Sealed Sources Research Articles

Attempt to re-estimate organ doses of victims in non-homogeneous exposure accident by means of the state-of-the-art Mesh-type Reference Computational Phantom-a case study of an IR-192 source accident.

An attempt was made to estimate organ doses of a victim in a high-dose non-homogeneous exposure accident caused by a sealed 192Ir gamma-ray source. The Gilan accident was selected as a case study. Organ doses including testis, red bone marrow and so on were properly estimated by applying the Monte Carlo calculation with the state-of-the-art adult male Mesh type Reference Computational Phantom. By introducing a complicated exposure scenario, the dose distribution on the right chest of the victim in the Gilan accident could be reproduced to a certain extent.

A Novel Anthropometric Phantom for Rapid Radiological Triage: A Quick Sort Triage Solution.

Rapidly identifying individuals who have received internal radiation exposure above action guidelines is crucial for mitigating health risks and addressing public concerns immediately following a radiological event involving the dispersal of radioactive materials. This study describes a novel triage method using a conventional Geiger-Mueller (GM) detector to select those individuals from the large group of persons who may have received an intake of radioactive material at levels corresponding to one Clinical Decision Guide (CDG). The triage method involves placing a portable GM detector against the lower anterior torso of a sitting person as they bend over to surround the detector with their body. The response of the GM detector is evaluated using a new, specially designed anthropometric phantom that simulates combined tissues of the lower thorax and gastrointestinal (GI) tract and is fabricated with a tissue substitute material that matches the overall radiological properties of human tissue present in this body region. The phantom has four separate layers of tissue substitute material with ports to accommodate a single GM detector at the center and one or more sealed radioactive sources that can be arranged to characterize the detector response for a variety of source distributions, including a "hot spot." In this study, the response of a Ludlum Model 133-4 GM detector was evaluated using sealed sources of 232Th and 137Cs to determine the measurement efficiency for a quantity of activity present in the abdomen within a few hours post-intake equivalent to 1 CDG. Results demonstrate that the Quick Sort triage procedure using a single GM detector placed against the abdomen of a person can reliably detect internal deposition resulting from an intake equivalent to 1 CDG for 232Th or a significantly lower activity of 137Cs within a few hours following a radiological incident. The evaluation was performed over a wide range of photon energies, so the Quick Sort triage procedure is expected to be suitable for most fission products distributed uniformly within the abdomen or as a single "hot spot."

Optimizing neutron shielding: A specialised container approach for Disused Sealed Radioactive Sources and orphan neutron emitters

Shielding Disused Sealed Radioactive Sources (DSRSs) and orphan neutron sources, such as 252Cf, pose challenges due to the high penetration of neutrons, induced radioactivity in shielding materials, and the limited availability of compact, effective shielding materials. This study addresses these challenges by proposing a specialized container for the safe transport, conditioning, and disposal of neutron-emitting DSRSs and orphan sources. The computational tool that was used in this study is the Monte Carlo N-Particle (MCNP). The investigation begins with an examination of moderation materials, including high-density polyethylene (HDPE), paraffin, and water-extended polyester (WEP). Subsequently, four concrete types, namely Ordinary, Barite, Portland, and Serpentine Concrete, are scrutinized. Employing a comprehensive methodology, the design of the container is optimized to effectively moderate and absorb neutron emissions. The findings of this study demonstrate that the designed compact container can safely handle activities exceeding those studied, effectively managing up to 10 μg (about 0.2 GBq) 252Cf without exceeding 25 μSv/h at the outer container contact. This suggests a promising solution for the secure management of high-activity neutron-emitting sources.

Monte Carlo simulation of shielding materials in storage drums for 241Am-Be disused sealed radioactive sources

Disused Sealed Radioactive Sources (DSRS) containing neutron sources such as 241Am-Be require careful management due to neutron radiation. However, finding readily available and effective combination layer shielding materials for practical use to safely contain 241Am-Be can be challenging. The main objective of this study is to investigate the configuration of shielding materials and determine the maximum activity of 241Am-Be sources that can be safely stored in a 200-L drum. A three-layer shielding approach using a 200-L drum as a storage container, with sequential layers of lead (Pb), polyethylene (PE), and ordinary Portland concrete (OPC), achieves the lowest dose rates compared to other combination sequences, as shown by Monte Carlo simulations. With a fixed lead thickness and varying polyethylene and ordinary Portland concrete thicknesses, Monte Carlo simulations using the Particle and Heavy Ion Transport code System (PHITS) demonstrate that this drum design can safely accommodate activities ranging from 22.01 Ci to 72.92 Ci of 241Am-Be. The fitted model equation determines the required polyethylene thickness for any activity within this range. Additionally, case-based simulation results indicate that Indonesia's total inventory of 241Am-Be DSRS can be stored in three 200-L drums with a polyethylene thickness of 15 cm. This configuration meets international standards, ensuring the dose rate does not exceed 2 mSv/h at the surface and 0.1 mSv/h at 1 m from the drum's surface.

