SU1666996A1 - Method of automatic measuring radioactivity of radionuclides in medium flow and device thereof - Google Patents

Abstract

The invention relates to the field of measuring the intensity of nuclear radiation, in particular, to methods and devices for analyzing radionuclide composition and activity of technological media of atomic power plants. The aim of the invention is to increase the efficiency and informativeness of measurements. The essence of the invention is that spectrometric measurements of the activity of the monitored medium are carried out with a single detector while passing the medium through one of the N (where N≥2) measurement chambers, the volumes of which are inversely proportional to the N average levels of medium activity. At the same time, the intensity of ionizing radiation from the medium is continuously monitored by comparing this intensity with the N lower and N upper predetermined levels to automatically switch the flow of the medium to the corresponding chamber, the volume of which provides the optimal statistical measurement conditions, and to the remote chambers - a clean medium. 2 sec. f-ly, 2 ill.

Description

The invention relates to the measurement of nuclear radiation intensity, and specifically to methods and devices for analyzing radionuclide composition and activity of technological media of atomic power plants, can be used to control radioactive impurities in said environments of nuclear power plants and other nuclear power objects. both for the purpose of diagnosing the condition of the equipment and for the purpose of protecting the environment from radioactive contamination.

The aim of the invention is to increase the efficiency and informativeness of measurements.

FIG. 1 is a functional diagram of the device for automatically measuring the activity of radionuclides in a substance stream; in fig. 2 - graphs of changes in the activity of the monitored medium and the recorded radiation intensity with time.

The method is carried out as follows.

The controlled medium is passed through a given flow rate through one of N, where N 2, flow-through measuring chambers, the volumes of which are inversely proportional to N average activity levels of the monitored medium (if the geometric solid angle of the detector per chamber is the same) and the clean medium through the other chambers. Spectrometric measurements of the activity of radionuclides are carried out, the duration of which is either fixed.

ABOUT

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or inversely proportional to the level of activity of radionuclides.

From the spectrometric information, information about the instantaneous value of the radiation intensity is continuously separated and compared with the N upper and N lower predetermined levels, which are the boundaries of the optimal statistical conditions for spectrometric measurements, based on the fact that the measured intensity value has reached the specified medium at a given time. sent to another measuring chamber corresponding to this level, the volume of which provides more optimal statistical conditions; s, wherein the duration of the measurement limit of the intensity values of said output torque level.

The device (Fig. 1, for the number of chambers N 3) contains supply 1 and return 2 pipelines of controlled medium, shut-off valves 3 and 4, switching valves 5-10, supply 11 and return 12 pipelines of clean medium, switching actuators 13-18 valves, measuring chambers 19-21, ionizing radiation detector 22, for example, Ge semiconductor (LI) spectrometry amplifier 23 programmable multichannel pulse analyzer 24 (PMAI) and processing unit 25 with information output devices, normalizer 26, two integrators 27 and 28, two comparator 29 and 30, two switches 31 and 32, the sources 33-38 of the reference signal conditioners 39 and 40 pulses, a reversible counter 41, the matching circuit 42, the valve control unit 43. The output of the detector 22 is connected to the input of the spectrometric amplifier 23, the output of which is connected to the input of the PMAI 24 and the input of the normalizer 26. The course of the PMAI 24 is connected to the input of the processing unit 25, and the output of the normalizer 26 is connected to the inputs of the integrators 27 and 28. The output of the integrator 27 is connected the first input of the comparator 29, and the output of the integrator 28 is connected to the second input of the comparator 30, the second input of the comparator 29 via the switch 31 is connected to the outputs of the sources 33-35 of the reference signal, and the first input of the comparator 30 is connected via the switch 32 to the outputs of the source ik 36-38 reference signal. The outputs of the comparators 29 and 30 are connected via the formers 39 and 40 to the direct and inverse inputs of the reversible counter 41, the outputs of which are connected to the inputs of the valve control unit 43, to the control inputs of the switches 31 and 32, and to the inputs of the matching circuit 42. The outputs of the control unit 43

the valves are connected to the actuators 13-18, and the outputs of the matching circuit 42 are connected to the control bus of the PMAI 24,

The device works as follows.

