A mathematical model is developed for the radiolysis of water vapor and water vapor to which molecular hydrogen and oxygen are added. The model is verified using existing experimental data on the radiolysis of water vapor in a wide range of temperatures and dose rates of ionizing radiation.In our country, we do not have certified software for calculating the consequences of normal and radiation-chemical processes in the first-loop coolant, which in the core is a two-phase system consisting of water vapor and liquid water and containing noncondensing gases, for reactor facilities with boiling water-moderated water-cooled reactors. The lack of such software is due to the complexity of the mathematical model of the thermal radiolysis of a two-phase system. Essentially, such a model is a superposition of three models which interact with one another -the radiolysis of liquid water, interphase mass transfer, and radiolysis of vapor with process additives. The first two models are now quite well developed, whereas there is no satisfactory model for the radiolysis of water vapor under the conditions of the core in a power reactor.The present work is devoted to developing a model of the radiolysis of water vapor and water vapor to which molecular hydrogen and oxygen are added and verifying this model on the basis of existing experimental data in a wide range of temperatures and dose rates of ionizing radiation.There are many works devoted to the radiolysis of water vapor under various conditions, but a mechanism suitable for describing its kinetics, specifically, the kinetics of the accumulation of stable products -hydrogen and oxygen -is described in detail only in [1,2]. It is this mechanism that was used as a basis for developing a model of the radiolysis of vapor and it was supplemented by reactions discussed in later works [3]. The set of elementary reactions, which is used for developing the model, and their parameters from [4] are presented in Table 1. The initial radiation-chemical yield of active particles of radiolysis of vapor and the yield from the decomposition of water, which were determined after the physicochemical stage of radiolysis has been completed, when purely chemical radical processes start to occur in the irradiated system, was assumed to be G H 2 = 0.5, G H = 7.4, G OH = 6.3, G O = 1.1, G H 2 O = 7.4 particles/100 eV. In accordance with the data in [3], it was assumed that the yield is independent of the irradiation conditions in a wide range of values of the external parameters -temperature up to 900 K, pressure from 10 4 to 10 6 Pa, absorbed dose rate up to 10 12 Gy/sec -and types of radiation -from γ rays to the fission products of uranium nuclei.Analysis showed that not all existing experimental results can be used to verify the mechanism describing the kinetics of the radiolysis of vapor. The documentation accompanying the experimental data used for verification must meet strin-

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Yields of hydrogen ions have been measured by pulse radiolysis with optical registration of short-lived species and by use of chromate ions and pH indicators as scavengers of H 3 0 + . It was found that G(H,O+) for the bulk of the solution (after the completion of reactions in spurs) is -3-3.3 ions/100 eV. Some reactions of H30+ ions were also studied by the pulse radiolysis method. The rate constants of their reactions with pH indicators-bromophenol blue, phenol red and bromothymol blue-were determined. They are 1.6 x lo'', 7.2 x 1O1O and 8.8 x 10" dm3 mol-' s-l respectively.The earlier conclusion that free hydrogen ions take no part in the formation of C1during pulse radiolysis of neutral aqueous solution of alkaline metal chlorides was confirmed on the basis of results of the investigation of the influence of CrO2additions and temperature on G(C1t).

Deep burial of liquid radioactive wastes in porous rocks is one of the methods of dealing with waste used in Russia [1]. Reliability in localizing wastes in such stores is determined primarily by the geological parameters, which should guarantee isolation from the surface and aquifers. The wastes represent a complicated multicomponent system, which may influence geochemical equilibria and alter the conditions in an underground store [2, 3]. Therefore, long-time forecasting for the state of such a store is impossible unless one knows the main transformations occurring in the waste-groundwater-rock system [4, 5].There is evidence on the main parameters governing the trends and extents of physicochemical processes in the thermal and radiation fields from the behavior of major components of the wastes and the radionuclides, including sorption on rocks, coprecipitation on solids, and so on [6][7][8][9]. The stratal temperature can be monitored periodically in injection and observation boreholes. These data characterize individual points but do not give a general picture of the temperature pattern and do not define zones of maximum heating or the temperatures there. To forecast component states at various times after deposition, one needs to know the distributions of the heat and dose levels throughout the store.Descriptions have been given [10] of ways of determining energy release and radiation doses in deep storage. Methods have been given [11] for calculating temperature patterns in storing liquids with the addition of cement involving hydraulic stratal fracturing. That form differs considerably from the storage of liquid wastes because the cement converts them to the solid state, which radically alters heat transfer. Thermal calculations on liquid waste storage [4, 7, 12] have shown that agreement is obtained with experiment when one considers the detailed technology, which includes not only depositing the wastes but also the injection of preparatory and displacing solutions. That is fairly obvious because the supply of large amounts of inactive solutions substantially reduces the radionuclide concentrations, as the radionuclides are the sources of heat and affect the heat-transfer conditions. Unfortunately, those papers give no details of the models, and the software used remains unknown, so one cannot perform calculations for other storage conditions.The data show that one can characterize the state of an underground waste store from a model that includes the following: 1) description of deposition in the storage rock; 2) calculation of energy production and radiation dosage; 3) calculation of temperature pattern at various times; 4) a physicochemical model for the state of the components that includes sedimentation, sorption, coprecipitation, and so on; and 5) calculations on component migration underground.

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