Techniques for intergranular crack formation and assessment in alloy 600 base and alloy 182 weld metals

Background: A technique developed to produce artificial intergranular stress corrosion cracks in structural components was applied to thick, forged alloy 600 base and alloy 182 weld metals for use in the qualification of nondestructive examination techniques for welded components in nuclear power plants. Methods: An externally controlled procedure was demonstrated to produce intergranular stress corrosion cracks that are comparable to service-induced cracks in both the base and weld metals. During the process of crack generation, an online direct current potential drop method using array probes was used to measure and monitor the sizes and shapes of the cracks. Results: A microstructural characterization of the produced cracks revealed realistic conformation of the crack faces unlike those in machined notches produced by an electrodischarge machine or simple fatigue loading using a universal testing machine. Conclusion: A comparison with a destructive metallographic examination showed that the characteristics, orientations, and sizes of the intergranular cracks produced in this study are highly reproducible. ??? 2015, Published by Elsevier Korea LLC on behalf of Korean Nuclear Societyclose0

Calculation of the proportion of reactive waste for hydrogen ignition scenario

This study was conducted as outlined in NHC Letter of Instruction 9751330 dated February 247 1997 and entitled {open_quotes}Analysis by Pacific Northwest National Laboratory to Support a Safety Assessment for Rotary Mode Core Sampling in Flammable Gas Watchlist Tanks{close_quotes}. As prescribed in this letter, the results of this study were provided to Los Alamos National Laboratory (LANL) to revise the safety assessment document. Sampling Hanford tanks with a rotary drill could result in a drill-bit overheating accident which could ignite flammable gases present in the tanks. According to calculations, an over-heated drill bit could not get hot enough to ignite the hydrogen directly. However, an overheated drill bit could ignite saltcake waste containing high concentrations of organics, and a local organics burn would achieve sufficient temperature to ignite flammable gas present in the waste. This report estimates one quantity required to evaluate this particular accident scenario; the fraction of reactive waste in the tank waste. Reactive waste is waste that contains sufficient organic carbon and a low enough moisture content to ignite when in contact with an over-heated drill bit. This report presents a methodology to calculate the proportion of reactive waste for the 100 series tanks, using sampling data from tank characterization studies. The tanks are ranked according to their reactive waste proportions, and confidence limits are assigned to the estimates

Origin of Spurious Ultrasonic Echoes in Stainless Steel Piping with Weld Overlay

The initiation and growth of intergranular stress-corrosion cracking (IGSCC) in the heat-affected zone of welds in stainless steel reactor piping has been a subject of concern to electric utilities for over ten years. This type of crack can be detected with ultrasonic shear waves during normal maintenance periods with a reliability of up to 80% [1]. Often, when crack indications have been found, the utility has been allowed to apply a weld metal overlay as a temporary repair measure. However, the complex, elastically anisotropic microstructure of the overlay considerably reduces the reliability of subsequent ultrasonic inspections. This paper addresses the problems arising because of the overlay

In-tank photo analysis

This report documents an analysis performed by Pacific Northwest Laboratory (PNL) of photographs showing the interior of a single shell tank (SST) at the Hanford site. This report shows that in-tank photos can be used to create a plan-view map of the waste surface inside a tank, and that measuring the elevation of the waste surface from the photos is possible, but not accurate enough to be useful at this time. In-tank photos were acquired for Tanks BX111 and T111. The BX111 photos were used to create the waste surface map and to measure the waste surface elevation. T111 photos were used to measure the waste surface elevation. Uncertainty analyses of the mapping and surface elevation are included to show the accuracy of the calculations for both methods

Hydrothermal monitoring in Yellowstone National Park using airborne thermal infrared remote sensing

This paper describes the image acquisition and processing methodology, including surface emissivity and atmospheric corrections, for generating surface temperatures of two active hydrothermal systems in Yellowstone National Park. Airborne thermal infrared (8–12 μm) images were obtained annually from 2007 to 2012 using a FLIR SC640 thermal infrared camera system. Thermal infrared image acquisitions occurred under clear-sky conditions after sunset to meet the objective of providing high-spatial resolution, georectified imagery for hydrothermal monitoring. Comparisons of corrected radiative temperature maps with measured ground and water kinetic temperatures at flight times provided an assessment of temperature accuracy. A repeatable, time-sequence of images for Hot Spring Basin (2007–2012) and Norris Geyser Basin (2008–2012) documented fracture-related changes in temperature and fluid flow for both hydrothermal systems, highlighting the utility of methods for synoptic monitoring of Yellowstone National Park\u27s hydrothermal systems

