ns can be seen, which correspondto prompt gamma-rays, 14.8-MeV neutrons, and 3.0-MeV parasitic neutrons, respectively. The
parasitic neutrons were produced by the D(d, n) reactions between incident deuteron beamand deuterium accumulated in the tritium target. The neutron energies were estimated fromthe ﬂight length and the diﬀerence of time-of-ﬂight between the prompt gamma-rays and theneutrons. The gamma-ray events were rejected by the two-gate method of the pulse shapeanalysis. After eliminating the gamma-ray events, the number of detected 14.8-MeV neutrons
is estimated with paying attention to the parasitic neutrons. The detection eﬃciency of theNE213 neutron detector was calculated from the neutron ﬂuence measured by a reference longcounter consists of a thermal neutron detector and a polyethylene moderator and the obtained
counts by the NE213 neutron detector. The uncertainty of the neutron ﬂuence measured by thelong counter was 6%. Figure 4 shows the detection eﬃciency of the NE213 neutron detector
as a function of the neutron energy. The black circles correspond to the 241 Am-quarter and
137 Cs-double biased eﬃciencies measured in the present experiment. Here the 241 Am-quarter
biased eﬃciency means to neutron detection eﬃciency with larger light output than quarter of
59-keV electron equivalent (keVee) which corresponds to a photo peak of 59-keV γ-ray from
241 Am. Also the 137 Cs-double biased eﬃciency corresponds to that with larger output than
986 keVee [6]. The black square is the 241 Am-quarter biased eﬃciency measured in the previous
experiment at lower neutron energy [7]. The solid and dashed lines are calculated eﬃciencies
by SCINFUL-R [8, 9] code in each bias. The calculations almost reproduce the obtained data.
However, small diﬀerence can be seen in the 241 Am-quarter biased eﬃciency. It is consideredthat the parasitic neutrons is not completely removed in the time-of-ﬂight spectrum. Time153
- 153 -

JAEA-Conf 2021-001

Figure 4: Detection eﬃciency of NE213 as a function of neutron energy [7].
resolution of the time-of-ﬂight is approximately 4 ns which is originated from the inner clock of
the digitizer, the pulse width of incident deuteron beam, and the ﬂight path length.

4.2

Result for 237 Np ﬁssion chamber

Figure 5 shows charge distribution from the 237 Np ﬁssion chamber. The large number of low
charge events and several high charge events are seen. The former is signals induced by αdecay of 237 Np nuclei and the latter are ﬁssion events of them. The ﬁssion events are clearly
separated from the α-decay component by their much larger deposit energy. We assume thatthe events with charge larger than 4.5 × 104 channel are ﬁssion events. The counts per ﬂuenceis estimated to be 9.0±2.5 counts/(n/cm2 ). We also derive the calculated one from ﬁssion crosssection of 237 Np at 14.8-MeV neutron and the number of 237 Np nuclei calculated by the activityof deposited 237 Np. The calculated one is 6.8 counts/(n/cm2 ), which agrees with the measured
one within 1σ of the statistical error. However, the statistics is little bit poor to check theconsistency between the measured count rate and the calculated one. Also, the contributionof the parasitic neutron as seen in the time-of-ﬂight spectrum measured by the NE213 should
be considered carefully because 237 Np has a comparable ﬁssion cross section at 3-MeV neutronenergy to 14.8-MeV neutron.

5

Summary

For the development and design of ADS, more nuclear data measurements are desired especiallythe proton incident energy ranging from several tens of MeV to 100 MeV. In this situation,
new experimental campaign has been launched to measure the TTNYs and the DDXs at FFAG
facility, Kyoto University, and mass distribution of ﬁssion product and neutron multiplicity inhigh energy ﬁssion. At present, design of the measurement and detector tests are in progress.
In advance of the experiment at FFAG, the detectors planned to be used in FFAG facility
were tested with 14.8-MeV monoenergetic neutron at FRS, JAEA. The detection eﬃciency ofNE213 liquid organic scintillator shows good agreement with calculation by SCINFUL-R. Also,
count rate of 237 Np ﬁssion chamber under the 14.8-MeV neutron ﬁeld was consistent with thecalculated value from the activity of deposited 237 Np. From these measurements, the detector154- 154 -

Counts [-]JAEA-Conf 2021-001

10

4

10

3

10

2

10

1
0

20

40

60

80

100

120

×10

3

Charge [ch]Figure 5: The measured charge distribution from 237 Np ﬁssion chamber.
test and response check have been done and tuning towards the FFAG experiment will be
conducted.

References[1] Tsujimoto K, Oigawa H, Ouchi N, et al. Research and Development Program on Accelerator
Driven Subcritical System in JAEA. J Nucl Sci Technol. 2007;44(3):483-490.
[2] Boudard A, Cugnon J, David JC, et al. New potentialities of the Liège intranuclear cascade model for reactions induced by nucleons and light charged particles. Phys Rev C.
2013;87:014606.
[3] Satoh D, Iwamoto Y, Ogawa T. Measurement of neutron-production double-diﬀerential
cross sections of nat C, 27 Al, nat Fe, and nat Pb by 20, 34, 48, 63, and 78 MeV protons in the
most-forward direction. Nucl Instrum Meth A. 2019;920:22-36.
[4] Ziegler JF, Ziegler MD, Biersack JP. SRIM - The stopping and range of ions in matter(2010). Nucl Instrum Meth B. 2010;268(11):1818-1823.
[5] Tanimura Y, Fujii K, Tsutsumi M, et al. Neutron ﬂuence monitoring system in monoenergetic neutron ﬁelds at FRS/JAEA. Prog Nucl Sci Technol. 2014;4:388-391.
[6] Dietze G and Klein H. Gamma-calibration of NE 213 scintillation counters. Nucl Instrum
Meth. 1982;193(3):549-556.
[7] Matsuda H, Iwamoto H, Meigo S, et al. Measurement of thick target neutron yield at 180°
for a mercury target induced by 3-GeV protons. Nucl Instrum Meth B. 2020;483:33-40.
[8] Dickens JK. SCINFUL: A Monte Carlo Based Computer Program to Determine a Scintillator Full Energy Response to Neutron Detection for En Between 0.1 and 80 MeV: User’s
manual and FORTRAN program listing. Oak Ridge National Lab TN (USA); 1988.
[9] Meigo S. Measurements of the response function and the detection eﬃciency of an NE213
scintillator for neutrons between 20 and 65 MeV. Nucl Instrum Meth A. 1997;401:365–378.

Acknowledgments
This work was supported by MEXT Innovative Nuclear Research and Development Program
Grant Number JPMXD0219214562.
155- 155 -

JAEA-Conf 2021-001

 Neutron Filtering System for Fast Neutron
Cross-section Measurement at ANNRI
Gerard ROVIRA†1 , Osamu IWAMOTO1 ,Atsushi KIMURA1 ,Shoji NAKAMURA1 ,Nobuyuki IWAMOTO1 , Shunsuke ENDO1 ,Tatsuya KATABUCHI2 ,Kazushi
TERADA∗2 ,Yu KODAMA2 , Hideto NAKANO2 , Jun-ichi HORI3 , andYuji
SHIBAHARA3
1

Nuclear Data Center, Japan Atomic Energy Agency
Laboratory for Advanced Nuclear Energy, Tokyo Institute of Technology
3
Institute for Integrated Radiation and Nuclear Science, Kyoto University†
Email: gerard.rovira@jaea.go.jp
2

Abstract
The double-bunch pattern of the J-PARC facility introduces serious ambiguities in theneutron-induced cross-section measurement for fast neutrons. The neutron ﬁltering technique
is implemented in the ANNRI beamline in order to produce quasi-monoenergetic neutron
peaks. Diﬀerent ﬁlter conﬁgurations with Fe and Si were tested by means of capture andtransmission experiments and with Monte-Carlo simulations using the PHITS code. In thiswork, the characteristics of the neutron ﬁltering system using Fe and Si are presented together
with a preliminary cross-section results for the 197 Au neutron capture cross-section.

1

Introduction

The double-bunch mode is employed in the Japanese Proton Accelerator Research Complex(J-PARC) in which two 0.1 μs-wide proton bunches are shot into a spallation target with a time
diﬀerence of 0.6 μs at a repetition rate of 25Hz. This mode is intended to increase the thermal
neutron beam intensity as, for that energy, the doublet structure of the neutron beam is negligible due to Doppler broadening and moderation time. Nonetheless, for fast neutrons experimentsin the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline, thistime diﬀerence is no longer trivial. Fast neutrons reach the target position within 10 μs and the0.6 μs time diﬀerence becomes a signiﬁcant source of ambiguities in the cross-section measurements. Neutrons detected with a certain time-of-ﬂight (TOF) can have two diﬀerent energies
as it is impossible to ascertain the originating proton bunch. For example, for the case of 100
keV neutrons, the expected TOF for the NaI(Tl) spectrometer target position is about 6.4 μs.
However, at 6.4 μs, neutrons with an energy of 120 keV coming from the delayed proton shot
can also be detected. In this work, we propose a solution to bypass the double bunch structureof ANNRI using a neutron ﬁltering system. The characteristics and performance of the neutron
ﬁltering system implemented at ANNRI are presented in this paper. The ﬁltering system wasanalyzed using both experimental analysis and Monte-Carlo simulations.
∗

Present address: Institute for Integrated Radiation and Nuclear Science, Kyoto University

156- 156 -

JAEA-Conf 2021-001

2

Neutron Filtering System

A neutron ﬁltering system has been designed at the ANNRI beamline in order to circumventthe double-timed structure of the neutron beam within the ”Study on accuracy improvement of
fast-neutron capture reaction data of long-lived MAs for development of nuclear transmutation
systems” project [1]. Using the neutron ﬁltering tecnique, the incident white neutron ﬂux canbe tailored into quasi-monoenergetic peaks using materials that present a sharp minimum inthe neutron total cross-section [2]. Several cylinders of nat Fe and nat Si were used in diﬀerent
conﬁgurations and expected to create quasi-monoenergetic ﬁltered neutron peaks with energiesof 24 keV (Fe) and 54 and 144 keV (Si).

3Experimental Analysis

3.1

Neutron Filtering Setup

The neutron total cross-section for nat Fe and nat Si can be seen in ﬁgure 1(a). Neutron ﬁlteredpeaks are expected with energies of 24, 54 and 144 keV. Three diﬀerent ﬁlter assemblies consistingof 20 cm of Fe and 20 and 30 cm of Si were implemented in the rotary collimator of the ANNRI
beamline (see Fig. 1(b)).

102

nat

Fe(n,tot)

nat

Cross section [b]Si(n,tot)

1

10

100
10−1
24 keV Fe
10−2

10

54 keV Si

144 keV Si

100
Energy [keV]

500

(a)

(b)

Figure 1: (a)Neutron total cross-section of nat Fe and nat Si. (b) Schematic view of the ANNRI
beamline. The neutron ﬁlter material was introduced in the rotary collimator.

3.2

Neutron Capture Experiments

The NaI(Tl) spectrometer of the ANNRI beamline was employed to determine the ﬁltered incident neutron ﬂux [3]. The samples were situated at a neutron ﬂight path of 27.9 m. A boron
sample with a 10 mm diameter and thickess of 0.5 mm and a Au sample with a 10 mm diameterand 1 mm thickness were used in the experiments. The incident neutron ﬂux was determined bymeasuring the 478 kev γ-rays from the 10 B(n,αγ)7 Li reaction. The Au sample measurement wasused to normalize the incident neutron ﬂux derived from the boron sample measurement at theenergy point of the ﬁrst resonance (4.9 eV) since it was completely saturated. More information
about the experimental analysis can be found here [4].

157
- 157 -

JAEA-Conf 2021-001

3.3

Transmission Experiments

The incident neutron ﬂux was also measured in transmission experiment using two types of Liglass detectors. A Li-glass detectors enriched with 6 Li (GS20) and a Li-glass detector enrichedwith 7 Li (GS30) were simultaniously employed in the experiments. The detectors were situatedat a ﬂight-path of 28.6 m having the 7 Li enriched detector in the upstream position. The
GS20 detector is used to detect the incident neutrons via the 6 Li(n,α)4 He reaction whereas
GS30 detector is employed to estimate the background due to γ-rays. Further details on thetransmission analysis are provided there [5].

3.4Experimental Results

The results obtained from both experimental techniques provide very good agreement and areable to show the ﬁltering performance of the neutron ﬁltering system. The results for the Fe
ﬁlter array of 20 cm is provided is Fig. 2.

Counts [1/proton shot/100 ns]

The ﬁltered neutron peak of 24 keV is clearly
isolatedfor both capture and transmission exper20
Captureiments in one double-humped peak that includes
Transmission
overlapped neutrons from both proton bunches.
15
Other ﬁltered peaks can also be seen between 7
24 keV10
and 9 μs but the counting rate seems to be too
small to be used in experiments. The results for5
the two diﬀerent Si ﬁlter assemblies can be seen in
Fig. 3(a) for 20 cm of Si and in Fig. 3(b) for 30 cm
0
4
6
8
10
12
14
16
18
20
of Si. As is the case for the Fe array, both captureTime at the Detector Position [μs]and transmission experiments present high agreeFigure 2: Filtered neutron ﬂux by 20 cm of ment for both ﬁltered peaks of 144 and 54 keV.
Fe obtained from capture (black) and trans- Here the contributions from each proton bunch areclearer as these peaks occur at a higher energy. The
mission (red) experiments.
diﬀerence in time between the results from both detectors is due to the fact that that the detectors are installed at diﬀerent positions with respect
to the incident neutron beam (see Fig. 1(b)). The NaI(Tl) spectrometer is situated at a distaceof 27.9 m from the moderator surface whereas the Li-glass detectors are situated at a slightly
longer distance of 28.6 m.
CaptureTransmission
144 keV60

40

CaptureTransmission

80
Counts [1/proton shot/100 ns]

Counts [1/proton shot/100 ns]

80

54 keV20

0

144 keV60

40
54 keV
20

0
2

4

6

8

10

12

14

16

18

20

2

Time at the Detector Position [μs]

4

6

8

10

12

14

16

Time at the Detector Position [μs]

(a)

(b)

Figure 3: Filtered neutron ﬂux by 20 cm of Si (a) and 30 cm of Si (b) determined from capture(black) and transmission (red) experiments

158- 158 -

JAEA-Conf 2021-001

4

PHITS Simulations

Monte-Carlo simulations with the code PHITS [6] were employed as benchmark for the ﬁlteringsystem performance analysis. Since the straight relationship between time and energy for thedetected neutrons is no longer applicable for fast neutrons due to the double-bunch structure,
simulations with PHITS are used the neutron transmition ratio through all the materials, including not only the ﬁlter materials but also structural materials, in the ANNRI beamline. The
neutron transmitted ratios were then unfolded taking into account the time structure of the
ANNRI beamline as was described by Kino et al [7] using the model function suggested by
Ikeda and Carpenter [8].

Counts [1/proton shot/100 ns]

100

TOF gate 24 keV
PHITS - No Filter
PHITS - Fe 20 cm Filter
Capture - No Filter
Capture - Fe 20 cm

50

0
4

6

8

10

12
Time [μs]

14

16

18

20

(a)
200
Counts [1/proton shot/100 ns]

The derived time distribution results from the PHITS simulations
can be seen in Fig.
4(a) and4(b) for the 20 cm Fe and 20 cm
Si ﬁlter arrays, respectively, compared with the results with no ﬁlter present. The PHITS results
are also compared with the experimental results obtained from thecapture experiments. The MonteCarlo simulations are able to accurately reproduce the experimental results with both ﬁlter assemblies and when no ﬁlter material is used.
Hence, the energy distribution obtained from the
PHITS simulations is deemed reliable.

TOF gate 144 keV
TOF gate 54 keV
PHITS - No Filter
PHITS - Si 20 cm
Capture - No Filter
Capture - Si 20 cm

150

In order to analyze the neutronenergy distribution derived with
100
PHITS at the ﬁltered peaks, TOF
gated were created enclosing thethree ﬁltered neutron peaks. For the50
Fe ﬁlter array, a TOF gate was created from 12.6 to 14.6 μs to wrap the
0
4
6
8
10
12
14
16
18
20
24 keV ﬁltered neutron beam. ThisTime [μs]gate is shown in Fig. 4(a). From thegated TOF data, a centroid energy(b)of 23.6 keV was determined for the
Fe 24 keV window. On the other Figure 4: Time distribution of the PHITS results andhand, the neutron energy distribu- {aptureexperimentsusinga20cmFeﬁlter(a)anda20cm
tuon of the ﬁlered peaks of 144 keV Si ﬁlter (b) compared with the results when no ﬁlter isand 54 keV were derived using TOF present.
gates from 5.4 to 6.4 μs and from 8.6
to 9.8 μs, respectively. For the Si array, centroid peaks of 127.7 and 51.5 keV were derived from the PHITS results. The result of
127.7 keV is much lower than the expected value of about 144 keV. The reason for this is that159
- 159 -

JAEA-Conf 2021-001

the peak is shifted to a lower energy due to the presence of 27 Al in the beamline which has aresonance peak at the energy around 150 keV in the neutron total cross-section. Neutrons withenergies from 135 to 160 keV are scattered by the several layers of 27 Al present at ANNRI used
to compartimentalize the beamline and cannot reach the experimental areas.

5

Cross-section results

Preliminary results of the 197 Au neutron capture cross-section were derived as the ﬁnal step toevaluate the perfomance of the neutron ﬁlter and their viability for neutron-induced reaction
measurement. The Au cross-section was derived from the obtained Au capture yield using thePulse-Height Weighting Technique (PHWT) [9] at each TOF gate (Gi ) using the following:σAu (Gi ) =YAu (Gi )C(Gi ) 1
φn (Gi )nAu(1)being σAu (Gi ) the absolute cross-section for each of the three TOF gates (Gi ); YAu (Gi ) andC(Gi ) are the Au neutron capture yield and the coeﬁcient to correct for the self-shielding andmultiple-scattering eﬀects for each TOF gate (Gi ), respectively. φn (Gi ) means the normalized incident neutron ﬂux at the TOF gate (Gi ) and nAu stands for the sample area density in at/barn.
The preliminary results for the 197 Au neutron capture cross-section are shown in Fig. 5.
The results are compared with the JENDL-4.0 evaluated data [10] and the IAEA standard
library[11]. The x-axis bar are the mininum and maximun neutron energy determined at each
TOF gate by PHITS.

1

Cross section [b]JENDL-4.0 - 197Au(n, γ)
197
IAEA Standard Au(n, γ)
Capture Filter Experiments

0.1

10

100
Neutron Energy [keV]

Figure 5: Preliminary results for the 197 Au neutron capture cross section using the ANNRI
ﬁltering system
The present preliminary results agree within uncertainties with the evaluated data fromJENDL-4.0 and present slightly lower values than those included in the IAEA standard library.
160- 160 -

JAEA-Conf 2021-001

6

Conclusions

The neutron ﬁltering system applied in the ANNRI beamline is able to tailor the incident neutron
ﬂux into quasi-monoenergetic neutron peaks. The ﬁlter conﬁgurations of 20 cm of Fe and 20
cm of Si have proven to be a feasible solution in order to circumvent the double-bunch structure
for fast neutron cross-section measurements. Using experiments and simulations with PHITS,
the characteristics of the three peaks molded by the Fe and Si assemblies were determinedwith centroid energies of 23.6 keV (Fe) and 51.5 and 127.7 keV (Si). Furthermore, a preliminary
cross-section measurement of the 197 Au neutron capture cross-section using the neutron ﬁlteringsystem was performed. The present results agree within uncertainties with the evaluated datafrom JENDL-4.0.

References[1] Katabuchi T, Iwamoto O, Hori J, Kimura A, et al. Fast neutron capture reaction datameasurement of minor actinides for development of nuclear transmutation systems. EPJ
Web of Conferences, 2020;239.
[2] Greenwood RC, Chrien RE. Filtered reactor beams for fast neutron capture γ-ray experiments. Nucl. Inst. and Meth., 1976;138:125-143.
[3] Katabuchi T, Igashira M, Matsuhasi M, Mizumoto M, et al. Nuclear data measurement
usingtheaccurateneutron-nucleusreactionmeasurementinstrument(ANNRI)intheJapan
Proton Accelerator Research Complex (J-PARC), IAEA-TECDOC, 2014.
[4] Rovira G, Katabuchi T, Tosaka K, Matsuura S, et al. Neutron capture cross-section andresolved resonance analysis of 237 Np. J. Nucl. Sci. Technol. 2020;57:24-39.
[5] Terada K, Kimura A, Nakao T, Nakamura S, et al. Measurements of neutron total andcapture cross section of 241 Am with ANNRI at J-PARC. J. Nucl. Sci. Technol. 2018;55:11981211.
[6] Sato T, Iwamoto Y, Hashimoto S, Ogawa T, et al. Features of particle and heavy ion
transport code system (PHITS) version 3.02. J. Nucl. Sci. Technol. 2018;55:684-690.
[7] Kino K, Furusaka M, Hiraga F, Kamiyama T, et al. Measurement of energy spectra andspatial distribution of neutron beams provided by the ANNRI beamline for capture crosssection measurements at the J-PARC/MLF. Nucl. Inst. and Meth. A, 2011;626-627:58-66.
[8] Ikeda S, Carpenter JM. Wide-energy-range, high-resolution measurements of neutron pulse
shapes of polyethylene moderators. Nucl. Inst. and Meth. A, 1985;239-3:536-544.

., Capture cross-section studies for 30-220 keV neutrons using a new[9] Macklin R, Gibbons, JJ.
technique. Phys. Rev., 1967;159:1007.
[10] Shibata K, Iwamoto O, Nakagawa T, Iwamoto N, et al. JENDL-4.0: A new library for
nuclear science and engineering. J. Nucl. Sci. Technol. 2011;48:1-30.
[11] Carlson A, Pronyaev V, Capote R, Hale G, et al. Evaluation of the neutron data standards.
Nucl. Data Sheets, 2018;148:143-188.

161- 161 -

JAEA-Conf 2021-001

 ANewMethodtoReduceSystematic
UncertaintiesofCaptureCrossSectionMeasurement
UsingaSampleRotationSystem
Y. Kodama1∗ , T. Katabuchi1 , G Rovira2 , H. Nakano1 , K. Terada3
A. Kimura2 , S. Nakamura2 , S. Endo2
1) Tokyo Institute of Technology
2) Japan Atomic Energy Agency3) Kyoto University
author: kodama.y.ae@m.titech.ac.jp

A new method to reduce systematic uncertainties of capture cross section measurement using a sample rotation
system has been developed. Theoretical and experimental tests on the method have been conducted. Calculations
using Monte Carlo simulation code were performed. Experiments using a sample rotation system at the Accurate
Neutron Nucleus Reaction Measurement Instrument in Materials and Life Science Facility of the Japan Proton
Accelerator Research Complex were also conducted.

I.

Introduction

Accurate nuclear data for neutron-induced reactions are necessary for the design of nuclear transmutation systems to reduce minor actinides (MA) and long lived ﬁssion products (LLFP) containedin nuclear waste. However, current uncertainties of nuclear data for MA and LLFP do not fulﬁll therequirements for the design of transmutation facilities. Measurements of the neutron capture crosssection are ongoing at the Accurate Neutron Nucleus Reaction Measurement Instrument (ANNRI) in the
Materials and Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC).
The neutron capture cross section σ [cm2 ] is determined in the experiments based on the following
equation:
1 Y ( En ),(1)σ=nt φ( En )where n [atoms/cm3 ] is density of sample, t [cm] is thickness of sample, Y is neutron capture reaction
yield and φ is neutron energy specrum.Y ( En ) is derived using pulse-height weighting techniue [1].
φ( En ) is measured using a neutron ﬂux monitor. The neutron capture cross section can be determinedby measuring Y ( Nn ) and φ( En ). In the determination of capture cross section, the systematic uncertainty
of ﬁnal cross section is governed by the incident neutron energy spectrum.
In ANNRI experiments, the neutron energy spectrum can be determined by measuring 478 keV
γ-rays from the 10 B(n,αγ)7 Li reaction. Detected γ-ray counts are converted to the numbers of neutrons
using the reaction rate of the 10 B(N,αγ)7 Li reaction. The energy dependence of the reaction rate depends
on the atomic area density of 10 B in the boron sample because the neutron self-shielding factor increase
with the 10 B area density and also changes with the neutron energy. Thus, 10 B atomic area dinsity isvery important to determine the incident neutron energy spectrum.
In the present work, we suggest a new method to reduce systematic uncertainties related to theincident neutron using a sample rotation system. Theoretical and experimental studies were also
performed.

62-1
162

JAEA-Conf 2021-001

II.

Methodology

1. Principle
The new method employs the change of the self-shielding effect with the sample rotation angle.
When a sample is tilted with respect to the beam axis, the effective thickness of the sample becomes larger
than the actual thickness. The reaction yield at the tilted angle θ in consideration of the self-shielding
effect can be expressed as follows:Yθ = c ·



σcap
1
· φ · 1 − e Ntσtot cosθ
σtot

(2)

where c is the correction factor for the multiple-scattering effect, and σcap and σtot are the capture andtotal cross sections, respectively. The new method suggested below is based on the yield change withsample rotation.