Discerning β-emitting radioactivity from caesium-137 γ radiation via bremsstrahlung for in-situ groundwater monitoring

A qualitative approach to discern the relative contributions of 137Cs and 90Sr in-solution with a monitoring probe is described, based on a comparison of X- and γ-ray photon spectra. The bremsstrahlung yield from 90Sr has been measured as a function of distance (x) from a cerium bromide scintillation detector relative to the 137Cs γ-ray full-energy peak response. The utility of two, count-independent shape factor parameters has been compared: the ratio of the sum of the counts in the 60–800 keV region to the full-energy peak response associated with the 137Cs 662 keV γ-ray line, termed for the benefit of this paper as SF1, and the ratio of counts in the 60–350 keV region to those in the 350–450 keV region, defined in this work as SF2. These parameters probe the presence of isotopes associated with clear full-energy spectral lines and bremsstrahlung, respectively. They have been calibrated as a function of x with sealed sources in the laboratory and both are observed to be asymptotic as x→0. This approach has been tested with a variety of open, laboratory-based liquid samples comprising 90Sr and 137Cs, and in a water-based, contaminated medium in the field associated with a sump at a low-level waste disposal facility on the former fast reactor site at Dounreay, UK. The highest response in both SF1 and SF2 measured in this work is observed in these on-site measurements, consistent with x→0, implying both 90Sr and 137Cs presenting together in solution. This is consistent with prior, laboratory-based analysis of the sump media, and suggests that the β−-emitter contribution (anticipated to comprise 90Sr and 90Y) is very near the probe, consistent with the solution being in contact with it. This is of relevance where the β−/γ composition of contaminated groundwater, in-situ, is not well understood or where migratory changes in activity are suspected.

Investigating resource-efficient neutron/gamma classification ML models targeting eFPGAs

There has been considerable interest and resulting progress in implementing machine learning (ML) models in hardware over the last several years from the particle and nuclear physics communities. A big driver has been the release of the Python package, hls4ml, which has enabled porting models specified and trained using Python ML libraries to register transfer level (RTL) code. So far, the primary end targets have been commercial field-programmable gate arrays (FPGAs) or synthesized custom blocks on application specific integrated circuits (ASICs). However, recent developments in open-source embedded FPGA (eFPGA) frameworks now provide an alternate, more flexible pathway for implementing ML models in hardware. These customized eFPGA fabrics can be integrated as part of an overall chip design. In general, the decision between a fully custom, eFPGA, or commercial FPGA ML implementation will depend on the details of the end-use application. In this work, we explored the parameter space for eFPGA implementations of fully-connected neural network (fcNN) and boosted decision tree (BDT) models using the task of neutron/gamma classification with a specific focus on resource efficiency. We used data collected using an AmBe sealed source incident on Stilbene, which was optically coupled to an OnSemi J-series silicon photomultiplier (SiPM) to generate training and test data for this study. We investigated relevant input features and the effects of bit-resolution and sampling rate as well as trade-offs in hyperparameters for both ML architectures while tracking total resource usage. The performance metric used to track model performance was the calculated neutron efficiency at a gamma leakage of 10-3. The results of the study will be used to aid the specification of an eFPGA fabric, which will be integrated as part of a test chip.

Multi-Organizational Insights Into Radiological Safety Standards in High-Dose Rate Brachytherapy.

The review provides an extensive study of regulations and recommendations set forth by organizations worldwide in the domain of high-dose rate (HDR) brachytherapy for the prevention and mitigation of radiation hazards. The relevant reports and publications by the International Commission on Radiological Protection (ICRP), International Atomic Energy Agency (IAEA), American Association of Physicists in Medicine (AAPM), United States (US) Nuclear Regulatory Commission (NRC), and Atomic Energy Regulatory Board (AERB) were accessed, and necessary information was compiled to clarify and understand concepts, similarities, and differences in safety standards concerning to the topic. The regulations and guidance are categorized under three major components of safety, namely layout, equipment, and source. Layout category accesses structure, design, layout, and survey. The equipment category summarizes the requirements of equipment, installation, commissioning, quality assurance (QA) and performance, safety precautions and preparedness, safety procedures, and instructions. The source category includes requirements for sealed source possession and use, calibration, categorization, certification, licensing, QA tests, and security. IAEA gives inclusive guidance on radiation protection and regulatory requirements, forming the basis of reference for other organizations worldwide. AERB regulates the radiation facilities in India; therefore, most set-ups follow their safety standards and instructions.

