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Isocratic anion exchange separations of Group V elements from solutions containing HF have been considered for the development of Db aqueous phase chemistry experiments. Separation of Nb/Ta from an HF/NH4F system has been demonstrated but has limited utility due to interferences with alpha and spontaneous fission (SF) source preparation. The physical parameters associated with ion exchange chromatography have been optimized for the separation and sequential isolation of Pa, Nb and Ta from mixed HF/HNO3 solutions. A suitable procedure incorporating a series of successive chemical separation techniques, i.e. precipitation and ion exchange chromatography, has been suggested for off-line Db characterization studies.

A procedure was developed for selective separation of Group IV elements from Sr and Lu, followed by rapid separation of Zr and Hf by cation-exchange chromatography in dilute HCl/HF solutions. The possibility of using this procedure for chemical identification and determination of decay parameters of the new isotope 267Rf was demonstrated.

Application of ultrasound and ball milling produces micrometer-sized crystallites of tris-(o-phenylenedioxy)-cyclotriphosphazene (TPP) that show zeolite-like reversible sorption of I 2 and CH 3 I (methyl iodide). The thermal stability of open-pore TPP is improved by partial loading with pyrazine. The sorption properties of open-pore TPP are investigated by the 1 3 1 I radioactive tracer method. Comparison with activated charcoal (ACC) shows that TPP has a higher sorption efficiency for I 2 dissolved in water than ACC. In the case of a humid gaseous source of CH 3 I also, TPP exhibits better sorption properties than ACC. Partial loading of open-pore TPP by pyrazine increases its thermal stability by 50 °C and the binding properties for retaining CH 3 I are also improved. Force-field calculations show a difference of ΔE20 kJ mol - 1 , making the open-pore system less stable than the apohost.

Summary A chemical separation procedure for Rf/Db is described which was applied to a long-lived decay product from the nuclear fusion reaction 48Ca+ 243Am. A 1.2 mg thick 243Am target was bombarded by 247 MeV 48Ca particles. The recoiling products were collected in a thick Cu catcher for about one day and then subjected to a chemical separation procedure that included an ion exchange from dilute HF solutions. Final samples were prepared on 30 μg/cm2 thick polyethylene (PE) foils and counted in 4π-geometry for α-particles and spontaneous fission (SF) coincidences. The detector arrays were surrounded by 3He detectors to also assay prompt neutrons. Decontamination factors from actinides of about 105 were achieved. Group 6 (W) to 14 (Pb) elements as models for their heavier homologues were shown to be separated from the Rf/Db fraction with more than 90%. In eight final samples, representing a total beam dose of 3.4 × 1018 particles, 15 SF events were detected. The decay pattern points to a single component with a half-life of ≈32h, which shows a chemical behavior similar to the lighter homologues of group 4 and 5 elements.

A semi-automated system has been developed for elution and concentration of the (188)Re-eluate from 111 GBq (3 Ci) (188)W/(188)Re-generators to provide a dissolved beta-source of high (188)Re-activity per unit volume. The elution progress and concentration were precisely and continuously monitored by use of collimated diode detectors. By using ion exchange cartridges, small eluate volumes (2-3 ml) of maximum 40 GBq, (188)Re/ml activity concentration were routinely prepared. The concentrated (188)Re solutions were used to beta-irradiate aqueous suspensions and solutions of iodine species to evaluate a simulation of the extent of radiolytic decomposition of chemical species (AgI and CH(3)I) expected to accumulate in the containment sump of a nuclear reactor in the event of a severe accident with reproducible dose rates of up to 0.4 Gys(-1). Results have shown that AgI colloidal particles decompose to varying extents, depending on conditions, and in proportion to their initial mass, which indicates surface oxidation. Experiments have also confirmed CH(3)I decomposition in proportion to initial aqueous concentration.

Phebus-FP is a multi-national collaborative programme comprising four integral and one debris bed melting and fission product release experiments. The integral experiments simulate the heat-up, degradation and fission product release and transport, thermal hydraulic response, aerosol behaviour and iodine chemistry in the containment. The total programme, including interpretation effort, runs from 1993 to ca. 2007. The experiments demonstrated new characteristics of core degradation, fission product and iodine chemistry and accident integral behaviour. PSI has participated extensively through planning support, interpretation of data from the experiments and analyses of the results to establish confidence in the models being used for plant application. A significant part of the PSI effort was performed to interpret the significance of silver iodide as an effective retention agent under typical reactor conditions. The conclusions are of an interim nature, since the data reduction and interpretation are not yet complete. The significance of the Phebus results for plant safety will be fully realised only after successful benchmarking of the computer codes against Phebus, and application to plant sequences. Such work remains in progress within the Phebus project and in various national programmes.

