State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios

In the last decade, the development of more compact and lightweight radiation detection systems led to their application in handheld and small unmanned systems, particularly air-based platforms. Examples of improvements are: the use of silicon photomultiplier-based scintillators, new scintillating crystals, compact dual-mode detectors (gamma/neutron), data fusion, mobile sensor networks, cooperative detection and search. Gamma cameras and dual-particle cameras are increasingly being used for source location. This study reviews and discusses the research advancements in the field of gamma-ray and neutron measurements using mobile radiation detection systems since the Fukushima nuclear accident. Four scenarios are considered: radiological and nuclear accidents and emergencies; illicit traffic of special nuclear materials and radioactive materials; nuclear, accelerator, targets, and irradiation facilities; and naturally occurring radioactive materials monitoring-related activities. The work presented in this paper aims to: compile and review information on the radiation detection systems, contextual sensors and platforms used for each scenario; assess their advantages and limitations, looking prospectively to new research and challenges in the field; and support the decision making of national radioprotection agencies and response teams in respect to adequate detection system for each scenario. For that, an extensive literature review was conducted.

An Easily Integrable Industrial System for Gamma Spectroscopic Analysis and Traceability of Stones and Building Materials

In the building material and stones market, lots of restrictions are coming in different world zones. In Europe, a recent regulatory set up the maximum level of radiological emissions for materials intended for use in public and private building structures. For this reason, companies need to have a very efficient radiological measurements system in their production chain, in order to respect all the rules and to be competitive in the world market. This article describes CORSAIR, a Cloud-Oriented Measurement System for Radiological Investigation and Traceability of Stones. Our cyber-physical system consists of sensing nodes network connected to a data collection gateway through LoRaWAN protocol, and interfaces with a centralized cloud application. CORSAIR introduces a fast, repeatable, real-time and non-destructive method to measure radiological emissions and other parameters of each single building material item, uniquely identified by an applied RFID tag. The validity of this system is confirmed by in-situ measurement campaign compared with high-precision laboratory analysis. The results demonstrate the accuracy of the CORSAIR sensor and the possibility to easily integrate it in the company production chain without any change.

226Ra, 210Po and lead isotopes in a pit lake water profile in Sweden

A pit lake arises as a consequence of anthropogenic activities in opencast mining areas. These water bodies may be enriched in hazardous stable contaminants and/or in naturally occurring radionuclides depending on the local geological conditions. Mining legacy in Sweden produced hundreds of these pit lakes and most of them are used for recreational purposes in the southern part of the country. In this paper, one pit lake was selected for having enhanced levels of natural radionuclides. Physico-chemical parameters (temperature, pH, oxidation-reduction potential, dissolved oxygen and depth), elemental composition (via Inductive Coupled Plasma Mass Spectrometry) and radiometric characterization (via alpha spectrometry of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb) were carried along the depth of a 60 m depth pit lake, with the main aim to describe how natural radionuclides and elements behaves with depth in a non-uraniferous pit lake. Based on observed changes in physico-chemical parameters, a thermocline and a chemocline region were identified at around 10 and 30 m depth respectively. Concerning radionuclides, ²²⁶Ra ranged from 75 ± 3 up to 360 ± 12 mBq/kg while ²¹⁰Po ranged from 11 ± 1 up to 71 ± 3 mBq/kg. ²¹⁰Pb distribution with depth was also determined via secular equilibrium with ²¹⁰Po after 2 years and also stable Pb was measured. Disequilibrium ²²⁶Ra-²¹⁰Pb was found and the residence time of ²¹⁰Pb in the water column was assessed. Additionally, different vertical distributions between ²¹⁰Pb and Pb were found which points out different sources for different lead isotopes in the water body.

Modification of natural radionuclide uptake by wheat using a NORM by-product as soil amendment

Drinking Water Treatment Plants (DWTPs) can be optimised for removal of natural radionuclides, thus meeting EU legislation. Removed radionuclides (^234,238U, ²²⁶Ra and ²¹⁰Po) go into sludges. What would happen if these sludges were used in agriculture? Wheat plantlets were cultivated in original and sludge-amended soils under laboratory controlled conditions. Soil-to plant transfer was significantly increased in factors ranging 1.2-3.7, 2.0-5.6, and 1.6-2.4 for ^234,238U, ²²⁶Ra and ²¹⁰Po, respectively. The additional input was preferentially accumulated in roots.