2. Sample Area Density Determination
The new method is for atomic area density determination of 10 B sample which is used for measurement of the incident neutron spectrum in ANNRI experiments. The ratio of the reaction yield at a
rotation angle of 0Âž, Y0◦ to the yield at θ, Yθ ◦ is written as:
1

R=

Yθ ◦
1 − e Ntσtot cosθ=.
Y0◦
1 − e Ntσtot(3)


Area Density[103 atoms/b]

The energy dependence of the yield is measured by the neutron time-of-ﬂight (TOF) method. Thus, theyield ratio R(t) is explicitly written as a function of TOF t.
The reaciton yields of 10 B(n,αγ)7 Li for different area density were calculated using a Monte Carlosimulation code. A typical calculated results of the yield ratio R(t) is of 0Âž to 60Âž is shown in Fig. 1.
The yield ration R(t) is equal to unity at low energies (slow TOF) and increases up to 1/cosθ that is 2.0
for 60Âž at high energy area. The transient TOF region between the two constant values 1.0 and 2.0
changes with the sample atomic area density. We deﬁne Thal f as the TOF value where R(t) becomes thehalf of the maximum. Thal f changes with the sample atomic area density. In other words, the sample
area density can be determined from Thal f . Figure 2 shows a plot of Thal f vs the sample atomic area
density.
1.45
1.4
1.35
1.3
1.25
1.2
1.15
600 620 640 660 680 700 720 740
TOF at half value [μs]Figure 2: Sample atomic area density calibration curve

Figure 1: Reaction ratio TOF spectrum

163- 163 -

JAEA-Conf 2021-001

III.

Analysis

1. Simulation
We performed simulations of the sample rotation measurement by using the Monte Carlo simulation
code PHITS [3]. A 10 B 90% enriched B4 C sample calculated 10 B(n,α)Li7 reaction counts. The ratio at eacha tilted angle and at each thickness was derived from the calculated reaction counts. The calibration
curve was obtained at a tilted angle of 45Âž.

2. Experiment
The sample rotation measurement was performed at ANNRI beam line in MLF of J-PARC. The
sample rotation system installed at the beam line was used to rotate samples. A 10 B 90% enriched B4 C
sample with an area density of 1.259 × 10−3 atoms/b, a diameter of 10 mm and a thickness of 0.5 mm
was used for the test of the rotation system. A nat C sample with a diameter of 10 mm and a thickness of
0.5 mm was used to derive the background events due to scattered neutrons. Neutrons were produced
from the spallation reactions coused by a 3-GeV proton beam shot to a mercury target of the MLF [4].
The neutron beam was collimated to a diameter of 13 mm at the sample position. A TOF method was
employed in this experiment with a neutron ﬂight path of 27.9 m from the spallation source to thesample position. γ-rays emitted from the sample were detected by a NaI(Tl) detector.

Results and Discussion

Ratio Yθ°/Y0°2

θ = 60°θ = 45°
θ = 30°

1.8
1.6
1.4
1.2

1

2

3

10
10
Time of Flight [μs]

1.2
1.1

10

1.3

fit

1.25

1.2

1.15

1.1
0

1000

2000

3000

2

3

10
Time of Flight [μs]Figure 4: Reaction ratio at each a thickness

Area Density[103 atoms/b]

Figure 3: Reaction ratio at each a tilted angle

Ratio Y45°/Y0°

1.3

1

1
10

t = 0.45 [mm]t = 0.50 [mm]t = 0.55 [mm]1.4
Ratio Y45°/Y0°

IV.

fit
1.35
1.3
1.25
1.2
1.15

4000

600 620 640 660 680 700 720 740

Time of Flight [μs]TOF at half value [μs]Figure 5: Reaction ratio TOF spectrum

Figure 6: Sample atomic area density calibration curve164- 164 -

JAEA-Conf 2021-001

1. Simulation of Boron Sample Rotation
TheratioateachatiltedanglewithdifferentthicknesseswereplottedinFig.3andFig.4respectively.
Theseresultswerefittedtothefollowingequation
R(t) =

1 − e(c1 +c2 t)/cosθ
c +c t)1−e(12(4)Theenergydependenceoftheratiochangeswiththicknessandthetiltedangle.Theratioatathicknessof
0.45andatiltedangleof45EFHSFFwasshowninFig.5.Theboroncalibrationcurvetodeterminetheboron sample thickness (Fig. 6) was derived from the result calculated at each thickness. In theanalysis, the area density value of the boron sample of 1.259 ± 0.025 [10−3atoms / b] was obtained.
The calculation results of the first method to determine the boron sample area density is reasonable
agreement.

2. Rotation experiment of a boron sample
TheTOFspectrumof10B(n,αγ)7LireactionshowninFig.wasobtainedbyusingasamplerotation
system. Inthisanalysis,blankbackground,thebackgroundeventsinducedduetoscatteredneutronsatthesampleweresubtracted. Correctionforsmallersamplesizethantheneutronbeamwasemployed.
TheratioY45◦/Y0◦ wasobtainedasshowninFig. 8. Theexperimentalresultsdifferfromthecalculated
one. The applied correction seems insufﬁcient.T hisd isagreementi sp ossiblyc ausedb ysystem
asymmetryorsystemaxismisalignment. Alargerboronsamplethantheneutronbeamisnecessaryinthefuturework
0.04

45 degree
30 degree
0 degree

0.03
0.025

Ratio

count[1/shot]

0.035

0.02
0.015
0.01
0.005
0
2
10

3

4

10
10
Time of Flight[us]Figure 7: TOF spectrum of the 10 B(n,αγ)7 Li reaction

V.

1.4
1.35
1.3
1.25
1.2
1.15
1.1
1.05
1
0.95
0.9
100

exp
phits

1000
Time of Flight [μs]10000

Figure 8: Reaction yield ratio

Summary

In order to reduce systematic uncertainties of neutron capture cross section measurement, a new
method using a sample rotation system were proposed to determine a sample atomic area density for aneutron energy spectrum. The calibration curve for the area density of the boron sample can be obtainedby using Monte Carlo calculation code. A test measurement to determine the boron area density wereconducted. The experimental result were different from the calculated result. We plan to use a larger
boron sample than the neutron beam to test the sample rotation system in the future.

References[1] R. L. Maklin et al. Phys Rev. 159, 1007-1015(1967)[2] R. L. Macklin et al. ,Nuc. Ins. and Meth vol.164, 1, 213-214(1979)[3] T. Sato et al. ,J. Nucl. Sci. Technol. 55, 684-690(2018)[4] F. Maekawa et al., Nuc. Ins. and Meth vol.620, Issues 2-3, 11-21(2010)165- 165 -

JAEA-Conf 2021-001

%FWFMPQNFOUPGBOFVUSPOCFBNNPOJUPSGPSOVDMFBS
EBUBNFBTVSFNFOUVTJOHTQBMMBUJPOOFVUSPOTPVSDF)JEFUP/BLBOP∗ 5,BUBCVDIJ (3PWJSB :,PEBNB ,5FSBEB
",JNVSB 4/BLBNVSBBOE4&OEP
 -BCPSBUPSZGPS"EWBODFE/VDMFBS&OFSHZ 5PLZP*OTUJUVUFPG5FDIOPMPHZ
 +BQBO"UPNJD&OFSHZ"HFODZFNBJM OBLBOPIBH!NUJUFDIBDKQ

Neutron beam intensity for nuclear data measurement is increasing. The qualities of cross section
measurement of radioactive nuclides were signiﬁcantly improved. In neutron capture cross section
measurement, the number of the incident neutrons is necessary to derive the neutron capture crosssection. However, conventional neutron detectors do not have fast response to adapt high counting
rate measurement with spallation neutron sources. To avoid possible failure of a proton pulse counting
method and make measurement with ANNRI more robust, an additional neutron beam monitor isunder development. A plastic scintillator with a thin 6 Li layer is adopted for a detector. A test detector
system was built to study the feasibility of the present method. Test experiments demonstrated thatthe new detection system was able to detect neutrons from the spallation neutron source.

I.

Introduction

Thequalitiesofcrosssectionmeasurementsofradioactivenuclideweresigniﬁcantlyimprovedwithhighintensityneutronbeams. Ithasbeendifﬁculttomeasureneutron-inducedreactioncrosssections
ofradioactivenuclidesduetolargebackgroundofthedecaygamma-raysfromradioactivesamples. In
recentyears,withtheadventofspallationneutronsources,thequalitiesofcrosssectionmeasurement
weresigniﬁcantlyimproved.TheJapanProtonAcceleratorResearchComplex(J-PARC)wasstartedin
operationin2008anditsbeampowerhasbeenincreasedyearbyyear[].Tomeasureneutron-induced
nuclear data using the high intensity neutron beam from the J-PARC spallation neutron source, theAccurateNeutronNucleusReactionMeasurementInstrument(ANNRI)wasbuiltintheMaterialsand
LifeScienceExperimentalFacility(MLF)ofJ-PARC.
In neutron capture cross section measurement, the number of the incident neutrons is important
physicalquantity. Tonormalizethedetectedgamma-rayyieldtothenumberoftheincidentneutrons,
the neutron count is usually monitored by with a neutron detector. However, in measurement with
ANNRI,thenumberofprotonbeampulsesinjectedintothespallationtargethasbeenusedinsteadof
directneutronmonitoring. Thismethodisbasedontheassumptionthatthenumberofprotonbeam
pulses is proportional to the number of incident neutrons. This assumption is mostly plausible but
couldfailwhentheconditionsoftheprotonacceleratorortheneutronsourcechange. Toavoidpossible
failure of the proton pulse counting method and make measurement with ANNRI more robust, an
additionalneutronbeammonitorisunderdevelopment.

II. DetectorDesignTo develop a neutron beam monitor for ANNRI, there are two requirements. Fast time response
adaptsveryhighintensityneutronbeamandlowgamma-raysensitivelyreducesbackground. Inorder166- 166 -

JAEA-Conf 2021-001

to fulﬁll the requirements, a thin sheet-type plastic scintillator combined with a thin 6 Li layer on analuminum ﬁlm is adopted for the present neutron monitor. The incident neutrons react with 6 Li andthe 6 Li(n,t)4 He reaction occurs. The emitted particles, tritons and alphas, are detected with the plastic
scintillator. The short ranges of tritons and alphas allow for using a thin plastic scintillator ﬁlm, and thethin detector leads to low gamma-ray sensibility. Another requirement for fast detection is achieved by
the fast response property of plastic scintillator with 3.7 ns decay time. Simulation studies using Monte
Carlo simulation code PHITS [] were performed to optimize the detector design, especially thicknessof the 6 LiF layer. In Fig. 1, the concept of the detector system is shown schematically.

Figure 1: Detector geometric design.

III.

Experiments

A test detector system was built to study the feasibility. LiF was deposited on an aluminum ﬁlm bya vacuum deposition method. The LiF layer was thin enough for tritons and alpha particles to penetrate
and reach the plastic scintillator. 6 Li was isotopically enriched 95%. The photomultiplier tube was
HAMAMATSU R1306-22ASSY. Test experiments were carried out at ANNRI. The detector was placed
at a ﬂight length of 29.62 m from the spallation neutron source. The beam power was about 500 kW.
The pulse height (PH) and the time-of-ﬂight (TOF) were acquired. TOF measurement was started by asignal from the J-PARC accelerator and stopped by PMT signal. In addition to measurement with the
LiF foil, measurement without the LiF foil was conducted for background evaluation. Measurement
time with 6Li was about 11 min
As shown in Fig. 2, pulse-height (PH) spectra are shown. The spectra were normalized with thenumber of proton pulses. In Fig. 2, the 6 Li(n,t)4 He reaction was successfully observed as a strong peakin the region from 22 ch to 36 ch. In Fig. 3, time-of-ﬂight spectra are shown. Difference between the
spectra with and without LiF is observed in the TOF region from 400 to 35000 μs that corresponds tothe thermal neutron region. The peak of the resonance of 6 Li(n,t)4 He at 250 keV was also observedin the TOF region from 7 to 9 μs. The neutron energy spectrum was derived from TOF spectrum by
dividing the detected neutron counts by the reaction rate calculated from the 6Li(n,t)4He cross section.
To evaluate the system performance, the present results were compared with neutron spectra measured with different methods in previous experiments []. In Fig. 4, the neutron spectrum (red) measured in this work was compared with a neutron spectrum (black) at 27.9 m obtained detecting 478 keVgamma-rays from the 10B(n,α)7Li reaction placing a 10B sample []. The neutron spectra agree well in thethermal neutron region but the present neutron spectrum is slightly higher than the previous measurement in the higher energy region, and deviates from 10 eV. The difference comes from insufﬁcient
subtraction of background that is mainly gamma-ray from the neutron source. The background subtraction must be improved in the future development. Statistical error was 0.68 % at 6 meV. Figure
5 shows another comparison of the present results (red) with a TOF spectrum (black) measured with167
- 167 -

JAEA-Conf 2021-001

a Li glass detector in a previous experiment []. The beam power of the previous experiment was 200
kW. A Pb ﬁlter with a thickness of 5 cm was inserted upstream to reduce the gamma ﬂash from theneutron source while no Pb ﬁlter was used in the present experiment. Detector paralysis caused by the
gamma-ﬂash occurred in the previous experiment. Detector paralysis leads to count loss observed in the
TOF region from 3 to 20 μs in the previous experiment. On the other hand, detector paralysis did notoccur and signiﬁcant count loss did not appear in the present system, despite no use of the Pb ﬁlter. This
experiment was successfully measured without detector paralysis at fast TOF region.

Figure 2: Pulse height spectra with and without LiF.

168
- 168 -

JAEA-Conf 2021-001

Figure 3: TOF spectra with and without LiF.

Figure 4: Comparison of neutron spectra of the present work with the previous measurement by Rovira et al [].

169
- 169 -

JAEA-Conf 2021-001

Figure 5: Comparison of TOF spectra of the present work with the previous measurement by Terada [].

IV. Summary
A new neutron monitor system was designed and built. Signal from the 6 Li(n, t)4 He reaction was
clearly observed. Neutron spectrum was derived from TOF spectrum in data analysis. Statistical error
was 0.68 % at 6 meV. In the future plan, this system will be used as an incident neutron monitor
in nuclear data measurement. Moreover, application to other nuclear cross section measurement isplanned.

References[1] Kino K, Furusaka M, Hiraga F, et al. Measurement of energy spectra and spatial distributions ofneutron beams provided by the ANNRI beamline for capture cross-section measurements at the
J-PARC/MLF. Nucl Instruments Methods Phys Res Section A. 2011;626-627:58-66.
[2] Sato T, Iwamoto Y, Hashimoto S, et al. Features of particle and heavy ion transport code system(PHITS) version 3.02. J Nucl Sci Technol. 2018;55:684-690.
[3] Rovira G, Katabuchi T, Tosaka K, et al. Neutron capture cross-section measurement and resolved
resonance analysis of 237Np. J Nucl Sci Technol. 2020;57:24-39.
[4] Terada K. private communications.

170- 170 -

JAEA-Conf 2021-001

 'HYHORSPHQWRI$EVROXWH(SLWKHUPDODQG)DVW1HXWURQ)OX[,QWHQVLW\'HWHFWRUVIRU%1&7,B[VTIJ"PLJp 4IJOHP5BNBLJ 4BDIJF,VTBLB 'VNJOPCV4BUP *TBP.VSBUB
(SBEVBUF4DIPPMPG&OHJOFFSJOH 0TBLB6OJWFSTJUZ :BNBEBPLB 4VJUBTIJ 0TBLBGV +BQBO

pBPLJ!RSTFFFOHPTBLBVBDKQ
"CTUSBDU
"O BCTPMVUF FQJUIFSNBM OFVUSPO  F7 _  LF7  GMVY JOUFOTJUZ EFUFDUPS BOE B GBTU OFVUSPO  LF7_.F7  GMVY JOUFOTJUZ EFUFDUPS XFSF EFTJHOFE BOE EFWFMPQFE GPS #PSPO /FVUSPO $BQUVSF 5IFSBQZ
#/$5  "GUFS GBCSJDBUJOH UIF EFUFDUPST  JO PSEFS UP UFTU UIF QFSGPSNBODF PG UIF FQJUIFSNBM BOE GBTU
OFVUSPO EFUFDUPST  WFSJGJDBUJPO FYQFSJNFOUT XFSF DPOEVDUFE BU ,63 <>  ,ZPUP 6OJWFSTJUZ BOE '/-
GBDJMJUZ <>  5PIPLV 6OJWFSTJUZ  SFTQFDUJWFMZ "T UIF SFTVMU  UIF FQJUIFSNBMOFVUSPO GMVY JOUFOTJUZ DPVME
CF NFBTVSFE XJUI BO FSSPS PG   BGUFS UIFPSFUJDBMMZ DPSSFDUJOH UIF IJHI FOFSHZ OFVUSPODPOUSJCVUJPO
5IFGBTUOFVUSPOGMVYJOUFOTJUZDPVMEBMTPCFNFBTVSFEBDDVSBUFMZ UIBUJT UIFFYQFSJNFOUBMBOEDBMDVMBUFEWBMVFTBHSFFEXFMMXJUIJOUIFTUBUJTUJDBMVODFSUBJOUZ *OUSPEVDUJPO#/$5JTBQSPNJTJOHDBODFSUIFSBQZXIJDILJMMTUVNPSDFMMTXIJMFTVQQSFTTJOHFYQPTVSFEPTFUPOPSNBMUJTTVFT/PSNBMMZ UIFOFVUSPOGJFMEPG#/$5 XIJDIJTQSPEVDFECZBOVDMFBSSFBDUPSPSBOBDDFMFSBUPS IBT
BOFOFSHZEJTUSJCVUJPOTQSFBEJOHXJUIJOUIFSNBM FQJUIFSNBMBOEGBTUOFVUSPOSFHJPOT#FDBVTFFQJUIFSNBM
OFVUSPOTBSFHFOFSBMMZVTFEGPS#/$5 XFNVTUNFBTVSFUIFFQJUIFSNBMOFVUSPOGMVYJOUFOTJUZUPFWBMVBUF
UIFUIFSBQFVUJDFGGFDUBOEQBUJFOUbTFYQPTVSFEPTF*OBEEJUJPO XFBMTPIBWFUPFWBMVBUFUIFFYQPTVSFEPTFPG
UIF GBTU OFVUSPOT UIBU NBZ CF IBSNGVM UP UIF IVNBO CPEZ )PXFWFS  JU JT RVJUF EJGGJDVMU UP LOPX TVDIJOUFOTJUJFT EJSFDUMZ BOE BDDVSBUFMZ  CFDBVTF UIFSF JT OP TVJUBCMF OFVUSPO TQFDUSPNFUFS BOE OP BDUJWBUJPONBUFSJBM DPWFSJOH FQJUIFSNBM PS GBTU OFVUSPOT TFQBSBUFMZ 5IF PCKFDUJWF PG UIJT XPSL JT IFODF UP EFWFMPQOFXEFUFDUPSTUPQSFDJTFMZNFBTVSFUIFBCTPMVUFJOUFHSBMGMVYJOUFOTJUJFTPGFQJUIFSNBM F7_LF7 
BOEGBTUOFVUSPOT LF7_.F7 
 %FTJHO
%FTJHOPGFQJUIFSNBMOFVUSPOEFUFDUPS
5IF GPMMPXJOHT BSF EFTJHO SFRVJSFNFOUT GPS UIF FQJUIFSNBM OFVUSPO EFUFDUPS   *U TIPVME IBWF GMBU
TFOTJUJWJUZGPSFQJUIFSNBMOFVUSPOTBOEOPTFOTJUJWJUZGPSUIFSNBMOFVUSPOTBOEGBTUOFVUSPOT  *UTIPVMECFBTTNBMMBTQPTTJCMFOPUUPEJTUPSUUIFOFVUSPOGJFME  *UTIPVMECFBWBJMBCMFJOBTUSPOH OFVUSPO GJFME
5IFSFGPSF  XF EFDJEFE UP FNQMPZ UIF GPJM BDUJWBUJPO NFUIPE *O QSFWJPVT

171- 171 -

JAEA-Conf 2021-001

SFTFBSDI <  >  JU XBT DPOTJEFSFE UP BEPQU B TQIFSJDBM TIBQF BT UIF EFUFDUPS  CVU UP NBLF UIFTFOTJUJWJUZGMBUJOFQJUIFSNBMFOFSHZSFHJPO XFBEPQUFEBSFDUBOHVMBSTIBQFEFUFDUPSTIPXOJO'JH <>
5IF FQJUIFSNBM OFVUSPO EFUFDUPS DPOUSPMT JUT TFOTJUJWJUZ CZ VTJOH $E UIFSNBM OFVUSPOBCTPSCFSBOE
QPMZFUIZMFOFOFVUSPONPEFSBUPS 1& "OBDUJWBUJPOGPJMJTQPTJUJPOFEJOUIFDFOUFSBOEUIFGPJMJTDPWFSFEXJUI1&NPEFSBUPSTVSSPVOEFEXJUIB$ETIFFUUPDVUUIFSNBMOFVUSPOT"TGPSUIFDBMDVMBUJPONFUIPE 
XFVTFE.$/1BTOFVUSPOUSBOTQPSUDBMDVMBUJPOUPPMBOE+&/%-BTFWBMVBUFEOVDMFBSEBUBMJCSBSZ<>
5IF EFTJHO QSPDFEVSF DPOTJTUT PG UXP QSPDFTTFT 0OF JT UP GJY UIF BDUJWBUJPO GPJM BOE 1& NPEFSBUPSUIJDLOFTTUPNBLFUIFTFOTJUJWJUZGMBUUPFQJUIFSNBMOFVUSPOT5IFPUIFSJTUPEFTJHOUIF$EUIJDLOFTTUPDVUPWFSPGUIFTFOTJUJWJUZGPSF7OFVUSPOT5IFEFTJHOHPBMJTUIBUGMVDUVBUJPOJOUIFTFOTJUJWJUZUPFQJ
UIFSNBMOFVUSPOTJTUPCFXJUIJO

'JH%FTJHODBMDVMBUJPONPEFM
"TUIFEFTJHOSFTVMU  (B O ϡ  (BSFBDUJPOXBTTFMFDUFEBTUIFBDUJWBUJPOSFBDUJPOBOEUIFTIBQFPGUIFEFUFDUPSXBTGJYFEUPCFBSFDUBOHVMBSQPMZFUIZMFOF DN DPWFSFEXJUIBDBENJVNTIFFUPGDN
JOUIJDLOFTT'JHTIPXTUIFGJOBMMZEFTJHOFEEFUFDUPSbTTFOTJUJWJUZ5IFCMVFMJOFTIPXTUIFTFOTJUJWJUZPGUIJTEFUFDUPS5IFHSFFOSFHJPOJTUIFFQJUIFSNBMOFVUSPOSFHJPO BOEUIFSFEMJOFJTUIFBWFSBHFTFOTJUJWJUZ
JO UIBU SFHJPO 5IF GMVDUVBUJPO PG UIF QSPEVDUJPO ZJFME PG (B GPS FQJUIFSNBM OFVUSPO JT   BOE UIFTIJFMEJOHSBUFPGF7OFVUSPOJT)PXFWFS UIJTEFUFDUPSJTBMJUUMFTFOTJUJWFUPGBTUOFVUSPOT)LJ6HQVLWLYLW\RIHSLWKHUPDOQHXWURQGHWHFWRU
172- 172 -

JAEA-Conf 2021-001

%FTJHOPGGBTUOFVUSPOEFUFDUPS 5P DMBSJGZ UIF GBTU OFVUSPO DPOUSJCVUJPO  XF EFWFMPQ UIF GBTU OFVUSPO EFUFDUPS 5P FYUSBDU POMZ GBTU
OFVUSPOT  UIF GBTU OFVUSPO EFUFDUPS DPOTJTUT PG UXP TVCEFUFDUPST  BOE UIF GBTU OFVUSPO GMVY JT
FTUJNBUFEGSPNUIFEJGGFSFODFJOTFOTJUJWJUZCFUXFFOUIFUXPTVCEFUFDUPST"GBTUOFVUSPOEFUFDUPSDPOUSPMTUIFTFOTJUJWJUZCZVTJOHDBENJVN #$BOEQPMZFUIZMFOF5IFTIBQFPGPOFPGUIFUXPJTBDVCFDPWFSFEXJUIQPMZFUIZMFOF XJUI B TJEF PGDN 1&UZQF  BOEUIF PUIFS JT BDVCF DPWFSFEXJUI#$XJUIBTJEFPG
DN #$ UZQF  BT TIPXO JO 'JH  'PS CPUI  (B/ GPJMT BSF DPWFSFE XJUI $E TIFFUT UP FMJNJOBUF UIFSNBMDPNQPOFOU

'JH1SPUPUZQFGBTUOFVUSPOEFUFDUPST)PXFWFS  JO PSEFS UP SFEVDF UIF TFOTJUJWJUZ UP UIFSNBM BOE FQJUIFSNBM OFVUSPOT  UIF TFOTJUJWJUZ PG #$
UZQF XBT TVCUSBDUFE GSPN UIBU PG 1& UZQF NVMUJQMJFE CZ B GBDUPS PG "   )FSF  UIFNVMUJQMJDBUJPO GBDUPS"XBT DBMDVMBUFE TP BTUPNBLF UIF GPMMPXJOH FRVBUJPOUP IBWFUIF NJOJNVNWBMVF
"MTP  'JH  TIPXT UIF TFOTJUJWJUZ PG UIF GBTU OFVUSPO EFUFDUPS 5IF CMVF MJOF TIPXT UIFTFOTJUJWJUZPGUIJTEFUFDUPS5IFHSFFOSFHJPOJTUIFGBTUOFVUSPO LF7_.F7  SFHJPO BOEUIFSFEMJOFJTUIFBWFSBHF
TFOTJUJWJUZJOUIBUSFHJPO
ଵ଴୩ୣ୚

ଶ

෍ ൫‫୔ܻ × ܣ‬.୉. (E) െ ܻ୆ସେ (E)൯୉ୀ଴.଴ଵୣ୚(1)

