scholarly journals Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 719
Author(s):  
Misato Shimbashi ◽  
Shingo Yokoyama ◽  
Yasutaka Watanabe ◽  
Tsutomu Sato ◽  
Tsubasa Otake ◽  
...  
Keyword(s):  
Magnesium Silicate ◽  
The Philippines ◽  
Radioactive Waste Disposal ◽  
Ultramafic Rocks ◽  
Barrier Materials ◽  
Clastic Sediments ◽  
Natural Silicate ◽  
Alkaline Conditions ◽  
Precipitation Reactions ◽  
Drill Holes

In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (14C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments.

scholarly journals Microbial impacts on 99mTc migration through sandstone under highly alkaline conditions relevant to radioactive waste disposal

2017 ◽  
Vol 575 ◽  
pp. 485-495 ◽  
Author(s):  
Sarah L. Smith ◽  
Christopher Boothman ◽  
Heather A. Williams ◽  
Beverly L. Ellis ◽  
Joanna Wragg ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Alkaline Conditions

Mineralogy and Petrology of Serpentine

2007 ◽  
Author(s):  
Earl B. Alexander ◽  
Roger G. Coleman ◽  
Todd Keeler-Wolfe ◽  
Susan P. Harrison
Keyword(s):  
Ultramafic Rock ◽  
Magnesium Silicate ◽  
Ultramafic Rocks ◽  
Chemical Compositions ◽  
Silicate Minerals ◽  
Excess Iron ◽  
Serpentine Minerals ◽  
Similar Chemical ◽  
Serpentine Mineral ◽  
Mineralogical Compositions

“Serpentine” is used both as the name of a rock and the name of a mineral. Mineralogists use “serpentine” as a group name for serpentine minerals. Petrologists refer to rocks composed mostly of serpentine minerals and minor amounts of talc, chlorite, magnetite, and brucite as serpentinites. The addition of “-ite” to mineral names is common practice in petrologic nomenclature. For instance, quartzite is a name for a rock made up mostly of quartz. Serpentinites are rocks that form as a result of metamorphism or metasomatism of primary magnesium–iron silicate minerals. This entails the replacement of the primary silicate minerals by magnesium silicate serpentine minerals and the concentration of excess iron in magnetite. “Mafic” is a euphonious term derived from magnesium and ferric that is used for dark colored rocks rich in ferromagnesian silicate minerals. “Ultramafic” is used when the magnesium–ferrous silicate minerals compose >90% of the total rock. Olivine, clinopyroxene, and orthopyroxene are the minerals in primary ultramafic rocks, with minor amounts of plagioclase, amphibole, and chromite. Ultrabasic has been used by some geologists in referring to ultramafic rocks. The most common ultramafic rocks are harzburgite, containing <75% olivine and 25% orthopyroxene; dunite, with 100% olivine; and lherzolite, which has 75% olivine, 15% orthopyroxene, and >10% clinopyroxene, with or without plagioclase. Very small amounts of chromite are present in all of the mantle ultramafic rocks (Coleman 1971). The alteration of primary ultramafic rocks to serpentine mineral assemblages is incremental due to episodic invasion of water into the ultramafic rock. It is difficult to distinguish and map the gradations from primary ultramafic rock to serpentinite. Because of this difficulty in distinction, we prefer to use the term ultramafic or serpentinized peridotite for all gradations to serpentinite. Pedologists and botanists commonly group serpentinites with primary ultramafic rocks and refer to these substrates as serpentine because all of them have similar chemical compositions. As will become apparent later, there is great variability in the mineralogical compositions of these rocks and the soils derived from them.

Performance and Safety Assessment of the Co-Location of the Near Surface Radioactive Waste Disposal Facilities and Borehole Disposal Concept in the Philippines

2013 ◽  
Author(s):  
Maria Visitacion Palattao ◽  
Edmundo Vargas ◽  
Rolando Reyes ◽  
Carl Nohay ◽  
Alfonso Singayan ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Water Content ◽  
Safety Assessment ◽  
Technical Assistance ◽  
Clayey Soil ◽  
Dispersion Model ◽  
The Philippines ◽  
Radioactive Waste Disposal ◽  
Energy Agency ◽  
Near Surface

