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25 records · Page 2

A profile monitor for proton radiography experiments at the Los Alamos Neutron Science Center

The Proton Radiography (pRad) facility at the Los Alamos Neutron Science Center utilizes pulses of protons delivered by the 800 MeV linear accelerator to produce a series of radiographic images to study the dynamic behavior of materials under extreme conditions. Radiographs taken with an empty field of view, or beam pictures, are used to normalize transmission. However, because the center of the proton beam shifts between pulses, an in situ method for measuring beam position is required to normalize images for beam movement to perform absolute radiography. The beam profile monitor described here uses an array of scintillating fibers positioned in the beam path to produce light proportional to beam intensity across the beam cross section. This light is detected using fast photodiodes and a digital oscilloscope, providing a response time of several nanoseconds—suitable for measuring the 50-ns proton pulses used in pRad. The profile monitor achieves a measured position precision of 40 μm and an intensity precision of 0.7%, allowing for beam movement corrections to be applied to images, thereby improving data accuracy and image quality.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Dynamic fracture of glass fiber-reinforced ductile polymer matrix composites and loading rate effect

Here, the dynamic fracture of S-2 glass fiber-reinforced polymer matrix composites (FRPMCs) was investigated in this study. The matrix ductility was improved by a recently developed network topology modification technique via mixing partially reacted substructures (mPRS). The composite material was manufactured and characterized by micro-CT scanning and scanning electron microscopy (SEM). Dynamic single-edge notched bending (d-SENB) experiments were performed on the composites by using a modified split-Hopkinson pressure bar. Each specimen’s fracture process was visualized by ultrafast X-ray imaging. Such in-situ radiography enabled identifying the damage initiation below 50-micron scale and inspecting its propagation through the internal structures of opaque composites, thereby accurately quantifying the composites’ mechanical properties. Furthermore, the identical d-SENB experiments were designed and the digital image correlation (DIC) was employed to monitor the stress wave propagation on the composite specimens. The force and deflection measurements were modified and correlated to the physical damage processes. Besides, quasi-static SENB experiments were conducted to identify the loading rate effects on the composites’ fracture behaviors. The force and deflection history, bending stiffness, energy dissipation, and fracture toughness at different loading rates were quantified and compared. Finally, post-fracture analysis by micro-CT scanning and SEM provided physical observations on the variation of the fracture morphology by different loading rates.

42 ENGINEERING↗

Neutron Transmission Imaging with a Portable D-T Neutron Generator

Fast-neutron transmission imaging provides complementary information to x-ray transmission imaging. While fast neutron imaging resolution is generally below x-ray imaging, 14-MeV neutrons have an advantage over portable x-ray systems. Neutrons have higher transmission through high-Z materials due to a more uniform attenuation as a function of material atomic number Z compared to X-rays, and can therefore image low-Z materials inside high-Z materials. As a result, portable neutron transmission imaging has many applications, including inspection of concrete and welds for corrosion in vehicles, bridges, and other infrastructure, measurement of material levels in containers, and inspection of suspicious packages. Fast-neutron imaging is also more practical for field use than thermal-neutron imaging due to the size and shielding requirements typical of thermal-imaging systems compared to the availability of small 14.1 MeV D-T neutron generators. However, there are limitations in portable fast-neutron imaging systems, including limited neutron output, limited light produced by neutron scintillators, and lower resolution due to neutron source spot size and 2-3 mm scintillator thickness. In addition, digital-panel dark-noise is roughly 100x higher than neutron scintillator light, and variations in noise across the panel and in time is comparable to the imaging signal. Here we discuss recent efforts in developing a portable fast-neutron radiography system, including an improved neutron scintillator, mitigation of panel noise, and new commercial portable D-T neutron generators. We also present MCNP efforts to model neutron imaging, including scintillator resolution and the effects of neutron scattering from the object and surrounding materials.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Integrating fine root diameter and watershed mapping to characterize rhizosphere hydrology