XIFSFܻ1& & BOEܻ#$ & BSFUIFDBMDVMBUFE(BQSPEVDUJPOZJFMETGPS1&UZQFBOE#$UZQF SFTQFDUJWFMZ

173- 173 -

JAEA-Conf 2021-001)LJ6HQVLWLYLW\RIIDVWQHXWURQGHWHFWRU ([SHULPHQWV
 9DOLGDWLRQH[SHULPHQWRIHSLWKHUPDOQHXWURQGHWHFWRU
 ,QRUGHUWRWHVWWKHSHUIRUPDQFHRIWKHHSLWKHUPDOQHXWURQGHWHFWRUDYHULILFDWLRQH[SHULPHQWZDVFRQGXFWHGDW.85.\RWR8QLYHUVLW\$IWHUWKHH[SHULPHQWZHFDQGHGXFHWKHHSLWKHUPDOQHXWURQIOX[LQWHQVLW\ ����  >QFPVHF@E\IROORZLQJHTXDWLRQ ���� =ZKHUH4>%T@LVUDGLRDFWLYLW\RI*D<>�(1
Y × − e���� )��������_�����

������_�������/���(2)

@LV*DSURGXFWLRQVHQVLWLYLW\ λ >VHF@

LVGHFD\FRQVWDQWRI*DDQG �� >VHF@LVLUUDGLDWLRQWLPH

,QWKHWHVWVXIILFLHQWDFWLYLW\RI*DFDQEHLQGXFHGRQO\DVKRUWSHULRGLUUDGLDWLRQ0HDVXUHPHQWFRQGLWLRQVDUHVKRZQLQ7DEOH7KHUHDUH*DDQG*DLQQDWXUDO*D6LQFHWKLVGHWHFWRUXVHV*D Q γ *DUHDFWLRQRQO\WKHUDGLRDFWLYLW\RI*D NH9 ZDVPHDVXUHGZLWKWKH +3*H GHWHFWRU 7KH UDGLRDFWLYLW\ LPPHGLDWHO\ DIWHU LUUDGLDWLRQ RI *D ZDV  N%T >@

7KHUHIRUHWKHHSLWKHUPDOQHXWURQIOX[LQWHQVLW\LVHVWLPDWHGWREHʹ>QFPVHF@E\XVLQJ(T  7KHQRPLQDOYDOXHRIWKHHSLWKHUPDOQHXWURQ H9(QNH9 IOX[LQWHQVLW\LVJLYHQ
WREHʹ>QFPVHF@E\.85%HFDXVHWKLVGHWHFWRULVDOLWWOHVHQVLWLYHWRIDVWQHXWURQVDVPDOOGLVFUHSDQF\LVVHHQEHWZHHQWKHH[SHULPHQWDOYDOXHDQGWKHQRPLQDOYDOXH
7R LQYHVWLJDWH WKH FRQWULEXWLRQ IURP IDVW QHXWURQV ZH FDUULHG RXW D FRUUHFWLRQ FDOFXODWLRQ E\
0&13$VDUHVXOWWKHDPRXQWRIDFWLYDWLRQE\IDVWQHXWURQVZDVHVWLPDWHGWREH%TZKHQVLPXODWLQJZLWKWKHVDPHV\VWHPDVWKHH[SHULPHQW5HPRYLQJWKHFRQWULEXWLRQIURPIDVWQHXWURQ
WKHUDGLRDFWLYLW\EHFRPHVN%T7KHQWKHHSLWKHUPDOQHXWURQIOX[LQWHQVLW\LVILQDOO\HVWLPDWHG
WREHʹ>QFPVHF@E\XVLQJ(T  ,WVKRZVDQH[FHOOHQWDJUHHPHQWZLWKWKHJLYHQYDOXH
E\f
174- 174 -

JAEA-Conf 2021-001

7DEOH0HDVXUHPHQWFRQGLWLRQV 9DOLGDWLRQH[SHULPHQWRIIDVWQHXWURQGHWHFWRU
 ,Q RUGHU WR WHVW WKH SHUIRUPDQFH RI WKH IDVW QHXWURQ GHWHFWRU D YHULILFDWLRQ H[SHULPHQW ZDVFRQGXFWHGDWWKH)1/IDFLOLW\7RKRNX8QLYHUVLW\7KUHHW\SHVRIH[SHULPHQWVZHUHSHUIRUPHGE\FKDQJLQJWKHDSSOLHGYROWDJHRISURWRQDQGWKHEHDPFXUUHQW$IWHUWKHH[SHULPHQWZHFDQGHGXFH
WKHIDVWQHXWURQIOX[LQWHQVLW\ ����� >QFPVHF@E\IROORZLQJHTXDWLRQ����� =

� × ��� − ����Y × (1 − e���� )(3)

ZKHUH$>@LVPXOWLSOLFDWLRQIDFWRU ���  >%T@LV*DUDGLRDFWLYLW\RI  3(W\SH ���� >%T@LV*DUDGLRDFWLYLW\ RI  %&W\SH < >������_�������/���@ LV *D SURGXFWLRQ VHQVLWLYLW\ λ >VHF@ LVGHFD\��������_�����

FRQVWDQWRI*DDQG �� >VHF@LVLUUDGLDWLRQWLPH

7DEOH  VKRZV WKH H[SHULPHQWDO IDVW QHXWURQ IOX[ LQWHQVLWLHV REWDLQHG E\ XVLQJ WKH SURWRW\SH

GHWHFWRUFRPSDUHGWRWKHFDOFXODWHGYDOXHV)URPWKLVWDEOHWKHIDVWQHXWURQIOX[LQWHQVLW\FRXOGEHPHDVXUHGDFFXUDWHO\
7DEOH(VWLPDWHGIDVWQHXWURQIOX[LQWHQVLW\175- 175 -

JAEA-Conf 2021-001

4. Conclusion
Neutron flux intensity detectors for epi-thermal and fast neutrons were developed andexperimentally tested at KUR, Kyoto University and FNL facility, Tohoku University, respectively.
As a result, the epi-thermal neutron flux intensity in the neutron field for BNCT in KUR could
experimentally be estimated with a good accuracy of 10 % error. The fast neutron flux intensity
could also experimentally be estimated accurately in FNL of Tohoku University.
In the future, we will conduct a verification experiment of fast detector at KUR. And thereafter wewould like to conduct experiments in a real neutron field of Accelerator-Based Neutron Sources(ABNS) for BNCT.
Acknowledgments
The authors would like to express their sincere gratitude to Dr. Hiroki Tanaka and Dr. Yoshinori
Sakurai of Institute for Integrated Radiation and Nuclear Science, Kyoto University, who let us use
the BNCT irradiation facility at KUR as a cooperative research, and Dr. Shigeo Matsuyama of Fast
Neutron Laboratory, Graduate School of Engineering, Tohoku University, who allowed us to carryout experiments at the FNL facility with his warm support and guidance.
References[1] 京都大学複合原子力科学研究所, “京都大学研究用原子炉(KUR),” [オンライン]. Available:
https://www.rri.kyoto-u.ac.jp/facilities/kur. [アクセス日: 6 1 2021].
[2] 東北大学 松山・菊池研究室, “高速中性子実験室 -Fast Neutron Laboratory, Tohoku Univ.-,”[オンライン]. Available: http://web.tohoku.ac.jp/fnl/. [アクセス日: 26 12 2020].
[3] G. Xingcai, “Design of an epi-thermal neutron flux intensity monitor with GaN wafer forboron,” J. Nucl. Sci. Technol., Vol. 52, No. 4, pp.503–508, 2015.
[4] G. Xingcai, “Design study of neutron flux intensity monitor between ten and several hundred
keV for BNCT,” J. Nucl. Sci. Technol.,Vol. 53, No. 8, pp.1112–1119, 2016.
[5] Y. Kashiwagi, “Development of epi-thermal neutron beam intensity detector with 71Ga(n,γ)72Ga reaction for boron neutron capture therapy,” Appl. Radiat. Isot. Vol.151, pp.145-149,
2019.
[6] K. Shibata et. al., "JENDL-4.0: A New Library for Nuclear Science and Engineering," J. Nucl.

Technol, vol. 48(1), pp. 1-30, 2011.

[7] Glenn F. Knoll, "Radiation Detection and Measurement -4th ed.," Wiley, 2010, pp. 767-769.

176- 176 -

JAEA-Conf 2021-001

 Optimization of Activation Detector for Benchmark Experimentof Large-angle Elastic Scattering Reaction Cross Section by 14MeV
Neutrons
Ryohei TAKEHARA, Kazuki FUKUI, Sota ARAKI, Shingo TAMAKI, Sachie KUSAKA andIsao MURATA
Graduate school of Engineering, Osaka University, Yamada-oka 2-1, Suita, Osaka 565-0871, Japan

Email: takehara.ryohei@eb.see.eng.osaka-u.ac.jp
The neutron elastic scattering reaction cross section data commonly show smaller in backward
angles compared to those of forward angles when the energy of incident neutron is high. However, in ahigh neutron flux field, such as fusion reactor, the back-scattering reaction cross section is known tobecome not negligible. Practically, until now, there were differences reported between experimental andcalculated values of neutron benchmark experiments using a DT neutron source (deuterium-tritium),
which focused on back-scattering phenomena like a gap streaming experiment to verify the prediction
accuracy of neutron streaming passing through narrow gaps while scattering. For this problem, wedeveloped a benchmark method for large-angle scattering cross sections and has carried out experiments
to measure the large-angle elastic scattering cross section of iron for the last few years. The benchmark
method was successfully established based on activation reaction of Nb having a large activation crosssection at around 14 MeV. However, Nb foil takes a long time to obtain the enough number of counts
due to the long half-life (10.2 day) and low detection efficiency of the decay gamma-ray. In this study,
to find a more suitable activation foil, we examined possible nuclides having appropriately short halflives, not so high gamma-ray energies because high detection efficiency is essential, large activation crosssections, and not too low threshold energies of nuclear reaction. The optimization was carried out by
calculating and comparing the number of counts per reaction per nuclide for all nuclides listed in
JENDL/AD-2017.As a result, we have found that 197Au(n,2n)196Au was the most suitable reaction giving
us the largest number of counts in an acceptable short experimental time.

1. Introduction
As shown in Fig. 1, The neutron large-angels scattering reaction cross section data with high energy
neutron. This difference is not negligible in neutronics designs of high neutron flux fields in such as
fusion reactor. Therefore, it is necessary to measure back-scattering cross sections of Fe, Li, C, B etc. to
be used in the fusion reactor design. For this problem we designed the experimental system to extract thecontribution of large angle scattering reaction. [1] The benchmark method was successfully establishedbased on the activation of Nb foil normally used to characterize DT neutron sources. [2] However, Nb
foil takes a long time to obtain the enough number of counts due to the long half-life of about 10 days
and the low detection efficiency of the decay gamma-ray (energy of the decay gamma-ray = 934 keV).
In this study, to solve this problem, we examined possible activation nuclides having appropriately shorthalf-lives, not so high decay gamma-ray energies because high detection efficiency is essential, large177- 177 -

JAEA-Conf 2021-001

cross sections. And not too low threshold energies are required for the accuracy of benchmark
experiments.

2. Benchmark experiments
Basic structure of the experimental systems and neutron transport paths we consider in benchmark
experiments are shown in Fig. 2. A shadow bar is installed to prevent neutrons from directly incident on
activation foil, which detects neutrons, from a neutron source. Possible paths that a neutron can transportand contribute to the activation of the foil are numbered from 1 to 7. Path 1 is the neutron path via the
shadow bar. Path2 is the neutron path via the shadow bar and the sample. Path 3 is the backscatteredneutron from the sample, which is an object to be extracted. Path 4 is the neutron path via the wall andshadow bar. Path 5 is the neutron path via the wall and the sample. Path 6 is the neutron path via the wall.
Path 7 is the neutron path via the shadow bar and the wall and the sample.
The benchmark experiments are conducted in four experimental systems for extracting thecontribution of large angle scattering reaction. Figure 3 shows the four experimental systems, two of
which are with a thin shadow bar with and without the target, i.e., s1tc and s1c, and the rest two of which
are with a thick shadow bar with and without the target, i.e., s2tc and s2c. Figure 3 also shows relation of
the neutron transport paths that contribute to activation of the foil in each of the four systems. The
contributions of paths 1, 4, and 6 are the same for s1tc and s1c, and for s2tc and s2c, because they dependon the size of the shadow bars, but not depend on that of the sample. That of path 5 is the same for s2tc
and s1tc, and for s1c and s2c, because it depends on the presence of the sample. Therefore, calculating
s1tc-s2tc-(s1c-s2c), we can estimate the amount of activation by neutrons through paths 2, 3 and 7. Thoseof paths 2 and 7 does not cancel each other out. However, they are relatively a rare event, because thetransporting neutron through the paths experiences a large number of scatterings. It means thecontributions of paths 2 and 7 show less than path 3 largely. We thus regard the two contributions as theexperimental error of the present benchmark method. By comparing the amount of activation obtained by
the experiment with MCNP simulation (the Monte Carlo simulation) [3], the correctness of thebackscattering cross section of the nuclear data can be verified. As an example, the result of a benchmark
experiment with the iron sample is detailed in Ref. [2].

Figure 1 Angular distribution of neutron elastic scattering reaction cross section of 56Fe at 14
MeV. [4-8]178- 178 -

JAEA-Conf 2021-001

Figure 2 Basic structure of the experimental

Figure 3 Four experimental systems and neutron

systems and neutron transport paths we consider
in benchmark experiments. [1]transport paths that contribute to activation foreach system. [1]

3. Method to optimize
At present, we need about one week to complete the benchmark experiments and another one week
to finish measurement of the activation foils, in case of Nb foil is employed. To reduce the irradiationand measuring time, calculations of the number of counts for possible activation reactions werecarried out for all nuclides stored in JENDL/AD-2017 using following equation:ͳ ൌ ܰ න ߪ݂௡ ߮  ൈ ൈ ݂ ൈ ݃ ൈ ‫ܫ‬௥ ൈ ߝ ൈ ൫ͳ െ ݁ ିఒ௧௜ ൯ ൈ ݁ ିఒ௧௖ ൈ ൫ͳ െ ݁ ିఒ௧௠ ൯ ൈ ‫ܶܦ‬
ߣ
ா

ሺͳሻ

where ܰ, ߪ, ݂௡ , ߮, ߣ, ݂, ݃, ‫ܫ‬௥ , ߝ, ‫݅ݐ‬, ‫ܿݐ‬, ‫ ݉ݐ‬DT represent the number of atoms, cross-section[cm2] [9], factor of neutron self absorption [3], flux on foil calculated by MCNP with Fe sample[/cm2/source neutron], decay constant [/s] [10], self shielding factor [11], isotopic ratio [12],gamma-ray emission ratio [10], gamma-ray detection efficiency, irradiation time [s], cooling time[s], measurement time [s] and neutron intensity [/s] (=ͷ ൈ ͳͲଽ ), respectively. Consequently,
candidate activation nuclides showing the highest accuracy (the largest number of counts) were
found. To prevent the error of the count number from being dominant, we searched for an activation
foil that can obtain 10,000 counts in the shortest time.
Since the present benchmark experiments are conducted in OKTAVIAN facility of Osaka
University, Japan, there are constraints on the present calculation as follows. The maximum
irradiation time per day is 8 hours, and in the case of consecutive day’s experiment, the coolingtime of 16 hours between irradiations is required. In addition, the maximum measurement time was
set to 5 days. And gamma-ray detection efficiency used the value when the decay gamma-rays aremeasured at a distance of 3.1 cm from the detection window using germanium detector. The energyof backscattered neutrons by the sample is about 8-14 MeV depending on kind of the sample
nuclides, because the incident neutron energy is 14 MeV. Even if the reaction threshold energy is
below 8 MeV, the reaction cross section may still be low for the backscattered neutrons. Therefore,
in this study, we do not take into account the threshold energy, i.e., the threshold energy conditionis set to 0-14 MeV.

4. Result
The number of counts of the decay gamma-ray from Nb foil and the one that can realize the countnumber larger than 2,000 counts in the combination of irradiation and measurement are shown in Fig. 4.
179- 179 -

JAEA-Conf 2021-001

This figure shows the increase in the number of counts measured for 1 to 5 days, when irradiation
continues for 1 to 4 days. As can be seen from Fig. 4, it is found that the most efficient activation material
to obtain 10,000 counts for the shortest irradiation and experimental period is gold using 197Au(n,2n) 196Au
reaction. Table 1 shows a comparison of the threshold energy, cross-sectional area, half-life, gamma rayenergy and gamma ray emission ratio of 196Au and 92mNb. However, since 196Au has multiple excitedstate with a half-life of several minutes or more in Fig. 5 [13], it decays from two excited levels to theground state over time. Then the number of counts of the decay gamma-ray from ground state is expected
to be higher than estimation with Eq. (1).
Irradiation
1 day

2 day

3 day

4 day

107Ag(n,2n) 106mAg

Count

Measurement

4 day
3 day
2 day 5 day
1 day

m2

9.6 h
2.0 ns< 30 ns< 30 ns
1.65 ns

m1
g

8.1 s
6.183 d197Au(n,2n) 196Au
191Ir(n,2n) 190Ir
193Ir(n,2n) 192Ir
93Nb(n,2n) 92mNb

Au


197

123Sb(n,2n) 122Sb

Figure 4 The number of counts of nuclides whosecounts are larger than Nb foil.

Figure 5 The multiple excitedlevels of 196Au.

Table 1 Comparison of 92mNb and 196Au.
92mNb

196gAu196m1Au

196m2Au

Threshold energy [MeV]Cross section at 14 MeV [barn] [8]

9.1
0.45

8.1
1.89

8.2
0.15

8.7
0.13

Half-life

10.1 d

6.1 d

8.1 s

9.6 h

Energy of emitted gamma ray [keV]

934

356

85

148

Emission ratio [%]

99

87

0.3

43

5. Formulation of foil activation method using gold foil

If the number of counts is represented by Eq. (1), reaction rate, ‫׬‬ா ߪ߮ , can be estimated from thenumber of counts of experiments. Then the correctness of the backscattering cross section of nuclear data
can be verified by comparing the estimated reaction rate with the one calculated by the MCNP simulation.
In the case of gold, the number of counts cannot be expressed simply by Eq. (1) with the fact describedin Chap. 4. We thus need to formulate precisely to calculate the number of counts for gold in realapplications. The number of counts in the case of two days of irradiation as shown in Fig. 6 is expressedby following equation: ൌ ܰ஺ න ݀‫ ܧ‬ൈ ݂ ൈ ݃ ൈ ‫ ݎܫ‬ൈ ߝǡாሺʹሻwhere R is a term that includes cross section and decay constant, irradiation time, measurement time, andcooling time as shown in following equations. In these equations, ߪ଴ , ߪଵ , ߪଶ , ߣ଴ , ߣଵ , ߣଶ represent
cross sections of ground state, first excited state, second excited state, decay constant of ground state,
first excited state, second excited state, respectively.
 ൌ ሺ߮ଶ ଶ ൅ ߮ଵ ଶ ሻ൫ͳ െ ݁ ିఒబ ௧೘ ൯ ൅ ሺ߮ଶ ଶ ൅ ߮ଵ ଶ ሻ ൬ͳ െ180

- 180 -ߣଶߣ଴݁ ିఒబ௧೘ െ݁ ିఒమ ௧೘ ൰ሺߣଶ െ ߣ଴ ሻሺߣଶ െ ߣ଴ ሻሺ͵ሻ

JAEA-Conf 2021-001

1 day irradiation

φ1

ߪൌ
࢚ࢉ૚

ߪ଴ ൅ ߪଵ ൅ ߪଶ ߪଵ ൅ ߪଶ
ߪଶ
൅
൅
ߣ଴
ߣଵ
ߣଶ െ ߣ଴
2 day irradiation

࢚࢏૚

࢚

φ1

࢚ࢉ૚

ሺͶሻ
࢚࢏

φ2

࢚ࢉ

࢚

Fig. 6 Summary of the experiments.
For 1 day irradiation, irradiate with flux ɔଵ for ‫ݐ‬௜ଵ, cool for ‫ݐ‬௖ଵ and thenmeasure the decay gamma-ray for ‫ݐ‬௠ . For 2 day irradiation, irradiate withflux ɔଵ for ‫ݐ‬௜ଵ, cool for ‫ݐ‬௖ଵ and irradiate with flux ɔଶ for ‫ݐ‬௜ଶ, cool for‫ݐ‬௖ଶ and then measure the decay gamma-ray for ‫ݐ‬௠ .

where A, B, C and D are given as below:ߪଶߪଶ ൌ ɐ൫ͳ െ ݁ ିఒబ௧೔భ ൯ ൅൫ͳ െ ݁ ିఒమ௧೔మ ൯݁ ିఒమ௧೎మ ൅൫ͳ െ ݁ ିఒమ ௧೔మ ൯݁ ିఒమ ௧೎మߣ଴ െ ߣଶߣଵ െ ߣଶߪଶߪଶ൫ͳ െ ݁ ିఒమ௧೔మ ൯݁ ିఒమ௧೎భ ൅൫ͳ െ ݁ ିఒమ௧೔భ ൯݁ ିఒమ௧೎భ ିఒభ ௧೔భߣଶߣଵ െ ߣଶ
ߪଶ൅ߪ൫ͳ െ ݁ ିఒబ ௧೔భ ൯݁ ିఒబ ௧೔మ ൅൫ͳ െ ݁ ିఒమ௧೔భ ൯݁ ିఒమ௧೎భିఒబ௧೔మ
ൌߣ଴ െ ߣଶߪଶߪଶ൅൫ͳ െ ݁ ିఒమ௧೔భ ൯݁ ିఒమሺ௧೔మ ି௧೎భ ି௧೎మሻ ൅൫ͳ െ ݁ ିఒమ௧೔భ ൯݁ ିఒమሺ௧೎భ ି௧೔మ ି௧೎మ ሻߣ଴ െ ߣଶߣଵ െ ߣଶఙఙ‫ ܥ‬ൌ మ ൫ͳ െ ݁ ିఒమ௧೔మ ൯݁ ିఒమ௧೎మ , ‫ ܦ‬ൌ మ ൫ͳ െ ݁ ିఒమ௧೔భ ൯݁ ିఒమሺ௧೎భି௧೔మି௧೎మሻ
ఒమ

ఒమ

Recalculating the number of counts of 197Au(n,2n) 196 Au using Eq. (2), considering increment due todecay of 196m1Au and 196m2Au, does not change significantly from Fig. 4 because ߪ଴ is one digit larger
than ߪଵ and ߪଶ .

It is generally known that the nuclear data of the activation cross sections may have errors. Since
the errors of nuclear data of the activation cross sections (ߪ଴ , ߪଵ , ߪଶ ) cause the errors of R calculated
from MCNP simulation, it would be better to normalize ߪ଴ , ߪଵ , ߪଶ  with accurate re-measured values at
14 MeV experimentally. Since the number of counts of gamma rays emitted from 196m2Au can simply becalculated by Eq. (1), ߪଶ can be normalized accurately at 14 MeV. On the other hand, since the emission
ratio of gamma rays emitted from 196m1Au is small, the half-life is very short and the number of 196m1Auchanges largely depending on the decay of 196m2Au, the number of counts of gamma rays emitted from
196m1Au cannot be expressed by Eq. (1). As a result,number ofߪଵ cannot be normalized easily. Similarly, theAu changes irregularly due to existence of 196m1Au and 196m2Au, ߪ଴ cannot also be
normalized easily. Therefore, we consider the following measuring procedure to utilize 197Au(n,2n) 196Au
in benchmark experiments.
196

First of all, paying attention to the fact that R can be represented by ߪଶ and ߪ (including ߪ଴ , ߪଵ ,and ߪଶ ) as shown in Eqs. (3) and (4), it can be seen that normalizing only ߪଶ and ߪ can eliminate theerror of activation cross section in R. For normalizing ߪ, cooling for 3 days after 1day irradiation. Then
Au and 196m1Au almost decay and finally fall to the state of 196Au. Therefore, 197Au(n,2n)196Au canbe regarded as the virtual reaction in which 196Au is just generated with the cross section σ, and the countnumber can be calculated by following equation:
196m2

۱‫ ܜܖܝܗ‬ൌ  ࡺ࡭ න ࣐૚ ࣌ࢊࡱ ൈ ൫૚ െ ࢋିࣅ૙ ࢚࢏૚ ൯ࢋିࣅ૙࢚ࢉ૚ ൈ ࢌ ൈ ࢍ ൈ ࡵ࢘ ൈ ࢿࡱ181- 181 -

ሺ૞ሻ

JAEA-Conf 2021-001

The virtual cross section value in Eq. (4), σ, can thus be normalized and to be used in real benchmark
experiments in future.
The experiment to measure ߪଶ and ߪ precisely in OKTAVIAN facility of Osaka University iscurrently underway.

6. Conclusion
It was found from the theoretical examination that gold was the best activation foil to replace Nbfoil for the present benchmark experiment. In addition, the difficulty of using the reaction of 197Au(n,2n)
due to the multiple excited levels, 196m1Au and 196m2Au, in the activated gold foil is successfully overcome.
After normalizing the cross section at 14 MeV at OKTAVIAN facility of Osaka University, the gold foil
activation method would be utilized for our benchmark experiments in future.

References

N. Hayashi et al., “Optimization of Experimental System Design for Benchmarking of Large
Angle Scattering Reaction Cross Section at 14 MeV Using Two Shadow Bars”, Plasma and
Fusion Research, 2018; 13: 2405002, 1-7.



A. Yamaguchi et al., “Benchmark experiment of large-angle scattering reaction cross section
of iron at 14 MeV using two shadow bars – Comparison of experimental results with ENDF/BVIII –”, Journal of Nuclear Science and Technology, 2021; 58 (1), 80-86.

Team, X-5 Monte Carlo, "MCNP –A General Monte Carlo N-Particle Transport Code,
Version," Los Alamos National Laboratory, pp. LA-UR-03-1987, 2003.



K. Shibata et al., "JENDL-4.0: A New Library for Nuclear Science and Engineering," J. Nucl.
Sci. Technol, 2011; 48 (1), 1-30.



M. B. Chadwick et al., “ENDF/B-VII.0: Next Generation Evaluated Nuclear Data for Nuclear
Science and Technology”, Nucl. Data Sheets, 2006; 102, 2931-3060.