A rapid method to determine 226Ra concentrations in Marcellus Shale produced waters using liquid scintillation counting

Concentrations of naturally occurring radioactive material (NORM) in Marcellus Shale produced water presents a challenge for effective management and treatment, because of the vast fluid volumes generated. With an increased emphasis on beneficial reuse and resource recovery from the produced waters, a rapid, yet reliable, method for quantifying radium in these produced waters is needed. The high total dissolved solids (TDS) concentration introduces difficulties when measuring ²²⁶Ra by recommended EPA methods that were specifically developed several decades ago for drinking water. While other techniques for measuring radium in these high-TDS fluids have since been developed, these newer techniques often require extensive and complicated pre-concentration steps; and they thus require extensive analytical chemistry skills, utilize hazardous chemicals like hydrofluoric acid, demand long holding times or measurement times, and require high sample volumes. We present a rapid method for ²²⁶Ra measurements in high-TDS produced waters by liquid scintillation counting, which has been corroborated herein by concurrent gamma spectrometry analyses. Samples were prepared for analysis by evaporating the fluid and re-suspending the evaporate with acidified distilled deionized water prior to liquid scintillation counting for 1 h. This protocol yielded radium recoveries ≥93%. Per this protocol, the alpha and beta spectra of ²²⁶Ra and its daughters were computationally separated by alpha-beta discrimination and spectrum deconvolution. The minimum detectable activities of ²²⁶Ra was 0.33 Bq/L (9.0 pCi/L) when the counting time was 60 min and the sample volume was 4 mL. Nine produced waters of varying TDS and radium concentrations from the Marcellus Shale Formation were analyzed by this method and compared with gamma spectroscopy; and these yielded comparable results with an R² of 0.92. The reduced sample preparation steps, low cost, and rapid analysis position this as a well-suited protocol for field-appraisal and screening, when compared to comprehensive radiochemical analysis. We offer that for a given produced water region, routine and local liquid scintillation analyses can be compared and calibrated with infrequent gamma spec analyses, so as to yield a near-real time protocol for monitoring ²²⁶Ra levels during hydrofracturing operations. We present this as a pragmatic and efficient protocol for monitoring ²²⁶Ra when produced water samples host low levels of ²²⁸Ra-since the progeny of ²²⁸Ra can significantly confound the LSC analyses.

Micro-analytical characterization of thorium-rich aggregates from Norwegian NORM sites (Fen Complex, Telemark)

In this study we performed microscopic characterization of mineral particles that were collected in the thorium-rich Fen Complex in Norway and identified and isolated based on autoradiography in function of their radioactivity. For this we combined information obtained with X-ray absorption μ-CT, μ-XRF and μ-XRD, both in bi- and in three-dimensional (tomographic) mode. We demonstrate that radionuclides and metals are heterogeneously distributed both within soil samples and within individual Th-enriched aggregates, which are characterised as low-density mineral bulk particles with high density material inclusions, where Th as well as several metals are highly concentrated. For these sites, it is important to take into account how these inhomogeneous distributions could affect the overall environmental behaviour of Th and progeny upon weathering due to human or environmental factors. Moreover, the estimated size of the Th-containing inclusions as determined in this work represents information of importance for the characterization of radionuclides and toxic metals exposure, as well as for assessing the viability of mining for Th and rare-earth metals in the Fen Complex and the associated environmental impact.

Radon-222 diffusion length and exhalation characteristics of uraniferous waste rock and application to mine site remediation in the Australian wet-dry tropics

The diffusion length of ²²²Rn in uraniferous waste rock was determined through a novel experiment. Large PVC columns were filled to different depths in the range from 0.5 m to 3.0 m with waste rock material from the Ranger uranium mine and the build-up of ²²²Rn activity concentration in the column headspace above the material was measured after closing the columns with a lid. Measurements were made approximately one month after filling the columns and again after approximately one and two years. The average ²²²Rn diffusion length derived from the measurements was 1.9 ± 0.2 m in the dry material. The corresponding diffusion coefficient was (7.3 ± 0.7) × 10^-6 m² s^-1. For an infinitely thick layer of the dry material, the average value of the ²²²Rn exhalation flux density relative to the ²²⁶Ra activity concentration was estimated as (5.3 ± 0.3) × 10^-4 Bq m^-2 s^-1 per Bq kg^-1. From the diffusion length, the waste rock material was characterised as both a source and attenuator of ²²²Rn for its proposed use as the surface cover on the final landform of the remediated Ranger uranium mine.