The decomposition of aqueous colloidal suspensions of AgI induced by ionizing radiation was investigated under various conditions using {sup 188}Re as an in situ beta-radiation source. The suspensions were stabilized by an initial excess of either I{sup -} or Ag{sup +} ions. Although the results were somewhat scattered, the following trends were observed. With an initial excess of I{sup -} and under strong oxidizing conditions (N{sub 2}O sparging) at pH 2, {approx}65% AgI was decomposed into nonvolatile and volatile iodine (ratio 2:1) for doses of {approx}20 kGy, and up to {approx}80% was decomposed (mostly nonvolatile iodine) at pH 5. Chloride ions greatly enhanced the volatile and lowered the nonvolatile fractions. Little decomposition (

The recent discovery of the elements 115 and 113 in the reaction 48Ca + 243Am was confirmed by an independent radiochemical experiment based on the identification of the long-lived decay product dubnium.

Iodine is a biologically important trace element. Its behaviour in the environment and in human metabolism is determined by the type of iodine species which takes part in chemical reactions. Knowledge of their concentrations is necessary to understand and describe the iodine reaction paths. A separation procedure is proposed for quick determination of common forms of iodine—iodide, iodate ions, molecular iodine and organoiodine (in the form of CH3I). The procedure consists of sequential sorption by passing the sample solution first through a solid-phase extraction cartridge to separate I2 and CH3I from IO3 − and I− then through an anion-exchange resin in a cartridge to retain the latter two species. Each loaded cartridge is eluted to separate the sorbed pair of species. Concentration determination of the resulting four solutions can be performed by standard methods, e.g. by spectrophotometry, tracer counting or with ion-selective electrodes.

An analytical quick-test method was developed to determine iodide and iodate ions in aqueous solutions using solid phase extraction cartridges for sample preparation. Work was focussed on finding simple, but efficient conditions for quantitative separation of iodate and iodide. Iodine amounts were then determined by standard methods. Ion-exchange absorbers in cartridge form were used. Selectivity and yield of the species separation were studied at pH value of 5-10 and various solution compositions using 131I radioactive tracer. The electrolytes used were diluted alkaline, nitrate and boric acid-borate solutions. Application to nuclear reactor cooling water analysis or environmental investigations and monitoring is proposed.

Iodine radionuclides constitute one of the most important fission products of uranium and plutonium. If the volatile forms would be released into the environment during a severe accident, a potential health hazard would then ensue. Understanding its behaviour is an important prerequisite for planning appropriate mitigation measures. Improved and extensive knowledge of the main iodine species and their reactions important for the release and retention processes in the reactor containment is thus mandatory. The aim of PSI's radiolytical studies is to improve the current thermodynamic and kinetic databases and the models for iodine used in severe accident computer codes.

A rapid method for the preparation of 87Y/87mSr radionuclide generator from a rubidium chloride target irradiated with 35 MeV α-particles is described. A simple two-step procedure is used to obtain a carrier-free 87mSr isotope with a high enough radiochemical yield and high purity in the final aqueous fraction.

The contemporary nuclear power plant chemistry, i.e. radiochemical research predominantly in relation to operational nuclear power plants with light water reactors, is focused mainly on the species analysis of reactor source term radionuclides and the trace element analysis of reactor structural material. Results of selected examples from the PSI nuclear safety research programme demonstrate the relevance of the current radiochemical analysis to solve important problems of reactor maintenance and material improvement.

Summary A new device was developed for the identification of several iodine species in aqueous solution using ion chromatography. Iodide, iodate and molecular iodine can be determined. (The equipment allows both conductivity and radioactivity detections.) The method is applicable for the determination of radioactive iodine contaminations in the cooling water of nuclear power plants.

The title goal was achieved using a DOWEX 50Wx8 cation exchange column saturated with La(OH)3 and ammonia solution as eluent. Hf, Ta and Lu were adsorbed on this column, whereas W remained in the solution. This chemical system may be used for fast on-line separations of element 106.