The Philippine Nuclear Research Institute (PNRI) in collaboration with the interagency technical committee on radioactive waste has been undertaking a national project to find a final solution to the country’s low to intermediate level radioactive waste. The strategy adopted was to co-locate 2 disposal concepts that will address the types of radioactive waste generated from the use of radioactive materials. This strategy is expected to compensate for the small volumes of waste generated in the Philippines as compared to countries with big nuclear energy programs. It will also take advantage of the benefits of a shared infrastructure and R&D work that accompany such project. The preferred site selected from previous site selection and investigations is underlain by highly fractured “andesitic volcaniclastics” mantled by residual clayey soil which act as the aquifer or water bearing layer. Results of investigation show that the groundwater in the area is relatively dilute and acidic. Springs at the lower elevations of the footprint also indicate acidic waters. The relatively acidic water is attributed to the formation of sulfuric acid by the oxidation of the pyrite in the andesite. A preliminary post closure safety assessment was carried out using the GMS MODFLOW and HYDRUS softwares purchased through the International Atomic Energy Agency (IAEA) technical assistance. Results from MODFLOW modeling show that the radionuclide transport follows the natural gradient from the top of the hill down to the natural discharge zones. The vault dispersion model shows a circular direction from the vaults towards the faults and eventually to the creeks. The contaminant transport from borehole shows at least one confined plume from the borehole towards the creek designated as Repo1 and eventually follows downstream. The influx of surface water and rainfall to the disposal vault was modeled using the HYDRUS software. The pressure head and water content at the base of the foundation layer and the bottom of the concrete is where a significant reduction in water content can be observed. It is also noted that water content and pressure remain constant after one year.

scholarly journals Ultramafic rocks of the Aganozero chromium ore deposit (South Karelia) as a non-conventional magnesium-silicate raw material for the production of new ceramic materials

2019 ◽  
Author(s):  
V.P. Ilyina ◽  
P.V. Frolov
Keyword(s):  
Raw Materials ◽  
Practical Interest ◽  
Magnesium Silicate ◽  
Ceramic Materials ◽  
Raw Material ◽  
Ultramafic Rocks ◽  
Practical Application ◽  
Ore Deposit ◽  
Chromium Ore ◽  
Technological Level

Ultramafic rocks of the Aganozero chromium ore deposit located in South Karelia are of practical interest as a high-Mg raw material for industrial application. The preliminary results of the study of high-Mg rocks and minerals from the Aganozero deposit for the production of new materials are reported. The high technological level and economic efficiency of the ceramic materials produced, based on Karelia’s high-Mg rocks and industrial minerals, were achieved by reducing energy consumption and simplifying the technological process. The practical application of local types of mineral products will increase the raw materials potential for the production of various types of refractories and industrial ceramics.

Durability Analysis on Reactive Powder Concrete as Barrier Materials for Low-Level Radioactive Waste Disposal

2013 ◽  
Vol 284-287 ◽  
pp. 1295-1299
Author(s):  
Mei Ling Chuang ◽  
Wei Hsing Huang
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Gas Permeability ◽  
Radioactive Waste Disposal ◽  
Disposal Site ◽  
Reactive Powder Concrete ◽  
Barrier Materials ◽  
Low Level ◽  
Reactive Powder ◽  
Low Level Radioactive Waste

Reactive powder concrete (RPC) has been proposed as barrier materials for the construction of engineered barrier in a low-level radioactive waste disposal site. The durability characteristics of RPC in such applications become paramount for the success of the containment of the wastes. The adverse environmental conditions at the disposal site could attack concrete barrier material and result in degradation of the material. Laboratory tests were conducted on RPC with various compositions to investigate the physical and durability properties of RPC. The effects of the addition of cement, silica fume, quartz powder, silica sand, steel fiber, and 2 levels of water-to-binder ratio (W/B = 0.25 and 0.30) on the properties of RPC specimens were investigated. Experimental results indicate that the long-term durability of RPC is significantly improved with the hydration of pozzolanic materials, which produces a very dense structure and thus exhibiting improved durability. The coefficient of permeability of RPC matrix determined using gas permeability apparatus demonstrated that RPC has much lower permeability than that of ordinary concrete. Heat-treating of concrete at 80°C accelerates the hydration process of RPC and shows enhanced physical and durable characteristics, as demonstrated by the chloride penetration test results.

scholarly journals On a System Approach to the Selection of Safety Barriers for the Disposal of Radioactive Waste Class 3 and 4

2020 ◽  
Vol 12 (3) ◽  
pp. 54-65
Author(s):  
D. I. Pavlov ◽  
◽  
O. A. Ilina ◽  
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
System Approach ◽  
Radioactive Waste Disposal ◽  
Barrier Materials ◽  
Safety Barrier ◽  
Safety Barriers ◽  
Technical Specifications ◽  
Selection Of

The article describes different designs and materials of engineered safety barriers (ESB) for radioactive waste disposal facilities, systematizes the functions and technical specifications of EBS and based on a system approach proposes safety barrier materials and designs for the disposal of radioactive waste class 3 and 4.

scholarly journals Water Migration and Swelling in Engineered Barrier Materials for Radioactive Waste Disposal

2021 ◽  
pp. 1-20
Author(s):  
Joanna McFarlane ◽  
Lawrence M. Anovitz ◽  
Michael C. Cheshire ◽  
Victoria H. DiStefano ◽  
Hassina Z. Bilheux ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Water Migration ◽  
Barrier Materials ◽  
Engineered Barrier

