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All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

A Search for FRB 121102-like Persistent Radio-luminous Sources—Candidates and Implications for the FRB Rate and Searches

The localization of the repeating fast radio burst (FRB), FRB 121102, suggests that it is associated with a persistent radio-luminous compact source in the FRB host galaxy. Using the FIRST radio catalog, I present a search for luminous persistent sources in nearby galaxies, with radio luminosities >10% of the FRB 121102 persistent source luminosity. The galaxy sample contains about 30% of the total galaxy g-band luminosity within <108 Mpc, in a footprint of 10,600 deg{sup 2}. After rejecting sources likely due to active galactic nuclei activity or background sources, I am left with 11 candidates that are presumably associated with galactic disks or star-formation regions. At least some of these candidates are likely to be due to chance alignment. In addition, I find 85 sources within 1{sup ′′} of galactic nuclei. Assuming that the radio persistent sources are not related to galactic nuclei and that they follow the galaxy g-band light, the 11 sources imply a 95% confidence upper limit on the space density of luminous persistent sources of ≲5×10{sup −5} Mpc{sup −3}, and that at any given time only a small fraction of galaxies host a radio-luminous persistent source (≲10{sup −3} L{sub ∗}{sup −1}). Assuming a persistent source lifetime of 100 years, this implies a birth rate of ≲5×10{sup −7} yr{sup −1} Mpc{sup −3}. Given the FRB volumetric rate, and assuming that all FRBs repeat and are associated with persistent radio sources, this sets a lower limit on the rate of FRB events per persistent source of ≳0.8 yr{sup −1}. I argue that these 11 candidates are good targets for FRB searches and I estimate the FRB event rate from these candidates.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1989

Restrictive loads powered by separate or by common electrical sources

In designing a multiple load electrical system, the designer may wish to compare the performance of two setups: a common electrical source powering all loads, or separate electrical sources powering individual loads. Three types of electrical sources: an ideal voltage source, an ideal current source, and solar cell source powering resistive loads were analyzed for their performances in separate and common source systems. A mathematical proof is given, for each case, indicating the merit of the separate or common source system. The main conclusions are: (1) identical resistive loads powered by ideal voltage sources perform the same in both system setups, (2) nonidentical resistive loads powered by ideal voltage sources perform the same in both system setups, (3) nonidentical resistive loads powered by ideal current sources have higher performance in separate source systems, and (4) nonidentical resistive loads powered by solar cells have higher performance in a common source system for a wide range of load resistances.

Appelbaum, J.↗
NASA NTRS2016

The Chandra Deep Field-South Survey: 7 Ms Source Catalogs

We present X-ray source catalogs for the approx. 7 Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 arcmin2. Utilizing WAVDETECT for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0 keV, 0.5-2.0 keV, and 2-7 keV. A supplementary source catalog is also provided, including 47 lower-significance sources that have bright (Ks < or = 23) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous approx. 4 Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central approx. 1 arcmin2 region of 1.9 x 10(exp -17), 6.4 x 10(exp -18), and 2.7 x 10(exp -17) erg/sq cm/s in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0 keV flux levels. The highest X-ray source density reaches approx. 50,500/sq deg, and 47% +/- 4 of these sources are AGNs (approx. 23,900/sq deg).

cosmology: observations – diffuse radiation – ↗
NASA NTRS2022

Newly Identified Climatically and Environmentally Significant High-Latitude Dust Sources

