Method of controlling mass fraction of uranium-235 isotope in gas phase of uranium hexafluoride and measuring system for implementation of the method

FIELD: analytical methods in nuclear engineering.

SUBSTANCE: invention relates to analysis of fissile materials by radiation techniques and intended for on-line control of uranium hexafluoride concentration in gas streams of isotope-separation uranium processes. Control method comprises measuring, within selected time interval, intensity of gamma-emission of uranium-235, temperature, and uranium hexafluoride gas phase pressure in measuring chamber. Averaged data are processed to create uranium hexafluoride canal in measuring chamber. Thereafter, measurements are performed within a time interval composed of a series of time gaps and average values are then computed for above-indicated parameters for each time gap and measurement data for the total time interval are computed as averaged values of average values in time gaps. Intensity of gamma-emission of uranium-235, temperature, and pressure, when computing current value of mass fraction of uranium-235 isotope, are determined from averaged measurement data obtained in identical time intervals at variation in current time by a value equal to value of time gap of the time interval. Computed value of mass fraction of uranium-235 isotope is attached to current time within the time interval of measurement. Method is implemented with the aid of measuring system, which contains: measuring chamber provided with inlet and outlet connecting pipes, detection unit, and temperature and pressure sensors, connected to uranium hexafluoride gas collector over inlet connecting pipe; controller with electric pulse counters and gamma specter analyzer; signal adapters; internal information bus; and information collection, management, and processing unit. Controller is supplemented by at least three discriminators and one timer, discriminator being connected to gamma-emission detector output whereas output of each discriminator is connected to input of individual electric pulse counter, whose second input is coupled with timer output. Adapter timer output is connected to internal information bus over information exchange line. Information collection, management, and processing unit is bound to local controlling computer network over external interface network.

EFFECT: enabled quick response in case of emergency deviations of uranium hexafluoride stream concentration, reduced plant configuration rearrangement at variation in concentration of starting and commercial uranium hexafluoride, and eliminated production of substandard product.

24 cl, 5 dwg

 

The invention relates to the analysis of nuclear materials, radiation methods, and is intended for operational control of the enrichment of uranium hexafluoride in gas flows isotope separation of uranium production.

The enrichment of uranium is commonly understood as either atomic or mass fraction (concentration) of the isotope uranium-235 in a mixture of isotopes of uranium, expressed as a percentage. Unprincipled distinction between the definitions insignificant for process control.

The control methods of uranium enrichment based on indirect methods, where the content of uranium-235 is judged by the results of measurements of certain quantities Xiassociated with the determined mass fractions of C5previously known functional relationship

Here X1, X2, ... - registered analytical signals, and the physical constants or constant parameters (coefficients)that characterize the measurement system.

For example, to control the mass fraction of the isotope uranium-235 in the gas phase of uranium hexafluoride known mass spectrometric method used in routine (serial) and the reference measurement. The method includes sampling the analyzed isotopic mixture, sample preparation, sample introduction into the ion source of the mass spectrometer, the actual registration of the ions in the measuring chamber of the mass spectrometer, the processing of the measurement results with the issuance of the [US No. 4514637 And, IPC 3 G 01 N 23/00, publ. 30.04.1985] (analog). The concentration of atoms or molecules in the analyzed sample is proportional to the ion current receiver ion mass spectrometer:

where Ii- register the current i-th component of the mixture, A; Cithe concentration of the i-th component of the mixture; α - calibration coefficient. The measurement error of the isotopic composition of uranium varies from tenths to thousandths of a percent and depends on the sequence analysis. The total analysis time ranges from tens of minutes to several hours and increases with increasing the accuracy of the analysis.

The results of measurements representing the current value of the mass fraction of uranium-235 in a fixed point in time, receive periodically over a significant time period. For this reason the method is not used in mass rapid control. In the latter case, the preferred radiation monitoring enrichment, based on the measurement of the photon spectrum (x-ray and gamma-radiation)inherent to analyze isotopes of uranium.

Known monitoring the enrichment of the gas phase of uranium hexafluoride using spectrometers based on scintillation detectors [Handbook of nuclear energy technology: F. RAS and others - M.: Energoatomizdat, 1989, s] (the number is). Here the concentration (or number of atoms) of uranium-235 is determined by measuring the characteristic gamma radiation specific to the isotope (typically, the basic analytical peak 185.7 Kev gamma-ray spectra, maintainer of natural alpha decay of uranium-235), and the total number (or concentration) of uranium by x-ray fluorescence of uranium atoms when lighting the gas phase of uranium hexafluoride gamma rays from an external source (for example, based on isotope americium-241 or selenium-75). Devices, registering gamma and x - ray radiation, graduate in units of content defined elements according to the measurement results of the reference samples. The ratio of the two concentrations gives the mass fraction of the isotope uranium-235

where Mu235, MI totalNu235NI totalWithu235WithI total- respectively, the atomic mass, number of atoms and the mass concentration of the isotope uranium-235, and total uranium in the gas phase; IγIpthe count rate of the detector main analytical lines of the spectrum of gamma and x-rays, respectively; b, q - calibration coefficients of the gamma and x-ray-channel measuring system.

The measuring system that implements the monitoring, includes two measuring cameras with gamma - ray detectors and x-ray channels, which is exercised by the overlap of the sample of uranium hexafluoride. The signals from the detectors are sent to the input unit of gathering and processing information to calculate the average intensity values account for the time interval measurement and calculation of the mass fraction of uranium-235 ratio (3). In the information output system periodically receive the result, which is an average in the time interval the amount of enrichment.

The time interval and the measurement error of the isotopic composition is inversely proportional to the average count rate of gamma - ray detectors and x-ray channels. In addition, the count rate of the detector in the x-ray channel depends on the intensity gamma-ray source. At concentrations of uranium-235 1-5 wt.% the measurement results with a relative error ±1 Rel.% able to get for 20-25 minutes.

