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We consider the disposal of spent nuclear fuel and high-level radioactive waste in horizontal holes drilled into deep, low-permeable geologic formations using directional drilling technology. Residual decay heat emanating from these waste forms leads to temperature increases within the drillhole and the surrounding host rock. The spacing of waste canisters and the configuration of the various barrier components within the horizontal drillhole can be designed such that the maximum temperatures remain below limits that are set for each element of the engineered and natural repository system. We present design calculations that examine the thermal evolution around heat-generating waste for a wide range of material properties and disposal configurations. Moreover, we evaluate alternative layouts of a monitoring system to be part of an in situ heater test that helps determine the thermal properties of the as-built repository system. A data-worth analysis is performed to ensure that sufficient information will be collected during the heater test so that subsequent model predictions of the thermal evolution around horizontal deposition holes will reliably estimate the maximum temperatures in the drillhole. The simulations demonstrate that the proposed drillhole disposal strategy can be flexibly designed to ensure dissipation of the heat generated by decaying nuclear waste. Moreover, an in situ heater test can provide the relevant data needed to develop a reliable prediction model of repository performance under as-built conditions.

In this paper, the results of a study aimed at evaluating the strength of wide-flanged beams subjected to corrosion-induced damage, modeled using a standard finite element program (ABAQUS) is presented and discussed. Typical beams in consideration were subjected to different cases of corrosion-induced damage, such as non-uniform and varying degree of material loss that simulates pitting corrosion. Many variables, such as (a) shape of pitting damage, (b) location of pits along the length of the beam, (c) number of pits, and (d) depth of pits, were considered to facilitate a better understanding of the load carrying capacity of steel I-beams having damage quite similar to pitting damage to the web. The results are compared with an “as-new” beam for purpose of evaluation of the reduction in strength due to environment-induced deterioration. A “corrosion strength reduction factor (CSRF)” is introduced to help identify the reduction in load carrying capacity as a consequence of both height and depth of the damage due to corrosion. The results are presented in charts for purpose of practical beam design.

A fault tree methodology has been used to analyze the combinations of basic factors involved in fungal degradation and corrosion. The purpose was to demonstrate the identification of mitigation actions for reducing the risk of fungal corrosion of coated aluminum in aircraft. The interaction between fungal-induced degradation processes and coatings is described, and the methodology of the fault tree analysis (FTA) is presented. The interconnection of the basic factors through conventional AND and OR logic gates in the fault tree structure reveals vulnerabilities and potential failure pathways in the system. Mitigation actions can be directed at these basic factors to reduce or eliminate failure pathways, thereby reducing the overall risk of fungal-induced corrosion. Potential applications of FTA for corrosion mitigation, design and materials selection, and failure analysis are presented.

A new type of enamel coated dowel bars for use as concrete pavements has been recently developed and implemented. A gradual deterioration of such bars can occur due to corrosion occurring at locations of the fine microscopic cracks and other defects in the coating. The results of a study aimed at evaluating and understanding the corrosion resistance of such dowel bars is presented and comparisons made with corresponding epoxy-coated dowel bars. Identical defects were introduced onto the surface of the dowel bars with the two types of coatings. The extrinsic influence of environment and resultant corrosion based on type, location and severity of the defects was carefully examined. Test results reveal the corrosion resistance of enamel-coated dowel bars to be as good as the corrosion resistance of the corresponding epoxy-coated dowel bars. The presence of corrosion products was essentially confined to locations of the defects in the test specimens when the steel was exposed to concrete and subject to induced current to accelerate corrosion thereby demonstrating the enamel coating on the surface of the dowel bars to be effective in isolating the steel from the surrounding concrete and concurrently providing enhanced resistance to corrosion. Also, the enamel-coated dowel bars did not experience peeling of the coating at the interface. The epoxy-coated dowel bars revealed peeling of the epoxy coating from the surface that eventually got stuck to the inner surface of the surrounding concrete. This demonstrated that the enamel-coated dowel bars would perform better under prevailing service conditions in concrete pavements where relative free sliding is both essential and required.

