Naturally Occurring Radioactive Materials Research Articles

Study of aluminothermic slag leaching for uranium and thorium recovery

The need for energy by modern society is increasing. On the other hand, it is necessary to reduce costs and environmental impact. In this perspective, the recovery of uranium present in industrial waste from the processing of naturally occurring radioactive material (NORM) appears as a possible complement to the mining stage of the Nuclear Fuel Cycle. NORM's uranium recovery can reduce environmental liabilities and mineral processing costs (especially blasting, crushing, and grinding). The industrial residue of this study, a type of aluminothermic slag, comes from the metallurgical processing of columbite (niobium and tantalum mineral) and has a content, measured by X-ray fluorescence, of 1.78% of U3O8. This content is higher, for example than those found in Lagoa Real-BA (0.2% in rock) and Santa Quitéria-CE (0.1% in rock). Another material that will be studied is ThO2, which is also present in the slag with a content, measured by X-ray fluorescence, around 3.66%. The process parameters analyzed were pH of the solution, time, granulometry and percentage of solids. The metallurgical recovery of U3O8 reached a maximum value of 71,3% with pH = 1, time of 8 hours, 65 % percentage of solids, and 200 µm of granulometry. The metallurgical recovery of ThO2 reached a maximum value of 69,7% with pH = 1, time of 8 hours, 65 % percentage of solids, and 200 µm of granulometry.

The behavior of the 210Pb during the recycling of selected waste in the metallurgical industry

Contemporary trends in the metal industry are based on zero-waste and a closed circular economy. Such an approach has encouraged the industry to search for new methods of metal production using unconventional sources of them instead of high-priced raw materials. Waste from some industry sectors e.g. residues, slag, stack dust, etc. may be a economically interesting input material for other sectors of industry. There are at least two benefits reusing waste in such a way – the reduction of disposal costs and reduction of the environmental and health impact of industry. However, industrial waste or by-products are often classed as naturally occurring radioactive materials (NORM). The behavior of a lead isotope 210Pb – a naturally occurring radioactive nuclide - was investigated in this work. The analyzed metallurgical process is based on the recycling of waste from niobium and tantalum production, which were then used in tin and lead production. Behavior of 210Pb in particular stages of a process may lead to the enrichment of this radionuclide in the final product – distilled lead. The concentrations of 210Pb in the input material, final product as well as generated by-products and waste were determined.

Laboratory and pilot plant scale study on the removal of radium, manganese and iron from drinking water using hydrous manganese oxide slurry

The presence of naturally occurring radionuclides in drinking water can pose health risks to consumers. Processes of radionuclides removal could result in the accumulation of radioactive elements in a treatment facility, e.g. in filter materials, causing the formation of naturally occurring radioactive materials (NORM). Development of water treatment solutions mostly puts the emphasis on radionuclide removal leaving the generation of (NORM) out of focus. To meet current radiation protection standards, a broader view is necessary - water purification from radionuclides is an optimization assignment between radionuclide removal and accumulation rates. In this work, the injection of HMO slurry into the raw water was tested for simultaneous reduction of the radium, iron, and manganese. Experiments were performed in a lab scale setup and then upscaled to a pilot plant. Laboratory study allowed to optimize the sequence of water treatment steps. The pilot plant was operated over the course of two years demonstrating the removal of Fe and Mn from water as high as 97% and 83%, respectively. The optimal dose of HMO for radium isotopes removal was found to be 1.3 gMnO2·m−3. At this dose the concentrations of Ra-226 and Ra-228 were reduced from 0.358 and 0.470 to 0.048 and 0.043 Bq·L−1, respectively. Thereupon, radionuclides content in drinking water was decreased far below the parametric value of 0.1 mSv·year−1. In terms of NORM generation, the studied approach enabled to slow down the accumulation of radionuclides in the filter material prolonging its operation cycle.

Development of a computer code for the calculation of self-absorption correction factors in γ-spectrometry applications

In γ-spectroscopy applications, one of the main effects that needs to be considered is the self absorption of the photons – especially of low energy – within the photon source, which may be significantly different between the calibration standard and the sample analyzed. This effect is highly dependent on material composition and density and sample thickness. A common way of dealing with the self-absorption issue is by using Efficiency Correction Factors (ECF), to take into consideration the different absorbing properties between the calibration standard and the sample. This work presents the on-going development of a MATLAB code for ECF calculation. The code calculates ECF for a variety of material matrices and compositions, focusing on Naturally Occurring Radioactive Materials (NORM), which may have high density and contain high Z elements. The results of the code were compared with other methods of ECF calculation, such as Monte-Carlo simulation.

