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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

2020 Postclosure Groundwater Monitoring and Inspection Report, Central Nevada Test Area, Subsurface Corrective Action Unit 443

This report presents the groundwater monitoring data collected by the U.S. Department of Energy (DOE) Office of Legacy Management (LM) from the Central Nevada Test Area (CNTA), Nevada, Site, Subsurface Corrective Action Unit (CAU) 443 in Nye County, Nevada (Figure 1). The CNTA is the site of an underground nuclear test in 1968 that resulted in residual contamination near the detonation depth of 3200 feet (ft); the contamination requires long-term monitoring. Responsibility for the environmental restoration and long-term monitoring was transferred from DOE’s National Nuclear Security Administration, Nevada Field Office, to LM on October 1, 2006. The environmental restoration and site closure process were completed in 2015 in accordance with the amended 1996 Nevada Federal Facility Agreement and Consent Order (FFACO) (State of Nevada et al. 1996, as amended) and all applicable Nevada Division of Environmental Protection (NDEP) policies and regulations. The Closure Report, Central Nevada Test Area, Subsurface Corrective Action, Unit 443 (DOE 2018), also called the Closure Report, originally was completed in January 2016 and revised in October 2018; it describes LM’s plan for long-term postclosure monitoring. This includes monitoring of the radioisotopes of interest and water elevations, inspecting the site and maintaining the institutional controls (ICs), evaluating and reporting data, and documenting the site’s records and data management processes (DOE 2018).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Alternative Power and Propulsion for Space Systems

What are the main sources of power and propulsion for space systems and what are their advantages, disadvantages, how do they work, and what are the politics behind them? The following topics will be analyzed solar panels, batteries, radioisotope thermoelectric generator (RTG), advanced Stirling radioscopic generator (ASRG), reactors, nuclear thermal rockets (NTP), thermionic experiment with conversion (TOPAZ), electrothermal plasma thruster (VASIMR), ion propulsion, and finally nuclear pulse propulsion. The production of Pu-238 is extremely controversial but a vital source of fuel for many of these space systems. Soral and Batteries are the most common and the least controversial forms of power used in space systems today. However, is ineffective for deep space exploration as they only function for up to four years without needing to be recharged. This is where nuclear systems come into play. Nuclear systems such as an RTG will “live” up to 88 years. For example, Voyager 1 is powered by an RTG It has been traveling since 1977 and has left out solar system in 2012 and has yet to run out of power. However, this type of technology (nuclear) has many hurtles it needs to jump through before advancements in can go much further.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Conjugate Heat Transfer Analysis in Pressurized Helium Gas Cooling Channels

Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 from the irradiation of Mo-100 targets. The NMR target consists of an Inconel window that allows the electron beam to penetrate and irradiate a stack of Mo-100 disks. The irradiation process generates large amounts of heat and is cooled using pressurized helium gas flowing at 400 g/s. LANL provides both numerical analysis support and experimental support. Computational fluid dynamics (CFD) and conjugate heat transfer (CHT) analysis are performed on the NMR target to analyze the helium flow and volumetric heating through the NMR system. In this iteration of numerical analysis, we update the Mo-100 disk thickness to 0.74 mm and the gap between the Inconel window and the first disk to 0.69 mm. Estimates of the heat flux from the electron beams from Monte Carlo N-Particle code (MCNP) analysis were combined with CFD to perform the CHT analysis. The pressure drop through the targets, force applied on the first disk, beam window and target disk temperatures are some of the quantities estimated using the simulations. The pressure drop through the target was estimated as 0.198 MPa, while the force due to venturi effects across the first disk was estimated to be 100 N. The results show maximum window temperatures over 600 °C and peak disk temperatures over 1600 °C. Past work has shown that beyond 650-700 °C, the Inconel window becomes susceptible to yield and rupture. The increased temperature in these results reduces the margin of error possible on beam spot size. The disk temperatures showed a sinusoidal distribution with the 6 th – 8 th disk from each window exhibiting highest disk temperatures. The peak temperature of the stainless steel housing was close to 316 °C and that of the laminations and spacers was approximately 582 °C.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Window Cooling Studies using Pulsed Beam Heating

Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 through the irradiation of Mo-100 using electron accelerators. Two electron accelerators are used to irradiate a double sided target. LANL collaborates with NMR to experimentally investigate beam effects on the target which consists of two Inconel 718 windows on either side of a stack of Mo-100 disks. LANL simulates the beam heating using an induction heater.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Flow Induced Vibration Studies in Pressurized Helium Gas Cooling Channels

Production of metastable Technetium-99 (Tc-99m), a radioactive tracer that emits gamma rays, is vital to the medical imaging community. Tc-99m is extracted from the decay of Molybdenum-99 (Mo-99) which has a half-life of about 2-3 days. The work presented in this report is part of the NNSA’s mission to produce Mo-99 commercially, within the US, without the use of highly enriched uranium (HEU) in support of nonproliferation and global security. Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 through the irradiation of Mo-100 targets using an electron beam. The NMR target comprises a stack of approximately 60-70 Mo-100 disks with diameter 24 mm and thickness 0.74 mm held in stainless steel laminations, each separated using 0.25 mm thick stainless steel spacers. The symmetric target stack is housed in an Inconel vessel with two Inconel windows on either side. Two electron accelerators are used to produce 40 MeV, 3.16 µA electron beams each that penetrate the Inconel windows and irradiate the Mo-100 disks. Approximately 90% of the total 250 kW beam power is deposited in the NMR target during the irradiation process. During irradiation, pressurized helium gas flows through 0.25 mm thin gaps between the disks cooling the beam window, target disks, disk laminations and spacers. Both NMR and LANL have found during cold testing of the target system (no heat deposition) that the Mo-100 disks undergo significant mass loss and disk breakage due to vibrations induced by the flowing helium gas. The mass loss is not only undesirable due to monetary loss from reduced final quantities of Mo-99, but also due to the hazards associated with radioactive material trapped in the cooling lines and particle filters. The effect of flow rate and target geometry on the flow induced vibrations need to be quantified, and recommendations provided to minimize this mass loss. This work describes LANL’s experimental characterization of the flow induced vibrations and disk mass loss in a reduced scale set-up containing 10 Mo-100 disks. We use high speed imaging, displacement measurements and microphone measurements combined with signal processing to estimate the vibration frequency of each disk. The effect of disk thickness, target fit and duration of testing on the mass loss is described. We find that in the current configuration of NMR targets, the vibrations and mass loss on the first disk are minimized, while those in the adjacent disks are highest. The microphone and high-speed image data show that increased flow rates and increased duration of testing increases vibration frequency and mass loss. The mass loss is due to both disk rotation and back and forth motion. There are visible wear marks on the disks with the highest mass loss. We also note that the current NMR window gap reduces flow induced vibrations compared to the previous smaller gaps. Longer duration testing will provide more data and verification for the findings presented in this report. The work will be continued in FY 24.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Comparison of Supervised and Un-Supervised Machine Learning Algorithms for Threat Detection and Scintillator Performance for Radiation Portal Monitoring

Following the events of September 11, 2001, international border crossing have been equipped with radiation portal monitors (RPMs) to identify illicit radioactive material. Polyvinyl toluene (PVT) scintillators are commonly used due to their low cost and reasonable maintainability, however they offer low spectral resolution. Despite the fact that over twenty years has transpired since this event, radioisotopes are still typically identified by hand-crafted classification algorithms, e.g., total counts or energy windowing, and exhibit relatively poor performance in detecting threats at the low false alarm rates required to support the stream of commerce. While some improvement to performance has been realized via the use of supervised machine learning, these classification algorithms typically utilize simulations in lieu of real data due to the sparsity of data for one or more classes. Accordingly, the performance of these algorithms is somewhat less than optimal when examining experiments or simulations with model mismatch. Consequently, in this work, we examine the application of a number of unsupervised machine learning, anomaly detection based algorithms, to circumvent the inverse crime when analyzing spectroscopy data for RPMs. We also compare anomaly detection results with those obtained via the use of supervised classification detection ML algorithms when model mismatch is introduced between the simulated threat items utilized for training/testing. Finally, we compared the performance of the PVT scintillators to those obtained with higher resolution detectors using both anomaly detection and supervised classification algorithms.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2023