To measure the isotopic enrichment of uranium is also known a method and apparatus [US No. 4629600 And IPC 4 G 21 17/06, publ. 16.12.1986] (analog), where to determine the atomic concentration of total uranium measuring chamber with a gas phase of the uranium hexafluoride is irradiated by photons with energy above or below the K-edge atomic spectrum of uranium and measure the intensity of radiation transmitted through the chamber. The calculation of the enrichment of uranium hexafluoride are in accordance with (3) with simultaneous recording of the main analytical peak uranium-235.

Significant drawbacks - external is radioisotope source of gamma radiation, the inability to determine the enrichment of uranium hexafluoride during perestroika configuration of the technological scheme of the plant because of the resulting large measurement errors.

The closest in technical essence to the present invention is a method of controlling the enrichment of gaseous uranium hexafluoride uranium-235 [RU No. 2189612 C1 IPC 7 G 01 N 23/00, publ. 20.09.2002], consisting in the measurement from the camera with uranium hexafluoride intensity of gamma radiation from uranium-235, which also measure the pressure and temperature of the uranium hexafluoride, and about the content of the isotope uranium-235 in the uranium hexafluoride is judged by the value of the ratio

Here Iγ - the intensity of the gamma radiation of uranium-235; t - temperature of uranium hexafluoride in the cell; p is the pressure of uranium hexafluoride in the chamber; α - calibration constant.

The method implements the installation comprising a cylindrical aluminum chamber with inlet and outlet valves on the pipes inlet and production of uranium hexafluoride, a detector of gamma radiation of uranium-235 with a pulse analyzer, sensors measure pressure and temperature, the United through the power of the data collection computer system. The block of data acquisition (adapter signals), the transformation is information about pressure and temperature to the form suitable for processing in the computer is the first complex.

The method is as follows. A sample of uranium hexafluoride sleuth from the monitored volume (gas manifold) cascade setting to the desired pressure to the prepared measuring chamber. The camera cut from the pipe inlet. Stand for equalization of temperature and pressure. Include gamma radiation detector of uranium-235. Measuring the intensity of gamma-radiation lead through two channels. The first channel set up on the energy line 185,7 Kev, the second channel for the registration of gamma radiation in a more high-energy interval to account for the background component under the peak 185,7 Kev. Simultaneously measure and continuously record the temperature and pressure of uranium hexafluoride in the measuring chamber. Calculate the average values of temperature and pressure for the entire period of measuring the intensity of gamma radiation. In computing the complex according to the formula (4) calculate the value of the concentration of uranium-235. After measuring the uranium hexafluoride from the measuring chamber through the outlet valve on the highway release sublimate in the cylinder, cooled by liquid nitrogen. The measuring chamber is ready for a new measurement cycle. Constant α in the estimated equation (4) determine the initial set-up of the measuring system by conducting parallel measurements similar to the ha of the new sample to the mass spectrometer.

Validation of the method showed that the error in the measurements increases with decreasing pressure of the gas phase in the measuring chamber.

Compared with the previous analogues, in principle, allows you to more accurately calculate the enrichment of uranium hexafluoride in the non-stationary gas flows, as when replacing in the estimated equation (4) parameter t for the absolute temperature T of the gas phase ratio R/T is already uniquely identifies the total number of uranium atoms in a chemically pure uranium hexafluoride with any change of thermodynamic state of the gas phase according to the known law for ideal gases

where nUF6the concentration of the molecules of uranium hexafluoride per unit volume; VISM- the volume of the measuring chamber; k - Boltzmann's constant. From (5) the total number of uranium atoms in the measured volume

and, by combining (3) and (5), we come to the new value

where α1calibration coefficient, defined when configuring the device.

This method of control calculated by equation (7) and implements its system of measurement is selected as the analog prototype.

The disadvantage of the prototype method, as with the other analogues, is that numerical results can be obtained only h is cut intervals, exceeding the value of the time interval measurement. With acceptable accuracy, this period is 40-45 minutes, including the time of overlap of the isotopic gas mixture in the measuring chamber, the exposure time for the adjustment of temperature and pressure and subsequent removal of uranium hexafluoride from the camera. It is possible to control the mass fraction of uranium-235 in natural gas streams with a stationary isotopic concentration is considered to be sufficient, but totally unacceptable for process control cascade installations, tracking in real-time transient processes in the cascade or for rapid response to emergency deviation of isotopic concentration from the established thresholds.

The last problem is especially relevant, because the isotope separating the uranium industry is currently working to fulfill specific orders, differing in the degree of enrichment of a commercial product. Modern uranium plants have the technical ability to rebuild the configuration of interstage links to various problems. During the reconstruction of the technological scheme in inter-stage, interstage and selected flows occur transients involving short-term significant change in thermodynamic state and the current enrichment work environment - ha is obraznogo of uranium hexafluoride.

The present invention aims at solving the problem of tracking in real time the current value of the mass fraction of the isotope uranium-235 in natural gas streams of uranium hexafluoride with a simultaneous increase measurement accuracy transient.

Currently on the market there are no suggestions of methods and measurement systems that can provide such technological Express control.

The above problems are solved due to the fact that in the method of controlling the mass fraction of the isotope uranium-235 in the gas phase of uranium hexafluoride, including the measurement in the selected time interval of the intensity of gamma radiation from uranium-235, the temperature and pressure of the gas phase of uranium hexafluoride in the measuring chamber and the subsequent processing of the averaged measurement results calculated in the measuring chamber create a duct of uranium hexafluoride and is measured in the time interval represented by the set of time segments, with calculated average values of the intensity of gamma radiation, the temperature and pressure of the gas phase of uranium hexafluoride in each time interval, and the results measurements in the time interval calculated as an average value of the average values of measurements in time intervals; the intensity of the gamma radiation, the temperature and pressure when calculating the current value of the mass fraction of the isotope uranium-235 determined through averaging the measurement results in identical time intervals when the current time value, equal to the time interval; and the calculated value of the mass fraction of the isotope uranium-235 is referred to the current time, per time interval measurement.

