Anthropogenic radioactive particles in the environment

Radioactive particles have been released from multiple sources since the mid-twentieth century. Famous examples include nuclear fuel particles from Chernobyl, glassy microparticles from Fukushima as well as particles from nuclear weapons production facilities (e.g., Windscale, United Kingdom and the facilities in the former Soviet Union), nuclear weapons accidents at Palomares (Spain) and Thule (Greenland), and atmospheric nuclear explosions. Current challenges in environmental research of radioactive particles include the drying of the cooling pond of Chernobyl NPP, which will cause the weathering of previously preserved fuel particles in the (former) sediment of the pond. Environmental aspects of resuspended particles as well as natural particles and aerosols contaminated with radionuclides (e.g., ¹³¹I) are briefly discussed.     

Analysis of radioactive particles from the Kola Bay area

Two types of radioactive particle were identified in marine sediment and lichen samples collected from the Kola Bay, NW Russia. The particles were identified by means of gamma-ray spectrometry and autoradiography, separated and subjected to various analysis techniques. Several complementary techniques are needed to characterise particle properties thoroughly. 137Cs was present in the sediment matrix in large (approximately 100 microns) greenish particles that were most probably pieces of paint. Although their element composition was heterogeneous, 137Cs was found to be evenly distributed. 60Co in the lichen matrix was present in small (approximately 1 micron) particles. No U or transuranium elements were detected in either type of particle.     

The use of SIMS and SEM for the characterization of individual particles with a matrix originating from a nuclear weapon.

The application of scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) for characterization of mixed plutonium and uranium particles from nuclear weapons material is presented. The particles originated from the so-called Thule accident in Greenland in 1968. Morphological properties have been studied by SEM and two groups were identified: a "popcorn" structure and a spongy structure. The same technique, coupled with an energy-dispersive X-ray (EDX) spectrometer, showed a heterogeneous composition of Pu and U in the surface layers of the particles. The SIMS depth profiles revealed a varying isotopic composition indicating a heterogeneous mixture of Pu and U in the original nuclear weapons material itself. The depth distributions agree with synchrotron-radiation-based mu-XRF (X-ray fluorescence microprobe) measurements on the particle (Eriksson, M., Wegryzynek, D., Simon, R., & Chinea-Cano, E., in prep.) when a SIMS relative sensitivity factor for Pu to U of 6 is assumed. Different SIMS identified isotopic ratio groups are presented, and the influence of interferences in the Pu and U mass range are estimated. The study found that the materials are a mixture of highly enriched 235U (235U:238U ratio from 0.96 to 1.4) and so-called weapons grade Pu (240Pu:239Pu ratio from 0.028 to 0.059) and confirms earlier work reported in the literature.     

Plutonium and americium in the sediments off the Thule air base, Greenland

In 1968 a U.S. B-52 bomber from USA with four nuclear weapons crashed on the sea ice near the Thule air base and contaminated the surroundings. Most of contamination was recovered during the cleanup program. However, some of the plutonium still remains in the bottom sediments of the area. In 1997 an international expedition with a comprehensive sampling program was performed. A lot of sediment samples were taken with a Finnish Gemini corer. Sediment samples from 5 sampling stations, 80 samples altogether, were pretreated in Ris, Denmark, and analysed for transuranic elements at STUK, Finland. The samples were analysed primarily for Pu, but gamma-spectrometric measurements of ²⁴¹Am were also made. Generally, the Pu concentrations in the area studied were from 1 to 3 magnitudes higher than the fallout level in the Arctic sea area. None of the vertical profiles of Pu at the various stations showed a typical Pu peak originating from the accident in 1968, but the sediments were mixed down and contaminated to the depths studied (20 cm). The presence of large quantities of hot particles distorted the estimations of mean concentrations and inventories. Samples with plutonium from the accident show significant variations of nuclide ratios, ²³⁸Pu/^239,240Pu, ²⁴¹Pu/^239,240Pu and ²⁴¹Pu/²⁴¹Am. This indicates that Pu at Thule may be from more than one source of different quality.     

