Stephen E. Cumblidge

Preliminary Assessment of NDE Methods on Inspection of HDPE Butt Fusion Piping Joints for Lack of Fusion

Studies at the Pacific Northwest National Laboratory in Richland, Washington, are being conducted to evaluate nondestructive examination approaches for inspecting butt fusion joints in high density polyethylene (HDPE) pipe for lack of fusion (LOF). The work provides information to the United States Nuclear Regulatory Commission on the effectiveness and need for volumetric inspection techniques of HDPE butt fusion joints in Section III, Division 1, Class 3, buried piping systems in nuclear power plants. This paper describes results from preliminary assessments using ultrasonic nondestructive techniques and high-speed tensile impact testing for determining joint integrity. A series of butt joints were fabricated in 3408, 12-inch IPS DR-11 material by varying the fusion parameters in attempts to provide good joints and joints containing LOF. These butt joints were visually examined and volumetrically examined with time-of-flight diffraction (TOFD) and phased-array (PA) ultrasound. A limited subset of pipe joint material was destructively analyzed by either slicing through the joint and visually examining the surface or by employing a standard high-speed tensile impact test. Initial correlation of the fusion parameters, nondestructive, and destructive evaluations have shown that areas with gross LOF were detected with both TOFD and PA ultrasound and that the tensile impact test showed a brittle failure at the joint. There is still some ambiguity in results from the less obvious LOF conditions. Current work is targeted on assessing the sensitivity of the ultrasonic volumetric examinations and validating the results with a destructive analysis. It is expected that on-going and future work will lead to quantifying the ultrasonic responses in terms of joint integrity.Copyright

An Assessment of Visual Testing

In response to increasing interest from nuclear utilities in replacing some volumetric examinations of nuclear reactor components with remote visual testing, the Pacific Northwest National Laboratory has examined the capabilities of remote visual testing for the Nuclear Regulatory Commission. This report describes visual testing and explores the visual acuities of the camera systems used to examine nuclear reactor components. The types and sizes of cracks typically found in nuclear reactor components are reviewed. The current standards in visual testing are examined critically, and several suggestions for improving these standards are proposed. Also proposed for future work is a round robin test to determine the effectiveness of visual tests and experimental studies to determine the values for magnification and resolution needed to reliably image very tight cracks.

New international Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT)

The Nuclear Regulatory Commission established the Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT) to follow on from the successful Program for the Inspection of Nickel alloy Components. The goals of PARENT are to conduct a confirmatory assessment of the reliability of nondestructive evaluation (NDE) techniques for detecting and sizing primary water stress corrosion cracks and apply the lessons learned from PINC to a series of round-robin tests. These open and blind round-robin tests will comprise a new set of typical pressure boundary components including dissimilar metal welds and bottom-mounted instrumentation penetrations. Open round-robin tests will engage research and industry teams worldwide to investigate and demonstrate the reliability of emerging NDE techniques to detect and size flaws with a wide range of lengths, depths, orientations, and locations. Blind round-robin tests will utilize various testing organizations, whose inspectors and procedures are certified ...

Analysis of Emerging NDE Techniques: Methods for Evaluating and Implementing Continuous Online Monitoring

There are approximately 440 operating reactors in the global nuclear power plant (NPP) fleet with an average age greater than 20 years and original design lives of 30 or 40 years. The United States is currently implementing license extensions of 20 years on many plants, and consideration is now being given to the concept of “life-beyond-60”, license extension from 60 to 80 years and potentially longer. In almost all countries with NPPs, authorities are looking at some form of license renewal program. In support of NPP license renewal over the past decade, various national and international programs have been initiated. One of the goals of the program for the proactive management of materials degradation (PMMD) is to manage proactively the in-service degradation of metallic components in aging NPPs. As some forms of degradation, such as stress corrosion cracking, are characterized by a long initiation time followed by a rapid growth phase, new inspection or monitoring technologies may be required. New nondestructive evaluation (NDE) techniques that may be needed include techniques to find stress corrosion cracking (SCC) precursors, on-line monitoring techniques to detect cracks as they initiate and grow, as well as advances in NDE technologies. This paper reports on the first part of the development of a methodology to determine the effectiveness of these emerging NDE techniques for managing metallic degradation. This methodology will draw from experience derived from evaluating techniques that have “emerged” in the past. The methodology will follow five stages: a definition of inspection parameters, a technical evaluation, laboratory testing, round robin testing, and the design of a performance demonstration program. This methodology will document the path taken for previous techniques and set a standardized course for future NDE techniques. This paper then applies the expert review section of the methodology to the acoustic emission technique to evaluate the use of acoustic emission in performing continuous online monitoring of reactor components.Copyright

Acoustic emission and guided wave monitoring of fatigue crack growth on a full pipe specimen

Continuous on-line monitoring of active and passive systems, structures and components in nuclear power plants will be critical to extending the lifetimes of nuclear power plants in the US beyond 60 years. Acoustic emission and guided ultrasonic waves are two tools for continuously monitoring passive systems, structures and components within nuclear power plants and are the focus of this study. These tools are used to monitor fatigue damage induced in a SA 312 TP304 stainless steel pipe specimen. The results of acoustic emission monitoring indicate that crack propagation signals were not directly detected. However, acoustic emission monitoring revealed crack formation prior to visual confirmation through the detection of signals caused by crack closure friction. The results of guided ultrasonic wave monitoring indicate that this technology is sensitive to the presence and size of cracks. The sensitivity and complexity of guided ultrasonic wave (GUW) signals is observed to vary with respect to signal frequency and path traveled by the GUW relative to the crack orientation.