JEFF-3.3 [Online]. France: The Nuclear Energy Agency; 2017 Nov. 20Available from:

https://www.oecd-nea.org/dbdata/jeff/jeff33/index.html>$FFHVVHG$XJ@
FENDL-3.1 [Online]. Austria: International Atomic Energy Agency; 2016 July 1
Available from: https://www-nds.iaea.org/fendl/>$FFHVVHG$XJ@

D. A. Brown et al., "ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data
Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data",

Nuclear Data Sheets, 2018; 148, 1-142.
 K. Shibata et al., “Activation Cross-section File for Decommissioning of LWRs”, JAEA-Conf
2016-004, 2016; 47-52.
 S. Y. F. Chu, L.P.et al., WWW Table of Radioactive Isotopes [Online] 1999 Feb$YDilable
http://nucleardata.nuclear.lu.se/nucleardata/toi/>$FFHVVHG0D\@Available from: http://nucleardata.nuclear.lu.se/toi/[Accessed: November 17, 2021]
 M. J. Berger at el., XCOM: Photon Cross Section Database (version 1.5) [Online]. USA:
National Institute of Standards and Technology; 2010
Available from:http://physics.nist.gov/xcom>$FFHVVHG-XO@ J. S. Coursey et al., Atomic Weights and Isotopic Compositions (version 4.1). [Online]. USA:
National Institute of Standards and Technology; 2015
Availablefrom: http://physics.nist.gov/Comp >$FFHVVHG0D\@ R. B. Firestone et al., “Table of Isotopes, 8th ed”. (Wiley, New York, 1999).
182- 182 -

JAEA-Conf 2021-001

 Nondestructive Determination of Water Content
in Concrete Using Am-Be Neutron Source- Experimental VerificationYoshihiro Miyaji, Shingo Tamaki, Sachie Kusaka, Fuminobu Sato, Isao Murata,
Department of Sustainable Energy and Environmental Engineering, School of Engineering,Osaka University, 2-1 Yamadaoka Suita, Osaka 565-0871, Japan
̊Email: miyaji@qr.see.eng.osala-u.ac.jp
Abstract
New nondestructive measurement technique has been developed with an AmBe neutron source toevaluate the amount of water in concrete. A concrete wall is irradiated with fast neutrons to activate a gold
foil set on the concrete. By evaluating in advance the relation of the gold activity and water content by
calculations, we can determine the water content in the concrete, the water content of which is not known. In
this study, to validate the present technique, experiments were performed with concrete samples having
different water contents, which were made from only cement and water. It was confirmed from theexperiments that water content could be estimated by the present nondestructive measurement technique forsamples made of cement and water. Now we are examining the validity for concretes made of cement, waterand sand.
1. Introduction
Concrete is often used in nuclear facilities for radiation shield. Shielding performance of neutrons depends
mainly on water in concrete, because neutrons are mainly moderated by hydrogen atoms in water containedin concrete. However, concrete loses its contained water as time passes. It can affect the ability of radiation
shield. We want to know water content in concrete for confirmation of the shielding performance of nuclear
facilities and for high-precision neutronics experiments. However, destructive methods to measure watercontent in concrete are not suitable in nuclear facilities. So It is necessary to establish a new technique tonondestructively determine water content in concrete.
In the present study, a new nondestructive measurement technique is developed to evaluate the amount ofwater in concrete, and to validate the present technique experiments are performed with concrete samples
having different water contents, which are made from only cement and water.
2. Nondestructive measurement technique
It is known from previous studies that when a concrete sample is irradiated with neutrons, the neutrons aremoderated according to water content in the concrete. In other words, the number of fast neutrons moderated
to thermal neutrons is determined mainly by the amount of water in the concrete. By combining the property
explained above with the foil activation method, water content in concrete can be determined by the following
183- 183 -

JAEA-Conf 2021-001

procedure developed in the previous study [1].
As in an experimental system shown in Fig. 2.1, a gold foil and Am-Be neutron source are placed on
the concrete. The concrete is irradiated with fast neutrons by the Am-Be neutron source. Then, theneutrons are moderated mainly by hydrogens in the concrete, moderated neutrons are leaking from theconcrete surface. The moderated neutrons enter the gold foil and activate it. Fast neutrons can be wellmoderated, if the amount of water increases. As a result, the gold foil can be well activated. It means that
there should be a correlation between the water content in the concrete and the gold activity. In this study,
to make the calibration curve of gold activity to water content, series simulation calculations were
performed using MCNP5 [2], that is, gold activities are calculated for various concretes having various
water contents. Other conditions are as follows: Irradiation time is one day. The source intensity of AmBe is 2.4×106 n/s. The composition of the concrete used by calculation is shown in Table 2.1. From theresult, a calibration curve of the gold activity to the water content in the concrete was obtained.
   Figure 2.2 shows the calibration curve obtained by the series simulations using MCNP5. Figure 2.3
shows an enlarged view of the calibration curve for the low water content region of 0 to 0.01 mol/cc. From
Fig. 2.3, as an exception concrete containing carbon which is a light atom (ANSI) and extremely highdensity concrete (heavy concrete) deviate slightly from the trend of other concretes. However, for otherconcretes, regardless of the density and composition, it can be seen that the gold activity changes depending
only on water content in the concrete. By using this calibration curve, it is possible to measure the watercontent in a concrete wall, the water content of which is not known, with a gold foil and AmBe neutron
source. When the thickness of concrete is 40 cm or more, the activity of gold foil is constant regardless ofthe thickness of concrete, so Fig. 2.2 can be used. On the contrary, when the thickness of concrete is 40
cm or less, the activity of gold foil changes depending on the thickness of concrete. Therefore, forconcrete with a thickness of 40 cm or less, it is necessary to create a calibration curve for each thickness.

Fig 2.1 Simulation system.

184- 184 -

JAEA-Conf 2021-001

Table 2.1 Composition of concretes. [3]Ordinary concrete

Serpentinite concrete

Heavy concrete

(wt%)

(wt%)

0.894

1.916

0.45

5.582

0

0

0

50.74

49.33950.53450.41531.392

Na

0

0

1.498

0.062

0

Mg

0.115

0.209

0.698

16.9

0.047

Al

0.446

0.511

5.501

1.28

0.199

Si

38.60618.808

28.8

15.5

2.982

S

0.07

0.082

0.304

0.016

1.936

K

0

0

1.798

0.077

0

Ca

6.869

24.949

7.692

6.95

4.081

Ti

0

0

0

0.005

0

Mn

0

0

0

0.79

0

Fe

2.738

0

2.281

6.8

58.913

Ni

0

0.312

0

0

0

Total

100

100

100

100

100

2.05

2.33

2.24

2.275

3.35

JAERI

ANSI

JRR-4

(wt%)

(wt%)

(wt%)

H

0.416

0.208

C

0

O

density(g/cc)

185- 185 -

JAEA-Conf 2021-001

Activity of gold foil (Bq)







-$(5,
$16,
-55





+HDY\FRQFUHWH
6HUSHQWLQWHFRQFUHWH












Water content (mol/cc)

Fig 2.2 Calibration curves of gold activity to water content.

Activity of gold foil (Bq)




-$(5,

$16,



-55
+HDY\FRQFUHWH



6HUSHQWLQWHFRQFUHWH














Water content (mol/cc)

Fig 2.3 Calibration curves for low water content.
3. Experiment
In order to confirm the validity of the present technique, experiments were performed with four concrete
samples having different water contents, which were made from only cement and water, meaning they haveno aggregate. An example of the experimental system is shown in Fig. 3.1. Four concretes made very
carefully by ourselves have water contents as 0.0209, 0.0241, 0.0267 and 0.0272 mol/cc. As a way to know
the water content accurately, we measured the mass ratio of cement and water before mixing. Next, we mixed
cement and water, and we measured the mass of the concrete before it hardens. After that, the water content
in the concrete before solidification is measured by multiplying the mass and the mass ratio of water andwater before mixing. Finally, the difference between the mass of the concrete after solidification and the mass
186
- 186 -

JAEA-Conf 2021-001

of the concrete before solidification is measured, and the difference is the amount of evaporation of water,
and the water content in the concrete is obtained by subtracting that amount. The densities of the four
concretes are 2.09, 2.05, 2.03, and 2.04 g/cc. The ratio of the amount of substance of four concretes isshown in Table .1, .2, .3 and .4. The size of concretes is 40 cm in length, 40 cm in width, and 40 cm inheight. A gold foil and Am-Be neutron source were placed on the concrete as shown in Fig. 3.1, and a gold
foil was activated on each concrete by neutron irradiation with the Am-Be neutron source for one day. The
intensity of Am-Be source is 2.4×106 n/s. We measured the activation of each gold foil with agermanium semiconductor detector. The gold activities obtained by the experiments were compared withthe predicted gold activities.

Fig 3.1 Experimental system.
7DEOH  5DWLR RI WKH DPRXQW RI VXEVWDQFH LQ FRQFUHWH  PROFF
HOHPHQW

+

2

6L

$O

)H

&D

0J

6

1D

.

$PRXQWRI





















VXEVWDQFH 

7DEOH  5DWLR RI WKH DPRXQW RI VXEVWDQFH LQ FRQFUHWH  PROFF
HOHPHQW

+

2

6L

$O

)H

&D

0J

6

1D

.

$PRXQWRI





















VXEVWDQFH 

7DEOH  5DWLR RI WKH DPRXQW RI VXEVWDQFH LQ FRQFUHWH  PROFF
HOHPHQW

+

2

6L

$O

)H

&D

0J

6

1D

.

$PRXQWRI





















VXEVWDQFH 

187- 187 -

JAEA-Conf 2021-001

7DEOH 5DWLRRIWKHDPRXQWRIVXEVWDQFHLQFRQFUHWH PROFF 
HOHPHQW

+

2

6L

$O

)H

&D

0J

6

1D

.

$PRXQWRI



















VXEVWDQFH  

4. Results)LJXUH  VKRZV WKH UHVXOW RI FRPSDULQJ WKH H[SHULPHQWDO YDOXH RI WKH JROG DFWLYLW\ ZLWK WKH
FDOFXODWHG YDOXH $V D UHVXOW WKH FDOFXODWHG DQG H[SHULPHQWDO YDOXHV DJUHH ZHOO ZLWKLQ WKHH[SHULPHQWDO HUURUV ,Q WKH QH[W VWHS ZH SODQ WR FDUU\ RXW H[SHULPHQWV ZLWK UHDO FRQFUHWHV ZLWKDJJUHJDWHVDQGWKHUHDIWHUPHDVXUHDUHDOFRQFUHWHZDOOLQRXUIDFLOLW\2.7$9,$1)RUWKDWSXUSRVHQRZZH
DUH H[DPLQLQJ KRZ WR IL[ WKH UHDO QXPEHU RI K\GURJHQV LQ FRQFUHWH IRU YDOLGDWLRQ RI WKH SUHVHQWO\SURSRVHGPHWKRG
Activity of gold foil (Bq)





WKHRUHWLFDO




YDOXH










Water content (mol/cc)

Fig 4.1 Experiment result.
5. Conclusion
It was confirmed from the experiments that water content could be estimated by the present nondestructive
measurement technique for samples made of cement and water.
In the next step, we will confirm the validity for aggregate concretes, concretes containing carbon andheavy concretes. Finally, we will apply to a real concrete wall in an actual nuclear facility.
References[1] Y. Nishiyama, et al., Nondestructive Determination of Water Content in Concrete by Foil Activation
Method-Feasibility study by Numerical Simulation-, JAEA-Conf 2017-001, 2018, pp.211-217.
[2] Los Alamos National Laboratory, A General Monte Carlo N-Particle Transport Code ver.5, 2003.
[3] D. Ito, Monte Carlo Calculation Hand Book, AESJ, 2006, p.224.

188- 188 -

JAEA-Conf 2021-001

 Comparison of double-differential cross sections between
JENDL/PD-2016.1 and experimental data for photo-neutron production of
medium-heavy nuclei at 16.6 MeV*T.K.Tuyet1, Y.Sakaki2, T.Sanami1,2, H.Yamazaki1,2, T.Itoga3, A.Takeuchi1, S.Miyamoto4 and Y.Asano2
1
SOKENDAI, Shonan Village, Hayama, Kanagawa 240-0193 Japan
2

KEK, 1-1 Oho, Tsukuba-shi, Ibaraki-ken 305-0801 JapanJASRI, 1-1-2, Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1205 Japan

3

University of Hyogo, 1-1-2, Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1205 Japan
Email: tuyet@post.kek.jp

4

Abstract: Understanding the photoneutrons' production from high-energy photons plays animportant role in accelerators' shielding design. We measured the double differential crosssections (DDX) for the (γ,xn) with 16.6 MeV polarized photons on Pb, Au, Sn, Cu, Fe, and Ti
targets and observed the low-energy and high-energy components on the neutron energy spectra.
In this work, we present the first comparison between the DDXs from JENDL/PD-2016.1, usedin Monte Carlo simulation tools to evaluate dose rate. There is a disagreement between the
JENDL/PD-2016.1 and experimental data. The photoneutron's low energy component agrees with
the JENDL/PD-2016.1, while the high-energy component does not.

1. Introduction
In an electron accelerator, high-energy photons can be produced as bremsstrahlung radiations.
These photons can interact with surrounding accelerator components, and via the photonuclear reaction,and produce secondary particles including neutrons. The double differential cross-section (DDX) of thephotoneutron is an essential quantity for radiation shielding and shielding calculation of the electron
accelerator design.
Until now, there are researches about photo-neutrons production in photonuclear reaction [1-4].
In the previous study of our research group [1], photoneutrons' energy spectra produced by the reactionof 16.6 MeV polarized photons on the Pb, Au, Sn, Cu, Fe, and Ti targets were measured at various angles.
The low-energy and high-energy components were identified in the energy spectra [1]. The angular
distribution of the low-energy component showed isotropic, while the high-energy component showeda dependence on the interaction angle between photon polarization and neutron emission [1].
The evaluated nuclear data library is used in simulation tools (such as PHITS, which is mentioned
in section 3) for shielding calculation and particle transportation. Comparison between the experimental
data and the evaluated data on DDXs of medium to heavy targets provides new information on photoneutron energy and angular distribution in addition to show contributions from evaporation and preequilibrium processes separately.

189- 189 -

JAEA-Conf 2021-001

2. Experiment
The experiment was performed at NewSUBARU-BL01, Hyogo, Japan. The details of ourexperimental setup were mentioned in Ref. [1]. Figure 1 indicates a detector system and setup ofphotoneutron measurement.

Plastic
targetFigure 1. The experimental setup of the photo-neutron measurement
In this measurement, we determined the photoneutron production per incident LCS photon. We
placed a plastic scintillator, with 0.5 cm thickness and 10 cm2 surface area, at 179.7 cm upstream fromthe target to estimate the number of incidents LCS photons. The cylindrical-shaped targets of Pb, Au,
Sn, Cu, Fe, and Ti, with 1 cm diameter and 1-4 cm thicknesses, were prepared in this experiment. The
LCS photons interact with the prepared targets and generate neutrons. We placed six 12.7 cmuI12.7
cmL cylindrical detector filled with NE213 organic liquid scintillator at different angles 30, 60, 90,
120, 150 (horizontally), and 90 (vertically), with respect to the photon beam axis. The distancesfrom the target center to the detectors ranged from 60 to 90 cm. As the neutron detector was sensitive
to both photoneutrons and background gamma radiations, a pulse shape discrimination (PSD)
method was employed. The time-of-flight (TOF) technique was employed to measure the neutronenergy. A VME-based data acquisition (DAQ) system was set up to collect the tail and full charges ofNE213’s signals by using a QDC module and measure the time difference between the LCS photon
and NE213 detector by using a TDC module. The energy deposited in the plastic scintillator was alsomeasured by our DAQ.
190
- 190 -

JAEA-Conf 2021-001

The neutron was distinguished from gamma events by a two-dimensional plot of time-of-flight vs ratioof light outputs from slow and total gates (Slow/Total). Figure 2 displays neutron-gamma events
separation. Figure 3 indicates neutron-gamma time-of-flight spectra after neutron-gamma events
separation. An energy threshold of 0.25 MeVee employed in our data was determined by energy
calibration using gamma radiations of 137Cs, 22Na, and 60Co.

Figure 2. Separation of neutron and gamma events by using ratio of pulse heigh slow and total gates

Figure 3. The neutron and gamma spectrum
We determined the efficiency of neutron detectors by measuring a 252Cf source and the SCINFULQMD simulation [7] to evaluate the total number of neutrons emitted from the target. The photon self191- 191 -

JAEA-Conf 2021-001

absorption factor inside the Au target was evaluated using the PHITS [8] simulation tool. With our setup,
we obtained a time resolution of 0.83 ns at gamma peak and a neutron’s energy resolution of less than10%.
The experimental data was obtained by using the polarized photon. In this work, we presented the
DDXs, which were obtained by detectors at vertical 90 degrees and horizontal 60 degrees (H60) to
minimize the polarization effect of the photon.

3. Evaluated nuclear data library and PHITS calculation
In this work, the DDXs from the evaluated nuclear data library and PHITS calculation arecompared with the experimental data. The DDXs were extracted from JENDL/PD-2004 andJENDL/PD-2016.1 library by our python-based software. The abundances of each target's isotopes wereconsidered in calculating the DDXs from the JENDL/PD-2016.1 library. Because we experimented
using the monoenergetic 16.6 MeV incident photons, the JENDL/PD-2016.1 DDXs of the incident
photon’s energy within 16 MeV – 17 MeV were taken average to yield the spectrum of the library thatshould be compared to the experimental data.
We used PHITS to calculate the DDX of photoneutron produced by the 16.95 MeV photons
incident on the Au, Pb, Sn, Cu, Fe, and Ti, which were natural targets. This energy was equal to the
maximum energy used in the experiment. The targets were cylindrical in this simulation with bothdiameter and thickness of 5 μm to remove the self-absorption effect due to the target’s thickness. This
self-absorption effect was considered in the experiment normalizing the DDX with the photon andneutron attenuation factors. The DDX was obtained on a detector cylinder, with both diameter andthickness of 12.7 cm, placed at 90 degrees and 60 cm away from the target.

4. Result and discussion
Figure 4 shows DDXs obtained from the experiment, the evaluated nuclear data libraries, the
PHITS calculation for the Au target. The circles indicate the experimental data at horizontal 60o (H60),
and the squares are the data at vertical 90o (V90). The experimental spectra indicate the low and highenergy components.
The black and blue lines are PHITS results (version 3.16) and JENDL/PD-2004, respectively. The
PHITS code has used the reaction cross-section from JENDL/PD-2004 and the Generalized Evaporation
Model (GEM) to generate energy spectra. Different models predict the different DDXs, PHITS [9] has
used the GEM, while JENDL/PD-2004 [10] has used exciton model-based code, CCONE, to produce
the DDXs of photo-neutron. The both spectra are not consistent with the experimental spectra, the highenergy component was not reproduced by the PHITS and JENDL/PD-2004. In addition to this, the slopeof the PHITS spectrum is lower than the experimental spectra.
The red line is the DDXs from JENDL/PD-2016.1. In this comparison, JENDL/PD-2016.1
produced the energy distribution in low energy, whereas this model cannot explain the high-energy
component.
A maximum neutron energy was determined by subtracting Qvalue of the (J,xn) reaction from thephoton energy. The maximum energy of results from the evaluated nuclear data and PHITS calculation
are lower than the experimental data. The maximum energy in the JENDL and PHITS have been
calculated using exactly the Q-value of the photonuclear reaction. In the photo-neutron measurement,
192- 192 -

JAEA-Conf 2021-001

DDX [barn/MeV/Sr]

that was impacted by energy resolution of neutron and the incident photon. The comparison of othertargets is similar to that of Au.
In this comparison, PHITS simulation does not produce the high-energy component, in spite of
the good agreement in the low-energy region below 4 MeV. Besides, the evaluated nuclear data library
could not reproduce the high-energy region.

Figure 4. Results of PHITS, evaluated nuclear data libraries and experiment for the DDXs of
197
Au(J,xn)

5. Conclusion
We compared the double differential cross-section from the evaluated nuclear data library(JENDL/PD-2016.1) and the experiment. The results show disagreement between JENDL/PD-2016.1
and the experiment in high energy region. Thus, a model to reproduce the high energy component should
be included in the simulation. To develop a model of high prediction power, further measurement on
DDX is strongly desired for various targets and energies.

References>@ Tuyet T.K., Sanami T., Yamazaki H., et al. Energy and angular distribution of photo-neutronsfor 16.6 MeV polarized photon on medium–heavy targets, Nucl. Instrum. Methods A 989(2021) 164965.
>@ Kirihara Y., Nakashima H., Sanami T., et al. Neutron emission spectrum from gold excitedwith 16.6 MeV linearly polarized monoenergetic photons, J. Nucl. Sci. Technol. 57 (2020) 444.

193
- 193 -

JAEA-Conf 2021-001>@ Horikawa K., Miyamoto S., Mochizuki T., et al. Neutron angular distribution in (γ, n) reactionswith linearly polarized γ -ray beam generated by laser Compton scattering Phys. Lett B 737(2014)109.
>@ Agodi A. Nuovo Cimento, 5, (1957) 21 (1).
>@ Asano Y., Miyamoto S. Shielding design of laser electron photon beamlines at SPring-8 Prog
NuclSci Tech (2014) 252.
>@ Miyamoto S., Asano Y., Amano S., et al. Laser Compton back-scattering gamma-ray beamline
onNewSUBARU Radiat Meas. 41 (2) (2007) S179.
>@ Satoh D., Kunieda S., Iwamoto Y., et al. Development of SCINFUL-QMD code to calculatetheneutron detection efficiencies for liquid organic scintillator up to 3 GeV J. of Nucl Sci
Tech 39(2014) 657.
>@ Sato T., Iwamoto Y., Hashimoto S., et al. Features of Particle and Heavy Ion Transport code
System, J. Nucl. Sci. Technol. 55 (2018) 684.
>@ Sato T., Niita K., Matsuda N., et al., Particle and Heavy Ion Transport Code System, PHITS,
version 2.52, J. Nucl. Sci. Technol. 50 (2013) 913–923.
>@ Iwamoto N., Kosako K., Murata T., Photonuclear Data File JAEA-Conf 2016-004 (2016) 53-58.

194- 194 -

JAEA-Conf 2021-001

 Development of Evaluation Method of Uncertainty of Radioactivity
by Propagating Nuclear Data Covariance for Clearance Verification in
Decommissioning of Nuclear Power Plants

Tatsuki AMITANI1, Tsunenori INAKURA1, Naoki YAMANO1, Ken-ichi TANAKA2,
Chikako ISHIZUKA 1, Masato WATANABE3, Ryoji MIZUNO4, Satoshi CHIBA 1*
1

Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan

2 The Institute of Applied Energy, 1-14-2 Nishi-shimbashi, Minato-ku, Tokyo, 105-0003, Japan
3

Chubu Electric Power Co., Inc., 1 Higashi-shincho, Higashi-ku, Nagoya, Aichi, 461-8680, Japan
4

Chuden CTI Co., Ltd., 1-3-10 Higashi-sakura, Higashi-ku, Nagoya, Aichi, 461-0005, Japan*Email: chiba.satoshi@nr.titech.ac.jp

To optimize the disposal of low-level radioactive wastes originating from the decommissioning of
nuclear facilities, required are 1) a reliable assessment of the radioactivity level by calculations andmeasurements and 2) a rational estimate of uncertainties of those results for the classification of theradioactive waste. We established a procedure to estimate uncertainties of a radioactivity concentration
required in the clearance verification by evaluating and propagating covariance of nuclear data properly.
For this aim, we estimated covariance of neutron cross sections of nuclides that account for over 90 % in
the sum of D/C of concrete materials and carbon steels. Here, D stands for the radioactivity concentration,
and C stands for the clearance level. The covariance of nuclear data was estimated by employing a
propagation of uncertainties of nuclear model parameters in the resonance and smooth regions by a
combination of nuclear model codes implemented in T6. Then, we developed a new method to calculate
uncertainty of the radioactivity by "Total Monte Carlo" method by connecting randomly perturbed ENDF6 format files generated by T6 to NJOY2016, and random 1-group activation cross sections were inserted
to ORIGEN2 in ORLIBJ40. It was concluded that the uncertainty of the radioactivity due to that of nuclear
data for nuclides which dominate the ΣD/C is of the order of 0.12 to 1.2%, which is sufficiently smaller
than the uncertainty of the radioactivity originating from that of the neutron flux.

1. Background and Purpose
At present, more than 20 nuclear power plants are either in the process of decommission or planned
to be decommissioned in near future in Japan. Therefore, decommissioning will become an important
activity in nuclear industry, so the procedure must be standardized. Decommissioning of nuclear power
plants produces huge amount of low-level radioactive waste. Radioactive wastes with extremely low
radioactivity concentrations and therefore having negligible impact to general public are referred to asclearance wastes. They can be reused and disposed of in the same way as general industrial waste withthe confirmation and permission of regulation authority. Promotion of clearance reduces the195- 195 -

JAEA-Conf 2021-001

environmental burdens and hence accomplishes streamlining and facilitating decommissioning in aproper way.
To be classified as clearance wastes, ΣD/C, sum of D/C by each specified nucleus, must be lower
than 1. Here, D stands for radioactivity concentration, and C stands for clearance level. In near future,
Nuclear Regulation Authority will stipulate that the uncertainty of radioactivity concentration must be
considered as a part of clearance procedure [1]. Therefore, it is required to establish a method to evaluate
the radioactivity concentration having rational uncertainty.
Uncertainty of radioactivity concentration depends on uncertainty of three factors, (1) nuclide
composition of material, (2) neutron irradiation condition and (3) nuclear data. Uncertainty of nuclear
data, namely, covariance data, was not considered in previous clearance studies. On the other hand, while
nuclear data library JENDL-4.0 that is frequently used for radioactivation calculation in Japan has nuclear
data for 406 nuclides, only 95 of them have covariance data. Evaluation of uncertainty of radioactivity
cannot be performed correctly without covariance data. For example, it is known that simple square sum
propagation of variance data gives underestimation of the uncertainty when the off-diagonal elements ofthe covariance matrix are positive, while it gives overestimation when the off-diagonal elements arenegative. Accurate estimation of the uncertainty of the radioactivity is possible only when the fullcovariance matrix is taken into consideration. For this reason, considering covariance data in uncertainty
evaluation is essentially important.
The purpose of this study is to establish a method to estimate the covariance data for nuclides without
covariance data in JENDL-4.0, and also to construct a method to quantitatively evaluate the effect of
uncertainty of nuclear data in the calculation of radioactivity by connecting to radioactivation calculation.

