WAM-D - Instrumentation Orange A 08:30 - 11:30
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| Chair(s): Frazier Bronson, Tom Voss
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WAM-D.2
08:30 Radio Frequency Immunity Testing of Two Ion Chamber Instruments SL Collins*, Ludlum Measurements, Inc.
Abstract: FAA (Federal Aviation Administration) guidelines require a periodic survey around radar sites where RF energy might be expected to be present. High power radar systems using klystrons have been known to leak dangerous x-ray fields. The Victoreen Model 440-RF/D has been the instrument of choice for these surveys, with some unspecified levels of RF-resistance. But with hard-to-find parts and maintainability problems, a replacement was desired. The Ludlum Model 9-4 was considered as a possible replacement, but had not been tested at higher RF power levels. RF standards are reviewed, with detail on frequencies and expected power levels. Applications for RF-immunity testing are becoming more relevant with the increasing use of the RF spectrum in the consumer market such as cell phones, Wi-Fi, Bluetooth, and ZigBee devices. In the presence of radiated electric fields, instrument wiring and traces on the PCBs begin to become more effective at receiving energy from electric fields. The field can induce voltages on both analog and digital signals, causing a host of issues. The purpose of RF immunity testing is to subject a product to a controlled RF stress that represents the likely level of stress that it might encountered in its operating environment, over a frequency range which is mostly dictated by practical aspects and experience of real-world problems. A description of the required equipment and testing procedures is given. A description of the data collection, evaluation, and then a discussion of the results on both instruments is given.
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WAM-D.3
08:45 SrI2 Scintillator: Low Energy Performance and Applications FL Bronson*, Mirion Technologies - Canberra
Abstract: Europium-doped Strontium Iodide (SrI2) scintillation detectors are starting to become commercially available. Due to the high light output and good linearity of the electron-light conversion these detectors have very good energy resolution. FWHM values of 3% at 662 keV are commonly available, with the potential to go even lower in the future. The resolution at 662 keV is significantly better than NaI, better than CeBr, and about the same as LaBr. Another favorable factor is that there is no internal radioactivity, unlike the La-138 natural radioactivity in LaBr scintillators. CZT detectors also are available with 2% resolution at 662 but are small in size, and have their resolution deterioriates below 200 keV. Both SrI and LaBr have good resolution at low energies, but the lack of internal contamination makes SrI very attractive for both low and high energies, and for low-level measurements of U-238, U-235, Am-241, and most nuclear medicine isotopes.
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WAM-D.4
09:30 Challenges In Monitoring For Transuranics JT Voss*, Voss Associates
; JA VOSS
Abstract: The radon/thoron interference in alpha contamination discrimination is due to the 7.68 MeV Po-214 and 6.00 MeV Po-218 alpha energy peaks from radon (Rn-222) decay and 8.78 MeV Po-212 and 6.00 MeV Bi-212 alpha energy peaks from thoron (Rn-220) decay. Radon and thoron exist everywhere in our environment and become one source of concern when personnel or their clothing or surfaces they may come in contact with becomes contaminated with this natural source of adioactivity. The main objectives of this presentation are to state methods to remove the radon and thoron interference from the detection of other alpha-emitting isotopes such as Pu-238, Pu-239, Am-241, and other alpha emitters. Further we wish to remove the radon and thoron interference when sampling for airborne transuranics. We want to be achieve an acceptable detection level in a short period of time while limiting or removing completely the interference due to radon and thoron progeny.
