One of the most important parameters indicating contamination of the environment by a radioactive contaminant (radioactive gases, aerosols), entering the atmosphere as a result of emissions from the ventilation pipes of nuclear power and other plants in the nuclear power industry, is the intensity of emission eemts [Ci/sec], defined as the product of the flow rate G [cm3/sec] in the ventilation pipe by the volume activity Qv [ Ci/cm3] [1]. For the standard operation of a nuclear power plant, the design and off-design accidents in the case when an automated system for monitoring the radiation conditions (ASMRC) is used, this parameter should be evaluated in the automatic regime. At the present time the per second flow rate is determined as the sum of the flow rate of separate ventilation systems that are part of the automated system; this is an inconvenient and expensive procedure in automating the measurements of the flow rate. The volume activity of the impurity in the automatic regime is measured with aspiration plants of the "Kalin" type and the nuclide composition of the standard emissions is measured under laboratory conditions in accordance with the technological regulations. If the rate of gas flow in the ventilation pipe is known as a function of the radius of the pipe, then, by normalizing the velocity function to the value measured at a point, i.e., by determining the velocity in absolute units, the flow rate can be found as an integral of the velocity of the flow over the cross section of the pipe at constant density, and the volume activity can be measured according to the dose rate produced by the radioactive contaminant.Therefore, if the velocity of the air flow at some point in the pipe and the dose rate of/3 and ,,/-radiation of the radioactive contaminant can be measured with a sensor, then the problem posed above can be solved. The construction of such a sensor and a method for determining the intensity of emission of a radioactive contaminant is presented in [2]. The sensor is based on a measurement of the induction and ionization currents produced by the ionized gas (air) flow, moving in the transverse (relative to the direction of flow) electric field in the interelectrode gap of the channel of the sensor (Fig. 1). In the present paper we consider the theory of the method and present the results of measurements of the induction and ionization currents as a functions of the velocity of the air flow or the external voltage, which indicate operation of the sensor.The physical crux of the method consists of the following. A gas flow, formed in the ventilation pipe as a result of ionziation of the air flow by the radioactive contaminant and separated in the electric field of the interelectrode gap, produces a current, the concentration of ions of one sign in the regions near the electrodes being much higher than that of ions of the opposite sign. But, just as the longitudinal air flow in the ventilation pipe also drags ions, so it produces a longitudinal component of their velocity that determine...

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