RU2652521C2 - Laser system for measuring a steam containment in the heater of nuclear energy reactor - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention relates to nuclear power engineering and laser measuring equipment and is intended for use in nuclear power reactors of RBMK and VVER type for the rapid measurement of the physical characteristics of the coolant, in particular, the measurement of the vapor content in the coolant in the core of nuclear reactors with a water coolant. Laser measuring system contains optical sensors, located in the coolant pipeline and in the core of the nuclear reactor, connected by fiber-optic lines with measuring equipment, taken to a safe zone for a distance of 1,000 meters from the nuclear reactor. Optical equipment of the laser measuring system contains laser generators, photodetector units, fiber optic lines, controlled optical filters and an analogue model of a nuclear reactor, that provides continuous in-situ modeling of the optical characteristics of the coolant of a controlled nuclear reactor.

EFFECT: technical result is an increase in the accuracy of measuring the vapor content in the coolant of the nuclear power reactor at various points in the coolant circuit and in the core of the nuclear reactor, an increase in the reliability and credibility, of the results obtained for measuring the coolant parameters.

7 cl, 21 dwg

Description

The invention relates to nuclear energy and measuring laser technology and is intended for the operational measurement of the physical characteristics of the coolant, in particular, the measurement of the vapor content in the coolant in the core of RBMK and VVER nuclear reactors. RBMK is a high-power channel (boiling) reactor. VVER - water-water power reactor. The laser system continuously measures the density of the coolant and the level of vaporization in the thickness of the coolant in the core of a nuclear reactor with an aqueous coolant. This provides continuous monitoring of the level of the steam reactivity coefficient of a nuclear reactor in order to prevent the possibility of thermal overload of a nuclear reactor and a thermal explosion similar to the Chernobyl accident.

In water reactors of the WWER and RBMK type, water, which is a coolant, simultaneously serves as an absorber and moderator of neutrons. Therefore, the physical and chemical characteristics of the coolant determine the operating mode of a nuclear reactor and are an important factor in controlling a nuclear reactor. In the RBMK reactor, water boils inside the reactor and partially turns into steam, which has a lower density and is the worst moderator and neutron absorber compared to water. Therefore, the level of vaporization in the coolant in the core of a nuclear reactor determines the level of steam reactivity of the reactor - the so-called steam reactivity coefficient, which is an integral part of the total reactivity of a nuclear reactor. For effective control of a nuclear reactor and ensuring its safe operation, constant monitoring of the steam reactivity of the reactor is necessary, which can be ensured by continuous measurement of the density of the coolant and the level of vapor content at various individual points in the core of the nuclear reactor. To date, this problem has not been fully resolved. It provides only control of the parameters of the steam at the outlet of the reactor installation, which is not enough, since it characterizes the integral level of vaporization in a nuclear reactor. Moreover, in certain areas of the reactor core, the level of vaporization can exceed acceptable values, which can lead to a positive steam reactivity coefficient, the appearance of positive feedback in reactivity, in which an increase in reactor power causes an increase in vaporization and leads to further even greater reactor power. This leads to rapid thermal overload of the reactor and can cause a thermal explosion of the reactor, as happened in the Chernobyl accident. In VVER-type nuclear reactors, boiling water in the coolant and the formation of vapor bubbles is unacceptable and indicates an emergency operation of the reactor. Therefore, the proposed system in VVER reactors can be used as a safety device that continuously monitors the density of the coolant and quickly signals the occurrence of an emergency operation of a nuclear reactor. Thus, measuring the density of the coolant and the level of vaporization in the thickness of the coolant in certain areas of the active zone of a nuclear reactor with high accuracy and efficiency is an urgent problem and an important factor in controlling the operation and ensuring the safety of a nuclear reactor.

