Deconvolution of 238,239,240Pu conversion electron spectra measured with a silicon drift detector.

Internal conversion electron (ICE) spectra of thin 238,239,240Pu sources, measured with a windowless Peltier-cooled silicon drift detector (SDD), were deconvoluted and relative ICE intensities were derived from the fitted peak areas. Corrections were made for energy dependence of the full-energy-peak counting efficiency, based on Monte Carlo simulations. A good agreement was found with the theoretically expected internal conversion coefficient (ICC) values calculated from the BrIcc database.

Rapid alpha spectrometry from liquids doped with ²°9Po and ²4¹Am using simplified sample processing.

Rapid detection of alpha-particle emitting radionuclides from liquids doped with (209)Po and (241)Am was investigated. These nuclides may mimic or be among those that could be used as threat agents in malevolent actions such as deliberate poisoning of refreshments. The liquids investigated here by using a semiconductor alpha detector in vacuum were coffee, beer and apple juice. Methods for the sample processing were rapid evaporation of the liquids and filtration. Both methods produced samples, which gave alpha spectra that could be readily analyzed by an unfolding program. The doped radionuclides were easily identified from the spectra, but the samples were too thick for reliable activity determination. Determination of the activity ratios is possible if the peak shapes are equal. However, radionuclides may behave differently during the sample preparation, which must be accounted for in the activity ratio determination.

Conversion electron spectrometry of Pu isotopes with a silicon drift detector.

An electron spectrometry set-up was built at IRMM consisting of a vacuum chamber with a moveable source holder and windowless Peltier-cooled silicon drift detector (SDD). The SDD is well suited for measuring low-energy x rays and electrons emitted from thin radioactive sources with low self-absorption. The attainable energy resolution is better than 0.5keV for electrons of 30keV. It has been used to measure the conversion electron spectra of three plutonium isotopes, i.e. (238)Pu, (239)Pu, (240)Pu, as well as (241)Am (being a decay product of (241)Pu). The obtained mixed x-ray and electron spectra are compared with spectra obtained with a close-geometry set-up using another SDD in STUK and spectra measured with a Si(Li) detector at IRMM. The potential of conversion electron spectrometry for isotopic analysis of mixed plutonium samples is investigated. With respect to the (240)Pu/(239)Pu isotopic ratio, the conversion electron peaks of both isotopes are more clearly separated than their largely overlapping peaks in alpha spectra.

Performance of an in-situ alpha spectrometer.

Equipment was recently developed for detecting alpha particles from flat and smooth surfaces with good energy resolution at ambient air pressure. In this work, the detection efficiencies were determined using different extended-area sources emitting alpha and beta radiation and a mixed nuclide point source emitting alpha radiation. Beta particles are of importance because they can also be detected. Counts originating from alpha and beta particles are mainly at different energies, which make their separation possible. An efficiency of 0.14 was determined for an extended-area (>30cm(2)) homogeneous source emitting alpha radiation at the energy of 5-6MeV, whereas for the beta emitters the efficiencies were 0.07-0.19 depending on the beta-particle emission energies. The use of a collimator reduces the detection efficiencies by a factor of up to ten.

Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector.

The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a (252)Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10(-4), whereas three-fold greater efficiency was obtained for a (241)AmBe neutron spectrum.

Determination of 239Pu/240Pu isotopic ratio by high-resolution alpha-particle spectrometry using the ADAM program.

A novel analysis program to unfold alpha-particle energy spectra was introduced, demonstrated and validated using radiochemically processed test sources, which contained different amounts of (239)Pu and (240)Pu. A high-resolution alpha spectrometer was used for data acquisition. The software known as ADAM unfolds the spectra using nuclide-specific decay data as a constraint. The peaks can have different shapes and the software can also cope with the coincidences between alpha particles and electrons/photons. In the present paper, the (239)Pu/(240)Pu activity ratios from alpha spectrometry agreed, within the stated uncertainties, with the reference values. Number of counts in the (239,240)Pu peak group must be larger than 100 to obtain reliable values when using semiconductor detector of energy resolution FWHM=10.6 keV.

Characterization of radioactive particles using non-destructive alpha spectrometry.

