Matthew S. Prowant

A method for rapid quantitative assessment of biofilms with biomolecular staining and image analysis

AbstractThe accumulation of bacteria in surface-attached biofilms can be detrimental to human health, dental hygiene, and many industrial processes. Natural biofilms are soft and often transparent, and they have heterogeneous biological composition and structure over micro- and macroscales. As a result, it is challenging to quantify the spatial distribution and overall intensity of biofilms. In this work, a new method was developed to enhance the visibility and quantification of bacterial biofilms. First, broad-spectrum biomolecular staining was used to enhance the visibility of the cells, nucleic acids, and proteins that make up biofilms. Then, an image analysis algorithm was developed to objectively and quantitatively measure biofilm accumulation from digital photographs and results were compared to independent measurements of cell density. This new method was used to quantify the growth intensity of Pseudomonas putida biofilms as they grew over time. This method is simple and fast, and can quantify biofilm growth over a large area with approximately the same precision as the more laborious cell counting method. Stained and processed images facilitate assessment of spatial heterogeneity of a biofilm across a surface. This new approach to biofilm analysis could be applied in studies of natural, industrial, and environmental biofilms. Graphical abstractA novel photographic method was developed to quantify bacterial biofilms. Broad spectrum biomolecular staining enhanced the visibility of the biofilms. Image analysis objectively and quantitatively measured biofilm accumulation from digital photographs. When compared to independent measurements of cell density the new method accurately quantified growth of Pseudomonas putida biofilms as they grew over time. The graph shows a comparison of biofilm quantification from cell density and image analysis. Error bars show standard deviation from three independent samples. Inset photographs show effect of staining

Progress towards prognostic health management of passive components in advanced small modular reactors

Sustainable nuclear power to promote energy security and to reduce greenhouse gas emissions are two key national energy priorities. The development of deployable small modular reactors (SMRs) is expected to support these objectives by developing technologies that improve the reliability, sustain safety, and improve affordability of new reactors. Advanced SMRs (AdvSMRs) refer to a specific class of SMRs and are based on modularization of advanced reactor concepts. Prognostic health management (PHM) systems can benefit both the safety and economics of deploying AdvSMRs and can play an essential role in managing the inspection and maintenance of passive components in AdvSMR systems. This paper describes progress on development of an experimental setup for testing and validation of PHM systems for AdvSMR passive components. The experimental set-up for validation of prognostic algorithms is focused on thermal creep degradation as the prototypic degradation mechanism. The test bed enables accelerated thermal creep aging of materials relevant to AdvSMRs along with multiple nondestructive evaluation (NDE) measurements for assessment of thermal creep damage. NDE techniques include eddy current, magnetic Barkhausen noise (MBN), and linear and non-linear ultrasonic measurements. Details of the test-bed design as well as initial measurements results for specimens at different levels of thermal creep damage are presented.

Experimental validation of ultrasonic NDE simulation software

Computer modeling and simulation is becoming an essential tool for transducer design and insight into ultrasonic nondestructive evaluation (UT-NDE). As the popularity of simulation tools for UT-NDE increases, it becomes important to assess their reliability to model acoustic responses from defects in operating components and provide information that is consistent with in-field inspection data. This includes information about the detectability of different defect types for a given UT probe. Recently, a cooperative program between the Electrical Power Research Institute and the U.S. Nuclear Regulatory Commission was established to validate numerical modeling software commonly used for simulating UT-NDE of nuclear power plant components. In the first phase of this cooperative, extensive experimental UT measurements were conducted on machined notches with varying depth, length, and orientation in stainless steel plates. Then, the notches were modeled in CIVA, a semi-analytical NDE simulation platform develope...

Evaluation of Gas Retention in Waste Simulants: Intermediate-Scale Column and Open-Channel-Depth Tests

Gas generation in Hanford’s radioactive waste storage tanks can lead to gas accumulation within the layer of settled solids (sludge) at the tank bottom. The gas, which may be hazardous and/or flammable, is formed principally by radiation-driven chemical reactions. Accumulation of these gases within the sludge increases the sludge-layer volume, which decreases the available tank volume for waste storage. Further, accumulation of large amounts of gas in the sludge can potentially result in a relatively rapid release of the accumulated gas if the sludge-layer density is reduced to less than that of the overlying sludge or that of the supernatant liquid. The potential for rapid release of large amounts of hazardous and/or flammable gases is a safety hazard that needs to be managed. Accordingly, a thorough understanding is needed of the circumstances that can lead to problematic gas accumulation in sludge layers. The Deep-Sludge Gas Release Event Project (DSGREP) is tasked with developing an improved understanding of these gas release events.