The controlled medium from the supply pipe 1 through the stop valves 3 and 4, which are constantly open during the measurements, and which are open in the initial state, when

0 low levels of activity of the controlled medium, switching valves 7 and 8 are passed with a predetermined flow rate through the measuring chamber 20 into the return pipeline 2. Through the measuring chambers 19 and 21, it is passed from the supply pipe 11 using switching valves 5, 6 and 9, 10 into return pipe 12 is clean medium. The output of the detector 22 thus forms

0 spectrometric information in the form of electric charge pulses, the frequency of which is proportional to the intensity of gamma radiation, and the amplitude is the energy of gamma rays emitted by the controlled medium. These pulses come to the input of the spectrometric amplifier 23, at the output of which voltage electric current pulses are formed, the amplitude and frequency of which are proportional to the corresponding gamma quanta energy and the intensity of their radiation in a controlled environment. The output pulses of the spectrometry amplifier 23 are fed to the input of the PMA 24 and the input of the normalizer 26.

5 PMAI 24 produces a distribution — the pulses are proportional to their amplitudes and the pulses are counted with the same amplitudes during the measurement time, i.e. a gamma-ray spectrum of the controlled medium is formed. In the normalizer 26, information on the instantaneous gamma radiation intensity of the measuring chamber 20 is extracted from the spectrometric information by

5 the normalization of all pulses in amplitude and duration, i.e. At the output of the normalizer 26, a sequence of pulses is formed with the same amplitude and duration, the frequency of which is proportional to the intensity of the ionizing radiation of the controlled medium. This sequence of pulses is fed to the inputs of two integrators 27 and 28 with different integration time constants,

5 which convert it into direct current voltage signals proportional to the instantaneous value of the intensity of ionizing radiation in the measuring chamber 20. The need to use two integrators

This is due to the fact that the range of optimal static loads of the spectrometric tract is limited from above by 5 10 pulses / s, and from below by the required control efficiency, i.e. the maximum permissible measurement duration and background radiation, which usually corresponds to a value of 10-50 pulses / s. At the same time, it is possible to reveal the upper and lower bounds of this range reliably using simple circuit solutions, for example comparators, by using two integrators. Constant integration times of which would differ, for example, 50-500 times and ensure the formation of output signals of integrators sufficient for reliable operation of the comparators. The output signal of the integrator 27 is fed to the first input of the comparator 29, the second input of which through the switch 31 receives the output signal of the reference signal source 34, the output signal of which corresponds to the upper limit of the optimum statistical loading range of the spectrometric path for the measuring chamber 20. The output signal of the integrator 28 arrives at the second input of the comparator 30, the first input of which through the switch 32 receives the output signal of the source 37 of the reference signal, the value of which is equal to rank output signal of the integrator 28 at the frequency of the input signal equal to the lower boundary of the measurement chamber 20. If the intensity of ionizing radiation in the measuring chamber 20 is less than the allowable value, i.e. Since the statistical loading of the spectrometric amplifier 23 is optimal, the output signal of the integrator 27 remains smaller than the output signal of the source 34 of the reference signal, and the output signal of the integrator 28 is larger than the output signal of the source 37 reference signal. In this case, the comparators 29 and 30 do not change their state, and no single pulses will be generated at the output of the imaging unit 39 and 40, and the reversible counter 41 will not change its state. The output code of the reversible counter 41, corresponding to, for example, the number 00, during this state provides the valve control unit 43 and the switches 31 and 32, in which the controlled medium is passed through the measuring chamber 20, and the cleaned medium through the measuring chambers 19 and 21 The inputs of the comparators 29 and 30 are connected to the outputs of the sources 34 and 37 of the reference signal.