AGING MANAGEMENT USING PROACTIVE MANAGEMENT OF MATERIALS DEGRADATION

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to lay the technical foundations for defining proactive actions to manage degradation of materials in light water reactors. The current focus is existing plants; however, if applied to new construction, there is potential to better monitor and manage plants throughout their life cycle. This paper discusses the NRC’s Proactive Management of Materials Degradation program and its application to nuclear power plant structures, systems, and components.

The Capabilities and Limitations of Remote Visual Methods to Detect Service-Induced Cracks in Reactor Components

Since 1977, the U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research has funded a multiyear program at the Pacific Northwest National Laboratory (PNNL) to evaluate the reliability and accuracy of nondestructive evaluation (NDE) techniques employed for inservice inspection (ISI). Recently, the U.S. nuclear industry proposed replacing current volumetric and/or surface examinations of certain components in commercial nuclear power plants, as required by the ASME Boiler and Pressure Vessel Code Section XI, with a simpler visual testing (VT) method. The advantages of VT are that these tests generally involve much less radiation exposure and examination times than do volumetric examinations such as ultrasonic testing (UT). However, for industry to justify supplanting volumetric methods with VT, an analysis of pertinent issues is needed to support the reliability of VT in determining the structural integrity of reactor components. As piping and pressure vessel components in a nuclear power station are generally underwater and in high radiation fields, they need to be examined by VT from a distance with radiation-hardened video systems. Remote visual testing has been used by nuclear utilities to find cracks in pressure vessel cladding in pressurized water reactors, core shrouds in boiling water reactors, and to investigate leaks in piping and reactor components. These visual tests are performed using a wide variety of procedures and equipment. The techniques for remote visual testing use submersible closed-circuit video cameras to examine reactor components and welds. PNNL has conducted a parametric study that examines the important variables that affect the effectiveness of a remote visual test. Tested variables include lighting techniques, camera resolution, camera movement, and magnification. PNNL has also conducted a laboratory test using a commercial visual testing camera system to experimentally determine the ability of the camera system to detect cracks of various widths under ideal conditions.Copyright

Effect of Gadolinium Doping on the Air Oxidation of Uranium Dioxide

Researchers at the Pacific Northwest National Laboratory (PNNL) investigated the effects of gadolinia concentration on the air oxidization of gadolinia-doped uranium dioxide using thermogravimetry and differential scanning calorimetry to determine if such doping could improve uranium dioxides stability as a nuclear fuel during potential accident scenarios in a nuclear reactor or during long-term disposal. We undertook this study to determine whether the resistance of the uranium dioxide to oxidation to the orthorhombic U3O8 with its attendant crystal expansion could be prevented by addition of gadolinia. Our studies found that gadolinium has little effect on the thermal initiation of the first step of the reported two-step air oxidation of UO2; however, increasing gadolinia content does stabilize the initial tetragonal or cubic product allowing significant oxidation before the second expansive step to U3O8 begins.

Overview of the program to assess the reliability of emerging nondestructive techniques open testing and study of flaw type effect on NDE response

In February 2012, the U.S. Nuclear Regulatory Commission (NRC) executed agreements with VTT Technical Research Centre of Finland, Nuclear Regulatory Authority of Japan (NRA, former JNES), Korea Institute of Nuclear Safety (KINS), Swedish Radiation Safety Authority (SSM), and Swiss Federal Nuclear Safety Inspectorate (ENSI) to establish the Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT). The goal of PARENT is to investigate the effectiveness of current emerging and perspective novel nondestructive examination procedures and techniques to find flaws in nickel-alloy welds and base materials. This is done by conducting a series of open and blind international round-robin tests on a set of large-bore dissimilar metal welds (LBDMW), small-bore dissimilar metal welds (SBDMW), and bottom-mounted instrumentation (BMI) penetration weld test blocks. The purpose of blind testing is to study the reliability of more established techniques and included only qualified teams and procedure...

Program for the Inspection of Nickel Alloy Components Report from the Program’s Steering Committee: Inspection of Bottom-Mounted Instrumentation Nozzles Round Robin

The U.S. Nuclear Regulatory Commission (NRC) executed agreements with organizations in Japan, Sweden, South Korea, Finland, and the United States to establish the Program for the Inspection of Nickel Alloy Components (PINC).