In addition, the tasks are achieved by the fact that the calculated value of the mass fraction of the isotope uranium-235 is referred to the current time, attributable either to the middle part or at the end or beginning of a time interval that the selected time interval are set equal time intervals; that the value of the time interval is chosen inversely proportional to the pressure of the gas phase in the measuring chamber; the intensity of gamma radiation, the temperature and pressure of the gas phase of uranium hexafluoride define at least two selected time intervals; that the magnitude of the time interval ranges from 100 to 2000 seconds; the amount of time segments is from 10 to 200 seconds; that, moreover, periodically conduct a comparison of the calculated values of the mass fraction of the isotope uranium-235 from its reference measurement; that the calculated ratio for processing the averaged measurement results calculated by adjusting so that the calculated value of the mass fraction of the isotope uranium-235 has deviated from the reference measurement on pre-determined the established value; what limit value of the deviation is ±1 Rel.%; what in the estimated ratio of correct calibration factor; that the measuring chamber is connected in parallel to the gas collector of uranium hexafluoride, and the gas manifold at the site of connection of the measuring chamber establish a narrowing device, such as a diaphragm; the measurement of the intensity of gamma radiation is determined taking into account the background component under the main analytical peak characterizing the natural alpha decay of uranium-235; the measurement of the intensity of gamma radiation is conducted at lock loop under the energy of the primary analytical peak characterizing the natural alpha-decay of the isotope uranium-235; the measurement of the intensity of gamma radiation is in the energy interval 166-215 it; that energy the interval for measuring the intensity of gamma radiation is divided relative to the energy of the primary analytical peak characterizing the natural alpha decay of uranium-235, two subchannel; the measurement of the intensity of gamma radiation is in the energy sub-166 -185,7 Kev and 185,7-215 Kev; the signal-locked loop under the energy of the primary analytical peak is formed by the relative difference in the intensity of gamma radiation in the subchannels.

The method implements the control system mass fraction from the top of the uranium-235 in the gas phase the uranium hexafluoride, containing the measuring chamber with the nozzle inlet and outlet, a detection unit, temperature sensors and pressure, is connected by the pipe inlet to the gas collector of uranium hexafluoride, the controller counters with electrical impulses and analyzer gamma-ray spectra, adapters signals, internal data bus, the block collection, management and processing of information, where the controller is further introduced at least three discriminator and one timer; input discriminators connected to the output of the detecting unit of gamma radiation, and the output of each discriminator is connected to the input of the individual meter electrical impulses connected to a second input with the output of the timer; the timer outputs and adapters are connected through line of communication with the internal data bus; block collection, management and processing of information on the external network interface connected to the computer network management.

In addition, the control system is further complemented by a technical solution, which consists in the fact that the measuring chamber by the outlet pipe is connected to a gas manifold of uranium hexafluoride; that to the local area network control via the second external interface network connected output channel reference probe mass fraction of the isotope uranium-235, for example mass spectra is romera; the output of the analyzer gamma spectrum controller is connected to the input of the detection unit, the detection unit according to the channel information exchange is additionally connected to the internal data bus; the controller of gamma-ray spectra is made in the form of a single Board spectrometric device containing, in addition, circuit solutions for precision spectrometry measurements in the form of the amplifier channel, Converter charging pulse signals into a digital code, a buffer memory, a diagram of the interface for managing the parameters, and connected across the input to output of the detection unit, one output to the internal data bus and the other to the detection unit; in the gas collector road between inlet and outlet of the measuring chamber is installed narrowing device; that, moreover, the conductivity of the nozzle inlet of the measuring chamber is greater conductivity of the outlet pipe.

In the analysis above, known methods and systems of control (see analogues), i.e. in the analysis of the level of technology control of uranium enrichment, not discovered the ways to exactly the same set of features that allows authors to consider the claimed method meets the criterion of “novelty”.

For specialist measurement systems uranium enrichment explicit way the m should not to solve the above problems in the claims, which stated, you need to enter exactly the above set of distinctive features. In this regard, the authors believe that the claimed method meets the criterion of "inventive step".

The main distinctive feature of this method is that all measurements are in continuous flow of uranium hexafluoride through the measuring chamber, and calculating a new average of the measurement values of the gas stream in identical time intervals and the subsequent processing of the measurement results is carried out periodically through 10-200 seconds. When assigning the calculated value of the mass fraction of the isotope uranium-235 to that of real-time attributable to the current time interval, for example at its middle part (equivalent to the end or beginning of the time interval), the measuring period is equivalent to a continuous, given a certain inertia of gas-dynamic processes in the volume of the cavities equipment isotope separation production.

High gazonapolnenie (pressure) in the measuring chamber, varying the size of the measuring time interval, the choice of a value for a time interval inversely proportional to the pressure of the gas phase in the measuring chamber, and pereodicheski the adjustment of the measuring system under the indication of the reference meter provide practical no appearance of bias under control. The method and system of measurement also reduce the probability of occurrence in the control random errors.

The highest value of the time interval in the claimed range of 100-2000 seconds is selected at a constant value of the mass fraction of the isotope uranium-235 in the gas stream. After a transient, for example, except when accurate measurements are important to the efficiency of control over the concentration of uranium-235, the value of the time interval can be reduced, or the control can be carried out in two significantly differing intervals. This way is chosen, and the amount of time in the range 10-200 seconds.

The optimum conditions of the process controlling the enrichment of uranium hexafluoride in each case are set empirically.

Figure 1 and 2 presents implement the method the block diagram of the control system; figure 3 is a 5-time diagrams of the current changes in the mass fraction of the isotope uranium-235 in the uranium hexafluoride in selected gas collector isotope separation of uranium factory.

The system comprises a measuring chamber 1 with the nozzle inlet 2 and release 3, the gas manifold 4 of uranium hexafluoride cascade setup with a narrowing device 5, the detection unit 6, the temperature sensors 7 and pressure with 8 adapters 9 and 10, respectively, the controller 11 with discriminatory 12-14,counters, electrical impulses 15-17, analyzer gamma spectrum 18, a timer 19, the internal data bus 20, block collection, management and processing of information 21, the external network interface 22, a local area network 23 management enrichment cascade, to which external network interface 24 connected to the reference meter mass fraction 25 (mass spectrometer).