Distribution of uranium and thorium chains radionuclides in different fractions of phosphogypsum grains

This work presents results obtained using gamma spectrometry measurements of phosphogypsum samples on a non-fractionated (native) and fractionated phosphogypsum byproduct. The phosphogypsum was divided into particles size fractions within the range of < 0.063, 0.063-0.090, 0.090-0.125, 0.125-0.250, and over 0.250 mm and analyzed after reaching radioactive equilibrium using high-resolution gamma spectrometry technique. It was found that there is no significant differentiation between ²²⁶Ra distribution among particular grain size fractions of this material; however, tendency for preferential retention of radionuclides in particular grain size fractions is observed. The detailed analysis of results revealed that radium is preferentially retained in smaller grain size fractions, whereas lead and thorium in coarse fractions. The results indicate that overall ²²⁶Ra activity concentrations between particular fractions of phosphogypsum vary globally between - 34 and + 47% regarding non-fractionated material, and for ²¹⁰Pb activity concentration, fluctuations are found between - 26 up and + 38%. Presumably, the mechanism of radium incorporation into gypsum phase is based on a sequence of radium bearing sulfate phases formation followed by a surface adsorption of these phases on the calcium sulfate crystals, whereas for lead and thorium ions, rather incorporation into crystal lattice should be expected as more likelihood process.

Method development for rapid quantification of Rn-222 in surface water and groundwater

Understanding the risks of a developing unconventional hydrocarbons industry, including shale gas, to the chemical quality of surface water and groundwater involves firstly establishing baseline compositions against which any future changes can be assessed. Contaminants of geogenic origin are of particular interest and radon has been identified as one potential contaminant from shale sources. Robust measurement and monitoring of radon in water at environmental concentrations is essential for ensuring protection of water sources and maintaining public confidence. Traditional techniques for Rn-222 determination in water, such as inference by gamma spectrometry and direct alpha counting, are impractical for direct field measurement, and the relatively short half-life of Rn-222 (~ 3.82 days) means that longer analytical protocols from field to the laboratory may result in greater uncertainty for Rn-222 activity. Therefore, a rapid and low-cost method would be beneficial. We have developed and refined a laboratory procedure for Rn-222 monitoring using liquid scintillation counting (LSC). The accuracy of Rn-222 activities obtained via this procedure was evaluated by the analysis of almost 200 water samples collected from streams and boreholes as part of a detailed baseline investigation in the Vale of Pickering, Yorkshire, one potential location for future shale gas exploration. LSC was preferred for measurement of Rn-222 and had comparable accuracy to gamma spectrometry and direct alpha counting. The methodology provided a rapid, portable and low-maintenance option relative to the two established techniques and is shown to be a favourable choice for the measurement of radon in surface water and groundwater at environmental concentrations.

Performance Analysis of Geiger-Müller and Cadmium Zinc Telluride Sensors Envisaging Airborne Radiological Monitoring in NORM Sites

Radiological monitoring is fundamental for compliance with radiological protection policies in the aftermath of radiological events, such as nuclear accidents, terrorism, and out-of-commission uranium mines. An effective strategy for radiation monitoring is to use radiation detectors coupled with Unmanned Aerial Vehicles (UAVs), enabling for quicker surveillance of large areas without involving the need of human presence in the target area. The main aim of this study was to formulate the parameters for a UAV flight strategy in preparation for future field measurements using Geiger-Muller Counters (GMC) and Cadmium Zinc Telluride (CZT) spectrometers. As a proof of concept, the prepared flight strategy will be used to survey out-of-commission uranium mines in northern Portugal. Procedures to assure the calibration of the CZT and verification of the GMCs were conducted, as well as a sensitivity analysis of the sensors considering different acquisition times, distance to source, and detector response time. This article reports specific parameters, such as UAV distance to ground, time of exposition, speed, and the methodology to perform the identification and calculate the activity of possible radioactive sources. An effective flight strategy is also presented, aiming to use radiation detectors coupled with UAVs to undertake extensive monitoring of areas with enhanced levels of environmental radiation, which is of prime importance due to the lasting hazardous effects of enhanced environmental radiation in the nearby ecosystem and population.

Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia

Recognizing the vast uses of water in human life, the presence of α and β particles emitting radionuclides in groundwater of northern Saudi Arabia has been evaluated as a means of water quality assessment of the region. A liquid scintillation counting technique was used to determine the gross α/β, and ²²⁸Ra radioactivities in water samples, while the radioactivity concentrations of ^234,238U and ²²⁶Ra were determined using alpha spectrometry after the separation process. Present results show that all water samples contain a higher level of gross α and β radioactivity than the WHO recommended limits; the average gross α activity is about 7 times greater than the limit value of 0.5 Bq L^-1, while the average gross β activity value is about 3.5 times greater than the limit value of 1 Bq L^-1. Correlations of TDS and pH with gross α and β radioactivity in the studied samples were investigated. The activity ratio of the measured U and Ra alpha emitters to the gross α radioactivity and the ratio of the measured β emitters to gross β radioactivity were also discussed. Furthermore, interesting information on thorium abundance and radioactive disequilibrium in U series were observed by studying the activity ratio of ²²⁸Ra/²²⁶Ra, ²²⁶Ra/²³⁸U, and ²³⁴U/²³⁸U. Although these samples are not directly used for human being drinking, and mainly used in irrigation, the higher gross α/β radioactivity may cause health risks to humans, since these radionuclides may enter the food chain through irrigation water. Thus, further radioactive risk assessment is highly recommended.

Radiometrical and physico-chemical characterisation of contaminated glass waste from a glass dump in Sweden

Around former glass factories in south eastern Sweden, there are dozens of dumps whose radioactivity and physico-chemical properties were not investigated previously. Thus, radiometric and physico-chemical characteristics of waste at Madesjö glass dump were studied to evaluate pre-recycling storage requirements and potential radiological and environmental risks. The material was sieved, hand-sorted, leached and scanned with X-Ray Fluorescence (XRF). External dose rates and activity concentrations of Naturally Occurring Radioactive Materials from ²³⁸U, ²³²Th series and ⁴⁰K were also measured coupled with a radiological risk assessment. Results showed that the waste was 95% glass and dominated by fine fractions (<11.3 mm) at 43.6%. The fine fraction had pH 7.8, 2.6% moisture content, 123 mg kg^-1 Total Dissolved Solids, 37.2 mg kg^-1 Dissolved Organic Carbon and 10.5 mg kg^-1 fluorides. Compared with Swedish EPA guidelines, the elements As, Cd, Pb and Zn were in hazardous concentrations while Pb leached more than the limits for inert and non-hazardous wastes. With ⁴⁰K activity concentration up to 3000 Bq kg^-1, enhanced external dose rates of ⁴⁰K were established (0.20 μSv h^-1) although no radiological risk was found since both External Hazard Index (H_ex) and Gamma Index (I_γ) were <1. The glass dump needs remediation and storage of the waste materials under a safe hazardous waste class 'Bank Account' storage cell as a secondary resource for potential future recycling.

Evaluation of Scintillator Detection Materials for Application within Airborne Environmental Radiation Monitoring

In response to the Fukushima Daiichi Nuclear Power Plant accident, there has occurred the unabated growth in the number of airborne platforms developed to perform radiation mapping-each utilising various designs of a low-altitude uncrewed aerial vehicle. Alongside the associated advancements in the airborne system transporting the radiation detection payload, from the earliest radiological analyses performed using gas-filled Geiger-Muller tube detectors, modern radiation detection and mapping platforms are now based near-exclusively on solid-state scintillator detectors. With numerous varieties of such light-emitting crystalline materials now in existence, this combined desk and computational modelling study sought to evaluate the best-available detector material compatible with the requirements for low-altitude autonomous radiation detection, localisation and subsequent high spatial-resolution mapping of both naturally occurring and anthropogenically-derived radionuclides. The ideal geometry of such detector materials is also evaluated. While NaI and CsI (both elementally doped) are (and will likely remain) the mainstays of radiation detection, LaBr₃ scintillation detectors were determined to possess not only a greater sensitivity to incident gamma-ray radiation, but also a far superior spectral (energy) resolution over existing and other potentially deployable detector materials. Combined with their current competitive cost, an array of three such composition cylindrical detectors were determined to provide the best means of detecting and discriminating the various incident gamma-rays.

