Boron determination in blood and tissue samples is a crucial task especially for treatment planning, preclinical research, and clinical application of boron neutron capture therapy (BNCT). Comparison of clinical findings remains difficult due to a variety of analytical methods, protocols, and standard reference materials in use. This paper addresses the comparability of inductively coupled plasma mass spectrometry, quantitative neutron capture radiography, and prompt gamma activation analysis for the determination of boron in biological samples. It was possible to demonstrate that three different methods relying on three different principles of sample preparation and boron detection can be validated against each other and yield consistent results for both blood and tissue samples. The samples were obtained during a clinical study for the application of BNCT for liver malignancies and therefore represent a realistic situation for boron analysis.

At the Paul Scherrer Institute (PSI), a very intense source of ultracold neutrons (UCN) is being built. The UCN converter of solid deuterium must be contained in a vessel. Produced UCN leave that vessel through its top lid. To decide on the design of the vessel and the top lid, we have measured the transmission of neutrons with velocities between 3 and 20 m/s through different material foils. Contrary to expectations, we found that transmission through aluminium and aluminium alloys is equal or even higher compared to zirconium and reactor-grade zirconium alloys, respectively.

To prepare electrodeposition experiments with superheavy elements (SHE), their homologs were investigated. In the experiments, various electrode materials and electrolytes were used. Critical potentials (E-crit) where the electrodeposition starts and potentials for the deposition of 50% of the atoms in solution (E-50%) were determined. Underpotential deposition was observed in most cases. An electrolytic cell for a fast electrochemical deposition was developed and the time for the deposition of 50% of the atoms in solution (t(50%)) was determined. Short lived a-emitting isotopes were produced at Gesellschaft fur Schwerionen-forschung (GSI), Darmstadt, transferred to the aqueous phase with ALOHA (Automated Liquid Online Heavy element Apparatus), transported to an electrolytic cell and deposited on a palladinated Ni tape. It was shown that the coupling of devices for collection, electrodeposition, and alpha-spectroscopy is feasible and might be of great use in SHE chemistry.

For the speciation of the plutonium oxidation states in aqueous solutions, the online coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed. Depending on the radius/ electrical charge ratio, the oxidation states 111, IV, V, and VI of plutonium are separated by CE, based on the different migration times through the capillary and are detected by ICP-MS. The detection limit is 20ppb, i.e. 10(9)-10(10) atoms (10(-12)-10(-11) g) for one oxidation state with an uncertainty of the reproducibility of the migration times of <= 1% and <= 5% for the peak area. The redox kinetics of the different plutonium oxidation states in the presence of humic substances (humic and fulvic acid) have been studied. A relatively rapid reduction of Pu(VI) (10 to 1000h) in contact with Gorleben fulvic or Aldrich humic acid could be observed, depending on the pH of the solution. Furthermore, at pH = 1, a reduction to Pu(Ill) and Pu(IV) in a mixture of all four oxidation states in contact with Gorleben fulvic acid after one month has been observed. In order to improve the sensitivity of the CE method, the offline coupling of CE to resonance ionization mass spectrometry (RIMS) has been explored. First applications of this new speciation method are presented.

Summary Two experiments aiming at the chemical investigation of element 112 produced in the heavy ion induced nuclear fusion reaction of 48Ca with 238U were performed at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, Germany. Both experiments were designed to determine the adsorption enthalpy of element 112 on a gold surface using a thermochromatography setup. The temperature range covered in the thermochromatography experiments allowed the adsorption of Hg at about 35 °C and of Rn at about -180 °C. Reports from the Flerov Laboratory for Nuclear Reactions (FLNR), Dubna, Russia claim production of a 5-min spontaneous fission (SF) activity assigned to 283112 for the 238U(48Ca,3n) 283112 reaction. Hence, Experiment I was designed to detect spontaneously fissioning (SF) isotopes of element 112 with half-lives (t 1/2) longer than about 20 s. 11 high-energy events were detected. 7 events exhibit a deposition pattern resembling a chromatographic peak in the vicinity of Rn deposition. However, the energy of the events observed in Experiment I was lower than expected for a SF-decay of 283112. Therefore, these events could not be unambiguously attributed to the decay of 283112. In contradiction with earlier publications newer reports from FLNR Dubna claim that 283112 decays by α-particle emission (E α = 9.5 MeV) with t 1/2 = 4 s followed by a SF-decay of 279Ds (t 1/2 = 0.2 s). Therefore, Experiment II was designed to be sensitive to both claimed decay properties of 283112. However, during this experiment neither short α-SF correlations nor SF coincidences were detected. The conclusion is that 283112 was not unambiguously detected, neither in Experiment I nor in Experiment II.