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WAM-D.5
09:45 Real-time Dosimetry of I-131 Using Nano fiber-Optic Detection Technology JM Raudabaugh*, Duke University
; BR Smiley, Duke University; NA Petry, Duke University; M Therien, Duke University; R Gunasingha, Duke University; T Yoshizumi, Duke University
Abstract: The purpose of this study was to develop a real-time in vivo radiation detection system for mixed ?beta and gamma emitters in liquid form, capable of simultaneously collecting signal from the mixed field, and the isolated gamma component. Beta particle detection has historically been difficult due to their short range in tissues and waters, and in vivo detection is limited by the size and nature of conventional detectors. Our laboratory has developed a scintillation detector system using a 600nm diameter fiber optic wire attached to a pressed pellet of the same diameter composed of organic scintillator material. The scintillation light caused by radiation is carried by the fiber optic wire to a photodiode which allows real time voltage data to be displayed on screen. These voltage values are proportional to the dose rate of the radiation field incident on the detector. Our goal was to demonstrate the detectors ability to accurately measure I-131 by comparing the decay rate of our signal with the known 8.02 day half. A vial containing a solution of I-131 was placed into a modified lead shielding pig. The vial was designed to allow two separate fiber-optic detectors to be inserted. One of the detectors was submerged into the solution, while the other was surrounded by an acrylic sheath of sufficient thickness to shield the most energetic I-131 beta particles. This allowed us to investigate signal generated from the mixed-field, as well as signal only from the gamma component of the decay. 17 measurements were taken over a 20 day time span by inserting the detectors into the vial containing the iodine solution. Our system measured a 9.02 ± 0.37 day half-life for the mixed-field fiber, and a 8.04 ± 0.47 day half-life for the gamma component fiber. These results illustrate the ability of our nano fiber-optic detector (Nano-FOD) to measure dose rate from mixed beta and gamma emitters such as I-131.
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WAM-D.6
10:00 Countering Detector Sensitivity Changes when Calibrating Neutron Survey Instruments and Reference Fields RK Piper*, Pacific Northwest National Laboratory
Abstract: A phenomenon observed in some neutron survey instruments involves a change in detector sensitivity as the integrated dose increases. This so-called radiation soaking effect is limited to proportional counter-based neutron detectors (e.g., BF3 and 3He detectors), and for some instruments, can result in a response increase as high as 30% before stabilizing. The elevated sensitivity eventually returns to the baseline condition, but the time to return appears to be inconsistent - even for a given detector. Unless acknowledged and properly compensated, this instability in detector response may lead to significant errors for an instrument being calibrated (e.g., a survey meter for field-use) and on reference fields being calibrated using a survey meter dedicated as a transfer standard. The potential influence upon neutron-related calibrations and measures taken to compensate for this effect are presented.
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WAM-D.7
10:15 Understanding the Radiation Soaking Effect in Neutron Survey Meters AV Mozhayev*, Pacific Northwest National Laboratory
; RK Piper, Pacific Northwest National Laboratory
Abstract: The drift in response of neutron survey meters that are based on moderated 3He and BF3 proportional counters has been reported and investigated by instrument calibration laboratories for over twenty years. When within a constant dose rate field of high intensity, dose rate readings of an instrument may steadily increase with a rate proportional to the field intensity, before reaching a relatively stable plateau. This phenomenon, so-called radiation soaking effect, has been attributed to the accumulation of charge on insulating surfaces inside the detector. This presentation provides results of a study specifically conducted to better understand the effect, and hence to possibly identify mitigation techniques. The magnitude of the effect in different instruments tested under the same conditions has been assessed, and a reason for the detector response variance clearly identified. A potential method to return an instrument sensitivity to its baseline level is also discussed
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WAM-D.8
10:30 Development of a Silicon-Plastic Scintillator Coincidence Beta-ray Spectrometer L Omar-Nazir*, McMaster University
; SH Byun, McMaster University
Abstract: With the impending change in the equivalent dose limit to the lens of the eye, as recommended by the International Commission on Radiological Protection in 2011, beta radiation poses a noteworthy challenge to personal dosimetry in a mixed beta-photon field for which there is a lack of knowledge at CANDU reactors. It is of great significance to know the beta and gamma-ray source term for accurate dosimetry to ensure the radiological safety of nuclear workers. For beta-ray spectral measurements at CANDU reactors, our group has been using a 2 cm thick plastic scintillator with a 5 cm diameter as it has moderate energy resolution, covers beta-ray energy up to 2.4 MeV and is convenient for accessing reactor sites. However, the plastic scintillator suffers from gamma-ray detection events, which requires a complicated and tedious gamma subtraction step in data analysis. Aiming at rejecting the gamma-ray detection events and collecting only the beta detection events, we present a new beta-ray spectrometer consisting of a thin silicon transmission detector operated in coincidence with a plastic scintillator. The responses of the coincidence spectrometer were characterized by Monte Carlo simulations and experimental measurements using 60Co, 137Cs, 36Cl, 90Sr/Y and 204Tl. Both simulation and experimental results showed that the gamma-ray count rate of the plastic scintillator was significantly reduced by coincidence operation and the spectral response of the plastic scintillator greatly improved. A comprehensive characterization of the coincidence spectrometer and further optimization are currently underway.
