Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Chemical form analysis of reaction products in Cs-adsorption on stainless steel by means of HAXPES and SEM/EDX

Kobata, Masaaki; Okane, Tetsuo; Nakajima, Kunihisa; Suzuki, Eriko; Owada, Kenji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Osaka, Masahiko

Journal of Nuclear Materials, 498, p.387 - 394, 2018/01

https://doi.org/10.1016/j.jnucmat.2017.10.035

In this study, for the understandings of Cesium (Cs) adsorption behavior on structure materials in severe accidents at a light water nuclear reactor, the chemical state of Cs and its distribution on the surface of SUS304 stainless steel (SS) with different Si concentration were investigated by hard X-ray photoelectron spectroscopy (HAXPES) and scanning electron microscope / energy dispersive X-ray spectroscopy (SEM/EDX). As a result, it was found that Cs is selectively adsorbed at the site where Si distributes with high concentration. CsFeSiO is a dominant Cs products in the case of low Si content, mainly formed, while CsSiO and CsSiO are formed in addition to CsFeSiO in the case of high Si content. The chemical forms of the Cs compounds produced in the adsorption process on the SS surface has a close correlation with the concentration and chemical states of Si originally included in SS.

Spontaneous formation of suboxidic coordination around Co in ferromagnetic rutile TiCoO film

Hu, W.*; Hayashi, Koichi*; Fukumura, Tomoteru*; Akagi, Kazuto*; Tsukada, Masaru*; Happo, Naohisa*; Hosokawa, Shinya*; Owada, Kenji; Takahashi, Masamitsu; Suzuki, Motohiro*; et al.

Applied Physics Letters, 106(22), p.222403_1 - 222403_5, 2015/06

https://doi.org/10.1063/1.4921847

New result in the production and decay of an isotope, 113 of the 113th element

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.

Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10

https://doi.org/10.1143/JPSJ.81.103201

An isotope of the 113th element, 113, was produced in a nuclear reaction with a Zn beam on a Bi target. We observed six consecutive decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of Db and Lr both in decay energies and decay times. This indicates that the present decay chain consisted of 113, Rg (Z = 111), Mt (Z = 109), Bh (Z = 107), Db (Z = 105), and Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope 113, of the 113th element.

Experimental study on thermal stratification in compact reactor vessel of sodium cooled fast reactor; Effects of core outlet velocity and temperature difference during scram

Kimura, Nobuyuki; Hayashi, Kenji; Tobita, Akira; Kamide, Hideki; Nagasawa, Kazuyoshi*

JAEA-Research 2010-065, 191 Pages, 2011/03

JAEA-Research-2010-065.pdf:14.57MB

Thermal stratification water experiments using a 1/10th scale model were carried out for an advanced loop type sodium cooled reactor. Experimental parameters were core outlet velocity, temperature difference during scram, and height of the plug which infill the hole at the dipped plates for setup of a fuel handling machine. It was found that the height and the rising speed of stratification interface depended on the Richardson number. Furthermore the temperature gradient of the stratification interface depended on the Peclet number.

Experimental study on thermal stratification in a compact reactor vessel of advanced sodium cooled reactor; Influence of a column-type upper inner structure (UIS) under scram conditions

Kimura, Nobuyuki; Hayashi, Kenji; Tobita, Akira; Kamide, Hideki; Miyake, Yasuhiro*

JAEA-Research 2009-026, 160 Pages, 2009/10

JAEA-Research-2009-026.pdf:15.97MB

Thermal stratification after a scram is one of main thermal loads of a reactor vessel in sodium cooled fast reactor. Water experiments using an 1/10th scaled model were carried out for an advanced loop type sodium cooled reactor. The reactor vessel is highly compact and has an upper inner structure (UIS), which has a slit in radial direction for fuel handling. The jet from core outlet goes through the UIS slit and makes asymmetric and locally high velocity field in the reactor upper plenum. Steep temperature distribution across the stratification interface and temperature fluctuations were found near the UIS slit. It was revealed that they were resulted from the impingement of the jet through the slit at the interface. Parameter experiments showed the characteristics of thermal stratification interface.