At the outputs of the matching circuit 42, connected to an MAL control bus 24,

In this case, signals are generated that allow measurement for the PMAI 24. The measurement time programmed by PMAI 24 is either fixed in advance or limited, for example, by a specified number of pulses of a given amplitude input to the PMA 24. At the end of the measurement time, the information from the output PMA 24 is transmitted to processing block 25

0 (for example, a computer), in which a qualitative and quantitative calculation of the activity of radionuclides is made.

If there was a surge in activity of the controlled environment and, accordingly,

5 a change in the intensity of ionizing radiation in the measuring chamber 20, causing, for example, an increase in the statistical loading of the spectrometric tract beyond a predetermined limit (the characteristic time

0 units - ten seconds), then the pulse frequency at the output of the spectrometric amplifier 23 and, therefore, at the output of the normalizer 26 exceeds the permissible value. In this case, the output signal

5, the integrator 27 will exceed the output signal of the source 34 of the reference signal, and the comparator 29 will have its own state, and at the output of the driver 39 there will be a pulse that will go to the direct reversing input

0 of the counter 41 and change its state and the code at its output will correspond to the number 01. In this case, the switches 31 and 32 will connect the outputs of the sources 35 and 38 of the reference signals to the inputs of the comparators 29 and 30 and

5, the output of the valve control unit 43 will generate signals which, with the help of actuators 17 and 18 and switching valves 9 and 10, will provide switching of the measuring chamber 21 to transmission through

0 with the same flow rate of the controlled medium, and with the help of actuators 15 and 16 and switching valves 7 and 8, switching the measuring chamber 20 to passing clean medium through it, and at the circuit outputs

5 42 matching signals will be generated, according to which in the SMA 24 the measurement is stopped for a programmed time.

The spectrometric information accumulated up to this point in the ASMA 24 is not distorted, since this stops the access of pulses, the frequency of which exceeds the optimum statistical loading of the spectrometric tract,

5 input of the PMAI 24. This information is fed to the input of unit 25 for qualitative and quantitative calculation of the activity of radionuclides in a controlled environment, normalized to the implemented measurement time, at the output of the ionizing radiation detector 22 and, therefore, at the output of the normalizer 26 after switching the measuring chambers 20 and 21 (the characteristic time is about 0.2 s) a sequence of pulses is formed, the frequency of which is lower than the frequency of the sequence of pulses up to the moment of switching the cameras, as in the measuring yu chamber 20 enters the clean environment, and the measurement chamber 21 of smaller volume, and hence the repetition frequency of pulses at the output of the normalizer 26 will be less than the pulse repetition frequency corresponding to the upper border of statistical optimum loading range spectrometry. at the output of the integrator 27, a signal is generated whose magnitude is less than the output signal of the source 35 of the reference signal, and the comparator 29 returns to the initial state. At the output of the imager 39, which forms a single pulse only when the state of the comparator changes to one side, the pulse does not turn out and the reversible counter 41 does not change its state, i.e. its output code will correspond to the number 01. At the output of the matching circuit 42, the signals also do not change, but the PMA 24 after a software-defined time interval corresponding to the output code of the matching circuit 42 and necessary for cleaning the measuring chamber 20 will switch back to the measurement mode. And the measurement process will continue either for a predetermined period of time or until reaching a predetermined number of accumulated pulses, or until the next switching over of the measurement chambers 19-21.