Dust particles from high latitudes have a potentially large local, regional, and global significance to climate and the environment as short-lived climate forcers, air pollutants, and nutrient sources. Identifying the locations of local dust sources and their emission, transport, and deposition processes is important for understanding the multiple impacts of high-latitude dust (HLD) on the Earth’s systems. Here, we identify, describe, and quantify the source intensity (SI) values, which show the potential of soil surfaces for dust emission scaled to values 0 to 1 concerning globally best productive sources, using the Global Sand and Dust Storms Source Base Map (G-SDS-SBM). This includes 64 HLD sources in our collection for the northern (Alaska, Canada, Denmark, Greenland, Iceland, Svalbard, Sweden, and Russia) and southern (Antarctica and Patagonia) high latitudes. Activity from most of these HLD sources shows seasonal character. It is estimated that high-latitude land areas with higher (SI ≥ 0.5), very high (SI ≥ 0.7), and the highest potential (SI ≥ 0.9) for dust emission cover > 1 670 000 km 2 , > 560 000 km 2 , and > 240 000 km 2 , respectively. In the Arctic HLD region (≥ 60◦ N), land area with SI ≥ 0.5 is 5.5 % (1 035 059 km 2 ), area with SI ≥ 0.7 is 2.3 % (440 804 km 2 ), and area with SI ≥ 0.9 is 1.1 % (208 701 km 2 ). Minimum SI values in the northern HLD region are about 3 orders of magnitude smaller, indicating that the dust sources of this region greatly depend on weather conditions. Our spatial dust source distribution analysis modeling results showed evidence supporting a northern HLD belt, defined as the area north of 50◦ N, with a “transitional HLD-source area” extending at latitudes 50–58◦ N in Eurasia and 50–55◦ N in Canada and a “cold HLD-source area” including areas north of 60◦ N in Eurasia and north of 58◦ N in Canada, with currently “no dust source” area between the HLD and low-latitude dust (LLD) dust belt, except for British Columbia. Using the global atmospheric transport model SILAM, we estimated that 1.0 % of the global dust emission originated from the high-latitude regions. About 57 % of the dust deposition in snow- and ice-covered Arctic regions was from HLD sources. In the southern HLD region, soil surface conditions are favorable for dust emission during the whole year. Climate change can cause a decrease in the duration of snow cover, retreat of glaciers, and an increase in drought, heatwave intensity, and frequency, leading to the increasing frequency of topsoil conditions favorable for dust emission, which increases the probability of dust storms. Our study provides a step forward to improve the representation of HLD in models and to monitor, quantify, and assess the environmental and climate significance of HLD.

high latitude dust↗
DOE OSTI2015

Special Analysis for the Disposal of the Oak Ridge National Laboratory General Radioactive Sources Waste Stream at the Area 5 Radioactive Waste Management Site, Nevada National Security Site, Nye County, Nevada

This special analysis (SA) evaluates whether the Oak Ridge National Laboratory (ORNL) General Radioactive Sources waste stream (ORNLSOURCES01, Revision 3) is suitable for disposal by shallow land burial (SLB) at the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada National Security Site (NNSS). The ORNL General Radioactive Sources waste stream consists of sealed sources and solid radioactive sources that are no longer needed (ORNL 2015). The ORNL General Radioactive Sources waste stream required a special analysis because 26 radionuclides exceeded the NNSS Waste Acceptance Criteria (WAC) Action Levels (U.S. Department of Energy, National Nuclear Security Administration Nevada Field Office [NNSA/NFO] 2015). However, review of the generator’s method to calculate waste concentration indicates that the concentrations are significantly overestimated. Waste concentrations are recalculated in this analysis using a list of individual sources provided by the generator. One radionuclide, radium-226 (226Ra), still exceeds its action level and a Special Analysis (SA) is required. The results indicate that all performance objectives can be met with disposal of the ORNL General Radioactive Sources in a SLB trench. Addition of the ORNL General Radioactive Sources inventory slightly increases the 222Rn flux density. The maximum mean and 95th percentile flux density remain less than the performance objective throughout the compliance period. The ORNL General Radioactive Sources waste stream had no significant effect on the maximum mean and 95th percentile for all other performance assessment results. The ORNL General Radioactive Sources waste stream is suitable for disposal by SLB at the Area 5 RWMS. However, because the activity concentrations on the waste profile sheet are significantly overestimated, approval of the sheet could potentially allow the disposal of high activity radiation sources. To ensure the generator does not include large radiation sources in its waste stream, a control is recommended on the maximum individual source activity from this generator.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Security of Mobile Radiological Sources: Overview of Industry Applied Technologies

Small radiological sources used in industrial settings recurrently require transit between job sites. Securing these sources, while stationary, can be addressed with standard security approaches and equipment. Transport of these sources increases the risk and complexity of managing and maintaining control of these sources. Implementing methodologies to securely monitor and locate sources improves response and resolution of anomalous events during transit. The Mobile Source Transit Security (MSTS) system was developed to improve security and provide situational awareness of these mobile sources throughout their job cycle. The MSTS development effort focused on creating a set of systems that could be successfully implemented in industrial radiography and well-logging applications. The MSTS team worked to address source presence and location through use and storage. The MSTS system monitors radiological sources as they move from the base of operations to the job site and back. The system provides near-real-time monitoring of the mobile source location and status and early notification of source loss or theft by transmitting operational status and alerting anomalous conditions over telematic links worldwide. The MSTS system can trigger an armed response or initiation of search and recovery operations and will automatically alert management and responsible staff if a radioactive source is lost or stolen whether it is on-site, in transport, or in storage.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2013

