P. Vater

Sr/Y separation by supported liquid membranes based on nuclear track micro filters

First results of experiments concerning the preparation of a Y-90 generator are presented. The aim of this work is to prepare a rather cost-effective and easy to maintain Y-90 generator that produces Y-90 solutions of sufficient purity for their subsequent application in radionuclide therapy. Besides the need for high purity of the Y-90 solutions, it has to be taken into account that high activities are involved (up to 2 Ci Sr-90). Consequently, materials with very good radiation stability must be used for the construction of the generator. Nuclear track micro filters (NTMFs) prepared from polyimide foils are renowned for their outstanding radiolytical and chemical stability. In addition to that they have the distinct advantage that pore size and porosity can be chosen and optimized for each application. The NTMFs are used as supported liquid membranes (SLM) after impregnating them with a 1:1 mixture of bis-(2-ethylhexyl)-phosphate (HDEHP) and tributylphosphate (TBP). Y-90 separation from its parent Sr-90 is achieved by its selective transport through the pores of the impregnated NTMF. The Y-90 activity of the prepared solutions is determined by means of Cerenkov-counting, the Sr-90 content is calculated after determining the activity of an internal standard, namely Sr-85, by low-level gamma-spectrometry. It was shown that a separation of Y-90 and Sr-90 using NTMFs impregnated with an appropriate extractant is possible.

Radionuclides and heavy metals in environment

Preface. List of Participants. 1. Man - Made Radionuclides in Environment and Living Species. 2. Heavy Metals in Environment. 3. Radioactivity and Heavy Metals in Environment Natural Radioactivity Earthquakes. 4. Transmutation of Man-Made Radionuclides. Author Index. Subject Index.

An application of SSNTD to nuclear physics: Multiprong events in heavy ion reactions due to multiple sequential fission

Abstract The study of multiple sequential fission using SSNTDs and the 2π-geometry is described. Some quantitative considerations are given.

Nuclear track microfilters made of mica

Abstract Production and properties of a new class of microsieves with high resistance to corrosion, chemical attack and temperature is described. At the heavy ion accelerator facility GSI, mica foils of 50 mm diameter and up to 60 μm thickness are irradiated with xenon, lead or uranium ions of specific energies up to 8.5 MeV/amu at preset doses (10 3 –10 6 cm −2 ), making often use of the waste beam from nuclear research experiments. The irradiated foils are etched in hydrofluoric acid to the desired pore diameter. The side length of the rhomboidally shaped pore depends linearly on the etching time and has a Gaussian distribution of fwhm ∼12%. The pore size remains constant throughout the thickness of the filter. For higher porosities multiple holes occur with predictable probability. Application of these well defined microsieves is envisioned in chemical engineering for filtration of hot aggressive liquids, in environmental studies for accurate determination of airborne particles, and in diagnostic medicine for filtration of blood.

Kinematical analysis of 2-, 3- and 4-body channels in the reaction (12.5 MeV/u) 84Kr + natU observed with mica track detectors

Abstract The exclusive measurements of reactions induced by 1050 MeV 84 Kr ions incident on natural uranium have been made with the help of mica track detectors used in a 27 π -configuration. The cross sections for ternary and quarternary events have been determined by directly counting the numbers of events of relevant multiplicities. The angular distribution in the case of elastic events has been fitted by a generalized Fresnel model with parameters θ 1 4 ( c.m. ) = (33.5 ± 0.5)° and Δ = 8.5 ± 5. A complete kinematical picture of the reaction process has been deduced by converting the three-dimensional track parameters (lengths and angles) into parameters of reaction products (masses and energies) on an event by event basis. An empirical velocity-range relation has been used for this purpose, which has been obtained by an internal calibration procedure. It has been found that the reaction mechanism for the bulk of the data can be described as a sequential fission process. However, non-equilibrium effects appear for a small number of events (about 8%) in the three-body channel and completely dominate the four-body channel. In order to estimate the uncertainties of the computed quantities in relation to the measurement errors, Monte Carlo simulation of the selected data sets has also been performed.