Source term identification of environmental radioactive Pu/U particles by their characterization with non-destructive spectrochemical analytical techniques

Six radioactive particles stemming from Thule area (NW-Greenland) were investigated by gamma-ray and L X-ray spectrometry based on radioactive disintegration, scanning electron microscopy coupled with energy-dispersive and wavelength-dispersive X-ray spectrometer, synchrotron radiation based techniques as microscopic X-ray fluorescence, microscopic X-ray absorption near-edge structure (μ-XANES) as well as combined X-ray absorption and fluorescence microtomography. Additionally, one particle from Mururoa atoll was examined by microtomography. From the results obtained, it was found out that the U and Pu were mixed in the particles. The U/Pu intensity ratios in the Thule particles varied between 0.05 and 0.36. The results from the microtomography showed that U/Pu ratio was not homogeneously distributed. The ²⁴¹Am/^{238 + 239 + 240}Pu activity ratios varied between 0.13 and 0.17, indicating that the particles originate from different source terms. The oxidation states of U and Pu as determined by μ-XANES showed that U(IV) is the preponderant species and for Pu, two types of particles could be evidenced. One set had about 90% Pu(IV) while in the other the ratio Pu(IV)/Pu(VI) was about one third.     

Studies of transuranics in an arctic marine environment

Since the accidental loss of four nuclear weapons by a B-52 at Thule Airbase, Greenland in 1968, the marine environment at Thule has showed enhanced levels of Pu and Am. Most of the activity is confined to the benthic environment within a distance of 50 km from the crash site of the B-52. Samplings of sediments, benthos, seaplants, fish, and water have been carried out in 1968, 1970, 1974, 1979, and in 1984. The study presented herein intends to answer the following questions: What is the mean residence time of these transuranics in the benthic communities? Do Pu and Am behave differently in the environment?     

Comparison of radionuclides levels from the Chernobyl reactor accident and from global fallout

Studies on radioactive fallout from atmospheric nuclear weapons tests have been carried out at this laboratory since the mid-fifties. The data thus generated on the levels and composition of radioactive fallout in India has been published periodically. Consequent to the Chernobyl reactor accident in the USSR in April 1986, similar studies were carried out. A number of fairly active samples were collected from commercial aircraft which had flown over the USSR soon after the accident. Even though the levels of fallout from the Chernobyl reactor accident observed in India were not significant from a health hazard view point, the studies provided detailed information on differences in the composition of fallout from the accident and long term radiation exposures likely to accrue from the Chernobyl fallout as opposed to global fallout from atmospheric nuclear weapons tests. This paper presents the results and their interpretation on the above aspects.     

The Legacy and Future of Radioactive Waste Management at the Millennium

Wastes containing radioactive materials have been produced ever since ore recovery and processing began; however, such materials did not become of public concern until the large-scale activities involving uranium and thorium ores and nuclear fission during and after World War II. Efforts to provide disposal sites for radioactive wastes, especially those associated with nuclear weapons and nuclear energy, have been largely unsuccessful for the past 40 years or so and are nearing crisis proportions as the new millennium begins — its eventual resolution is believed to require greater reliance on stewardship and a larger governmental presence.     

中国海大陆架沉积物超细标准物质系列研制

5个中国海大陆架沉积物标准物质的原样分别取自东海和南海,样品风干后,先经球磨制备成200目的均匀粉体,再用气流磨进一步加工成超细粒度的均匀样品.采用激光粒度仪检测了样品的粒度分布,5个样品的平均粒度均小于4 μm(约800目).采用高精度的XRF检验了样品的均匀性并以高灵敏度的ICP-AES、ICP-MS相配合确定了其最小取样量(5 mg).有12个实验室参加了合作定值研究,定值组分均为60个,其中MSCS-1,2分别有50和51个组分定为标准值,MSCS-3,4,5有52个组分定为标准值.全组分百分总和分别为99.9%, 99.9%, 100.4%, 100.1%和99.7%.     