Evaluation of the annual effective dose due to the external irradiation induced by using NORM added consumer products

This study aims to evaluate the annual effective dose from a sleeping mattress containing naturally occurring radioactive material (NORM). In this study, the dose rate was measured using two different portable radiation detectors, namely the Geiger Müller (GM) tube and portable high-purity germanium (HPGe) detector; the annual effective dose was calculated using annualized usage of the products, and the equivalent does was evaluated via Monte Carlo (MC) simulation and using the model of the human body, which is known as a computational human phantom. The dose rate of the product, excluding background radiation at the shielded room, was measured as 0.22 and 0.13 μSv/h in the GM-tube and portable HPGe, respectively. Assuming that the sleeping mattress was used for an average sleeping of 8 h/day, the annual effective dose was calculated as 0.64 and 0.38 mSv/y using the GM-tube and portable HPGe detectors, respectively. Also, the annual effective dose calculated using MC simulation and radioactivity values from the nuclides analysis was 0.13 mSv/y. The annual effective dose calculated using the two different portable detectors and MC simulation is less than the annual effective dose limit for the general public, which is set at 1 mSv/y. This technique could be used not only for the safety regulation for products containing NORM but also for the accurate evaluation of the effective dose for radiation workers in the diverse radiation field.

Establishment of a NORM baseline for selected seafood in the Gulf of Mexico

Naturally occurring radioactive material was characterized in selected seafood samples from three areas in the Gulf of Mexico. Relatively desirable and abundant fish such as Red Snapper, Red Drum, Northern Whiting, and Spotted Trout as well as oysters were collected and analyzed using gamma spectroscopy to determine the concentration of ²²⁸Ra, ²²⁶Ra, and ⁴⁰K. Average total activity concentration from these radionuclides were 0.9 ± 0.6, 1.6 ± 1.2, and 132 ± 57 Bq kg^-1 respectively, in the edible portion of wet weight samples. The results were consistent with previous studies for other bodies of water. A small but statistically significant increase in ²²⁶Ra was found in comparison to similar research performed 20 years prior. These measurements provide a reasonable baseline for the examined species from the Gulf of Mexico.

Toward the Optimization of Dinitrosyl Iron Complexes as Therapeutics for Smooth Muscle Cells

In this study, dinitrosyl iron complexes (DNICs) are shown to deliver nitric oxide (NO) into the cytosol of vascular smooth muscle cells (SMCs), which play a major role in vascular relaxation and contraction. Malfunction of SMCs can lead to hypertension, asthma, and erectile dysfunction, among other disorders. For comparison of the five DNIC derivatives, the following protocols were examined: (a) the Griess assay to detect nitrite (derived from NO conversion) in the absence and presence of SMCs; (b) the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 H-tetrazolium (MTS) assay for cell viability; (c) an immunotoxicity assay to establish if DNICs stimulate immune response; and (d) a fluorometric assay to detect intracellular NO from treatment with DNICs. Dimeric Roussin's red ester (RRE)-type {Fe(NO)₂}⁹ complexes containing phenylthiolate bridges, [(μ-SPh)Fe(NO)₂]₂ or SPhRRE, were found to deliver NO with the lowest effect on cell toxicity (i.e., highest IC₅₀). In contrast, the RRE-DNIC with the biocompatible thioglucose moiety, [(μ-SGlu)Fe(NO)₂]₂ (SGlu = 1-thio-β-d-glucose tetraacetate) or SGluRRE, delivered a higher concentration of NO to the cytosol of SMCs with a 10-fold decrease in IC₅₀. Additionally, monomeric DNICs stabilized by a bulky N-heterocyclic carbene (NHC), namely, 1,3-bis(2,4,6-trimethylphenyl)imidazolidene (IMes), were synthesized and yielded the DNIC complexes SGluNHC, [IMes(SGlu)Fe(NO)₂], and SPhNHC, [IMes(SPh)Fe(NO)₂]. These oxidized {Fe(NO)₂}⁹ NHC DNICs have an IC₅₀ of ∼7 μM; however, the NHC-based complexes did not transfer NO into the SMC. Per contra, the reduced, mononuclear {Fe(NO)₂}¹⁰ neocuproine-based DNIC, neoDNIC, depressed the viability of the SMCs, as well as generated an increase of intracellular NO. Regardless of the coordination environment or oxidation state, all DNICs showed a dinitrosyl iron unit (DNIU)-dependent increase in viability. This study demonstrates a structure-function relationship between the DNIU coordination environment and the efficacy of the DNIC treatments.

