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Evaluation of advanced and current leak detection system

Description: US Nuclear Regulatory Commission Guide 1.45 recommends the use of at least three different detection methods in reactors to detect leakage. Monitoring of both sump-flow and airborne particulate radioactivity is mandatory. A third method can involve either monitoring of condensate flow rate from air coolers or monitoring of airborne gaseous radioactivity. Although the methods currently used for leak detection reflect the state of the art, other techniques may be developed and used. Since the recommendations of Regulatory Guide 1.45 are not mandatory, Licensee Event Report Compilations have been reviewed to help establish actual capabilities for leak detection. The review of reports which had previously covered the period June 1985 to August 1986, has been extended. The total number of events of significance is now 83. These reports have provided documented, sometimes detailed summaries of reactor leaks.
Date: January 1, 1987
Creator: Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Developmental techniques for ultrasonic flaw detection and characterization in stainless steel. [PWR]

Description: Flaw detection and characterization by ultrasonic methods is particularly difficult for stainless steel. This paper focuses on two specific problem areas: (a) the inspection of centrifugally cast stainless steel (CCSS) and (b) the differentiation of intergranular stress-corrosion cracking (IGSCC) from geometrical reflectors such as the weld root. To help identify optimal conditions for the ultrasonic inspection of CCSS, the effect of frequency on propagation of longitudinal and shear waves was examined in both isotropic and anisotropic samples. Good results were obtained with isotropic CCSS and 0.5-MHz angle beam shear waves. The use of beam-scattering patterns (i.e. signal amplitude vs skew angle) as a tool for discriminating IGSCC from geometrical reflectors is also discussed.
Date: April 1, 1983
Creator: Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Origin of spurious ultrasonic echoes in stainless steel piping with weld overlay

Description: The initiation and growth of intergranular stress-corrosion cracking (IGSCC) in the heat affected zone (HAZ) of stainless steel reactor piping welds 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%. Often after an inspection indicating cracks, a utility has been allowed to administer a temporary fix to a pipe which is suspected of being cracked. This fix is a weld metal overlay. The repaired pipes often have to be inspected after the overlay has been put on the pipe. The overlay with a complex, elastically anisotropic microstructure, considerably reduces the reliability of the ultrasonic inspection. This paper addresses the problems arising because of the overlay.
Date: August 1, 1986
Creator: Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Reliability of leak detection systems in LWRs

Description: In this paper, NRC guidelines for leak detection will be reviewed, current practices described, potential safety-related problems discussed, and potential improvements in leak detection technology (with emphasis on acoustic methods) evaluated.
Date: October 1, 1986
Creator: Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Characterization of acoustic emission signals generated by water flow through intergranular stress corrosion cracks

Description: A program is under way at Argonne National Laboratory (ANL) to develop an independent capability to assess the effectiveness of current and proposed techniques for acoustic leak detection (ALD) in reactor coolant systems. The program will establish whether meaningful quantitative data on flow rates and leak location can be obtained from acoustic signatures of leaks due to intergranular stress corrosion cracks (TGSCCs) and fatigue cracks, and whether these can be distinguished from other types of leaks. 5 refs., 3 figs.
Date: May 1, 1985
Creator: Claytor, T.N. & Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Ultrasonic beam distortion in transversely isotropic media

Description: The distortion of beam profiles and skewing of beam energy observed in transmission of ultrasound into a transversely isotropic medium can lead to erroneous interpretations of NDE data for materials such as columnar-grain steels and fiber-reinforced composites. In this paper, results are presentd for the numerical evaluation of the exact Fourier integral representation of transmission of an arbitrary incident field from an isotropic into a transversely isotropic half-space. The problem is fully three-dimensional, i.e., the symmetry axis of the transversely isotropic material is oriented arbitrarily relative to the half-space boundary and angles of incidence. The cases chosen for numerical study were selected from previously unexplained experimental data obtained from the study of propagation in columnar grain steels (welds), and from situations commonly encountered during the inspection of fiber-reinforced composites. Experimental results which give evidence to the numerically observed phenomena are presented. 11 refs., 4 figs.
Date: August 1, 1987
Creator: Roberts, R.A. & Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Deviation of longitudinal and shear waves in austenitic stainless steel weld metal