Some short-lived isotopes of Hf, Ta and W, synthesized at the U-400 cyclotron of JINR-Dubna, have been isolated using a previously elaborated fast continuous method of chemical isolation of element 104 from nuclear reaction products. The products were transported by a NaCl aerosol jet, from the irradiated targets to a separation device in which Hf, Ta and W were isolated by using three coupled ion-exchange columns.

The sorption behavior of microamounts of Hf and Ta on DOWEX 50×8 and DOWEX 1×8 from aqueous HCl/HF solutions has been investigated. Suitable separation conditions for these two elements on cation exchange resins were found in solutions containing 1.5M HCl/10−4M HF and 0.05M HCl/10−3M HF. Kinetic experiments showed that the system can be applied in high speed on-line separations.

The short-lived isotopes of W and their descendants have been isolated from the products of the bombardment of144Sm with24Mg by a fast continuous ion-exchange method, using HF solution media. The feasibility of this method for isolation of element 106 is discussed.

The present study has been performed within the framework of experiments aimed at the investigation of chemical properties of long‐lived Db isotopes in aqueous solutions. The isocratic anion exchange separations of group V elements in the solutions containing HF have been considered. Parameters of separation of dubnium homologues (Pa, Nb and Ta) in HF/HNO3 mixed solutions have been optimized. The procedure of separation of group V elements from multicomponent system has been suggested.

A cation-exchange procedure was developed for separating Nb from Ta, Pa from Ta, and Nb, Pa, and Ta from Zr, Hf, and lanthanides in dilute HC1/HF solutions. The stability of the fluoride complexes of Group IV and V elements decreases in the following order: Nb ∼ Pa > Zr > Hf > Ta. This procedure can be used in experiments on synthesis of superheavy nuclei for isolation of Db from the reaction products and for its chemical identification.

Chemical behaviour of group 5 elements in the aqueous hydrofluoric acid solutions was studied. The radiochemical method for the cation exchange separation of Nb (Pa) and Ta from Zr, Hf and lanthanides is presented. The developed scheme allows excluding of the presence of SF heavy actinides in fractions of separated elements. On the basis of the data of the present work, it is possible to suggest the following order of the stability of the fluoride complexes of group 4 and 5 elements: Nb ≈ Pa > Zr > Hf > Ta. The order of the complex formation is in agreement with theoretical predictions. This analytical procedure can be used in future heavy nuclei synthesis experiments for the separation of dubnium (Db) from other reactions products and for its chemical identification.

The results of two experiments designed to synthesize element 115 isotopes in the {sup 243}Am+{sup 48}Ca reaction are presented. Two new elements with atomic numbers 113 and 115 were observed for the first time. With 248-MeV {sup 48}Ca projectiles, we observed three similar decay chains consisting of five consecutive {alpha} decays, all detected in a total time interval of 30 s. Each chain was terminated by a spontaneous fission (SF) with a high-energy release and a lifetime of about a day. With 253-MeV {sup 48}Ca projectiles, we registered a different decay chain of consecutive {alpha} decays detected in a time interval of 0.5 s, also terminated by spontaneous fission, but after 1.8 h. The decay properties of the eleven new {alpha}- and SF-decaying nuclei are consistent with expectations for consecutive {alpha} decays originating from the parent isotopes {sup 288}115 and {sup 287}115, produced in the 3n- and 4n-evaporation channels, respectively. Support for the assignment of the atomic numbers of all of the nuclei in the {sup 288}115 decay chain was obtained in an independent experiment in which a long-lived spontaneous fission activity, {sup 268}Db (15 events), was found to be chemically consistent with the fifth group of the periodic table.more » The odd-odd isotope {sup 288}115 was observed with largest cross section of about 4 pb. In the SF decay of {sup 268}Db, a total kinetic energy of 230 MeV and a neutron multiplicity per fission of 4.2 were measured. The decay properties of the 11 new isotopes with Z=105-115 and the production cross sections are in agreement with modern concepts of the role of nuclear shells in the stability of superheavy nuclei. The experiments were carried out at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research.« less

Energy-dispersive X-ray fluorescence has become a well established analytical technique by means of which the elemental content of geological, marine, biological or other samples can be determined down to concentrations in the ppm range. However, there are many analytical problems with respect to environmental pollution control and industrial process control which demand the determination of ppb-con-centrations. Therefore, a new special type of X-ray fluorescence analyzer, the RFAA-30, was developed (Leonhardt et al., 1986; Bruchertseifer et al., 1987).