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WAM-D.9
10:45 Adding the Ability to Quantify Activity to a Radionuclide Identification Device DF Sullivan*, Mirion Technologies
; H Persson, Mirion Technologies; K Phillips, Mirion Technolgies; J Spruytte, Mirion Technologies; B Oginni, Mirion Technologies
Abstract: The SPIR-Ace, originally a Mirion Technologies Radionuclide Identification Device (RID), has been updated to incorporate the ability to not only rapidly identify radionuclides but also allows the quantification of the material being measured by making use of Canberras ISOCS (In-Situ Object Counting System) software. The SPIR-Ace is a hand held detection platform, equipped with a scintillation based detector, a 1024 channel Multi-Channel Analyzer (MCA) and a Geiger-Muller probe for measuring high dose rates. Available with either NaI(Tl) (1.4 inch diameter, 2 inch length) or LaBr3 (1 inch diameter, 1.3 inch length), the system is sensitive to gamma ray radiation between 20 to 3000 keV. The work presented here will detail the ISOCS characterization process that allows compatibility of the system with the ISOCS software. This includes a comprehensive measurement protocol to evaluate the full energy peak efficiency of the given system. An intermediate modeling stage is described, to allow the peak energy efficiency to be simulated after the model has been completely validated with the benchmark measurements. The final stage of the characterization process will show the validation of the ISOCS efficiency calibrations. This work will also show the results of a series of verification measurements, using various measurement geometries and a range of radionuclides, including the impact of environmental fluctuations on the temperature stability. The results of this work show that the measured activities, making use of either the LaBr3 or the NaI systems, had agreement to the certified activities to within 25% or better when employing an efficiency calibration that originated from the ISOCS characterization.
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WAM-D.10
11:00 Introducing the R Programming Package, "radsafer" MG Hogue*, SRNS
Abstract: There are currently over 12,000 packages available for R programming. Until recently though, none of these packages were dedicated to providing helpful functions for health physicists. The availability of the new package, “radsafer,” puts at the user's fingertips easy access to many of the functions otherwise performed by calculator, or by error-prone spreadsheet methods. It also shares a number of functions that save time or improve analysis.
The radsafer package covers a number of typical HP functions such as source decay, half-life estimation, air density correction, and stay-time. It will show how to quickly correct for size differences between reference sources and swipes or air samples in alpha and beta counting. Functions for rate meter simulation and scaler simulation will help the user put readings into context. Finally, utilities for MCNP® input card generation will be introduced for interested users.
About radsafer: The radsafer package is a new addition to the R programming language. It provides radiation safety related functions. It is now available on Github and can be installed with devtools::install_github("markhogue/radsafer"). Submission of the package to CRAN (the Comprehensive R Archive Network at https://cran.r-project.org/) is anticipated before the conference.
MCNP® and Monte Carlo N-Particle® are registered trademarks owned by Triad National Security, LLC, manager and operator of Los Alamos National Laboratory.