Description: One of the difficulties associated with the ultrasonic inspection of stainless steel weld metal is the deviation of the ultrasonic beams. This can lead to errors in determining both the location and size of reflectors. The present paper compares experimental and theoretical data related to beam steering for longitudinal and shear waves in a sample of 308 SS weld metal. Agreement between predicted and measured beam deviations is generally good. Reasons for discrepancies are discussed.
Date: January 1, 1980
Creator: Kupperman, D.S. & Reimann, K.J.
Partner: UNT Libraries Government Documents Department

Current practice and developmental efforts for leak detection in US reactor primary systems

Description: Current leak detection practices in 74 operating nuclear reactors have been reviewed. Existing leak detection systems are adequate to ensure a leak-before-break scenario in most situations, but no currently available, single method combines optimal leakage detection sensitivity, leak-locating ability, and leakage measurement accuracy. Simply tightening current leakage limits may produce an unacceptably large number of unnecessary shutdowns. The use of commercially available acoustic monitoring systems or moisture-sensitive tape may improve leak detection capability at specific sites. However, neither of these methods currently provides source discrimination (e.g., to distinguish between leaks from pipe cracks and valves) or leak-rate information (a small leak may saturate the system). A field-implementable acoustic leak detection system is being developed to address these limitations. 5 refs., 3 figs.
Date: July 1, 1985
Creator: Kupperman, D.S. & Claytor, T.N.
Partner: UNT Libraries Government Documents Department

Effects of microstructure on ultrasonic examination of stainless steel

Description: Ultrasonic inspection of cast stainless steel components or stainless steel welds is difficult, and the results obtained are hard to interpret. The present study describes the effects of stainless steel microstructure on ultrasonic test results. Welded coupons, 2.5 and 5.0 cm thick, were fabricated from Type 304 stainless steel, with Type 308 stainless steel as the weld material. Metallography of the base material shows grain sizes of 15 and 80 ..mu..m, and dendrites aligned from the top to the bottom surface in cast material. X-ray diffraction and ultrasonic velocity measurements indicate a random crystal orientation in the base material, but the cast sample had aligned dendrites. The weld material exhibits a dendritic structure with a preferred (100) direction perpendicular to the weld pass. Spectral analysis of ultrasonic broad-band signals through the base materials shows drastic attenuation of higher frequencies with increasing grain size (Rayleigh scattering). Annealing and recrystallization increases the ultrasonic attenuation and produces carbide precipitation at grain boundaries. The microstructural differences of the base metal, heat-affected zone, and weld metal affect the amplitude of ultrasonic reflections from artificial flaws in these zones. Data obtained from two samples of different grain sizes indicate that grain size has little effect when a 1-MHz transducer is used. When going from a 15 to an 80-..mu..m crystalline structure, a 5-MHz unit suffers a 30-dB attenuation in the detection of a 1.2 mm deep notch. The anisotropy of the dendritic structure in stainless steel renewed the interest in the effect of shear-wave polarization. In the (110) crystallographic orientation of stainless steel, two modes of shear waves can be generated, which have velocities differing by a factor of two. This effect may be helpful in ''tuning'' of shear waves by polarization to obtain better penetration in large grain materials such as welds.
Date: January 1, 1976
Creator: Kupperman, D. S. & Reimann, K. J.
Partner: UNT Libraries Government Documents Department

Acoustic emission from thermal-gradient cracks in UO$sub 2$

Description: A feasibility study has been conducted to evaluate the potential use of acoustic emission to monitor thermal-shock damage in direct electrical heating of UO$sub 2$ pellets. In the apparatus used for the present tests, two acoustic- emission sensors were placed on extensions of the upper and lower electrical feedthroughs. Commercially available equipment was used to accumulate acoustic- emission data. The accumulation of events displayed on a cathode-ray-tube screen indicates the total number of acoustic-emission events at a particular location within the pellet stack. These tests have indicated that acoustic emission can be used to monitor thermal-shock damage in UO$sub 2$ pellets subjected to direct- electrical heating. 8 references. (auth)
Date: January 1, 1975
Creator: Kennedy, C.R.; Kupperman, D.S. & Wrona, B.J.
Partner: UNT Libraries Government Documents Department

