TPM-E - Health Physics Instrumentation Room 302AB 14:30 - 17:30
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| Chair(s): Rick Adams
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TPM-E.1
14:30 Development of Metal Halide Perovskite Semiconductors for Radiation Sensing R Tan*, University of Tennessee
; ED Lukosi, University of Tennessee; B Dryzhakov, University of Tennessee; M Ahmadi, University of Tennessee; B Hu, University of Tennessee; J Charest, University of Tennessee; K Higgins, University of Tennessee; C Busch, University of Tennessee
Abstract: In recent years, metal halide perovskites (MHPs) have emerged as a potential solution to address the increasing demand for medium-resolution, low-cost ionizing radiation detectors. One organic MHP variant, methylammonium lead tribromide (CH3NH3PbBr3, MAPbBr3, or MAPB) shows potential given its relatively cheap solution growths, suitable electronic properties, high effective atomic number for gamma sensing, and inherent atomic fraction of hydrogen of up to 50% for fast neutron sensing. This work presents the development of MAPB at the University of Tennessee, which encompasses the entire semiconductor detector fabrication process including the strategic incorporation of stabilizing elements into the perovskite structure, surface defect mitigation during sensor fabrication, judicious selection of electrode materials, characterization of bulk transport properties through radiation exposure, and computational methods of correcting for charge transport deficiencies within the detector bulk to improve energy resolution. These efforts collectively contribute towards demonstrating MAPB’s potential as a versatile semiconductor capable of gamma sensing, fast/thermal neutron sensing, and X-ray imaging, and the results justify its continued development as a low-cost semiconductor alternative for a variety of radiation sensing applications.
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TPM-E.2
14:45 Epithermal Neutron Field for Dosimetry and Instrument Testing AV Mozhayev*, Pacific Northwest Natl Lab
; RK Piper, Pacific Northwest Natl Lab; JR Meza, Pacific Northwest Natl Lab; JF Christ, Pacific Northwest Natl Lab; RK Berg, Pacific Northwest Natl Lab; AL Maine, Pacific Northwest Natl Lab; EB Dutcher, Pacific Northwest Natl Lab
Abstract: Staff at the Calibration Laboratory for Ionizing Radiation (CLIR) at Pacific Northwest National Laboratory routinely conduct testing and calibration of various radiation detection equipment. In terms of neutrons, the standardized fields are represented by D2O-moderated and unmoderated Cf-252 fission sources, AmBe and a deuterium-tritium generator. While the fields generated by the sources cover intermediate and fast neutron energy regions, all of them lack a well-defined epithermal component of the neutron spectrum. In order to fill the gap, the CLIR staff have designed and built a polyethylene reflecting structure that, when complemented with existing heavy water and polyethylene moderators, could provide an effective epithermal field without undermining the intensity of Cf-252 sources. This presentation is to illustrate the design of the structure and the resulting neutron field characteristics.
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TPM-E.3
15:00 Application and Comparison of Multi-Robot Exploration Methods for Radioactive Source Localization LK Chung*, Stanford University
; A Chan, Stanford University; Y Li, Stanford University; A Wong, Stanford University; CC Davis, University of Michigan; JD Noey, University of Michigan; KJ Kearfott, University of Michigan
Abstract: In situations involving routine radiological operations, lost radioactive sources, decommissioning and cleanup of nuclear facilities, and radiological terrorist events, efficient and accurate source localization algorithms for unmanned aerial vehicles (UAV) mounted with radiation detectors are important for mitigating potential risks of human exposure to radioactive materials. While much literature is focussed on localization methods for a single UAV, there has also been an increase of interest in applying these techniques for multiple agents, since the resulting policy of distributed, multi-robot control is scalable to a variety of situations, robust to individual robot failure, and modular. Multi robot exploration also allows for faster exploration compared to single robot methods, allowing for the radiation source to be localized efficiently. We aim to apply an information-theoretic control policy to a multi-robot exploration problem for a radioactive source localization application. The control law utilizes current radiation measurements as inputs to a Bayesian filter to compute the information gradient. This informs each robot to move in a direction that locally increases the mutual information of the entire system. We will also compare this control policy to state-of-the art exploration algorithms in the field of distributed control and determine which is best suited to the particular problem of radioactive source localization.
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TPM-E.4
15:15 Design Improvements to a Low Cost Radiation-Detecting Weather Station for Nuclear Science Outreach AJ Kent*, University of Michigan
; JD Noey, University of Michigan; KJ Kearfott, University of Michigan
Abstract: Most weather stations collect many forms of climate data including humidity, temperature, wind speed, wind direction, solar UV, soil moisture, soil temperature, and barometric pressure. A system has been undergoing development over the past several years which adds measurements of ionizing radiation, namely radon and background gammas, to draw attention to the presence and levels of background radiation. The design, intended for deployment in high schools and worldwide by the general public, is to be inexpensive (less than $500) and accurate (±15% across devices in all measurements). It will ultimately interface with a central database which makes information readily accessible by anyone. Recent advancements made to this Radiation Weather Station project included selecting more accurate sensors, combining hookups to simplify wiring, and implementing measures to reduce interference from outside sources. The upgraded sensor, the BME680, is a newer version of the previously installed BME280, is no more expensive, and has higher accuracy components. The codebase required updating for this substitution. The combined hookups arose from a design principle change from a modular to a combined architecture. Printed circuit board shielding and choice of wiring type between devices were explored for interference reduction. These combined advancements led to a more functional product and a system that is ready to move into beta testing.
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TPM-E.5
15:30 Interfacing a Radiation Detector to an Intelligent Radiation Awareness Drone RA Kim*, University of Michigan
; ME Trager, University of Michigan; CC Davis, University of Michigan; RS Ho, University of Michigan; AJ Kent, University of Michigan; JD Noey, University of Michigan; KJ Kearfott, University of Michigan
Abstract: An intelligent radiation-seeking drone, of value for response following radiological incidents, requires communication with radiation sensors not typically found on consumer drones. An efficient algorithm planned to map radiological sources in an area requires a separate onboard computer, chosen as a RaspberryPi4. Open-source PX4 drone flight control firmware exists for the PixHawk4, the selected consumer flight computer. Communication drivers are available for GPS and radios, but not ionizing radiation detectors. Pre-existing software lacks specialized computational functions and feedback loops to the flight controller essential for automated flight paths informed by the planned algorithm output. This work seeks to develop robust and reliable communications between the sensors and drone, enabling dynamic response to continuously improving information about radiation sources distributions. A universal asynchronous receiver-transmitter transmission system will be written to send data from the Raspberry Pi 4 to the PixHawk4. Sensor drivers allowing the PixHawk4 to receive data will be flashed onto the board, and drivers will be written in a library for the Raspberry Pi 4 to communicate with sensors and the flight computer. The ultimate goal is to establish reliable communications between the unique components and sensors of a radiation-seeking drone. Data sent from the Raspberry Pi 4 will be compared with the data received by the flight controller for precise correspondence to verify reliability. Successful communication will be noted based on the flight logs recorded by QGroundControl, the software which provides real-time drone data, e.g. location, while allowing drone control from a computer. Wireless communications will be considered reliable by meeting a standard of packet loss on drone and ground control software of <0.1%.
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TPM-E.6
15:45 Electronics Circuit Design Considerations for Novel Radiation Detection Instruments JD Noey*, University of Michigan
; AJ Kent, University of Michigan; L Jautakas, University of Michigan; TW Kennings, University of Michigan; KJ Kearfott, University of Michigan
Abstract: Effective circuits play an important role in the function of radiation detection instruments. Such instruments are generally easy to operate and perform robustly under different environmental conditions. Users may be unaware of the design and testing efforts expended in creation of the electronics circuits critical to their radiation detector system. However, there are instances when designing and understanding a circuit is necessary. This is the case for research and development of radiation detection systems for new applications demanding altered specifications such as size, shape, weight, ability to interface with different computers, and cost. Because of the desirability of interfacing radiation detectors with microcomputers and cellphones running unique software, a cost-constrained team consisting of full-time college students undertook the design of circuits for projects involving gas-filled detectors and scintillators coupled to silicon photomultipliers. Circuits were designed and specific components chosen for a project. These were tested using bread-boarding, followed by the design of printed circuit boards. Various design iterations were made, including cycling through different components after testing revealed undesirable characteristics. Many unexpected challenges can arise even when good conventional electrical engineering practices are followed for extremely simple circuits. For example, it was discovered that one device simply would not function in one specific location, a site later discovered to be subject to intermittent but significant radiofrequency interferences. Fortunately, there are several approaches that can be adopted to create an effective circuit that is highly efficient, compact in size, and easy to assemble when used for radiation detection instruments. Circuit design techniques and overall experiences, leading to a great appreciation for the electronics hidden in radiation protection instruments, will be shared for discussion.
