With the increasing use of fission-type nuclear power generation, particularly high-levels radioactive nuclear waste are generated, so the safe use of nuclear energy requires proper disposal of high-level radioactive nuclear waste. The selected treatment method is deep geological disposal. Therefore, underground research laboratory (URL) to prepare for deep geological disposal will also be carried out. Corrosion of metallic materials, which are closely related to the safety of URL, is the focus of this research project. This study selected monitoring techniques for URL and developed a rough monitoring scheme for temperature and resistivity in URL. In this study, corrosion-temperature and corrosion-resistivity monitoring experiments were carried out in different bentonite samples to simulate the experiments in URL. The results show that the self-compensating high-precision inductance corrosion monitoring system and multifunction soil corrosion rate measurer proved to be a good system for monitoring the corrosion-temperature and corrosion-resistivity of metals. However, the life span limitation makes them unable to meet the requirements of URL. The results also show that the corrosion rate of metal in bentonite is positively correlated with temperature. The existing electrochemical probes are suitable for monitoring the corrosion rate, but not suitable for soil corrosion rate monitoring.

<p> This is a study of the groundwaters and their associated rocks and minerals from the Lac du Bonnet batholith at the Underground Research Laboratory (URL), Pinawa, Manitoba, to assess the water-rock interaction in crystalline rocks by using Sr, O and U-series isotopes. Emphasis is also placed on the development of the analytical techniques.</p> <p> A high precision analytical technique of U-series isotopes has been developed in this study by using solid-source mass spectrometry. A precision of better than 1% (2σ) is achieved in determining the 234U/238U and 230Th/234U ratios using 10^-8 g of U and 10^-11 g of 230Th. The potential applications of this method is demonstrated by dating small speleothem samples and the results agree well with those of α-spectrometry. This method also applies well to precise determination of the 234U/238U ratios in groundwaters and igneous rocks and minerals using small quantities of samples. However, precise measurements of 230Th in igneous rocks and minerals are limited by the large 232Th tail in the Th mass spectrum. Even better precision is achievable if pure Th spike is used.</p> <p> An ICP-MS isotope dilution method is also developed for fast and precise determination of Sr concentrations in groundwater samples. A precision of 1% is routinely achieved by taking into account the dead-time effect of the Channel Electron Multiplier (CEM) and the sample-to-spike ratios.</p> <p> The isotope results of both the groundwaters and the host rocks and minerals have revealed the processes of water-rock interaction and water mixing through the history of the batholith. Strontium isotope systematics of the rocks and their constituent minerals have shown that Sr loss occurred on whole-rock scale during both the high-temperature alteration (about 2300 Ma ago) and the low-temperature alteration which lasted at least 450 Ma. The Sr loss is most pronounced in plagioclase of altered samples. Uranium-series results indicate the disequilibrium of both whole-rock samples and minerals, and migration of U on whole-rock scale in, at least, the last million years.</p> <p> The Sr and O isotopic results have shown that the groundwaters from the three sub-horizontal, successively deeper fracture zones (FZ) have distinct isotopic signature: 87Sr/86Sr= 0.715 to 0.719 and 𝛿18O=-13o/oo for FZ-3; 87Sr/86Sr= 0.720 to 0.729 and 𝛿18O=-13 to -20o/oo for FZ-2; 87Sr/86Sr= 0.730 to 0.738 and 𝛿18O=-13 to -17o/oo for FZ-1. Uranium-series results show that all the groundwaters are highly enriched in 234U and the 234U/238U activity ratios range from 2.6 to 7.7. Mixing of three groundwaters is indicated by the Sr and O isotopes and the elemental chemistry. The three end-members are fresh surface water, the deep fresh (possibly glacial melt) groundwater and the deep saline groundwater.</p> <p> Comparison between the rocks and associated groundwaters shows that Sr isotopic equilibrium exists between plagioclase of altered samples and the groundwaters. This similarity indicates the vulnerable mineral phase control, such as plagioclase in this case, of the isotopic signatures, hence, chemistry of the groundwaters.</p> / Thesis / Master of Science (MSc)

Underground Research Laboratories (URLs) allow geoscientific in-situ experiments at large scale. At the Mont Terri URL in Switzerland, international research groups conduct numerous experiments in parallel. The measured and simulated data as well as research results obtained from them are highly relevant as they improve the general understanding of geological processes, for example in the context of radioactive waste disposal. Unfortunately, the data obtained at the test site is often only available to researchers who are directly involved in a particular experiment. Furthermore, typical visualisation techniques of such data by domain scientists often lack spatial context and accessing and exploring the data requires prior technical knowledge and a high level of effort.We created a digital replica of the Mont Terri URL and thereby implemented a prototype of a Virtual Experiment Information System that integrates highly heterogeneous data from several different sources. It allows accessing and exploring the relevant data embedded in its spatial context without much prior technical knowledge. Both, simulation results and observation data are displayed within the same system. The 4D visualisation approach focuses on three exemplary experiments conducted at Mont Terri and is easily transferable to other experiments or even other URLs. The Unity Game Engine has been used to develop the prototype. This allowed to build the application for various output devices like desktop computers or Virtual Reality hardware without much additional effort. The implemented system reduces the technical effort required to access and explore highly relevant research data and lowers the cognitive effort usually needed to gain insights from measurements, simulation models and context data. Moreover, it promotes exchange among research groups by enabling interactive visualisations embedded in the URL’s spatial context. In addition, a future use of the system for the communication of scientific methods and results to stakeholders or the general public is plausible.

In the published article, there was an error concerning the FE Experiment. Incorrect information was used regarding the heaters’ power and temperature. A correction has been made to Chapter 3: Visualisation of Selected Experiments, Sub-section 3.3 “Full- Scale Emplacement Experiment”, Paragraph 1. The sentence previously stated: “They work with up to 1,500W each and emit heat up to 195°C.” The corrected sentence now states: “They work with up to 1,350W each and emit heat up to 135°C.” The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.