The disposal of spent nuclear fuel and other high-level radioactive waste in deep horizontal drillholes is an innovative system. Canisters of highly corrosion-resistant nickel-chromium-molybdenum (Ni-Cr-Mo) alloys are specified for the disposal of this nuclear waste. The canisters are emplaced along a steel casing in a horizontal drillhole that is one to three kilometers deep into or below a low-permeability geologic formation. The drillhole is in fully saturated rock with anoxic and reducing pore waters. A time-interval analysis method was used to track the evolution of the environment and to analyze corrosion performance of a representative engineered barrier system (EBS) configuration. In this analysis, the canisters remained perforation-free for tens of thousands of years. The amounts of hydrogen and metal oxides formed as by-products of the metal corrosion process were determined. These by-products are of interest, because both hydrogen and metal oxides can affect the chemical composition of the environment and the transport and sorption behavior of radionuclides and other species. Beneficial attributes that contribute to the extraordinarily long life of the canisters were identified. Several inherent characteristics of the horizontal drillhole disposal system reduced the complexities and uncertainties of the analysis.

Developing predictive models for quantitative assessment of the deterioration of rock bolts exposed to corrosive environments is essential for rational planning of maintenance activities for anchorage structures. This article presents a probability-based computational model for predicting the time-dependent deterioration of bond capacity of corroding rock bolts due to the attack of chlorides. The inherent stochastic nature involved in the corrosion and degradation process is identified and simulated. A method is developed based on fundamental Mohr–Coulomb theory to evaluate the effect of corrosion on the bond strength due to a failure mode involving splitting of grout cover. Parameters affecting both strength and stress state at the bolt–grout interface are quantitatively related to the degree of corrosion. Integrating the realised corrosion stochastic process and the developed bond loss evaluation method, a computational algorithm based on Monte Carlo simulation is presented for evaluating the bond deter...

Understanding of cracking behavior of cover concrete is important for assessment of the remaining service life of corrosion-affected concrete structures. Predicting initiation of concrete cracking is commonly based on the evolution of stresses caused by the volume expansion of corrosion products on reinforcing bars. This paper presents an analytical method that is capable of providing the solution to two-dimensional (2D) elastic stress field caused by nonuniform volume expansion around the corroding reinforcing bars. The developed method features the formulation of a displacement model, which is applied as a boundary condition to simulate the effect of nonuniform corrosion on the deformation of the surrounding concrete. A closed-form solution to the stress field is obtained using the complex variable method of Muskhelishvili. Validation of the solution is supported by a comparison with finite-element-based simulation results. The solution reveals the evolution of stresses surrounding two typical locations...

The objective of this work was to develop a hydrogen storage module for onboard electrical power sources suitable for use in micro power systems and micro-electro-mechanical systems (MEMS). Hydrogen storage materials were developed as thin-film inks to be compatible with an integrated manufacturing process. Important design aspects were (a) ready activation at sub-atmospheric hydrogen pressure and room temperature and (b) durability, i.e. capable of hundreds of absorption/desorption cycles and resistance to deactivation on exposure to air. Inks with palladium-treated intermetallic hydrogen storage alloys were developed and are shown here to be compatible with a thin-film micro-fabrication process. These hydrogen storage modules absorb hydrogen readily at atmospheric pressure, and the absorption/desorption rates remained fast even after the ink was exposed to air for 47 weeks.

In this paper, the results of a study aimed at understanding the extrinsic influence of test specimen orientation, with respect to a wrought alloy-steel plate, on the stress-controlled cyclic fatigue properties and fracture behavior of a structural steel is highlighted. The alloy steel chosen was ASTM A572 grade 50. Samples of this alloy steel, prepared from both the longitudinal and transverse orientations, were cyclically deformed over a range of maximum stress and the corresponding number of cycles to failure (NF) was recorded. The influence of test specimen orientation and intrinsic microstructural effects on cyclic fatigue life and fracture behavior are presented and discussed. Overall, the macroscopic fracture mode was essentially identical regardless of orientation of the test specimen with respect to the wrought plate. The microscopic mechanisms governing cyclic deformation, fatigue life, and final fracture behavior are presented in light of the mutually interactive influences of magnitude of applied stress, intrinsic microstructural effects, orientation of test specimen, and deformation characteristics of the key microstructural constituents.