2. Developed evaluation method
As a method to quantitatively evaluate the influence of uncertainty in nuclear data, we developed anevaluation method using the TMC (Total Monte Carlo) method, which incorporates calculations by the
nuclear data evaluation code group T6 [2]. Figure 1 shows our evaluation method.
T6 consists of 6 codes (TASMAN, TALYS, TARES, TEFAL, TANES, TAFIS) and produces
nuclear data library. In this study, we used 4 codes in T6, TALYS, TARES, TASMAN and TEFAL (Table1). T6 calculation generates perturbed cross sections in ENDF-6 format file. These files are denoted as
random files. TMC calculation is the process of performing radioactivation calculation using ORLIBJ40
with these random files as input, and then statistically processing the result.
As preparation of T6 calculation, (1) reproduction of cross section in JENDL-4.0 and (2) adjustment
of distributions of model parameters for random calculation are needed. For (1), resonance parameters in
JENDL-4.0 were used to calculate cross sections in the resonance region with TARES and parameters
including optical model parameters are adjusted manually to calculate cross sections in the continuous
region with TALYS. For (2), uncertainties of resonance parameters evaluated by Mughabghab [3, 4] were
employed in the resonance region. Uncertainties of negative resonances were adjusted to reproduce
uncertainty of the thermal cross section. On the other hand, TALYS improves parameter distributions foreach random calculation based on Bayesian Monte Carlo (BMC) method. The posterior distribution
obtained by the BMC method starting from a uniform distribution given as the prior distribution was usedas the parameter distribution in the main calculation. After configurating the above setting, 1,000 random
files were produced by 1,000 random calculations as the main calculation.
In the TMC calculation, the random files were processed by NJOY2016 and then effective one-group196- 196 -

JAEA-Conf 2021-001

cross section was generated for each random file using neutron flux data. Then, it was incorporated into
the one-group cross section library set ORLIBJ40, and ORIGEN2 was used to calculate the radioactivity.
This procedure was repeated for the number of random files, and the results were statistically processedto obtain the mean value and standard deviation.

Figure 1 Overview of developed evaluation method
Table 1 Codes in T6 used in this study
TALYS

a nuclear reaction code to calculate cross sections in the continuous region.

TARES

a code to generate resonance cross sections.

TASMANa code for production of covariance data using result of TALYS and TARES.

TEFAL

a code for the translation of the nuclear reaction results from TALYS, TARES andTASMAN into ENDF-6 formatted nuclear data libraries.

3. Calculation Result of Covariance with T6
The nuclides to be evaluated were selected by performing calculation of radioactivity by ORLIBJ40.
The assumed plant was Hamaoka unit-1. Evaluation position was located at 30 cm depth from the surfaceof the concrete of the RSW (Reactor Shielding Wall) at the center height of the reactor core. Materials
were general concrete material (density = 2.3 g/cm 3) and carbon steel of primary containment vessel(PCV) (density = 7.86 g/cm3). Material composition data and neutron flux data ware provided from Chubu
Electric Power Co., Inc. Figure 2 shows neutron flux at the evaluation point. Effective full power year
(EFPY) is 16.2 years. As a result of activation calculation, 60Co and 152Eu were found to be the dominantradionuclides. Therefore, their parent nuclides, 59Co and 151Eu, were selected as the nuclides to beevaluated.
Random calculations were carried out by reproducing the cross sections of JENDL-4.0 for theevaluated nuclides and adjusting the parameter distribution according to the procedure shown in Section197- 197 -

JAEA-Conf 2021-001

2. The top graph in figure 3 shows perturbed 151Eu(n, γ)152Eu cross sections generated T6. The bottom
graph in Figure 3 shows the relative standard deviation when the generated cross sections were groupedby the VITAMIN-B6 structure and statistically processed.
Figure 4 shows correlation matrix of (n, γ) cross section of 151Eu. In 1/v region, correlation is strongly
positive since the energy-dependence of the cross section is fixed. On the other hand, correlation is weakand complex in resonance region. Correlation between continuous and resonance regions is zero because
TALYS and TARES are independent calculations of each other. Similarly, we also calculated correlations
between different reactions for calculations, including neutron transport calculation, other than this study.

Figure 2 Neutron flux in the concrete 30 cm deep from the surface of the RSW at the center heightof the reactor core (VITAMIN-B6 structure)

Figure 3 Perturbed 151Eu(n, γ)152Eu cross sections generated by 1000 times T6 calculation
and relative standard deviation
198- 198 -

JAEA-Conf 2021-001

Figure 4 Correlation matrix of (n, γ) cross section of 151Eu calculated with T6

4. Evaluation of Uncertainty of Radioactivity
We calculated D/C uncertainty due to nuclear data by TMC calculation. Figure 5 shows calculated
D/C and relative standard deviation of that of dominant nuclides in concrete. From the result, Δ(D/C) of
Co is 0.12 % and that of 152Eu is 1.2 %. Figure 6 shows similar calculation result in carbon steel (PCV).
From the result, Δ(D/C) of 60Co is 0.12 %. These results are smaller than uncertainty due to neutron flux
60

data, which is dozens % [5]. Therefore, it can be concluded that the uncertainty due to nuclear data is not
major factor in the uncertainty of the radioactivity.

Figure 5 D/C and relative standard deviation of D/C (Δ(D/C)) of dominant nuclides in concrete(left: 60Co, right: 152Eu)

199- 199 -

JAEA-Conf 2021-001

Figure 6 D/C and Δ(D/C) of dominant nuclide, 60Co, in carbon steel

5. Conclusion
In order to contribute to the rationalization of the disposal of dismantled waste generated in thedecommissioning of nuclear power plants, we developed quantitative evaluation method of theuncertainty in radioactivity due to uncertainty of nuclear data. Then, we applied our evaluation method
to Hamaoka unit-1 and evaluated the uncertainty of D/C of important nuclides in clearance verification,
60Co and 152Eu.
Our evaluation method consists of T6 calculation and TMC calculation. T6 calculation generates
perturbed cross sections in ENDF-6 format file for data that reproduces JENDL-4.0. TMC calculationis the process of performing activation calculation using ORLIBJ40 with generated cross sections as
input, and then statistically processing the result.
We applied developed method to Hamaoka unit-1 and calculated uncertainty of D/C of dominant
nuclides in concrete material and carbon steel. From the result, uncertainty of 60Co due to nuclear data is
0.12 % and that of 152Eu is 1.2 %. They are smaller than uncertainty due to neutron flux data, which isdozens %. Therefore, it can be concluded that the uncertainty due to nuclear data is not major factor in
the uncertainty of the radioactivity.

References
1)
2)
3)
4)
5)

Nuclear Regulation Authority, ࢡࣜ࢔ࣛࣥࢫࡢ ᐃཬࡧホ౯ࡢ᪉ἲࡢㄆྍ࡟ಀࡿෆつࡢぢ┤ࡋ᪉㔪࡟ࡘ࠸࡚, (2019).
A.J. Koning and D. Rochman, Modern Nuclear Data Evaluation with the TALYS Code System,
Nuclear Data Sheets 113, 2841 (2012).
S.F. Mughabghab, Atlas of Neutron Resonances: Volume 1: Resonance Properties and Thermal
Cross Sections Z=1-60, 6th ed., Elsevier, New York (2018).
S.F. Mughabghab, Atlas of Neutron Resonances: Volume 2: Resonance Properties and Thermal
Cross Sections Z=61-102, 6th ed., Elsevier, New York (2018).
K. Yokoi, T. Endo, A. Yamamoto, R. Mizuno and Y. Kimura, Uncertainty Quantification of
Activation Due to Cross Section Data in Neutron Shielding Calculation, Trans. Am. Nucl. Soc.,
115, pp.1085-1087 (2016).

Acknowledgements
This study includes results of collaborative study on “ࢡࣜ࢔ࣛࣥࢫ᳨ㄆ࡛ồࡵࡽࢀࡿᨺᑕ⬟ホ౯ࡢ୙☜࠿ࡉࡢ◊✲” between Tokyo Institute of Technology and Chubu Electric Power Co., Inc.
200
- 200 -

JAEA-Conf 2021-001

4UVEZPODIBSBDUFSJTUJDTPGOFVUSPOBOEѝSBZmFMET
BU DPNQBDU OFVUSPO TPVSDF 3"/4** GBDJMJUZ CZ
TJNVMBUJPO CZ UIF 1)*54 DPEF
,FOUB46(*63"p  :VKJSP*,&%"  5PNPIJSP,0#":"4)* ,VOJIJSP'6+*5" /PCVIJSP4)*(:0 ,BOFOPCV5"/"," BOE:PTIJF05",&

3*,&//JTIJOB$FOUFS 3*,&/ )JSPTBXB 8BLP 4BJUBNB +BQBO
%FQBSUNFOUPG"QQMJFE2VBOUVN1IZTJDTBOE/VDMFBS&OHJOFFSJOH ,ZVTIV6OJWFSTJUZ .PUPPLB /JTIJLV 'VLVPLB +BQBO

3*,&/$FOUFSGPS"EWBODFE1IPUPOJDT 3*,&/ )JSPTBXB 8BLP 4BJUBNB +BQBO
+1"3$$FOUFS +BQBO "UPNJD&OFSHZ"HFODZ 4IJSBLBUB 5PLBJNVSB /BLBHVO

†*CBSBLJ +BQBO&NBJM LFOUBTVHJIBSB!SJLFOKQ

Aiming at development of a compact neutron source for non-destructive inspection,
RIKEN Accelerator-driven compact Neutron Source-II (RANS-II), based on the p-Li reaction with 2.49 MeV proton beam, has been under beam commissioning. As it is important
to assess the validity of neutrons at the RANS-II facility, radiation ﬁelds in a rather narrowexperimental room has been studied. The characteristics of neutron and γ-ray are calculated
by simulation with Particle and Heavy Ion Transport code System (PHITS). As a result, except for a target station, neutrons and γ-rays distribute widely in the hall. The scatteredradiation could be the major contributor to the background events in the future experiments.
Thus, a collimator is designed to suppress the background radiation. In this article, we report
the radiation ﬁelds in the RANS-II hall and the eﬀectiveness of the collimator.

1

Introduction

RIKEN Accelerator-driven compact Neutron Source-II (RANS-II) has been under beam commissioning to demonstrate speciﬁc performance of the system[1]. At the RANS-II facility, neutrons
are produced via 7 Li(p, n)7 Be reaction with 2.49 MeV proton beam. Through the studies of neutrons generated at RANS-II, RIKEN has a prospect of realizing novel non-destructive neutron
inspection for infrastructures.
As prominent characteristics, RANS-II has the maximum neutron energy of 0.8 MeV, which
is lower than that of 5 MeV at RANS based on the 9 Be(p, n)9 B reaction with 7 MeV proton
injection[2]. Neutron at the RANS-II facility has extremely forward-favored angular distribution
with respect to the proton beam direction. Also, it should be emphasized that the RANS-II
system is installed in a relatively small space isolated by concrete shield with boron containment.
Accordingly, there should be quite large diﬀerences in neutronic performances between RANS-IIand RANS in terms of neutron spectrum and angular distributions. Prior to future experiments
at RANS-II, the simulation of radiation ﬁelds for neutron and γ-ray in the RANS-II experimental
hall plays a critical important role for designing experimental set-up in low background.
201- 201 -

JAEA-Conf 2021-001

In this paper, we report characteristics of dose rate in the experimental hall. Major sourceof background and adequacy of shielding are discussed in viewing requirement from future experiment. Also we have preliminary designed collimators to provide neutron beam for theexperiments. The eﬀect of collimator is discussed from quality of neutron beam proﬁle as well
as reduction of radiation background in the hall.

2

Simulation

2.1

Cross section data and simulation code

We have performed simulations to characterize radiation ﬁelds of RANS-II with the use of Particle and Heavy Ion Transport code System (PHITS)[3]. To calculate neutron production via the
7 Li(p, n)7 Be reaction, Evaluated Nuclear Data File/B-VII.0 (ENDF/B-VII.0)[4] is employed.
The cross section of ENDF/B-VII.0 is shown in Figure 1. Neutron energy spectra at six angles
with respect to proton beam direction with ENDF/B-VII.0 is depicted in Figure 2. We usean angular width of ±1.5◦ in the ﬁgure. According to Figure 2, characteristics of the maximum energy and the angler distributions of forward-favored are visible. Japanese EvaluatedNuclear Data Library-4.0 (JENDL-4.0)[5] and Livermore Evaluated Photon Data Library ’97(EPDL97)[6] is applied to calculate interactions of neutrons and γ-ray, respectively.
0.7

Flux [n/cm2/source]

Cross Section [barn]

0.6
0.5
0.4
0.3
0.2
0.1
0
1.4 1.6 1.8 2 2.2 2.4 2.6 2.8
Proton Energy [MeV]

3

×10−9
0.22
0°
0.2
30°
0.18
60°
0.16
90°
0.14
120°
0.12
150°
180°
0.1
0.08
0.06
0.04
0.02
00
0.2
0.4
0.6
0.8
Neutron Energy [MeV]1

Figure 2: Neutron energy spectra from 0◦ to
Figure 1: Cross section of 7 Li(p, n)7 Be reaction
180◦ at 30◦ intervals with respect to the proton
from ENDF/B-VII.0.
beam direction.

5BSHFU4UBUJPO$PMFNBOJUF
$PODSFUF
no. ="DDFMFSBUPS
1, y = 0.0000E+00#0XU
Air

x [cm]−600

Concrete
Fe−800

1SPUPO%JSFDUJPO

−1000
−1200

#VJMEJOH8BMM

Colem
olem
ole
le
lem
emanite ConcreteemColemanite
Pb
B_Pol
_Po
Po yethy
Po
eth
ethy
e
et
th
tthy
hyylene
h
len
ene
e
ne
n
e
B_Polyethylene

−500

0

z [cm]Polyey thyley ne
Polyethylene
Alminium
Almin
min
niiu
ium
um
u
m
vacuum
vacuu
cuu
ccu
uu
u
um
Cu
H2O

500

1000

Figure 3: Plan view of the calculation model for the RANS-II experimental hall. Accelerator
and target station of RANS-II are surrounded by concrete and partially colemanite concretewith boron.
202- 202 -

JAEA-Conf 2021-001

Model for simulation
no. = 1,QSPUPO

0.0000E+00

QSPUPO

−800

8BUFS

Airr
Fe
e

Pb
b
B_Polyethylene
B_Poly
_Poly
_P
Poly
P
oly
yethyle
eth
et
e
ethy
th
thyl
thyle
tthy
hyl
hyle
h
hy
y
yle
le
ene
ne
Polyethylene
Polyet
olye
ol
olyet
oly
o
llyet
yet
ye
y
e
etth
hyle
hy
hylen
hyl
hylene
ylen
y
ylene
lene
llen
en
en
ne
e
Cu
Alminium
Almini
lmin
lm
mini
min
m
in
n um
H2O
vacuum
acuu
acuum
acu
cu
uum
m

−850


−900
YDN
PQFOJOHT−350-JUBSHFU
−300

−250

−200

z [cm]

Figure 4: RANS-II target station.

/FVUSPO

106

−600

105

x [cm]

y=

104

−800

103
102

−1000

Dose[uSv/h@100uA]

Simpliﬁed model of the RANS-II experimental
hall, accelerator, target station in PHITS is illustrated in Figure 3. The size of the hall isabout 14 × 5.5 × 3.0 m3 . An enlarged viewof the target station is shown in Figure 4. The
lithium(Li) target is made by depositing thin Li
layer of about 100 μm on a 5 mm thick copper
substrate cooled by water in the target station.
The target station with all of the sides about
900 mm long has ﬁve layers, polyethylene(PE),lead(Pb), borated polyethylene with 10 % weightB2 O3 (BPE), lead and iron to reduce the radiation leakage. There is a hole with a 150 × 150
mm2 cross section in the forward direction. Calculations introduced in the following chapters
are performed with these systems.

x [cm]

2.2

101

−500

0

ĕSBZ

z [cm]

500

1000

106

−600

x [cm]

100

105
104

−800

103
102

−1000

Dose[uSv/h@100uA]

−1200

101

−1200

−500

0

z [cm]

500

1000

100

Figure 5: Dose rate distribution of neutrons and γ-rays at the RANS-II hall. The T-Track tallyin PHITS is used. The mesh width for both x and z axis is 100 mm in the calculation.

3

Result and discussion

3.1

Dose rate distribution

We assume 100 μA for the proton beam current at the Li target. Dose rate distribution of neutrons and γ-rays at the RANS-II hall is depicted in Figure 5. The dose conversion coeﬃcient[7]in PHITS is utilized in Figure 5. Along the downstream of the beam line, the highest dose
rate of neutrons is shown. Except locations near the neutron production target and along theproton beam direction, dose rate distribute uniformly. Around the side of the target station,
the dose rate is the order of 1.0 mSv/h and 0.1 mSv/h for neutron and γ-ray, respectively. For
the neutrons, the dose rate is caused by the scattered neutrons with the down stream concrete203- 203 -

JAEA-Conf 2021-001

walls. Dose rate of γ-ray is mainly attributed to γ-ray from the reactions between neutronsand elements in the concrete. The ratio of the component scattered from the concrete walls
is about 90% for both neutrons and γ-ray at the region. The scattered neutrons and γ-rays
become background events in the future experiments. Suppression of the background radiation
is important. Therefore, we have a plan to install a collimator in the target station to reduce
the excessive spread of the neutron beam introduced in the following chapter.

3.2

Collimatorx [cm]

To suppress the spread of neutrons, it is intended to insert−750
a collimator in the downstream
openings at the target station as−800
Airshown in Figure 6. There is avacuumFecylindrical cavity at the center ofPb−850
B_Polyethylene
the collimator. The length of the
PolyethyleneCucollimator is 530 mm. It is nec−900
AlminiumHOessary to examine the inﬂuenceof the collimator’s material and−950
EFUFDUPSJOTJNVMBUJPOYˏ
hole diameter for neutron sup−1000
pression capacity. The material
−400
−300
−200
of the collimator is assumed toz [cm]
be PE or BPE. The hole diameter is 10, 30 and 50 mm. At the
Figure 6: Target station with a PE collimator.
downstream of the target station,
detectors in simulation are aligned along a surface perpendicular to proton beam direction. Sizesof the detectors are 10 × 10 × 10 mm3 and 100 × 100 × 100 mm3 at the central region andoutside region, respectively. x’ axis is deﬁned as the axis along the detectors. The number ofneutrons is obtained by the T-Cross tally implemented in PHITS. The energy range for fast andthermal neutrons is set from 10−2 to 102 MeV and from 10−9 to 10−7 MeV, respectively.
2'BTUOFVUSPO

106

105

Flux [n/cm2/sec]@100 μA

Flux [n/cm2/sec]@100 μA

106

104
103
102

−100

−50

0
50
x' [cm]100

5IFSNBMOFVUSPO

105
104
103
102

−100

−50

0
50
x' [cm]100

Figure 7: Fast and thermal neutron ﬂux at the downstream. The horizontal axis means thevalue of x’. The vertical axis represents the ﬂux of neutrons.
204- 204 -

JAEA-Conf 2021-001

x [cm]The results of neutron ﬂux are shown in Figure 7. The black line stands for the result without
the collimator. The red line means the outcome for the PE collimator with the 10 mm cylinderhole. The other colors’ lines are similar to the red line. Because the PE or BPE collimator
has elements with small mass number, it is eﬀective for neutron suppression. According to theresults of fast neutrons, the suppression ability for the PE collimator is a little greater than thatfor BPE collimator. This is attributed to the greater amount of hydrogen in the PE collimatorthan BPE one. For thermal neutrons, the BPE collimator has much stronger power than the PE
collimator due to boron eﬀect. The result suggests that the BPE collimator is appropriate to
reduce the wide spreading of thermal neutrons. When the diameter of the collimator is 10 mm,
the number of neutrons is too suppressed to utilize for future experiments. The collimator with
30 mm hole is enough to provide sharp neutron beam because the fast and thermal neutron ﬂux
are roughly to be less than 1/100 at the outer region from x’ = 15 compared with the value atx’ = 0. Accordingly, we conclude that BPE collimator with 30 mm hole is suitable for neutron
suppression.
Because the γ-rays’ attenuation in materials depends on the−750
mass number, signiﬁcant eﬀect
for γ-ray of the BPE collimator−800
Air
is not expected. To control γvacuumFe
ray distribution, the material ofPb−850
B_Polyethylene
the collimator is changed to BPE
Polyethylene
Cu
and Pb as shown in Figure 8.
−900
AlminiumHO
The length of the Pb collimaEFUFDUPS−950
tor is 230 mm. The minimum
Yˏ
JOTJNVMBUJPO
and maximum energy in the tally−1000
is ﬁxed to be from 10−9 to 102
−400
−300
−200
z [cm]
MeV for both neutrons and γrays. The other conditions for
Figure 8: Target station with a BPE + Pb collimator.
the calculation are the same asabove calculation.
2/FVUSPO

105
104
103
102

−100

−50

0
50
x' [cm]

ĕSBZ

106

Flux [n/cm2/sec]@100 μA

Flux [n/cm2/sec]@100 μA

106

100

105
104
103
102

−100

−50

0
50
x' [cm]100

Figure 9: Neutron and γ-ray ﬂux at the downstream.
205- 205 -

JAEA-Conf 2021-001

The calculation results with BPE + Pb collimator are depicted in Figure 9. The black, redand green line stands for the result without the collimator, that with the BPE collimator andthat with the BPE + Pb collimator, respectively. According to the neutron result, the neutron
ﬂux with the BPE and Pb collimator is a little greater than that of only BPE collimator due
to the reduction of BPE area of the collimator. On the other hand, great contribution for γ-ray
ﬂux is observed. Compared with the value at the point of x’ = 0, γ-ray ﬂux drops by about 5%
at the external area from x’ = 15.

4

Conclusion

The distribution of neutrons and γ-rays in the RANS-II experimental hall are acquired withthe use of PHITS. The interactions of neutrons and γ-rays are described by JENDL-4.0 and
EPDL97, respectively. Due to the openings at the downstream of the target station and small
experimental hall, neutrons and γ-rays spread widely in the hall. When the BPE and Pb
collimator is installed in the openings of the target station, The RANS-II facility can supply
sharp neutron beam with low background condition.

References[1] Kobayashi T, et al., Completion of a new accelerator-driven compact neutron source prototype RANS-II for on-site use, Nucl. Instr. Methods, Phys. Res., Sect. A, vol. 994, 2021,
pp. 1-6, 165091.
[2] Otake Y, RIKEN Compact Neutron Systems with Fast and Slow Neutrons, Plasma FusionRes., vol. 13, 2018, 2401017.
[3] Sato T, et al., Features of Particle and Heavy Ion Transport code System (PHITS) version
3.02, J. Nucl. Sci. Technol., vol. 55, 2018, pp. 684-690.
[4] Chadwick, M.B., et al., ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Libraryfor Nuclear Science and Technology, Nucl. Data Sheets, vol. 107, 2006, pp. 2931-3060.
[5] Shibata K, et al., JENDL-4.0: A New Library for Nuclear Science and Engineering, J. Nucl.
Sci. Technol., vol. 48, 2011, pp. 1-30.
[6] Cullen, D.E., et al., ”EPDL97: the Evaluated Photon Data Library, ’97 Version”, UCRL50400, Vol. 6, Rev. 5, Lawrence Livermore National Laboratory (1997).
[7] Sakamoto Y et al., Dose conversion coeﬃcients for high-energy photons, electrons, neutronsand protons, JAERI-1345, 2003 [in Japanese].

Acknowledgement
The PHITS calculations were performed using the supercomputer system of RIKEN. This work
was partially supported by Council for Science, Technology, and Innovation (CSTI), Crossministerial Strategic Innovation Promotion Program (SIP), ”Infrastructure maintenance, renovation and management” (Funding agency: JST) and also partially supported by ”Upgrading
and sophistication of compact and high brightness neutron sysytem for high-degree applicationof industrial use” Photon and Quantum Basic Research Coordinated Development Programfrom the Ministry of Education, Culture, Sport, Science, and Technology, Japan.

206- 206 -

JAEA-Conf 2021-001

 Nuclide production cross section of natLu target
irradiated with 0.4-, 1.3-, 2.2-, and 3.0-GeV protons
Hayato TAKESHITA1,2, Shin-ichiro MEIGO2, Hiroki MATSUDA2, Hiroki IWAMOTO2,
Keita NAKANO2, Yukinobu WATANABE1, Fujio MAEKAWA2
1Department of Advanced Energy Engineering Science, Kyushu University2

J-PARC Center, Japan Atomic Energy Agency
email: takeshita.hayato.890@s.kyushu-u.ac.jp

Proton-induced nuclide production cross sections of natLu target were measured at incident energies of 0.4, 1.3,
2.2, and 3.0 GeV by means of the conventional activation method. The targets were irradiated by the proton beam
generated from the 3 GeV Rapid Cycling Synchrotron of Japan Proton Accelerator Research Complex. Gammarays emitted by the irradiated samples were detected by two high purity Ge detectors. The experimental data werecompared with model predictions to benchmark reaction models used in the simulation of particle transport inmatter, INCL4.6/GEM and INCL++/ABLA07.