Currently, there are several methods for determining the level of vaporization during the boiling of liquids and water. A known method and device for determining the boiling of a liquid according to the patent of the Russian Federation No. 2065604 from 08.20.1996, [1]. The method is based on measuring the noise level in a liquid using ultrasonic sensors, and the moment of boiling and bubble boiling is determined by the maximum noise level. The disadvantages of the method and device include low accuracy and low noise immunity. The main disadvantage is the inability to use the data of the method and device for operation in a nuclear reactor. A known method for determining bubble boiling according to the patent of the Russian Federation No. 2238547 from 10.20.2004, [2]. The method is based on monitoring a physical quantity, for example, conductivity or dielectric constant in a liquid, and determining the moment of boiling by a sharp change in the variable component of the measured value by means of conductivity sensors and dielectric permittivity sensors placed in the liquid. The disadvantages of this method include the inability to accurately determine the level of vaporization and, accordingly, the density of the liquid, as well as the inability to use devices that implement this method in the active zone of a nuclear reactor. A known method of inertialess control of the vapor content in the coolant of a nuclear reactor according to the patent of the Russian Federation No. 2167457 [3]. The method is based on the placement in the coolant of the collector and emitter of betta electrons. The emitter is based on Strontium-90, which, during radioactive decay, transforms into the short-lived radioactive isotope Yttrium-90, which emits beta-electrons during beta decay. The latter pass through the coolant layer and are collected on the collector. The current from the collector is fed to the pre-converter and then to the measuring device. The magnitude of the current determines the level of vapor content in this section of the coolant. The disadvantages of this method and the implementing device include low accuracy in determining the level of vapor content due to the lack of information on the exact value of betta electrons emitted from the emitter under conditions of a high level of radiation in the core of a nuclear reactor. Of great complexity is also the determination (measurement) of the magnitude of the direct electric current from the collector and the transmission of this information to a considerable distance in the harsh temperature and radiation conditions characteristic of the active zone of a nuclear reactor, in which it is impossible to ensure the continuous operation of modern electronic measuring instruments. The known method and channel for detecting the boiling of the coolant in the core of the WWER reactor according to the patent of the Russian Federation No. 2437176 [4]. The method includes evaluating neutron flux fluctuations, isolating, processing, and evaluating signals from neutron detectors over the entire assembly height of the fuel assembly, compensating for interference and spurious signals present in the VVER core. The detection channel includes neutron detectors, which are direct charge sensors distributed over the entire height of the controlled fuel assembly, and also contains bandpass filters located in the reactor core, and signal processing units. According to the method, the neutron flux fluctuations are recorded against the background of noise and interference of the reactor core, and the presence of boiling in the coolant is determined by exceeding the fluctuation level above a certain predetermined limit. The disadvantages of this method and the implementing device include the low accuracy of determining the vapor content of the coolant, as well as the low reliability of the results. The vapor content level is determined indirectly by exceeding the fluctuations of the neutron flux above a certain limit established by calculation. At the same time, the determination of the vapor content level is necessary in order to prevent precisely this unacceptable increase in reactor power fluctuations characteristic of emergency reactor operation in a timely manner. It can be argued that the information obtained in this method is belated and does not fully ensure the safety of a nuclear reactor. The disadvantage of the device that implements the method is the placement of the measuring units in the reactor core, which significantly reduces the accuracy and reliability of the measurements.

A known method of determining the steam reactivity coefficient at nuclear power plants with reactor plants of the RBMK type according to the patent of the Russian Federation No. 2136062 [5]. The method includes monitoring the processes of changing the neutron-physical parameters of the reactor installation when the feed water flow changes, while processes with a natural change in feed water flow due to the operation of automatic water level controllers and satisfying the stabilization conditions for at least 2 minutes, the absence of rod movement are selected CPS for 2 minutes, and the steam reactivity coefficient is determined from the ratio of the perturbation of the feedwater flow to the change in the average volumetric change I current feedwater flow. The disadvantages of this method include the low efficiency of obtaining final information about the parameters of the operating mode of the reactor installation, low accuracy and low reliability of the resulting estimate of the steam reactivity of the reactor installation, which is due to an indirect assessment of the current steam content, the presence of a number of random and uncontrolled factors affecting the flow measurement process and fluctuations in feedwater and estimates based on this change in the vapor content in the reactor installation. As a result of this, this method does not provide the necessary level of safety for the operation of nuclear power plants with this type of reactor installation.