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TPM-E.7
16:00 Break
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TPM-E.8
16:15 A Mapping and Navigation Algorithm for an Intelligent Radiation Awareness Drone CC Davis*, University of Michigan
; LK Chung, Stanford University; ME Trager, University of Michigan; RA Kim, University of Michigan; JD Noey, University of Michigan; KJ Kearfott, University of Michigan
Abstract: Both the immediate response to a nuclear response as well as long-term followup for mitigation and other purposes would greatly benefit from having the capability of rapidly and remotely identifying radionuclides and mapping their distributions in space. An autonomous unmanned aerial vehicle (UAV) could be used to improve upon both these areas. This project has as its goals the optimization of algorithms which will interface with the navigational software of a small UAV to accomplish exactly that. Prior work in this area treated it as an image-reconstruction problem, exploring Least-Squares and Maximum A Posteriori (MAP) methods. Recursive Bayesian Estimation was also studied. Of these three, the first and last have shown the most immediate promise, as a MAP estimator depends upon resolution, grid placement, and an appropriate prior. Additional research has shown that treating this localization as a Hill-Climbing problem also holds promise. Specifically, coordinate descent and stochastic methods provide an efficient and distinct approach. A number of these algorithms and their performance will be compared, in addition to naive and brute-force solutions serving as a baseline reference. A unique challenge is provided by multiple signals in close proximity. In this case, the sources’ signals will be discriminated using frequency analysis and the power spectral density. Experiments involving non-ionizing radiation sources, such WiFi from a router placed on open ground, are planned to measure the success rate of each algorithm. Both elapsed time and number of computational iterations will be compared. In single-source tests, the total distance traveled will be compared to the Euclidean distance from the starting position to the source. The experimental path will be compared to the ideal path via curvilinear integration. Consideration will be given to extrapolation to ionizing radiation detectors based upon the experimental results.
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TPM-E.9
16:30 Analysis of Minimum Detectable Concentrations for Environmental Samples in a Novel High Sensitivity Large Volume Spectroscopy System JD Noey*, University of Michigan
; KJ Kearfott, University of Michigan
Abstract: A novel gamma ray spectroscopy system consisting of eight readily available 11 cm x 42.5 cm x 5.5 cm NaI(TI) detectors was designed to maximize sensitivity with some compromise in energy resolution. Two configurations of this well-shielded system were tested: one consisting of an octagonal detection cylinder with a sensitive sample volume of ~25,000 cm3, and the second a cross-like detector prism with a sample volume of ~10,000 cm3. Background spectra, with and without different types of blank samples present, were collected during sequential 4 h periods over 30 d. Optimal relative sample and background counting times were derived for different anticipated samples. Careful calibration of the system was performed using samples of different geometries and densities with known radionuclide concentrations. Detection efficiencies were computed and empirical extrapolations performed to account for samples of different volumes, densities, and energies from the calibration sources. Radioactivity concentrations in previously collected mill tailings and soil samples were then measured. An error analysis, including expected minimum detectable concentrations and the relative sources of uncertainties for different samples, was performed. The ultrasensitive gamma-ray spectroscopy system and methods developed are practical and advantageous for the rapid identification and quantification of radionuclide contaminants in environmental samples.
