Circumstances of establishment of regulations for near surface disposal of radioactive waste generated from research facilities, etc.

Sakai, Akihiro

Dekomisshoningu Giho, (64), p.24 - 33, 2023/05

Japan Atomic Energy Agency (JAEA) has proceeded with the project of near surface disposal of radioactive waste generated from research facilities, etc. as the implementing body. On the other hand, Nuclear Regulation Authority (NRA) has established the safety regulations and standards for the operation of the disposal facilities. This report outlines the disposal project of JAEA and the development of the regulations and standards for the disposal by NRA.

Disposal project for LLW and VLLW generated from research facilities in Japan; A Feasibility study for the near surface disposal of VLLW that includes uranium

Sakai, Akihiro; Hasegawa, Makoto; Sakamoto, Yoshiaki; Nakatani, Takayoshi

Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.98_1 - 98_4, 2016/11

The radioactivity of uranium-bearing waste contaminated by refined uranium increases with the production of its progeny on a long-term timescale. Therefore, the long-term safety concept of the near surface disposal of uranium-bearing waste is very important. The Japan Atomic Energy Agency (JAEA) examines disposal safety by controlling the average uranium radioactivity concentration in each section of disposal facility and performing safety assessment for very conservative assumptions.

Mechanism of state-specific enhancement in photon-stimulated desorption as studied using a polarization-dependent technique

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Wu, G.*; Kitajima, Yoshinori*

Surface Science, 593(1-3), p.310 - 317, 2005/11

https://doi.org/10.1016/j.susc.2005.06.076

Using a newly developed rotatable time-of-flight mass spectrometer(R-TOF-MS) and polarized synchrotron radiation, orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids have been investigated. Reported will be polarization-angle dependencies of TOF mass spectra, high-resolution electron- and ion-NEXAFS in condensed chlorobenzene.

Substitution effect on orientation of organosilicon compounds (CH)SiX (X = F, Cl, Br, I, NCO) as studied using NEXAFS spectroscopy

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.*; Uddin, M. N.*

Journal of Physics; Condensed Matter, 17(36), p.5453 - 5466, 2005/09

https://doi.org/10.1088/0953-8984/17/36/002

The orientation nature of multilayer organosilicon compounds has been investigated by measuring the dependence of the Si K-shell near-edge X-ray absorption fine structures (NEXAFS) on the polarization angle. Two approaches helped to elucidate the orientation mechanism: the substitution effect and the deposition-rate dependence. The orientation angles of Si-X bond axes were obtained for trimethylsilyl halides, (CH)SiX (X =F Cl Br I NCO, condensed on Cu(111) at a low (82 K) temperature: the angles are 60, 73, 61, 55, and 55 degrees with respect to the surface normal, for X =F, Cl, Br, I, and NCO, respectively. Chloride (X =Cl) produces the most parallel tilt angle. The specific orientation nature of chloride is attributed to its strong dipole moment as well as the regular tetrahedron shape of the molecule. The molecular volumes calculated verify this view. Furthermore, deposition rates are found to greatly influence the growth manner: namely, high deposition rates led to a slightly perpendicular orientation of Si-X bond axis.

Relativistic band-structure calculations for CeTIn(T=Ir and Co) and analysis of the energy bands by using tight-binding method

Maehira, Takahiro; Hotta, Takashi; Ueda, Kazuo; Hasegawa, Akira*

Journal of the Physical Society of Japan, 72(4), p.854 - 864, 2003/04

https://doi.org/10.1143/JPSJ.72.854

In order to investigate electronic properties of recently discovered heavy fermion superconductors CeTIn (T=Ir and Co), we employ the relativistic linear augmented-plane-wave (RLAPW) method to clarify the energy band structures and Fermi surfaces of those materials.The obtained energy bands mainly due to the large hybridization between Ce and In 5 states well reproduce the Fermi surfaces consistent with the de Haas-van Alphen experimental results. For the purpose, we construct a tight-binding model for CeTIn by including - and - hoppings as well as - hybridization, which are expressed by the Slater-Koster integrals, determined by the direct comparison with the band-calculation result. Similarity and difference between CeIrIn and CeCoIn are discussed based on the obtained tight-binding model, suggesting a significant importance of the effect of crystalline electric field to understand the difference in electronic properties among CeTIn.

Initial free surface instabilities on a high speed water jet simulating a liquid-metal target

Ito, Kazuhiro*; Tsuji, Yoshiyuki*; Nakamura, Hideo; Kukita, Yutaka*

Fusion Technology, 36(1), p.69 - 84, 1999/07

no abstracts in English

Safety demonstration test for the disposal of very low level concrete waste

Abe, Masayoshi; Okoshi, Minoru; Yoshimori, Michiro

Dekomisshoningu Giho, 0(15), p.50 - 58, 1996/12

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_15.pdf

no abstracts in English

International Atomic Energy Agency co-operated research programme on the safetyassessment of near-surface radioactive waste disposal facilities(NSARS) results for test case 1(earth trench case)

Takahashi, Tomoyuki; ; Kimura, Hideo; Matsuzuru, Hideo

JAERI-M 91-216, 31 Pages, 1992/01

JAERI-M-91-216.pdf:0.77MB

no abstracts in English

Outline of the disposal of very low level concrete waste in JAEA

Tsuji, Tomoyuki

no journal, , 

Japan Atomic Energy Agency (JAEA), who conducted the demonstration test on a safe dismantling of Japan Power Demonstration Reactor (JPDR) in Nuclear Science Research Institute, has been performing the safe demonstration test of near-surface disposal of very low level (VLL) concrete waste arising from JPDR dismantling. Approximately 1,700 tons of VLL concrete wastes were placed in a simple disposal facility, of which dimensions are 45 m16 m and 3.5 m in depth without any engineered barrier, and covered with soil of 2.5 m thickness. The safe demonstration test of near-surface disposal of VLL concrete waste consists of a operation stage (FY 1995-1996) and a management stage (FY 1996-2024). In the operation stage, radiation dose around the disposal facility was measured, and radioactivity concentrations in groundwater and soil were analyzed. After we proceeded the management stage of disposal, radiation monitoring was continued additionally for 3 years in the management stage. An inspection such as no outflow, crack and subsidence of the covered soil is conducted at once a week. The radiation monitoring data is planned to storage properly by management department until the finishing of management stage, and an inspection data is stored in accordance with the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors.