Yu. T. Chuburkov

Experiments on chemistry of element 104-kurchatovium—V: Adsorption of kurchatovium chloride from the gas stream on surfaces of glass and potassium chloride

Abstract The adsorption of kurchatovium chloride on surfaces of glass and potassium chloride was studied by a gas-solid chromatographic technique. The compound was shown to be similar in its properties to hafnium tetrachloride. More than 60 kurchatovium atoms were observed in these experiments by their spontaneous fission.

Man-made plutonium in environment — possible serious hazard for living species

Abstract It is pointed out that, contrary to the situation with natural Rn, the growing concentration of man-made Pu in environment — natural water soil plants and food — can provide the serious danger for all kind of animals and especially for mankind. Really, as it was established recently, element Pu is accumulated in human body during all the life and the dangerous concentration estimated to be 10 −12 – 10 −13 grapm Pu per gram of human tissues. Unfortunately up to now there are no simple nonexpensive methods of Pu determination at the level of sensitivity 10 −14 – 10 15 g/g which can provide the determination of Pu even in 0.2 g of human tissue. We warn that now the average concentration of Pu in human body is not less than 10 −14 g/g and much higher for some “hot” regions in Europe and Asia. We propose to discuss the problem of organizing world net exploration of Pu in environment — similarly to Rn exploration program — and personnel Pu monitoring for inhibitions of Pu damaged regions. Our approach to the problem is based on chemical separation of Pu, on determination of Plutonium by high fission cross section with thermal neutrons 239 Pu(n,f) reaction and by control of possible admixture of 235 U isotope by 238 U(γ, f) reaction in Pu preparations. The problem of increasing of sensitivity of Pu analysis up to 10 −14 – 10 −15 g/g is discussed in detail.

On the determination of low Pu content in the environment

Abstract The method of 239 Pu minor content determination in the soil, water, air, living species is developed. It is based on chemical extraction of plutonium from the specimens. The 236 Pu α-active tracer was used to control the chemical yield of Pu from samples. The layers with Pu were put in contact with polyterephtalate and irradiated with thermal neutron fluences ∼ 10 15 cm −2 together with calibrated U and P ethalons. The Pu content in soils from North Ukraina region was 310 -12 - 1.210 -13 g/g. To check the possible Th-U minor admixtures of U and Th in Pu fractions, the control experiments with 23 MeV γ-rays were carried out. It provides an upper limit of admixture of these nuclei at the level of ≤ 10 8 per sample.

Results of the searches for superheavy nuclei in the Cheleken Penninsula geothermal waters

The water rich in heavy volatile metals form the Cheleken Penninsula hot springs was passed through a column containing 850 kg of anion exchange resin. The spontaneous fission activity (SF) of the samples was measured by neutron multiplicity detectors. The counting rate of spontaneous fission events was 0.5 per day for 9 kg of saturated resin. After 170 kg of the resin had been treated with acid solutions and hydroxides had been precipitated from the eluate with alkali, the counting rate for the precipitate was about five per day. From measurements of theα/SF ratio it is concluded that the activity cannot be traced back to a contamination by actinides, except to a contamination by pure252Cf, which, however, seems to be unlikely. Thus the explanation of the observed effect as being due to the spontaneous fission of a new naturally occurring isotope of a superheavy element is considered to be the most probable one.

On the determination of subpicogram concentrations of Pu in environment and living species

Abstract The method of 239 Pu minor content determination based on subsequent activation with thermal neutrons and gamma-rays was applied for preparations chemically separated from soils, water, river sediments and some living species. The obtained level of sensitivity for routine analysis is proved to be equal 10 −13 gram Pu per gram of sample.

On the determination of and content in human tissues

Abstract The growing concentration of man-made Pu in natural environment—water, soil, plants and food can provide the serious danger for all kind of animals and especially for mankind. Actually, as it has been established recently, Pu is accumulated during the whole life and the dangerous concentrations are estimated to be 10 −12 – 10 −13 g of Pu/g of human tissues. We warn that now the average concentration of Pu in human body is not less that 10 −14 g/g and much higher for some “hot” regions in Europe and Asia. Here we present the data on 239 Pu and also 241 Am in human hair (Semipalatinsk region area) and in human gall stones of some samples from more “quiet” regions—Minsk (Belarus) and Krakow (Poland). At the measurements of 239 Pu concentration in human hair and gall stones it has been found that it varies from 10 −13 up to 3×10 −12 g/g for south part of heavily damaged Semipalatinsk nuclear bomb test site region. Further possible improvement of neutron–gamma activation analysis—up to the level of 10 −15 g/g of Pu in human tissues, based on application of ultra clean chemicals and track detectors and on selective extraction of U out of electroplated Pu layers in flow of chlorides at high temperatures are discussed. Such upgrading the method can allow one to use the specimens of human tissues as small, as 0.1– 0.2 g in the routine Pu analysis.