Root morphology and soil hydraulic characteristics were integrated using watershed distance mapping to show water distribution and uptake across the plant-soil interface. Poplar (Populus deltoides, P. trichocarpa), maize (Zea mays), juniper (Juniperus virginiana), grape (Vitis rotundifolia) and maple (Acer saccharum) seedlings were grown in sand, after which root diameter and soil water dynamics were assessed via sequential neutron radiography. Three local soil regions (root-soil interface or edge, rhizosphere, bulk soil) were classified based on both radial distance from the root surface and diameter of the nearest root, from which changes in water content and distribution were characterized using digital image processing. Water content dynamics across the rhizosphere showed two different species-independent processes: a consistently elevated water content at the root-soil edge interface which increased with root diameter, and hysteresis as the rhizosphere transitioned to bulk soil (~0.5 cm from the root), independent of root diameter. Water uptake per unit root surface area declined exponentially with root diameter, independent of species. Results highlight the species-independent hydrologic characteristics of the rhizosphere and the potential for evaluating them in a local spatially connected soil context. Avenues for improved integration of soil and root characteristics are discussed.

59 BASIC BIOLOGICAL SCIENCES↗

An Analysis of Input Parameters for Film-Based Flash X-Ray Radiography

Flash X-ray radiography (flash) is a commonly used diagnostic technique in dynamic experiments. An analysis of the effects of input parameters on resulting metrics of image quality can aid the experimentalist in configuring the X-ray input parameters to produce the highest quality radiograph for a given experiment. Here, a flash X-ray test bed with HS800 film and a LANEX Medium F intensifier screen was used with an L3 450 kVp pulser and Scandiflash X-ray tube for this study. Input parameters including charge voltage, source filtering, and film-pack assembly were investigated for their impact on contrast-to-noise ratio (CNR), contrast, and contrast transfer function (CTF). Using VIDAR’s NDT Pro industrial film digitizer, scanner parameters such as optical density range, pixel spacing, scan mode, and digital bit-depth were also examined for their impact on image quality metrics. The highest CNR values were found with two LANEX intensifiers and no filtering. Charge voltage had no direct impact on CNR values. LANEX screen count and filtering resulted both in direct effects on CNR and interaction effects with each other and CNR value. Uncertainty bounds for CNR comparisons and repeatability of CTF evaluations are also discussed. Finally, the film results are compared with a previous study using other detector types, specifically Carestream INDUSTREX Flex GP, Flex HR, Flex XL Blue, and HPX-DR 3543.

dynamic radiography↗

2025 Intern Poster

The Hot Fuel Examination Facility (HFEF) at the Materials and Fuels Complex (MFC) houses the largest U.S. inert atmosphere hot cell for nuclear material research. Key features include the precision gamma scanning (PGS), Fuel Accident Condition Simulator (FACS), Neutron Radiography Reactor (NRAD), and the focus of this project, the Metallograph Loading Cell (MET Cell). The MET Cell performs tests on spent nuclear fuel, such as microhardness testing, microscopy, and neutron radiography. However, the MET Cell’s existing pressure and lighting control systems are outdated and inefficient, with inadequate documentation for system changes over time. This project aims to design a new automated control system for the MET Cell, ensuring longevity (minimum ten years), ease of troubleshooting/repair, and integration into the building monitoring system. The design process addressed challenges such as space restrictions, varied voltages within enclosures, sourcing new components, and security limitations. Compliance with NFPA 70, UL508A, MFC Physical Security, and INL Engineering standards was essential. The project involves repurposing an existing PLC to manage lighting and pressure control using digital and analog signals, simplifying wiring, and ensuring thorough documentation for future reference.