R. Eichler, W. Brüchle, R. Buda, S. Bürger, R. Dressler, Ch.E. Düllmann, J. Dvorak, K. Eberhardt, B. Eichler, C.M. Folden III, H.W. Gäggeler, K.E. Gregorich, F. Haenssler, H. Hummrich, E. Jäger, J.V. Kratz, B. Kuczewski, D. Liebe, D. Nayak, H. Nitsche, D. Piguet, Z. Qin, U. Rieth, M. Schädel, B. Schausten, E. Schimpf, A. Semchenkov, S. Soverna, R. Sudowe, N. Trautmann, P. Thörle, A. Türler, B. Wierczinski, N. Wiehl, P.A. Wilk, G. Wirth, A.B. Yakushev, A. von Zweidorf Paul Scherrer Institut, CH-5232 Villigen, Switzerland 1

SummaryHassium, element 108, was produced in the fusion reaction between26Mg and248Cm. The hassium recoils were oxidizedin-situto a highly volatile oxide, presumably HsO4, and were transported in a mixture of He and O2to a deposition and detection system. The latter consisted of 16 silicon PIN-photodiodes facing a layer of NaOH, which served, in the presence of a certain partial pressure of water in the transport gas, as reactive surface for the deposition of the volatile tetroxides. Six correlated α-decay chains of Hs were detected in the first 5 detectors centred around detection position 3. In analogy to OsO4, which forms Na2[OsO4(OH)2], an osmate(VIII), with aqueous NaOH, HsO4presumably was deposited as Na2[HsO4(OH)2], a hassate(VIII).

Summary Experiments with different oxidation states of Pu in GoHy-532 groundwater under reducing conditions reveal that Pu(VI) and Pu(V) are reduced rapidly to Pu(IV) at pH 7. The half-life of the redox reactions Pu(VI)/(V) and Pu(V)/(IV) are in the range of minutes. The rates of both reduction reactions decrease with decreasing pH values. A portion of the Pu(IV) is not stable in the same groundwater and is reduced slowly to Pu(III) in the range of weeks. Ultrafiltration experiments show Pu to be totally bound to the humic substances in the groundwater. At Pu concentrations of 10 -5 to 10 -4 M, most of the Pu occurs as a Pu-colloid and/or Pu-colloid bound to humic substances (Pu-colloid-HS) in solution, which is indicated by EXAFS/XANES and XPS measurements.

A. von Zweidorf1, R. Angert1, W. Brüchle1, S. Bürger2, K. Eberhardt2, R. Eichler1,3, H. Hummrich2, E. Jäger1, R. Jera2, H.-O. Kling2, J. V. Kratz2, U. Krille2, B. Kuczewski2, G. Langrock2, G. Lehr2, M. Mendel2, A. Nähler2, A. Peil2, V. Pershina1, U. Rieth2, M. Schädel1, B. Schausten1, E. Schimpf1, H.-J. Schött1, E. Stiel1, P. Thörle2, N. Trautmann2, K. Tsukada4, N. Wiehl2, G. Wirth1 1Gesellschaft für Schwerionenforschung, Darmstadt, 2Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 3now at PSI, Villigen, 4JAERI, Tokai In October/November 2002, after an intensive optimization of many experimental parameters, the CALLISTO-project finally led to a hassium chemistry experiment [1] at the UNILAC. Since it has been predicted, that hassium forms a volatile tetroxide [2], which was recently confirmed by C. Düllmann et al. [3], we decided to investigate this compound of hassium. For the very volatile OsO4, it is known that it dissolves in strongly basic alkali hydroxide solutions thereby forming red, diamagnetic osmates(VIII) of stoichiometry [OsO4(OH)2]. In previous beamtimes, in which OsO4 was produced in-situ directly behind the target [4], we demonstrated, that the volatile OsO4 deposits effectively on NaOH surfaces from humid He gas. This behaviour was used to design a continuously working system for the formation, transport, deposition and detection of OsO4 and HsO4 [1]. This system, which uses 4 computercontrolled valves and 4 detection arrays, each with 4 alphadetectors [5], combines the advantages of a continuously operating system and adds the possibility to change the deposition material, a thin layer of NaOH on a plate of stainless steel, on a regular basis without interrupting the experiment. Changing the deposition material is necessary, as the deposition efficiency decreases with time [1].

Capillary electrophoresis (CE) was coupled to ICPMS in order to combine the good performance of this separation technique with the high sensitivity of the ICPMS for the analysis of plutonium and neptunium oxidation states. The combination of a fused-silica capillary with a MicroMist AR 30-I-FM02 nebulizer and a Cinnabar small-volume cyclonic spray chamber yielded the best separation results. With this setup, it was possible to separate a model element mixture containing neptunium (NpO2(+)), uranium (UO2(2+)), lanthanum (La3+), and thorium (Th4+) in 1 M acetic acid. The same conditions were also suitable for the separation of various oxidation states of plutonium and neptunium in different aqueous samples. All separations were obtained within less than 15 min. A detection limit of 50 ppb identical with 2 x 10(-7) M (3-fold standard deviation of a blank) was achieved. To prove the negligible disturbance of the plutonium and neptunium redox equilibria during the CE separations, plutonium and neptunium speciation by CE-ICPMS in acidic solutions was compared with the results of UV/visible absorption spectroscopy and was found to be in good agreement. The CE-ICPMS system was also applied to study the reduction of Pu(VI) in a humic acid-containing groundwater at different pH values.

