Leaching of 137 Cs, 90 Sr, and 239+240 Pu from products of underground nuclear explosions in tunnels 504R, 148/5, and 190 of the Semipalatinsk test site was studied. Samples were taken from central zones of the explosions. Sample characteristics are presented. Leaching experiments were performed in the batch and dynamic modes. The degrees and rates of 137 Cs, 90 Sr, and 239+240 Pu leaching with granite aqueous extract were determined. The leach rates determined in batch experiments are in the following ranges: 90 Sr 2.g cm -2 day -1 , and those determined in dynamic experiments are in the following ranges: 90 Sr 9.2 × g cm -2 day -1 . The values obtained are close to those reported in the literature for vitrified radioactive wastes.A series of underground nuclear explosions (UNEs) were performed in the period from 1961 to 1990 on the Semipalatinsk test site (Kazakh SSR, now Kazakhstan) both for nuclear weapons tests and for peaceful purposes [1].A UNE performed in a rock massif leads to the formation of a cavity, which, as a rule, collapses soon and becomes filled with crushed rock. The fission product fraction occurring in the gaseous state or in the form of volatile compounds is fixed in crushing and cracking zones, usually on the surface of cracks. In contact with water, these species pass into solution first.In the lower part of the cavity, there is molten rock containing the major fraction of high-melting radionuclides produced by UNE. The rate of the melt solidification depends on many factors, one of which is the moment of collapse of the cavity dome.In UNE in aluminosilicate rocks, more than 99.5% of high-melting radionuclides present in the solidified melted rock, as a rule, are not leached with water, and thus the explosion itself stabilizes radioactive elements in the form of a vitrified mass. However, when explosions were performed in carbonate rocks and in some rock salt deposits, the explosion products may be less resistant to leaching.UNEs lead to strong deformation of rocks with the formation of numerous crushing zones, downfall pits, and gaping cracks. As a result, the rocks become considerably more permeable, the descending filtration is enhanced, and surface water drainage is partially converted to underground drainage. UNEs give rise to a new type of underground waters, so-called tunnel waters, combining flows of crack-vein and crack waters and flows from atmospheric precipitation filtration zones. When underground waters get into the explosion cavity, contact of the solution with the crushed rock in the collapse zone and with the solidified melted rock will result in water contamination with radionuclides due to leaching. The contaminated underground waters can either replenish the underground water basin or flow out to the diurnal surface in the region of tunnel portals and then migrate over the diurnal surface.

A method was developed for determining radioactive Kr and Xe isotopes in air using liquid technical-grade oxygen prepared at air-separation plants. Kr and Xe are less volatile air components than N 2 and O 2 and are therefore accumulated in liquid oxygen in the course of its production. The method allows determination of background volumetric concentrations of Kr and Хе at short distances (~100 km) from the sources of radioactive noble gas (RNG) injection. The results of 85 Kr and 133,135 Xe monitoring in air of St. Petersburg in 2006-2008 are presented. For some air samples taken in St. Petersburg, back trajectories of the transfer of air masses were calculated, using HYSPLIT dispersion transport model developed by ARL, to determine possible sources of injection of Хе and 85 Kr radionuclides. Keywords: radioactive noble gas monitoring, volumetric concentrations of krypton and xenon isotopes in air, liquid technical-grade oxygen, transfer of air massesAn efficient method for monitoring safe operation of plants of nuclear power engineering is monitoring of gas-aerosol discharges in zones of location of such objects. In so doing, data on the concentrations of Хе and Kr in air are very valuable and bear important information. Direct isolation of Kr and Хе from air is very difficult, because their weight fraction in air is low: 1.14 × 10 -4 and 0.87 × 10 -5 vol %, respectively. Therefore, to determine background concentrations of Kr and Хе radionuclides, it is, as a rule, necessary to process large (no less than 5 m 3 ) air samples. These problems can be overcome by using those products from air-separation plants in which Kr and Хе are concentrated. A Kr-Xe mixture produced as by-product in oxygen production at metallurgical plants or liquid oxygen produced on smaller but more widespread airseparation plants can be used for this purpose. For monitoring of Kr and Хе radionuclides in St. Petersburg in 2006-2008, we used liquid technical-grade oxygen produced at an air-separation plant in the northern part of St. Petersburg near the Khlopin Radium Institute site.RNG adsorption on an inorganic sorbent, subsequent desorption, and transfer of Kr and Хе into a measuring ampule.Liquid oxygen samples were taken into a 5-l Dewar vessel from the liquid oxygen pouring system. Then the sample was delivered to a laboratory and processed into a spectrometric sample. The procedure was as follows: first step, gasification of liquid oxygen and sorption of Kr and Хе on an inorganic sorbent; second step, desorption of Kr and Хе from the inorganic sorbent and their transfer into a spectrometric ampule.Liquid oxygen gasification was performed in a specially fabricated gasifier. It was a ~1-l cylindrical metallic vessel with two welded-in gas-outlet pipes and a hole with a threaded stopper for filling with liquid oxygen. For gasification, liquid oxygen was poured into the vessel from which it spontaneously evaporated without special heating. With the progress of evaporation, oxygen was intermittently added into the gasifier until the oxyg...

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