If the increase in the intensity of the ionizing radiation of the controlled medium continues, then when the pulse frequency at the output of the normalizer 26 exceeding the measurement chamber 21 is exceeded, the output signal of the integrator 27 will exceed the output signal of the reference source source 35 and the comparator 29 will change its state again. the driver 39 generates a pulse, which, arriving at the direct output of the reversible counter 41, will change the code at its output, which will correspond to the number 10. In this case, the block 43 is controlled and the valves will generate signals that, using actuators 17, 18 and 13, 14 and switching valves 5, 6 and 9, 10, will switch the measuring chamber 21 to a clean medium, and the measuring chamber 19 to a controlled medium. The matching circuit 42 will generate signals that will stop measurement at a software defined time and will accumulate information at PSA 24 to processing unit 25 and via which switches 31 and 32 will connect the outputs of sources 33 and 36 of the reference signal to comparators 29 and 30 . Further, the device will come to a steady state in the same way as during the previous switching of cameras, only the code at the output of the reversing counter will be

0 correspond to the number 10.

If the intensity of ionizing radiation decreases, the pulse tracking frequency at the output of the normalizer 26 and the output signals of the inverters 27 and 28 will also decrease, and when the output signal of the integrator 28 is less than the output signal of the reference signal source 36, the comparator will change its state 30 and at the exit

0 shaper 40 will generate a pulse that will go to the inverse input of the reversible counter 41 and change the code at its output, which will correspond to the number 01, and the valve control unit 43 will generate signals that will be provided by drives 13, 14 and 17, 18 and switching valves 5, 6 and 9, 10 connecting the measuring chamber 21 to the controlled medium, and measuring

0 cameras 19 to clean environment. The matching circuit 42 will generate signals that will stop the measurement in the ASMA 24 for a programmed time and the information will go to the processing unit 25, and

5 which the switches 31 and 32 will connect to, the inputs of the comparators 29 and 30 of the outputs of the sources 35 and 38 of the reference signal. Since the volume of the measuring chamber 21 is larger than the volume of the measuring chamber 19, then immediately

0 after switching the cameras, the intensity of ionizing radiation in the zone of the ionizing radiation detector 22 will increase and the pulse frequency at the output of the normalizer 26 will exceed

5, the lower limit of permissible value, with the output of the integrator 28 exceeding the output of the source 38 of the reference signal. The comparator 30 then returns to its original state, at the output

0 the driver 40 does not deliver a pulse in this case, since it works similarly to the driver 39, and the reversible counter 41 will maintain a state in which the code at its output will correspond to

5, the number 01. At the time set by the software and necessary for cleaning the measuring chamber 19, the PMAI 24 switches to the measurement mode and its input receives pulses from the output of the spectrometric amplifier 23. The measurement time in this case is limited in the same way as after the previous switching cameras. If the measurement process further decreases the intensity of the ionizing radiation of the controlled medium, the device will work out the change in a similar way, i.e. the state of the reversible counter 41 will change (its code will correspond to the number 00) and the switching of the measuring chamber 20 to the monitored medium, and the measuring chamber 21 to a clean medium.

With a fixed position of the ionizing radiation detector 22, various configurations are possible in the set of measuring chambers 19-21, which do not fundamentally change the implementation of the method and operation of the device from the point of view of achieving the objective of the invention. For example, a config / ci with equidistant arrangement of chambers relative to the detector can be realized. There may be configurations when the cameras are located at different distances, but the geometric efficiency of recording radiation from each of the cameras is the same (i.e., with the same absolute active in radionuclides in the volume of any camera, the same statistical loading of the spectrometer is provided) . With the opinion of the position of the ionizing radiation detector 22 relative to the selected set of measuring chambers 19-21, the measurement range can be shifted towards higher activities (when the detector is removed) or to smaller (when approached) without changing the number of cameras

Graphs of the change in the intensity of the ionizing radiation of a controlled medium detected by a semiconductor detector with a surge in the activity of the controlled medium are shown in FIG. 2,

where (is the intensity of the radiation of the controlled medium detected by the detector, imp./sec;

let, 1–2, to the upper limits of the radiation intensity, permissible, for example, for measuring chambers 19–21, respectively;

1h1.1n2, ns - lower limits of the radiation intensity, permissible, for example, for measuring chambers 19-21, respectively;

And the activity of the controlled environment, rel .;

ABI, Av2, AVZ value of the activity of the controlled medium at which the upper limits of the IBL IFV pz, respectively, are reached,

AHL AHZ, ANS - the value of the activity of the controlled medium, which correspond to the lower boundaries of IHL 1Н2, 1нз.

ti, 13 time points

the intensity of the radiation detected by the detector, the upper bounds;

ts. t are the instants of time for reaching the intensity of the radiation detected by the detector, the lower bounds.