Current Situation for Management of Disused Sealed Radioactive Sources in Japan - 13025

As for the Sealed Radioactive Source currently used in Japan, many of them are imported from overseas. The U.S., Canada, Germany, the Netherlands, Belgium and Czech Republic are the main exporting States. Many of disused sealed radioactive sources are being returned to exporting States. The sealed radioactive sources which cannot be returned to exporting States are appropriately kept in the domestic storage facility. So, there are not main problem on the long term management of disused sealed radioactive sources in Japan. However, there are some difficulties on repatriate. One is reservation of a means of transport. The sea mail which conveys radioactive sources owing to reduction of movement of international cargo is decreasing in number. And there is a denial of shipment. Other one is that the manufacturer has already resigned from the work and cannot return disused sealed radioactive sources, or a manufacturer cannot specify and disused sources cannot be returned. The disused sealed radioactive source which cannot be repatriated is a little in term of radioactivity. As for the establishment of national measure of final disposal facility for disused sealed radioactive sources, in Japan, it is not yet installed with difficulty. Since there are many countries for which installation of a final disposal facility for disused sealed radioactive sources is difficult, the source manufacture country should respond positively to return the source which was manufactured and sold in the past. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2018

Introducing a risk aggregation rationale for mapping risks to aquifers from point- and diffuse-sources–proof-of-concept using contamination data from industrial lagoons

Highlights: • Aquifer risk mapping is introduced for contaminants acting as point/diffuse-sources. • Innovations are framed by risk cells based on Source-Pathway-Receptor-Source (SPRC). • Point-source (Risk Cell 1) and diffuse-source (Risk Cell 2) use sets of algorithms. • Algorithms include MODPATH, DRASTIC, GWPI and are integrated on a modular basis. • Risk Cells 1/2 are aggregated giving fit-for-purpose results as proof-of-concept. - Abstract: Proof-of-concept for a methodology is presented on mapping risks to aquifers impacted from point- and diffuse-sources, where mapping or indexing refers to relative but not absolute values. The methodology is generic but tested by investigating impacts of a risk exposure from industrial wastewater lagoons. The methodology is innovative for using the qualitative Source-Pathways-Receptors-Consequences (SPRC) framework to aggregate risks from both point-sources and diffuse-sources through breaking down a study area into SPRC risk cells. In this paper, two risk cells are required as: (i) Cell 1 is directly impacted from a point-source; and (ii) Cell 2 is impacted by diffuse-sources to slowly contaminate the aquifer by infiltration over a large area. Indexing both types of risk cells generically comprise three tiered processes: (i) binary indexing establishes if a grid cell is at a potential risk or not; (ii) graded indexing measures the strength of the risk pathways from source to receptors; and (iii) local indexing measures intrinsic potentials at the grid cell to propagate the risk. These three processes apply to both point- and diffuse-sources but with different mathematical formulations. The proof-of-concept for the methodology of risk aggregation using the SPRC framework is supported by results of a study area, in which a set of performance metrics are used by comparing with the measurements. The results are found to be fit-for-purpose for serving as proactive management tools and to provide a deeper insight into potential impacts of adverse effects.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

X-RAY POINT-SOURCE POPULATIONS CONSTITUTING THE GALACTIC RIDGE X-RAY EMISSION

Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2-8 keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, we present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, we divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, we speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N-log S curve of the 2-8 keV band, the group A non-thermal sources are dominant above Almost-Equal-To 10{sup -14} erg cm{sup -2} s{sup -1}, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K{alpha} emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Radiation Safety of Sealed Radioactive Sources

