[Radio-ecological situation in the area of JSC "Priargunsky Production Mining and Chemical Association"].

In order to assess the radioecological situation created in the area of the location of diversified uranium mining enterprise "Priargunsky Production Mining and Chemical Association" (PIMCU) there was investigated the radioactivity of a number of the compartments of environment, both at the industrial site and beyond it, as well as the volume activity of radon inside the ground and working premises. Radioecological situation in the vicinity of the uranium mines was performed in comparison with the background (fixed reference, control) district, where there is no uranium mining. Performed studies have shown the significant excess content of 226Ra, 232Th, 210Pb, 222Rn in soil, water open water bodies and local foods near uranium mines compared to areas outside the zone of influence of uranium mining that allows to make a conclusion about the significant technogenic pollution of local areas of the plant and adjoining territory.

Heavy particle fluxes in Salyut space station orbit.

Results of a detailed analysis of heavy ion fluences measured on the Salyut and MIR orbital stations from 1978 to 1990 are presented. The analysis has made use of new models that describe the cosmic ray fluxes and their transition through the magnetosphere. The penetration of solar cosmic ray particles to the orbit, the increase of the (Sc-Cr)/Fe flux ratio in the orbit, and the occurrences of 200-500 MeV/nucl heavy nuclei in <30 degrees latitudes have been analyzed.

Cosmic ray particles with different LET values under various thicknesses of shielding in low altitude orbits: calculations and Cosmos-2044 measurements.

Fluxes of cosmic ray particles with different LET values were measured on board the Cosmos-2044 biosatellite under various thicknesses of shielding by stacks of CR-39 and nitrocellulose plastic nuclear track detectors (mounted outside the satellite). The component composition of the particles detected under shieldings of 0.1-2.5 g cm-2 is verified by comparing experimental data with the results of model simulations of the fluxes of galactic cosmic ray particles and of radiation belt protons.

Charge state distribution of anomalous oxygen ions in low Earth orbit during solar quiescence.

A new method of evaluating the charge state distribution of cosmic ray heavy ions, using a measured ratio of particle fluxes observed in two different satellite orbits passing through the Earth's magnetosphere, is described. The measurements of heavy ions were performed simultaneously on the Cosmos 1882 (orbital inclination 82 degrees) and Cosmos 1887 (inclination 62.3 degrees) satellites during September-October 1987. Solid state nuclear track detector stacks were used for the registration of C, N, O and heavier ions. After comparing the data of the two experiments with theoretical calculations, the charge state of galactic and anomalous heavy ions was derived.

Reliability of trajectory identification for cosmic heavy ions and cytogenetic effects of their passage through plant seeds.

The potentially specific importance of the study of heavy ions from galactic cosmic rays for the understanding of radiation protection in manned spaceflight continues to stimulate spaceflight experiments in order to investigate the radiobiological properties of these ions. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of carcinogenesis as the primary radiation risk for man in space. An essential technical ingredient of such spaceflight experiments is the visual nuclear track detector which permits identification of those biological test organisms which have been affected by cosmic heavy ions. We describe such a technique and report on an analysis of the qualitative and quantitative reliability of this identification of particle trajectories in layers of biological test organisms. The incidence of chromosome aberrations in cells of lettuce seeds, Lactuca sativa, exposed during the Kosmos 1887 mission, was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced.

Radiobiological experiments with plant seeds aboard the biosatellite Kosmos 1887.

The effects of spaceflight factors on the seeds of Arabidopsis thaliana and Crepis capillaris were studied provided with various protective measures: the seeds were located inside the satellite and in open space, protected with aluminium foil and also exposed without the foil cover. When the seeds were in open space without any protection, their viability was found to be suppressed; the survival rate and fertility of plants grown from these seeds were also diminished. An increase in the frequency of chromosome aberrations (CA) and in the number of multiple injuries was registered in this case. Experiments with the aluminium foil shielding showed a decrease in the suppression of the seeds' viability, but mutational changes were found to be even more increased, while the survival and fertility of the plants decreased. An increase in the thickness of shielding resulted in a decrease in the effects up to the level of the control, except for the effects connected with CA and fertility of the plants. Analysis of the results shows that these impairments can be ascribed to the action of single heavy charged particles (HCP). The seeds can be thus regarded as an integral biological 'dosimeter' which allows estimation of the total effects of radiation, ecological and biological factors.

LET variation measurements behind different absorber thicknesses on COSMOS-1129 satellite.

LET variation with the absorber thickness was measured by plastic detectors exposed on COSMOS-1129 satellite.

Results of cosmic radiation dose field measurements aboard the "Salyut-6" orbital station.

During the 3rd main expedition on board the "Salyut-6" orbital station in 1979 the integral characteristics of cosmic radiation were measured in various positions inside the manned modules (experiment "Integral"). Measurements were performed with thermoluminescent dosimeters, photographic films and solid state plastic detectors supplied for the experiment by specialists of the USSR, Bulgaria, Hungary, GDR and Romania. The dose gradient inside the manned modules of the station amounted to 70% for long intervals of time. During the experimental period the dose rate inside the station was 15 to 30 mrad per day. The mean flux of particles with Z > or = 6 and LET > or = 200 keV/micrometer was found to be 0.22 cm-2 or day-1.

Radiobiological investigations in Cosmos 782 space flight (Biobloc SF1 experiment).

Several biological objects were flown in Cosmos 782 in order to investigate the effects of HZE cosmic particles and other environmental factors of space. Space flight results in chromosomic aberrations in lettuce seeds, decreased germination rate and increased frequency of abnormalities in tobacco seeds and decreased developmental capacity in Artemia eggs. In lettuce and tobacco seedlings, changes were observed not only in seeds hit by heavy ions but also in nonhit seeds. The results indicate that exposure to the space environment can induce important changes in biological objects and emphasize the usefulness of investigations carried out on organisms less complex than mammals.

Preliminary results of the Biobloc experiment on the Cosmos 782 flight: effects of cosmic rays on brine shrimp eggs and tobacco seeds.

The aim of the Biobloc experiment is to determine the biological effects of cosmic rays. Biobloc is a stack made up of biological layers and physical detectors (nuclear emulsions and plastic). Artemia eggs and tobacco seeds are used by French workers. Irradiation by cosmic heavy ions induces a late developmental inhibition of Artemia eggs. A light increase of emergence rate is observed for the non-hit eggs. The results are compared with those of previous space experiments. Investigations on tobacco seeds are in progress.