Sub-surface corrosion research on rock bolt system, perforated SS sheets and steel sets for the Yucca Mountain Repository — Quarterly technical report No. 2

This report encompasses the work done for second quarter in accordance to cooperative agreement of UCCSN for the Task 019 “Subsurface Corrosion Research on Rock Bolt System, Perforated SS Sheets and Steel Sets for the Yucca Mountain Repository”, the objective of which was proposed earlier, to conduct corrosion research and predict the durability of rock-bolts and other underground metallic roof supports. We have recently started working on oxidation tests using Thermogravimetric Analyzer, stress corrosion cracking/hydrogen embrittlement studies on rock bolts, other support materials including bench mark materials. In this quarterly report we will discuss “Dry” oxidation of steels and other supporting materials that are susceptible to oxidation under the repository conditions. We initiated these studies to observe the rate of change in sample mass as a function of temperature and time using a Thermogravimetric analysis (TGA). In addition we started sample preparation of the Swellex rock bolts, and performed oxidation studies and electromechanical tests on baseline materials, namely, alloy C-22, and YM rock bolts

Sub-surface corrosion research on rock bolt system, perforated SS sheets and steel sets for the Yucca Mountain Repository — Quarterly technical report No. 6

This report encompasses the work done for this fourth quarter of the year 2005, in accordance to cooperative agreement of University of Nevada system for the Task 019 “Subsurface Corrosion Research on Rock Bolt System, Perforated SS Sheets and Steel Sets for the Yucca Mountain Repository”, the overall objective of which is to conduct corrosion research and predict the durability of rock-bolts and other underground metallic roof supports. We have started oxidation tests using Thermogravimetric Analyzer (TGA), and Potentiodynamic tests to determine the corrosion rates of rock bolts, other support materials including bench mark materials. In this quarter, we have also performed (1) Potentiodynamic tests were performed to determine corrosion rates (CR) of Swellex rock bolts and Split Sets rock bolts. In addition, experiments have been performed on 4340 steel and Alloy 22, but the analyses are not complete; for example, hydrogen permeation tests on baseline material, Alloy 22 and Thermogravimetric Analysis (MTGA) on Swellex rock bolts under pure O2 atmosphere

Sub-surface corrosion research on rock bolt system, perforated SS sheets and steel sets for the Yucca Mountain Repository — Quarterly technical report No. 1

The principal purpose of the cooperative agreement is to develop and continue providing the public and the Office of Repository Development (ORD) of the U.S. Department of Energy’s (DOE) Office of Civilian Radioactive Waste Management (OCRWM) with an independently derived, unbiased body of scientific and engineering data concerning the study of Yucca Mountain as a potential high-level radioactive waste repository. Under this agreement, the University and Community College System of Nevada (UCCSN) will perform scientific or engineering research, and maintain and foster collaborative working relationships between government and academic researchers. The following describes the objectives of Task 019 “Subsurface Corrosion Research on Rock Bolt System, Perforated SS Sheets and Steel Sets for the Yucca Mountain Repository” under the cooperative agreement. The objective of this task is to conduct corrosion research and predict the durability of rock-bolts and other underground metallic roof supports. Corrosion resistance of rock bolts (such as Swellex, CT, and hollow core anchor) made of high-strength low alloy steel, medium carbon steel (from the YM site), stainless steel, and other higher strength materials will be evaluated. In addition, investigators will examine underground tunnel roof support materials such as perforated stainless steel sheets, I Beams, and associated materials. The proposed research for this project is divided into eight different subtasks given as follows: Subtask 1: Selection of New High Strength Steels, Stainless Steels for Rock Bolts, Steel Sets and Perforated Roof Supports Subtask 2: Electrochemical Corrosion Tests Subtask 3: Electrochemical Impedance Spectroscopy (EIS) Subtask 4: Environmentally Assisted Corrosion Tests Subtask 5: Hydrogen Permeation Studies Subtask 6: Immersion Corrosion Tests Subtask 7: Dry Oxidation Tests ASTM G-54 Subtask 8: Microstructure and Phase Characterization Studies This task is an essential part of the program to enhance the collaborative ongoing research between the UCCSN and the YMSCO during the five-year period of the cooperative agreement

Investigation of long term stability in metal hydrides

It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation

Sub-surface corrosion research on rock bolt system, perforated SS sheets and steel sets for Yucca Mountain Repository