Spherical particles with known properties were used to demonstrate and test a novel software package known as AASIFIT, which is able to unfold complex alpha spectra. A unique feature of the program is that it uses simulated peak shapes in the fitting process. The experimental reference particles in the testing were artificially produced U particles of diameter 1.4microm and a nuclear bomb particle with a twenty-fold greater diameter, mainly composed of U and Pu dioxides. AASIFIT was used to determine the density of the U particles. In addition, the activities of (239+240)Pu and (241)Am were determined for the nuclear bomb particle and compared to earlier determinations in the literature. The results of this investigation demonstrated that the software can be used to estimate the properties of particles emitting alpha radiation. However, the composition and geometry of the investigated particles need to be known with good accuracy for reliable estimates. Furthermore, uncertainties in the stopping power data, especially for U and Pu, may have an influence on the results obtained from the software.

Design of an air sampler for a small unmanned aerial vehicle.

In the aftermath of a nuclear accident or malevolent act, it is of paramount importance to have the capability to monitor airborne radioactive substances by collecting air samples. For potentially dangerous missions, the Radiation and Nuclear Safety Authority of Finland (STUK) has developed an air sampler to be used on a small unmanned aerial vehicle. When a Petrianov or Fluoropore filter is used in the sampler and the air velocity is 71 km h(-1), the air flow rate through the filter is 0.73 m(3) h(-1) or 0.23 m(3) h(-1), respectively. The present article introduces the developed air sampler using fluid dynamic simulations and wind tunnel data. The operation of the system was validated by collecting airborne radioactive aerosols from air.

Direct high-resolution alpha spectrometry from nuclear fuel particles in an outdoor air sample.

The potential use of direct high-resolution alpha spectrometry to identify the presence of transactinium elements in air samples is illustrated in the case when alpha-particle-emitting radionuclides are incorporated in nuclear fuel particles. Alpha particle energy spectra are generated through Monte Carlo simulations assuming a nuclide composition similar to RBMK (Chernobyl) nuclear fuel. The major alpha-particle-emitting radionuclides, in terms of activity, are 242Cm, 239Pu and 240Pu. The characteristics of the alpha peaks are determined by fuel particle properties as well as the type of the air filter. It is shown that direct alpha spectrometry can be readily applied to membrane filter samples containing nuclear fuel particles when rapid nuclide identification is of relevance. However, the development of a novel spectrum analysis code is a prerequisite for unfolding complex alpha spectra.

Multi-technique characterization of a nuclear bomb particle from the Palomares accident.

A January 1966 accident dispersed Pu and other nuclear bomb materials in the vicinity of Palomares, a village in southeastern Spain. Radioactive particles were identified in a soil sample collected in 1998 and analytical results obtained from one of the isolated particles are presented here. Isolation of the particle was performed using gamma-ray spectrometry and imaging plates. Scanning electron microscopy with X-ray microanalysis revealed the presence of U and Pu as well as Pb and Fe in the particle of approximately 10microm diameter. Radioisotopes of U, Pu, and Am were quantified using radiometric methods, inductively coupled plasma mass spectrometry and secondary ion mass spectrometry. The elevated (235)U/(238)U atom ratio indicates enriched U, and the Pu atom ratios are consistent with weapons-grade material. This work demonstrates that the analysis of individual particles provides information not available through bulk sample analysis.

High-resolution alpha spectrometry under field conditions - fast identification of alpha particle emitting radionuclides from air samples.

Alpha particle emitting radionuclides may be released into the atmosphere as a result of a severe nuclear accident, the malevolent use of radioactive material or some other incident. Rapid detection methods are then of crucial importance for carrying out well-timed protective actions. The present paper demonstrates that a method in which an aerosol sample is collected on a filter and directly analysed by high-resolution alpha spectrometry in a vacuum chamber, but without radiochemical sample treatment, is suitable for field measurements. A detection limit of less than 0.1 Bqm(-3) for (239)Pu is achieved assuming 1-h sampling using a glass-fibre filter and 1-h data acquisition. This value is higher than in the case when sampling is performed using a porous membrane filter. A measurement system consisting of standard components is mounted in a vehicle designed for rapid field measurements.

Minimum detectable activity concentration in direct alpha spectrometry from outdoor air samples: continuous monitoring versus separate sampling and counting.