Uranium leaching using mixed organic acids produced by Aspergillus niger

Source term information is required for to reconstruct a device used in a dispersed radiological dispersal device. Simulating a radioactive environment to train and exercise sampling and sample characterization methods with suitable sample materials is a continued challenge. The Idaho National Laboratory has developed and permitted a radioactive response training range (RRTR), an 800 acre test range that is approved for open air dispersal of activated KBr, for training first responders in the entry and exit from radioactively contaminated areas, and testing protocols for environmental sampling and field characterization. Members from the Department of Defense, Law Enforcement, and the Department of Energy participated in the first contamination exercise that was conducted at the RRTR in the July 2011. The range was contaminated using a short lived radioactive ⁸²Br isotope (activated KBr). Soil samples contaminated with KBr (dispersed as a solution) and glass particles containing activated potassium bromide that emulated dispersed radioactive materials (such as ceramic-based sealed source materials) were collected to assess environmental sampling and characterization techniques. This presentation summarizes the performance of a radioactive materials surrogate for use as a training aide for nuclear forensics.     

A comparison of two micro-beam X-ray emission techniques for actinide elemental distribution in microscopic particles originating from the hydrogen bombs involved in the Palomares (Spain) and Thule (Greenland) accidents

In order to validate and to gain confidence in two micro-beam techniques: particle induced X-ray emission with nuclear microprobe technique (μ-PIXE) and synchrotron radiation induced X-ray fluorescence in a confocal alignment (confocal SR μ-XRF) for characterization of microscopic particles containing actinide elements (mixed plutonium and uranium) a comparative study has been performed. Inter-comparison of the two techniques is essential as the X-ray production cross-sections for U and Pu are different for protons and photons and not well defined in the open literature, especially for Pu.The particles studied consisted of nuclear weapons material, and originate either in the so called Palomares accident in Spain, 1966 or in the Thule accident in Greenland, 1968. In the determination of the average Pu/U mass ratios (not corrected by self-absorption) in the analysed microscopic particles the results from both techniques show a very good agreement. In addition, the suitability of both techniques for the analysis with good resolution (down to a few μm) of the Pu/U distribution within the particles has been proved. The set of results obtained through both techniques has allowed gaining important information concerning the characterization of the remaining fissile material in the areas affected by the aircraft accidents. This type of information is essential for long-term impact assessments of contaminated sites.     

X射线荧光光谱法同时测定矿石中铀和钍

建立了X射线荧光光谱法测定矿石样品中铀、钍含量的快速分析方法。采用高压粉末制样法,对不同含量的放射性样品的压片压力、粒径、含水率、用量等处理条件到进行单因素实验。在400 MPa压力下压制,克服了低压制样的弊端,制备的样片表面光滑、致密,大幅改善了制样重现性,有效地减少了部分基体效应,铀校准曲线的标准偏差从0.053%降到0.0071%,钍校准曲线的标准偏差从0.062%降到0.0057%。经国家一级标准物质验证,表明方法准确、可靠,能满足样品中铀、钍含量日常分析要求。     

Characterization of marine sediments using analytical techniques

This study deals with the characterization of a marine sediments profile from the Gulf of Tehuantepec, Mexico. Ten sediment samples obtained from a core of 18.3 m of length were analysed. Although there have been numerous marine sediments studies carried out in Mexico, more are needed to better understand the sea floor formation. Crystallographic, morphologic, physical, chemical and gamma ray activity analysis were carried out on the samples. The analysis results showed a decrease in organic matter content as a function of sea depth; this value is related to the specific surface area. Some hazardous materials as Cr, Mn, Ni, Sr and Hg were also identified by PIXE in some samples, probably due to anthropogenic activity. The presence of uranium a naturally occurring element was found in all the samples, suggesting a migration through all materials of strata, radioactive elements such as ²²⁶Ra, ²³⁵U, ²¹²Pb, ²¹⁴Pb, ²²⁸Ac, ²⁰⁸Ti, ²¹⁴Bi, ²²⁸Ac and ⁴⁰K were detected.     