Evaluation of radioactivity concentration of some selected mineral rocks from Mayo-Belwa Local Government Area of Adamawa State, Nigeria

Radiation from natural sources is constantly present around people and their surroundings. Natural Occurring Radioactive Materials (NORM) present in rock, soil and underground water are the major sources of this radiation. In this study, radioactivity concentration of 238U, 232Th, and 40K from Ten (10) different Granite (GN), Gneiss (GS), and Migmatite (MG) rocks samples obtained from Mayo Belwa Local Government Area of Adamawa State were evaluated using a well calibrated and shielded Canberra 3 x 3 inch NaI(Tl) detector at the National Institute of Radiation Protection and Research (NIRPR), University of Ibadan. Rock samples were cleaned, pulverised and placed in the detector for counting, and based on standard expressions, the radionuclide content of the granite rock samples were evaluated. The result shows that the activity concentration of 238U, 232Th, and 40K in GN samples varies from 62.44 – 117.67 Bq/kg, 76.59 – 165.58 Bq/kg, and 688.03 – 1472.42 Bq/kg with corresponding mean of 74.59 ± 3.12, 104.41 ± 3.12, and 950.16 ± 3.12 Bq/kg. Activity concentration of 238U, 232Th, and 40K in GS samples ranges from 19.23 – 36.49 Bq/kg, 29.06 – 49.42 Bq/kg, and 310 – 924.21 Bq/kg with corresponding mean of 28.1 ± 5.36Bq/kg, 38.92 ± 6.38 Bq/kg, and 664.21 ±178.14 Bq/kg. Activity concentration of 238U, 232Th, and 40K in MG samples ranges from 32.11 – 74.73 Bq/kg, 40.79 – 105.87 Bq/kg, and 453.34 – 1040.77 Bq/kg with corresponding mean of 50.19 ± 14.35 Bq/kg, 60.50 ± 19.96 Bq/kg, and 714.88 ± 200.37 Bq/kg. The mean activity from this study are higher than the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) global mean of 238U (32 Bq/kg), 232Th (45 Bq/kg), and 40K (420 Bq/kg) in soil and rock samples except for 238U and 232Th in GS samples which are lower than the recommended standards. The results signifies that usage of such rocks as building construction raw materials might pose radiological hazards in the long run. Therefore, mineral content of the rock responsible for the high radionuclide concentration should be investigated.

In Situ Determination of Radioactivity Levels and Radiological Doses in and around the Gold Mine Tailing Dams, Gauteng Province, South Africa

The mining and processing of naturally occurring radioactive materials (NORMs) could result in elevated levels of natural radionuclides in the environment. The gold mining in the goldfields of the Witwatersrand Basin of South Africa has resulted in numerous tailing dams that have high concentrations of NORM bearing residue. The aim of this study was to evaluate the radioactivity levels in tailing dams, soils and rocks, and the consequential radiological exposure to the public in the gold mining areas of Gauteng Province, South Africa. The activity concentrations of 238U, 232Th, and 40K were assessed using a gamma ray spectrometer (RS-230), and the activity concentrations ranges in the mine tailings were 209.95–2578.68 Bq/kg, 19.49–108.00 Bq/kg, and 31.30–626.00 Bq/kg, respectively. The radionuclides show significant spatial variability in soils, with high activities recorded in soils located in close proximity to tailings although regionally, the soil radioactivity levels mainly depend on the chemistry of the underlying rocks. The estimated annual effective doses were higher than the recommended regulatory limit of 0.25 mSv/y in particular tailing dams and soil impacted by tailings. Therefore, to ensure the protection of people and the environment, further monitoring and regulatory control measures targeting these areas are required.