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TPM-E.10
16:45 Quality Control Program for High Precision Radiation Dose Delivery in Operational Health Physics Facilities JD Noey, University of Michigan
; CJ Stewart*, University of Michigan; KJ Kearfott, University of Michigan
Abstract: Radiation doses delivered for high precision applications in medical physics, such as external beam radiotherapy, are monitored through strict quality assurance programs. However, high precision dose delivery in operational health physics, such as used for dosimeter and detector calibration, is typically monitored less rigorously due to a less critical connection to immediate human health and safety. Dosimetry and instrument calibration facilities could benefit from enhanced quality assurance programs, as undesirable changes could be detected sooner and a better understanding of the true accuracy of dose delivery would be gained. A quality control program was introduced for a 137Cs dosimetry calibration source with documented prior failures. Data were collected and monitored over a long period of time in a uniform area of the beam to study long-term effects of continual source use. Various subgrouping methods were used to develop different Phase I control charts that excel at determining assignable causes based on data outliers. Control limits were set based on acceptable values of estimated population standard deviation. The diverse use of control charts was successful at isolating and determining certain assignable causes based on events that could trigger unreliable data. To further determine and characterize future events, additional data were collected in a systematic format to appropriately adjust the control limits. Data were then interpreted using Phase II methods by analyzing the process as opposed to only the last subsequent measurements. Phase II approaches were applied to look at smaller process shifts, which may predict future source failure. A designed experiment was planned to better determine assignable causes based on known changes to the operation. The resulting quality control program proved useful for obtaining reliable dose measurements, ensuring that the measurement operation is consistent, and predicting if a source failure will occur.
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TPM-E.11
17:00 Building Our Own: Design Challenges for an Intelligent Radiation Awareness Drone ME Trager*, University of Michigan
; RA Kim, University of Michigan; CC Davis, University of Michigan; RS Ho, University of Michigan; A Phatke, University of Michigan; KH Sumter, University of Michigan; M Kidambi, University of Michigan; P Wang, University of Michigan; JD Noey, University of Michigan; KJ Kearfott, University of Michigan
Abstract: A drone with its flight path determined by a unique radiation mapping algorithm informed by an integral radiation detector was designed by an undergraduate engineering team. This drone, Intelligent Radiation Awareness Drone (iRAD), is controlled using the open source software PX4 Autopilot and was created using readily available parts. iRAD is a 6-motor multicopter that uses a customized DJI F550 drone frame. It is equipped with the necessary hardware for collision avoidance and terrain holding. This includes a depth camera, flow sensor, LiDar sensor, a PixHawk4 flight controller, and a Raspberry Pi companion computer. The goal of iRAD is to survey radiologically hazardous environments efficiently and semi-autonomously using both flight hardware and a hazardous navigation algorithm driving movements. The primary airborne vehicle design issues facing iRAD are minimizing weight while maximizing possible flying time, specified as 15 min minimum. The limiting factors are battery size and the number of onboard sensors, each adding mass and requiring power. Another key concern is the interface between the hazardous navigation algorithm and the autopilot software. The algorithm must calculate and send coordinates to the PX4 controls software using measurements captured in real time, as opposed to the usual operation of a multicopter using a set flight path. Physically testing iRAD in large-scale is possible primarily using WiFi emitters to replicate ionizing radiation over a large area. iRAD’s payload must consequently be modular with the ability to interface with both a radiation detector and WiFi sensor. The ultimate design, results of testing, and team management are included in this presentation.
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TPM-E.12
17:15 Reevaluating Legacy Neutron Survey Meters NB Rashidifard*, Mirion Technologies
Abstract: The 9 Inch “Remball” is a tried-and-true neutron survey meter that has been in used for many decades at any facility where neutron dose is present. Modern facilities, such as Cyclotron and Fusion, can have a much different neutron energy profiles than that of the Nuclear Power sites where a newer solution can be advantageous. In field experience has shown that poor combinations of instrumentation and neutron energy can provide under reporting of dose rates by a factor of up to four. This leads to poor ALARA planning and potential for exceeding planned dose allotments. Use of legacy instrumentation, while trusted, can offers physical and safety burden. Neutron energy response functions for a variety of instrumentation, both legacy and modern, were compared and categorized for facilities where they provide the best overall response while gaining advantages in terms of ergonomics and safety. This will lead to improved dose rate information as well as other practical factors.
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