Rapid method for identifying the presence of alpha particle emitting radionuclides in outdoor air is of paramount importance should a nuclear or radiological incident occur. Minimum detectable activity concentrations of U, U, Pu, and Pu in outdoor air are calculated for two direct alpha spectrometry methods: continuous air monitoring is compared with separate sampling and subsequent alpha particle counting in a vacuum chamber. The radon progeny activity concentration typical for outdoor air and the effects for the alpha particle spectra caused by the properties of the filter and the aerosol particles are taken into account using measurements and Monte Carlo simulations. Continuous air monitoring is a faster method for identifying the presence of (trans)uranium elements when their activity concentration is considerably higher than the typical detection limit. Separate sampling and counting in a vacuum chamber is a more sensitive method when concentrations are close to the detection limit and when the duration of the sampling-counting cycle is greater than approximately 2 h. The method may serve as a tool for rapid field measurements.

Design of a radiation surveillance unit for an unmanned aerial vehicle.

This paper describes a prototype of a compact environmental radiation surveillance instrument designed for a Ranger unmanned aerial vehicle. The instrument, which can be used for tracking a radioactive plume, mapping fallout and searching for point sources, consists of three different detector types (GM, NaI(Tl) and CZT) and an air sampling unit. In addition to the standard electronics for data acquisition, the system contains an onboard computer, a GPS receiver and environmental sensors, all enclosed in a single housing manufactured of fiberglass-reinforced composite material. The data collected during the flight is transmitted in real-time to the ground station via a TETRA radio network. The radiation surveillance unit is an independent module and as such can be used in, for example, airplanes, helicopters and cars.

Simulation of alpha particle spectra from aerosol samples.

A Monte Carlo code is developed for simulating energy spectra of alpha particles from aerosol samples. Geometrical detection efficiency and energy loss of the alpha particles in the source itself and in the material between the source and detector are simulated. Different characteristics of the aerosol particles and medium material are taken into account in the computation. An excellent agreement with earlier results and measurements is found. The code can be applied for example in designing optimal aerosol sampling methods in direct alpha spectrometry.

Over-expression of tenascin-C in malignant pleural mesothelioma.

AIMS: Tenascin-C is an extracellular matrix glycoprotein known to have anti-adhesive characteristics and to be expressed in various human malignant neoplasms. We hypothesized that the expression of tenascin-C would be increased in human malignant pleural mesothelioma, and its accumulation associated with the prognosis of the patients with this disease. METHODS AND RESULTS: Thirty-seven cases of mesothelioma were studied by immunohistochemically using a monoclonal antibody against tenascin-C, and with a semiquantitative scoring system for tenascin-C in different areas of the tumours. In 10 selected cases tenascin-C mRNA in-situ hybridization was also analysed. Since transforming growth factor-beta (TGF-beta) is known to induce both the synthesis of tenascin-C and the growth of mesotheliomas, an immunohistochemical analysis of TGF-beta 1, -beta 2 and -beta 3 was also performed. Normal pleura (n = 7) and metastatic pleural adenocarcinomas (n = 7) were used as controls. Tenascin-C protein was expressed in every histological subtype of malignant mesothelioma, being most prominent in the fibrotic stroma of a tumour, around tumour cells and at the invasive border, whereas tenascin-C mRNA was scarce in tumour cells. The patients with less immunohistochemical expression for tenascin-C tended to live longer (P = 0.028 by Fishers' exact probability test). All mesotheliomas showed positivity for at least one isoform of TGF-beta. CONCLUSIONS: In conclusion, high expression of tenascin-C protein in malignant pleural mesotheliomas may play a role in its invasive growth, and might serve as a prognostic marker of the disease.

Characterisation of projectiles composed of depleted uranium.

Projectiles suspected to be composed of depleted uranium (DU) were found in Kosovo. Their properties were analysed using alpha and gamma ray spectrometry, mass spectrometry and electron microscopy. They were found to be composed of DU with small amounts of other elements such as Ti. 236U was detected in the penetrators, reflecting the use of reprocessed fuel. No transuranium elements were detected. The typical external dose rate meter is not the best option for mapping the location of penetrators from the ground. Monte Carlo calculations were performed in estimating possible skin doses. Penetrators in long-lasting contact with skin may cause a notable equivalent dose to skin.

Distribution and mRNA expression of tenascin-C in developing human lung.