Radiation hazard assessments of natural radioactivity in clay-based cosmetic products in Malaysia

Natural sources such as clays, plant extracts, and raw materials containing naturally occurring radioactive material (NORM) have been used as ingredients for medicinal and cosmetic purposes since ancient times. Nowadays, a variety of commercially available cosmetics products used clay minerals containing NORMs as the main formulation, which poses unknown radiation risks to the consumer. In this study, 11 samples of clay-based cosmetic products were used to conduct dose assessments on members of the public for various usage scenarios to evaluate the external exposure dose. Gamma-ray spectroscopy was utilised to measure the activity concentrations of 238U, 232Th, and 40K in the sample. Meanwhile, doses to skin and other organs from these cosmetic products were modelled using Geant4 Monte Carlo simulations and the MIRD5 mathematical phantom, incorporating dose conversion factors (DCFs). The results revealed that the activity concentration for 238U, 232Th, and 40K ranged from 0.1 – 1.3, 0.06–15.6, and 0.22–6.9 Bq g−1, respectively, which were lower than the reference provided by the international regulation. The analysis for heavy metals showed that sample 9 contained a high amount of Cd, which gave an immediate alert to that particular product. Furthermore, the effective doses in the skin estimated in this study with the range of 2.7–240 μSv y−1, were significantly lower than the International Commission on Radiological Protection (ICRP) reference limit of 50 mSv per year for members of the general public. Based on the few μSv of effective dose exposure, it is sufficient to conclude that the dose from these products poses no radiological risk to the user. The addition of NORMs in cosmetic products should be done with caution because higher concentrations can raise the dose.

Inventory of Occupational Risk from Natural Occurring Radioactive Materials (NORMs) in Soil Samples of the Coastal Region of Nigeria After Six Decades of Oil and Gas Exploration

Inventory of Occupational Risk from Natural Occurring Radioactive Materials (NORMs) in Soil Samples of the Coastal Region of Nigeria After Six Decades of Oil and Gas Exploration

A review of current inventory for major industries involving naturally occurring radioactive materials in Canada

Earth materials contain radionuclides of natural origin in varying concentrations. Exposure to natural sources dominates the occupational and public exposure to ionizing radiation. Canada has one of the largest and most diverse supplies of natural resources in the world. A large quantity of material production is associated with a large quantity of waste releases to the environment. Releases from industries involving naturally occurring radioactive material (NORM) can concentrate trace amounts of natural radionuclides and are often poorly characterized. This raises concerns for occupational and public health. Currently, there are data and knowledge gaps in radiological characteristics of NORM products and waste or releases to the environment. For the evaluation of occupational and public exposure to natural sources, a review of current inventory for major industries involving NORM in Canada was conducted with the objective to provide basic information on major issues, help set the priority for research needs to filling these data and knowledge gaps.

Radiological Atmospheric Risk Modelling of NORM Repositories in Hungary

The human population is continuously exposed to natural radionuclides in environmental elements. The concentration of these nuclides is usually low, but different technological processes and activities can concentrate them in products, by-products, or wastes. These activities are, for example, coal mining, fertilizer production, ore mining, metal production, etc. These materials are labelled as NORM (Naturally Occurring Radioactive Material). The most common method of disposal for NORMs is deposition in different types of depositories. The long-term effects of these depositories on the environment and on human health are hard to estimate. The aim of the study is to assess radiation risk from the five selected NORM depositories (Ajka coal ash, Ajka red mud, Almásfüzitő red mud, Zalatárnok drilling mud, and Úrkút manganese residue) for members of the public and biota. The radionuclide concentrations were determined by HPGe gamma-spectrometry. The measured concentration was between 31 Bq/kg and 1997 Bq/kg for Ra-226, between 33 Bq/kg and 283 Bq/kg for Th-232, and between 48 Bq/kg and 607 Bq/kg for K-40. The dose estimation was investigated using RESRAD-ONSITE and RESRAD BIOTA, which are computer codes developed by the Argonne National Laboratory (USA). RESRAD-ONSITE can estimate the radiation risk from the radionuclides in the contaminated sites. The highest dose was observed in the case of the Ajka coal ash depository–without cover (12.38 mSv/y), and the lowest was in the case of Zalatárnok (0.53 mSv/y). The most significant contributors to the population dose are the uptakes through plants and external pathways, which account for more than 80% of the total dose on average. RESRAD-BIOTA code was used to estimate the radiation exposure of terrestrial organisms (plants and animals). During this work, the values of sum ratio factor (SRF), biota concentration guide (BCG), external dose, internal dose, and total dose were determined.