Sealed radioactive sources are used in a wide variety of occupational settings and under differing regulatory/licensing structures. The definition of a sealed radioactive source varies between US regulatory authorities and standard-setting organizations. Potential problems with sealed sources cover a range of risks and impacts. The loss of control of high activity sealed sources can result in very high or even fatal doses to members of the public who come in contact with them. Sources that are not adequately sealed, and that fail, can cause spread of contamination and potential intake of radioactive material. There is also the possibility that sealed sources may be (or threatened to be) used for terrorist purposes and disruptive opportunities. Until fairly recently, generally-licensed sealed sources and devices received little, if any, regulatory oversight, and were often forgotten, lost or unaccounted for. Nonetheless, generally licensed devices can contain fairly significant quantities of radioactive material and there is some potential for exposure if a device is treated in a way that it was never designed. Industrial radiographers use and handle high activity and/or high-dose rate sealed sources in the field with a high degree of independence and minimal regulatory oversight. Failure to follow operational procedures and properly handle radiography sources can and has resulted in serious injuries and death. Industrial radiographers have experienced a disproportionately large fraction of incidents that result in unintended exposure to radiation. Sources do not have to contain significant quantities of radioactive material to cause problems in the event of their failure. A loss of integrity can cause the spread of contamination and potential exposure to workers and members of the public. The NCRP has previously provided recommendations on select aspects of sealed source programs. Future efforts to provide recommendations for sealed source programs are discussed.

radioactive material↗
DOE OSTI2011

Modeling a Hypothetical {sup 170}Tm Source for Brachytherapy Applications

Purpose: To perform absorbed dose calculations based on Monte Carlo simulations for a hypothetical {sup 170}Tm source and to investigate the influence of encapsulating material on the energy spectrum of the emitted electrons and photons. Methods: GEANT4 Monte Carlo code version 9.2 patch 2 was used to simulate the decay process of {sup 170}Tm and to calculate the absorbed dose distribution using the GEANT4 Penelope physics models. A hypothetical {sup 170}Tm source based on the Flexisource brachytherapy design with the active core set as a pure thulium cylinder (length 3.5 mm and diameter 0.6 mm) and different cylindrical source encapsulations (length 5 mm and thickness 0.125 mm) constructed of titanium, stainless-steel, gold, or platinum were simulated. The radial dose function for the line source approximation was calculated following the TG-43U1 formalism for the stainless-steel encapsulation. Results: For the titanium and stainless-steel encapsulation, 94% of the total bremsstrahlung is produced inside the core, 4.8 and 5.5% in titanium and stainless-steel capsules, respectively, and less than 1% in water. For the gold capsule, 85% is produced inside the core, 14.2% inside the gold capsule, and a negligible amount (<1%) in water. Platinum encapsulation resulted in bremsstrahlung effects similar to those with the gold encapsulation. The range of the beta particles decreases by 1.1 mm with the stainless-steel encapsulation compared to the bare source but the tissue will still receive dose from the beta particles several millimeters from the source capsule. The gold and platinum capsules not only absorb most of the electrons but also attenuate low energy photons. The mean energy of the photons escaping the core and the stainless-steel capsule is 113 keV while for the gold and platinum the mean energy is 160 keV and 165 keV, respectively. Conclusions: A {sup 170}Tm source is primarily a bremsstrahlung source, with the majority of bremsstrahlung photons being generated in the source core and experiencing little attenuation in the source encapsulation. Electrons are efficiently absorbed by the gold and platinum encapsulations. However, for the stainless-steel capsule (or other lower Z encapsulations) electrons will escape. The dose from these electrons is dominant over the photon dose in the first few millimeter but is not taken into account by current standard treatment planning systems. The total energy spectrum of photons emerging from the source depends on the encapsulation composition and results in mean photon energies well above 100 keV. This is higher than the main gamma-ray energy peak at 84 keV. Based on our results, the use of {sup 170}Tm as a brachytherapy source presents notable challenges.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2013

