Orphan Source Research Articles

Discovering an Orphan Source of Ionizing Radiation with Respect to Occupational Safety and Health

Compliance with the principles of occupational safety and health is one of the preconditions for avoiding emergency events. Without a doubt, this is one of the underlying duties of every employer or operator of waste recycling centers. The risk to health resulting from an orphan source of ionizing radiation in the form of scrap metal is quite high and can affect a significant number of people. As part of the precautions relating to employees, the employer must analyze the risks associated with working with scrap metal and emphasize the possibility of any previous contamination. In practice, various methods and procedures are used to assess the risks at scrap metal collection facilities, which are mostly based on the knowledge and experience of their inspectors. However, this is not usually done by means of appropriate risk analysis methods, which is the main disadvantage. The goal of this article is to point at the risks related to discovering an orphan source of ionizing radiation by using the Ishikawa diagram and the point method. Furthermore, this article also deals with the demarcation of a safety zone with respect to the protection of health and the environment. The specification of risks, the proposal of recommended precautions, and the expeditious demarcation of a safety zone in the case of the intervention of fire brigades in order to protect and/or decontaminate the persons are also included. Doi: 10.28991/CEJ-2022-08-11-013 Full Text: PDF

Accuracy of a Bayesian technique to estimate position and activity of orphan gamma-ray sources by mobile gamma spectrometry: Influence of imprecisions in positioning systems and computational approximations.

The purpose of this study was to investigate the effects of experimental data on performance of a developed Bayesian algorithm tailored for orphan source search, estimating which parameters affect the accuracy of the algorithm. The algorithm can estimate the position and activity of a gamma-ray point source from experimental mobile gamma spectrometry data. Bayesian estimates were made for source position and activity using mobile gamma spectrometry data obtained from one 123% HPGe detector and two 4-l NaI(Tl) detectors, considering angular variations in counting efficiency for each detector. The data were obtained while driving at 50 km/h speed past the sources using 1 s acquisition interval in the detectors. It was found that deviations in the recorded coordinates of the measurements can potentially increase the uncertainty in the position of the source 2 to 3 times and slightly decrease the activity estimations by about 7%. Due to the various sources of uncertainty affecting the experimental data, the maximum predicted relative deviations of the activity and position of the source remained about 30% regardless of the signal-to-noise ratio of the data. It was also found for the used vehicle speed of 50 km/h and 1 s acquisition time, that if the distance to the source is greater than the distance travelled by the detector during the acquisition time, it is possible to use point approximations of the count-rate function in the Bayesian likelihood with minimal deviations from the integrated estimates of the count-rate function. This approximation reduces the computational demands of the algorithm increasing the potential for applying this method in real-time orphan source search missions.

An internet of radiation sensor system (IoRSS) to detect radioactive sources out of regulatory control

A radioactive source that is not under regulatory control, either because it has never been under regulatory control or because it has been abandoned, lost, misplaced, stolen, or otherwise transferred without proper authorization, is considered an orphan source. Orphan sources are usually gathered as scrap metal because of their heavy metallic containers. Melting an orphan source with scrap metal produces contaminated recycled metal and waste; the consequences will be extremely serious for humans and the environment, affecting the economy and social stability. In this paper, we propose and develop an Internet of Radiation Sensor System (IoRSS) to detect radioactive sources out of regulatory control in scrap metal recycling and production facilities. It is a complete IoT system consisting of a network of wirelessly connected radiometric devices that optimizes the detection, localization, and identification of radioactive sources by integrating data from multiple portable radiation detectors. The proposed IoRSS system creates a robust and flexible network architecture along with advanced data fusion algorithms that combine information from many detectors. The IoRSS system provides advanced search and monitoring capabilities in a large coverage area and in difficult operational environments.

An IoT System for Radioactive Material Detection in Scrap Metal Recycling and Production Facilities

A radioactive source that is not under regulatory control because it is abandoned, lost, misplaced, stolen, or transferred without proper authorization is referred to as an orphan source. The melting of an orphan source, when mixed with scrap metal, has resulted in contaminated recycled metal and wastes and the consequences will be very serious for humans and the environment. In this paper, we propose and develop an Internet of Radiation Sensor System (IoRSS) to enhance the use of nuclear detection systems to detect nuclear and other radioactive materials out of regulatory control at points of entry/exit and other trade locations of scrap metal recycling and production facilities. The proposed IoRSS creates a robust and flexible network architecture along with advanced data fusion algorithms that combine information from many detectors. The test results show that the IoRSS system allows for accurate detection of radioactive sources and provides appropriate radiation incident response plans.