Fabrication of sealed source scandium-46 (46Sc) as an alternative calibration standard

Fabrication of sealed source scandium-46 (46Sc) as an alternative calibration standard

Handling of radioactive waste from the use of radionuclides in hospitals

The waste that is generated during the different applications of radionuclides in medicine is considered as biomedical radioactive waste. This waste includes contaminated materials and syringes generated from Nuclear Medicine procedures, unused radioactive seeds from implants in Radiation Oncology as well as sealed sources used for calibration purposes, which are no longer useful. The overall goal of biomedical radioactive waste handling is to minimize the hazards posed by the waste prior to discharge or disposal. In order to plan the treatment of radionuclides in medical facilities, it is important to design an effective system for the overall management of radioactive biomedical waste. In this scientific paper I make a general assessment of the planning methods used in the handling of radioactive waste in medical facilities, including the collection, separation and packaging of radioactive biomedical waste.

Characterisation of sealed radioactive source for nuclear forensic purposes

Characterisation of sealed radioactive source for nuclear forensic purposes

Advances in Head-and-Neck Interventional Radiotherapy (Brachytherapy)

Interventional radiotherapy, also known as brachytherapy, is the use of sealed radioactive sources that directly deliver radiation to the tumor or tumor bed. Its unique dose distribution profile allows for high conformality, making it a very useful modality in the treatment of cancers in the head and neck, where different organs and substructures that serve various but related functions are situated close to each other. In recent years, we have seen several important technological breakthroughs in the field, especially regarding its application in head and neck cancers. These include advances in treatment delivery, dosimetry planning , image guidance , and catheter positioning techniques . These innovations, which often require interdisciplinary interventions, have resulted in enhanced treatment accuracy, and therefore, major clinical advantages in terms of increased local control and decreased toxicity, as well as economic benefits. In order to highlight the differences from old brachytherapy techniques, a more appropriate terminology should perhaps be adopted, to signify these advancements that resulted in new opportunities, approaches and better outcomes – interventional radiotherapy (IRT). Such a change in terminology will not only allow recognition of these advances, but also a meaningful distinction from obsolete techniques and suboptimal outcomes that are associated with traditional brachytherapy. This is very important in increasing awareness among professionals outside the field of radiation oncology. We briefly review these recent advances, the current indications, and future directions for IRT in head-and-neck cancers. Keywords : interventional radiotherapy, brachytherapy, head-and-neck cancers, image-guidance

Deposition of Fine-Pitch Indium Bumps on Single Die

Photolithographic lift-off at wafer level is a wellestablished method for depositing indium bumps onto pixels of electronic components such as sensors and application-specific integrated circuits (ASIC). These indium bumps form interconnects between pixels of the components during flip-chip bonding to make devices such as radiation detectors. Such components are not always available on wafer-scale, and single dies need to be processed in small-scale production, R&D, or for Cd(Zn)Te detector material. Photolithography on single dies is ineffective due to the edge-bead of photoresist that compromises perfect indium deposition onto pixels near the periphery of the die. To utilize the maximum surface area of a die, a rigid mask with apertures (shadow mask) is an adequate substitute for the photoresist. Different mask designs and production techniques for fine-pitch indium bump arrays are investigated by testing electroformed stencils or micromachined silicon (Si) membranes as shadow masks. For the indium deposition, the sensor and ASIC dies are clamped into custom-made jigs that include shadow masks. Alternatively, dies can be adhered to shadow masks with soluble adhesive. The apertures of a mask are aligned to the pixel array of the detector component. Bump arrays with 250μm- and 100μm-pitch were demonstrated with electroformed stencils. For smaller pitch (55μm) and bump diameter of ~20μm, specialized masks from Si membranes are tested. Components with successfully deposited indium bump arrays were subsequently flip-chip bonded at room temperature without reflowing the indium. A bond yield of at least 99.9% pixels for such flip-chip bonded radiation detector was shown using the read-out signal from exposure with a flat field X-ray radiation of an Am-241 sealed source.

