[en] Abstract only

[en] Radiation-chemical modification of timber improves the mechanical quality and the biological stability. Timber of beech, poplar, alder, fir, oak, and pine trees is soaked with polymer-forming compounds as vinylacetate, methylmethacrylate, styrene, acrylonitrile or monomer mixtures and then irradiated by ₆₀Co ß-rays. The total conversion of the monomer soaked in timber depends mainly on the chemical nature of the modificator and the integral irradiation dose. Data on static hardness, pressure strength, impact strength, static bending strength, and humidity of modified timber are given

[en] The aim of this study was to ascertain the degree and direction of those changes in physicochemical characteristics of irradiated peaches and grapes which determine their quality after irradiation and during storage. The following main conclusions are made: irradiation with doses of 200 to 300 krad does not cause significant alterations in the chemical composition and physicochemical characteristics of peaches and grapes; irradiation has a direct effect on the consistancy of peaches and grapes, leading to their softening which is proportional to the radiation dose used; radiation treatment is advisable in the case of peaches and grapes in tended for short-term rather than long-term storage at low temperatures

[en] Abstract only

[en] The objective of the study is to clarify the seismic adequacy of already installed fluid operated valves (FOV) in operating WWER-1000 MW type NPP. The approach is a combination of the earthquake experience based SQUG GIP methodology and analysis applying ASME code. The plant specific floor response spectra and the as-built conditions are taken into account. As a result of the study 86% of the FOVs are qualified for Review Level Earthquake (RLE), for 2% of the FOVs is prescribed upgrading and for 12% of the FOVs is recommended changing with seismically qualified ones. Based on Safety Analysis Report additional conclusions are made for the FOV, recommended for changing. (authors)

[en] Determination of the content of ²¹⁰Po and ²¹⁰Pb in tobacco leaves of different seasoning (age) - green leaves and after 4 and 8 months seasoning - showed that ²¹⁰Po in tobacco leaves increases with time, in accordance with its deposition, as a result of ²¹⁰Pb breakdown. These data show that the amount of ²¹⁰Po entering the leaves is negligible and that the basic source of ²¹⁰Po in tobacco leaves is ²¹.H0Pb. (author)

[en] Content of polonium 210 was studied in the leaves of six varieties of Bulgarian oriental tobacco according to their class. Tobacco that had to be examined was kept for more than three years for equilibrium between polonium 210 and lead 210 to be reached. Tobacco leaves of higher classes contained smaller quantities polonium 210 compared with those of lower classes (III-V classes). This is due to leaves of the upper and middle parts of the plant with a shorter vegetation period belonging to higher tobacco classes; radionuclide penetration by the root. The established divergence from this relationship was due to some other reasons such as mechanical damage, etc. (A.B.)

[en] In order to estimate the reduction dose rates of J¹³¹ absorbed by thyroid glands after preliminary administration of several chemical protectors, the experiments on 210 male Wistar rats were carried out. The protectors AET, VVR-2721, cysteamine hydrochloride, serotonin, creatine sulfate and Adeturon were applied intraperitoneally and after different periods of time J¹³¹ was introduced via stomach sounding . The results were shown as measured absorbed doses as well as calculated thyroid gland protection coefficients (PC). In all cases a sharp reduction of the absorbed doses in the first minutes after applications was found. The maximum PC of about 50-55% for serotonin, cysteamine and VVR-2721 was obtained. The protection effect gradually died down in the longer periods of time and practically it was missing in all cases in the 24th hour. The protection effect of radioprotectors was evaluated as unessential even in the most favourable cases

[en] Non-oriented films prepared from EVA-iPP and LDPE-iPP blends, irradiated with fast electrons, have been examined by thermomechanical analysis (TMA) and some mechanical properties (tensile strength and elongation at break) have been determined. The irradiation was carried out at low doses (5-12 Mrad) which brings about the formation of 50-60% gel content in the material. The thermomechanical curves of the irradiated films exhibit a plateau of a high elastic material after the segregation melting of the components, whose elastic modulus E depends on the composition and the irradiation dose D. The density of cross-linking, evaluated qualitatively from E, increases with increase of D and the increase of the EVA and LDPE contents in the blends. The tensile strength does not depend on the blend composition and the dose, while the elongation at break decreases with increase of D. The peculiarities in the dependence of the thermomechanical and mechanical properties on the dose and the composition have been explained by the formation of a statistical network with a broad distribution of the lengths between cross-links. The properties of the samples depend on the density of cross-linking, which is determined in turn by the balance between cross-linking and scission in the separate components. (author)

[en] The efficiency of potassium iodide in combined internal and external irradiation with iodine 131 introduction in relation to age, external irradiation dose and time following the contamination was estimated. Experiments on 300 female Wistar rats were carried out. Three doses of external irradiation (87, 260 and 435 cGy) of 5,42.10^-4 ± 3% A/kg were applied. J¹³¹ of 37 kBk/animal was introduced via stomach sounding at the 24th hour, 4th and 10th day after the irradiation. The stable iodine (KJ) was also orally introduced by 5 mg/kg b.w., 5 min after the contamination. The control groups were treated only with J¹³¹ and KJ. In all cases the potassium iodide application reduced the dose absorbed by the thyroid gland in two orders which corresponded to the literature data in cases without irradiation. The evaluated thyroid gland protection coefficient was 98-99%. These results were valid both for the young and the old groups, as well as for the whole period of maximal reaction of the organism. on the external irradiation. The efficiency of the preparation was independent on the external irradiation dose to be examined. The high toxicity of the iodine isotopes and the efficiency of the potassium iodide for thyroid gland protection at combined injuries show the advisability of the preparation under these conditions, too