Identification and assessment of occupational safety risks in case of failure to capture an orphan source of ionizing radiation

Occupational safety and health belong to fundamental human rights. This fully applies to the protection of employees and other persons, which operate or are located in facilities for the collection of scrap metal. The founder of the landfill or the employer has an irreplaceable place in the field of protection of persons against the effects of ionizing radiation. Based on the identification and assessment of occupational safety risks in the event of failure to ensure timely detection of an orphan source of ionizing radiation, the operator must assess all risk factors with emphasis on radiation. At the same time, it must take specific regime measures, which would minimize the impact on people and the environment. The article deals with the causes of failure the system of protection against the effects of ionizing radiation. The assessment of these causes is performed using the fault tree analysis method with the application of Boolean equations. The result of solving the problem is the calculation of the failure of the regime protection system in the devices, intended for the collection of scrap metal, caused by human error as a result of intentional or negligent actions of the operator and insufficient training in the areas of control of measuring devices, principles of correct use of detection devices, insufficient visual identification of potentially dangerous objects. The contribution of this paper is in the design of appropriate regime measures eliminating the consequences of non-capturing a source of ionizing radiation.

Activity estimation of shielded gamma-ray source by measuring the single compton scattering count

During a routine inspection of radioactive sources or orphan source disposal, it is essential to effectively and rapidly estimate the activity of the radioactive source. However, this estimation may be difficult, especially when the source is shielded and the shield thickness is unknown. In this paper, a new method is developed to estimate the activity of radioactive sources under shields of unknown thickness based on the ratio of the full-energy peak count (FEPC) to the single Compton scattering count (SCSC). The proposed method is evaluated by experiments, and the results show that the proposed method can obtain a relative error of thickness of less than 7% and a relative error of source activity of less than 28%, which indicate that the method can be used to efficiently estimate the activity of radioactive sources under different shields.

Mayapuri Radiological Catastrophe: Good Practices and the Lessons Learnt.

Advances in the peaceful applications of ionizing radiation have brought in its wake the inevitable concern about radioactivity. Almost a decade ago, an infamous unprecedented radiological exposure incident occurred in Delhi, which has not only some positive aspects for imbibing good practices to emulate but also lessons learnt to further improvise the overall management, respectively. The Mayapuri incident at Delhi exposed the lack of awareness and laxity on the part of University of Delhi authorities in disposing of the Cobalt Irradiator, and the further insecure handling of the orphan radioactive source. Since an occurrence like this was unparalleled, it was necessary to flag all interlinked issues and put in place a technology management system that should address them. The methodology includes an in-depth discussion about the good practices and lessons learnt of the then-existing techno-legal systems and the response mechanism to the Mayapuri radiological incident from various departments of repute, both governmental as well as non-governmental. The present article attempts to intensify pragmatic approaches to proactively avert and thwart 'orphan source' incidents like the Mayapuri radiological incident, so that threat to the society is minimal, and putting in place enhanced medical preparedness measures for the management of radiation casualties caused by ignorance, negligence, incompetence, accident, or malicious intention.

Lesson learned from the recovery of an orphan source inside a maritime cargo: analysis of the nuclear instrumentations used, and measures realized during the operations

In this paper, the authors analyze the case study of the recovery of an orphan source of 60Co inside a maritime cargo full of metal wastes in the Italian Harbor of Genova carried out by the Italian Fire Fighters. Orphan radioactive sources or Radiological Dispersal Devices are a critical security issue in large geographical areas, and they result in a safety concern for people who may become accidentally exposed to ionizing radiation. The abandonment of orphan sources can usually be related to three factors: human errors, cost reasons (in order to avoid the payment of disposal procedures), or malevolent purposes (like the production of dirty bombs). The present data concern the nuclear safety measures implemented during the recovery event and the pool of procedures carried out in order to reduce the risks for the involved harbor operators. Following data collection and analysis, an important lesson about the management of such events and scenarios can be learned.

