Study on the evaluation methodology of the radioactivity concentration in low-level radioactive concrete wastes generated from JPDR

Aono, Ryuji; Haraga, Tomoko; Kameo, Yutaka

JAEA-Technology 2024-006, 48 Pages, 2024/06

JAEA-Technology-2024-006.pdf:1.77MB

In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. In this work, we studied the evaluation methodology of the radioactivity concentrations in concrete waste generated from JPDR. In order to construct the evaluation methodology of the radioactivity concentration, the validity of the evaluation methods was confirmed by mainly theoretical calculation and using the result of radiochemical analysis. Correcting the theoretical calculations using results of nuclide analysis, it is possible to evaluate the radioactivity concentrations of nuclides preliminary selected.

Study on radioactivity evaluation method of research reactors using DORT and MCNP codes

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.

Online measurement of the atmosphere around geopolymers under gamma irradiation

Cantarel, V.; Lambertin, D.*; Labed, V.*; Yamagishi, Isao

Journal of Nuclear Science and Technology, 58(1), p.62 - 71, 2021/01

https://doi.org/10.1080/00223131.2020.1801531

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.

JRR-2 decommissioning activity, 1

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.

Japan-Australia co-operative program on research and development of technology for the management of high level radioactive wastes: Phase II (1990-1995)

Bamba, Tsunetaka; K.P.Hart*

JAERI-Tech 96-024, 67 Pages, 1996/05

JAERI-Tech-96-024.pdf:2.5MB

no abstracts in English

Radialogical Safety Studies on the Ground Disposal of Radioactive Wastes; Distribution and Migration of Radionuclides is an Aerated Zone

; Wadachi, Yoshiki

JAERI-M 8044, 19 Pages, 1979/01

JAERI-M-8044.pdf:0.7MB

no abstracts in English

Development of HCl-free analytical methods for Se in concrete rubble by ICP-MS/MS

Do, V. K.; Banjarnahor, I. M.; Ota, Yuki; Tanaka, Yasuyuki; Furuse, Takahiro; Tanaka, Kosuke

no journal, , 

The presentation summarizes the results of the development of analytical method for Se in concrete rubble using inductively coupled plasma triple quadrupole mass spectrometry (ICP-MS/MS). Se has been conventionally measured by a liquid scintillation counter (LSC). However, LSC measurement is time-consuming and susceptible to the radioactive interferences from highly radioactive nuclides (Sr, Cs, etc.) coexisting in the samples. In this regard, ICP-MS/MS is a powerful technique, which can effectively eliminate the interferences. In this study, we have developed an HCl-free chemical separation to recover Se and remove the Br isobar. Chemical recovery for Se was around 90%. Also, we investigated the best conditions to measure Se by ICP-MS/MS. The method detection limit of 0.1 Bq/g was achieved indicating that the developed method meets the requirements for the measurement of Se in the radioactive rubble collected at the Fukushima Daiichi Nuclear Power Plant.

Disposal project of low-level radioactive waste generated from research facilities, etc.; Development for impermeable function of cover soil of trench disposal facility

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.