In the measurement system (see figure 2), the controller 11 with blocks 12-19 made in the form of single-Board spectrometric device 26.

The control method is as follows. The measuring chamber 1 through the pipes 2 and 3 connected in parallel to the section of the gas manifold 4 selected lines of enriched uranium hexafluoride cascade isotope separation plant. Inside the reservoir 4 in the area between the nozzles 2 and 3 establish a narrowing device 5 in the form of a diaphragm and due to the resulting pressure drop of the gas stream to create a continuous selection of uranium hexafluoride into the measuring chamber from the inlet through the pipe 2 and the release of the pipe 3. Since the conductivity of the pipe 2 more conductivity of the pipe 3, to the extent the pressure of the gas phase in the measuring chamber differs little from its pressure in the reservoir 4 of uranium hexafluoride.

Inside the chamber 1 is set to a detection unit 6 on the basis of the crystal Nal(TI) with a photomultiplier (PMT-49), digital micromanometer is W2 7 and thermocouple platinum resistance 8. The detection unit detects gamma spectrum of photon radiation of the isotope uranium-235 and its daughter isotopes, formed by the chain of radioactive decay and present as uranium hexafluoride, and the composition of the corrosion deposits on the walls of the measuring chamber. The output of block a signal is generated in the form of electrical pulses with the amplitude proportional to the energy of gamma quanta, then flows to the input of discrimination 12, 13, 14 of the controller 11.

On discriminator is a sample of gamma-quanta energies. In particular, the discriminator 12 is extracted with energy 320-380 Kev for determining a background component under the main analytical peak 185,7 Kev. The number of pulses counted by the counter 15. Discriminatory 13 and 14 are designed to determine the intensity of the energy lines 185,7 Kev. Here is a sample of gamma-quanta with energy 166-215 Kev, while the energy interval is divided relative to the line 185,7 it on two subchannel - 166-185,7 Kev and 185,7-215 Kev. Sample energy quanta 160-185,7 Kev is on the discriminator 13, and their number is counted by the counter 16. On the discriminator 14 is sampled energy quanta 185,7-215 Kev, and their number is counted by the counter 17. The analyzer 18 is a comparison of the number of quanta counted in the counters 16 and 17, and still is sustained fashion to the difference of the account is formed, the signal PLL PMT block b for energy 185,7 Kev.

Counting the number of quanta counter 15-17 is conducted within a specified time period 10-200 seconds, which algorithmically calculated in block collection, management and processing of information 21 as a multiple of a given time interval measurement 100-2000 seconds. In the same time interval in block 21, there is an accumulation of information about pressure and temperature of uranium hexafluoride in the measuring chamber 1. Information about the latter enters the block 21 with the pressure sensors 7 and temperature 8 through adapters 9 and 10.

Job duration time measurement is performed by entering information about it in the timer 19. At the end of lap time, the timer generates a signal on internal data bus 20 is supplied to the block collection, management and processing of information. To signal the end of the time period, the number of quanta counted in the counters 15-17, bus 20 is passed to block 21. When the counters are reset, and the timer is set the next time interval from the interval 10-200 seconds.

In block collection, management and processing of information accumulates information about the count rate of quanta, the pressure and temperature of uranium hexafluoride in the measuring chamber for a time interval of 100-2000 seconds. Simultaneously with the collection of information in real-time, the computation of m is Savoy the proportion of uranium-235 by the formula (7). The calculated value for the external network interface 22 is transmitted to the database of the local computer network 23 control cascade installation. In the same database on the external network interface 24 is passed information about the reference value of the mass fraction of the isotope uranium-235 in the flow of uranium hexafluoride, obtained from the results of periodic measurements of the mass spectrometer 25, and information about the current time of the sample in the mass spectrometer. On the workstation network 23 periodically (not more than once in 30 days) is determined by the variance calculated by the formula (7) values with the results of the reference measurement. If the misalignment is greater than the set limit deviations (± 1 Rel.%), then on the workstation network 23 to reconcile the two results is recalculated calibration factor α1included in the calculation formula (7). External network interface 22 is adjusted coefficient α1sent in block 21 of the collection, management and processing of information.

The information output unit 20 every 10-200 seconds receive a signal about the value of the mass fraction of the isotope uranium-235 in the selected collector uranium plant (see figure 3-5).

In the measurement system (see figure 2) single-Board spectrometric device 26, which implements the controller of gamma-ray spectra, which contains all the necessary circuitry decision to perform precision spectrometry measurements, including dual high-voltage source voltage detection unit 6, spectrometric amplifier with gramasevaka circuits signal conditioning, key restorer baseline, rejector overlays, analog-to-digital Converter with a fixed conversion time, the buffer memory circuit interface to control settings and access devices to the internal interface bus 20.

Figure 3 as a specific example registered proposed method the change in the mass fraction of the isotope uranium-235 in the period of perestroika configuration diagram of the uranium plant with enrichment of 3.8% commercial product on the enrichment of 4.5% (solid line). Here plotted the results of the reference mass spectrometric measurement of the enrichment of uranium hexafluoride (point marker mass fraction of the isotope uranium-235), which are transmitted to the workstation local area network management cascade with an interval of two hours. The diagram above shows that the discrepancies with the results of the reference measurement is not more than ±1 Rel.% from the absolute value of the enrichment. Moreover, in the period of transition processes the samples to the mass spectrometer, as a rule, are not conducted, because the measurement data becomes obsolete more quickly than lasts for a time period of information processing and in the reference meter. The measurement system recorded the presence of oscillatory processes in the change of concentration of uranium-235 in the selected reservoir during the changeover of the circuit configuration of the plant, previously known methods of control have been noted.