Tenascin-C is an extracellular matrix glycoprotein that is spatially expressed during organogenesis, in inflammatory and fibrotic disorders, and in neoplasms. The aim of this study was to analyze its expression in developing human lung tissues during pseudoglandular, canalicular, saccular, and alveolar periods corresponding to Weeks 12 to 40. Lung tissues were obtained at autopsy from 34 nonmalformed cases. An immunohistochemical analysis and a messenger RNA (mRNA) in situ hybridization method combined with light microscopy were used. The extent of tenascin-C immunoreactivity was scored as absent, low, moderate, or strong in and around different types of pulmonary cells. The immunohistochemical expression for tenascin-C was strong beneath the airway epithelium, especially at the sites of airway subdivision during Weeks 12 to 23, whereas its expression was moderate or weak underneath alveolar and bronchiolar epithelia between Weeks 24 and 40. The expression for tenascin-C was strong in the intima of veins, especially in the canalicular period, i.e., Weeks 17 to 28. A moderate or strong immunoreactivity for tenascin-C was also observed around chondrocytes in every case studied during all periods. The increased expression of tenascin-C mRNA was most often seen in the cells below the airway epithelium. Taken together, tenascin-C is expressed in human lung during all developmental periods, and its expression is especially strong below the airway epithelium at the sites of airway subdivision.

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.

Tenascin expression and distribution in pleural inflammatory and fibrotic diseases.

We hypothesized that tenascin expression is increased in pleural inflammatory and fibrotic diseases and that its expression can be used as a marker of active pleural involvement. For this purpose we analyzed 71 histological samples of inflammatory and fibrotic pleura from patients with asbestos-induced pleural reaction (n = 6), postcardiac injury syndrome (n = 6), parapneumonic infection and/or empyema (n = 23), tuberculosis (n = 5, rheumatoid disease (n = 1), and fibrosis with inflammation of unknown etiology (n = 30). All 71 cases were studied by immunohistochemistry for tenascin. In 19 selected cases tenascin mRNA in situ hybridization was also performed. In every case, tenascin was increased by immunohistochemistry. Most prominent immunoreactivity was detected in areas of newly formed fibrosis. Increased tenascin mRNA expression by in situ hybridization was detected in the individual cells of the newly formed fibrosis underneath the fibrinous exudate. The tenascin mRNA-positive cells localized in areas in which by immunohistochemical studies the cells were positive for alpha-smooth muscle actin, desmin, and vimentin, suggesting a myofibroblast phenotype. Tenascin mRNA expression was also seen less frequently in areas in which some cells were positive for cytokeratin. These cells might represent mesothelial cells entrapped in the inflammatory lesion. Alternatively, they might represent fibroblast-type cells with aberrant cytokeratin expression. We conclude that in pleural inflammatory and fibrotic diseases tenascin immunoreactivity is increased and tenascin mRNA-positive cells localized mainly in the areas of myofibroblast- and, less often, mesothelial-type cells, suggesting that mainly myofibroblasts and, less commonly, also mesothelial cells might be responsible for tenascin expression in pleural inflammatory and fibrotic diseases. (J Histochem Cytochem 48:1257-1268, 2000)

Tenascin mRNA expression at the foci of recent injury in usual interstitial pneumonia.

To elucidate which cells are synthesizing tenascin in usual interstitial pneumonia (UIP) we have analyzed thoracoscopic or open lung biopsies from 30 patients with UIP by mRNA in situ hybridization, using (35)S-labeled tenascin RNA probes. The phenotype of the cells expressing tenascin mRNA was confirmed by immunohistochemical stainings of serial sections with antibodies against alpha-smooth muscle actin and human cytokeratin. The results demonstrate that tenascin is expressed at the foci of recent lesions consisting of intralumenal or incorporating loose fibrotic buds. The cells expressing tenascin mRNA were located in and underneath the newly formed epithelium. Immunohistochemical stainings showed that the cells in the newly formed epithelium were strongly cytokeratin positive, and thus evidently regenerating type 2 pneumocytes, while the cells underneath the newly formed epithelium were alpha-smooth muscle actin positive and apparently myofibroblasts. Tenascin mRNA expression was clearly stronger and more frequent in myofibroblasts than in type 2 pneumocytes, however. Weak tenascin mRNA expression was also found in metaplastic bronchiolar-type epithelium and alveolar macrophages. Our results are thus in good agreement with the previous studies showing that tenascin is actively synthesized at the early fibrotic lesions in UIP. Furthermore, results demonstrate that the interaction between the epithelium and the underlying connective tissue plays a significant role in tenascin synthesis and that myofibroblasts are mainly responsible for its synthesis in fibroblastic foci of UIP.