Acoustic leak detection and ultrasonic crack detection

Description: A program is under way to assess the effectiveness of current and proposed techniques for acoustic leak detection (ALD) in reactor coolant systems. An ALD facility has been constructed and tests have begun on five laboratory-grown cracks (three fatigue and two thermal-fatigue and two field-induced IGSCC specimens. After ultrasonic testing revealed cracks in the Georgia Power Co. HATCH-1 BWR recirculation header, the utility installed an ALD system. Data from HATCH-1 have given an indication of the background noise level at a BWR recirculation header sweepolet weld. The HATCH leak detection system was tested to determine the sensitivity and dynamic range. Other background data have been acquired at the Watts Bar Nuclear Reactor in Tennessee. An ANL waveguide system, including transducer and electronics, was installed and tested on an accumulator safety injection pipe. The possibility of using ultrasonic wave scattering patterns to discriminate between IGSCCs and geometric reflectors has been explored. Thirteen reflectors (field IGSCCs, graphite wool IGSCCs, weld roots, and slits) were examined. Work with cast stainless steel (SS) included sound velocity and attenuation in isotropic and anisotropic cast SS. Reducing anisotropy does not help reduce attenuation in large-grained material. Large artificial flaws (e.g., a 1-cm-deep notch with a 4-cm path) could not be detected in isotropic centrifugally cast SS (1 to 2-mm grains) by longitudinal or shear waves at frequencies of 1 MHz or greater, but could be detected with 0.5-MHz shear waves. 13 figures.
Date: October 1, 1983
Creator: Kupperman, D.S.; Claytor, T.N. & Groenwald, R.
Partner: UNT Libraries Government Documents Department

Modeling of eddy current probe response for steam generator tubes

Description: Sample calculations were performed with a three-dimensional (3-D) finite-element model analysis that describe the response of an eddy current (EC) probe to steam generator (SG) tubing artifacts. Such calculations could be very helpful in understanding and interpreting of EC probe response to complex tube/defect geometries associated with the inservice inspection (ISI) of steam generator (SG) tubing. The governing field equations are in terms of coupled magnetic vector and electric scalar potentials in conducting media and of total or reduced scalar potentials in nonconducting regions. To establish the validity of the model, comparisons of the theoretical and experimental responses of an absolute bobbin probe are given for two types of calibration standard defects. Preliminary results are also presented from a recent theoretical study of the effect of ligament size in axial cracks on EC indications with conventional ISI bobbin probes.
Date: December 1, 1996
Creator: Bakhtiari, S. & Kupperman, D.S.
Partner: UNT Libraries Government Documents Department

Characterization of flaws in a tube bundle mock-up for reliability studies

Description: As part of an assessment of in-service inspection of steam generator tubes, the authors will assemble a steam generator mock-up for round robin studies and use as a test bed in evaluating emerging technologies. Progress is reported on the characterization of flaws that will be part of the mock-up. Eddy current and ultrasonic techniques are being evaluated as a means to characterize the flaws in the mock-up tubes before final assembly. Twenty Inconel 600 tubes with laboratory-grown cracks, typical of those to be used in the mock-up, were provided by Pacific Northwest National Laboratory for laboratory testing. After the tubes were inspected with eddy current and ultrasonic techniques, they were destructively analyzed to establish the actual depths, lengths, and profiles of the cracks. The analysis of the results will allow the best techniques to be used for characterizing the flaws in the mock-up tubes.
Date: October 1, 1996
Creator: Kupperman, D.S. & Bakhtiari, S.
Partner: UNT Libraries Government Documents Department

Energy dependent neutron imaging

Description: A waste package consisting of a container and high-level nuclear waste is being developed for the permanent disposal of radioactive waste. Yucca Mountain, Nevada, is being studied as a potential site for the underground high-level nuclear waste repository. A major consideration for choosing Yucca Mountain is the presence of zeolite in tertiary ash-flow tuffs. The presence of zeolites could provide geological barriers to radionuclide migration. The suitability of the tuffaceous rocks at Yucca Mountain for the repository is being investigated since the properties of the environment around a waste site must be well characterized to reliably predict performance. The results of experiments at Lawrence Livermore National Laboratory (LLNL) to assess the possibility of imaging water in Nevada Test Site welded tuff samples showed that nuclear magnetic resonance imaging is not viable. This leaves neutron tomography and high-frequency electromagnetic geotomography as possibilities for the practical imaging of distribution and flow of fluids in rock, including tuff specimens. Water tracers are needed in electromagnetic tomography techniques since the contrast for detecting water in cracks of tuff is lower than in granite because of the higher porosity in tuff. The results of preliminary testing with geotomography by LLNL indicates relatively low spatial resolution. More sensitive techniques for detecting water is needed. This paper describes preliminary experiments to apply pulsed neutrons to image water in a sample of tuff. 3 refs., 3 figs.
Date: December 31, 1990
Creator: Kupperman, D.S.; Hitterman, R.L. & Rhodes, E.
Partner: UNT Libraries Government Documents Department