Niowave Neutron Source Converter: Lead-Bismuth-Eutectic (LBE) Windowless Target Design and Evaluation

Los Alamos National Laboratory (LANL) is working with Niowave on the design and evaluation of their lead-bismuth-eutectic (LBE) windowless target (i.e., neutron source converter). Niowave plans to use 200 kW electron beam at 40 MeV beam energy to produce neutrons by photonuclear reaction with LBE. Then, the neutrons undergo fission at the surrounding uranium target assembly (UTA) to produce Molybdenum 99 (Mo-99) as a fission product, which eventually decays to Technetium-99 (Tc-99m). Tc-99m is one of important radioisotopes that is used for medical diagnostics. LANL conducted 3D multiphysics analysis for the Niowave neutron converter design and provided design assessment in thermohydraulic aspects. LANL conducted radiation transport calculations using Monte-Carlo N-Particle (MCNP) code with unstructured meshing scheme. The 3D volumetric heating profiles in the LBE and Stainless-Steel (SS) housing were imported into multiphase computational fluid dynamics (CFD) to obtain 3D temperature profiles of LBE and SS through conjugate heat transfer (CHT) analysis. The key findings are: LBE film thickness at the center of the beam is approximately 1.6 cm with a maximum LBE velocity of approximately 1.8 m/s, which is below a 2 m/s limit to avoid erosion issues on supporting structures; Heat deposition in the LBE peaks at ~1 cm depth from the LBE free-surface because of the forward interactions of electron, photon, and neutron with LBE; LBE maximum temperature is ~360 °C, which is below LBE evaporation initiative temperature, ~450 °C; LBE-SS interface temperature is ~350 °C, which is below the safety thermal limit to prevent severe corrosion on SS. The results indicate that Niowave’s neutron converter design satisfies both hydraulic and thermal criteria for safe operation. By virtue of such computational analysis, Niowave can move toward establishing an experimental setup to experimentally test their LBE neutron converter. The following sections describe the detailed work done by LANL.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Baseline Hypothetical Facility for the Production of 131 I, 99 Mo, and 133 Xe from HALEU Fission Targets

The report describes the development of a hypothetical facility to produce the pharmaceutical radioisotope 131 I at an amount of 60 curies per week via the fission of a High Assay Low Enriched Uranium (HALEU) target, along with the chemical and physical processes and equipment needed to separate the 131 I and co-produced 99 Mo and 133 Xe. The hypothetical design was carried out using a 10 MWt research reactor. The irradiation calculation determined that three HALEU targets with aluminum cladding can be used to produce 60 Ci/week of 131 I, 750 Ci/week of 99 Mo and 560 Ci/week of 133 Xe. The process selected for the baseline design uses caustic dissolution of the target material with ion exchange processes to separate and purify the iodine and molybdenum. The xenon is processed using a cryogenic carbon bed separation process. Target processing occurs in seven shielded hot cells with a total footprint of 16m 2 and waste management occurs in an eight hot cell with a 2.5 m 2 footprint. Waste generated from the processing of the three targets per week would generate less than 4 shielded drums of waste annually. These hot cells would need varying levels of shielding due to the amount of fission products being handled in the unit. Hot cell facilities also require support services including QA/QC, health physics, administrative staff, operator changing room, radiological buffer areas, and waste storage. The overall facility would require a footprint of 1050 m 2 with 20.25 m 2 of shielded hot cells.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Flow Measurements in Pressurized Helium Gas Cooling Channels: Rev. 1