Calculation of combustible waste fraction (CWF) estimates used in organics safety issue screening

This report describes how in-tank measurements of moisture (H{sub 2}O) and total organic carbon (TOC) are used to calculate combustible waste fractions (CWF) for 138 of the 149 Hanford single shell tanks. The combustible waste fraction of a tank is defined as that proportion of waste that is capable of burning when exposed to an ignition source. These CWF estimates are used to screen tanks for the organics complexant safety issue. Tanks with a suitably low fraction of combustible waste are classified as safe. The calculations in this report determine the combustible waste fractions in tanks under two different moisture conditions: under current moisture conditions, and after complete dry out. The first fraction is called the wet combustible waste fraction (wet CWF) and the second is called the dry combustible waste fraction (dry CWF). These two fractions are used to screen tanks into three categories: if the wet CWF is too high (above 5%), the tank is categorized as unsafe; if the wet CWF is low but the dry CWF is too high (again, above 5%), the tank is categorized as conditionally safe; finally, if both the wet and dry CWF are low, the tank is categorized as safe. Section 2 describes the data that was required for these calculations. Sections 3 and 4 describe the statistical model and resulting fit for dry combustible waste fractions. Sections 5 and 6 present the statistical model used to estimate wet CWF and the resulting fit. Section 7 describes two tests that were performed on the dry combustible waste fraction ANOVA model to validate it. Finally, Section 8 presents concluding remarks. Two Appendices present results on a tank-by-tank basis

Statistical Evaluation of NDE Reliability in the Aerospace Industry

The goal of this paper is to review the statistical methods used in the aerospace industries to evaluate NDE reliability. The techniques presented are consistent with the damage tolerant design and structural maintenance philosophies of the aerospace industry. The first part of this paper establishes the evaluation criteria and discusses the history of NDE reliability evaluations. The second part describes the state-of-the-art analysis methods through examples from the retirement for cause (RFC) inspection system evaluation. The last part of the paper discusses some techniques used to rate operator performance and deal with false calls

Detection of Gaseous Plumes using Basis Vectors

Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. There are several methods currently being used to detect plumes. They can be grouped into two categories: those that use a chemical spectral library and those that don't. The approaches that use chemical libraries include physics-based least squares methods (matched filter). They are “optimal” only if the plume chemical is actually in the search library but risk missing chemicals not in the library. The methods that don't use a chemical spectral library are based on a statistical or data analytical transformation applied to the data. These include principle components, independent components, entropy, Fourier transform, and others. These methods do not explicitly take advantage of the physics of the signal formulation process and therefore don't exploit all available information in the data. This paper describes generalized least squares detection using gas spectra, presents a new detection method using basis vectors, and compares detection images resulting from applying both methods to synthetic hyperspectral data

Performance demonstration requirements for eddy current steam generator tube inspection

This paper describes the methodology used for developing performance demonstration tests for steam generator tube eddy current (ET) inspection systems. The methodology is based on statistical design principles. Implementation of a performance demonstration test based on these design principles will help to ensure that field inspection systems have a high probability of detecting and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented. Probability of detection and flaw sizing tests are described

Application of the risk-based strategy to the Hanford tank waste organic-nitrate safety issue

This report describes the results from application of the Risk-Based Decision Management Approach for Justifying Characterization of Hanford Tank Waste to the organic-nitrate safety issue in Hanford single-shell tanks (SSTs). Existing chemical and physical models were used, taking advantage of the most current (mid-1997) sampling and analysis data. The purpose of this study is to make specific recommendations for planning characterization to help ensure the safety of each SST as it relates to the organic-nitrate safety issue. An additional objective is to demonstrate the viability of the Risk-Based Strategy for addressing Hanford tank waste safety issues