V.P. Perelygin

Ternary fission produced in Au, Bi, Th and U with Ar ions

Abstract Ternary fission of Au, Bi, Th and U induced with 230–380 MeV Ar ions is studied using a 2 π geometry. Thin layers of heavy elements made by evaporation on the surface of mica detectors are irradiated with heavy ions. The fission fragment tracks are revealed separately after a heat treatment followed by etching. The observed ratio of ternary fission to binary fission increases with the energy of Ar ions and with Z 2 / A of the compound nuclei. Angular distributions and the length of the fission tracks are reported.

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.

Research on variation of radon and gamma-background as a prediction of earthquakes in the Caucasus

For prediction of earthquakes in the Caucasus, a network of measurement sites for radon and gamma-background is established. The sites are established in the galleries of Krasnodar and Stavropol regions. The setups of measuring gamma-background and Rn in the soil air were built in galleries near settlement Kholmsky. The detector of Rn in soil operates in the gallery near Pyatigorsk. Gamma-setup is being mounted. Moreover, solid state nuclear track detectors (SSNTD) are operating in several points, including a mud volcano. They are exchanged every month. The preliminary data show correspondences between background radiation levels, and seismic and atmospheric phenomena.

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.

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.

α-Particle track investigation of the Chernobyl Nuclear Power Plant accident region soil samples

Abstract Results of α-particle track studies (Radiat. Meas. 25(1–4) (1995) 413; Radionuclides and Heavy metals in Environment, Vol. 5, 2001, Kluwer Academic Publisher, Dordrecht) indicate that the surface (⩽5 cm ) layer of the soil in the Chernobyl Nuclear Power Plant (NPP) accident region consists of thinly dispersed radionuclides and highly-radioactive “hot” particles (HPs). The latter contain nearly 2/3rds of the total α-activity of the contaminated soil. In the present report, the new results of continued HP α-activity characteristics are presented. The chief attempt made was to investigate size–frequency vs. α-activity distribution of HPs of size fraction ⩽10– 100 μm . For the Hp-aggregates with ∼100– 1000 μm sizes, α-radio-nuclide heterogeneity was established. This is probably the result of formation of HP-aggregates during the second stage of the NPP accident process: in these HPs the presence of not only U and fission products of “fuel” origin has been revealed, but also of terrestrial matter components.

Transmutation studies using ssntd and radiochemistry and the associated production of secondary neutrons

Abstract Experiments using 1.5 GeV, 3.7 GeV and 7.4 GeV protons from the Synchrophasotron, LHE, JINR, Dubna, Russia, on extended Pb- and U-targets were carried out using SSNTD and radiochemical sensors for the study of secondary neutron fluences. We also carried out first transmulation studies on the long-lived radwaste nuclei 129I and 237Np. In addition, we carried out computer code simulation studies on these systems using LAHET and DCM/CEM codes. We have difficulties to understand rather large transmutation rates observed experimentally when they are compared with computer simulations. There seems to be a rather fundamental problem understanding the large transmutation rates as observed experimentally in Dubna and CERN, as compared to those theoretical computer simulations mentioned above.

Fission track age and cooling rate of the Marjalahti pallasite

Abstract Nuclear tracks were studied in olivine and merrillite (phosphate previously called whitlockite) from the Marjalahti pallasite. The merrillite contains an important fission contribution due mainly to the spontaneous decay of now extinct 244 Pu. The U contents of 29 merrillite grains range from 60 to 140 ppb (median value: 85 ppb). Assuming a reasonable fractionation temperature of ∼ 1750 K for the pre-pallasitic material, a lower limit of ∼ 5 K/Myr is obtained for the cooling rate, in strong contrast with the previous metallographic result (∼ 0.5 K/Myr). This disagreement, together with those observed in the case of mesosiderites, strengthens the need for a revision of the metallographic method of retracing the cooling histories of meteorites, as suggested by Narayan and Goldstein [31].

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.

Studies on neutron production in the interaction of 7.4 GeV protons with extended lead target

Abstract A cylindrical lead target of diameter 8 cm and length 20 cm was irradiated with 7.4 GeV protons along the axis of the cylinder. The lead target was surrounded with a paraffin layer of thickness 6 cm to moderate the neutrons produced in p + Pb reactions. The spatial distribution of the slow and fast neutrons on different surfaces of the moderator were determined using LR 115 2B detectors (through 10 B(n,α) 7 Li reactions) and CR39 detectors (through proton recoils) respectively. Such results can be valuable in the studies and design of Accelerator Driven Subcritical Nuclear Reactors and Nuclear Waste Incinerators.