303 research outputs found
Frequency domain reflectometry NDE for aging cables in nuclear power plants
No full textDegradation of the cable jacket, electrical insulation, and other cable components of installed cables within nuclear power plants (NPPs) is known to occur as a function of age, temperature, radiation, and other environmental factors. System tests verify cable function under normal loads; however, demonstration of some cable’s ability to perform under exceptional loads associated with design-basis events is essential to assuring plant integrity. The cable’s ability to perform safely over the initial 40-year planned and licensed life has generally been demonstrated and there have been very few age-related cable failures.With greater than 1000 km of power, control, instrumentation, and other cables typically found in an NPP, replacing all the cables would be a severe cost burden. Justification for life extension to 60 and 80 years requires a cable aging management program to justify cable performance under normal operation as well as accident conditions. A variety of tests are available to assess various aspects of electrical and mechanical cable performance, but none of these tests are suitable for all cable configurations nor does any single test confirm all features of interest. One particularly powerful test that is beginning to be used more and more by utilities is frequency domain reflectometry (FDR). FDR is a nondestructive electrical inspection technique used to detect and localize faults in power and communication system conductors along the length of a cable from a single connection point. For the measurement, two conductors in the cable system are treated as a transmission line, which propagates a low-voltage swept-frequency waveform to interrogate the cable length. Note that because the applied signal is low-voltage (<5 volts), the test is completely nondestructive and poses no special safety concerns to operators. An inverse Fourier transform is used to convert the resulting frequency-domain data into a time-domain format, which can determine the physical location of signal reflections if the signal propagation velocity is known. FDR detects discontinuities in the electrical impedance that arise due to cable splices or similar changes along the path of the conductor pair. In addition, FDR has the potential to provide sensitivity to insulation degradation by detecting small changes in capacitance between the cable conductors being examined. Example changes that impact the insulation capacitance include exposure to heat, radiation, water damage, corrosion, or mechanical fatigue. The technique is also sensitive to cable bends, the particular lay of the cable in tray, proximity to other cable, and other factors that bear consideration when interpreting these tests. This paper examines various influences on the FDR approach and compares results of three different instruments capable of producing the FDR to assess accelerated aging cable damage among several NPP representative cables.</p
Frequency domain reflectometry modeling for nondestructive evaluation of nuclear power plant cables
No full textPower Above Gender: How Lady Macbeth Shapes Perceptions of Political Power
No full textArgumentative essay that addresses the tension between gender and power in Shakespeare's Macbeth.AgoraCopyright held by authors.GenderMacbethShakespeareAgora 202
Sediment mixing at Nonda Rock: investigations of stratigraphic integrity at an early archaeological site in northern Australia and implications for the human colonisation of the continent
No full textAbstractArchaeological excavations in sediments dating to between 60 000 and 40 000 years ago are rare in Australia. Yet this is precisely the period in which most archaeologists consider that Aboriginal people arrived on the continent. In the few cases where such early sites have been investigated, questions have invariably been raised as to the reliability of stratigraphic associations between cultural items and the surrounding sediments. This paper describes a method for examining sediment mixing in a stratigraphic sequence using the optically stimulated luminescence (OSL) signals from individual sand‐sized grains of quartz. We apply this method to the archaeological site of Nonda Rock (north Queensland), in combination with radiocarbon dating of charcoal fragments, to construct chronologies for human occupation and for the preceding, culturally sterile, deposits. Our age estimates have implications for the timing of first human arrival in Australia. Copyright © 2007 John Wiley & Sons, Ltd.Bruno David, Richard G. Roberts, John Magee, Jerome Mialanes, Chris Turney, Michael Bird, Chris White, L. Keith Fifield, John Tibb
Inter-digital capacitive sensor for evaluating cable jacket and insulation aging
No full textAn inter-digital capacitive (TDC) sensor has previously been used to measure dielectric properties of cable insulation polymer material when placed in direct contact with the insulation. Often cable insulation is covered by a polymer jacket. The dielectric properties of many cable jacket and insulation polymers are known to change due to thermal and radiation exposure-related damage. These dielectric properties frequently track with other measures of cable aging, such as tensile elongation-at-break and indenter modulus that have been broadly established as cable insulation polymer assessment methods. The external jacket of a cable is likely to have a different permittivity from the underlying insulation, and frequently the jacket material exhibits more severe damage than the insulation material due to environmental exposure. Because the jacket serves primarily to guard the cable during installation, as long as the underlying insulation condition is acceptable, the jacket condition is relatively unimportant in service.