0 Change of radiation intensity in the time intervals between the moments of time i, 12; 13.14; 15, te; t, te are determined by transients in measuring chambers 19-21, due to the switching of controlled and clean media.

The method is carried out using the most simple, but retaining the possibility of functional expansion. technical means, i.e. with the help of two

0 com, speakers 29 and 30. two formers 39 and 40 pulses and a reversing counter 41. connected to the valve control unit 43 Switches 31 and 32 and individual sources for each camera 335 38 reference signals allow, in addition, with fixed volumes of measuring chambers 19-21 and relative to the ionizing radiation detector 22, affect the degree of overlap

0 working control sub-bands, i.e. report additional features in the practical use of the device.

Thus, in the proposed method and device for its implementation from

Claims (2)

The process of measuring the activity of radionuclides in a substance stream eliminates operations associated with preliminary measurement of the level of activity, and also eliminates information distortions that occur during the measurement process due to bursts of activity causing an increase in the statistical loading of the spectrometric tract beyond the allowable limits, and this increases the efficiency and informativeness of the measurements. Claim 1. A method for automatically measuring the activity of radionuclides in a substance flow, which means that the controlled medium is passed through a given flow rate through one of N, where N is 2. flow measuring chambers, the volumes of which are inversely proportional to N average levels of activity of the controlled medium, and 5 clean medium — through other chambers; spectrometric measurement of the activity of radionuclides is carried out, the duration of which is either pre-fixed or inversely proportional to the level of activity of the radionuclides, characterized in that, in order to improve the efficiency and informativeness of the measurements, information on the instantaneous value is obtained from spectrometric information the intensity of the ionizing radiation of the controlled medium is compared with the N upper and N lower predetermined levels, which are the boundaries of According to the statistical conditions of the spectrometric measurements, after the instantaneous intensity of the ionizing radiation of the controlled medium emerges at a given time, the specified level of the controlled medium is directed to another measuring chamber corresponding to this level, the volume of which provides the optimal statistical conditions of spectrometric measurements, the duration of measurements limits at this moment, the instantaneous value of the intensity of ionizing radiation is environment under one of the specified levels. 2. An apparatus for automatically measuring the activity of radionuclides in a substance flow, containing N flow measuring chambers, the volumes of which are inversely proportional to the activity levels of the controlled medium, valves with actuators providing the controlled medium through one of the chambers and the clean medium through the rest, valve control unit, serially connected ionizing detector radiation, spectrometry amplifier, programmable multichannel pulse analyzer, processing unit, ОT and C, so that, in order to increase efficiency and informativeness of measurements, the pulse normalizer, two integrators are entered into it. 2 N reference sources, two pulse drivers, a reverse counter of the reference signal, two pulse drivers, a reverse counter and a matching circuit, the input of the normalizer connected to the output of the spectrometric amplifier, and the output from the inputs of two integrators, output the first integrator is connected to the first input of the first comparator, the output of the second integrator is connected to the second input of the second comparator, the second input of the first comparator is connected via the first switch to the outputs of the first N sources of the reference signal, and the first input of the second comparator is connected via the second switch to the outputs of the second N sources of the reference signal, the output of the first comparator through The first pulse shaper is connected to the forward input of the reversible counter, and the output of the second comparator through the second pulse shaper is connected to the inverted input of the reversible counter, the outputs of the reversible counter are connected to the inputs of the valve control unit, to the inputs of the switch and via a programmable multi-channel analyzer matching circuit pulses. 7 j 1 5-10 5 10 t rel fd