Study on mixing behavior in a tee piping and numerical analyses for evaluation of thermal striping

Kamide, Hideki; Igarashi, Minoru*; Kawashima, Shigeyo*; Kimura, Nobuyuki; Hayashi, Kenji

Nuclear Engineering and Design, 239(1), p.58 - 67, 2009/01

https://doi.org/10.1016/j.nucengdes.2008.09.005

Water experiments were carried out for thermal hydraulic aspects of thermal striping in a mixing tee, which has main to branch diameter ratio of 3. Detailed temperature and velocity fields were measured by a movable thermocouple tree and particle image velocimetry. Flow patterns in the tee were classified into three groups, which had own temperature fluctuation profiles. The power spectrum density (PSD) of temperature fluctuation showed an unique profile, which is normalized by St number, when the flow velocity ratio and flow pattern was identical. Numerical simulation based on finite difference method showed alternative vortex development behind the jet from the branch pipe in a case of wall jet. Mixing behavior in the tee was discussed based on the measured data and the simulation.

Transient behavior of gas entrainment caused by surface vortex

Ezure, Toshiki; Kimura, Nobuyuki; Hayashi, Kenji; Kamide, Hideki

Heat Transfer Engineering, 29(8), p.659 - 666, 2008/08

https://doi.org/10.1080/01457630801980574

A compact sodium cooled reactor is one of important candidates as FBRs and has been investigated in the feasibility study of FBR cycle. According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues for reactor design, and it is required to clarify the criterion of gas entrainment at free surface and the tolerance. In the present study, some visualization experiments were performed in a water-air system focusing on the gas entrainment due to surface vortex and its transient phenomena. Influences of horizontal velocity were clarified by the visualization. Time trends of circulation and length of gas core for the intermittent surface vortices were measured by the particle image velocimetry and visualization. It was found that the gas core length extends with time delay to the increase of circulation around the vortex.

Development of geometry measurement technique for complicated flow channel based on optical visualization image

Kobayashi, Jun; Sato, Hiroyuki; Hayashi, Kenji; Kamide, Hideki

JAEA-Technology 2008-026, 30 Pages, 2008/03

JAEA-Technology-2008-026.pdf:8.59MB

High burn-up core in a sodium cooled fast reactor may result in fuel pin deformation due to irradiation, e.g., swelling and bowing. Such deformation will influence thermal hydraulics in a core fuel subassembly, i.e., the highest temperature. Thus it is significant to estimate pin deformation effects. A water experiment was carried out to measure velocity field in a deformed pin bundle by using transparent resin and refractive index matching technique. In the experiment, the deformed pin geometry should be measured as a boundary condition. Here an optical measurement technique of pin bundle geometry was developed. An image of a horizontal cross section of the pin bundle was captured by a camera set on an inclined line to the pin bundle axis. This image was converted to a straight image to the pin bundle axis by taking accounts of refraction at the wall. The positions of deformed pins were well estimated by this method.

Experimental study of gas entrainment phenomena; Developing process of surface vortex

Ezure, Toshiki; Kimura, Nobuyuki; Hayashi, Kenji; Kamide, Hideki

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-12) (CD-ROM), 13 Pages, 2007/09

According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues for the latest fast reactor design. It is required to clarify the criterion of gas entrainment at free surface and the tolerance of gas entrainment. In the present study, some visualization experiments were performed in the water-air system focusing on the gas entrainment due to a surface vortex. The gas entrainment occurs intermittently and the vortex develops and decays in time. Then developing process of the vortex is significant to estimate the gas entrainment phenomena. Multi plane PIV using a scanning mirror was adopted to investigate the temporal and spatial development of velocity around the vortex. The spatial propagation of downward velocity was clarified as the key factors of the vortex development.