Figure 4 shows the results of measuring changes in the enrichment of uranium hexafluoride in the restructuring scheme of the plant with the developments of energy uranium enrichment of 4.5 wt.% for the production of 1.5%. Practical work with the measurement system in transients showed (see figure 4)that the management of a cascade installation control mass fraction of the isotope uranium-235 in the selected reservoir proposed method allows to reduce time of perestroika plant configuration and to exclude the output of the enrichment of uranium hexafluoride for the required limits of concentration.

Figure 5 shows the variation in the enrichment 27 and 28 of uranium hexafluoride in the gas collector according to the results of measurement of parameters of the gas phase simultaneously in two time intervals.

Implementation of the above-described control method will allow you to respond quickly to emergency deviations enrichment flow of uranium hexafluoride to reduce the time realignment circuit configuration of the plant when changing enrichment and commodity uranium hexafluoride and to prevent the accumulation of non-conforming product.

1. The control method m is Savoy the proportion of the isotope uranium-235 in the gas phase of uranium hexafluoride including the measurement in the selected time interval of the intensity of gamma radiation from uranium-235, the temperature and pressure of the gas phase of uranium hexafluoride in the measuring chamber and the subsequent processing of the averaged measurement results by calculation, characterized in that in the measuring chamber create a duct of uranium hexafluoride and is measured in the time interval represented by the set of time segments, with calculated average values of the intensity of gamma radiation, the temperature and pressure of the gas phase of uranium hexafluoride in each time interval, and the results of measurements in the time interval calculated as an average value of the average values of measurements in time intervals; the intensity of the gamma radiation, the temperature and pressure when calculating the current value of the mass fraction of the isotope uranium-235 determined through averaging the measurement results in identical time intervals when you change the current time by an amount equal to the amount of time of the time interval, and the calculated value of the mass fraction of the isotope uranium-235 is referred to the current time, per time interval measurement.

2. The method according to claim 1, characterized in that the calculated value of the mass fraction of the isotope uranium-235 is referred to the current time, attributable either to the middle part or at the end or the beginning of the time interval.

3. The method according to claim 1, wherein the selected time interval are set equal time segments.

4. The method according to claim 1, characterized in that the magnitude of the time interval is chosen inversely proportional to the pressure of the gas phase in the measuring chamber.

5. The method according to claim 1, characterized in that the intensity of gamma radiation, the temperature and pressure of the gas phase of uranium hexafluoride define at least two selected time intervals.

6. The method according to claim 1 or 4 or 5, characterized in that the magnitude of the time interval ranges from 100 to 2000 C.

7. The method according to claim 1 or 3, characterized in that the amount of time segments is from 10 to 200 C.

8. The method according to claim 1, wherein periodically conduct a comparison of the calculated values of the mass fraction of the isotope uranium-235 from its reference dimension.

9. The method according to claim 1 or 8, characterized in that the estimated value for processing the averaged measurement results calculated by including the average values of the intensity of gamma radiation, temperature, pressure, and calibration factor is adjusted so that the calculated value of the mass fraction of the isotope uranium-235 has deviated from the reference measurement to a predefined limit value.

10. The method according to claim 9, characterized in that the limit value of the deviation is ± 1% Rel.

11. The method according to claim 9, characterized in that the estimated proportion correct calibration factor.

12. The method according to claim 1, characterized in that the measuring chamber is connected in parallel to the gas collector of uranium hexafluoride, and the gas manifold at the site of connection of the measuring chamber establish a narrowing device, such as a diaphragm.

13. The method according to claim 1, characterized in that the measurement of the intensity of gamma radiation is determined taking into account the background component under the main analytical peak characterizing the natural alpha decay of uranium-235.

14. The method according to claim 1, characterized in that the measurement of the intensity of gamma radiation is conducted at lock loop under the energy of the primary analytical peak characterizing the natural alpha-decay of the isotope uranium-235.

15. The method according to claim 1 or 14, characterized in that the measurement of the intensity of gamma radiation is in the energy interval 166-215 Kev.

16. The method according to claim 1 or 15, characterized in that the energy interval of measuring the intensity of gamma radiation is divided relative to the energy of the primary analytical peak characterizing the natural alpha decay of uranium-235, two subchannel.

17. The method according to claim 1 or 16, characterized in that the measurement of the intensity of gamma radiation is in the energy sub-166-15,7 Kev and 185,7-215 Kev.

18. The method according to item 16 or 17, characterized in that the signal-locked loop under the energy of the primary analytical peak is formed by the relative difference in the intensity of gamma radiation in the subchannels.

19. Measuring system for monitoring the mass fraction of the isotope uranium-235 in the gas phase of uranium hexafluoride containing the measuring chamber with the nozzle inlet and outlet, a detection unit, temperature sensors and pressure, is connected by the pipe inlet to the gas collector of uranium hexafluoride, the controller counters with electrical impulses and analyzer gamma-ray spectra, adapters signals, internal data bus, the block collection, management and processing of information, wherein the controller is further introduced at least three discriminator and one timer inputs discrimination connected to the output of the detecting unit, and the output of each discriminator is connected with a private entrance counter electrical impulses connected to a second input with the output of the timer, the timer outputs and adapters connected through line exchange of information with internal information bus, the block collection, management and processing of information on the external network interface connected to the computer network management.

20. Measuring system according to claim 19, characterized in that the measuring chamber Pat is the UBK release connected to a gas manifold of uranium hexafluoride.

21. Measuring system according to claim 19, wherein the local area network control via the second external interface network connected output channel reference probe mass fraction of the isotope uranium-235, such as a mass spectrometer.

22. Measuring system according to claim 19, characterized in that the output of the analyzer gamma-ray spectra adapter is connected to the input of the detection unit, the detection unit according to the channel information exchange is additionally connected to the internal data bus.

23. Measuring system according to claim 19, characterized in that the controller of gamma-ray spectra is made in the form of a single Board spectrometric device containing, in addition, circuit solutions for precision spectrometry measurements in the form of the amplifier channel, Converter charging pulse signals into a digital code, a buffer memory, a diagram of the interface for managing the parameters and connected across the input to output of the detection unit, one output to the internal data bus and the other to the detection unit.