1. Introduction
For the design of high-energy accelerator facilities such as accelerator-driven transmutation systems (ADSs)
and spallation neutron sources, reliable assessment of radioactivity in target and structural materials requires
sufficiently accurate estimation of the production yields of radioactive nuclides. Although a great deal of effort has
been devoted to studying the spallation reactions from both the theoretical and experimental [1, 2] perspectives,
the prediction powers of theoretical models are still insufficient. As for the experiments, relatively large
uncertainties (~10%) in the experimental data make it difficult to improve the theoretical models. To obtainaccurate experimental data required for improving the theoretical models, we have conducted a series of systematic
measurements of nuclide production cross sections for various targets using the 3 GeV Rapid Cycling Synchrotron(RCS) accelerator at the Japan Proton Accelerator Research Complex (J-PARC). Our previous experiments for Al,
Pb, and Bi targets [3,4] showed that a well-calibrated current transformer successfully reduced the uncertainty inthe beam current, which finally achieved approximately 3.6% as the minimum total uncertainty.
To improve theoretical reaction models, further experimental data are required in the GeV range where theexperimental data are insufficient. Recently, we have measured the nuclide production cross sections for Ho, Lu,
and Re at 0.4, 1.3, 2.2, and 3.0 GeV to meet the requirement. In this paper, we show preliminary results of natLu.
In addition, we compare the measured data with theoretical model calculations using INCL4.6/GEM [5, 6] andINCL++/ABLA07 [7, 8].

2. Experiment
The sample foils were assembled in four stacks as shown in Figure1. In each stack, Ho, Lu, and Re targets

207- 207 -

JAEA-Conf 2021-001

were put in order of increasing atomic number. To prevent the products from escaping to the other target, Al foils
were inserted between samples. All foils were 25 mm × 25 mm square and 0.1-mm thick. Four sets of stacks wereenclosed in 0.1-mm-thick Al containers, and were fixed on movable stages in a vacuum chamber, which was
installed in the beam dump line. Each stack was inserted to the irradiation position, and irradiated by proton beamwith energies of 0.4, 1.3, 2.2, and 3.0 GeV. The beam profiles and currents were monitored by multi-wire profile
monitors [9] installed in the beam transport line. Typical irradiation time was approximately 100 seconds.
After the irradiation, gamma-ray measurement was performed with two high-purity Ge detectors. Energy
calibration and determination of detection efficiency of the detectors were performed with standard gamma-ray
sources 137Cs, 60Co, 152Eu, and 241Am. The gamma-ray measurement was periodically performed with different
intervals ranging from 0.5 hours to 7 days. During the measurement, an acrylic spacer was placed between thesample and the detector to keep the geometrical detection efficiency constant.

Figure 1. Schematic drawing of a sample stack.

3. Data Analysis
3.1 Determination of the number of protons
During the experiment, the total number of protons irradiated to the samples was monitored by the multi-wire
profile monitors. However, a part of protons transits without bombarding the sample because of the spatial expanseof the proton beam. To determine accurately the number of protons that bombarded the sample foils, twodimensional activation distributions of the foils were taken by the FUJIFILM BAS-SR2040 imaging plate. Here,
we assumed that the activation distribution is identical to the proton-beam profile. Figure 2 shows an example of
the activation distributions of Lu target irradiated by 3.0-GeV protons. The proton-beam profile is wellapproximated by the two-dimensional gaussian:ଶሺ‫ ݔ‬െ ߤ௫ ሻଶ ൫‫ ݕ‬െ ߤ௬ ൯ʹߩሺ‫ ݔ‬െ ߤ௫ ሻ൫‫ ݕ‬െ ߤ௬ ൯ͳ݂ሺ‫ݔ‬ǡ ‫ݕ‬ሻ ൌ ൥െ
൝
൅
െ
ൡ൩ ǡ
ଶሻ
ଶ
ଶ
ଶ
ߪ
ߪ
ߪ௫ ߪ௬
ʹሺͳ
െ
ߩ
௫
௬
ʹߨߪ௫ ߪ௬ ඥͳ െ ߩܰሺͳሻwhere ܰ, ߤ௫ , ߤ௬ , ߪ௫ , ߪ௬ , and ߩ are the fitting parameters. By fitting the activation distribution, the number ofprotons that bombarded the sample, ܰ௣௥௢௧௢௡ , were determined byܰ௣௥௢௧௢௡ ൌ ܰ௧௢௧௔௟ ௣௥௢௧௢௡ ൈͳන ݂ሺ‫ݔ‬ǡ ‫ݕ‬ሻ݀‫ ݕ݀ݔ‬ǡܰ ௙௢௜௟

208- 208 -ሺʹሻ

JAEA-Conf 2021-001

where ܰ௧௢௧௔௟ ௣௥௢௧௢௡ ൌ ʹǤ͵Ͳ ൈ ͳͲଵସ was measured by the current transformer. For this correction, typicalcorrection factor, ܰ௣௥௢௧௢௡ Τܰ௧௢௧௔௟ ௣௥௢௧௢௡ was approximately 0.97.

Table 1. Number of protons bombarding the sample
Proton energy [GeV]ܰ௣௥௢௧௢௡

0.4

2.171014

1.3

2.261014

2.2

2.261014

3.0

2.231014

Figure 2. Example of activation
distribution taken by an imaging plate

3.2 Cross section determination
Figure 3 shows an example of the gamma-ray spectrum for 3.0-GeV proton irradiation. The number of
products at time ‫ ݐ‬after proton irradiation was obtained byܰ௣௥௢ௗ௨௖௧ ሺ‫ݐ‬ሻ ൌ‫ܥ‬ሺ‫ݐ‬ǡ ‫ݐ‬௠ ሻǡሺͳ െ ݁ ିఒ௧೘ ሻ‫ܫ‬ఊ ߝ௣ሺ͵ሻwhere ‫ܥ‬ሺ‫ݐ‬ǡ ‫ݐ‬௠ ሻ is the number of peak counts in a gamma line with the measurement time ‫ݐ‬௠ , ߣ is the decay
constant of the product nuclide, ‫ܫ‬ఊ is the gamma intensity, and ߝ௣ is the peak efficiency of the detector. Figure 4

shows some examples of decay curves obtained for 24Na and 172Lu. The fitting curve is expressed byܰ௣௥௢ௗ௨௖௧ ሺ‫ݐ‬ሻ ൌ ܰ௣௥௢ௗ௨௖௧ ሺ‫ ݐ‬ൌ Ͳሻ݁ ିఒ௧ ǡሺͶሻwhere the number of products at the end of proton irradiation, ܰ௣௥௢ௗ௨௖௧ ሺ‫ ݐ‬ൌ Ͳሻ , was determined as a fitting
parameter. Finally, the production cross section ߪ was obtained byߪൌܰ௣௥௢ௗ௨௖௧ ሺ‫ ݐ‬ൌ Ͳሻǡ݊ܰ௣௥௢௧௢௡

where ݊ is the areal number density of target nuclei in the sample foil.

Figure 3. Example of gamma-ray spectrum

Figure 4. Example of decay curve fitting209- 209 -ሺͷሻ

JAEA-Conf 2021-001

3.3 Correction for incoming and escape of reaction products
In the sample stack, Al foils were inserted to prevent the reaction products in the sample foil from escaping tothe other sample foils. However, light reaction products generated in the Al foil and other sample foils such as 7Be,
Na, and 24Na may escape to the neighboring foils. In this work, the contribution of product escape was corrected22

on the basis of the simulation by Particle and Heavy Ion Transport code System (PHITS) [10]. All input parameters
were set to default values. For proton-induced reaction, the INCL4.6/GEM model was used. Particle transport of
the reaction products including 7Be, 22Na, and 24Na was simulated by using the same sample stack geometry as in
the measurement. The simulation tallied the total number of the products of interest generated in the Lu foil (ܰ௣௥௢ )and the number of reaction products which finally stopped in the Lu foil by ion transport among the reaction

products generated in the Lu and neighboring Al foils ( ܰ௦௧௢௣ ). The latter number ܰ௦௧௢௣ corresponds toܰ௣௥௢ௗ௨௖௧ ሺ‫ ݐ‬ൌ Ͳሻ in Eq.(5). The correction factor for the Lu foil was defined as ܰ௖௢௥௥ ൌ ܰ௣௥௢ Τܰ௦௧௢௣ . In this work,
the correction was applied only for the 7Be production. It should be noted that the corrections for 22Na and 24Na
heavier than 7Be were negligibly small (less than 1%).
Table 2. Correction factors for 7Be produced in the Lu target
Proton energy [GeV]
0.4

ܰ௖௢௥௥

1.3

0.80

2.2

0.97

3.0

0.99

0.52

4. Results and Discussion
4.1 Comparison with model predictions
Figure 5 shows the production cross sections of 7Be, 24Na, 148Eu, and 172Lu. In the figure, the previous data
[11] are also plotted. The production cross sections of light nuclides, e.g. 7Be and 24Na, increase with increasing
incident proton energy. This could be because the residual nuclei generated after INC process have higher
excitation energy with increasing incident energy and are likely to emit nucleons and light ions including 7Be in
the subsequent evaporation processes. The INCL4.6/GEM calculation generally reproduced the energy
dependence of the cross sections except for 24Na. The INCL++/ABLA07 calculation showed good agreement withthe experimental values for 24Na, 148Eu, and 172Lu. Both the two model calculations underestimated the production
cross section of 7Be.

5. Summary and outlook
Nuclide production cross sections of natLu were measured by irradiation of 0.4, 1.3, 2.2, and 3.0-GeV protons
at J-PARC. In the report, we showed preliminary results of production cross sections for 7Be, 24Na, 148Eu, and
Lu. The present data is very useful for model improvement, because the cross section data of Lu target is very

172

limited. To investigate the prediction power of the above-mentioned models for 7Be production, 7Be production

210- 210 -

JAEA-Conf 2021-001

Figure 5. Experimental production cross sections for 7Be, 24Na, 148Eu, 172Lu produced by p + natLu reaction andmodel predictions by INCL4.6/GEM and INCL++/ABLA07. The subscripts ind. and cum. represent independentand cumulative cross sections. The experimental data were taken from [11]. The calculation results for 24Na by the
INCL4.6/GEM calculation was multiplied by 100. Our data shows statistical uncertainties, but included in the
maker.

Figure 6. The 7Be production cross sections for 25Mn, 27Co, 28Ni, 40Zr, and 71Lu measured at J-PARC and model
predictions by INCL4.6/GEM (a) and INCL++/ABLA07 (b). The statistical uncertainties are included in the maker.

211- 211 -

JAEA-Conf 2021-001

cross sections of Mn, Co, Ni, Zr, and Lu measured at J-PARC [12] were compared in Figure 6. It was found thatthe dependency of 7Be production cross sections on the target nuclide is weak. The model calculations
underestimate the experimental values as incident energy increases.
Model predictions with INCL4.6/GEM and INCL++/ABLA07 were compared with the measured data tovalidate their prediction powers. The INCL4.6/GEM generally reproduced the dependence of cross sections on
incident proton energy, but the calculated cross sections do not necessarily agree with the experimental ones. The
INCL++/ABLA07 model successfully reproduced the experimental data except for 7Be production. The
description of the two models should be improved to reproduce the 7Be production in the future.

References[1] Titarenko YE, Batyaev VF, Titarenko AY et al., Phys Atom. Nucl.2011;74(4):537 - 550.
[2] Michel R, Bodemann R, Busemann H et al., Nucl. Instrum. Meth. Phys. B 1997 Jan;129:153 - 193.
[3] Matsuda H, Meigo S, and Iwamoto H, J. Nucl. Sci. Technol. 2018 Apr;55(8):955 – 961.
[4] Matsuda H, Meigo S, and Iwamoto H, Maekawa F, EPJ Web Conf. 2020 239:06004.
[5] Boudard A, Cugnon J, David JC, et al. Phys Rev C. 2013 Jan;87:014606.
[6] Furihata S, Nucl. Instrum. Meth. B 2000;171:251 – 258.
[7] Mancusi D, Boudard A, Carbonell J et al., Phys. Rev. C 2015;91:034602.
[8] Kelic A, Ricciardi MV, and Schmidt KH, Proceedings of Joint ICTP-IAEA Advanced Workshop on Model
Codes for Spallation Reactions, ICTP Trieste, Italy 2008;181.
[9] Meigo S, Ohi M, Kai T et al., Nucl. Instrum. Meth. Phys. B 2009:600(1):41 – 43.
[10] Sato T, Iwamoto Y, Hashimoto S et al, J. Nucl. Sci. Technol. 55(5-6), 684-690 (2018)[11] Michel R, Dittrich B, Herpers U et al., J. Analyst 1989 Mar;114:287 – 293.
[12] Takeshita H, Meigo S, Matsuda H et al., Proceedings of J-PARC Symposium 2019 (to be published).

212- 212 -

JAEA-Conf 2021-001

 Estimation of Flux and Residual Radioactivity forthe COMET Phase-I Experiment
NaokiTOKUNAGA†1 ,NobuhiroSHIGYO1 ,ShunsukeMAKIMURA2 ,Yoshinori
FUKAO2 ,NaoyaKAMEI2 ,and MakotoYOSHIDA2
1

DepartmentofApplied Quantum Physics andNuclearEngineering, Kyushu University
2HighEnergy AcceleratorResearchOrganization(KEK)†
Email: n.tokunaga@kune2a.nucl.kyushu-u.ac.jp

Abstract
COherent Muon to Electron Transition (COMET) is an experiment at J-PARC, which
will search for coherent neutrino-less conversion of a muon to an electron in a muonic atom.
The experiment will be carried out in two steps: Phase-I and Phase-II. In the Phase-I experiment, the 3.2-kW 8-GeV proton beam irradiates a 70-cm long graphite target to produce
negative pions. The negative pions are captured in the magnetic ﬁeld and delivered topion-decay and muon-transport sections. The Phase-I experiment aims to detect the μ− econversion events and measure the beam-related background events for the Phase-II experiment. It has been planned that the maintenance by radiation workers would be conducted
after the 150-day operation and the following 180-day cooling. It is necessary to evaluate theresidual radiation dose for the safety of the workers during the maintenance. On this study,
we calculated ﬂuxes of neutron, photon, proton and other charged particles in the beam
room during the beam operation and the residual activity after the cooling time by using theMonte Carlo simulation code PHITS version 3.22 and DCHAIN-PHITS version 3.21. The
calculation results show that the design of components around the target and beam dump
needs to be improved to reduce the radioactivities after the cooling time.

1

Introduction

Coherent muon to electron transition (COMET) experiment is planning to search for the lepton
ﬂavor violating process of μ− N → e− N in the ﬁeld of an aluminum nucleus [1]. The PhaseI experiment aims for the experimental sensitivity of 3.1 × 10−15 , which is a factor of 100
improvement from the current limit in SINDRUM-II [2] at PSI. Figure 1 shows the geometry of
the beam room. In the Phase-I experiment, the 3.2-kW 8-GeV proton beam from the J-PARC
main ring irradiates the 70-cm long pion production target made of graphite for 150 days. Theenergy loss of proton in the target is about 200 MeV. The components around the target arehighly activated by the secondary particles. The magnetic ﬁeld with the maximum magnitude 5
T is generated by the capture solenoid (CS). The produced pions are captured and transferredto the detection area by the magnetic ﬁeld. The ﬂange at the downstream of the beam has theobround shape beam hole with the 14.3-cm straight sides and the semicircles of 10.0-cm radius.
Currently, it has been planned that the maintenance by radiation workers would be conducted
after the 180-day cooling. It is, therefore, necessary to estimate the eﬀective dose rate for thesafety of the workers.
In this paper, we report the eﬀective dose rate distribution calculated by the general purpose
Monte Carlo radiation transport code PHITS [3] version 3.22 and the decay chain analysis code213
- 213 -

JAEA-Conf 2021-001

Figure 1: Plan view of the beam room.
DCHAIN-PHITS [4] version 3.21. Because the result shows that the eﬀective dose rate is toohigh to work around the ﬂange, we list the possible ways to reduce the radioactivity.

2

Simulation

First, neutron ﬂux with kinetic energy of less than 20 MeV and production rates of radioactive
nuclides are estimated by using PHITS when the 8.0-GeV proton beam irradiates a 70-cm longgraphite target. The computational geometry and the magnetic ﬁeld shown in Figures 2 and 3
are used. For the estimation of neutron production yields with kinetic energy of less than 20
MeV, JENDL-4.0 is used. For neutrons in the range of 20 MeV to 3 GeV and protons upto
3 GeV, INCL4.6 coupled with GEM is used. For neutrons and protons with kinetic energy ofgreater than 3 GeV, JAM coupled with GEM is used. For electrons and photons, EGS5 is used.
We correct treatment of relativistic eﬀect on transportation of charged particles in the magnetic
ﬁeld in PHITS version 3.21. The correction has been merged into PHITS version 3.22. With
these data as input, DCHAIN-PHITS calculates radioactivity and gamma-ray spectrum at any
given time. Again, photon ﬂux is calculated by PHITS, and then it is converted to eﬀective dose
rate by using the conversion coeﬃcient of AP irradiation based on ICRP103 as shown in Figure
4 [5].

3

Result3.1

Particle ﬂuxes during the beam operation

Figures 5, 6 and 7 show ﬂux distributions of neutron, negative pion and negative muon during
the beam operation, respectively. High neutron ﬂux of 2.0 × 1010 cm−2 s−1 is estimated aroundthe production target and the dump. Pions and muons are transported to the detection area by
the magnetic ﬁeld as expected. The maximum ﬂux for the pion and the muon are 2×109 cm−2 s−1
and 7 × 107 cm−2 s−1 , respectively.

3.2

Residual activities

Figure 8 shows how the residual activities change over time in four regions (production target,shield for CS, ﬂange, and beam dump). The half lives of the nuclides shown in Figure 8 arelisted in Table 1. In the graphite production target, more than 108 Bq/cc of 11 C exists right214- 214 -

JAEA-Conf 2021-001

Figure 2: Geometry around the muon production target and the beam dump in the PHITS
simulation.

Figure 3: Magnetic ﬁeld of the pion production target and the muon capture solenoid sections.

Figure 4: Conversion coeﬃcient from the photon energy to the eﬀective dose of AP irradiation
based on ICRP103.
after the 150-day beam operation. It decays with half life of 20 minutes. Therefore after coolingtime, 3 H and 7 Be are dominant. In the copper shield of CS, the radioactive isotopes of copperwith short half life are dominant at ﬁrst, and the radioactive isotopes of cobalts and 54 Mn
are dominant after 180 days. In the ﬂange and the dump, 54 Mn, 55 Fe and 49 V are the mainradioactive nuclides.

3.3

Spatial distribution of dose rate

Figure 9 shows the eﬀective dose rate distribution after the 150-day beam operation and the180-day cooling time. The components along the proton beam line are strongly activated, andtherefore high eﬀective dose rates are estimated around them. Around area marked as star in
the ﬁgure, where workers need to approach during the maintenance, the eﬀective dose rate is
10 mSv/h. In front of the dump (marked as circle), the eﬀective dose rate of 2.5 mSv/h isestimated.

215- 215 -

JAEA-Conf 2021-001

Figure 5: Neutron ﬂux distribution of the beam room.

Figure 6: Negative pion ﬂux distribution of
the beam room.

4

Figure 7: Negative muon ﬂux distributionof the beam room.

Discussion

The calculated eﬀective dose rate is much higher than 100 μSv/h as tentative target aroundarea marked as star shown in Figure 9 in the beam room. The following options may reduce theresidual radioactivity.
First thing is to have a longer cooling time. Figure 10 shows decrease of the eﬀective dose
rate in front of the ﬂange over time. The main contributor to the eﬀective dose rate from theﬂange is 54 Mn with half life of 312 days, the eﬀective dose rate, therefore, only decreases by halfin about a year.
Second thing is to make the beam window of the ﬂange larger. As shown in Figure 11, highproton ﬂux exists around the beam window. A larger beam window makes these protons go
through without them interacting with the ﬂange, which results in less activation. The size ofthe beam window, however, cannot be increased unlimitedly. The further calculation needs tobe carried out in order to know the correlation the window size and the residual activity.
Third thing is to make the pion production target shorter. The amount of secondary particles
produced in the target are proportional to the energy loss in the target. The energy loss of the
primary beam is proportional to the length of the target. Therefore, a shorter production
target suppresses the residual activity. However, a shorter production target also results in theundesired decrease in pion production.
216- 216 -

JAEA-Conf 2021-001

Figure 8: Residual activities of main isotopes from start of beam irradiation at (a) production
target, (b) radiation shield for CS, (c) ﬂange, and (d) beam dump.

nuclide
51 Cr
54 Mn
11 C
14 C
62 Cu

Table 1: The half lives of the nuclides
half life
nuclide half life
nuclide56 Mn
27.7 days
2.5 hours 48 V
55 Fe
312 days
2.7 years 49 V
7
3H
20 minutes
Be
53 days64
5730 daysCu
12 hours 66 Cu
57 Co
9.7 minutes 58 Co
70 dayshalf life
16.0 days
330 days12.3 years
5.1 minutes
271 days

With all available means, the design of the components needs to be optimized so as tosuppress the eﬀective dose rate as much as possible. If the eﬀective dose rate cannot be lowered
enough, a remote working is another possible option.

5

Summary

The eﬀective dose rate distribution after 150-day beam irradiation by 3.2-kW 8-GeV proton
beam and 180-day cooling for COMET Phase-I experiment is estimated by PHITS and DCHAINPHITS for the safety assessment. The results show that the residual radiation is too high forpeople to work in the beam room. Three possible ways are indicated to suppress the residual
activity, but the further investigation is still necessary. Remote working might be anotherpractical option.

217- 217 -

JAEA-Conf 2021-001

Figure 9: Spatial distribution of eﬀective dose rate after 180-day cooling.

Figure 11: Proton ﬂux at the ﬂange in xyplane. High ﬂux of the beam is seen around(x, y) = (-40, -20). The black lines indicate
the boundaries of the ﬂange.

Figure 10: Decrease of eﬀective dose ratein front of the ﬂange.

References[1] Lee M.J., COMET Muon Conversion Experiment in J-PARC, Front. Phys. Vol. 6, 2018,133.
[2] Bertl W. et al., A search for μ-e conversion in muonic gold, Eur. Phys. J. C, Vol. 47, no.2,
2006, pp.337-346.
[3] T. Sato, et al., Features of Particle and Heavy Ion Transport code System (PHITS) version
3.02, J. Nucl. Sci. Technol., Vol. 55, no.6, 2018, pp.684-690.
[4] Hunter N. Ratliﬀ et al., Modernization of the DCHAIN-PHITS activation code with newfeatures and updated data libraries, Nucl. Instrum. Meth. B, Vol. 484, 2020, pp.29-41.
[5] Petoussi-Henss N, Bolch WE, Eckerman KF, et al., Conversion coeﬃcients for radiologicalprotection quantities for external radiation exposures, Ann ICRP, Vol. 40, no. 2-5, 2010,
pp.1-257.

218- 218 -

JAEA-Conf 2021-001

 Measurement of neutron total cross sectionsof Sn-Pb alloys in solid and liquid states

Takuya UEMURA1, Jun-ichi HORI2, Kazushi TERADA2, Tadafumi SANO3,
Jun NISHIYAMA4, Rei KIMURA5 and Ken NAKAJIMA2
1
2

Departments of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto-shi, Kyoto, 615-8246, Japan

Institute of Integrated Radiation and Nuclear Science, Kyoto University, Kumatori-cho, Sennan-gun, Osaka,590-0494, Japan
3

4

Kindai University Atomic Energy Research Institute, Higashiosaka-shi, Osaka, 577-8502, Japan

Laboratory for Advanced Nuclear Energy, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
5

Toshiba Energy Systems & Solutions Corporation, Saiwai-ku, Kawasaki-shi, Kanagawa, 212-8585, Japan

Email : uemura.takuya.77n@st.kyoto-u.ac.jp

The use of a Sn-Pb alloy as an emergency in-core heat transport medium is being considered in thedesign of a small modular reactor proposed by Toshiba Energy Systems & Solutions Corporation. However,there exists no experimental data for the neutron cross sections of Sn-Pb alloy.
In the present study, the neutron total cross sections of Sn-Pb alloy were obtained from neutrontransmission measurements by the time-of-flight (TOF) method using the Kyoto University Institute forIntegrated Radiation and Nuclear Science – Linear Accelerator (KURNS-LINAC). The sample temperature
was changed from room temperature (solid) up to 300 ℃ (liquid). The total cross sections of the solid andliquid states were compared with the evaluated data and the previous data of Pb and Sn.

Keywords: neutron total cross section, Sn-Pb alloy, time-of-flight, KURNS-LINAC, solid, liquid1.