Growth difficulties and growth of crack free Eu2+ activated KSr2I5 scintillator single crystal by vertical bridgman-stockbarger technique for radiation detection applications

Europium activated potassium strontium iodide (KSr2I5:0.5Eu2+) compound was synthesized and refined by indigenous zone-refinement experimental set-up. The impurities that are insoluble in the KSr2I5:Eu2+ compound was filtered by using a specifically programmed dual chamber quartz ampoule with frit filter method. Temperature profile of this in-house built vertical transparent Bridgman-Stockbarger technique growth furnace is optimized to grow quality single crystals of KSr2I5:Eu2+. From the photoluminescence emission spectrum a typical 4f6 5d1 – 4f7 transition is observed for a broad emission peak at 432 nm whereas a broad emission peak at 448 nm was obtained from the X-ray excited radioluminescence spectrum. The gamma ray spectrometer was administered to detect the scintillation properties of the grown crystal. The scintillation decay time was calculated for the KSr2I5:Eu2+ crystal wherein the energy resolution under 137Cs sealed gamma source is found to be 3.5 % at 662 KeV.

Optimization and experimental characterization of the innovative thermo-brachytherapy seed for prostate cancer treatment.

Adjuvant administration of hyperthermia (HT) with radiation therapy in the treatment of cancer has been extensively studied in the past five decades. Concurrent use of the two modalities leads to both complementary and synergetic enhancements in tumor management, but presents a practical challenge. Their simultaneous administration using the same implantable thermo-brachytherapy (TB) seed source has been established theoretically through magnetically mediated heat induction with ferromagnetic materials. Careful consideration, however, showed that regular ferromagnetic alloys lack the required conductivity to generate enough power through eddy current to overcome heat dissipation due to blood perfusion at clinically measuredrates. We characterized the TB implant that combines a sealed radioactive source with a ferrimagnetic ceramic (ferrite) core, serving as a self-regulating HT source when placed in an alternating electromagnetic field. To increase the heat production and uniformity of temperature distribution the empty spacers between radioisotope seeds were replaced by hyperthermia-only (HT-only)seeds. The heat generation due to eddy currents circulating in the seed's thin metal shell, surrounding the core, depends drastically on the core permeability. We identified a soft ferrite material ( ) as the best candidate for the core, owing to its high permeability, the HT-range Curie temperature, adjustable through material composition, and a sharp Curie transition, leading to heat self-regulation, with no invasive thermometry required. The core permeability as a function of temperature was calculated based on measured resistor-inductor (RL) circuit parameters and material B-H curves. The thickness of the shell was optimized separately for TB and HT-only seeds, having slightly different dimensions. Heat generation was calculated using the power versus temperature approximation. Finally, the temperature distribution for a realistic prostate LDR brachytherapy plan was modeled with COMSOL Multiphysics for a set of blood perfusion rates found in theliterature. The small size of the investigated ferrite core samples resulted in demagnetization significantly decreasing the relative permeability from its intrinsic value of ∼5000 to about 11 in the range of magnetic field amplitude and frequency values relevant to HT. The power generated by the seed dropped sharply as the shell thickness deviated from the optimal value. The optimized TB and HT-only seeds generated 45 and 267 mW power, respectively, providing a HT source sufficient for >90% volume coverage even for the highest blood perfusion rates. The toxicity of the surrounding normal tissues was minimal due to the rapid temperature fall off within a few millimeters distance from aseed. The investigated TB and HT-only seed prototypes were shown to provide sufficient power for the concurrent administration of radiation and HT. In addition to being used as a source for both radiation and heat at the onset of cancer therapy, these implanted seeds would be available for treatment intensification in the setting of salvage brachytherapy for locally radiorecurrent disease, possibly as a sensitizer to systemic therapies or as a modulator of the immune response, without another invasive procedure. Experimentally determined parameters of the ferrite material cores provided in this study establish a mechanistic foundation for future pre-clinical and clinical validationstudies.

Time-dependent and spatio-temporal statistical analysis of seismicity: application on the complete data set of the 2010 Beni–Ilmane earthquake sequence

SUMMARY The Beni–Ilmane (BI) seismic sequence, situated in the north-central region of Algeria, began on 2010 May 14 with a main shock of ML 5.4 followed by two other shocks on May 16 and 23 of ML 5.3 for both. Using the complete data set from May 14 to August 31 and the Epidemic Type Aftershock Sequences (ETAS) model to separate background from aftershocks contribution gave a first insight around the uncertainty that surrounds the causes and mechanisms of the seismicity. According to our findings, two phases have been determined, the first one, beginning from May 14, shows low b- and p-values with most of the seismicity being self-triggered. In contrast, the second phase, beginning from May 23, demonstrates an increase of both the b- and p-values with a high number of background events. In the second phase, the background contribution involves 53 per cent of all seismic activity after May 23’s peak which is high compared to typical main shock–aftershocks sequences. A possible explanation is that the main shocks began or assisted aseismic processes in addition to causing aftershocks. A sealed source at depth may have been broken by the third main shock, opening the way for the following incursion of highly pressurized fluids (hydrocarbures) confirmed by a high Vp/Vs ratios.