24. Measuring system according to claim 19 or 20, characterized in that the conductivity of the nozzle inlet of the measuring chamber is greater conductivity of the outlet pipe.



 

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FIELD: power engineering; evaluating burnout margin in nuclear power units.

SUBSTANCE: proposed method intended for use in VVER or RBMK, or other similar reactor units includes setting of desired operating parameters at inlet of fuel assembly, power supply to fuel assembly, variation of fuel assembly power, measurement of wall temperature of fuel element (or simulator thereof), detection of burnout moment by comparing wall temperatures at different power values of fuel assembly, evaluation of burnout margin by comparing critical heat flux and heat fluxes at rated parameters of fuel assembly, burnout being recognized by first wall temperature increase disproportional relative to power variation. Power is supplied to separate groups of fuel elements and/or separate fuel elements (or simulators thereof); this power supplied to separate groups of fuel elements and/or to separate fuel elements is varied to ensure conditions at fuel element outlet equal to those preset , where G is water flow through fuel element, kg/s; iout, iin is coolant enthalpy at fuel element outlet and inlet, respectively, kJ/kg; Nδi is power released at balanced fuel elements (or simulators thereof) where burnout is not detected, kW; n is number of balanced fuel elements; Nbrn.i is power released at fuel elements (or element) where burnout is detected; m is number of fuel elements where burnout is detected, m ≥ 1; d is fuel element diameter, mm.

EFFECT: enhanced precision of evaluating burnout margin for nuclear power plant channels.

1 cl, 2 dwg

FIELD: nuclear fuel technology.

SUBSTANCE: invention relates to production of pelleted fuel and consists in controlling nuclear fuel for thermal resistance involving preparation for selecting pellets from nuclear fuel lot for measuring diameter, which preparation consists in dedusting. Selected pellets are placed in temperature-stabilized box together with measuring instrument. Diameter of each pellet is them measured and measurement data are entered into computer. Thereafter, pellets are charged into heat treatment vessel, wherein pellets are heated in vacuum at residual pressure not exceeding 7·10-2 Pa at heating velocity not higher than 10°C/min to 100-160°C and held at this temperature at most 2 h, whereupon heating is continued under the same conditions to 1470-1530°C and this temperature is maintained for a period of time not exceeding 4 h, after which hydrogen is fed with flow rate 2-6 L/min. Humidity of gas mix is measured in the heat treatment outlet. If humidity of gas mixture in the heat treatment outlet exceeds 800 ppm, hydrogen feeding is stopped and material is subjected to additional vacuum degassing at residual pressure below 7·10-2 Pa and held at 1470-1530°C in vacuum for further 4 h. Hydrogen feeding is the repeated at 2-6 L/min. If humidity of gas mixture in the heat treatment outlet is below 800 ppm, preceding temperature is maintained not longer than 2 h and raised to 1625-1675°C at velocity 40-60°C/h and then to 1700-1750°C at velocity 15-45°C/h. When outlet humidity of mixture is 500-750 ppm, hydrogen feeding is lowered to 1 L/min. Temperature 1700-1750°C is maintained during 24±2 h, after which pellets are cooled to 1470-1530ºC at velocity not higher than 10°C/min. Hydrogen is replaced with argon and cooling is continued to temperature not higher than 40°C, which temperature is further maintained. Outside diameter of each pellet from the selection is measured to find average diameter of pellets before and after heat treatment in order to calculate residual sintering ability. When this parameter equals 0.0-0.4%, total lot of pellets is used in fuel elements and in case of exceeding or negative residual sintering ability the total lot of pellets is rejected.

EFFECT: improved pellet quality control.

2 dwg

FIELD: atomic industry.

SUBSTANCE: proposed line is provided with computer-aided system for contactless control of flaw depth and profile on surface of fuel element can and on end parts including sorting-out device that functions to reject faulty fuel elements. This line is characterized in high capacity and reduced labor consumption.

EFFECT: enlarged functional capabilities, improved quality of fuel elements.

1 cl, 2 dwg

FIELD: analog computer engineering; verifying nuclear reactor reactivity meters (reactimeters).

SUBSTANCE: proposed simulator has m threshold devices, m threshold selector switches, m series-connected decade amplifiers, m electronic commutators, n - m - 1 series-connected decade frequency dividers, first group of m parallel-connected frequency selector switches, second group of n - m frequency selector switches, and group of n - m parallel-connected mode selector switches. Integrated inputs of threshold selector switches are connected to output of high-voltage amplifier and output of each threshold selector switch, to input of respective threshold device; output of each threshold device is connected to control input of respective electronic commutator; inputs of electronic commutators are connected to outputs of decade amplifiers and outputs are integrated with output of group of mode selector switches and with input of voltage-to-frequency converter; output of inverting amplifier is connected to input of first decade amplifier and to that of group of mode selector switches; input of first group of frequency selector switches is connected to output of voltage-to-frequency converter and to input of first decade frequency divider and output, to integrated outputs of first group of frequency selector switches and to input of division-chamber pulse shaper input; each of inputs of second group of frequency selector switches is connected to input of respective decade frequency divider except for last one of this group of switches whose input is connected to output of last decade frequency divider; threshold selector switches and frequency selector switches of first group, as well as m current selector switches have common operating mechanism; mode selector and frequency selector switches of second group have common operating mechanism with remaining n - m current selector switches. Such design makes it possible to realize Coulomb law relationship at all current ranges of simulator for current and frequency channels.

EFFECT: ability of verifying pulse-current input reactimeters by input signals adequate to signals coming from actual neutron detector.

2 cl, 1 dwg

FIELD: the invention refers to analytical chemistry particular to determination of general hydrogen in uranium dioxide pellets.