Iodine is a main fission product of the fuel generated during power operation in nuclear power plants (NPPs). A severe NPP accident can cause fuel, containing fission products (FPs), control rod assemblies and core structures to melt and then release into the containment. The key signatures of iodine behaviour during a NPP severe accident are reviewed, i.e. its release from the molten core in the reactor pressure vessel and transfer via the primary coolant system into the containment. Containment or filter failure would disperse radioactive iodine into the environment. The iodine radioisotopes, 131I (T1/2 ca. 8 d) in particular, in sufficient concentrations can pose a health hazard. The overview focuses on the current state of knowledge on iodine behaviour in containment. The formation of volatile iodine species (molecular iodine and organic iodides) by FP-radiation and recent efforts at PSI to suppress their release by reduction to non-volatile iodide for engineered systems are described. Despite extensively available data, further experimental studies are needed to reduce the significant uncertainties in model development. In particular, additional studies on organic iodide formation are required, since these species form the major volatile fraction under certain conditions. Gas phase reactions and the potential effects of many other sump constituents are also important.

Unter Venwendung radioaktiver Indikatoren wur den verschiedene Methoden der Abtrennung von Schwermetallen (Ir, Pt, Tl, Pb und Bi) aus den Quellwassern der Halbinsel Tscheleken und des Vulkans Mendelejew der Insel Kunaschir untersucht. Die optimalen Bedingungen zur Anreicherung der genannten Elemente werden angegeben und die Anwendungsbereiche der einzelnen Methoden aufgezeigt. Die eingesetzten Radionuklide wurden durch Bestrahlung von An- und Ta-Targets mit Kohlenstoff synthetisiert und radiochemisch abgetrennt.

Experiments have been performed to synthesize isotopes of elements 114–116 in fusion reactions between 48Ca ions and 246, 248Cm, 243Am and 242Pu target nuclei. The detection of reaction products by recording spontaneous fission and α-decay events allowed us to set upper limits of 5 × 10−35 cm2 and ≈ 2 × 10 −34 cm2 on the production cross sections for superheavy elements with 2 h ≦ Tsf ≦ 1 y and 2 h ≦ Tα ≦ 10 d, respectively.

The electrolytic deposition of the hydroxides of rare earth and transplutonium elements on nickel holders from α-hydroxyisobutyrate solutions of 10−5 M to 5·10−1 M concentrations has been investigated in the presence of ammonium chloride. It is shown that at total concentrations of ≥10−12 M of rare earth and transplutonium elements, their electrodeposition proceeds with a 90% yield.

Zusammenfassung Läßt man Wasserstoffperoxid auf eine saure RuO4-Lösung einwirken, dann bilden sich je nach Arbeitsbedingungen Ruthen(III)- oder -(IV)-Ionen. Es wird ein Verfahren beschrieben, nach dem man auf relativ einfachem Wege solche Ruthenlösungen durch Papierelektrophorese charakterisieren kann. Das ist besonders für die Untersuchung trägerfreier radioaktiver Lösungen bedeutsam.

Using nuclide Ru-106 the extraction of ruthenium by some usual organic reagents and various solvents has been studied with the aim to obtain informations on the complex chemical behaviour of ruthenium(IV) in diluted solutions and on the mechanism of the extraction. A characteristic of ruthenium(IV) species in solution is its reaction inertia which manifested itself in the influence of reaction time and temperature on the distribution ratio. It has been established, that with the most varied of reagents ruthenium(lV) forms stable complexes even in acid aqueous solutions, which may prevent a precipitation of the hydroxide or losses through the adsorption of the radiocolloides and permit an extractive separation of micro ruthenium quantities from aqueous solutions with yields of more than 90%.

In bombarding209Bi and207, 208Pb targets by55Mn and58Fe ions the yields of “cold fusion” reactions have been determined using a sensitive technique for detectingT 1/2≧1 ms spontaneous fission and theα-decay of heavy actinide elements. It has been shown that theA = 263–265 isotopes of element 108, including the even-even isotope264108, undergo mainlyα-decay. The obtained results, together with the known data on the properties of the isotopes of elements 104 and 106, provide evidence for the enhanced stability of theZ=108 nuclei against spontaneous fission.