Compressed helium gas is used to cool the NorthStar Medical Radioisotope (NMR) target system, also called the trident, chosen due to its superior heat transfer capabilities and its inability to react with Molybdenum-100 (Mo-100) during irradiation. To test the housing and NMR target stack at Los Alamos National Laboratory (LANL), two sets of helium gas flow loop facilities have been set-up and tested. One system is used for bench-top experiments to systematically investigate individual components of the NMR target, and the other, larger system is more representative of the system at NMR and is used for testing the full NMR target stack.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Next-Gen RTG Peltier Cooling Testing [Poster]

The Peltier Cooling Test was developed and performed on a General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) for the first time to support the refurbishment and recertification of a legacy flight unit. The GPHS-RTG flight units generate power for NASA space missions by converting heat from decaying Plutonium-238 into electricity using 572 thermocouples. The Peltier test successfully verified the electrical connections of the thermocouples by visually observing their thermal behavior under an applied current. Knowledge of the thermocouple electrical connections will be critical as the refurbishment and recertification plan moves forward.

42 ENGINEERING↗
DOE OSTI2023

Modeling and Analysis Support for Acceleratro-based Production of Mo-99

NorthStar Medical Radioisotopes, LLC, is in the process of commissioning a medical isotope production facility, which will use high-power electron accelerators to produce molybdenum-99 (Mo-99), the parent of technetium-99m (Tc-99m), through photonuclear reactions in molybdenum-100 (Mo-100). In this approach, a target comprising multiple thin disks of enriched molybdenum metal is bombarded with a 40-MeV electron beam. Electrons that impinge on the molybdenum target produce bremsstrahlung x-rays that cause the nuclear reaction. Because enriched Mo-100 is expensive, there is a desire to use as much beam power as possible to achieve maximum production yield and minimize the size of the target. This requirement leads to very high beam power density (heat deposition in the target), which creates challenging requirements for target cooling. In the latest concept developed by NorthStar, a stack of target (sintered molybdenum) disks is irradiated from two sides by a 40-MeV electron beam, with a total power of 250 kW (125 kW from each side). The target disks are cooled by pressurized helium gas flowing through channels between the disks. Inconel windows in the target housing form a pressure boundary between the helium within the housing and the evacuated beam tube.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

Advanced Fuel Cycle Cost Basis Report: Module D1-2 LWR Pelletized MOX Fuel Fabrication

Nature of this 2021 Module update from previous AFC-CBRs: Use of U,Pu MOX life cycle cost data from late 1970s Non-proliferation Assessment Systems Analysis Program (NASAP). This archived data has been updated in 2018-2019 to reflect today’s regulatory and economic conditions and is presented in 2017. For the lower unit cost MOX fabrication case the PuO 2 from the reprocessed LWR SNF is assumed to be fabricated immediately after aqueous PUREX reprocessing, thus minimizing the time for undesirable actinide radioisotopes, from the standpoint of radiation safety, to build in. Fabricated MOX utilizing separated and multi-year stored Pu from aqueously reprocessed SNF has also been added to this Module as a second LWR MOX fabrication variant, requiring additional and more costly glovebox design and operations to protect personnel. This new NASAP-informed data augments historical data and unit cost projections appearing in the 2009 (Shropshire et al 2009), 2012 (Dixon et al 2012), and 2017 Dixon et al 2017) AFC-CBRs. The “What-it-takes” 2017 unit fabrication cost values based on the updated NASAP studies are escalated to 2020$ for this 2021 Update Report.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

High Temperature Tensile Testing of Molybdenum Before and After Exposure in Flowing He at 600°C to 1000°C