Modelling the dispersion of radionuclides in dust from a landform covered by low uranium grade waste rock

The dispersion of radionuclides in dust and inhalation dose rates to the public from the planned remediation of the Ranger uranium mine in the wet-dry tropics of Australia was modelled using RESRAD-OFFSITE. Dust inhalation dose rates were predicted to be highest on the remediated site and decrease with an approximate inverse square to inverse cubic dependence with distance from the site. The annual dose above natural background to a hypothetical individual permanently occupying the remediated site (representing the worst case scenario for radionuclide in dust exposure) was estimated to be 5.3 × 10^-3 mSv. The estimated doses from exposure to radionuclides in dust were two to three orders of magnitude lower than those from exposure to ²²²Rn. A sensitivity analysis showed that source-related and receptor-related model parameters had direct proportional influences on dust inhalation dose rates. Four transport-related model parameters (atmospheric stability class, deposition velocity of particulates, precipitation and wind speed) were also influential and generally had an increasing influence with distance from the source. The results of this study may provide general guidance to similar sites elsewhere on the relative importance of dust versus gaseous ²²²Rn transport pathways and the relative influence of dispersion modelling parameters on predicted exposures and doses.

Naturally occurring radioactive material and risk assessment of tailings of polymetallic and Ra/U mines from legacy sites

Old mine tailings from Northern and Central Portugal were studied in order to perform a radiological and chemical characterization. The evaluation of massic activity of natural radionuclides and concentrations in tailings of polymetallic and Ra/U mines was performed by gamma spectrometry and neutron activation analysis. Iron speciation was carried out by Mössbauer spectroscopy. In polymetallic tailings with physical ore processing (Cumieira and Verdes - exploited for Sn, Nb-Ta) higher contents of Th, ²²⁸Ra and ²²⁶Ra in the coarser materials occur, probably due to their presence in host rock and ore fragments. In finer tailings, washing may explain the lower ²²⁶Ra and ²¹⁰Pb massic activity. In tailings with physical/chemical ore processing (Covas - exploited for W and Sn) high U contents and a tendency for higher ²²⁶Ra and ²¹⁰Pb massic activity in the fine materials is observed, probably due to their incorporation in nano-sized particles of iron oxides. A high variation of the ²¹⁰Pb/²²⁶Ra ratio occurs in polymetallic tailings; a deficit of ²¹⁰Pb can be observed particularly in deposits of settling tanks drained from dumps of chemically treated ore. In Ervideira-Mestras tailings (Ra/U exploitation) where no ore process in situ was performed, a near equilibrium between ²¹⁰Pb and ²²⁶Ra occurs. Dose risk assessment was carried out by calculating external outdoor Annual Effective Dose Rate; the dose rates in air due to terrestrial gamma radiation are low for the polymetallic tailings (<47 nGy/h), and higher for tailings of Ra/U (up to 4130 nGy/h), in the worst scenario.

