Key Issues Identified From Project TRU-2 on the Generic Co-Location Concept of Transuranic (TRU) Waste and High-Level Radioactive Waste (HLW) Repositories in Japan

2007 ◽  
Author(s):  
Andrew J. Martin ◽  
Shigeki Kuroda ◽  
Keiji Morimoto ◽  
Gento Kamei ◽  
Masao Shiotsuki
Keyword(s):  
Radioactive Waste ◽  
Cementitious Materials ◽  
Separation Distance ◽  
Energy Agency ◽  
High Level Radioactive Waste ◽  
Key Issues ◽  
Single Complex ◽  
Materials Used ◽  
High Level ◽  
Reciprocal Influences

The Federation of the Electric Power Companies of Japan (FEPC) and the Japan Atomic Energy Agency (JAEA) have been collaborating with relevant organisations to promote the safe geological disposal of transuranic (TRU) waste following the already established disposal policy for high-level radioactive waste (HLW) in Japan. A result of this intensive collaborative effort was the production of a recent progress report (TRU-2) which describes the generic R&D for TRU-waste disposal in Japan. In order to improve feasibility and reduce costs and the burden on siting, the concept of co-locating TRU-waste and HLW repositories in a single complex was assessed in detail and compared with the results from several other countries that have also looked at co-location disposal. Heat from HLW, high pH plume(s) from the large amounts of cementitious materials used in the engineered barrier system (EBS) of TRU waste, and nitrates and organic materials in certain types of TRU waste were identified as critical reciprocal influences that might degrade the performance of the TRU/HLW co-location disposal system over the long-term. It was shown that these reciprocal influences could be avoided by establishing a separation distance between the two repositories of approximately 300 meters.

scholarly journals Distinguishing between more and less suitable bentonites for storage of high-level radioactive waste

Clay Minerals ◽  
2016 ◽  
Vol 51 (2) ◽  
pp. 289-302 ◽  
Author(s):  
S. Kaufhold ◽  
R. Dohrmann
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Swelling Pressure ◽  
Point Of View ◽  
Dry Density ◽  
Swelling Clay ◽  
High Level Radioactive Waste ◽  
Key Issues ◽  
The Individual ◽  
High Level

AbstractOne of today's big challenges is to store safely the increasing amount of high-level radioactive waste (HLRW) in the world. In some of the concepts devised for this challenge, bentonite, a natural swelling clay, plays a key role in encasing the canisters containing the waste. The use of bentonite as a geotechnical barrier in HLRWrepositories is a new venture; specifications to ensure either optimum performance or that a minimum standard is reached at least do not exist yet. The present study summarizes relevant research and discusses possible HLRW-bentonite specifications. The importance of these specifications for any given repositories has to be assessed on a case by case basis, depending on the concept being employed and any special circumstances for the individual repositories.Ten key issues were identified which were used to discuss bentonite specifications. In some of these key issues the optimum bentonite performance depended more on processing and production (compaction) than on the bentonite type (e.g.swelling pressure and thermal conductivity). In contrast, in some of the other key issues, the type of bentonite was found to influence possible specifications: the bentonite should not alter its mineral composition or its geotechnical parameters such as the swellability. Therefore, the bentonite should contain neither soluble nor reactive phases (e.g.organic matter, pyrite, gypsum). The structural Fe content of the smectites should be small because of the lesser stability and greater reactivity of the Fe-rich bentonites. Also, a large layer-charge density of the swelling clay minerals leads to less corrosion at the iron–bentonite interface (relevant if iron canisters are used). The hydraulic conductivity and swelling pressure can be tailored by compaction of the bentonite resulting in different dry densities. From an engineering point of view, a bentonite with least dependence of the hydraulic conductivity/swelling pressure on the dry density would be best. Using a bentonite which has been investigated extensively over many years means less uncertainty compared to unknown materials.

scholarly journals Alteration of compacted GMZ bentonite by infiltration of alkaline solution

Clay Minerals ◽  
2016 ◽  
Vol 51 (2) ◽  
pp. 237-247 ◽  
Author(s):  
Chen Bao ◽  
Guo Jiaxing ◽  
Zhang Huixin
Keyword(s):  
Radioactive Waste ◽  
Alkaline Solution ◽  
Chemical Properties ◽  
Swelling Pressure ◽  
Cementitious Materials ◽  
Gmz Bentonite ◽  
High Level Radioactive Waste ◽  
Buffer Material ◽  
Porosity And Permeability ◽  
High Level

AbstractConcepts for geological disposal of high-level radioactive waste usually include bentonite buffer materials. Numerous studies have been performed with most usingWyoming bentonite. Gaomiaozi (GMZ) bentonite has been selected as a potential buffer/backfill material for the deep geological repository of high-level radioactive waste in China. In this context, the highly alkaline environment induced by cementitious materials in the repository is likely to alter montmorillonite, the main clay mineral in GMZ bentonite. This alteration may result in deterioration of the physical and/or chemical properties of the buffer material. To acquire quantitative data which would allow us to assess the dissolution of montmorillonite and changes in the diffusivity of hydroxide ions as well as their effects on the swelling pressure and permeability of the compacted GMZ bentonite, an experimental study was conducted under highly alkaline (NaOH solutions with various pH values were used), simulated groundwater conditions. The GMZ bentonite also contains cristobalite which may also have been dissolved. The microstructure of the compacted bentonite samples after the experiments was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDX) was carried out to identify mineralogical changes. At pH >13, the permeability of specimens increased significantly; the swelling potential decreased with increasing pH. Furthermore, the pore volume and pore size of GMZ bentonite changed when exposed to alkaline solution, resulting in an increase in porosity and permeability. The main alteration mechanisms of compacted GMZ bentonite undergoing infiltration by highly alkaline solution are likely to be dissolution and modifications in terms of the microstructure and mineralogy.

Evaluated and Estimated Solubility of Some Elements for Performance Assessment of Geological Disposal of High-Level Radioactive Waste Using Updated Version of Thermodynamic Database

2010 ◽  
Author(s):  
Akira Kitamura ◽  
Reisuke Doi ◽  
Yasushi Yoshida
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Safety Assessment ◽  
Thermodynamic Database ◽  
Energy Agency ◽  
Geological Disposal ◽  
High Level Radioactive Waste ◽  
Five Elements ◽  
High Level ◽  
Aqueous Species

Japan Atomic Energy Agency (JAEA) established the thermodynamic database (JAEA-TDB) for performance assessment of geological disposal of high-level radioactive waste (HLW) and TRU waste. Twenty-five elements which were important for the performance assessment of geological disposal were selected for the database. JAEA-TDB enhanced reliability of evaluation and estimation of their solubility through selecting the latest and the most reliable thermodynamic data at present. We evaluated and estimated solubility of the 25 elements in the simulated porewaters established in the “Second Progress Report for Safety Assessment of Geological Disposal of HLW in Japan” using the JAEA-TDB and compared with those using the previous thermodynamic database (JNC-TDB). It was found that most of the evaluated and estimated solubility values were not changed drastically, but the solubility and speciation of dominant aqueous species for some elements using the JAEA-TDB were different from those using the JNC-TDB. We discussed about how to provide reliable solubility values for the performance assessment.

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