Development of a statistical evaluation method for core hot spot temperature in sodium-cooled fast reactor under natural circulation conditions

Doda, Norihiro; Igawa, Kenichi*; Iwasaki, Takashi*; Murakami, Satoshi*; Tanaka, Masaaki

Nuclear Engineering and Design, 410, p.112377_1 - 112377_15, 2023/08

https://doi.org/10.1016/j.nucengdes.2023.112377

To enhance the safety of sodium-cooled fast reactors, the decay heat in the core must be removed by natural circulation even if the AC power supply to the forced circulation equipment is lost. Under natural circulation conditions, sodium flow is driven by buoyancy, and flow velocity and temperature distribution influence each other. Thus, it is difficult to evaluate the core hot spot temperature by deterministically considering the uncertainties affecting flow and heat. In this study, a statistical evaluation method is developed for the core hot spot temperature by using Monte Carlo sampling methods. The applicability of the core hotspot evaluation method was confirmed in three representative events during natural circulation decay heat removal operations in loop-type sodium-cooled fast reactors.

Development of a design optimization framework for sodium-cooled fast reactors; Development of coupled analysis control function

Doda, Norihiro; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iwasaki, Takashi*; Murakami, Satoshi*; Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 27, 6 Pages, 2022/06

As a part of the development of the "Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)" to automatically optimize the life cycle of innovative nuclear reactors including fast reactors, ARKADIA-design is being developed to support the optimization of fast reactor design in the conceptual stage. ARKADIA-Design consists of three systems (Virtual plant Life System (VLS), Evaluation assistance and Application System (EAS), and Knowledge Management System (KMS)). A design optimization framework controls the cooperation between the three systems through the interfaces in each system. This paper reports on the development status of the "VLS interface," which has a control function of coupling analysis codes in VLS.

Survival probabilities of charmonia as a clue to measure transient magnetic fields

Iwasaki, Sachio*; Jido, Daisuke*; Oka, Makoto; Suzuki, Kei

Physics Letters B, 820, p.136498_1 - 136498_6, 2021/09

https://doi.org/10.1016/j.physletb.2021.136498

We investigate time evolution of -wave charmonium populations under a time-dependent homogeneous magnetic field and evaluate survival probabilities of the low-lying charmonia to the goal of estimating the magnetic field strength at heavy-ion collisions. Our approach implements mixing between different spin eigenstates and transitions to radially excited states. We show that the survival probabilities can change even by an extremely short magnetic field. Furthermore, we find that the survival probabilities depend on the initial spin states. We propose the sum of the survival probabilities over spin partners as an observable insensitive to the initial states. We also find that the sum can be approximately given as a function of with a duration time and the maximum strength of the magnetic field .

A Review of quarkonia under strong magnetic fields

Iwasaki, Sachio*; Oka, Makoto; Suzuki, Kei

European Physical Journal A, 57(7), p.222_1 - 222_14, 2021/07

https://doi.org/10.1140/epja/s10050-021-00533-5

We review the properties of quarkonia under strong magnetic fields. The main phenomena are (i) mixing between different spin eigenstates, (ii) quark Landau levels and deformation of wave function, (iii) modification of potential, and (iv) the motional Stark effect. For theoretical approaches, we review (i) constituent quark models, (ii) effective Lagrangians, (iii) QCD sum rules, and (iv) holographic approaches.

Cross-shell excitations in Ca studied with fusion reactions induced by a reaccelerated rare isotope beam

Ash, J.*; Iwasaki, Hironori*; Mijatovi, T.*; Budner, T.*; Elder, R.*; Elman, B.*; Friedman, M.*; Gade, A.*; Grinder, M.*; Henderson, J.*; et al.

Physical Review C, 103(5), p.L051302_1 - L051302_6, 2021/05

https://doi.org/10.1103/PhysRevC.103.L051302

no abstracts in English

Intercomparison of numerical atmospheric dispersion prediction models for emergency response to emissions of radionuclides with limited source information in the Fukushima Dai-ichi Nuclear Power Plant accident

Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.

Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10

https://doi.org/10.1016/j.atmosenv.2019.116830

The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.

Hadronic Paschen-Back effect in charmonium

Iwasaki, Sachio; Oka, Makoto; Suzuki, Kei*; Yoshida, Tetsuya*

AIP Conference Proceedings 2130, p.050001_1 - 050001_8, 2019/07

https://doi.org/10.1063/1.5118418

We find a novel phenomenon induced by the interplay between a strong magnetic field and finite orbital angular momenta in hadronic systems, which is analogous to the Paschen-Back effect observed in the field of atomic physics. This effect allows the wave functions to drastically deform. We discuss anisotropic decay from the deformation as a possibility to measure the strength of the magnetic field in heavy-ion collision at LHC, RHIC and SPS, which has not experimentally been measured. As an example we investigate charmonia with finite orbital angular momentum in a strong magnetic field. We calculate the mass spectra and mixing rate. To obtain anisotropic wave functions, we apply the cylindrical Gaussian expansion method, where the Gaussian bases to expand the wave functions have different widths along transverse and longitudinal directions in the cylindrical coordinate.

Hadronic Paschen-Back effect

Iwasaki, Sachio; Oka, Makoto; Suzuki, Kei*; Yoshida, Tetsuya*

Physics Letters B, 790, p.71 - 76, 2019/03

https://doi.org/10.1016/j.physletb.2018.10.024

We find a novel phenomenon induced by the interplay between a strong magnetic field and finite orbital angular momenta in hadronic systems, which is analogous to the Paschen-Back effect observed in the field of atomic physics. This effect allows the wave functions to drastically deform. We discuss anisotropic decay from the deformation as a possibility to measure the strength of the magnetic field in heavy-ion collision at LHC, RHIC and SPS, which has not experimentally been measured. As an example we investigate charmonia with finite orbital angular momentum in a strong magnetic field. We calculate the mass spectra and mixing rate. To obtain anisotropic wave functions, we apply the cylindrical Gaussian expansion method, where the Gaussian bases to expand the wave functions have different widths along transverse and longitudinal directions in the cylindrical coordinate.

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

https://doi.org/10.1051/epjconf/201919800003

New precise measurement of muonium hyperfine structure interval at J-PARC

Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

https://doi.org/10.1007/s10751-016-1381-7