Production of ²³⁵Np, ²³⁶Pu and ²³⁷Pu via nuclear reactions on ^235,236,238U and ²³⁷Np targets

A summary of methods for cyclotron production of 235Np (396.1d), 236Pu (2.858y) and 237Pu (45.2d) via nuclear reactions with protons and 3He-ions on 235,236,238U and 237Np targets in wide energy ranges is given. Methods for the chemical separation and purification of these nuclides from the irradiated uranium and neptunium targets are described. Cross sections, yields and radionuclidic purities of 235Np, 236Pu and 237Pu are presented and compared with literature data on the nuclear reactions leading to these radionuclides. The nuclear reactions with the so far highest known yields of 235Np, 236Pu and 237Pu are determined: 236U(p, 2n)235Np, 237Np(p, 2n + pnβ-)236Pu and 237Np(p, n) 237Pu, respectively. The highest radionuclidic purity of 235Np, 236Pu and 237Pu tracers can be reached with the 236U(p, 2n)235Np, 236U(p, nβ -)236Pu and 237Np(3He, t) 237Pu reactions, respectively. In addition new cross sections and yield data of the 236U(3He, p3n)235Np reaction in the energy range 42.4-60 MeV are given.</p

Quantitative elemental analysis of dry-ashed bark and wood samples of birch, spruce and pine from south-western Finland using PIXE

A total of over 200 different samples of bark and wood of Silver birch, Norway spruce and Scots pine were analysed. Samples were taken from several areas in western Finland, some with known sources of atmospheric heavy metal emission (Harjavalta, Ykspihlaja). Also analytical data for pine needles from some sites are reported. The chemical analyses were performed by thick-target particle-induced X-ray emission (PIXE) spectrometry after preconcentration by dry ashing of samples at 550oC. The following elements were quantified in most of the samples: P, S, K, Ca, Mn, Fe, Ni, Cu, Zn, Rb, Sr, Cd, Ba and Pb. The ash percentage and the chemical composition of ashes of different wood materials were also obtained, as dry ashing was used in the analytical procedure. The variations in elemental concentrations in wood and bark of an individual tree, expressed as RSDs, were mostly in the range 10 – 20 %. For several trees of the same species sampled from small areas (< 1 ha), the variations in elemental concentrations were surprisingly high (RSDs 20 – 50 %). In the vicinity of metal plants, effects of strong atmospheric heavy metal pollution (pollution factor above 100) were observed in pine bark. The increase of heavy metal content in wood samples from the same sites was quite small. Elemental concentrations in ashes of bark and wood, from areas with no local source of atmospheric pollution, were relatively uniform. Based on this observation an alternative way of demonstrating atmospheric pollution of tree bark is discussed

Determination of trace element profiles in coarse-grained minerals by external millibeam PIXE - A schorl tourmaline study

The thick-target PIXE technique was applied to direct analysis of trace elements in tourmaline minerals. Analyses of these minerals with conventional wet-chemical methods are difficult and time consuming. The PIXE analyses were carried out in air with a collimated proton beam. As the technique was used in combination with a polarizing microscope it provided excellent control over the spots analyzed. A scanning device was developed for remote-controlled spot analyses across the surface of the samples. Several scans were run across polished sections of multicrystal schorl-tourmaline aggregates. Pellets of crushed and ground tourmaline samples were also analyzed. The method was calibrated against USGS standard reference materials. The precision of the method varied between 1 and 10 % and the detection limits were 1-10 ppm for most of the elements analyzed. Different sets of X-ray absorbers were used to improve the sensitivity and reliability of the method for the elements of interest. The concentrations of fourteen elements were calculated from their X-ray yields and the fluorine content was simultaneously determined using the 109.8 keV gamma line. The tourmaline samples were taken from a complex granite pegmatite on the Kimito island in SW Finland. They were found to contain mainly elements with Z < 33 (lighter than As). Relatively high concentrations of Fe, Zn, Ga and F were observed. Zinc was found to be a geochemically important minor element in schorl with a concentration ranging from 0.10 to 0.28 %. The pellets were found to contain inclusions of other minerals

Gill raker counting for approximating the ratio of river- and sea-spawning whitefish, Coregonus lavaretus (Actinopterygii: Salmoniformes: Salmonidae) in the Gulf of Bothnia, Baltic Sea