Determination of transit dose profile for a {sup 192}Ir HDR source

Purpose: Several studies have reported methodologies to calculate and correct the transit dose component of the moving radiation source for high dose rate (HDR) brachytherapy planning systems. However, most of these works employ the average source speed, which varies significantly with the measurement technique used, and does not represent a realistic speed profile, therefore, providing an inaccurate dose determination. In this work, the authors quantified the transit dose component of a HDR unit based on the measurement of the instantaneous source speed to produce more accurate dose values. Methods: The Nucletron microSelectron-HDR Ir-192 source was characterized considering the Task Group 43 (TG-43U1) specifications. The transit dose component was considered through the calculation of the dose distribution using a Monte Carlo particle transport code, MCNP5, for each source position and correcting it by the source speed. The instantaneous source speed measurements were performed in a previous work using two optical fibers connected to a photomultiplier and an oscilloscope. Calculated doses were validated by comparing relative dose profiles with those obtained experimentally using radiochromic films. Results: TG-43U1 source parameters were calculated to validate the Monte Carlo simulations. These agreed with the literature, with differences below 1% for the majority of the points. Calculated dose profiles without transit dose were also validated by comparison with ONCENTRA{sup Registered-Sign} Brachy v. 3.3 dose values, yielding differences within 1.5%. Dose profiles obtained with MCNP5 corrected using the instantaneous source speed profile showed differences near dwell positions of up to 800% in comparison to values corrected using the average source speed, but they are in good agreement with the experimental data, showing a maximum discrepancy of approximately 3% of the maximum dose. Near a dwell position the transit dose is about 22% of the dwell dose delivered by the source dwelling 1 s and reached 104.0 cGy per irradiation in a hypothetical clinical case studied in this work. Conclusions: The present work demonstrated that the transit dose correction based on average source speed fails to accurately correct the dose, indicating that the correct speed profile should be considered. The impact on total dose due to the transit dose correction near the dwell positions is significant and should be considered more carefully in treatments with high dose rate, several catheters, multiple dwell positions, small dwell times, and several fractions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

A generic high-dose rate {sup 192}Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism

Purpose: In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-based dose calculation algorithms (MBDCAs), treatment planning systems (TPSs) using a MBDCA require a set of well-defined test case plans characterized by Monte Carlo (MC) methods. This also permits direct dose comparison to TG-43 reference data. Such test case plans should be made available for use in the software commissioning process performed by clinical end users. To this end, a hypothetical, generic high-dose rate (HDR) {sup 192}Ir source and a virtual water phantom were designed, which can be imported into a TPS. Methods: A hypothetical, generic HDR {sup 192}Ir source was designed based on commercially available sources as well as a virtual, cubic water phantom that can be imported into any TPS in DICOM format. The dose distribution of the generic {sup 192}Ir source when placed at the center of the cubic phantom, and away from the center under altered scatter conditions, was evaluated using two commercial MBDCAs [Oncentra{sup ®} Brachy with advanced collapsed-cone engine (ACE) and BrachyVision ACUROS{sup TM}]. Dose comparisons were performed using state-of-the-art MC codes for radiation transport, including ALGEBRA, BrachyDose, GEANT4, MCNP5, MCNP6, and PENELOPE2008. The methodologies adhered to recommendations in the AAPM TG-229 report on high-energy brachytherapy source dosimetry. TG-43 dosimetry parameters, an along-away dose-rate table, and primary and scatter separated (PSS) data were obtained. The virtual water phantom of (201){sup 3} voxels (1 mm sides) was used to evaluate the calculated dose distributions. Two test case plans involving a single position of the generic HDR {sup 192}Ir source in this phantom were prepared: (i) source centered in the phantom and (ii) source displaced 7 cm laterally from the center. Datasets were independently produced by different investigators. MC results were then compared against dose calculated using TG-43 and MBDCA methods. Results: TG-43 and PSS datasets were generated for the generic source, the PSS data for use with the ACE algorithm. The dose-rate constant values obtained from seven MC simulations, performed independently using different codes, were in excellent agreement, yielding an average of 1.1109 ± 0.0004 cGy/(h U) (k = 1, Type A uncertainty). MC calculated dose-rate distributions for the two plans were also found to be in excellent agreement, with differences within type A uncertainties. Differences between commercial MBDCA and MC results were test, position, and calculation parameter dependent. On average, however, these differences were within 1% for ACUROS and 2% for ACE at clinically relevant distances. Conclusions: A hypothetical, generic HDR {sup 192}Ir source was designed and implemented in two commercially available TPSs employing different MBDCAs. Reference dose distributions for this source were benchmarked and used for the evaluation of MBDCA calculations employing a virtual, cubic water phantom in the form of a CT DICOM image series. The implementation of a generic source of identical design in all TPSs using MBDCAs is an important step toward supporting univocal commissioning procedures and direct comparisons between TPSs.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

A multicenter study to quantify systematic variations and associated uncertainties in source positioning with commonly used HDR afterloaders and ring applicators for the treatment of cervical carcinomas