The objective of this work was to demonstrate a micro-fabricated hydrogen storage module for micro-power systems. Hydrogen storage materials were developed as thin-film inks to be compatible with an integrated manufacturing process. Performance and durability of storage modules were evaluated. Further, applications were demonstrated for a nickel-hydrogen battery and a micro-fabricated hydrogen-air PEM fuel cell. The ink making process, in which polymer binders and solvents were added to the palladium-treated alloys, slightly decreased the storage capacities, but had little effect on the activation properties of the treated alloys. After 5000 absorption/desorption cycles under hydrogen, the hydrogen storage capacities of the thin-film inks remained high. Absorption/desorption behavior of the ink was tested in the environment of a new type nickel-hydrogen battery, in which it would in contact with 26wt% KOH solution, and the ink showed no apparent degradation. Storage modules were used as the successfully as hydrogen source for PEM fuel cell.

The objective of this study is to investigate the composition of corrosion products and the metal surface within a crevice after localized corrosion. The analysis provides insight into the propagation, stifling and arrest processes for crevice corrosion and is part of a program to analyze the evolution of localized corrosion damage over long periods of time, i.e. 10,000 years and longer. The approach is to force the initiation of crevice corrosion by applying anodic polarization to a multiple crevice assembly (MCA). Results are reported here for alloy C-22, a Ni-Cr-Mo alloy, exposed to a high temperature, concentrated chloride solution. Controlled crevice corrosion tests were performed on C-22 under highly aggressive, accelerated condition, i.e. 4M NaCl, 100 C and anodic polarization to -0.15V-SCE. The crevice contacts were by either a polymer tape (PTFE) compressed by a ceramic former or by a polymer (PTFE) crevice former. Figure 1 shows the polarization current during a crevice corrosion test. After an incubation period, several initiation-stifle-arrest events were indicated. The low current at the end of the test indicated that the metal surface had repassivated.

The baccalaureate program in Corrosion Engineering at The University of Akron is the first of its kind in the nation. It was formed in response to Federal Government interest and industry need in the area. The idea was first presented in 2006 and the University welcomed its first freshman class in 2010. The degree is a traditional engineering degree based on a math, science and general education courses that support engineering science and engineering design courses; students take courses from five different engineering programs. At its core are classes and laboratories in corrosion electrochemistry, high temperature oxidation, and corrosion engineering management. In addition, the students are exposed to hands-on experience as a corrosion engineer through the co-op program. This curriculum was developed using input from a number of stakeholders in government, industry and academia that wanted students with knowledge in corrosion basics, materials characterization and corrosion prevention and the ability to diagnose failures, guide maintenance and repair as well as perform risk based assessment. In this presentation we will review the method that lead to the current program as well as feedback from co-op experiences including both student and employer perspectives.

One important factor affecting crevice corrosion of passive metals is the crevice geometry, e.g., the gap of the crevice. The crevice geometry can be affected by the properties of the materials used as the crevice formers, i.e., a polymeric crevice former can conform to the surface roughness of a metal specimen, which helps the creation of a tighter crevice gap. The objective of this work was to investigate the effects of crevice former materials on the evolution of crevice corrosion damage of Alloy 22 (UNS N06022). The factors that may limit the initiation and slow or stop the propagation of crevice corrosion are addressed. Crevice formers made from ceramic, polymers, and polytetrafluoroethylene (PTFE) tape-covered ceramic are compared in controlled crevice corrosion tests, which are performed under highly aggressive, accelerated conditions. Results show that crevice corrosion of Alloy 22 is affected by the crevice former materials and by the surface finishes of the crevice former and specimen. ...

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