Swelling pressures of compacted bentonites from diffuse double layer theory

2004 ◽  
Vol 41 (3) ◽  
pp. 437-450 ◽  
Author(s):  
Snehasis Tripathy ◽  
Asuri Sridharan ◽  
Tom Schanz
Keyword(s):  
Radioactive Waste ◽  
Double Layer ◽  
Expansive Soils ◽  
Chemical Properties ◽  
Weighted Average ◽  
Swelling Pressure ◽  
Radioactive Waste Disposal ◽  
Diffuse Double Layer ◽  
Barrier Materials ◽  
Double Layer Theory

The swelling pressures of several compacted bentonites (MX80, Febex, and Montigel) proposed for use as barrier materials in storing high-level radioactive waste in many countries were determined from the Gouy–Chapman diffuse double layer theory. The swelling pressures thus determined were compared with the reported experimental swelling pressures. The study revealed that, in general, at low compaction dry densities of the bentonites, the experimental swelling pressures are less than their theoretical counterparts, with the reverse trend at high compaction dry densities. Based on the reported experimental results for the three bentonites, relationships between the nondimensional midplane potential function, u, and the nondimensional distance function, Kd, were established. New equations for the swelling pressure were proposed on the basis of the diffuse double layer theory and the reported experimental data to compute swelling pressures of compacted bentonites. The suitability of the new equations was also verified with additionally reported experimental swelling pressures from three other bentonites (Kunigel V1, Kunigel, and bentonite S-2) that have been also proposed for use as barrier materials. Very good agreement was found in all the cases between the experimental swelling pressures and the swelling pressures obtained using the proposed equations. The use of the proposed equations is based on the weighted average valency of the cations present in bentonites, since the valency of the cations present has a significant influence on the swelling pressure.Key words: clays, compressibility, swelling pressure, expansive soils, chemical properties, radioactive waste disposal.

Discussion on Very Low-Level Radioactive Waste near Surface Disposal

2013 ◽  
Vol 807-809 ◽  
pp. 1207-1210 ◽  
Author(s):  
Hai Ying Chen ◽  
Chun Ming Zhang ◽  
Shao Wei Wang ◽  
Qiao Feng Liu ◽  
Jing Ru Han
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Early Period ◽  
Radioactive Waste Disposal ◽  
Nuclear Facilities ◽  
Near Surface ◽  
Barrier Materials ◽  
Low Level ◽  
Low Level Radioactive Waste ◽  
Natural Barriers

Radioactive waste disposal is one of the most sensitive environmental problems. As the arriving of decommissioning of early period nuclear facilities in China, large amounts of very low-level radioactive waste will be produced inevitably. The domestic and abroad definitions about very low-level radioactive waste and its disposal were introduced, and then siting principles of near surface disposal of very low-level radioactive waste were discussed. The near surface disposal sites’ natural barriers were analyzed from the crustal structure and the radionuclide adsorption characteristics of natural barriers. The near surface disposal sites’ engineering barriers were analyzed from the repository design and the repository barrier materials selection. Finally, the improving direction of very low-level radioactive waste disposal was proposed, which would promote the study of very low-level radioactive waste disposal in China.

scholarly journals The Grimsel Test Site – more than 35 years of underground research

2021 ◽  
Vol 1 ◽  
pp. 239-240
Author(s):  
Andrew J. Martin ◽  
Ingo Blechschmidt
Keyword(s):  
Feasibility Studies ◽  
Field Testing ◽  
Test Site ◽  
Radioactive Waste Disposal ◽  
Diffusion Experiment ◽  
Training Centre ◽  
Barrier Materials ◽  
In Situ Experiments ◽  
Grimsel Test Site ◽  
And Migration

Abstract. Nagra and its international partners have been conducting underground research projects at the Grimsel Test Site (GTS, https://www.grimsel.com, last access: 8 November 2021) for more than 35 years. The results have been incorporated directly into modelling, safety and engineering feasibility studies necessary for the siting and construction of deep geological repositories. Various types of experiments are carried out at the GTS, each involving field testing, laboratory studies, design and modelling tasks, thus integrating all scientific aspects. Projects are typically planned over a 5 year period with the option to extend depending on the latest findings from the experiment. In the current 5 year programme (2019–2023) new phases of running in situ experiments using radionuclides were started and include the Long-Term Diffusion experiment (LTD) and the Colloid Formation and Migration project (CFM). A completely new experiment studying the migration of C-14 and I-129 in aged cement (CIM) was also initiated. Other experiments focusing mostly on engineered barrier materials were continued such as the Material Corrosion Test (MaCoTe), which is studying anaerobic corrosion of candidate canister materials in bentonite (Fig. 1). Also, a 1:1 scale experiment studying the high-temperature (>175∘C) effects on bentonite materials (HotBENT project) was started last year. In this paper we provide an overview of the CIM, LTD and MaCoTe projects, including key findings so far. In addition to research, the GTS, as part of the Grimsel Training Centre (GTC), is also used as an education platform for knowledge transfer to the next generation of scientists and engineers in the area of radioactive waste disposal and geosciences.

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