Purpose: The reconstruction of radiation source position in the treatment planning system is a key part of the applicator reconstruction process in high dose rate (HDR) brachytherapy treatment of cervical carcinomas. The steep dose gradients, of as much as 12%/mm, associated with typical cervix treatments emphasize the importance of accurate and precise determination of source positions. However, a variety of methodologies with a range in associated measurement uncertainties, of up to ±2.5 mm, are currently employed by various centers to do this. In addition, a recent pilot study by Awunor et al. [“Direct reconstruction and associated uncertainties of {sup 192}Ir source dwell positions in ring applicators using gafchromic film in the treatment planning of HDR brachytherapy cervix patients,” Phys. Med. Biol. 58, 3207–3225 (2013)] reported source positional differences of up to 2.6 mm between ring sets of the same type and geometry. This suggests a need for a comprehensive study to assess and quantify systematic source position variations between commonly used ring applicators and HDR afterloaders across multiple centers. Methods: Eighty-six rings from 20 European brachytherapy centers were audited in the form of a postal audit with each center collecting the data independently. The data were collected by setting up the rings using a bespoke jig and irradiating gafchromic films at predetermined dwell positions using four afterloader types, MicroSelectron, Flexitron, GammaMed, and MultiSource, from three manufacturers, Nucletron, Varian, and Eckert & Ziegler BEBIG. Five different ring types in six sizes (Ø25–Ø35 mm) and two angles (45° and 60°) were used. Coordinates of irradiated positions relative to the ring center were determined and collated, and source position differences quantified by ring type, size, and angle. Results: The mean expanded measurement uncertainty (k = 2) along the direction of source travel was ±1.4 mm. The standard deviation associated with the source position reproducibility was within ±1.0 mm for all afterloaders. Maximum source positional variations of 2.1 and 3.9, 1.8 and 5.4, and 2.3 and 3.4 mm were observed at standard treatment positions for the Ø26, Ø30, and Ø32 mm sized 45° and 60° rings, respectively. Mean positional differences between a majority of the rings were within ±1.0 mm. Mean positional differences between a majority of the intracenter ring sets were within the expanded measurement uncertainty. When comparing the 45°–60° source paths, mean differences of 1.6, 0.9, and 0.9 mm were observed across the Ø26, Ø30 (MicroSelectron), and Ø32 mm (GammaMed) rings, respectively. When comparing to manufacturer source path models, maximum offsets of 1.9 and 2.1, 2.6 and 2.3, and 0.8 and 1.6 mm were observed for the Ø26, Ø30 (MicroSelectron), and Ø30 mm (Flexitron) sized 45° and 60° rings, respectively. When comparing the audit to ring commissioning data of participating centers, mean differences of up to 2.4 mm were observed. Conclusions: A majority of the audited rings showed a good degree of manufacturer consistency; however, substantial positional variation observed between some rings emphasizes the importance of commissioning each ring before clinical use. Differences observed between audit and commissioning data also indicate some variation in source treatment positions across centers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Radiation Source Mapping with Bayesian Inverse Methods

In this work, we present a method to map the spectral and spatial distributions of radioactive sources using a limited number of detectors. Locating and identifying radioactive materials is important for border monitoring, in accounting for special nuclear material in processing facilities, and in cleanup operations following a radioactive material spill. Most methods to analyze these types of problems make restrictive assumptions about the distribution of the source. In contrast, the source mapping method presented here allows an arbitrary three-dimensional distribution in space and a gamma peak distribution in energy. To apply the method, the problem is cast as an inverse problem where the system’s geometry and material composition are known and fixed, while the radiation source distribution is sought. A probabilistic Bayesian approach is used to solve the resulting inverse problem since the system of equations is ill-posed. The posterior is maximized with a Newton optimization method. The probabilistic approach also provides estimates of the confidence in the final source map prediction. A set of adjoint, discrete ordinates flux solutions, obtained in this work by the Denovo code, is required to efficiently compute detector responses from a candidate source distribution. These adjoint fluxes form the linear mapping from the state space to the response space. The test of the method’s success is simultaneously locating a set of 137 Cs and 60 Co gamma sources in a room. This test problem is solved using experimental measurements that we collected for this purpose. Because of the weak sources available for use in the experiment, some of the expected photopeaks were not distinguishable from the Compton continuum. However, by supplanting 14 flawed measurements (out of a total of 69) with synthetic responses computed by MCNP, the proof-of-principle source mapping was successful. The locations of the sources were predicted within 25 cm for two of the sources and 90 cm for the third, in a room with an ~4-x 4-m floor plan. Finally, the predicted source intensities were within a factor of ten of their true value.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2012

Intrinsic Radiation Source Generation with the ISC Package: Data Comparisons and Benchmarking