On problem of ultrasensitive determination of man-made plutonium in living species

Abstract To improve the sensitivity of the method of Pu determination in specimens we applied two additional steps of chemical separation of Pu from U. After the usual chemical separation of Pu we used second step with ion-exchange column, where the ions of U 4+ were absorbed by sorbent and Pu 3+ ions remains in solution. For converting Plutonium to Pu 3+ state the electrochemical procedure has been used. After the electrochemical separation procedure the solution was deposited onto quartz glass. Then the quartz glass plates were inserted into the gas mixture flow (SOCL 2 +air) at the temperature 650°C. Such a procedure extracts ≥90% U from Pu layer. Now we provide the chemical separation of Pu from U by a factor ≥10 7 . It means that now we are able to perform the routine Pu analysis at the level of sensitivity 10 −14 –10 −15 g/g. By using combined n-γ activation technique we can determine the Pu content in the small fragments of tissues of living species with the weight as small as 0,05-0,1 gram. The new technique could be used in routine analysis of Pu in population of heavily Pu damaged regions (Chernobyl, Ural Region, Semipalatinsk).

Experiments on chemistry of element 103 adsorption of chloride from the gas stream

Abstract Element 103 chloride was found to have similar adsorbability on solid surfaces, and hence volatility, as the chlorides of curium, californium, fermium and element 102 and to be much less volatile than kurchatovium chloride. These first experiments on the chemistry of element 103 performed with ∼ 300 atoms provide evidence that the element is ekalutecium.

On Search and Identification of Fossil Tracks dne to Superheavy Cosmic Ray Nuclei (Z ≥ 110) in Meteoritic Crystals

A new method for investigation of the ultra-heavy component of Galactic cosmic-ray nuclei (Z = 50 – 92) has been developed since 1980. It depends on the ability of extraterrestrial silicate crystals (olivine) to register and store during many million years the tracks due to cosmic-ray nuclei with Z ≥ 22. Our approach bases on the partial annealing of both “fossil” tracks and the tracks due to accelerated Kr, Xe, Au, Pb and U ions, and on the chemical etching of total volume track length of the cosmic-ray nuclei in the olivine crystals. The crystals taken from Marjalahti and Eagle Station pallasites (the radiation ages are 180 and 45 million years respectively) were annealed at 703 K during 32 h and etched. The volume tracks due to Z ≥ 50 cosmic-ray nuclei were then measured. The intercomparison of track length spectra of the “fossil” tracks and the tracks due to the accelerated 238U and 208Pb nuclei proves unambiguously that the last two abundant peaks of “fossil” track length spectra (120 – 140 μm and 180 μm, first observed in 1980 in Dubna) are products of the recent nucleosynthesis in our Galaxy due to Pt-Pb and Th-U groups of cosmic-ray nuclei. During 1980 – 1996 more than 1600 Th-U “fossil” tracks were measured and 11 anomalously long tracks (L = 340 – 370 μm) were found. Concerning the origin of the anomalously long tracks we have determined the orientation of these tracks in olivine crystal with the Laue-Roentgen method. We estabilished that five anomalously long “fossil” tracks have an angle ≥ 15° to the main crystal plane (010) and subsequently can not be attributed to any actinide nuclei in meteoritic olivine crystals. Moreover, in the fossil track study of olivines annealed at 703 K during 32 h we found the 250 μm – long track which could not be attributed to Th-U nuclei at any orientation in the crystal lattice. Now we can set an upper limit of Z ≥ 110 (superheavy) nuclei abundance at the level NZ μ 110 / NTh, U ≤ (1÷3) · 10−3. Our goal is to obtain the final, necessary and sufficient proofs of the existence of SHE nuclei in Galactic matter.

Thermochromatographic Determination of the Relative Volatility of Chlorides and Oxychlorides of Group IVb-VIb Elements

Thermochromatographic and gas-chromatographic experiments show that the recoil atoms of Group IV-VI elements (Zr, Hf, Nb, Ta, Mo, W) thermalized in inert gases (He, Ar) form in chloride systems both higher and lower chlorides and oxychlorides. The relative yields of these gaseous compounds depend on the experimental conditions.