As part of a continuing program to develop and evaluate nondestructive examination methods that may be applied to cable condition assessment, a set of tools has been developed including (1) a parallel-plate sensor to directly measure the permittivity spectrum of flat sheet material and (2) an TDC and fixture to measure the effect of cable polymer dielectric property change on the sensor response. The TDC consists of two fork-like electrodes facing each other with the fork tines interspersed and separated by a small gap. The electrodes are printed on one side of a flexible substrate that can be conformed to the surface of a cylindrical cable, with tines parallel to the cable axis. The electrodes are connected to a broad-frequency-spectral impedance meter that senses the capacitance between the narrowly gapped electrode tines. This capacitance is known to vary as a function of the permittivity of any material in close proximity to the electrodes. By finite element modeling (FEM) and experimentation, this study investigates the effect of tine spacing and other design parameters associated with the TDC on the voltage (potential) distribution and electric field depth of penetration. The TDC measurement of an unshielded ethylene-propylene rubber (EPR)-insulated cable is shown to track with the degree of aging and quantities obtained by established methods. For jacketed cable systems, the TDC response is dominated by the jacket but, by analyzing measurements from TDC sensors with different depths-of-field penetration into the cable under test, the influence of the chlorinated polyethylene (CPE) cable jacket material degradation can be separated from an assessment of the cable insulation thereby enabling assessment of the insulation beneath/through the jacket.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Glass, S. W., L. S. Fifield, A. Sriraman, W. C. Palmer, and N. Bowler. "Inter-digital capacitive sensor for evaluating cable jacket and insulation aging." AIP Conference Proceedings 2102, no. 1 (2019): 020024, and may be found at DOI: 10.1063/1.5099728. Posted with permission.</p
Interdigital Capacitance Local Non-Destructive Examination of Nuclear Power Plant Cable for Aging Management Programs
No full textThis Pacific Northwest National Laboratory milestone report describes progress to date on the investigation of non-destructive test methods focusing on local cable insulation and jacket testing using an interdigital capacitance (IDC) approach. Earlier studies have assessed a number of non-destructive examination (NDE) methods for bulk, distributed, and local cable tests. A typical test strategy is to perform bulk assessments of the cable response using dielectric spectroscopy, Tan , or partial discharge followed by distributed tests like time domain reflectometry or frequency domain reflectometry to identify the most likely defect location followed by a local test that can include visual inspection, indenter modulus tests, or Fourier Transform Infrared Spectroscopy (FTIR) or Near Infrared Spectroscopy FTIR (FTNIR). If a cable is covered with an overlaying jacket, the jacket’s condition is likely to be more severely degraded than the underlying insulation. None of the above local test approaches can be used to evaluate insulation beneath a cable jacket. Since the jacket’s function is neither structural nor electrical, a degraded jacket may not have any significance regarding the cable’s performance or suitability for service. IDC measurements offer a promising alternative or complement to these local test approaches including the possibility to test insulation beneath an overlaying jacket.This report is published as Glass, Samuel W., Fifield, Leonard S., Bowler, Nicola, Sriraman, Aishwarya, and Palmer, William C. Interdigital Capacitance Local Non-Destructive Examination of Nuclear Power Plant Cable for Aging Management Programs. PNNL-27546. United States: N. p., 2018. DOI: 10.2172/1440630. Posted with permission.</p
Actinides AMS at CIRCE and 236U and Pu measurements of structural and environmental samples from in and around a mothballed nuclear power plant
No full textAccelerator mass spectrometry (AMS) is presently the most sensitive technique for the measurement of
long-lived actinides, e.g. 236U and 239Pu. A new actinide line is in operation at the Center for Isotopic
Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy. Using the actinide line a uranium
mass sensitivity of around 4 lg has been reached measuring with a 16-strip silicon detector, and a
239Pu background level of below 0.1 fg has been obtained.
In this work we also discuss preliminary results for environmental and structural samples from in and
around the Garigliano nuclear power plant (GNPP), presently in the decommissioning phase. Measurements
on environmental samples from the vicinity of the plant allow the assessment of contamination,
if any, over the years. Measurements of structural samples from the plant are relevant to the optimization
of the decommissioning program for the GNPP
Remodeling of the lymphatic vasculature during mouse mammary gland morphogenesis is mediated via epithelial-derived lymphangiogenic stimuli
No full textLink to a related website: http://ajp.amjpathol.org/article/S0002944012006773/pdf, Open Access via UnpaywallDespite the key roles of lymphatic vessels in homeostasis and disease, the cellular sources of signals that direct lymphatic vascular growth and patterning remain unknown. Using high-resolution imaging in two and three dimensions, we demonstrated that postnatal mouse mammary gland lymphatic vessels share an intimate spatial association with epithelial ducts and large blood vessels. We further demonstrated that the lymphatic vasculature is remodeled together with the mammary epithelial tree and blood vasculature during postnatal mouse mammary gland morphogenesis. Neither estrogen receptor α nor progesterone receptor were detected in lymphatic endothelial cells in the mouse mammary gland, suggesting that mammary gland lymphangiogenesis is not likely regulated directly by these steroid hormones. Epithelial cells, especially myoepithelial cells, were determined to be a rich source of prolymphangiogenic stimuli including VEGF-C and VEGF-D with temporally regulated expression levels during mammary gland morphogenesis. Blockade of VEGFR-3 signaling using a small-molecule inhibitor inhibited the proliferation of primary lymphatic endothelial cells promoted by mammary gland conditioned medium, suggesting that lymphangiogenesis in the mammary gland is likely driven by myoepithelial-derived VEGF-C and/or VEGF-D. These findings provide new insight into the architecture of the lymphatic vasculature in the mouse mammary gland and, by uncovering the proximity of lymphatic vessels to the epithelial tree, suggest a potential mechanism by which metastatic tumor cells access the lymphatic vasculature.Kelly L. Betterman, Sophie Paquet-Fifield, Marie-Liesse Asselin-Labat, Jane E. Visvader, Lisa M. Butler, Steven A. Stacker, Marc G. Achen, and Natasha L. Harve
Actinides AMS at CIRCE and 236U and Pu measurements of structural and environmental samples from in and around a mothballed nuclear power plant
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