A practical approach to limit the radiation dose from building materials applied in dwellings, in compliance with the Euratom Basic Safety Standards

Individuals receive a significant part of their radiation exposure indoors. We anticipate that this exposure is likely to increase in the near future, due to a growing use in the building industry of recycled materials and materials previously regarded as waste. Such materials often contain elevated levels of natural radionuclides. Directive 2013/59/Euratom ('Basic Safety Standards', BSS) pays comprehensive attention to indoor exposure from natural radionuclides, but proper implementation of all corresponding BSS regulations is not straightforward, especially when regarding the regulation of building materials containing so-called Annex XIII materials. In this paper, we discuss the most relevant deficiencies in the BSS and present a practical approach to cope with these. Our most important observation is that adequate methods for assessing the annual dose due to gamma radiation from building materials are not provided by the BSS. This is in particular difficult because compliance of single building materials has to be tested, but the corresponding BSS reference level refers to gamma radiation emitted by all building materials present in a room. Based on a simple model of three layers of building materials, we present a set of operational conditions for building materials, either used for construction purposes ('bulk layers') or for the finishing of walls, floors and ceilings ('superficial layers'). Any customary combination of building materials meeting these conditions will stay below the BSS reference level for gamma radiation. This statement holds for the middle of a reference room, but is not always the case close to the walls, especially when low density materials with a relatively high content of natural radionuclides are present at the inner side of the room. This can be avoided by applying more strict conditions for those kind of materials than presented in this paper. We further focus on the indoor exposure to thoron progeny. Building materials that pass the test for gamma radiation can still be a significant source for indoor air concentrations of thoron progeny. When the average annual thoron inhalation dose were to be restricted to 1 mSv a^-1 - a level comparable to the BSS reference level for gamma radiation - the activity concentration of Ra-224 in (especially porous) building materials used for wall finishing purposes should be limited to a value of typically 50 Bq kg^-1. Even if our suggested approach of the BSS regulations is fully implemented, it still allows for a significant increase in the average radiation exposure in dwellings due to external radiation and thoron progeny. However, the situation will be worse if a less strict interpretation of the BSS regulations will be applied.

Modelling the dispersion of radon-222 from a landform covered by low uranium grade waste rock

The dispersion of ²²²Rn from the planned remediation of the Ranger U mine in the wet-dry tropics of Northern Australia was modelled. Dry and wet season contour maps of ²²²Rn dose normalised to ²²⁶Ra activity concentration in the proposed waste rock substrate on the remediated landform were developed. Three example exposure scenarios were assessed based on an anticipated waste rock ²²⁶Ra activity concentration of 800 Bq kg^-1. The estimated above-background annual dose from ²²²Rn to hypothetical receptors at the Aboriginal community at Mudginberri (∼10 km NNW) was 0.005 mSv and at the township of Jabiru (∼7 km W) was 0.033 mSv. The estimated above-background annual dose for the hypothetical worst case scenario, representing a receptor 1 km WNW of the landform centroid during the dry season and at the centroid during the wet season, was 0.13 mSv. Variability analysis on the 20 y meteorological dataset used in the dispersion modelling showed that the dry and wet season ²²²Rn dose predictions in any single year could be approximately double those of an average year, which suggests that estimates of average ²²²Rn dose should potentially be doubled if the assessment aim is to demonstrate compliance with the public dose limit.

Alpha emitter NORM crystal scales in industrial pipelines: A study case

Radioactive related pollution due to suspended particulate matter dispersion is an important workplace and health care issue. Recycling oil production ducts and contaminated production equipment, represent a health hazard to workers and public alike. Radioactive plate-out NORM scales with crystal deposit is analyzed by different techniques; results provide proper information on physico-chemical features and emitted alpha particles. Recommendations for handling and recycling procedures are included in relation to health risk and radiological hazard.

Grey monazite (rare earths) mining in centre of Spain: Characterization and pre-operational radiological evaluation

A radiological evaluation associated to the future mining of grey monazite nodules enriched in light rare-earths, from a modest superficial deposit located in the centre of Spain, has been performed at pre-operational level, and the main results are shown in this paper. Although the monazite nodules in the deposit are clearly enriched in radionuclides from the uranium and thorium series with activity concentrations higher than 1 Bq/g, the size of these nodules (in the 0.5 mm-2 mm grain size interval), its refractory behaviour that prevents the leaching or dissemination of natural radionuclides to waters or other ecosystem compartments and consequently the impact in the food chain, and its presence quite diluted in the deposit at concentrations of 2.5-3 kg/m³, conducted to conclude that pre-operationally the area to be mined for the extraction of the monazite is generating a negligible radiological impact in the public and the nearby environment. Additionally, the extraction of the raw material and the restoration of the area after mining (i.e. the mining activities which will be done in-situ, in the mining area) will be exempted of any radiological regulation attending to the European Union legislation being expected that will not generate a radiological impact.