Preparation and thermal stability of Al2O3-clay and Fe2O3-clay nanocomposites, with potential application as remediation of radioactive effluents

In the last years metal/clays, aluminosilicates with properties and characteristics of microporous materials, have received more attention, due to the possibility of their use as matrix for nanoparticles encapsulation and stabilization processes. Some types of clays were comparatively evaluated for treating the simulated radioactive wastewater. The raw clay from Valea Chioarului Romania and its pillared forms with Al, Fe, pillars for decontamination of waste-waters with medium and low radioactivity were used. Characterization of the obtained materials was carried out using techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, BET analyses and thermogravimetric analysis (DTG-TG), respectively. Also, the thermal stability of nanocomposites was highly superior to native clay due to the presence of the well-dispersed clay nanolayer, which has a barrier property in a composite system. Clay nanocomposite sample materials were obtained with good thermal stability after calcination. Clay nanocomposites samples were evaluated for remediation of radioactive effluents by treating the radioactive wastes streams. The ion-exchange characteristics and the abilities to uptake radioisotopes of indigene clay from Valea Chioarului area-Romania were examined. The results showed that the precursor used in sample preparation influenced the structural and textural properties of nanocomposites and also capability of prepared modified clay samples by pillaring to be potential candidates for use in connection with environmental protection, remediation of radioactive effluents, respectively.     

Multi-point radiation monitor

A simple, inexpensive instrument for measuring radiation fields in otherwise inaccessible locations has been developed. The RadRope consists of a series of radiation detectors inside a flexible sheath and connected to a data readout device to alert the operator to unexpected radiation fields at a remote location. The instrument is designed for use in a maritime environment and will assist inspection personnel in detecting potential illicit radioactive materials or radiological/nuclear weapons of mass destruction.     

Morphology of actinide-rich particles released from the BOMARC accident and collected from soil post remediation

The physical, chemical, and radiological characteristics of material released to the environment from accidents involving nuclear weapon components are dependent upon many factors, especially the manner in which the material is released and delivered to the environment. These characteristics will also be influenced by physical and chemical effects associated with weathering if the material remains exposed to the environment for a long period of time. This study evaluates the morphological characteristics of particles released to the environment as a result of the 1960 BOMARC incident and compares these characteristics to those described following similar incidents at Thule, Greenland (1968) and Palomares, Spain (1966). Each of these incidents involved unique circumstances and conditions that distributed actinide-rich particles to the environment with a range of distinctive morphological characteristics. Morphological and surface elemental analyses were conducted on a set of discrete particles isolated from samples of post-remediated soil collected at McGuire Air Force Base, the site of the BOMARC incident. Scanning electron microscopy and complimentary energy dispersive X-ray spectroscopy were used to perform the analyses. Non-destructive analysis of uranium and plutonium contained in each particle was measured using high-resolution gamma spectrometry. Unique characteristics of the BOMARC samples include some particles exhibiting a smooth, crystalline texture and varying elemental surface distribution of uranium and plutonium, dependent on the particle’s morphology.     

Application of overpressured layer chromatography combined with digital autoradiography and mass spectrometry in the study of deramciclane metabolism

Overpressured layer chromatography was combined with the highly sensitive and rapid digital autoradiography (DAR) and mass spectrometry to separate, detect, and identify 3H- and 14C-labeled deramciclane metabolites in different biological matrixes. Several minor and major metabolites were separated from plasma and urine samples. The radioactive metabolites localized by DAR were scraped from the thin-layer chromatographic plate and transferred to a mass spectrometer for structure identification. Several metabolites were isolated and characterized, including hydroxy-N-desmethyl deramciclane, which is described in detail. The combination of techniques is efficient and has good sensitivity: about 2 micrograms metabolite from a biological matrix was isolated and identified this way.     