Sequential fission studies in the interaction of 9.03 MeV/N 238U with natU using mica track detectors

Abstract The heavy ion interaction 9.03 MeV/N 238 U + nat U has been investigated using mica Solid State Nuclear Track Detector (SSNTD) in 2π-geometry. Numerical analysis of the track data yielded masses and energies of the reaction products formed in two-, three- and four-prong events. It has been observed that sequential fission, yielding three or four heavy fragments in the exit channel, is the main mode of the interaction. The five particle exit channel occurred with a considerable smaller probability. The relative yield of the four-particle exit channel increases with total kinetic energy loss (TKEL). But at the highest TKEL this trend is reversed and we observe the same amount of three-prong events as four-prong events. This might be explained by the large mass transfer forming surviving intermediate masses relatively stable against fission.

SSNTD and radiochemical studies on the transmutation of nuclei using relativistic ions

Extended targets were irradiated for transmutation studies with relativistic heavy ions. For this, a metal core was surrounded by a paraffin moderator. The metal is either copper or lead and it was irradiated with deuterium, alpha, or carbon beams of 1.5 or 3.7 GeV/u at the SYNCHROPHASOTRON, LHE, JINR, Dubna, Russia. During this irradiation copious amounts of secondary neutrons are produced and studied with SSNTD detectors and radiochemical sensors, for example: 139 La (n,γ) 140 La→ B- . The yield of reaction products allows an estimation of secondary neutron fluxes. The yields of all kinds of reactions produced with deuterium and alpha beams obey to some extent the law of limiting fragmentation, i.e. they show little influence on the energy and the kind of incoming particles. However, one observes with 44 GeV 12 C ions always enhanced nuclear cross-sections induced by secondary particles. This behavior could not be confirmed with theoretical estimations based on the Dubna Cascade Model in its Cascade Evaporation Model version (DCM-CEM). Finally, some results for transmutation studies on 127 I and Cu will be presented.

The etch-induction time (Tind) and other registration properties in CR-39 detectors for well-defined ions

Abstract The etch-induction time ( T ind ) in CR-39 for tracks of various ions, such as 4 He, 12 C, 86 Kr, 136 Xe, fission fragments, 208 Pb and 238 U has been measured. Three different kinds of CR-39 plastic detectors, made by Homalite, Pershore and Acrylic were used. The influence of the etching temperature on T ind has been measured. It is possible to differentiate fast light ions (84 MeV/amu 12 C), common alpha particles, and heavy ions (including fission fragments) by their T ind . Some applications to nuclear reaction studies are discussed.

Monitor reactions in Al-foils for high energy proton beams bombarding a thick target

Abstract During the bombardment of U and Pb targets (each 21 cm thick) with protons of energy 1.0 and 1.5 GeV, the reactions 27Al(p, 3pn)24Na and nat.Cu(p, X)24Na were studied as monitor reactions. The influence of 27Al(n, α)24Na on the monitor reaction 27Al(p, 3pn)24Na was investigated experimentally and theoretically. In order to avoid the influence of (n, α) reaction, placing of the Al-monitors 35 cm upstream the massive targets is recommended. This method may be used in Accelerator-Driven-Transmutation (ADT) studies of long-lived nuclear waste, where one always uses a massive heavy element target irradiated with protons at about 1 GeV. The experiments were performed at the Laboratory of High Energies, JINR, Dubna, Russian Federation.

On the energy resolution of α-sources prepared by electrodeposition of uranium

Abstract Using energy-dispersive X-ray fluorescence (EDXF) analysis of electrodeposited α-sources, we show that, after heating to glowing, the deposited material on the metal plates takes the form of very small spheres. Moreover, the average diameter of these spheres is found to depend on the degree of smoothness of the metal-plate surface. In addition, this spherelike material is found to consist not only of uranium but also of platinum, the latter of which originates from the platinum anode used for electrodeposition. Consequently, the energy resolution of α-sources prepared in this way is dependent not only on the physical attributes of the surface of the planchets used, but also on the duration of deposition.