Study on Mechanical Influence of Gas Generation and Migration on Engineered Barrier System in Radioactive Waste Disposal Facility

2010 ◽  
Author(s):  
Mamoru Kumagai ◽  
Shuichi Yamamoto ◽  
Kunifumi Takeuchi ◽  
Yukihisa Tanaka ◽  
Michihiko Hironaga
Keyword(s):  
Radioactive Waste ◽  
Time Evolution ◽  
Mechanical Stability ◽  
Water Saturation ◽  
Hydrogen Gas ◽  
Gas Pressure ◽  
Radioactive Waste Disposal ◽  
Gas Generation ◽  
Disposal Facility ◽  
Engineered Barriers

In Japan, some radioactive waste with a relatively higher radioactivity concentration from nuclear facilities is to be packaged in rectangle steel containers and disposed of in subsurface disposal facilities, where normal human intrusion rarely occurs. After the closure of a facility, its pore is saturated with groundwater. If the dissolved oxygen of the pore water is consumed by steel corrosion, hydrogen gas will be generated from the metallic waste, steel containers, and reinforcing bars of concrete mainly by anaerobic corrosion. If the generated gas accumulates and the gas pressure increases excessively in the facility, the facility’s barrier performance might be degraded by mechanical influences such as crack formation in cementitious material or deformation of bentonite material. Firstly, in this study, we assessed the time evolution of the gas pressure and the water saturation in a sub-surface disposal facility by using a multi-phase flow numerical analysis code, GETFLOWS, in which a pathway dilation model is introduced and modified in order to reproduce the gas migration mechanism through the highly compacted bentonite. Next, we calculated the stress applied to the engineered barriers of the facility from the results of the time evolution of the pressure and the saturation. Then, we conducted a mechanical stability analysis of the engineered barriers by using a nonlinear finite element code, ABAQUS, in order to evaluate their performances after the closure of the facility.

Modelling Multi-Phase Flow Phenomena in Concrete Barriers Used for Geological Disposal of Radioactive Waste

2007 ◽  
Author(s):  
Dirk Mallants ◽  
Diederik Jacques ◽  
Janez Perko
Keyword(s):  
Radioactive Waste ◽  
Hydrogen Gas ◽  
Phase Flow ◽  
Gas Generation ◽  
Boom Clay ◽  
In Situ Experiments ◽  
Production Of Hydrogen ◽  
Multi Phase Flow ◽  
Engineered Barriers ◽  
Multi Phase

Gas generation and gas transport phenomena occur in geological repositories of radioactive waste. This has been extensively studied over the past ten years, usually within the framework of international projects (MEGAS, PROGRESS, etc.). These studies indicate that the production of hydrogen by anaerobic corrosion of metals is the most important source for gas generation. Laboratory and in situ experiments carried out at SCK•CEN indicate that, in the presence of Boom Clay (the reference geologic formation for deep disposal studies in Belgium), carbon steel suffers generalised corrosion estimated conservatively at 1 μm y−1. Simulations with the finite difference multi-phase flow code TOUGH2 were carried out in an attempt to quantify the effects of hydrogen gas generation on desaturation of initially saturated concrete components of the disposal gallery and the concomitant expulsion of cementitious pore-water into the surrounding host formation. Several simulation cases were considered and addressed differences in initial water saturation degree of concrete, hydrogen gas generation rate, and material porosity. Several conceptual models have been developed to better understand the phenomena at work in the transport of gas in the cementitious engineered barriers and Boom Clay. Multi-phase flow modelling was found to be helpful to get insight into the phenomenology of coupled water-gas flow in the cementitious engineered barriers. However, modeling the discontinuous variation in the conductivity of the clay relative to the gas (creation of preferential pathways) requires incorporation of geomechanical processes in conventional models based on the laws of two-phase flow.

A hydrochemical and isotopic case study around a near surface radioactive waste disposal

2007 ◽  
Vol 95 (1) ◽  
Author(s):  
Zs. Szántó ◽  
É. Svingor ◽  
I. Futó ◽  
L. Palcsu ◽  
M. Molnár ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Waste Treatment ◽  
Radioactive Waste Disposal ◽  
Ion Chemistry ◽  
Continuous Transition ◽  
Near Surface ◽  
Disposal Facility ◽  
Treatment And Disposal ◽  
Site Characterisation

As part of the site characterisation program for the near surface radioactive waste treatment and disposal facility (RWTDF) at Püspökszilágy, Hungary, water quality and environmental isotope investigations have been carried out. Water samples for major ion chemistry, tritium,The chemical composition of groundwaters presented a continuous transition from waters situated on one side to waters on the top and on the other slope of the disposal suggesting the mixing of the three hydrochemical “endmembers”.Most of δ

scholarly journals UPPER FILLER MATERIAL APPLIED IN CAVERN TYPE RADIOACTIVE WASTE DISPOSAL FACILITY

2016 ◽  
Vol 72 (3) ◽  
pp. 234-248
Author(s):  
Shin-ichi TAKECHI ◽  
Toshiyuki SASAKI ◽  
Kosuke YOKOZEKI ◽  
Hiroshi SHIMBO ◽  
Yoshihiro AKIYAMA ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Filler Material ◽  
Disposal Facility

Planning of Large-Scale In-Situ Gas Generation Experiment in Korean Radioactive Waste Repository

2010 ◽  
Author(s):  
Juyoul Kim ◽  
Sukhoon Kim ◽  
Jin Beak Park ◽  
Sunjoung Lee
Keyword(s):  
Radioactive Waste ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Large Scale ◽  
Radioactive Waste Disposal ◽  
Gas Generation ◽  
Radioactive Waste Repository ◽  
Waste Repository

In the Korean LILW (Low- and Intermediate-Level radioactive Waste) repository at Gyeongju city, the degradation of organic wastes and the corrosion of metallic wastes and steel containers would be important processes that affect repository geochemistry, speciation and transport of radionuclides during the lifetime of a radioactive waste disposal facility. Gas is generated in association with these processes and has the potential threat to pressurize the repository, which can promote the transport of groundwater and gas, and consequently radionuclide transport. Microbial activity plays an important role in organic degradation, corrosion and gas generation through the mediation of reduction-oxidation reactions. The Korean research project on gas generation is being performed by Korea Radioactive Waste Management Corporation (hereafter referred to as “KRMC”). A full-scale in-situ experiment will form a central part of the project, where gas generation in real radioactive low-level maintenance waste from nuclear power plants will be done as an in-depth study during ten years at least. In order to examine gas generation issues from an LILW repository which is being constructed and will be completed by the end of December, 2012, two large-scale facilities for the gas generation experiment will be established, each equipped with a concrete container carrying on 16 drums of 200 L and 9 drums of 320 L of LILW from Korean nuclear power plants. Each container will be enclosed within a gas-tight and acid-proof steel tank. The experiment facility will be fully filled with ground water that provides representative geochemical conditions and microbial inoculation in the near field of repository. In the experiment, the design includes long-term monitoring and analyses for the rate and composition of gas generated, and aqueous geochemistry and microbe populations present at various locations through on-line analyzers and manual periodical sampling. A main schedule for establishing the experiment facility is as follows: Completion of the detailed design until the second quarter of the year 2010; Completion of the manufacture and on-site installation until the second quarter of the year 2011; Start of the operation and monitoring from the third quarter of the year 2011.

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