Assessing the need for radiation protection measures in artisanal and small scale mining of tantalite in Oke-Ogun, Oyo State, Nigeria

There is concern that work scenarios on the tantalite mining sites in Oke-Ogun, Oyo State, Nigeria may cause occupational radiation exposure of workers due to enhanced concentrations of naturally occurring radionuclides in some process materials. A prior radiological assessment of the mining activities was carried out to determine if and which exposure scenarios may require radiation protection measures. Samples of the materials involved, comprising tantalite (tantalum ores), soil and waste rock were collected and analyzed for activity concentrations of 40K, 226Ra, 238U and 232Th using a hyper pure germanium detector gamma-ray spectrometer. Radon concentrations in the mines were also measured using a continuous radon monitor - Radon-Scout Plus (Sarad, GmbH). Activity concentrations of 40K are below 10 Bqg-1 in all the samples but all the tantalite samples contain more than 1 Bqg-1 of 226Ra and 238U. Hence tantalite is regarded as naturally occurring radioactive material (NORM) and the mining activity as a practice. The requirements for planned exposure situations apply to all the mining sites but, on the basis of graded approach, the optimum radiation protection measures vary from one mine to another, ranging from exemption to authorization. Exposures to radon in the underground mines pose the greatest radiological risks and portend the greatest need for regulatory control in the mining operations. The results further underscore the need to integrate radiation protection with the other health and safety measures in the mining sector.

Radiological risk assessment to marine biota from exposure to NORM from a decommissioned offshore oil and gas pipeline

Scale residues can accumulate on the interior surfaces of subsea petroleum pipes and may incorporate naturally occurring radioactive materials (NORM). The persistent nature of ‘NORM scale’ may result in a radiological dose to the organisms living on or near intact pipelines. Following a scenario of in-situ decommissioning of a subsea pipeline, marine organisms occupying the exteriors or interiors of petroleum structures may have close contact with the scale or other NORM-associated contaminated substances and suffer subsequent radiological effects. This case study used radiological dose modelling software, including the ERICA Tool (v2.0), MicroShield® Pro and mathematical equations, to estimate the likely radiological doses and risks of effects from NORM-contaminated scale to marine biota from a decommissioned offshore oil and gas pipeline. Using activity concentrations of NORM (226Ra, 210Po, 210Pb, 228Ra, 228Th) from a subsea pipeline from Australia, environmental realistic exposure scenarios including radiological exposures from both an intact pipe (external only; accounting for radiation shielding by a cylindrical carbon steel pipe) and a decommissioned pipeline with corrosive breakthrough (resulting in both internal and external radiological exposure) were simulated to estimate doses to model marine organisms. Predicted dose rates for both the external only exposure (ranging from 26 μGy/h to 33 μGy/h) and a corroded pipeline (ranging from 300 μGy/h to 16,000 μGy/h) exceeded screening levels for radiological doses to environmental receptors. The study highlighted the importance of using scale-specific solubility data (i.e., Kd) values for individual NORM radionuclides for ERICA assessments. This study provides an approach for conducting marine organism dose assessments for NORM-contaminated subsea pipelines and highlights scientific gaps required to undertake risk assessments necessary to inform infrastructure decommissioning planning.

Automation and Closed-Loop Systems Reduce HSE Risks

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31985, “Reducing HSE Risks Through Automation and Closed-Loop Systems,” by Simon Smith, Olof Nilsson, SPE, and Aksel Skåland, SPE, FourPhase. The paper has not been peer reviewed. Copyright 2022 Offshore Technology Conference. Reproduced by permission. Solids production in produced fluids is an industrywide challenge, incurring major costs to operators through lost production, asset integrity, and well-intervention campaigns. The complete paper highlights solids-management technologies that are currently available and still in use topside (and some of which are potentially outdated). It also identifies the amount of exposure to hazardous byproducts of produced oil and gas from these various technologies. The complete paper also presents a new-technology case study and compares this with legacy methods and practices in terms of health, safety, and environment (HSE) risk and cost. Naturally Occurring Radioactive Materials (NORM) NORM can be divided into sources that originate from the ground and those produced from the interaction of atmospheric gases with cosmic rays. The risks associated with NORM, and the solutions available to manage those risks, are not widely known in the industry. The complete paper focuses on 3 NORM, which originate from the ground. The paper further details the characteristics of benzene and hydrogen sulfide, two other hazardous materials often encountered in solids-handling within the industry. NORM Hazards. - The hazardous elements found in NORM are radionuclides such as radium 226 and 228, radon 222, and daughter products from these radionuclides. The concentration of radium and other daughter products builds up in the body over time. The elements can migrate to bone tissue and concentrate, causing bone cancers, lymphoma, leukemia, and other serious medical conditions. Employers should always prioritize minimization of exposure of their offshore personnel. NORM in the Oil and Gas Industry. - Scale may build up over time from naturally occurring radium and its daughter products in wellbores, pipes, and vessels. Isotopes build and radiate differently depending on the reservoir rock and salinity of the well. Because a correlation usually exists between the age of a well and salinity (which increases with age), old wells seem to carry higher NORM levels than younger wells.