Sequential isotopic determination of plutonium,thorium, americium and uranium in the air filter and drinking water samples around the WIPP site

The simultaneous determination of actinides in air filter and water samples around the WIPP site have been demonstrated. The analytical method is based on the selective separation and purification by anion exchange and Eichrome-TEVA, TRU and DGA-resin followed by determination of actinides by alpha spectrometry. Counting sources for alpha spectrometric measurements were prepared by microcoprecipitation on neodymium fluoride (NdF₃). Radiochemical yields were determined using ²⁴²Pu, ²²⁹Th, ²⁴³Am and ²³²U as tracers. The validation of the method is performed through the analysis of reference materials or participating in laboratory intercomparison programs. The plutonium concentrations in aerosols varied seasonally, being highest in spring and summer due to the spring-time enhanced wind-storm transportation of radioactive aerosols from the stratosphere to the troposphere. The ²³⁸Pu/^239+240Pu activity ratio in the aerosol samples is typically close to that of global fallout from historic above-ground nuclear weapons testing. The results presented here indicate that the source of plutonium in the WIPP environment results mainly from global nuclear fallout and there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP.     

Noble metals as permanent chemical modifiers for the determination of mercury in environmental reference materials using solid sampling graphite furnace atomic absorption spectrometry and calibration against aqueous standards

Iridium, palladium, rhodium and ruthenium, thermally deposited on the platform, were investigated as permanent modifiers for the determination of mercury in ash, sludge, marine and river sediment reference materials, ground to a particle size of 50 μm, using solid sampling graphite furnace atomic absorption spectrometry. A total mass of 250 μg of each modifier was applied using 25 injections of 20 μl of modifier solution (500 mg l⁻¹), and executing a temperature program for modifier conditioning after each injection. The performance of palladium was found to be most consistent, taking the characteristic mass as the major criterion, resulting in an excellent correlation between the measured integrated absorbance values and the certified mercury contents. Mercury was found to be lost in part from aqueous solutions during the drying stage in the presence of all the investigated permanent modifiers, as well as in the presence of the palladium and magnesium nitrates modifier added in solution. A loss-free determination of mercury in aqueous solutions could be reached only after the addition of potassium permanganate, which finally made possible the use of aqueous standards for the direct analysis of solid samples. A characteristic mass of 55–60 pg Hg was obtained for the solid samples, using Pd as a permanent modifier, and also in aqueous solutions after the addition of permanganate. The results obtained for mercury in ash, sludge and sediment reference materials, using direct solid sapling and calibration against aqueous standards, as well as the detection limit of 0.2 mg kg⁻¹ were satisfactory for a routine procedure.     

Beiträge zur mikrochemischen analyse langlebiger uranspaltprodukte in staubproben

A microchemical qualitative and quantitative separation process for long-lived radionuclides from uranium fission (Cs, Sr, Ce, Zr, Ru) in dust samples is described. The loaded dust filter is moistened with carrier solution and with borax-sodium carbonate, and ashed in an electrically heated platinum spiral; the dust is thus decomposed, forming beads. The solution of the bead in dilute acid is concentrated in a ring with the ring oven ; the paper bearing the radioactive ring is cut into sectors and a specific precipitation reaction is applied for each nuclide in separate sectors. Identification and determination are carried out by autoradiography of the sectors. Practical testing was done with a 2.5-year old dust sample originating from nuclear studies in 1961–62 ; radioactive Cs, Sr and Ru were detected in 1.7 mg of dust ash. The quantitative evaluation of strontium-90 of the order of 10^-12 C showed the sensitivity of the method. The range of application of the method is indicated.