[en] The leaching of Ra-226 from U mill tailings consolidated with cement and cement plus clay and/or peat may be described by a plane source diffusion model or a simultaneous first order reaction and diffusion model. A useful quantitative measure of the effectiveness of the consolidation process is the magnitude of the effective diffusion coefficient relative to that of the unconsolidated tailings material. The lowest effective diffusion coefficient upon consolidation was for consolidation with cement and peat. (orig.)

[en] The utilization of construction and demolition waste materials for the radionuclide immobilization by sorption processes was investigated. Given that the liquid radioactive waste usually has a complex composition and that effects of competition may significantly influence the efficiency of the treatment, the Simplex Centroid experimental design was used to explore ions sorption from multi-component solutions. For the purpose of this study, the common components of construction and demolition waste, such as pathway concrete and different bricks samples, were used along with the multi-component Sr2+, Co2+, and Ni2+ ions solutions. The equations for the prediction of metal ions sorption capacities were derived. The coefficients that correspond to the linear and interaction terms were obtained using a special cubic model. Likewise, by analysis of variance, statistically significant terms of the obtained polynomial were defined. The investigation has shown that the most effective sorption was onto the pathway concrete for all three cations, while the highest sorption capacity was found for Co2+ ions. Also, it has been determined that concerning Sr2+ ion removal there was a competition with coexisting Co2+ and Ni2+ ions, reducing its sorption capacity, while sorption of Co2+ and Ni2+ occurred more independently on other cations in multi-component solutions. Based on the obtained results, the applied experimental design can be efficiently used for the description of competitive sorption process and could be a powerful tool for the prediction of cation immobilization in liquid radioactive waste treatment.

[en] The experiment was carried out on a group of 10 carp receiving the soft tissue of previously contaminated lymnaea as food. Ingestion by carp of 45 daily rations, distributed over a 63-day period, resulted in a low retention of the radionuclide. The contamination kinetics showed that the steady state should be reached after only 225 days. The ⁶⁰Co transfer factor was approximately 10⁻² and the retention factor about 3.3 x 10⁻³. During the depuration phase, radiocobalt elimination by the carp developed in accordance with an exponential model based on the existence of two biological half-lives of 1.5 and 35 days which indicate a high Co turnover. During both phases of the experiment, urinary and branchial excretion appeared to be higher than faecal excretion

[en] The reduction of aqueous nitrates by suspended N-heptane is investigated under irradiation with a strong unfiltered UV source. Chemical changes are monitored using time-curves of nitrite and ammonium formation in the aqueous phase. Those kinetics suggest overall reactions which involve free radicals and take place over a wide range of NO₃^- concentrations, temperatures, pH and light intensity. The research is aimed at a better understanding of some photoprocesses which occur on heterogeneous aerosol substance, in areas polluted by either natural or man-made particulates. (Auth.)

[en] The concentration of medically used radionuclides has been studied in sludge from the sewage treatment plant serving the borough of Malmoe. In this area all nuclear medicine procedures are carried out in one hospital and almost all patients live in the borough. Therefore, the input of medically used radionuclides into the sewage system can be estimated with good accuracy. Samples of digested sludge have been taken once or twice a week during half a year. Iodine-131 (physical half life (T) = 8.05 d) was detected in all samples. The ¹³¹I-activity concentration due to medical use varied between (0.03 +- 0.01) and (0.12 +- 0.02) nCi kg^-1. The ratio between the total output of ¹³¹I via the sludge and an adherent input of the radionuclide into the sewage system was determined to (2.6 +- 0.6) X 10^-3, which is equivalent to a ratio of (2 +- 1) X 10^-2 for stable I. Occasionally measurable activities of ¹⁹⁸Au (T = 2.7 d) and ²⁰¹Tl (T = 3.1 d) have been found. The radioactivity concentration of medically used radionuclides in the sludge is low and constitutes no health problems for the persons involved. The sludge however has proved to be a very sensitive and suitable integrator of radioactive material released from a large urban area. (Auth.)

[en] In order to study the transfer of ¹²⁹I from soil into rice, tracer experiments have been carried out in the soil-rice plant system. The soil-plant transfer factors, which are defined as ‘concentrations of the nuclide in a plant organ’ divided by ‘concentrations of the nuclide in dry soil’, were 6.0 × 10⁻³ for brown rice, 3.2 for the first leaf blade (flag leaf), 5.1 for the second leaf blade, 2.6 for stem, 1.4 for rachis and 9.0 for root on a dry weight basis at the time of harvest. The ratio of radio-iodine in brown rice to polished rice was about 1:0.3. The transfer factor of radio-iodine from soil to polished rice was estimated to be about 2 × 10⁻³. It was observed that the concentration of radio-iodine in the soil solution increased with the plant growth. This was attributed to the reduced condition in the soil caused by the effects of root and/or micro-organisms. Release of I from rice plants into the air in an organic form was found. The chemical form of radio-iodine in the soil solution appeared to be iodide, and the radio-iodine in the plant tissue was found in a low molecular weight fraction by gel-filtration. The vertical distribution of radioiodine in the soil was also studied

[en] In order to evaluate Cobalt 60 behavior in freshwater ecosystems, two food chains including different nutritionally interdependent species in a natural environment were defined. This article covers the dynamics of water-borne contamination in the species. (Auth.)

[en] A laboratory study with Selenastrum capricornutum has shown that the interpretation of C-14 uptake data can be influenced by the method of data presentation. The expression of C-14 data as rate of uptake rather than total uptake is more representative of the algal stimulation potential of the medium being investigated. Also, data expressed as a rate of uptake based on a four-hour incubation period are more sensitive to changes in algal activity than those based on rate of uptake for long-term incubation periods. Several examples are discussed where data were initially interpreted as showing stimulation, although conversion of the data to rate of uptake shows a lack of stimulation. (Auth.)

[en] Radiation protection planning in urban areas after a radioactive fallout requires knowledge of decontamination caused by storm water transport. The transport of 137Cs from a roof and three storm sewers was measured in Uppsala (Sweden) during the first rainfall since the contaminated rainfall from Chernobyl on 29-30 April 1986. Runoff and concentration of 137Cs in storm water were determined with an accuracy of 10 to 15%

[en] Recent research on the photoreduction of aqueous nitrite by suspensions of some organic compounds is extended to solutions of inorganic nitrates. With analogy to previous work, formation of ammonium in the aqueous phase is found to occur. However, the related kinetics strongly depend on several concurrent reactions of nitrite, such as its decomposition, its further reduction and its attack onto the organic substance. With further analogy to the work carried out in a nitrous medium, there also is formation of diverse organic derivatives, their yields being larger by a factor of 2 to 4 at those experimental conditions. (Auth.)