Fabrication and characterization of sealed source scandium-46 (46Sc) for industrial gamma scanning applications

Fabrication and characterization of sealed source scandium-46 (46Sc) for industrial gamma scanning applications

Preparation and evaluation of mixed gamma sealed source for calibration purpose

Preparation and evaluation of mixed gamma sealed source for calibration purpose

Monte Carlo simulation of a simple and fast method to experimentally determine the partial sensitivity of a bare LR-115 detector using planar alpha sources

Partial sensitivity of the bare LR-115 detector (KB) to radon or thoron, or any of their airborne progeny, is an essential component in the detector's calibration factor. Its experimental determination is complex, requires expensive and sophisticated instruments and facilities, and is time consuming. Using the TRACK_TEST and SRIM programs, and Monte Carlo simulations, the possibility of a simple and fast method to determine KB experimentally was demonstrated. The method is based on calculations of the average value of detection efficiencies (i.e., the cumulative efficiency) for alpha particles emitted by a planar alpha source placed at different distances from detectors. Source radius can be estimated from the energy of emitted alpha particles, detector radius, and parameters dependent on etching conditions. Varying the emission energy of alpha particles, the source and detector radii, and the source-detector distance step length, an average value of 0.02 tracks. cm−2 per Bq.d.m−3 (0.22 cm) was obtained assuming standard etching conditions. In addition to alpha electrodeposited sources, sealed sources such as those built with anodized aluminium sheets proved to be suitable for this proposal. Experimentally, KB can be estimated from: track densities registered in detectors exposed at different distances from the source, range of distances that produce visible tracks, and source activity. The developed method is much simpler and faster than the conventional method that uses standard sources of radon and its progeny and large chamber with controlled conditions.

Compact Back-End Electronics with Temperature Compensation and Efficient Data Management for In Situ SiPM-Based Radiation Detection.

A compact back-end interface for silicon photomultipliers (SiPMs) implementing Zener diode-based temperature compensation has been developed for the remote detection of beta and gamma radiation. Remote detection is facilitated by the development of an efficient data management system utilising MySQL database storage for recording periodic spectra data for wireless access over a private Wi-Fi network. A trapezoidal peak shaping algorithm has been implemented on an FPGA for the continuous conversation of pulses from the SiPM, signifying the detection of a radiological particle, into spectra. This system has been designed to fit within a 46 mm cylindrical diameter for in situ characterization, and can be attached to one or more SiPMs used in conjunction with a range of scintillators. LED blink tests have been used to optimise the trapezoidal shaper coefficients to maximise the resolution of the recorded spectra. Experiments with an array of SiPMs integrated with a NaI(Tl) scintillator exposed to sealed sources of Co-60, Cs-137, Na-22 and Am-241 have shown that the detector achieves a peak efficiency of 27.09 ± 0.13% for a gamma peak at 59.54 keV produced by Am-241, and a minimum energy resolution (Delta E/E) of 4.27 ± 1.16% for the 1332.5 keV gamma peak from Co-60.

X-ray diffraction line profile analysis for the detection of the propensity to sensitize

Prior studies have revealed that the sensitization kinetics of 5xxx-series Al-Mg alloys are responsive to the dislocation content, with lower dislocation densities leading to higher rates of sensitization. In this work, X-ray line profile analysis (LPA) was employed to non-destructively assess the dislocation density in 5083 and 5456 alloys samples in various tempers and thermomechanical processing states. Using a conventional laboratory powder diffractometer with a Cu-Kα sealed tube source, it is shown that the approach has the ability to discriminate between samples of disparate tempers (H131, H116, and solutionized and water quenched). Destructive electron backscattered diffraction (EBSD) measurements on select samples confirm the variations, from the perspective of geometrically necessary dislocation density. Experiments were also performed using softer X-rays generated using a Cr Kα sealed tube source, which would render the approach more portable, due to lower shielding requirements. Unfortunately, Cr radiation was not successful due to the limited number of accessible diffraction peaks. Using the dislocations densities measured using LPA together with an established constitutive model permits accurate prediction of the mechanical strength of the alloys of the above disparate tempers. However, the technique does not appear capable of discriminating between samples within a given temper (e.g., H116). Use of a more highly monochromatic X-ray source could render the technique useful for a comprehensive structural health monitoring system for 5xxx alloys prone to sensitization.