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Minari, Eriko*; Kabasawa, Satsuki; Mihara, Morihiro; Makino, Hitoshi; Asano, Hidekazu*; Nakase, Masahiko*; Takeshita, Kenji*
Journal of Nuclear Science and Technology, 60(7), p.793 - 803, 2023/07
Times Cited Count：2 Percentile：53.91(Nuclear Science & Technology)Kochiyama, Mami; Sakai, Akihiro
JAEA-Technology 2022-009, 56 Pages, 2022/06
JAEA-Technology-2022-009.pdf:4.15MB
It is necessary to evaluate radioactivity inventory in wastes before disposal of low-level radioactive wastes generated from dismantling research reactors. It is efficient for owners of each research reactor to use a common radioactive evaluation method in order to comply with the license application for disposal facility. In this report, neutron transport and activation calculations were carried out for the Rikkyo University research reactor in order to examine a common radioactivity evaluation method for burial disposal of radioactive wastes generated by dismantling. We adopted the neutron transport codes DORT and MCNP and the activation code ORIGEN-S with cross-section libraries based on JENDL-4.0 and JENDL/AD-2017. The radioactivity concentrations obtained by the radiochemical analysis and both calculation codes were in agreement by 0.4 to 3 times. Therefore, by appropriately considering this difference, the radioactivity evaluation method by DORT, MCNP and ORIGEN-S can be applied to the radioactivity evaluation for buried disposal. In order to classify wastes from dismantling by clearance or buried disposal method according to their radioactivity levels, we also created radioactivity concentration distributions in the concrete area and graphite thermal column area.
Ochs, M.*; Dolder, F.*; Tachi, Yukio
Applied Geochemistry, 136, p.105161_1 - 105161_11, 2022/01
Times Cited Count：4 Percentile：66.78(Geochemistry & Geophysics)Various types of radioactive wastes and environments contain organic substances that can stabilize the aqueous complexes with radionuclides and therefore lead to a decrease of sorption. The present study focuses on testing a methodology to quantify sorption reduction factors (SRFs) in the presence of organic ligands for cement systems. Three approaches for the estimation of SRFs; (1) analogy with solubility enhancement factors, (2) radionuclide speciation based on the thermodynamic calculations, and (3) experimental sorption data in ternary systems, were coupled and tested for the representative organic ligands (ISA and EDTA) and selected key radionuclides (actinides). Our approach allows to critically evaluate the dependence of SRFs for various systems on the chosen method of quantification, in accordance with the data availability for a given systems. The reliable SRFs can only be derived from the sorption measurements in ternary systems. SRF often need to be derived in the absence of such direct evidence, and estimations need to be made based on analogies and speciation information. However, such estimates may be subject to substantial uncertainties.
Cantarel, V.; Lambertin, D.*; Labed, V.*; Yamagishi, Isao
Journal of Nuclear Science and Technology, 58(1), p.62 - 71, 2021/01
Times Cited Count：4 Percentile：35.51(Nuclear Science & Technology)The gas production of wasteforms is a major safety concern for encapsulating active nuclear wastes. For geopolymers and cements, the H
produced by radiolytic processes is a key factor because of the large amount of water present in their porous structure. Herein, the gas composition evolution around geopolymers was monitored on line under 
Co gamma irradiation. Transient evolution of the hydrogen production yield was measured for samples with different formulations. The rate of its evolution and the final values are consistent with the presence of a chemical reaction of the pseudo-first order consuming hydrogen in the samples. The results show this phenomenon can significantly reduce the hydrogen source term of geopolymer wasteform provided their diffusion constant remains low. Lower hydrogen production rates and faster kinetics were observed with geopolymers formulations in which pore water pH was higher. Besides hydrogen production, a steady oxygen consumption was observed for all geopolymers samples. The oxygen consumption rates are proportional to the diffusion constants estimated in the modelization of hydrogen recombination by a pseudo first order reaction.