Use of Genie 2000 and Excel VBA to correct for γ-ray interference in the determination of NORM building material activity concentrations

The γ-radiation emitted by building materials is calculated from the activity indices for ²³²Th, ²²⁶Ra and ⁴⁰K and expressed as the activity concentration index (ACI). Gamma spectroscopy is a non-destructive technique frequently used to simultaneously determine the indices for several radionuclides. Spectral interpretation poses a number of challenges, including identification of γ-lines subject to summing-in effects, interference from other γ-ray emitting radionuclides and the time required to reach secular equilibrium. These challenges are not fully addressed by Canberra Industries' Genie 2000, the software used by many laboratories to analyse samples. This article describes a Microsoft Excel workbook that exploits Genie 2000 flexibility to program applications with Visual Basic using Canberra's Nuclear Data Access Library and batch procedure tools. The workbook determines ⁴⁰K activity concentration after correcting for ²²⁸Ac interference and ²²⁶Ra activity directly from the γ-peak at 186.5 keV. The method proposed was tested by participating in 13 national and international scale inter-comparison exercises. The results were statistically indistinguishable from the reference values at a coverage factor of k = 3 and no statistically significant differences were identified between the respective means by a Student's t pairwise comparison.

Recovery of ilmenite mud as an additive in commercial Portland cements

This work is focused on the manufacture of commercial cement using as additive ilmenite mud, a waste generated during TiO₂ pigment production. The cements were produced by adding different proportions of mud (2.5, 5 and 10 wt%) to ordinary Portland cement (OPC). The ilmenite mud and the ilmenite mud cements (IMCs) were characterised physico-chemically by X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffraction (XRD). Moreover, the technological properties of the IMCs were evaluated and compared with a reference material (OPC). Since waste from the TiO₂ industry is classified as a NORM (naturally occurring radioactive material), the concentrations of radionuclides were measured by high-resolution low-background gamma and alpha spectrometry techniques. Finally, the TCLP leaching test (Toxicity Characteristic Leaching Procedure, USEPA), the radiological index ("I") and the Ra equivalent concentration were also calculated to evaluate the environmental risks. As a final conclusion, it can be pointed out that the addition of ilmenite mud to OPC plays a beneficial role since it reduces the heat of hydration, the final setting time, the expansion and the linear retraction compared to standard OPC. The compression strength improves with the addition of up to 5 wt% mud. Moreover, the environmental impact of IMC2.5 and IMC5 can be considered negligible.

Rapid in-situ radiometric assessment of the Mrima-Kiruku high background radiation anomaly complex of Kenya

This paper presents the radiometric survey results of the Mrima-Kiruku high background radiation (HBR) anomaly complex of south coastal Kenya. Utilizing a portable γ-ray spectrometer consisting of a 2.0 l NaI(Tl) backpack detector integrated with GPS to perform the relevant in-situ radiometric measurements, a novel geospatial gating method was devised to represent the measurements. The goal of this study was to assess radiation exposure and associated natural radioactivity levels in the complex and to compare the results obtained with those from previous preliminary related studies. Absorbed dose-rates in air were found to range <60-2368 nGy h^-1. These rates were observed to correspond with the spatial variability of the underlying geology and terrain, increasing toward the summits of both Mrima and Kiruku Hills which implies that the complex is a geogenic HBR anomaly. The activity concentrations of ²³²Th in the study area are generally higher than those of ⁴⁰K and ²³⁸U: The means of ⁴⁰K, ²³⁸U and ²³²Th ranged 235±19-603±28 Bq kg^-1, 68±6-326±24 Bq kg^-1 and 386±12-1817±51 Bq kg^-1 respectively. It was concluded that the high air absorbed dose-rate values that were measured (>600 nGy h^-1) are due to elevated activity concentrations of ²³²Th. Therefore there is significant (>1 mSv/y) radiological hazard to the inhabitants of the area particularly those who reside at the foothills of both Mrima and Kiruku Hills.