Summary 27-s 263Db was produced in the 249Bk ( 18O, 4n) reaction at 93 MeV. The activity was transported by a He/KCl-jet to the laboratory where it was collected for 15 min and then subjected to a chemical separation specific for group-4 elements. The activity was dissolved in 0.5 M unbuffered α-HiB and eluted from a cation-exchange column. The effluent was made 9 M in HCl and group-4 tetrachlorides were extracted into TBP/Cyclohexane which was evaporated to dryness on a Ta disc. The Ta discs were assayed for α and SF activity. A SF activity with a half life on the order of 20 min was observed and assigned to the nuclide 263Rf. It is formed by electron-capture decay of 263Db with a decay branch of 3+4 -1%.

A. von Zweidorf1, R. Angert1, W. Brüchle1, S. Bürger2, K. Eberhardt2, R. Eichler1,3, H. Hummrich2, E. Jäger1, R. Jera2, H.-O. Kling2, J. V. Kratz2, U. Krille2, B. Kuczewski2, G. Langrock2, G. Lehr2, M. Mendel2, A. Nähler2, A. Peil2, V. Pershina1, U. Rieth2, M. Schädel1, B. Schausten1, E. Schimpf1, H.-J. Schött1, E. Stiel1, P. Thörle2, K. Tsukada4, N. Wiehl2, G. Wirth1 1Gesellschaft für Schwerionenforschung, Darmstadt, 2Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 3now at PSI, Villigen, 4JAERI, Tokai It has been predicted [1] and confirmed [2], that hassium forms a volatile tetroxide. The first attempt to study a chemical reaction of this compound, and to learn more about the chemical behaviour of Hs, is described in a companion contribution [3]. For this purpose, CALLISTO [4] has been developed in recent years. This system, which is in principle gas chemistry using reactive surfaces, was completely redesigned to integrate all the results of the many preliminary experiments. The volatile tetroxide is formed in-situ in the target chamber, where the recoils are stopped in the jet gas (a mixture of 1 l/min He and 0.1 l/min O2)[5]. At the exit of the target chamber, the gas flow passes a quartz glass tube containing a quartz wool plug, both heated to 500 °C in order to complete the oxidation of osmium and hassium to the tetroxide. The gas is transported via a 13 m long PTFE capillary to the detection system. Because water seems to influence the deposition of OsO4 on the NaOH surface [6], it was necessary to introduce it into the chemical system. As H2O cannot be added before the He passes the target chamber (it prohibits an accurate beam current measurement), it was added after the target chamber and before the detection system. For that reason, a special moisturizing unit was designed for CALLISTO. It consists of a large, thermostated moisturizer [7], which continuously adds at a defined temperature (30 °C) water to a second helium jet (0.1 l/min with the option to use 0.05 2 l/min). This humidified helium passes through a declusterizer at 200 °C to evaporate all remaining water aerosols. Thereafter, the humidity of the gas was monitored with a dewpoint transmitter (~20 g H2O per kg gas). This moisturized helium is added to the jet gas from the target chamber, containing only a few ppm of water and resulting in a humidity of about 2 g H2O per kg gas in the final gas jet. This jet is then distributed through a system of 4 computer-controlled valves to 4 detection arrays (Fig. 1). During an experiment, the He gas is flowing through 3 detection arrays, whereas 1 detection array is cut off from the gas flow; it is in a “service mode” to change the deposition material. We used a thin layer of NaOH as a deposition material, which was prepared by coating plates of stainless steel with 1M ethanolic NaOH and by drying these plates. Every 60 minutes, the valves were automatically switched and the deposition plate of the detection array, being in the “service mode”, was manually changed, cleaned and recoated. Thus, a continuously working detection and deposition system was realized. The surface of the deposition material looses reactivity with time [6]. One possible explanation is, that NaOH is partially neutralized by CO2, which is an impurity of the used gases and probably formed by a reaction of the carbon beam dump with the oxygen of the jet gas, too. The Na2CO3 has a decreased reactivity and shows only a yield of about 50%, compared to NaOH. After the volatile oxides (OsO4, HsO4) are deposited, their αdecay and spontaneous fission can be detected with the detection arrays, each consisting of four (10x10) mm2 large PINdiodes facing the deposition material (Fig. 2).