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WAM-D.11
11:15 Novel, Low-Cost, Light-Weight, High Efficiency (H* Capable) Neutron Detection-Dosimetry RP Taleyarkhan*, Purdue University
; B Archambault, Consultant; A Sansone, Purdue University; T Grimes, Pacific Northwest National Laboratory; A Hagen, Pacific Northwest National Laboratory
Abstract: During 2017-2018, DOE’s Nuclear Safety Research and Development Program sponsored a collaborative project between Purdue University and Oak Ridge National Laboratory (ORNL) for the developing the novel tensioned metastable fluid detector (TMFD) technology for enabling 100% gamma-beta blind, neutron spectroscopy-enabled tensioned H*10 dosimetry. TMFDs work by placing fluids under negative (sub-vacuum) pressures to make them selectively sensitive for detecting a range of nuclear particle types (e.g., neutrons, alphas, fission fragments) based on their linear energy transfer while remaining 100% gamma-beta blind (even in 700 R/h fields). We developed the high (60-80% neutron) intrinsic efficiency prototype H*TMFDs, which were successfully assessed (at ORNL) vs Bonner Sphere Spectrometry, resulting in H*10 dose estimates within +/- 20% for shielded and unshielded neutron sources. Two H*TMFD system architectures are available for use by health physicists (HPs) – the ~2.5 kg HP-H*TMFD), and the ~10kg H*TMFD area monitor consisting of an array of 4 TMFDs of different sizes (including one with borated fluid). The configurations enable neutron energy spectroscopy (single bin for < 0.1 MeV, and 152 energy bins in the 0.1-15 MeV range) and H*(10) dosimetry from ~5 µRem/h to 10+ Rem/h. The HPH*TMFD and H*TMFD array spectrometers can be controlled-operated remotely, as well as via PC- based graphical user interface. The novel capability for a low-cost, light-weight, efficient neutron spectroscopy-based dosimetry (at ultra-low 5-10 µRem/h, and 20+ Rem/h in survey mode) constitutes an exciting opportunity for use in the HP, safety, security and safeguards arenas.
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WAM-D.12
11:30 Continuous and Unattended Spectroscopic Operation and Analysis with the Mirion Data Analyst J Zickefoose*, Mirion Technologies (Canberra) Inc
; F Bronson, Mirion Technologies (Canberra) Inc; B Huckins, Mirion Technologies (Canberra) Inc; T Anderson, Mirion Technologies (Canberra) Inc; S Laskos, Mirion Technologies (Canberra) Inc; D Sullivan, Mirion Technologies (Canberra) Inc
Abstract: A number of applications benefit from continuous and repeated gamma ray spectral acquisition, analysis, and reporting. These applications include the measurement of fluid or gas flowing through a pipe, material on a conveyor belt, a detector in a free air plume, as well as nuclide mapping by detectors attached to drones. In these cases, important criteria include: no lapses in data acquisition during monitoring, full data analysis and reporting can be applied in real time, the spectra and results are stored for post analysis review, and notifications are available when concentration levels rise above predetermined limits. The Data Analyst is a small device designed to accommodate these needs and provide the flexibility needed to configure measurement, data collection, and data analysis for a variety of applications. Continuous acquisition is accomplished with novel software and hardware which allows for unattended acquisition, analysis, and storage of data over multiple measurement workflow definitions. Each workflow is an independent analysis stream where acquisition time, analysis algorithm parameters, and reporting options may be configured. Since multiple averaging times are allowed for a single data stream it is possible to attain swift reaction times in parallel with very low minimum detectable concentrations. As a direct result of the multiple averaging times, the dynamic range of the applied system may cover eight orders of magnitude depending on the intrinsic range of the radiation detector being utilized. The analysis protocol leverages existing Genie 2000 analysis algorithms and applies them in real time to each workflow as it completes an averaging interval. When one or more intervals are complete the device automatically starts a new interval without the loss of data. The device also accommodates the use of analog inputs, GPIO communication, GPS location, and either wired or wireless communications. The features and capabilities of the device as well as a number of applications will be discussed.
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