42 - ENGINEERING↗

Secure Storage: Historical Documentation of TA-08-0032, TA-11-0036, TA-22-0016, TA-22-0023, TA-22-0025, TA-22-0035, TA-37-0006, TA-37-0009, and TA-37-0020

The U.S. Department of Energy, National Nuclear Security Administration, Los Alamos Field Office (NA-LA), is pursuing the decommissioning and demolition (D&D) of facilities contaminated with high-explosives residues at the Los Alamos National Laboratory (Laboratory or LANL). This effort affects nine facilities associated with high-explosives and detonator research, development, and storage: Technical Area (TA) 8 Facility 32 (TA-08-0032), TA-11-0036, TA-22-0016, TA-22-0023, TA-22-0025, TA-22-0035, TA-37-0006, TA-37-0009, and TA-37-0020. All nine facilities proposed for D&D have been evaluated for listing in the National Register of Historic Places (NRHP) and determined eligible. NA-LA previously requested the State Historic Preservation Officer (SHPO) to concur with the NRHP-eligibility determinations of these nine properties presented in four reports: (1) TA-08-0032 was determined eligible for listing in the NRHP in the report, From Ranching to Radiography: An Assessment of Historic Buildings at Anchor West Site (TA-8), Vol. 1 (McGehee et al. 2008a). The SHPO concurred with this eligibility determination on November 26, 2008. (2) TA-11-0036 was determined eligible for listing in the NRHP in the report, ESA Division’s Five-Year Plan: Consolidation and Revitalization at Technical Areas 3, 8, 11, and 16, Vol. 1) (McGehee et al. 2003). The SHPO concurred with this eligibility assessment on June 22, 2003. (3) TA-22-0016, TA-22-0023, TA-22-0025, and TA-22-0035 were determined eligible for listing in the NRHP in the report, DX Division’s Facility Strategic Plan: Consolidation and Revitalization at Technical Areas 6, 8, 9, 14, 15, 22, 36, 39, 40, 60, and 69, Vol. 1 (McGehee et al. 2005a). The SHPO concurred with these eligibility determinations on April 18, 2006. (4) TA-37-0006, TA-37-0009, and TA-37-0020 were determined eligible for listing in the NRHP in the report, High Explosives and the Nuclear Stockpile: An Assessment of Historic Buildings at Magazine Area C (TA-37), Vol. 1 (McGehee et al. 2008b). The SHPO concurred with these eligibility determinations on April 17, 2008. In a letter dated January 24, 2020, NA-LA acknowledged that the D&D of these nine NRHP-eligible facilities was an adverse effect that requires resolution through mitigation. NA-LA proposed the use of standard mitigation practices as defined in the Programmatic Agreement (PA) among the U.S. Department of Energy, National Nuclear Security Administration, Los Alamos Field Office, the New Mexico State Historic Preservation Office, and the Advisory Council on Historic Preservation Concerning Management of the Historic Properties at Los Alamos National Laboratory, Los Alamos, New Mexico. The PA states that adverse effects to NRHP-eligible buildings and structures will be resolved according to the standard practices defined in Part II, Section 10, of the Laboratory’s Cultural Resources Management Plan, A Plan for the Management of the Cultural Heritage at Los Alamos National Laboratory, New Mexico (Purtzer et al. 2019), and Section 2.B of Appendix D of the PA itself. The standard practice documentation package includes the following components: (1) Interior and exterior photography and production of archival-quality digital photographs; (2) Documentation and curation of historically significant equipment and artifacts; (3) A list of all known drawings for the property; (4) Reduced-scale reproductions of selected drawings for the property; (5) A location map that shows the location of the property relative to the entire Laboratory property; (6) Reproduction of historical TA maps; (7) A TA map that depicts the footprint of each eligible and non-eligible facility; and (8) An expanded historic context that uses oral-history interviews, if available. On March 3, 2020, the SHPO concurred with the adverse effect determination and the mitigation plan. The documentation package, as previously described, is provided in Volumes 1 and 2 of this report.

99 GENERAL AND MISCELLANEOUS↗