Developing an Integrated Nuclear Waste Management Strategies on Aggregate Orphan Source Radioactive Materials in the Oil and Gas Sector.

Orphan sourced radioactive waste materials associated with oil and gas exploration, exploitation and production have been identified as causal factors in environmental health risks of operation personnel and the host communities in the Niger Delta. These Technologically Enhanced Radionuclides such as 14C, 40K, 87Rb, 232Th, 288U and some low frequency radioactive heavy metals constitute potential dangers to environmental health assay. Highly Sensitive Radiation Detection Tracers (HSRDT) were deployed for tracking and analysis of ionized leakages in the coastal marine offshore and shallow offshore areas in in a typical deltaic region. The inverse determination technique of the generalized half-life period was integrated into the model equations 1 – 12. Table 1 is a survey from 1992 t0 2015, showing that some identified radionuclides are reactive and contaminants to the surrounding environment from oil and gas processes. However, inadequate strategic decommissioning activities are responsible for severe occupational and environmental hazards to flora and fauna. This paper is fundamental to developing an integrated orphan waste management system as remedial techniques to minimize radiation waste burns and other harmful environmental effects on personnel and the environment. Its application is useful for decision-making on radioactive waste material management strategy. Furthermore, possible conceptual legal framework and standards for the disposal system of orphan sourced radionuclides in the petroleum sector could be explored. Keywords: Radioactive Waste Materials; Aggregate Orphan–Sourced Radionuclides; Environment Management; Waste Disposal Systems; Oil and Gas Sector etc.

Development of a high-precision gamma-ray source finder based on a single detector

In this research, the conceptual design of an orphan gamma-ray finder based on a single NaI(Tl) scintillation detector in energy range of ∼50 keV to ∼3 MeV using Monte Carlo (MCNPX2.6) code has been presented. In the conventional finders, usually 2, 3 or more detectors are used. First, the system including three 2-in. NaI(Tl) scintillation detectors has been investigated. Based on the results, a newer approach to find the angular position of γ-ray orphan source for the system including only one 2-in. NaI(Tl) scintillation detector has been proposed. The height difference between an orphan source’s position and central axis of detector will decrease the precision of determining spatial location as well as activity calculation of the source. In this research, 3D localization of an orphan γ-ray source in a limited space using an electromechanical motorized laboratory jack has been enabled. This system can determine location and activity of an orphan source in distances of 2.0 m to 10.0 m from center of this system with activity of 3.77 × 106 Bq with relative errors less than 3% and 6%, respectively.

Monte Carlo and experimental analysis of a novel directional rotating scatter mask gamma detection system

Abstract For such diverse applications as on-site radiation monitoring, treaty or material verification, cargo monitoring during transport, and orphan source location a radioactive source localization system is of great use. The Rotating Scatter Mask (RSM) detection system, a rapid scatter mask retrofit to a conventional radiation detector, provides a low-cost, large field of view and energy range solution to this problem. This work demonstrates successful experimental operation of a prototype system to identify source direction which was modeled using a library of signals simulated using GEANT and a novel algorithm, validated by comparing results with MCNP and experiment.

A Bayesian method to localize lost gamma sources

A feasibility study of a Bayesian based algorithm for orphan source localization by means of mobile gamma spectrometry is presented. The method was tested on three types of gamma sources (137Cs, 133Ba and 131I) using a HPGe detector mounted on a vehicle. Estimates on source activity and source locations were within 51% and 29% of actual values, respectively. Further studies are required to validate and develop this method for additional source-detector configurations and gamma radiation background conditions.

Public Health Emergency Response for the Detection of a Radioactive Orphan Source in a Public Park in Toshima Ward, Tokyo

Public Health Emergency Response for the Detection of a Radioactive Orphan Source in a Public Park in Toshima Ward, Tokyo

A Rotating Scatter Mask for Inexpensive Gamma-Ray Imaging in Orphan Source Search: Simulation Results

The Rotating Scatter Mask (RSM) system is an inexpensive retrofit that provides imaging capabilities to scintillating detectors. Unlike traditional collimator systems that primarily absorb photons in order to form an image, this system primarily scatters the photons. Over a single rotation, there is a unique, smooth response curve for each defined source position. Testing was conducted using MCNPX simulations. Image reconstruction was performed using a chi-squared reconstruction technique. A simulated 100 uCi, Cs-137 source at 10 meters was detected after a single, 50-second rotation when a uniform terrestrial background was present. A Cs-137 extended source was also tested. The RSM field-of-view is 360 degrees azimuthally as well as 54 degrees above and 54 degrees below the horizontal plane. Since the RSM is built from polyethylene, the overall cost and weight of the system is low. The system was designed to search for lost or stolen radioactive material, also known as the orphan source problem.