REVIEW OF NORM DISTRIBUTION AND BEHAVIORS IN PRODUCED WATER FROM OILFIELD INDUSTRIES

According to the noteworthy concentration of naturally occurring radioactive material (NORM), produced water that is considered a damaging waste resulting from the oil extraction process according to the noteworthy concentration of naturally occurring radioactive material (NORM), is regularly disposed into nearby areas, resulting in environmental contamination that raises the possibility of human exposure NORM in various pathways. This paper purposes to provide an extensive examination of the NORM reported in produced water linked with oilfield activities from previous reports. The comparison of NORM values in oilfields around the world demonstrates a vivid understanding of radionuclide behaviors associated with oil extraction operations. The results illustrate that Radium isotopes are the most radionuclides abundant in produced water, especially Radium-226, activity concentrations of U-238 and Th-232 were remarkable to be low in the water. Oil extraction is increasing, leading to more produced water being disposed of, which is a real concern for human health, so a depth study is recommended to focus on minimization and other management methods of produced water instead of being disposed of. Furthermore, the NORM waste and its influence could be minimized by obeying the recommended standard set by IAEA and other environmental protection agencies.

Activity concentrations and radiation hazard in the soil of Ashaka Cement PLC Gombe state, Nigeria with a multivariate statistical approach

Humans are exposed externally and internally in their environment to natural background radiation from radionuclides such as 40K, 238, U and 232Th which emit gamma, alpha, beta and other forms of radiation through their decay processes. These radionuclides are found in the soil, food and the water we consume. Human activities such as the mining of uranium, oil exploration, building materials, coal-fired power station can ignite the Naturally Occurring Radioactive Materials (NORMs). The aim was to assess radiation impact in Ashaka cement factory, Gombe state for their potential radiological hazards in order to maintain a safe environment. A prospective cross-sectional survey design was adopted and using a purposive sampling technique, fifteen (15) soil samples were collected using a geographical positioning system (GPS). The activity concentrations of these natural radionuclides were measured due to Gamma radiation by using a High Purity Germanium detector. Samples were analysed at the Radiation Protection Institute of Ghana Atomic Energy Commission, Kwanbeya District, at Accra, Ghana. Fifteen (15) soil samples were collected from within the Ashaka Cement factory (Zone 1) and environment (Zone 2). Data was analyzed by the use of SPSS Version 22.0 (IBM Corp. Armonk NY, 2011). Descriptive statistics was employed to obtain the Mean and Standard deviation of the radioactivity concentrations. Inferential statistics was carried out to compare the radionuclides and radiological parameters. Statistical significance was considered at p ≤ 0.05. The mean activity concentrations of 238U, 232Th and 40K in soil samples at Zone 1 are 42.70 Bqkg-1, 29.00 Bqkg-1, 375 Bqkg-1 and Zone 2 is 46.11 Bqkg-1, 35.00 Bqkg-1, 780.30 Bqkg-1respectively. Radiation hazard indices at Zone 1 and 2 shows the mean for External Hazard index, Internal Hazard index, Gamma Index, External Absorbed Dose Rate, Annual Effective Does Rate, External Annual Effective Does Rate, Excess Lifetime Cancer Risk and Annual Gonadal Effective Dose is 0.31, 0.42, 0.83, 38.80nGyh-1, 0.32x10-3, 0.048mSvyr-1, 0.17mSvyr-1, 371mSvyr-1 and 0.42, 0.55, 1.18, 45.70nGyhr-1, 0.46mSvyr-1, 0.056mSvyr-1, 0.20x10-3, 533.80mSvyr-1 respectively. This implies that both staffs and members of the public in the factory might be at risk due to cumulative effect of radiation exposure high activity concentration from 238U and Annual Gonal effective dose exceeding the world average limits.