The characterization of radioactive emissions from unstable isotopes (intrinsic radiation) is necessary for shielding and radiological-dose calculations from radioactive materials. While most radiation transport codes, e.g., MCNP [X-5 Monte Carlo Team, 2003], provide the capability to input user prescribed source definitions, such as radioactive emissions, they do not provide the capability to calculate the correct radioactive-source definition given the material compositions. Special modifications to MCNP have been developed in the past to allow the user to specify an intrinsic source, but these modification have not been implemented into the primary source base [Estes et al., 1988]. To facilitate the description of the intrinsic radiation source from a material with a specific composition, the Intrinsic Source Constructor library (LIBISC) and MCNP Intrinsic Source Constructor (MISC) utility have been written. The combination of LIBISC and MISC will be herein referred to as the ISC package. LIBISC is a statically linkable C++ library that provides the necessary functionality to construct the intrinsic-radiation source generated by a material. Furthermore, LIBISC provides the ability use different particle-emission databases, radioactive-decay databases, and natural-abundance databases allowing the user flexibility in the specification of the source, if one database is preferred over others. LIBISC also provides functionality for aging materials and producing a thick-target bremsstrahlung photon source approximation from the electron emissions. The MISC utility links to LIBISC and facilitates the description of intrinsic-radiation sources into a format directly usable with the MCNP transport code. Through a series of input keywords and arguments the MISC user can specify the material, age the material if desired, and produce a source description of the radioactive emissions from the material in an MCNP readable format. Further details of using the MISC utility can be obtained from the user guide [Solomon, 2012]. The remainder of this report presents a discussion of the databases available to LIBISC and MISC, a discussion of the models employed by LIBISC, a comparison of the thick-target bremsstrahlung model employed, a benchmark comparison to plutonium and depleted-uranium spheres, and a comparison of the available particle-emission databases.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Searching for Compact Radio Sources Associated with UCH ii Regions

Ultra-compact (UC)H ii regions represent a very early stage of massive star formation. The structure and evolution of these regions are not yet fully understood. Interferometric observations showed in recent years that compact sources of uncertain nature are associated with some UCH ii regions. To examine this, we carried out VLA 1.3 cm observations in the A configuration of selected UCH ii regions in order to report additional cases of compact sources embedded in UCH ii regions. With these observations, we find 13 compact sources that are associated with 9 UCH ii regions. Although we cannot establish an unambiguous nature for the newly detected sources, we assess some of their observational properties. According to the results, we can distinguish between two types of compact sources. One type corresponds to sources that are probably deeply embedded in the dense ionized gas of the UCH ii region. These sources are photoevaporated by the exciting star of the region and will last for 10{sup 4}–10{sup 5} years. They may play a crucial role in the evolution of the UCH ii region as the photoevaporated material could replenish the expanding plasma and might provide a solution to the so-called lifetime problem of these regions. The second type of compact sources is not associated with the densest ionized gas of the region. A few of these sources appear resolved and may be photoevaporating objects such as those of the first type, but with significantly lower mass depletion rates. The remaining sources of this second type appear unresolved, and their properties are varied. We speculate on the similarity between the sources of the second type and those of the Orion population of radio sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

List-Mode source injection algorithm for detectors with arbitrary pose and trajectory

environments, introducing actual sources is usually neither feasible nor economical. It is more practical to move the detector (whether airborne, vehicle-borne, or human-portable) through the test environment and then later artificially superimpose either measured or simulated source signatures on the recorded background data. We present a source injection (SI) algorithm that inserts source events into list-mode background data. It is designed to accommodate cases where “injection data” are available only at a limited set of locations. Stochastic methods are employed both to select source events from a measured dataset containing both source and background events, and to scale the number of selected events to match the field conditions of detector-source distance, air attenuation, acquisition duration, and the relative strength of the measured and injected sources. The algorithm is deployed as part of the Airborne Radiation Enhanced-sensor System (ARES) Advanced Technology Demonstration, and is applied to field data obtained using the ARES detector system. For this helicopter-borne detection system, we describe a practical ground-based measurement scheme for acquiring data for later injection. These data are then injected into background data acquired during flight, where arbitrary detector poses and trajectories are possible. Similar flight paths are traversed with and without actual 137Cs and 60Co sources present. SI is applied to the source-absent datasets, and the results are compared to the source-present datasets. SI output is found to be consistent with measured activity within the estimated uncertainties in GPS position and source strength.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