Outline Metallurgical Issues in Underground Repository Reinforcement Support for Nuclear Materials Storage in simulated Yucca Mountain Environment used for Corrosion Issues Issues related to I-beams (Low Carbon) and Rock Bolts (Med. Carbon) Experimental Results 1. Corrosion Tests- Effect of Ionic Concentration (1x,10x,100x), Temperature, concentration and aeration/deaeration effects in YM waters (RB and I-Beam) 2. Hydrogen Permeation Tests 3. Environmentally Assisted Corrosion Tests - Stress Corrosion Cracking/Hydrogen Embrittlement in 100x YM water concentration at Room Temperature and 85oC (I-Beams

Corrosion research on rock bolts and steel sets for sub-surface reinforcement of the Yucca Mountain Repository

Underground nuclear waste storage repositories generally use steels and super alloys for various structural members and storage containers. These materials are susceptible to corrosion due to seepage of water. We studied rock bolt materials for reinforcing tunnels and containment materials for storing nuclear waste materials. In general, the design of underground support materials for tunnels are mainly based on mechanical behavior of the materials, but not much was known about the interaction of the seepage YM waters with the structural members under various conditions in the tunnels. The sources of water in the Yucca Mountain (YM) repository are due to rain fall (~5%), perched and pore waters associated with the tunnel that contain various levels of chlorides, nitrate, sulfate, silicates and bicarbonates. The temperature of the tunnel is expected to increase initially and subsequently decreases after closure of the YM repository due to nuclear waste radioactive decay. Our tests for corrosion were under 100C to obtain a wide range of data at different temperatures and electrolyte concentrations. The rock bolts are generally embedded 10 to 12 feet deep inside the host-rock of the tunnel and water seepage through the rock pores creates an interface between the bolt material and water making it conducive to aqueous corrosion. The issues related to corrosion of the rock bolts and other structural materials are: (1) variation in the temperature of the tunnel over the years, (2) concentration of the ions present in the YM waters, (3) combination of temperature and detrimental anions that cause structural damage

Hydrogen induced abrupt structural expansion at high temperatures of a Ni32Nb28Zr30Cu10 membrane for H2 purification

Ni-Nb-Zr amorphous membranes, prepared by melt-spinning, show great potential for replacing crystalline Pd-based materials in the field of hydrogen purification to an ultrapure grade (>99.999%). In this study, we investigate the temperature evolution of the structure of an amorphous ribbon with the composition Ni32Nb28Zr30Cu10 (expressed in atom %) by means of XRD and DTA measurements. An abrupt structural expansion is induced between 240 and 300 °C by hydrogenation. This structural modification deeply modifies the hydrogen sorption properties of the membrane, which indeed shows a strong reduction of the hydrogen capacity above 270 °C

Sub-surface Corrosion Research on Rock Bolt System, Perforated SS Sheets and Steel Sets for the Yucca Mountain Repository

The objective of the proposed investigation is to conduct corrosion research and predict the durability of rock-bolts and other underground metallic roof supports. In critical areas, it is possible to use highly corrosion resistant steels for rock bolts at Yucca Mountain (YM) repository, as the steel rock bolts, as well as other materials such as Bernold type shields for tunnels at YM site [1-4]. In addition, there is propensity for stress corrosion cracking as well as hydrogen induced cracking in rock bolts likely to occur in YM repository emplacement under drift conditions. As corrosion of these materials for underground support structures depends on the YM environmental constraints, loading, and temperatures, it is necessary to evaluate different materials with a wide range of corrosion rates for the rock bolts, particularly important for SCC and HE resistance which incorporate these conditions. Thus these studies will enable DOE to more accurately model for long-term predictions of drift stability during YM repository service. It is proposed that the following subtasks be performed to further this goal. The tables below describe the proposed materials for the rock bolts and steel sets as well as the types of tests important corrosion tests of significance to determine the optimal materials for use at the YM underground repository

Corrosion research on rock bolts and steel sets for sub-surface reinforcement of the Yucca Mountain repository