Shale gas wastewater characterization: Comprehensive detection, evaluation of valuable metals, and environmental risks of heavy metals and radionuclides

Shale gas wastewater (SGW) has great potential for the recovery of valuable elements, but it also poses risks in terms of environmental pollution, with heavy metals and naturally occurring radioactive materials (NORM) being of major concerns. However, many of these species have not been fully determined. For the first time, we identify the elements present in SGW from the Sichuan Basin and consequently draw a comprehensive periodic table, including 71 elements in 15 IUPAC groups. Based on it, we analyze the elements possessing recycling opportunities or with risk potentials. Most of the metal elements in SGW exist at very low concentrations (< 0.2 mg/L), including rare earth elements, revealing poor economic feasibility for recovery. However, salts, strontium (Sr), lithium (Li), and gallium (Ga) are in higher concentrations and have impressive market demands, hence great potential to be recovered. As for environmental burdens related to raw SGW management, salinity, F, Cl, Br, NO3−, Ba, B, and Fe, Cu, As, Mn, V, and Mo pose relatively higher threats in view of the concentrations and toxicity. The radioactivity is also much higher than the safety range, with the gross α activity and gross β activity in SGW ranging from 3.71–83.4 Bq/L, and 1.62–18.7 Bq/L, respectively and radium-226 as the main component. The advanced combined process “pretreatment-disk tube reverse osmosis (DTRO)” with pilot-scale is evaluated for the safe reuse of SGW. This process has high efficiency in the removal of metals and total radioactivity. However, the gross α activity of the effluent (1.3 Bq/L) is slightly higher than the standard for discharge (1 Bq/L), which is thus associated with potential long-term environmental hazards.

External dose assessment of NORM added consumer products using Geant4 Monte Carlo simulations

Radioactive consumer products (RCP) are widely marketed for everyday use. The study herein was conducted on 21 commercially available RCP, including bio-glass discs, energy cards, scalar energy products, and anti-radiation stickers, all purposefully designed to contain naturally occurring radioactive material (NORM). This study investigates the dose influence of such consumer products which acts as external radiation sources that may be in contact with human body. The goal of this study is to assess the potential risk of using NORM-added consumer products, the presence of such products in the living environment unnecessarily exposing members of the public to radiation. A Pb-shielded high purity Ge (HPGe) spectrometer was used to perform the analysis of samples radioactivity levels. Simulations were performed using Geant4 Monte Carlo (GMC) simulations to estimate the equivalent organ doses and annual effective dose (AED) in the use of such products. The total activity in such radioactive consumer products ranges from 2.0 ± 0.1 to 7413 ± 576 Bq, 1.9 ± 0.8 to 1168 ± 131 Bq, and 21 ± 5–574 ± 103 Bq, for 232Th, 238U, and 4 K, respectively. It was found that RCP contains monazite, giving a relatively high concentration of uranium and thorium. The radiological risk posed by the use of such items as healthcare products is assessed, with the daily external exposure doses of particular concern. Dose assessments of the organ equivalent and average effective doses were performed by measuring the activity of 232Th, 238U, and 4 K using the aforementioned products for various exposure duration scenarios. Accordingly, sample A13 a bio-glass disc offered concentrations with mean percentages of 1.29 ± 0.003% and 0.043 ± 0.0003% for Th and U, respectively, giving rise to estimate the greatest annual effective dose exposure of 2.54 mSv among samples, considerably in excess of the public dose limit of 1 mSv y-1

A Practical Procedure to Determine Natural Radionuclides in Solid Materials from Mining