Ito, Mitsuo; Obara, Kazuhiro; Toida, Yukio*; Suzuki, Daisuke; Gunji, Katsubumi*; Watanabe, Kazuo
JAERI-Review 2004-007, 65 Pages, 2004/03
JAERI-Review-2004-007.pdf:5.53MB
no abstracts in English
Nakano, Masahiro; Arigane, Kenji; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki; Sakuraba, Naotoshi; Oba, Nagamitsu
JAERI-Tech 2003-072, 92 Pages, 2003/08
JAERI-Tech-2003-072.pdf:6.99MB
The decommissioning plan of the Japan Research reactor No2(JRR-2), decommissioning activities until the first half of phase-3, radioactive wastes and exposure dose of workers are described in this report. Since the first criticality in October 1960, JRR-2 had been operated about 36 years for various experiments. However, JRR-2 was permanent shutdown in December 1996 based on JAERI's long term plan, and the decommissioning of the JRR-2 was started in August 1997. Decommissioning of the JRR-2 was planed for 11 years from 1997 to 2007 and the program was divided into 4 phases. The decommissioning activities of the phase-1, phase-2 and the first half of phase-3 had already completed as planned in March 1998, February 2000, March 2002, respectively. The decommissioning activities of the later half of Phase-3 (dismantling of the reactor cooling systems) are carrying out at present time with planed 2002 and 2003 fiscal years.
NUCEF 2001 Symposium Working Group
JAERI-Conf 2002-004, 714 Pages, 2002/03
JAERI-Conf-2002-004.pdf:69.13MB
This volume contains 94 papers presented at the 3rd NUCEF International Symposium NUCEF 2001 held on October 31 - November 2, 2001, in Tokai, Japan, following the 1st symposium NUCEF'95 (Proceedings: JAERI-Conf 96-003) and the 2nd symposium NUCEF'98 (Proceedings: JAERI-Conf 99-004). The theme of this symposium was " Scientific Basis for Criticality Safety, Separation Process and Waste Disposal". The papers were presented in oral and poster sessions on following research fields: (1) Separation Process, (2) TRU Chemistry, (3) Radioactive Waste Disposal, (4) Criticality Safety.
Bamba, Tsunetaka; K.P.Hart*
JAERI-Tech 96-024, 67 Pages, 1996/05
no abstracts in English
; *;
Nihon Genshiryoku Gakkai-Shi, 23(5), p.338 - 341, 1981/00
Times Cited Count：0 Percentile：0.02(Nuclear Science & Technology)no abstracts in English
; Wadachi, Yoshiki
JAERI-M 8044, 19 Pages, 1979/01
no abstracts in English
Co and 
Cs in the Sand Layer -; ; Wadachi, Yoshiki
JAERI-M 7642, 15 Pages, 1978/04
no abstracts in English
Okamoto, Yoshihiro; Nagai, Takayuki; Kobayashi, Hiromi*; Hatakeyama, Kiyoshi*; Shiwaku, Hideaki
no journal, ,
Chemical correlation analysis between different elements in the simulated nuclear waste glass samples was performed by using imaging XAFS technique. We have used this new technique in the study of chemical behavior of platinoid elements in the borosilicate nuclear waste glass. In the present study, the simulated nuclear waste glass prepared by several kinds of conditions were analyzed by the imaging XAFS technique.
Sakai, Akihiro
no journal, ,
Japan Atomic Energy Agency (JAEA) is promoting the project for near surface disposal of low-level radioactive waste generated from research facilities, etc. Since a function to reduce infiltration water into the cover soil is needed at trench facilities for very low-level waste, we are calculating the infiltration water through the cover soil which is installed in various composition and parameters of the impermeable sheet, low permeable soil layer and drainage layer by using the HELP code developed by EPA and a calculation code by two-dimensional finite element method. This report outlines these studies that have been conducted on the impermeable function of the trenching facilities.