SUBSTANCE: the installation has an electrode furnace with feeding assembly , an afterburner, a reaction tube with calcium carbide, an absorption vessel with Ilovay's reagent for absorption of acetylene, a supply unit. The afterburner of hydrogen oxidizes hydrogen to water which together with the water exuding from pellets starts reaction with carbide calcium. In result of this equivalent amount of acetylene is produced. The acetylene passing through the absorption vessel generates with Ilovay's reagent copper acietilenid which gives red color to absorption solution. According to intensity of color of absorption solution the contents of general hydrogen are determined.

EFFECT: simplifies construction of the installation, increases sensitivity and precision of determination of the contents of hydrogen in uranium dioxide pellets.

2 cl, 1 dwg

FIELD: analyzing metals for oxygen, nitrogen, and hydrogen content including analyses of uranium dioxide for total hydrogen content.

SUBSTANCE: proposed analyzer depending for its operation on high-temperature heating of analyzed specimens has high-temperature furnace for heating uranium dioxide pellets and molybdenum evaporator; molybdenum evaporator is provided with water-cooled lead-in wire, and molybdenum deflecting screen is inserted between molybdenum evaporator and furnace housing.

EFFECT: simplified design of electrode furnace, reduced power requirement.

1 cl, 1 dwg

FIELD: identifying o spent fuel assemblies with no or lost identifying characteristics for their next storage and recovery.

SUBSTANCE: identifying element is made in the form of circular clip made of metal snap ring or of two metal semi-rings of which one bears identification code in the form of intervals between longitudinal through slits. Clip is put on fuel assembly directly under bracing bushing and clip-constituting semi-rings are locked in position relative to the latter without protruding beyond its outline. For the purpose use is made of mechanical device of robot-manipulator type. Identification code is read out by means of mechanical feeler gage and sensor that responds to feeler gage displacement as it engages slits. Identifying elements are installed under each bracing bushing.

EFFECT: ability of identifying fragments of spent fuel assembly broken into separate parts before recovery.

10 cl, 4 dwg

FIELD: nuclear power engineering.

SUBSTANCE: proposed invention may be found useful for optimizing manufacturing process of dispersion-type fuel elements using granules of uranium, its alloys and compositions as nuclear fuel and also for hydraulic and other tests of models or simulators of dispersion-type fuel elements of any configuration and shape. Simulators of nuclear fuel granules of uranium and its alloys are made of quick-cutting steel alloys of following composition, mass percent: carbon, 0.73 to 1.12; manganese and silicon, maximum 0.50; chromium, 3.80 to 4.40; tungsten, 2.50 to 18.50; vanadium, 1.00 to 3.00; cobalt, maximum 0.50; molybdenum, 0 to 5.30; nickel, maximum 0.40; sulfur, maximum 0.025-0.035; phosphor, maximum 0.030; iron, the rest.

EFFECT: enhanced productivity, economic efficiency, and safety of fuel element process analyses and optimization dispensing with special shielding means.

1 cl, 3 dwg

FIELD: operating uranium-graphite reactors.

SUBSTANCE: proposed method for serviceability check of process-channel gas gap in graphite stacking of RBMK-1000 reactor core includes measurement of diameters of inner holes in graphite ring block and process-channel tube, exposure of zirconium tube joined with graphite rings to electromagnetic radiation, reception of differential response signal from each graphite ring and from zirconium tube, integration of signal obtained, generation of electromagnetic field components from channel and from graphite rings, separation of useful signal, and evaluation of gap by difference in amplitudes of signals arriving from internal and external graphite rings, radiation amplitude being 3 - 5 V at frequency of 2 - 7 kHz. Device implementing this method has calibrated zirconium tube installed on process channel tube and provided with axially disposed vertically moving differential vector-difference electromagnetic radiation sensor incorporating its moving mechanism, as well as electronic signal-processing unit commutated with sensor and computer; sensor has two measuring and one field coils wound on U-shaped ferrite magnetic circuit; measuring coils of sensor are differentially connected and compensated on surface of homogeneous conducting medium such as air.

EFFECT: ability of metering gas gap in any fuel cell of reactor without removing process channel.

2 cl, 9 dwg

A fuel assembly // 2242058
The invention relates to the field of thermophysical studies and can be used for studies of temperature regimes of fuel elements (FE) of nuclear reactors, in the study of different emergency modes of fuel assemblies (FA) on electrically heated stands

FIELD: inspection of large-sized goods.

SUBSTANCE: radiographic inspection system has radiation source, detector system, multichannel signal processing system and transportation system for displacement of objects to be inspected. Radiation source has electron accelerator, conversion target and local radiation protecting aid made of metal units. Protection aid has two-position X-ray radiation collimator made in form of rotary metal cylinder provided with narrow slot to let X-ray radiation pass in the position of radiation and overlap the radiation at the calibration position. Signal processing system has means for calibrating each channel.

EFFECT: high penetration ability; improved efficiency of operation.

2 dwg

FIELD: object investigations in dissipated or passed radiation.

SUBSTANCE: broad irradiating beam covering entire object to be investigated is used for inspecting this object with passed or dissipated penetrating radiation. Novelty is use of beam with time-variable radiation intensity distribution in its cross-sectional area ensured by moving screen heterogeneous for used radiation across beam. Resultant definition depends on penetrating radiation measurement quantization step upon interacting with object at essential increase in effectiveness of source energy use.

EFFECT: enhanced scan speed due to effective use of source power or reduced power of source at same scan speed.

19 cl, 19 dwg

FIELD: measurement engineering.

SUBSTANCE: sample of saturated thickness tested material is irradiated by monochromatic gamma-ray or X-ray radiation and intensities of coherent dissipated primary radiation of matter being non-coherent dissipated. Concentration of element in tested sample is calculated from analytical signal which has to be the relation of mentioned intensities registered simultaneously or subsequently.

EFFECT: improved precision of measurement.

3 dwg

FIELD: radiation methods of testing.