Examination of overlay pipe weldments removed from the Hatch-2 reactor

Description: Laboratory ultrasonic examination (UT), dye penetrant examination (PT), metallography, and sensitization measurements were performed on Type 304 stainless steel overlay pipe weldments from the Hatch-2 BWR to determine the effectiveness of UT through overlays and the effects of the overlays on crack propagation in the weldments. Little correlation was observed between the results of earlier in-service ultrasonic inspection and the results of PT and destructive examination. Considerable difficulty was encountered in correctly detecting the presence of cracks by UT in the laboratory. Blunting of the crack tip by the weld overlay was observed, but there was no evidence of tearing or throughwall extension of the crack beyond the blunted region.
Date: February 1, 1985
Creator: Park, J.Y.; Kupperman, D.S. & Shack, W.J.
Partner: UNT Libraries Government Documents Department

Application of ultrasonic waves to assess grain structure in cast stainless steel

Description: Although the ASME code requires the inspection of cast stainless steel (CSS) piping in nuclear reactors, it has not been possible to demonstrate unambiguously that current inspection techniques are adequate. Ultrasonic inspection is difficult because the microstructure of CSS can vary considerably, from elastically isotropic with equiaxed, relatively small grains to elastically anisotropic with a columnar grain structure to a combination of the two. For the near term, improvements that may increase the reliability of ultrasonic inspection include (a) the development of methods to establish the microstructure of the material (to help optimize the inspection technique), (b) the identification of calibration standards that are more representative of the material to be inspected and (c) the use of cracked CSS samples for training purposes. In this paper, the results of experiments to characterize the microstructure of CSS by use of ultrasonic waves will be discussed. Shear waves may be more effective for isotropic material, whereas longitudinal waves may be better for the anisotropic case because of beam-focusing effects. Sound velocity and beam skewing can be measured accurately enough to characterize CSS even in thick-walled reactor components. 5 refs., 6 figs., 2 tabs.
Date: April 1, 1985
Creator: Kupperman, D.S.; Reimann, K.J. & Abrego-Lopez, J.
Partner: UNT Libraries Government Documents Department

Thermal strains in titanium aluminide and nickel aluminide composites

Description: Neutron diffraction was used to measure residual thermal strains developed during postfabrication cooling in titanium aluminide and nickel aluminide intermetallic matrix composites. Silicon carbide /Ti 14Al-21Nb, tungsten and sapphire/NiAl, and sapphire and SiC-coated sapphire/NiAl{sub 25}Fe{sub 10} composites were investigated. The thermal expansion coefficient of the matrix is usually greater than that of the fibers. As such, during cooldown, compressive residual strains are generated in the fibers and tensile residual strains are generated in the matrix, parallel to the fibers. Liquid-nitrogen dipping and thermal cycling tend to reduce the fabrication-induced residual strains in silicon carbide-fiber-reinforced titanium aluminide matrix composites. However, matrix cracking can occur as a result of these processes. The axial residual strains in the matrix were lower in the nickel aluminide matrix than in the titanium aluminide matrix. As the matrix undergoes plastic deformation, residual thermal strains are related to the yield stress of the matrix.
Date: July 1, 1992
Creator: Saigal, A. & Kupperman, D. S.
Partner: UNT Libraries Government Documents Department

Acoustic emission from fuel pellets in a simulated reactor environment

Description: Thermal-shock damage of nuclear reactor fuel pellets in a simulated reactor environment has been correlated with acoustic-emission data obtained from sensors placed on extensions of the electrical feedthroughs. Ringdown counts, rms output data, and event-location data has been acquired for experiments carried out with single pellets as well as multiple pellet stacks. These tests have shown that acoustic-emission monitoring can provide information indicating the onset and the extent of cracking.
Date: January 1, 1977
Creator: Kupperman, D. S.; Kennedy, C. R. & Reimann, K. J.
Partner: UNT Libraries Government Documents Department

Evaluation of methods for leak detection in reactor primary systems and NDE of cast stainless steel