Background. The ability to distinguish between stocks in mixed fisheries is a prerequisite for a sustainable fisheries management. In the Gulf of Bothnia the relative contribution of endangered river-spawning and sea-spawning whitefish, Coregonus lavaretus (Linnaeus, 1758), to fisheries catches are currently not well known. This also applies to the southern Åland Islands, a major feeding ground for river-spawning whitefish from northern rivers. River- and sea-spawning whitefish are mixed while away from the breeding grounds and off the spawning season, and cannot be distinguished based on external features. Materials and methods. Analysis on gill raker numbers of river-spawning (n = 480) and sea-spawning (n = 456) whitefish from twelve locations at the Finnish west coast and the Åland Islands was performed. In whitefish sampled from feeding grounds at the Åland Islands the strontium concentration was analysed in otoliths from fish (n = 20) with low (27) and high (30) number of gill rakers. Results. A marked difference in the mean gill raker number of the river- and sea-spawning whitefish stocks was observed. The weighted mean of gill rakers of whitefish caught at spawning locations showed that the number of gill rakers of fish from rivers and the sea were 29.9 ± 2.14  (n = 480) and 26.7 ± 2.21  (n = 456), respectively. The difference between the two groups was highly significant (t = 22.50, df = 934, P < 0.0001). The means differed by 3.20 (2.92–3.48, 95% CL) indicating the groups are well separated.  In whitefish sampled at feeding grounds at the Åland Islands, otolith strontium concentration was higher (t = 2.09, df = 18, P = 0.04) in fish having 27 gill rakers (3.86 ± 0.30 mg · g–1, n = 10), compared to those having 30 gill rakers (3.54 ± 0.35 mg · g–1, n = 10).  Otolith strontium analysis thereby supported the utility of gill raker counting data for estimating the proportion of river- and sea-spawning whitefish in mixed populations. As expected, the gill raker counting method successfully indicated temporal alterations in the proportions of river- and sea-spawning whitefish on feeding grounds. Conclusion. Gill raker counting is an easy, fast, and inexpensive method that can be used to estimate the spatiotemporal occurrence and migratory patterns of river- and sea-spawning whitefish at the southern feeding grounds in the Gulf of Bothnia, and thereby aid in a sustainable management of whitefish stocks

Measurement of [11C]CO2 in exhaled air with a positron-sensitive single-wire proportional counter after i.v. injection of [11C] acetate

A positron-sensitive, large window single-wire proportional counter was used for measurements of [11C]CO2 in exhaled air after i.v. injection of [11C] acetate. The performance of the proportional counter was studied using Geant4 and Garfield simulation tools as well as experimentally by injections of known amounts of radioactive gas into measuring volume. The proportional counter was found to be sensitive enough for measuring the low concentrations of [11C]CO2 in the air exhaled by patients after i.v. injection of an 11C-labelled radiopharmaceutical. The limit of detection was 200 Bq/L for [11C]CO2

PI E X M E I C O 2 0 0 7 Removal of Ammonium from Wastewater with the Mineral Vermiculite -Using PIGE for Nitrogen Monitoring

Abstract. Solid samples were irradiated with a 4.2 MeV proton beam in a specially built chamber. The ion beam was extracted out of the cyclotron vacuum system through a 4 ;m thick nickel foil. A helium gas flow of 10 cm 3 /min was used to avoid interference from atmospheric nitrogen and oxygen. The emitted gamma radiation was measured with an HPGe coaxial detector located behind the chamber. The reaction 14 N(p,p&apos;@) 14 N was employed for the determination of nitrogen. The peak at 1454 keV from the nickel foil was used for the normalisation. A pressed pellet of KNO 3 was used for nitrogen calibration. The method was evaluated using six different biological certified reference materials. A synthetic tobelite mineral was also used in the evaluation. The limit of detection for nitrogen in the mineral samples was about 1 mg/g. The set-up was applied for the determination of the total amount of nitrogen in vermiculite. The mineral vermiculite was treated in different ways to optimize for the ammonium uptake. The experiments were performed by doping samples in ammonium solutions and by analysing the samples with PIGE. The aim of the study was to find a product that could be used for the removal of ammonium from wastewater