ORNL supported NorthStar Medical Radioisotope’s accelerator-based concept to produce the medical isotope molybdenum-99 (Mo-99). The Mo targets are expected to experience in the accelerator temperature ranging from 200°C to 1000°C, and previous studies have demonstrated the embrittlement of Mo targets at room temperature when exposed to impure He at 800 to 1000°C. The goal of this project was to evaluate potential embrittlement at temperature ranging from 600°C to 1000°C for three Mo materials exposed at the same temperatures for 100h in high purity He (O 2 < 5ppm (µl/l)) with a flow rate of ~1m/s. Enriched Mo-100 (aMo) and conventional pressed and sintered Mo (UHP) disks were provided by NorthStar while low carbon arc cast rolled Mo, fabricated at ORNL, was used for comparison. The as fabricated rolled Mo exhibited superior tensile strength due to the alloy very fine grain size with limited ductility except at 1000°C with the elongation at rupture reaching 30%. The UHP Mo disks showed the lowest strength but highest ductility at 20-1000°C with significant strain hardening during tensile testing. The ductility of the aMo material was quite low at all temperatures due to a high density of voids at grain boundaries. Significant embrittlement of the aMo material was observed after exposure at 600°C to 1000°C, most likely because of oxygen diffusion and segregation at grain boundaries. No embrittlement was observed for the UHP Mo material, with excellent elongation at rupture for some of the specimens oxidized in He and tested at 600-1000°C. Significant variation in ductility from one UHP Mo specimen to another was, however, measured, both in the as fabricated and He-oxidized conditions. The rolled Mo was not affected by oxidation in He at 800°C, but a decrease in strength and increase in ductility was observed at 1000°C, likely due to the material recrystallization.

36 MATERIALS SCIENCE↗
DOE OSTI1995

Nuclear Safety [Vol. 36, No. 2, July-December 1995]

Nuclear Safety is a journal that covers significant issues in the field of nuclear safety. Its primary scope is safety in the design, construction, operation, and decommissioning of nuclear power reactors worldwide and the research and analysis activities that promote this goal, but it also encompasses the safety aspects of the entire nuclear fuel cycle, including fuel fabrication, spent-fuel processing and handling, and nuclear waste disposal, the handling of fissionable materials and radioisotopes, and the environmental effects of all these activities. Table of Contents for this issue follows. THE CHORNOBYL ACCIDENT: 195 The Chornobyl Accident Revisited, Part III: Chernobyl Source Term Release Dynamics and Reconstruction of Events During the Active Phase, A. R. Sich; GENERAL SAFETY CONSIDERATIONS: 218 Second ANS Workshop on the Safety of Soviet-Designed Nuclear Power Plants, R. A. Bari; 234 Elements of a Nuclear Criticality Safety Program, C. M. Hopper; 243 Rickover, Excellence, and Criticality Safety Programs, R. E. Wilson; ACCIDENT ANALYSIS: 249 Transient Analysis of the PIUS Advanced Reactor Design with the TRAC-PF1/MOD2 Code, B. E. Boyack, J. L Steiner, S. C. Harmony, H. J. Stumpf, and J. F. Lime; 278 The Hierarchy-By-Interval Approach to Identifying Important Models that Need Improvement in Severe-Accident Simulation Codes, T. J. Heames, M. Khatib-Rahbar, J. E. Kelly, R. P. Jenks-Johnson, and Y.-S. Chen; 290 RELAP5/MOD3 Code Coupling Model, R. P. Martin; 299 Missiles Caused by Severe Pressurized-Water Reactor Accidents, R. Krieg; DESIGN FEATURES: 310 Validation of COMMIX with Westinghouse AP-600 PCCS Test Data, J. G. Sun, T. H. Chien, J. Ding, and W T. Sha; ENVIRONMENTAL EFFECTS: 321 Spent Nuclear Fuel Characterization for a Bounding Reference Assembly for the Receiving Basin for Off-Site Fuel, S. D. Kahook, R. L. Garrett, L. R. Canas, and M J. Beckum; OPERATING EXPERIENCES: 332 Reactor Shutdown Experience, Compiled by J. W. Cletcher; U.S. NUCLEAR REGULATORY COMMISSION INFORMATION AND ANALYSES: 335 Reactor Coolant System Blowdown at Wolf Creek on September 17, 1994, J. V. Kauffman and S. L. Israel; RECENT DEVELOPMENTS: 344 Reports, Standards, and Safety Guides, D. S. Oueener; 349 Proposed Rule Changes as of June 30, 1995; ANNOUNCEMENTS: 320 Symposium on Acceptability of Risk From Radiation—Application to Manned Space Flight; 320 24th DOE/NRC Nuclear Air Cleaning and Treatment Conference; 361 Radiation Biology and Radiation Protection— Modern Developments and Tendencies in Radiation Biology; 362 1997 IEEE Sixth Conference on Human Factors and Power Plants; 354 The Authors; 360 Reviewers of Nuclear Safety, Vol. 36.

