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Conclusion Analysis of the state-of-the-art of the scientific and engineering aspects of the development and application of nuclear membranes shows that rapid progress has been made in the quantitative and qualitative respects. Fields where the use of nuclear membranes is particularly effective have now been determined. Nuclear membranes with pores measuring 0.5–1 µm in size are used extensively for analytical purposes in physicochemical studies and in biological and medical experiments. Membranes with pores of diameter 0.1–0.2 µm are used to make filters for fine purification of technological materials in the fabrication of semiconductor devices. Structures with the smallest pores (<0.1 µm) are used in the technique of thorough gas treatment and in the microbiological industry. The demand for nuclear membranes will rise rapidly. In view of this, it is important to develop and build customized accelerators for the mass production of high-quality filtration material.

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 thea/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.

Conclusions When using antimony-beryllium neutron sources for activation analysis of the composition of a substance, the problem of the analytical monitoring of many elements can be solved with a limit of determination of 10-3–10-5%. Based on the data obtained by the authors concerning the spatial distribution of the neutrons from a124Sb-Be-source in different moderators, a beryllium-graphite assembly with a powerful124Sb source has been designed, manufactured, and introduced into operation, for neutron-activation analysis.

A study is made for the search of superheavy nuclei in Marjalahti, Eagle Station and in other pallasite olivines. The olivine crystals are calibrated for heavy ion track lengths by using heavy ion beams from cyclotrons. The calibration for ultra heavy ions which are presently not available with sufficient energy to produce volume tracks in olivine crystals, is based on Katz and Kobetich model of track formation. The length spectrum of volume tracks, revealed by puncturing them with focussed Nd-glass laser beam, is measured and the abundances of different nuclei groups are calculated. Partial annealing has been used at 430°C for 32 hr which eliminates the interfering tracks due to nuclei of atomic numberS≤ 50. During the scanning 4 cm3olivine crystals, about 360 long tracks of uranium group as well as two very long tracks have been found. If these tracks belong to superheavy nuclei, the relative abundance of super heavies is found to be 6 × 10−11in galactic cosmic rays.

During December 1987 a microtron was put into operation at the Central Institute of Isotope and Radiation liesearch Leipzig. The maximum electron energy and current planned amounts to 25 MeV and 10 … 20 μA, respectively. After few weeks of operation an energy of 17 MeV was obtained. After conditioning the accelerator will be used preferably for activation analysis and radionuclide production. Some important components of the accelerator and possible applications are briefly discussed.

Neutron activation analysis consists of irradiating the samples of rock, ore, or concentrates to be analyzed with (Po-Be)-sources and then measuring the induced activity with scintillation and other counters. A method was developed for measuring aluminum, manganese, vanadium, and indium in ores of complex composition with reasonable concentrations of these elements. The use of its short-lived isotope as an indicator of the element determined makes it possible to achieve a rapid analysis method. The great sensitivity and accuracy of the method makes its application promising.

In experiments on the irradiation of Pu242 and Pu239 with O16 and O18 ions in the extracted beam of the 310-era cyclotron of the Joint Institute for Nuclear Research, isotopes of 102254, 102253 and 102252 have been synthesized. Their properties are given below: Isotope T1/2, sec Ea, meV 102254 75±15 8.11±0.03 102253 95±10 8.01±0.03 102252 4.5±1.5 8.41±0.03

The isotopes Fm247, Fm247m and Fm246 were synthesized in the extracted beam of the 310-cm heavy-ion cyclotron in the Joint Institute for Nuclear Research by irradiating Pu239 with C12 ions. ]he procedure of collecting the recoil atoms by means of gas jets is used, with subsequent recording of their ~- decay with Si(Au) detectors. For the isotope Fm247, a-activities are obtained with two different half-lives - one with two obviously complex groups of a-particles Ea=7.87±0.05MeV (~70%) and EEa=7.93±0.05 MeV (~30%), whose half- life is T1/2=35±4 sec; the other, with Ea=8.18±0.03 MeV has T1/2=9.2±2.3 sec. Data are confirmed concerning the properties of the isotope Fm246(Ea=8.25±0.03MeV and T1/2=1.6±0.4 sec), synthesized in 1966 at The Joint Institute for Nuclear Research.

The isotope 102254 was synthesized in the extracted beam of the OIYaI (United Institute of Nuclear Research) 150-cm cyclotron by means of the reaction Am243(N15, 4n) 102254. By recording the alpha disintegrations of the primary and daughter nuclei, it was shown that the half-life of this isotope is between 20 and 50 sec, while the energy of its emitted alpha particles is 8.10±0.05 MeV. These figures disagree with the literature data (T1/2=3 sec, Eca=8.3 MeV).