SUBSTANCE: tested object is subject to illumination of narrow low-divergent beam of penetrating radiation and radiation passed through object is registered by means of coordinate-sensitive detectors. Structure of matters composing the object is identified from small-angle coherent dissipation of radiation passed through object. Distribution of radiation intensity across the beam is registered when object is present and absent correspondingly. Attenuation factor of penetrating radiation is determined for center of the beam by means of comparing intensities of incident beam and passed beam. Intensity distribution curve is normalized for incident radiation at the area of central peak of diffraction for angle of dissipation by attenuation factor and is subtracted from curve of distribution of radiation passed through the object.

EFFECT: higher quality of building of internal structure of object.

1 tbl, 1 dwg

FIELD: medical engineering.

SUBSTANCE: method involves forming X-ray radiation flow, letting pass it through filter transparent mainly for high power radiation spectrum portion of X-ray tube. The filter is mounted in front of volume under study. The X-ray radiation flow is directed to transducers for recording X-ray radiation quanta. Data are read from the transducers and image is built by applying computer software. An additional X-ray radiation flow is let pass through the filter transparent mainly for low power radiation spectrum portion of X-ray tube and mounted in front of volume under study. Another embodiment of the invention is characterized with scanning X-ray radiation flow being produced. High power radiation spectrum portion is directed to a transducers row for recording X-ray radiation quanta. X-ray radiation flow is additionally let pass through the filter transparent mainly for low power radiation spectrum portion of X-ray tube and mounted in front of volume under study. The X-ray radiation flow is directed to an additional transducers row for recording X-ray radiation quanta set in parallel to the available row.

EFFECT: high quality of diagnosis.

FIELD: examination of baggage; customs inspection.

SUBSTANCE: according to the method, the object should be inspected inside one local area G (m). Detection unit is divided to lower and higher degrees of inspection. Coordinates of local area are determined at lower degree of inspection; electron diffractometer is oriented to the local area at higher degree of inspection. Explosives can be detected, for example, by using x-ray diffraction analysis. Electron diffractometer has collimating-detection system, which can be regulated, in height and in side direction at higher degree of inspection. Diffractometer also has X-ray radiation source, which is matched with collimating-detection system, which can be oriented at side direction. Collimating-detection system has one collimator max and one detector. Collimator is provided with conical widened slit, which reproduces preset angle Θ of dissipated radiation.

EFFECT: higher speed of detection of prohibited luggage.

14 cl, 6 dwg

FIELD: analysis of water and organic solutions.

SUBSTANCE: sensor has multi-channel structure in form of length 1 of poly-capillary pipe with through capillary, forming micro-channels, which are filled with two layers of non-mixing substances. One layer 4 is formed by water or water solution and other 3 - by organic substance. In first of said layers into micro channels micro-granules 5 of absorbent are placed.

EFFECT: higher efficiency, lower costs.

27 cl, 14 dwg

FIELD: measuring engineering.

SUBSTANCE: method comprises recording the flux of slow neutrons, which are generated by irradiating a matter to be tested by fast neutrons from a source, with the use of two groups of detectors-counters of slow neutrons whose maximums of the spectral sensitivity are spaced within the energy range of the moderate neutrons, e.g., with the use of a cadmium filter, measuring the output signals from each group of detectors in the absence of the material to be tested and after supplying material with known humidity, and determining humidity of the material from the formula proposed.

EFFECT: reduced error of determining humidity.

FIELD: inspection aids.

SUBSTANCE: device has first modular cabin unit inside which radiation source in mounted for generating penetrating radiation beam to penetrate inspected container, second modular cabin unit inside which detectors are mounted for detecting penetrating radiation beam through inspected container as well as for forming corresponding radiographic signals. First and second units are disposed at some distance to each other to form inspection aisle. Modular portal unit is connected with first modular cabin unit and second modular portal unit to form portal frame made for finding at embracing position above the container inspected. Portal frame moves in accordance with inspected container along inspection aisle. First modular cabin unit, second modular cabin unit and modular portal unit are made as separate modular units connected together for disconnection in inspection area.

EFFECT: ability of quick mounting and dismounting of device; simplified design.

10 cl, 2 dwg

FIELD: mechanical engineering; radiation method of inspection of materials and items.

SUBSTANCE: centering mount has housing inside which the laser is disposed as well as first reflector mounted onto axis of laser in front of exit window of X-ray radiator is the point where axis of laser crosses axis of X-ray beam, second reflector mounted onto axis of laser outside the projection of exit window of X-ray reflector for rotation relatively axis being perpendicular to plane formed by axes of laser beam and X-ray. Device also has aids for indicating focal length made in form of pointer provided with scale fixed onto housing of centering mount. Flat collimated laser beam forming system is mounted in front of laser. Laser beam propagates along plane being parallel to vertical plane crossing longitudinal axis of X-ray radiator. The axis is at the same time perpendicular to vertical plane crossing axis of X-ray beam. The second reflector is mounted at the exit of system at laser axis. Beam splitter is mounted between first and second reflectors. In front of the beam splitter there is the second semiconductor laser which is mounted onto axis being perpendicular to axis of laser to cross its point of crossing with beam splitter.

EFFECT: improved precision of measurements; simplified application.

4 dwg

FIELD: measurement technology.

SUBSTANCE: several γ-radiation sources are mounted onto closed frame of balance. Corresponding γ-ray detectors are mounted under the frame. Transporter is placed between detectors and sources. Output voltages U0 and Ui of γ-ray detector are measured at presence and absence of material. Values of U0 and Ui are introduced into data processing unit which is connected γ-ray detector. Speed Vi of transporter-placed transportation tape is measured by means of meter and value of Vi is introduced into data processing unit which is connected with speed meter. Total weight W of materials subject to transportation during specific period of time is calculated from relation Differences in nuclear weights are specified by the fact that value of K factor using for calculation of formula F=K*Ln(Ui/U0) can be calibrated depending on changes in loads of materials, different positions of materials located onto the band of transporter, different shape of accumulation of materials and dissipation factor.

EFFECT: improved precision of measurement.

7 cl, 10 dwg

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