Ultrasonic phased array sound field mapping through large-bore coarse grained cast austenitic stainless steel (CASS) piping materials

A sound field beam mapping exercise was conducted to further understand the effects of coarse-grained microstructures found in cast austenitic stainless steel (CASS) materials on phased array ultrasonic wave propagation. Laboratory measurements were made on three CASS specimens with different microstructures; the specimens were polished and etched to reveal measurable grain sizes, shapes, and orientations. Three longitudinal, phased array probes were fixed on a specimens outside diameter with the sound field directed toward one end (face) of the pipe segment over a fixed range of angles. A point receiver was raster scanned over the surface of the specimen face generating a sound field image. A slice of CASS material was then removed from the specimen end and the beam mapping exercise repeated. The sound fields acquired were analyzed for spot size, coherency, and beam redirection. Qualitative analyses were conducted between the resulting sound fields and the microstructural characteristics of each specimen.

Ultrasonic Evaluation of Two Dissimilar Metal Weld Overlay Specimens

Two dissimilar metal weld (DMW) pipe-to-nozzle specimens were implanted with thermal fatigue cracks in the 13% to 90% through-wall depth range. The specimens were ultrasonically evaluated with phased-array probes having center frequencies of 0.8, 1.0, 1.5, and 2.0 megahertz (MHz). An Alloy 82/182 weld overlay (WOL) was applied and the specimens were ultrasonically re-evaluated for flaw detection and characterization. The Post-WOL flaw depths were approximately 10% to 56% through-wall. This study has shown the effectiveness of ultrasonic examinations of Alloy 82/182 overlaid DMW specimens. Phased-array probes with center frequency in the 0.8- to 1.0-MHz range provide a strong coherent signal but the greater ultrasonic wavelength and larger beam spot size prevent the reliable detection of small flaws. These small flaws had nominal through-wall depths of less than 15% and length in the 50-60 mm (2-2.4 in.) range. Flaws in the 19% and greater through-wall depth range were readily detected with all four probes. At the higher frequencies, the reflected signals are less coherent but still provide adequate signal for flaw detection and characterization. A single inspection at 2.0 MHz could provide adequate detection and sizing information but a supplemental inspection at 1.0 or 1.5 MHz is recommended.

Progress towards prognostic health management of passive components in advanced reactors — Model selection and evaluation

This paper presents recent progress towards developing a prognostic health management framework for passive components of advanced reactors (AR). The focus of this paper is on lifecycle prognostics for passive components using a Bayesian prognostic algorithm that provides a natural framework for incorporating different sources of variability and uncertainties inherent in the operations of AR. High-temperature creep damage, a prototypic failure mechanism in AR materials, is used as the context for this research. A Bayesian model selection approach is implemented to select the appropriate creep degradation model at any given time, using relevant sensor measurements reflecting the material degradation state. The model selection approach, based on reversible jump Markov chain Monte Carlo methods, is integrated with Bayesian particle filter-based prognostic framework. The proposed approach is evaluated using strain measurements obtained from accelerated creep testing of stainless steel specimens. Results indicate feasibility of the proposed approach in accurately identifying the creep degradation stage from the available measurements at a given time. Effect of uncertainties in material degradation model and measurement noise on the performance of the prognostic algorithm is also investigated.

Ultrasonic Evaluation and Imaging

Ultrasonic evaluation of materials for material characterization and flaw detection is as simple as manually moving a single-element probe across a specimen and looking at an oscilloscope display in real time or as complex as automatically (under computer control) scanning a phased-array probe across a specimen and collecting encoded data for immediate or off-line data analyses. The reliability of the results in the second technique is greatly increased because of a higher density of measurements per scanned area and measurements that can be more precisely related to the specimen geometry. This chapter will briefly discuss applications of the collection of spatially encoded data and focus primarily on the off-line analyses in the form of data imaging. Pacific Northwest National Laboratory (PNNL) has been involved with assessing and advancing the reliability of inservice inspections of nuclear power plant components for over 35 years. Modern ultrasonic imaging techniques such as the synthetic aperture focusing technique (SAFT ), phased-array (PA) technology, and sound field mapping have undergone considerable improvements to effectively assess and better understand material constraints.

Using Phased Array Ultrasonic Testing in Lieu of Radiography for Acceptance of Carbon Steel Plate Welds

The Pacific Northwest National Laboratory (PNNL) is conducting studies for the U.S. Nuclear Regulatory Commission (NRC) to assess the capability, effectiveness, and reliability of ultrasonic testing (UT) as a replacement method for radiographic testing (RT) for volumetric examination of nuclear power plant (NPP) components. This particular study focused on evaluating the use of UT on carbon steel plate welds. Welding fabrication flaws included a combination of planar and volumetric types, e.g., incomplete fusion, lack of penetration, cracks, porosity, and slag inclusions. The examinations were conducted using phased-array (PA) UT techniques applied primarily for detection and flaw type characterization. This paper will discuss the results of using UT in lieu of RT for detection and classification of fabrication flaws in carbon steel plate welds.

Phased Array Ultrasonic Sound Field Mapping in Cast Austenitic Stainless Steel

This study maps the phased array-generated acoustic sound fields through three types of CASS microstructure in four specimens to quantitatively assess the beam formation effectiveness in these materials.