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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.
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.
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.
Se in concrete rubble by ICP-MS/MSDo, 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.