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A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 1 8 2 7 interest, size or severity of degradation that constitutes a critical flaw, instru- ment and material noise, and human factors. Quantification of these factors is possible in cases where a significant number of inspections have been per- formed and where the population of actual flaws is known and may be com- pared to the NDE detection record. For some critical examinations, the influ- ence of human factors can be mini- mized by independent analysis where the data is subjected to multiple inde- pendent reviews. Any indication of dis- position discrepancy is subject to an additional review. This type of analysis is common in critical nuclear NDE pro- grams such as steam generator tube inspection [2] . CODES AND STANDARDS Numerous codes and standards for inspection are widely available and range from being quite specific to rath- er general in nature. Table 1 includes a few examples. Information may in- clude details on calibration standards, inspection frequency, guidance on how to perform inspections, applicability, mandatory and nonmandatory practic- es, tips on where to focus inspections to detect damage or degradation, and other aspects of inspection. NDE per- sonnel should be familiar with codes and standards related to their indus- try and consider the code and standard guidance when applicable. As a practi- cal matter, if an inspection is performed in accordance with some standard, it may be more efficient to cite the stan- dard for details of how the inspection was performed. Such a standard refer- ence may also add credibility to the ex- amination. Keep inmind that codes and standards do not address all aspects of NDE and cannot replace education, ex- perience, and the use of engineering judgment. EMERGING NDE METHODS New methods are continually be- ing introduced to improve NDE ac- curacy or reduce the cost and time associated with traditional methods. Examples of techniques emerging in the industry include: • Wave field analysis where an ultra- sound emitter generates an acoustic wave and the behavior of the wave is mapped over the part surface using scanning contact transducers, water or air immersion transducers, or laser velocimetry sensors. • Guided wave ultrasound using piezo- electric, electromagnetic acoustic transducer (EMAT), or magnetostric- tive sensors. This is a growing in- spection approach due to advance- ment of techniques for focusing, steering, temperature, and disper- sion curve compensation, and other developments leading to increased confidence in this technology. • Nonlinear ultrasound exploits nonlinear waveform distortion of the primary excitation frequency that typically manifests in a first harmonic or 2 × the primary fre- quency. Filtering for this harmonic response can enhance sensitivity to some conditions of interest includ- ing some types of medical imaging, nuclear reactor hydrogen embrittle- ment, and titanium diffusion bonds. • Various thermographic techniques taking advantage of higher reso- lution temperature discrimination and new ways to induce thermal gradients including sonic, flash heating lamps, inductively coupled eddy currents, and lasers. • Visual image processing algorithms designed to detect subtle differenc- es between a reference part image and an inspection object or be- tween images of a part taken after a time interval looking for indications of change. STEPS TO SUCCESSFUL NDE The guiding principle of any in- spection is that the NDE-specific pro- cedure must be demonstrated to be able to detect and, if required, deter- mine the size of any defects of interest. Demonstration of the efficacy of any NDE method typically follows a rigor- ous logical process whose steps include the following: 1. Define the minimum target size and overall range of flaw, defect, material characteristic anomalies, or measurement property of inter- est. Typically, this is performed in conjunction with responsible com- ponent designers who understand the component’s design stresses and fracture mechanics experts who can help assess likely failure mechanisms, stress concentration factors, expected flaw growth rates, TABLE 1 — EXAMPLES OF NDE CODES, STANDARDS AND INDUSTRY GUIDELINES Codes, standards, and guidelines Reference ASME Boiler and Pressure Vessel Code, Section XI: Rules for Inservice Inspection of Nuclear Power Plant Components 3 ASME Boiler and Pressure Vessel Code, Section V: Nondestructive Examination 4 ASME Boiler and Pressure Vessel Code, Section III: Subsection NB Class 1 Components – Rules for Construction of Nuclear Facility Components 5 API 1104, Welding of Pipelines and Related Facilities 6 ACI 349.3-02, Evaluation of Existing Nuclear Safety Related Concrete Structures 7 ACI 228, Nondestructive Test Methods for Evaluation of Concrete in Structures 8 International Atomic Energy Agency Guidebook on Nondestructive Testing of Concrete Structures 9 AC 43.13-1B, Acceptable Methods, Techniques, and Practices – Aircraft Inspection and Repair 10 MIL-HDBK-6870B, Nondestructive Inspection Program Requirements for Aircraft and Missile Materials and Parts, 2012 11