Introduction
Recently, a small modular reactor (SMR), which has inherent and passive safety, has been receiving

attention all over the world. In Japan, a very small modular reactor, namely, MoveluXTM (Mobile-Very-Small
reactor for Local Utility in X-mark) [1] is being developed by Toshiba Energy Systems & Solutions
Corporation. MoveluXTM is a thermal reactor that uses calcium hydride as a neutron moderator and its heat
output is 10 MWth. As for the heat exhaust function in the core, some heat pipes are used, and heat can betransported by using temperature differences. On the other hand, when the heat exhaust function of the heat
pipes is lost, an emergency in-core heat transport medium, instead, will carry the heat to the reactor wall by219- 219 -

JAEA-Conf 2021-001

natural convection, and the core wall will be cooled by ambient air circulation. The use of a Sn-Pb alloy as
the emergency in-core heat transport medium is being considered.
Since the melting point of the Sn (60 wt%)-Pb (40 wt%) alloy is about 180 ℃, the alloy is solid state
when the reactor is just started to work, and it becomes liquid state while the power increases, because thecore temperature reaches 660 ℃ in full power operation. Change of the state of the alloy during operation
will affect the core characteristics. In particular, the thermal neutron scattering cross section will change
between the solid and liquid states, because solid metal has a crystal structure and it causes the coherent
scattering effect, and when it melts the effect changes. Alloy also has a crystal structure and its orientation isdifferent from that of single element metal. The wavelength of a thermal neutron is close to the lattice spacingof atoms in the crystal structure and the coherent scattering occurs. Therefore, the neutron cross section in
the thermal neutron energy region also differs due to the influence of coherent scattering by the crystal
structure and its orientation. However, there are no reports on experimental data for the neutron cross sectionof Sn-Pb alloy in both solid and liquid states. In the present work, the thermal neutron total cross sections ofsolid and liquid Sn-Pb alloy were measured and compared with the evaluated nuclear data of the free gas
model in JENDL-4.0 [2].

2.

Experiment
The neutron total cross section measurements of Sn-Pb alloy were carried out by using the TOF method

at KURNS-LINAC. The experimental arrangement is shown in Figure 1. The KURNS-LINAC was operated
with a pulse width of 1 μs, a repetition rate of 50 Hz, and an average current of 28.4 μA. The accelerated
electrons were incident on a water-cooled Ta-target [3]. Then, fast neutron were produced by the photo
nuclear reaction (Џ, n). To obtain thermal neutrons, the Ta-target was set at the center of a water moderator
tank (20 cm in diameter). The neutron flight tube was used in the direction of 135 degrees with respect to the
LINAC beam line [4]. A 6Li-galss scintillator detector, GS20, was used as a neutron detector. The flight length
between the Ta-target and the 6Li-glass detector was about 12.1 m.
Pulsed electron beam

Concrete
BF3 Counter

Ta

e-

water
135㼻

6Li-glass

Pb

SamplePolyethylene-Boron

24.3 cm

12.1 mFigure 1: Experimental arrangement for neutron total cross measurement.
The specifications of the Sn-Pn alloy samples and the Al case are listed in Table 1. The Sn-Pb alloys
containing 60 wt% natural tin and 40 wt% natural lead were used. We prepared two types of samples in thesolid state, one is a re-solidified sample with 10 mm thickness contained in the Al case after melting, and theother is a commercially available rod with 6 mm thickness. To reduce the effects of neutron scattering from220
- 220 -

JAEA-Conf 2021-001

the Al case, its thickness was reduced to 1 mm. The measurement times are listed in Table 2.
Table 1: Specifications of Sn-Pb alloys and Al case
Sn-Pb alloy (Sn : 60 wt%, Pb : 40 wt%)Alliquidsolid
solid
Al case(in Al case) (in Al case) (rod sample)
413.52413.52200.51
193.42
2750
2625
3835
4200
10
10
6
1 (beam line)

SampleWeight (g)2Size (mm )Thickness (mm)Table 2: List of measurement times

Sn-Pb
alloy

SampleMeasurement time (h)12.0liquid (300 Υ䠅㻌liquid (250 Υ䠅㻌
12.0
liquid (210 Υ䠅㻌
12.0
solid (in Al case)
12.0
solid (rod sample)
9.0
Al case
12.0
Blank
9.0
Al case + res.filter
3.0

In the TOF method, the incident neutron energy was obtained by the following equation:͹ʹǤ͵ ൈ ‫ ܮ‬ଶ‫ ܧ‬ൌ ൬
൰
‫ݐ‬

(1)

where, E is the incident neutron energy, L is the neutron flight length and t is the TOF. The neutron total crosssection ߪ௧௢௧ ሺ‫ܧ‬ሻ was obtained by the following equation:ͳ ሺ‫ܥ‬௦ ሺ‫ܧ‬ሻ െ ‫ܥ‬௦ǡ௕ ሺ‫ܧ‬ሻሻȀ‫ܯ‬௦ߪ௧௢௧ ሺ‫ܧ‬ሻ ൌ െ ݊ ሺ‫ܥ‬௢ ሺ‫ܧ‬ሻ െ ‫ܥ‬௢ǡ௕ ሺ‫ܧ‬ሻሻȀ‫ܯ‬௢

(2)where, ‫ܥ‬௦ ሺ‫ܧ‬ሻ and ‫ܥ‬௢ ሺ‫ܧ‬ሻ are the neutron count rates with the sample existed (hereafter, called as “sample-in”) and not existed (hereafter, called as “sample-out”) measured by the 6Li-glass detector. ‫ܥ‬௦ǡ௕ ሺ‫ܧ‬ሻ and‫ܥ‬௢ǡ௕ ሺ‫ܧ‬ሻ are the neutron background for the sample-in and sample-out. ‫ܯ‬௦ and ‫ܯ‬௢ are the neutron countrates by the BF3 detector to monitor neutron intensity fluctuation between measurements. ݊ is the atomic

area density [atom/barn] of Sn-Pb alloy samples.

The γ-ray background level was estimated from the pulse height spectrum of each measurement. Figure

2 shows the pulse height spectrum of the 6Li-glass detector. As shown in Figure 2, the counts for 320-420 ch.
includes neutron and background γ-ray counts. On the other hand, the counts for 220-319 ch. is only
background γ-ray one. Then, the γ-ray background level was evaluated from the TOF spectrum by interpolate
the corresponding pulse height normalized by each event. Figure 3 shows the results of evaluated γ-ray
background of the TOF spectrum, comparing with the one with resonance filters (Mn, Co, Ag, In and Cd).
As shown in Figure 3, the evaluated γ-ray background shows good agreement with the dips of In (1.46 eV),221
- 221 -

JAEA-Conf 2021-001

Ag (5.19 eV), Co (132 eV), and Mn (337 eV), which correspond to the large resonance peaks, respectively.
Then, it was confirmed that the present background evaluation method is appropriate.
㻝㻜㻞

㻜㻚㻢

㻌䃒㻙㼞㼍㼥㻌㻮㻚㻳㻚㻌㼞㼑㼟㻚㻌㼒㼕㼘㼠㼑㼞㻯㼛㼡㼚㼠㼟㻛㻯㼔㼍㼚㼚㼑㼘㻛㼟㻯㼛㼡㼚㼠㼟㻛㻯㼔㼍㼚㼚㼑㼘㻛㼟

㻝㻜㻝

㻝㻜㻜

㻝㻜㻙㻝

Co-59
132eV

㻜㻚㻠

Mn-55
337eV

㻝㻜㻙㻞

㻝㻜㻙㻟

㻜

㻝㻜㻜

㻞㻜㻜

㻟㻜㻜

㻠㻜㻜

㻡㻜㻜

㻢㻜㻜

㻣㻜㻜

㻤㻜㻜

Ag-1095.19eV

㻜㻚㻞

㻥㻜㻜

㻜

㻟㻜

㻼㻚㻴㻚㻌㻯㼔㼍㼚㼚㼑㼘㻝㻜㻜

In-115
1.46eV㻝㻜㻜㻜㻟㻜㻜㻜㼀㻻㻲㻌㻯㼔㼍㼚㼚㼑㼘

Figure 2: Pulse height spectrum of 6Li-glass Figure 3: TOF spectra with resonance filters
detector.
and evaluated γ-ray background.

3.

Results and Discussion
We will discuss the results of the measurements from three perspectives. The first perspective is theeffect of temperature of the liquid alloy. Figure 4 shows the neutron total cross sections of the liquid Sn-Pb
alloys with different temperatures. There are some small differences in the total cross sections between 210 ℃
and other temperatures from 0.002 eV to 0.01 eV. This seems to be caused by the remaining crystal structure
in liquid at 210 ℃, which is relatively low temperature. On the other hand, there is a little difference in the
cross sections between 250 ℃ and 300 ℃. However, in the present study, it is difficult to say clearly that
there is a difference due to sample temperature in the liquid state. Before the experiment, we had consideredthat the effect of the coherent scattering would disappear in the neutron cross section of the liquid state, andthe cross section would be almost close to the one with the free gas model. However, the effect of coherent
scattering still exists in the liquid state in the present study.

㻥

㻌㻞㻝㻜䉝
㻌㻞㻡㻜䉝
㻌㻟㻜㻜䉝

㼀㼛㼠㼍㼘㻌㻯㼞㼛㼟㼟㻌㻿㼑㼏㼠㼕㼛㼚㻌㻔㼎㼍㼞㼚㻕

㻤

㻣

㻢

㻡

㻠

㻟
㻞㼤㻝㻜㻙㻟㻝㻜㻙㻞㻝㻜㻙㻝㻺㼑㼡㼠㼞㼛㼚㻌㻱㼚㼑㼞㼓㼥㻌㻔㼑㼂㻕

Figure 4: Comparison of neutron total cross sections of liquid Sn-Pb alloy between temperatures(210 ℃, 250 ℃ and 300 ℃).
222- 222 -

JAEA-Conf 2021-001

The second perspective is the effect of the solid/liquid sates on the neutron total cross sections. The
cross sections of the Sn-Pb alloy in the solid and liquid states, and the JENDL-4.0 data are compared in
Figure 5. The JENDL-4.0 data shows the neutron total cross sections of the Sn-Pb alloy calculated using the
Sb and Pb cross sections of the JENDL-4.0 with the weights of the atomic ratio of each composition. In thesolid state, the Bragg edges due to the crystal structure are observed in the neutron energy below 0.05 eV.
However, it turned out that the magnitude (or height) of Bragg edges in the liquid state decreased and widenedin the energy region. This would be caused by change of the crystal structure of the solid due to melting. In
comparison with the JENDL-4.0, although the measured data shows big difference in the low energy, theyshow good agreement above 0.05 eV. This is because the influence of coherent scattering due to the crystal
structure is little above 0.05 eV.
㻝㻜㻌㻿㼛㼘㼕㼐
㻌㻸㼕㼝㼡㼕㼐
㻌㻶㻱㻺㻰㻸㻙㻠㻚㻜㼀㼛㼠㼍㼘㻌㻯㼞㼛㼟㼟㻌㻿㼑㼏㼠㼕㼛㼚㻌㻔㼎㼍㼞㼚㻕

㻤

㻢

㻠

㻞

㻜
㻝㻜㻙㻞

㻝㻜㻙㻝

㻝㻜㻜

㻺㼑㼡㼞㼠㼛㼚㻌㻱㼚㼑㼞㼓㼥㻌㻔㼑㼂㻕

Figure 5: Comparisons between neutron total cross sections of Sn-Pb alloys
in the solid, liquid states and JENDL-4.0.
The third perspective is the comparisons in the solid state measurements. In Figure 6, the neutron total
cross sections of Sn, Pb measured in the past [5,6] and Sn-Pb alloys in the present measurement are shown.
The present Sn-Pb alloy measurements are the results of the two solid samples, the re-solidified sample andthe rod one (see Section 2, for detail). As seen in Figure 6, several Bragg edges are in good agreement between
the re-solidified and rod samples, Sn, and Pb from 0.002 eV to 0.05 eV. However, there are differences in the
Bragg edges between the re-solidified and rod samples. For the re-solidified sample, some Bragg edges of
Pb tended to disappear at 3.42 meV, 6.82 meV, and 17.1 meV. The neutron cross section of the material witha crystal structure changes depending on its orientation. Therefore, this difference between the re-solidified
and rod samples would be due to the change in crystal orientation caused by melting. However, there is stillroom for considering the reasons of the difference as further study.

223- 223 -

JAEA-Conf 2021-001㻝㻠㼀㼛㼠㼍㼘㻌㻯㼞㼛㼟㼟㻌㻿㼑㼏㼠㼕㼛㼚㻌㻔㼎㼍㼞㼚㻕㻝㻞㻌㻿㼚㻌㻔㻾㻚㻱㻚㻌㻹㼍㼥㼑㼞㻕㻌㻌㻌㻼㼎㻌㻔㻳㻚㻌㻹㼡㼔㼞㼑㼞㻌㻕㻌㻌㻌㻿㼛㼘㼕㼐㻌㻔㼞㼛㼐㻕㻌㻾㼑㻙㼟㼛㼘㼕㼐㻌㻔㼕㼚㻌㻭㼘㻌㼏㼍㼟㼑㻕

㻝㻜
㻤
㻢
㻠
㻞
㻜
㻝㻜㻙㻞

㻺㼑㼡㼠㼞㼛㼚㻌㻱㼚㼑㼞㼓㼥㻌㻔㼑㼂㻕

Figure 6: Comparison between the total cross sections of the rod sample (indicated as“solid (rod)”), the re-solidified sample after melting (indicated as “Re-solid (in Alcase)”) of Sn-Pb alloys and the previously measured data of Pb and Sn.

4.

Conclusion
We have performed the neutron total cross section measurements of the Sn-Pb alloy in solid and liquidstates using the TOF method at KURNS-LINAC. The measurement results were compared with the evaluateddata in JENDL-4.0 and the previous experimental data of Sn and Pb. The total cross sections of the solid andliquid states were compared and changes in Bragg edges were observed in the energy range below 0.05 eV.
Comparing the total cross sections of the rod and re-solidified samples, it was confirmed that Bragg edges,
which is thought to be due to the crystal structure of Pb, was not observed in the re-solidified sample.
The present study shows important data for using the solid and liquid alloys as heat transport medium
in the core of a thermal reactor.

References>@ R. Kimura et al., Nucl. Sci. Eng., 2020; 194: 213-220
>@ K. Shibata et al., J. Nucl. Sci. Technol., 2011; 48(1): 1-30
>@ K. Kobayashi et al., Ann. Rep. Res. Reactor Inst. Kyoto Univ., 1989: 22; 142
>@ Y. Takahashi et al., Phys. B: Condensed Matter, 2018; 551; 488-491
>@ G. Muhrer et al., Nucl. Instrum. Methods Phys. Res. Sec. A, 2007; 572: 866-873
>@ R. E. Mayer et al., Jour. Atomkernenergie, 1981: 39; 55

224- 224 -

JAEA-Conf 2021-001

 Research for nuclear transmutationof high-radiotoxic nuclide 90Sr
via proton- and deuteron-induced reactions
RikuMatsumura†1, 2 ,HideakiOtsu1 ,HeWang1 ,NobuyukiChiga1 ,ShoichiroKawase3 ,KeitaNakano3 ,HiroyoshiSakurai1, 4 ,MizukiShikata5 ,SatoshiTakeuchi5 ,Yasuhiro
Togano5 ,andfor theImPACT-RIBFcollaboration
1

RIKENNishinaCenter,Saitama351-0198,Japan
DepartmentofPhysics,Saitama University,Saitama338-8570,Japan3
DepartmentofAdvancedEnergyEngineering Science,KyushuUniversity,Fukuoka
816-8580,Japan
4
DepartmentofPhysics,TheUniversityofTokyo,Tokyo113-0033,Japan
5DepartmentofPhysics,TokyoInstituteof Technology,Tokyo152-8551,Japan†
Email: riku@ribf.riken.jp
2

The isotopic-production cross sections for high-radiotoxic nuclide 90 Sr on proton and deuteron at
104 MeV/nucleon were obtained in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory.
The experimental data were compared with those obtained from calculations using the Particle and Heavy
Ion Transport code System. These were also compared with the existing data.

1

Introduction

The processing of spent fuels from nuclear power plants is a worldwide problem. The high-level
radioactive wastes are the by-products of the reprocessing of spent fuels, which contain minor actinides
and ﬁssion products. In this study, we focus on 90 Sr, which is the most radiotoxic nuclide in the ﬁssion
products (see Figure 1 and Table 1).
Table 1: Nuclides contained in the high-level radioactive waste and its half-life, toxicity, and content.
Nuclide
79
Se
90
Sr
93
Zr
99
Tc
107
Pd
126
Sn
129
I
135
Cs
137
Cs

Half-life [y]29.5 ×10428.8
15.3 ×105
21.1 ×104
65.0 ×105
10.0 ×104
15.7 ×106
23.0 ×105
30.1

Toxicity [μSv/kBq]
2.9
28
1.1
0.64
0.037
4.7
110
2
13

225
- 225 -

Content [kg/tHM]
0.006
0.6
1
1
0.3
0.03
0.2
0.5
1.5

JAEA-Conf 2021-001

109

FP-Total
Sr-90
Cs-137
Cs-134
Ru-106Ce-144
Pm-147
Eu-154
Sb-125
Cd-113m
Eu-155
Ag-110m
Sm-151
Tc-99
I-129

8

Potential radiotoxicity [Sv/ItHM]

10

107
106
105
104
103

Sn-126
Rh-102
Zr-93
Eu-152
Pm-146
Cs-135
Se-79
Te-127m
Pd-107
Ho-166m
Nb-94
Sm-147
Rb-87
Tc-98
Sm-146102
101
100
10-1 0
10

101

102

103

104

Time [year]

105

106

107

108

Figure 1: Potential radiotoxicity per one ton of spent fuels from a pressurized water reactor (nuclear fuelburnup: 45 GWd/tHM), after ﬁve years cooling, taken from Ref. [1].
There is a strong desire to develop nuclear transmutation technology using accelerator facilities toreduce these harmful nuclides. The simplest way can be irradiating a neutron beam on the radioactive
waste. 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 from 90 Sr in advance. From
this point of view, the inverse kinematics, i.e., incident 90 Sr beam on light-particle targets, is an eﬀective
method for identifying reaction products in the forward direction.

2

Experiment

The experiment was performed at the RIKEN Radioactive Isotope Beam Factory (RIBF) by using
the RIKEN Projectile-fragment Separator (BigRIPS) [2] and the ZeroDegree Spectrometer (ZDS) [2].
The setup is shown in Figure 2. The details of the experiment are given in Ref. [3]. The secondary
beam, including 90 Sr, was produced by in-ﬂight ﬁssion of 238 U at 345 MeV/nucleon on a 3-mm thick9
Be production target at the BigRIPS ﬁrst stage. In the following second stage, the beam particles wereselected and identiﬁed event-by-event using the TOF-Bρ-ΔE method [4], as shown in Figure 3.

Production target
9Be (3 mm)
F0

BigRIPS 1st Stage
Production / Separation

ZDS

F5
F1

F2

F3

F4

F11

Measurement
F6

F7

F8

F9

F10

Reaction targets
CH2, CD2, C (~200 mg/cm2)

BigRIPS 2nd Stage
Tagging

Figure 2: Schematic view of the RIKEN Projectile-fragment Separator (BigRIPS) and the ZeroDegree
Spectrometer (ZDS).

226- 226 -

JAEA-Conf 2021-001

44

Atomic number Z

42
40
38
90Sr

36
2.15

2.2

2.25

2.3

2.35

Mass-to-charge ratio A/Q

2.4

2.45

Figure 3: Secondary beam particle identiﬁcations at the BigRIPS.
The beam particles bombarded at 104 MeV/nucleon to CH2 (179.2 mg/cm2 ), CD2 (218.2 mg/cm2 ),and C (226.0 mg/cm2 ) reaction targets, which placed at the entrance of the ZDS. The residual nuclei
produced in reactions were identiﬁed in the ZDS with the same method as the BigRIPS. Because themomentum acceptance of the ZDS is limited to ±3 %, the experiment was carried out by using ﬁve
diﬀerent momentum settings (Δ (Bρ) /Bρ = −9, −6, −3, 0, and +3 %) for each target to accept thewide range of mass-to-charge ratio A/Q. Figure 4 shows an example of particle identiﬁcations after
selecting 90 Sr (Z = 38, A/Q = 2.37) for the projectile and the Δ (Bρ) /Bρ = −6 % setting at the ZDS.
The reaction cross sections were deduced from the number of incident 90 Sr, the number of each residual
particle, and the thickness of the target. The backgrounds of carbon from CH2 and CD2 targets andbeam-line materials were subtracted by using the empty and carbon target runs.
40

Y
Atomic number Z

38

36

34

Sr
Rb
Kr
Br
Se
⁝

32
2.1

2.15

2.2

2.25

2.3

Mass-to-charge ratio A/Q

2.35

Figure 4: Residual particle identiﬁcations at the ZDS.

227
- 227 -

2.4

JAEA-Conf 2021-001

Results and Discussion

Cross section σ [mb]3102(a) Y (Z = 39)

101

σp Exp.
σd Exp.
σp PHITS
σd PHITS(b) Sr (Z = 38)(c) Rb (Z = 37)(e) Br (Z = 35)(f) Se (Z = 34)

100
10-1
102 (d) Kr (Z = 36)
101
100
10-1

75

80

85

90

75

80

85

Mass number A

90

75

80

85

90

Figure 5: Isotopic-production cross sections of proton- (circles) and deuteron-induced (diamonds) reactions and those obtained from the PHITS calculations (proton for solid, deuteron for dotted).
The data points above 1 mb were obtained with good statistics. These were compared with thecalculations using the Particle and Heavy Ion Transport code System (PHITS) [5] as shown in Figure 5.
The Liége Intranuclear Cascade model (INCL4.6) [6] and the Generalized Evaporation Model (GEM) [7]were employed in the calculations. It is seen that the calculation results were overestimated aroundthe mass number of the projectile. Few-nucleon removal reactions are not interpreted properly in the
INCL because momentum distributions of the nuclear surface are treated in a semiclassical way [8]. In
addition, even-odd staggering eﬀects have appeared excessively for nuclides produced by emitting many
nucleons. This may be controlled to some extent by considering the competition between particle andγ-ray emissions, and the discrete energy levels, in the GEM.

228
- 228 -

JAEA-Conf 2021-001

102(a) Y (Z = 39)

101

Cross section σ [mb](b) Sr (Z = 38)(c) Rb (Z = 37)(e) Br (Z = 35)(f) Se (Z = 34)

σp 104 MeV/u
σp 185 MeV/u

100
10-1
102 (d) Kr (Z = 36)
101
100
10-1

75

80

85

90

75

80

85

Mass number A

90

75

80

85

90

Figure 6: Results of proton-induced reaction cross sections at 104 MeV/nucleon (circles). For comparison,
those at 185 MeV/nucleon (crosses) [9] are also shown.

102(a) Y (Z = 39)

101

Cross section σ [mb](b) Sr (Z = 38)(c) Rb (Z = 37)(e) Br (Z = 35)(f) Se (Z = 34)

σd 104 MeV/u
σp 185 MeV/u

100
10-1
102 (d) Kr (Z = 36)
101
100
10-1

75

80

85

90

75

80

85

Mass number A

90

75

80

85

90

Figure 7: Same as Figure 6, but of deuteron-induced ones (diamonds).
Figure 6 shows the incident energy dependences of the cross sections with proton-induced reaction. In
one-proton removal channel, which goes to 84,85,86,87 Rb at 104 MeV/nucleon, even-odd staggering eﬀects
were observed distinctly. This has not been reported in the previous ImPACT-related studies [3, 10].
Figure 7 shows the incident particle dependences of the cross sections with the total kinetic energies,
208 MeV for deuteron. The trends and orders of the cross section are in good agreement with 185 MeV
for proton. However, the deuteron-induced reaction is expected the initial reaction mechanism to change
drastically at lower energy [11], we would also like to obtain the reaction data for 90 Sr in the near future.

229- 229 -

JAEA-Conf 2021-001

4Conclusion

The isotopic-production cross sections for high-radiotoxic nuclide 90 Sr on proton and deuteron at
104 MeV/nucleon were obtained in inverse kinematics at the RIBF. The experimental data were comparedwith those obtained from the PHITS calculations. Some discrepancies to be improved still remain. In
proton-induced reaction cross sections at 104 MeV/nucleon, one-proton removal channel which goes to84,85,86,87
Rb observed even-odd staggering eﬀects distinctly. More detailed analysis will be performed.

Acknowledgments
We are grateful to the accelerator staﬀ of the RIKEN Nishina Center for providing a high-quality
U beam. This work was funded by the ImPACT Program of the Council for Science, Technology andInnovation (Cabinet Oﬃce, Government of Japan).
238

References<> K. Nishihara, “Data for Estimating Potential Radiotoxicity of Spent Nuclear Fuel”, JAEAData/Code 2010-012 (2010).
<> T. Kubo et al.,“BigRIPS separator and ZeroDegree spectrometer at RIKEN RI Beam Factory”,
Prog. Theor. Exp. Phys.  2012, 03C003 (2012).
<> S.Kawaseetal.,“Studyofprotonanddeuteroninducedspallationreactionsonthelong-livedﬁssion
product93Zrat105MeV/nucleonininversekinematics”,Prog.Theor.Exp.Phys. 2017,093D03
(2017).
<> N.Fukudaetal.,“IdentiﬁcationandseparationofradioactiveisotopebeamsbytheBigRIPSseparatorattheRIKENRIBeamFactory”,Nucl.Instrum.Meth.B317,323(2013).
<> T. Sato et al., “Features of Particle and Heavy Ion Transport code System (PHITS) version 3.02”,+ Nucl. Sci. Technol. 55, 684 (2018).
<> A.Boudardet al.,“NewpotentialitiesoftheLiégeintranuclearcascademodelforreactionsinduced
by nucleons and light charged particles”, Phys. Rev. C 87, 014606 (2013).
<> S. Furihata, “Statistial analysis of light fragment production from medium energy proton-induced
reactions”, Nucl. Instrum. Meth. B 171, 251 (2000).
<> D.Mancusietal.,“Improvingthedescriptionofproton-inducedone-nucleonremovalinintranuclearcascade models”, Phys. Rev. C 91, 034602 (2015).
<> H.Wangetal.,“Spallationreactionstudyforﬁssionproductsinnuclearwaste:Crosssectionmeasurementsfor137Csand90Sronprotonanddeuteron”,Phys.Lett.B754,104(2016).
<> H.Wangetal.,“Spallationreactionstudyforthelong-livedﬁssionproduct107Pd”,Prog.Theor.Exp.
Phys.2017,021D01(2017).
<> H. Wang et al., “Enhancement of element production by incomplete fusion reaction with weaklybound deuteron”, Commun. Phys. 2, 78 (2019).