There are many regulations related to the radiological control of NORMs (Naturally Occurring Radioactive Materials) in activities such as mining, industry, etc. Consequently, it is necessary to apply fast and accurate methods to measure the activity concentrations of long-lived natural radionuclides (e.g., 238U, 234,232,230,228Th, 228,226Ra, 210Pb, 210Po, and 40K) in samples characterized by a wide variety of compositions and densities, such as mining samples (wastes, minerals, and scales). Thus, it is relevant to calculate the radioactive index (RI), which summarizes for all radionuclides the ratio between the activity concentration and its respective threshold activity concentration as established by regulations, in order to classify a material as a NORM. To proceed with the determinations of these radionuclides, two spectrometric techniques based on both alpha-particle and gamma-ray detections should be employed. In the case of gamma-ray spectrometry, it is necessary to correct the full-energy peak efficiency (FEPE) obtained for the calibration sample, εc, due to self-attenuation and true coincidence summing (TCS) effects. The correction is especially significant at low gamma emission energies, that is, Eγ &lt; 150 keV, such as 46 keV (210Pb) and 63 keV (234Th). On the other hand, in samples which contain radionuclides that are in secular disequilibrium with others belonging to the same series (238U or 232Th series), like wastes or intermediate products, it is necessary to measure some pure-alpha emitters (232Th, 230Th, 210Po) by employing alpha-particle spectrometry. A practical and general validated procedure based on both alpha and gamma spectrometric techniques and using semiconductor detectors is presented in this study.

Estimation of public radiological dose from mining activities in some selected cities in Nigeria

Mining activities is one of the most significant sources of radiation exposure from long-lived naturally occurring radioactive materials (NORMs), and have resulted in unjustifiable public exposure doses which contravene radiation protection standards. As a result, estimating the extent of such exposure is essential for keeping the recommended public dose limit. This study therefore aims at estimating the public radiation dose around mining areas and its environs in some selected cities across Nigeria. Data on measured activity concentration of NORMs radionuclides comprising of U-238, Ra-226, Th-232 and K-40 from soil round mining areas in some selected cities in Nigeria were extracted from previous literatures and are used for public dose estimation using RESRAD computer code. From the calculated mean activity concentration, the results from each mining locations shows the maximum dose are lower than International Commission on Radiological Protection (ICRP), commended public dosage boundary of 1 mSv/yr with highest dose of 0.91 mSv/yr from Ra-226, Th-232 and K-40 over the period of 47.9 years reported from Gura Top mining site in Jos, Plateau State, while the lowest dose of 0.09 mSv/yr each over the period of 14.06 and 20.27 years occurred at Itagunmodi and Arufu sites for U-238, Th-232 and K-40. The highest dose recorded in Gura Top was due to numerous mining activities in the region. According to the ICRP, there is no safe level of radiation exposure. Therefore, there is need for competent authorities to conduct periodic assessment of radiation exposure from mining sites to ensure that all exposure emanating as a result of such activities are kept below the prescribed dose limit in accordance to the principle of As Low As Reasonably Achievable (ALARA), thereby ensuring public protection from unjustified radiation exposure.

Recycle Glass Waste as a Host for Solidification of Oil Sludge

The production of oil sludge per year is more than 1 billion tonne that mainly generated from the production, refinery, storage, and transportation of petroleum. Disposal of oil sludge had been a great issue since the waste consists of highly concentrated of Natural Occurring Radioactive Material (NORM). Therefore, to overcome this problem, this study aims to investigate used and recycle borosilicate glass as a host for solidification of oil sludge. The oil sludge and glass host were mixed into different compositions, melted at high temperature (1,100 °C -1,200 °C) for 1 h in alumina crucible and rapidly cooling in the room temperature, by reducing the radioactivity levels of NORM. This study found out that, the optimum waste loading was obtained at a range of 20-25 wt% of oil sludge and 75-80 wt% of the glass host at 1,200 °C. All the glass waste was produced as an amorphous phase material with small amount of crystalline phase such as SiO2, Ba4-Al2-O7, AlPO4, Al2O3 and Fe3Zn10, which observed to be appeared during the cooling process. The major elements of the glass waste were found to be distributed uniformly based on energy dispersive X-ray spectroscopy (EDX) mapping. Furthermore, the dissolution rate of indicator element increased due to the increase of pH solution, while the normalized releases of B, Si, and Na during product consistency tests were low and below the standard glass limit, which shows high durability of the glass due to lower release of glass elements. Therefore, this study emphasized the suitability of recycle borosilicate glass as a host for immobilization of oil sludge prior for disposal, while deploying high temperature technology.