Corrosion resistance of Yucca Mountain (YM) carbon steel rock bolt (0.44%C) and I-beam steel sets (0.08%C) towards electrochemical/general corrosion, stress corrosion cracking (SCC), and hydrogen embrittlement (HE) susceptibility has been determined using simulated YM waters in this Task 18 for YM site underground repository tunnel support. These findings show the corrosion behavior of these structural support members with and without applied stresses in simulated YM environments. The simulated YM waters were increased in nominal concentrations from Ix to lOOx (three different levels) for electrochemical and other corrosion studies. The effect of temperature, of significance to YM repository, on the corrosion behavior are presented using electrochemical as well as electro-mechanical studies. Conventional ASTM general corrosion tests, such as (ASTM G-85 YM water spray Fog tests), ASTM G-31 (Immersion Tests), ASTM G-85 (modified YM water Spray), ASTM G-60 (Cyclic Humidity) tests were performed. Electrochemical corrosion tests include potentiodynamic tests and impedance spectroscopy, stress corrosion cracking, hydrogen cracking. In addition, effect isolation of ions such as HCO 3, SiO 2, that play critical role in affecting the corrosion rates of steels, have been determined. Microstructural and phase characterization of rock bolt and I-beam materials were performed by using scanning electron microscopy (SEM), xray photoelectron microscopy (XPS), and x-ray diffraction (XRD) analyses. In the present study, and we have measured higher corrosion rates for the (0.08%C) low carbon steel I-beam as compared to higher carbon (0.44%C) rock bolts; normally high carbon steels will undergo more corrosion than low carbon steels. It postulated that it may be due to: (a) Environmental effects due to the electrochemical reactions in this YM (electrolyte) in which dissolution as well as deposition of extrinsic ions are dynamic processes that make the corrosion process more complex, (b) Uniform distribution of carbides in rock bolts due increased Pearlite areas, as compared to the I-beams that have much smaller amounts of Pearlite. The variation of corrosion rates (CR) of rock bolts and I-beam as a function of temperature (between 25° and 85°C) is very interesting; these have been performed using de-aerated and aerated conditions showing lower and upper CR limits. A striking result is that the corrosion rate of rock bolts and I-beam increased with temperature from 25° to 45°C, thereafter there is a decrease in corrosion rate at higher temperatures for the lOOx YM waters (65° and 85°C). This CR maxima appears around 45°C for both these steels, in most cases, particularly, lOOx (nominal) YM waters. This can be explained taking into account the following competing factors: (1) temperature and ionic concentration generally increase the CR due to increased reaction rates, and on the other hand (2) dissolved oxygen effects decrease as the temperature is increased; it appears that the convergence occurs around 45°C after which the corrosion rates start to decrease. The decrease in CR at higher temperatures can be mainly attributed to the decrease in oxygen solubility and the adsorption of ionic species such as Mg and Si providing resistance to further corrosion, as determined by XPS analyses. The corrosion rates obtained for the rock bolts from polarization tests using deaerated and aerated electrolytes are plotted in Figure l(a). These plots show that in deaerated condition the corrosion rates are significantly low as compared to the oxygenated electrolytes; thus these deaerated conditions show lower corrosion limits. However, in the case of rock bolts, at Ix and lOx the corrosion rate increased with temperature up to 85°C (Figure (la)). In the case of I-beams, this trend in the decrease in corrosion rates was observed at all concentration levels [1, 10, and lOOx in Figure l(b)]. Data points, for example, CH-887 indicates cyclic humidity corrosion rates of 887 urn/year, and other general or immersion corrosion tests have been incorporated in Figures 1 (a and b) and show a reasonable agreement with the electrochemical results

A selective synthesis of taon nanoparticles and their comparative study of photoelectrochemical properties

A simplified ammonolysis method for synthesizing single phase TaON nanoparticles is presented and the resulting photoelectrochemical properties are compared and contrasted with as-synthesized Ta2O5 and Ta3N5. The protocol for partial nitridation of Ta2O5 (synthesis of TaON) offers a straightforward simplification over existing methods. Moreover, the present protocol offers extreme reproducibility and enhanced chemical safety. The morphological characterization of the as-synthesized photocatalysts indicate spherical nanoparticles with sizes 30, 40, and 30 nm Ta2O5, TaON, and Ta3N5 with the absorbance onset at ~320 nm, 580 nm, and 630 nm respectively. The photoactivity of the catalysts has been examined for the degradation of a representative cationic dye methylene blue (MB) using xenon light. Subsequent nitridation of Ta2O5 yields significant increment in the conversion (ζ: Ta2O5 95% ζ for a lower (0.1 g) loading and with a lamp with lower Ultraviolet (UV) content. Improved Photoelectrochemical performance is noted after a series of chronoamperometry (J/t), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) measurements. Finally, stability experiments performed using recovered and treated photocatalyst show no loss of photoactivity, suggesting the photocatalysts can be successfully recycled