230- 230 -

JAEA-Conf 2021-001

 Detection of gamma ray from short-lived fission product at KUCA
and KURNS-LINAC

Yasushi NAUCHI1*, Jun-ichi HORI2, Tadafumi SANO 3, Yoshiyuki TAKAHASHI2, Koji
KUSUMI1 and Hironobu UNESAKI 2
1Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry
2-6-1 Nagasaka, Yokosuka-shi, Kanagawa 240-0196, Japan
2

Institute for Integrated Radiation and Nuclear Science, Kyoto University
2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
3

Atomic Energy Research Institute, Kindai University
Kowakae, Higashi-Osaka, Osaka 577-8502, Japan*

Email: nauchi@criepi.denken.or.jp

Two kinds of J ray spectrum measurement are performed. The one is for a critical core of enricheduranium (U) mocked up in Kyoto university critical assembly facility (KUCA). The other is for a U
sample of natural enrichment to obtain microscopic nuclear data at an accelerator neutron source facility(KURNS-LINAC). In KUCA, discrete energy J rays from 2.9 to 5 MeV are observed above prompt
components. In KURNS-LINAC, also discrete energy J rays of resemble spectrum are measured in atime-background region. By comparing the measured spectra to the numerical analyses of production anddecay of isotopes originated in fission of 235U, those discrete gamma rays are identified as those fromdecay of short -lived fission products.

1. Introduction
Fission products (FPs) play significant roles in power reactors. For example, the delayed neutron
emissions from FPs mitigate power transient due to a reactivity insertion and the decay heat of FP may
initiate a severe accident if it is not removed due to the station black out. In these regards, production anddecay of FP must be predicted accurately. For those purposes, the data of the yield and the decay chainsof FPs have been evaluated and compiled in libraries such as JENDL/FPY and FPD-2011 [1]. Thoselibraries have been developed based on J ray spectra measured with scintillators and validated against
measured decay heat [2,3]. However, they are seldom to be validated against isotopic data since J raydata from short-lived FP are scarce.
Two kinds of experiments were conducted in the Kyoto university critical assembly facility (KUCA)
and the LINAC neutron source facility of the institute of integrated radiation and nuclear science, Kyoto
university (KURNS). In KUCA, J ray spectrum was measured with a highly purified germanium (HPGe) detector for a critical core [4,5]. In KURNS-LINAC, U metal sample of the natural enrichment wasirradiated by neutrons of white spectrum and the emitted J rays from the sample were measured with the231- 231 -

JAEA-Conf 2021-001

same HP-Ge [6]. In the two experiments, resemble J ray spectra were measured unexpectedly. In thiswork, the measurement and numerical analyses for the discrete J rays are discussed to see whether themeasured data are feasible for the validation of the yield and the decay chains of FPs.

2. Critical experiment
Details of the critical experiments and the identification of FPs had already been presented [4, 5], so
only essential points are described. Schematic view of the set up is shown in Figure 1. The critical core
was mocked up with fuel plates of uranium (U) - aluminum (Al) alloy, of which 235U enrichment is 93
wt-%. The criticality is adjusted by the control rod position. 428 sheets of the plates were loaded into the
C-core tank of KUCA. The effective core size was about 28 cm x 38 cm x 57 cm. The fuel plates were
immersed in the light water. The core power was adjusted less than 4.6 mW. Outside the tank, a HP-Ge
detector of the 35 % relative efficiency was put. Between the fuel plates and HP-Ge, there was light waterlayer of 60 cm thickness. By the arrangement, the neutron flux was well attenuated in the light water andthe transmission J rays were measured. J ray count rate of was 13 kcps.
J ray pulse height spectra of good resolution were obtained [4, 5]. In the spectra, 2.223 and 7.724 MeV J
rays from radiative capture of hydrogen (1H) and 27Al, respectively, are prominent. The spectrum inenergy region from 2.9 to 3.9 MeV is magnified in Figure 2. The base continuum component of thespectrum is due to fission prompt J rays.
Above the continuum spectrum, discrete energy J rays are found. Distinct peaks are of the photoelectric, the single escape, and the double-escape components of J rays from 27Al(n,J) reactions. However,peaks of fewer count rates are observed. By comparison of the small peaks to the calculation describedin Section 4, the peaks are considered to be the components due to short lived FPs such as 87,88Br, 89Kr,
90,90m,91Rb, 95,97,98Y, 136Te. Since 93 wt% -235U metal fuel was used in the water, almost all the FP wereoriginated in fission of 235U. As for 90Rb, the J ray peak of 4136 keV is overwrapped 27Al(n,J) components.
However, they were confirmed by the measurement posterior to the critical operation. Instead, J rays ofhalf-life shorter than 1 minutes could not be measured posterior to (from one to three minutes) that due
to the statistical fluctuation. It is the advanced feature of the measurement under the critical condition to
enable detections of J rays from FPs of half-life shorter than 1 min ( 97, 98Y, for example). Whereas, due
to the prompt components, the peak to base ratio was small.
㻟

㻞

㻯㼛㼡㼚㼠

㻥㻣㼅
㻟㻚㻣㻡㼟
㻟㻚㻞㻤㻤

㻝
㻜㻚㻥
㻜㻚㻤
㻜㻚㻣
㻜㻚㻢

㻥㻣㼅
㻟㻚㻣㻡㼟
㻟㻠㻜㻝
㻤㻡㻿㼑
㻤㻝㻚㻣㼟
㻟㻟㻥㻢

㻥㻡㼅
㻟㻡㻣㻢
㻝㻜㻚㻟㼙

㻥㻝㻾㼎
㻌㻤㻥㻷㼞 㻡㻤㻚㻞㼟㻟㻚㻞㼙 㻟㻢㻜㻜
㻌㻟㻡㻟㻟

㻤㻣㻮㼞
㻡㻡㻚㻢㻡㼟
㻠㻝㻤㻝㼛㼢㼑㼞㼣㼞㼍㼜㼜㼑㼐㻌㼎㼥㻌㻭㼘㻔㼚㻘㼓㻕

㻥㻝㻾㼎
㻡㻤㻚㻞㼟
㻠㻜㻣㻤
㻝㻟㻢㼀㼑
㻝㻣㻚㻡㼟
㻟㻞㻟㻡

㻥㻜㼙㻾㼎
㻠㻚㻟㼙㼕㼚
㻟㻟㻝㻣

㻜㻚㻡
㻜㻚㻠
㻜㻚㻟

Figure 1. Side view of the critical core and HP-Ge
detector. Yellow lines are of aluminum alloy.

㻥㻤㼅㻜㻚㻡㻠㻤㼟
㻠㻠㻡㻜
㻥㻜㻾㼎
㻝㻡㻤㼟
㻠㻟㻢㻢

㻤㻤㻮㼞
㻝㻢㻚㻡㼟 㻥㻞㻾㼎㻠㻡㻢㻟 㻠㻚㻠㻥㼟㻠㻢㻟㻤㻌㻌㻥㻜㻾㼎
㻌㻌㻝㻡㻤㼟
㻌㻌㻠㻝㻟㻢
㻻㼢㼑㼞㼣㼞㼍㼜㼜㼑㼐㻌㼎㼥㻌㻭㼘

㻟㻜㻜㻜

㻟㻡㻜㻜

㻠㻜㻜㻜
㻼㼡㼘㼟㼑㻌㻴㼑㼕㼓㼔㼠㻌㻔㼗㼑㼂㻕㻠㻡㻜㻜

Figure 2. Measured J ray spectrum for critical
core.
232

- 232 -

JAEA-Conf 2021-001

3. Microscopic Nuclear Data Measurement
The original purpose of the microscopic nuclear data measurement was to obtain J ray spectrum
from reactions of 238U induced by neutrons of thermal and resonance energies. The energy of the incident
neutron is determined by the time of flight (TOF) of the neutron between the target and the sample.
At KURNS-LINAC facility, accelerated electrons were injected onto a tungsten (W) target andbremsstrahlung rays were radiated. Then photo-nuclear reactions were induced, and fast neutrons were
emitted. The neutrons were moderated to the resonance and thermal energy regions in the light water
surrounding the W target. U metal sample was set effectively 11.3 m from the W target. The size of thesample was 4 cm x 4cm and the thickness was 2.91 g/cm2. For the TOF measurement, pulsed neutron
source was used with frequency of 50 Hz. The same HP-Ge was set 5 cm from the sample. The detector
was shadowed from the neutron and the J ray flash from the W target with a collimator. The energy
dependent J ray detection efficiency was measured by detection of the J ray spectrum from the radiative
capture of 35Cl.
The TOF spectrum was shown in Figure 3. Events of the earlier TOF is generally induced by thefaster neutrons. The events induced by fast neutrons of energy greater than keV could not be measured
since influence by the J ray flash from the W target still remains in earlier TOF. The peak spectrum in
Figure 3 corresponds to the radiative capture at the resonance neutron energy. In the lower energy, broad
peak structure is found. It is called “thermal peak”. After the decay out of the thermal peak, flatcomponent is found, which is treated as the time background components for the original purpose. In thepresent work, the J ray pulse height spectrum in the time background region was focused on. Figure 4
shows the pulse height spectrum. Since the time region was after the thermal neutron decays out, prompt
J rays from radiative captures and the fissions do not exist. Accordingly, this component was considered
due to decay of FP of half-life longer than 10 ms. By comparison of the peaks to the data in Figure 2, thesame J rays were measured although 92Rb, 88Br, and 136Te are not observed. Generally, the counting
statistics is poorer in this time-background condition. Instead, the better peak to base ratio was given
thanks to the attenuation of the prompt J rays from the radiative capture and the fission reactions.
㻺㼑㼡㼠㼞㼛㼚㻌㼑㼚㼑㼞㼓㼥㻌㼞㼑㼓㼕㼛㼚㻢㻚㻢㻣㼑㼂
㼑㼜㼕㻙㼠㼔
㼠㼔㼑㼞㼙㼍㼘
㼎㼍㼏㼗

㻞㻜㻜

㻯㼛㼡㼚㼠

㼏㼛㼡㼚㼠㻌㻛㻌㼏㼔

㻝㻜㻢

㼒㼍㼟㼠
㻟㻢㻚㻢㻡㼑㼂
㻟㻢㻚㻢㻡㻙㻞㻜㻚㻤㻣㼑㼂㻞㻜㻚㻤㻣㼑㼂
㻞㻜㻚㻤㻣㻙㻢㻚㻢㻣㼑㼂

㻝㻜㻜
㻥㻜
㻤㻜
㻣㻜
㻢㻜

㻥㻤㼅㻌㻜㻚㻡㻡㼟㻌㻟㻟㻝㻜 㻤㻥㻷㼞㻌㻟㻚㻝㻡㼙㻌㻟㻡㻟㻟㻥㻜㻾㼎㻌㻝㻡㻤㼟㻌㻟㻟㻝㻣㻥㻣㼅㻥㻡㼅㻌㻝㻜㻚㻟㼙㻌㻟㻡㻣㻢
㻟㻚㻣㻡㼟
㻥㻝㻾㼎
㻟㻞㻤㻢
㻥㻝㻾㼎
㻡㻤㻚㻠㼟
䚷㻡㻤㻚㻠㼟
㻠㻜㻣㻤䚷㻟㻡㻥㻥㻚㻣
㻥㻡㻿㼞 㻥㻜㻾㼎㻞㻠㼟 㻝㻡㻤㼟
㻠㻜㻣㻡 㻠㻝㻟㻢 㻥㻜㻾㼎
㻝㻡㻤㼟
㻠㻟㻢㻢

㻥㻤㼅
㻜㻚㻡㻡㼟
㻠㻠㻡㻜

㻡㻜

㻝㻜㻡

㻠㻜
㻥㻣㼅
㻟㻚㻣㻡㼟
㻟㻠㻜㻝
㻤㻡㻿㼑
㻤㻝㻚㻣㼟
㻟㻟㻥㻢

㻟㻜

㻝㻜㻜
㻝㻜㻜㻜
㼀㻻㻲㻔㼏㼔㻕㻘㻌㻝㻜㻜㻜㻜㼏㼔㻩㻌㻞㻜㼙㼟㻌

㻞㻜

㻝㻜㻠

Figure 3. Time of flight spectrum for estimationof energy of incident neutron.

㻟㻜㻜㻜

㻟㻡㻜㻜

㻠㻜㻜㻜
㻼㼡㼘㼟㼑㻌㻴㼑㼕㼓㼔㼠㻌㻔㼗㼑㼂㻕㻠㻡㻜㻜

Figure 4. J ray spectrum at time background.
Nuclides in labels denote E-decay parents ofdelayed J rays.
233- 233 -

JAEA-Conf 2021-001

0.72% of the metal sample was 235U and that was also irradiated by the thermal neutron. Accordingly,
a part or almost all FPs might be generated by fission of 235U. However, it should be also noted again thatneutron flux in energy region higher than keV had never been characterized by the J ray flash.
Accordingly, there is a possibility that some FPs are generated by fission of 238U induced by neutrons
faster than the threshold energy (~MeV).

4. Comparison to Calculation
In the both measurements in KUCA and KURNS-LINAC, the neutron flux was low so thatradiative captures of produced FPs can be neglected. In such cases, the activities of FPs are determinedby the radioactive decay and the fission rate. In this work, it was assumed that all FPs were produced byfission of 235U induced by the thermal neutrons. The depletion after the instant irradiation was calculatedby Bateman’s method [7] in an exact manner, based on the JENDL/FPY & FPD-2011 library. Then theactivity was integrated for time lengths of the neutron irradiation and of the J ray measurement. For thecritical experiments, the flux variation with time was also considered. For the microscopic datameasurement, fission rate was assumed as the continuous wave operation and the measurement time wasalso continuous, in spite that the fission occurred periodically induced by the pulsed neutron source andonly J ray spectrum during the time background region was measured. Then using the data in
JENDL/FPD-2011, the number of emissions of the discrete J rays were deduced. The measured J rays
were identified by comparison to the calculated J rays of larger emission rates as shown in Figures 2 and4.
Quantitative analyses were also performed. For the critical experiments, the J ray pulse heightspectrum was simulated with the MCNP-5 code [8] and the AcelibJ40 library [9] based on JENDL-4.0.
At first, the fission reaction distribution in each fuel plate was estimated by a neutron transport calculationin the manner of the eigenvalue calculation. In the next step, the J rays of each energy shown in Figure 5
were transported from the fuel. The spatial distribution of the J ray emission is treated similar to that of
calculated fission reaction rates. In the calculation, the threshold energy of the J ray transport was set
1.6MeV outside the HP-Ge detector. Inside the detector, it was set down to 3 keV. For the tally, photon- electron coupled transport was done and the pulse height response was calculated. The calculated countrate for the pulse height was compared to the measured one in Figure 5.
For the microscopic data measurement, the experimental count rates were divided by the energy
dependent efficiency measured using the 35Cl(n, J) reaction. The deduced ratio is considered proportional
to the number of photon emission. Then, the calculated one was compared to the deuced one in Figure 6.
In the both figures, the absolute values of C/E do not make sense since the absolute efficiency
was not known in the critical core and the continuous wave operation was assumed in the micro scopic
data measurements. C/E for each J ray depends on FP and J ray energy. However, variation of C/E with
FP is resembled each other in the two measurements. That indicates significant part of the discrete energy
J rays were radiated from the same FP produced by the fission reactions of the same fissionable nuclide.
Accordingly, the two kinds of experiment are considered worth to be investigated further to obtain thereference data for validating FP yield and decay data libraries.

234- 234 -

JAEA-Conf 2021-001

㻼㼡㼘㼟㼑㻴㼑㼕㼓㼔㼠㻔㼗㼑㼂㻕㻦㻲㻼㻠㻢㻟㻣㻚㻣㻦㻌㻥㻞㼋㻾㼎㻼㼡㼘㼟㼑㻴㼑㼕㼓㼔㼠㻔㼗㼑㼂㻕㻦㻲㻼㻠㻢㻟㻣㻚㻣㻦㻌㻥㻞㼋㻾㼎㻠㻡㻢㻞㻚㻤㻦㻌㻤㻤㼋㻮㼞㻠㻡㻢㻞㻚㻤㻦㻌㻤㻤㼋㻮㼞㻠㻠㻡㻜㻚㻞㻦㻌㻥㻤㼋㼅㻠㻠㻡㻜㻚㻞㻦㻌㻥㻤㼋㼅㻠㻟㻢㻡㻚㻥㻦㻌㻥㻜㼋㻾㼎㻠㻟㻢㻡㻚㻥㻦㻌㻥㻜㼋㻾㼎㻠㻝㻟㻡㻚㻡㻦㻌㻥㻜㼋㻾㼎㻗㻭㼘 㻺㼛㼠㻌㼍㼢㼕㼘㼍㼎㼘㼑㻌㼐㼡㼑㻌㼠㼛㻌㻭㼘㻔㼚㻘J㻕㻌㼛㼢㼑㼞㼣㼞㼍㼜㻠㻝㻟㻡㻚㻡㻦㻌㻥㻜㼋㻾㼎㻗㻭㼘㻠㻜㻣㻤㻚㻞㻦㻌㻥㻝㼋㻾㼎㻠㻜㻣㻤㻚㻞㻦㻌㻥㻝㼋㻾㼎㻟㻡㻥㻥㻚㻣㻦㻌㻥㻝㼋㻾㼎㻟㻡㻥㻥㻚㻣㻦㻌㻥㻝㼋㻾㼎㻟㻡㻣㻢㻚㻜㻦㻌㻥㻡㼋㼅㻟㻡㻣㻢㻚㻜㻦㻌㻥㻡㼋㼅㻟㻡㻟㻞㻚㻥㻦㻌㻤㻥㼋㻷㼞㻟㻡㻟㻞㻚㻥㻦㻌㻤㻥㼋㻷㼞㻟㻠㻜㻝㻚㻟㻦㻌㻥㻣㼋㼅㻟㻠㻜㻝㻚㻟㻦㻌㻥㻣㼋㼅㻟㻟㻝㻣㻚㻜㻦㻌㻥㻜㼙㻾㼎㻟㻟㻝㻣㻚㻜㻦㻌㻥㻜㼙㻾㼎㻟㻞㻤㻣㻚㻢㻦㻌㻥㻣㼋㼅㻟㻞㻤㻣㻚㻢㻦㻌㻥㻣㼋㼅㻟㻞㻟㻡㻚㻝㻦㻌㻝㻟㻢㼀㼑㻟㻞㻟㻡㻚㻝㻦㻌㻝㻟㻢㼀㼑㻞㻥㻠㻝㻚㻟㻦㻌㻥㻤㼋㼅㻞㻥㻠㻝㻚㻟㻦㻌㻥㻤㼋㼅㻞㻣㻡㻝㻚㻟㻦㻌㻤㻢㼋㻮㼞㻞㻣㻡㻝㻚㻟㻦㻌㻤㻢㼋㻮㼞
㻝㻱㻙㻡

㻝㻱㻙㻠

㻜㻚㻜㻜㻜㻝

㻯㻛㻱㻌㼛㼚㻌㼏㼛㼡㼚㼠㻌㼞㼍㼠㼑㻜㻚㻜㻜㻝㻯㻛㻱㻌㼛㼚㻌㼑㼙㼕㼟㼟㼛㼕㼚㻌㼞㼍㼠㼑

Figure 5. Comparison of calculated photo-electric

Figure 6. Comparison of calculated number ofpeak counting to that by the measurement in KUCA.

J ray emission to that by measurement in
KURNS-LINAC.

㻠㻢㻟㻣㻚㻣㻦㻌㻥㻞㼋㻾㼎㻠㻡㻢㻞㻚㻤㻦㻌㻤㻤㼋㻮㼞㻠㻠㻡㻜㻚㻞㻦㻌㻥㻤㼋㼅㻠㻟㻢㻡㻚㻥㻦㻌㻥㻜㼋㻾㼎㻠㻝㻟㻡㻚㻡㻦㻌㻥㻜㼋㻾㼎㻠㻜㻣㻤㻚㻞㻦㻌㻥㻝㼋㻾㼎㻟㻡㻥㻥㻚㻣㻦㻌㻥㻝㼋㻾㼎㻟㻡㻣㻢㻚㻜㻦㻌㻥㻡㼋㼅㻟㻡㻟㻞㻚㻥㻦㻌㻤㻥㼋㻷㼞㻟㻠㻜㻝㻚㻟㻦㻌㻥㻣㼋㼅㻟㻟㻝㻣㻚㻜㻦㻌㻥㻜㼙㻾㼎㻟㻞㻤㻣㻚㻢㻦㻌㻥㻣㼋㼅㻟㻞㻟㻡㻚㻝㻦㻌㻝㻟㻢㼀㼑㻞㻥㻠㻝㻚㻟㻦㻌㻥㻤㼋㼅㻞㻣㻡㻝㻚㻟㻦㻌㻤㻢㼋㻮㼞㻹㼍㼕㼚㻌㼕㼟㼛㼠㼛㼜㼑㻻㼠㼔㼑㼞㻌㼕㼟㼛㼠㼛㼜㼑㼟㻜㻞㻌㻝㻜㻙㻡

㻠㻌㻝㻜㻙㻡

㻢㻌㻝㻜㻙㻡

㻤㻌㻝㻜㻙㻡

㻯㻛㻱㻌㼛㼚㻌㼏㼛㼡㼚㼠㻌㼞㼍㼠㼑㻝㻌㻝㻜㻙㻠

Figure 7 Contribution of other FPs to the count rate of target FP.
For the validation, additional measurements or improvements of the methods are required. For
the critical core in KUCA-C, experimental methods to determine the energy dependent J ray detection
efficiency is desired. Besides, analyses of the prompt components by the radiative capture and the fission
are mandatory. Whereas, for the microscopic data measurement in KURNS-LINAC, quantification ofneutron flux in energy region higher than 500 keV was required to see whether fission reaction of 238U
was significant or not. Besides, the numerical analysis of the production of FP in the pulse mode operationand the decay of them in the time region posterior to decay out of the thermal neutrons must be achieved.
Another issue is the resolution of the HP-Ge detector. Various energies of J ray are radiated from FPs
produced by the fission of 235U. Consider a measurement of with a HP-Ge detector of a resolution of s
5 keV. With the detector, J rays of energies within the error of s5 keV is measured in a peak spectrum.
Based on the JENDL/FPY & DPF-2011, the contribution of the main isotope and the other isotopes arecalculated. As shown in Figure 7, considerable fraction of counts of a peak are attributed to the othercomponents. In that sense, validation of FP yield and decay data should not be focused only on a single
J ray but comprehensive set of evaluated FPs should be validated against the measured data .

5. Conclusion
235- 235 -

JAEA-Conf 2021-001

At KUCA, J rays radiated from short-lived FP were measured in a critical core under the intense
background of prompt components of fission and radiative capture reactions. At KURNS -LINAC, they
were also measured for metallic U sample irradiated by white neutron source in the time region where
the thermal neutrons decayed out. The energy of the J rays and corresponding FPs were identified bycomparison of the measurement to the depletion calculations based on JENDL/FPY & FPD-2011 library.
J ray count rates and emission rates were numerically calculated and compared to the measured data of
KUCA and KURNS-LINAC, respectively. The ratio of the calculation to the measurement varied with
FPs. However, the trend of the ratio for the KUCA experiment is resemble to that for the KURNS-LINAC
experiment. The results indicate that the FP J rays produced by fission reaction of 235U induced by thermal
neutrons are the major components in the both measurements. The both measurement techniques aresuperior in detection of short-lived FPs compered to measurements posterior to neutron irradiation.
Accordingly, the J ray spectroscopy for the critical core and that for a uranium sample posterior to decay- out of the thermal neutrons are promising to give reference data to validate the FP yield and decay data.
For that, necessary improvements of the methods shall be conducted.

References1)

Katakura, J., JENDL FP Decay Data File 2011 and Fission Yields Data File 2011, JAEAData/Code 2011-025, 2012.

2)

Algora, A., et al., Reactor Decay Heat in 239Pu: Solving the J Discrepancy in the 4–3000-s
Cooling Period, Phys. Rev. Lett., vol.105, 2010, p. 202501.

3)

Dickens, J.K., et al., Fission Product Energy Release for Time following Thermal Neutron
Fission of 239Pu. Nucl. Sci. Eng., vol. 78, 1981, p.126.
Nauchi, Y., Sano, T., Unesaki, H., et al., Spectrum measurement of gamma ray from KUCA-C

4)

critical core, Proceedings of Fall meeting of Atomic Energy Society of Japan, On-Line,
5)

September, 2020.
Nauchi, Y., Sano, T., Takahashi, Y., et al., Gamma Ray Spectroscopy of Fission Product in

8)

Fuel Assembly, Proceedings of the 41th Annual Meeting of Institute of Nuclear Material
Management, Japan Chapter, On-Line, October, 2020.
Nauchi, Y., Hori, J., and Sano, T., Quantification of Gamma Ray Emission from Capture
Reaction of Uranium-238, KURNS Progress report 2019, 2020, CO2-2.
Bateman, H., The solution of a system of differential equations occurring in the theory ofradioactive transformations. Proc. Cambridge Phil. Soc. 15, 1910, p.15.
X-5 Monte Carlo Team., MCNP TM – A General Monte Carlo N-Particle Transport Code,

9)

Version 5, LA-UR-03-1987, Los Alamos National Laboratory (LANL) (2003).
Sato, T., Niita, K., Matsuda, N., et al., Particle and Heavy Ion Transport Code System PHITS,

6)
7)

Version 2.52, J. Nucl. Sci. Technol., vol. 50, no.9, 2013, pp. 913-923.

Acknowledgements   The experiments at KUCA and KURNS-LINAC had been carried out in part under the visiting
researcher’s program of the Institute for Integrated Radiation and Nuclear Science, Kyoto 8niversity.

236- 236 -