According to data from the International Atomic Energy Agency [1] there are presently 442-power units operating in the world having a total installed electrical capacity of 350,964 MW, which provide roughly 14% of all the energy generated on the planet. In the case of certain countries (for example, France, Japan, Ukraine) it can be said that they depend strongly on nuclear energy and have no real possibility of replacing it with conventional sources of energy. In other countries (the USA and Russia) this problem is not so acute in view of the existence of considerable reserves of coal, oil, and gas, and development of nuclear power in them is mainly related to transport problems of supplying the fuel to power stations and the requirements of protecting the environment.Questions of ecology are presently attracting worldwide attention since the development of traditional power sources in all countries results in intense buildup in the atmosphere of oxides of various elements, primarily carbon dioxide, and this is capable of causing a global climate change on the planet and the combustion of a large amount of oxygen, whose compensation in the atmosphere by naturally occurring processes is approaching its possible limit according to certain estimates. It is well known that nuclear energy generation does not require oxygen and does not produce carbon dioxide. At the same time, as for every large-scale modern industry, it has the right to exist only under conditions of safety for the population and protection of the environment from the radiation factor that is a characteristic feature of its production [2, 3].In recent activity in all countries of the world where nuclear power stations are operated or their construction is proposed, a marked reduction is observed in the rate of introducing new power units compared with that predicted. The reasons for this are complex and numerous, and there is no single point of view concerning some of them. The principal reason is that for certain types of destruction of a power unit (for example, the catastrophe at the Chernobyl nuclear power station in 1986) the radiation consequences are so great that such accidents are socially unacceptable and must be eliminated completely right from the design stage of the undertaking. In the case of accidents for which society can in principle accept the scale of the consequences, it is necessary to def'me an acceptable probability (risk) by comparing the social necessity of industry and the economic ability of society to eliminate its consequences. For nuclear power stations a limitation to both the probability of serious accidents and the scale of their consequences in the environment must, therefore, be introduced.In accordance with the recommendations of the International Commission on Radiological Protection (ICRP) [4] the dose limits for irradiation of the population do not apply to potential irradiation. In the latter case the limitation corresponding to the maximum dose can be given in the form of a maximum risk. The term "risk" was ...
The Chernobyl accident resulted in the contamination of the environment with long-lived radionuclides, including transuranium elements. The results, more accurate than the data of [1], for the production of the basic long-lived radionuclides in the reactor core where the accident occurred [2] are presented in Table 1.According to Table 1, the 241pu contribution to the total activity of transuranium elements accumulated in the reactor core is about 84%. Since the same amounts escaped into the atmosphere during the accident (3% [1]), this remark is also valid with respect to the radioactive contamination of the environment.The contamination of the environment by 24tAm is due both to its direct emission from the reactor core and the subsequent accumulation as a result of B-decay of 241Pu.The time dependence of the accumulation of 241Am activity in the environment is described by the equationwhere Aot and A02 are, respectively, the 24tpu and 24tAm emissions during the accident (in PBq); X t = 0.0482 yr -t is the decay constant of 241pu; X 2 = 0.0016 yr -I is the decay constant of 241Am; and, t is the time after the accident (in yr).We now introduce the function Y(t), which is the ratio of the 241Am activity at time t to the activity of the material emitted during the accident, i.e., Y(t) = A2(t)/A02.From Eq.(1) we obtain the expressionwhere k = X2/(X l -X2)(AoJA02 ).It is easy to show that the maximum of the function Y(t)
The SNESK program implements the approach described in [1][2][3] for calculating first-loop coolant leakage through the pipe board or collectors into the boiler water of a steam generator of a nuclear power plant with a VVI~R reactor.The algorithm is based on an analysis of a system of linear differential equations describing mass transfer of radionuclides through the second-loop systems of a nuclear power plant with VVI~R reactors. The case when all quantities appearing in the model are stationary random functions, which is important for practical applications, was studied. In the present version of the program it is assumed that the interaction between separate steam generators through the general systems is negligibly small, and the steam generator itself is a system with ideal mixing. The point and interval estimates of the leakage and flow rate of the blow-through water are calculated on the basis of a regression analysis of a model of the process being investigated, the input data, and the errors in these data. An important feature is the possibility of calculating leakage in the absence of reliable information about the flow rate of the blow-through water for cleaning.The leaks are calculated on the basis of a periodically measured specific activity of 131-135I, 24Na, and 42K in the first-loop coolant and in the boiler water of a steam generator, taking into account the reliability of these data (errors of measurement). For this list only data on radionuclides whose activity is measured with an error of not greater than 30% are used.When the flow rate of the blow-through water for cleaning is known, information about the activity of one radionuclide is sufficient to estimate the leakage. However, the error of the estimated leakage decreases as the number of radionuclides employed increases.In the absence of data on the flow rate of the blow-through water of the steam generator for cleaning, information about more than two radionuclides is used to calculate the leakage. The following technological parameters of the operation of a steam generator are used in the calculation: steam production, moisture content of the steam, the mass of the boiler water, and the flow rate of the blow-through water for cleaning (if it is measured). The data from the measurements, the name of steam generator, and required comments are also introduced into the program.The computational results are displayed on a monitor screen and are also printed out. The following information is displayed on the monitor screen: the name of the steam generator and the power-generating unit of the nuclear power plant, the date of the calculation, the average leakage, the confidence interval for the leakage, the flow rate of the boiler water for cleaning, the confidence interval for the flow rate of the boiler water for cleaning, and an estimate of the leakage for each of the reference radionuclides. In addition, visual and sound signals are given in the case when the leakage exceeds a limiting value or the quality of the input data is not satisfa...
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