Simulation of Hydrogeochemical Transport of Low-Level Radioactive Waste Through Engineered Barrier
Date Issued
2011
Date
2011
Author(s)
Tsao, Jui-Hsuan
Abstract
Taiwan has developed nuclear power since 1972. The nuclear power plants provided sufficient electricity but it brought the radioactive waste disposal problem in Taiwan. Thus the successful construction of the final disposal site of nuclear waste is the key to sustainable development for nuclear power. A proposed site for final disposal of low-level radioactive waste (LLRW) located in Daren Township of Taitung County along the southeastern coast has been on the selected list in Taiwan. The Daren Township is hilly terrain and the area is approximate 30,664.5 hectare. Taiwan Power Company proposed to build a tunnel disposal plant according to terrain features of Daren. This study aims to simulate the hydrogeochemical transport of low-level nuclides through engineered barrier and analyze the durability of engineered barrier. The geochemical equilibrium model PHREEQC was applied to simulate the quality of groundwater and selected the major reactions of low-level nuclides. The Simulated results by PHREEQC were used for the input data of the hydrogeochemical transport model HYDROGEOCHEM 5.0. Radionuclides of Cobalt-60, Strontium-90, Iodine-129, Cesium-137, Americium-241 were selected and assumed that the nuclides leaked from the waste container after 100 years of disposal. The simulated results by HYDROGEOCHEM 5.0 show that the contents of concrete engineered barrier remained essentially stability after 300 years. Formation of Ettringite, Friedel`s salt and Thaumasite observed outside concrete engineered barrier due to groundwater intrusion causing the swollen concrete and destructing the engineered barrier. The increased permeability accompanied with increase of concrete crack. Concrete cracks accelerated the rate of degradation. In addition, the flow rate and direction were altered due to the formation of Ettringite and Thaumasite in simulation area. The simulated results of radionuclides transport show that the concentration of nuclides of which the half-life is less than 30 years such as Cobalt-60, Strontium-90 and Cesium-137 decreased with time. The concentration of radionuclides with long half-life such as Iodine-129 and Americium-241 were stable. Because of the rate of groundwater flow was relatively small, the radionuclides were mostly confined within concrete engineered barrier, only a small amount of concentration diffused to the backfill of tunnel system.
Subjects
Daren Township
low-level radioactive waste
concrete
engineered barrier
hydrogeochemical transport
groundwater
SDGs
Type
thesis
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