05 NUCLEAR FUELS↗
DOE OSTI2021

Production Facility Simulations for Annular LEU Targets

Eden Radioisotopes, LLC is designing a new molybdenum-99 (Mo-99) production facility based on a TRIGA-sized reactor with a core composed of low enriched uranium (LEU) targets. Reactor production is designed to exceed U.S. demand for Mo-99 using the fission processes. The nominal operational power is 1.8MW (less than 2.0MW, to satisfy the “non-power” reactor requirement) and desired irradiation scenarios include 7, 14, or 21 days of the irradiation for each target element. Safety limits for reactor operating margins are associated with such physical phenomena as fission gas release, fuel swelling, and stress cracking. As shown in the literature, one of the critical parameters defining safety margins for metallic uranium fuel is swelling. In its turn the fuel operational temperature is the main parameter impacting the swelling rate. This report documents the results of consecutive studies of reactor criticality, fission energy depositions, and cooling conditions for the target. The maximum temperature calculated for the LEU targets allows us to choose appropriate modeling approximation of the swelling. All obtained results refer to the preliminary targets and core designs provided by Eden. A criticality analysis was performed, and the results are listed mainly to cross-check Eden’s safety report and assume maximal neutron field disturbance for maximal reactivity. A brief description of the metallic uranium swelling model is provided in the Appendix.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

Draft Specification for Representing Gamma Radiation Spectra in QR codes

This document defines a proposed specification for representing gamma radiation spectra, as commonly produced by handheld Radioisotope Identifiers, as a QR code, or as a Uniform Resource Identifier (URI). The intended primary application is transferring spectra between locations or devices using standard smart-phone capabilities when data transmission would otherwise be challenging or not possible. The proposed encoding also enables embedding of spectra within other documents as hyperlinks.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Phase II Final Technical Report: Dynamic Gamma-ray Imaging for In Vivo Tracking of Microelement Transport Across Plant-Microbial Systems

The Department of Energy Office of Biological and Environmental Research (DOE BER) Mesoscale to Molecules Bioimaging Technology Program aims to develop new imaging and measurement technology to enable in situ and dynamic imaging across a range of spatial and temporal scales. Various imaging modalities are required to span the complete spatiotemporal landscape for bioenergy and environmental bioimaging needs. The high-resolution gamma-ray spectroscopy, imaging, and sensitivity of new high-purity germanium (HPGe) instruments provide a unique opportunity to complement and enhance these research goals. The HPGe-based Gamma-ray Imager for Plant Research (GIPR) developed here provides non-invasive, in vivo measurements to dynamically track the uptake and distribution of multiple gamma-emitting radioactive elements simultaneously as they move from the soil microbiome into living plants. The hand portable GIPR utilizes commercially available radioisotopes to provide spatial and temporal imaging of plant microelement exchange for the broader scientific community.

Kiser, Matthew↗
DOE OSTI2025

Sensitivity calibration of a Carestream HPX-1 image plate scanner

There is a need to measure the sensitivity of the image plate scanners used to scan Z shot data. The Carestream HPX-1 image plate scanner was tested, and its performance was characterized to determine the system sensitivity in terms of signal per incident photon as a function of x-ray energy. A Manson source was used to simultaneously expose an Amptek x-ray multi-channel analyzer and image plates, allowing for a comparison of the counts as a function of energy to the signal recorded on the image plates. NIST-certified radioactive sources were used to assign an absolute sensitivity. Results indicate that the HPX-1 scanner response matches the shape of the modeled response, allowing for absolute scaling using NIST-certified radioisotope sources. The HPX-1 scanner shows a stable response with measurements taken over one week. In contrast, the sensitivity of the DITABIS scanner was characterized using the same approach, but it exhibits changes in its response that varied by more than 50% over the span of 4 days.

42 ENGINEERING↗