On background radiation gradients – the use of airborne surveys when searching for orphan sources using mobile gamma-ray spectrometry

Systematic background radiation variations can lead to both false positives and failures to detect an orphan source when searching using car-borne mobile gamma-ray spectrometry. The stochastic variation at each point is well described by Poisson statistics, but when moving in a background radiation gradient the mean count rate will continually change, leading to inaccurate background estimations. Airborne gamma spectrometry (AGS) surveys conducted on the national level, usually in connection to mineral exploration, exist in many countries. These data hold information about the background radiation gradients which could be used at the ground level.This article describes a method that aims to incorporate the systematic as well as stochastic variations of the background radiation. We introduce a weighted moving average where the weights are calculated from existing AGS data, supplied by the Geological Survey of Sweden. To test the method we chose an area with strong background gradients, especially in the thorium component. Within the area we identified two roads which pass through the high-variability locations. The proposed method is compared with an unweighted moving average. The results show that the weighting reduces the excess false positives in the positive background gradients without introducing an excess of failures to detect a source during passage in negative gradients.

Angular resolution study of a combined gamma-neutron coded aperture imager for standoff detection

Nuclear threat source observables at standoff distances of tens of meters from mCi class sources include both gamma-rays and neutrons. This work uses simulations to investigate the effects of the angular resolution of a mobile gamma-ray and neutron coded aperture imaging system upon orphan source detection significance and specificity. The design requires maintaining high sensitivity and specificity while keeping the system size as compact as possible to reduce weight, footprint, and cost. A mixture of inorganic and organic scintillators was considered in the detector plane for high sensitivity to both gamma-rays and fast neutrons. For gamma-rays (100 to 2500keV) and fission spectrum neutrons, angular resolutions of 1–9° and radiation angles of incidence appropriate for mobile search were evaluated. Detection significance for gamma-rays considers those events that contribute to the photopeak of the image pixel corresponding the orphan source location. For detection of fission spectrum neutrons, energy depositions above a set pulse shape discrimination threshold were tallied. The results show that the expected detection significance for the system at an angular resolution of 1° is significantly lower compared to its detection significance an angular resolution of ∼3–4°. An angular resolution of ∼3–4° is recommended both for better detection significance and improved false alarm rate, considering that finer angular resolution does not result in improved background rejection when the coded aperture method is used. Instead, over-pixelating the search space may result in an unacceptably high false alarm rate.

Maximum detector sizes required for orphan source detection

Orphan source detection is hampered by fluctuations in the natural background. These fluctuations act as systematic errors that limit the effectiveness of large detectors during a search. Large detectors just map background variations more accurately, while small detectors are dominated by counting-statistics errors. This suggests that there is a maximum effective size for a search detector that occurs approximately where the two variances are equal.

Too many notes?

Orphan sources are now recognized as a radiation protection problem needing attention. Government and private sector initiatives have been mounted in response. Should more be done? There are promising possibilities. Under the ICRP 60 system of radiation protection, any use of radiation should be justified. Key NRC licensing regulations predate ICRP 60 and, consequently, if a use is authorized by license, then the use is presumed to be justified even if alternatives are available. As an example, x-ray gauges can be successfully substituted for nuclear container fill level gauges in the food and beverage industry. But this development is not widely known to potential users and regulators, and current regulatory policies do not address this. Limiting the number of radioactive devices would limit the number of potential orphan sources. From an operational radiation safety point of view, persons wanting to dispose of unneeded or unwanted radioactive sources are faced with a system loaded with disincentives, in part because disposition options are not well known and in part because options have become limited, complex, and expensive. New approaches are needed if the orphan source problem is to be effectively addressed. Paramount are the needs to (1) update U.S. regulatory policies to incorporate the ICRP principle of justification, (2) create a system that encourages prompt, safe dispositioning of unneeded and unwanted radioactive sources, and (3) make information on these points universally known to users of radioactive sources.