Description: Six cracks, including two field-induced IGSCC specimens and two thermal-fatigue cracks, have been installed in a laboratory acoustic leak detection facility. The IGSCC specimens produce stronger acoustic signals than the thermal-fatigue cracks at equivalent leak rates. Despite significant differences in crack geometry, the acoustic signals from the two IGSCC specimens, tested at the same leak rate, are virtually identical in the frequency range from 200 to 400 kHz. Thus, the quantitative correlations between the acoustic signals and leak rate in the 300 to 400 kHz band are very similar for the two IGSCC specimens. Also, acoustic background data have been acquired during a hot functional sensitivity of acoustic leak detection techniques. In addition, cross-correlation techniques have been successfully used in the laboratory to locate the source of an electronically simulated leak signal.
Date: January 1, 1984
Creator: Kupperman, D.S.; Claytor, T.N.; Prine, D.W. & Mathieson, T.A.
Partner: UNT Libraries Government Documents Department

Dual-energy neutron tomography of water in rock using the Argonne IPNS

Description: In dual-energy hydrogen imaging, the increase in hydrogen neutron cross-section at subthermal neutron energies is used to enhance the imaging of small amounts of hydrogen against a background of other absorbing materials by subtracting a tomographic image obtained for higher energy neutrons from that obtained for subthermal neutrons (picking energies such that the other absorbing materials have nearly the same cross-sections at both energies). This technique was used to provide dual-energy imaging of water in tuffaceous rock, with the goal being to track water flow through porous rock for site risk analysis of permanent disposal of radwaste. A feasibility experiment was conducted at the IPNS facility with coarse spatial resolution, yielding promising results.
Date: July 1, 1992
Creator: Rhodes, E.; Kupperman, D.S. & Hitterman, R.L.
Partner: UNT Libraries Government Documents Department

Acoustic Leak Detection for District Heating Systems

Description: An acoustic leak detection facility was completed and used to evaluate the capability of piezoelectric sensors, accelerometers, and capacitance microphones to detect and locate gas and water leaks in underground district heating and cooling (DHC) piping. Leak detection sensitivity and location capabilities for DHC systems were estimated from laboratory data and from data obtained from the underground DH system in Scranton, Pennsylvania, where acoustic background noise levels and acoustic signals from field-induced steam leaks were acquired. Acoustic detection of leaks with flow rates of less than 10 gpm is possible at a distance of several hundred meters, with a location accuracy of a few meters. Although steam leaks of comparable mass loss can be detected over a similar range with transducers mounted on the pipe outer wall, location accuracy of a few meters over this range may only be possible with transducers in direct contract with the steam. Intrusive sensors may also be necessary to detect and locate leaks in plastic pipe.
Date: February 1988
Creator: Kupperman, D. S. & Karvelas, D. E.
Partner: UNT Libraries Government Documents Department

Nondestructive Evaluation Techniques for Silicon Carbide Heat-Exchanger Tubes : Second Annual Report, October 1978-September 1979

Description: This report discusses the development of ultrasonic testing, acoustic microscopy, dye-enhanced radiography, holographic interferometry, and infrared scanning techniques for flaw detection in silicon carbide (SiC) heat-exchanger tubing. Both preservice and in-service testing requirements are discussed. An ultrasonic boreside probe and an acoustic microscope stage have been designed for continuous monitoring of SiC tubing. Preliminary results with these acoustic systems are presented. In addition, a novel technique for detecting small surface flaws using holographic interferometry is discussed. Fracture mechanics analysis suggests that detection of flaws on the order of 100 um is necessary to assure good reliability of ceramic heat exchangers. The acoustic and holographic techniques have been shown to be capable of detecting flaws of this size. However, the sensitivity of ultrasonic flaw detection in SiC is affected by the microstructure of the component. The practical considerations involved in the use of these techniques are discussed.
Date: November 1979
Creator: Kupperman, D. S.; Yuhas, D.; Deininger, W. & Sciammarella, Cesar A.
Partner: UNT Libraries Government Documents Department

An Ultrasonic Scanner for Stainless Steel Weld Inspections

Description: The large grain size and anisotropic nature of stainless steel weld metal make conventional ultrasonic testing very difficult. This paper evaluates a technique for minimizing the coherent noise in stainless steel weld metal. The method involves digitizing conventional A-scan traces and averaging them with a minicomputer. Results are presented for an ultrasonic scanner which interrogates a small volume of the weld metal while averaging the coherent ultrasonic noise.
Date: September 1978
Creator: Kupperman, D. S. & Reimann, K. J.
Partner: UNT Libraries Government Documents Department