Thus, the known methods and devices do not solve the problem of accurately determining the level of vaporization in a liquid and are not suitable for use in a nuclear reactor. A known method and system for controlling steam quality according to US patents [6] and the Russian Federation [7]. The method includes emitting an optical sensor with a number of wavelengths, passing them through wet steam inside the turbine and measuring with an optical sensor the steam intensity corresponding to each of the wavelengths, based on which the ratio of the intensities of wet and dry steam is calculated based on which the quality parameters of the steam inside the steam are judged turbines. The system implementing the method comprises a steam turbine, the optical emitter and the optical detector being located inside the turbine. The disadvantages of this system include the low accuracy and low reliability of the obtained results of measuring the parameters of the steam, which is due to the lack of control of the parameters of the optical radiation generated by the optical emitter inside the steam turbine, as well as the lack of sensitivity control of the optical detector at various wavelengths, also located inside the steam turbines. The physical conditions inside the steam turbine do not allow to ensure and guarantee the efficiency, accuracy and reliability of modern electronic equipment. It should be noted the impossibility of using this system to operate as part of a nuclear reactor.

The most appropriate method for solving the problem of measuring fluid parameters under the conditions of a coolant in a nuclear reactor is the optical method for measuring the characteristics of a coolant, proposed by the authors in [8], [9] and implemented in measurement systems according to RF patents No. 2594364 dated 05/14/2015 [10] and No. 2606369 dated May 16, 2015 [11]. In these systems, the coolant is exposed to laser radiation and the characteristics of the radiation transmitted through the coolant layer are measured. The measured parameters of the laser radiation transmitted through the coolant allow us to estimate the level of vaporization and the density of the coolant, as well as provide an operational measurement of the concentration of boric acid in the coolant. These measurement systems are designed to operate in a nuclear reactor in the presence of radioactivity, high temperatures and pressure. The ability to work in a nuclear reactor is provided by the removal of measuring equipment from the reactor zone, in which only an optical measuring unit is placed, connected by a fiber line to the measuring equipment. As a prototype, the measurement system closest in technical implementation to the patent of the Russian Federation No. 26066369 [11] was selected. The measurement system contains the first and second laser generators, two optical cuvettes, a photodetector unit, laser radiation meters based on photodetector units, an optical modulator that functions as a controlled optical filter, fiber adapters, fiber optic lines, information processing and control units, two optical switches based on remote mirrors, corner optical reflectors, translucent and reflective mirrors, optical attenuators. The disadvantages of this measuring system include the limited accuracy of measuring the level of vapor content of the coolant due to the lack of a reference object with a known level of vapor content, with which the measured optical parameters of the coolant are compared in a nuclear reactor. In this known measuring system, the determination of vapor content was carried out based on the use of special tables linking the vapor content level with the optical absorption of radiation transmitted through the studied liquid medium, for example, an aqueous medium at different wavelengths of optical radiation. This method allows you to measure the vapor content when using, for example, two different wavelengths of the optical range, however, the accuracy and reliability of such a measurement are insufficient for use in critical measurements of the coolant in a nuclear reactor.

The aim of this invention is to overcome these drawbacks of known measuring systems, increase the accuracy of measuring the vapor content in the coolant in the core of a nuclear reactor under conditions of high radiation, temperature and pressure, increase the reliability of the measuring equipment in a nuclear reactor and ensure high reliability of the results, preventing thermal overloading a nuclear reactor and eliminating the possibility of thermal explosion. The goal is achieved by measuring the optical parameters of the coolant with the help of several optical sensors placed individually or compactly in the form of a triad at one or more points of the coolant, as well as using a special analog model of a nuclear reactor, the optical parameters of which are measured simultaneously with the measurement of optical parameters of the coolant of a nuclear reactor and using the same optical measuring units and elements.

Achievable new technical result is an increase in the accuracy of measuring the vapor content in the coolant of a nuclear power reactor at various points in the coolant circuit and in the core of a nuclear reactor, an increase in the reliability and reliability of the results of measuring the parameters of the coolant.

A new technical result is achieved as follows.

1. In a laser system for measuring the vapor content in the coolant of a nuclear power reactor containing the first and second laser generators, the first and second laser radiation meters, the first and second optical switches, the first fiber adapter connected to the first fiber-optic line, the first optical sensor, located in the coolant pipe of a nuclear power reactor and comprising a first beam expander and a first optical reflector sequentially installed at a fixed distance It also contains five translucent and one reflective mirrors, a control unit connected to an information processing unit, a first photodetector unit optically coupled to a first controlled optical filter, the optical input of which is connected via a semitransparent mirror to the first input of the first optical switch, and the outputs of laser generators through the first reflective and translucent mirrors are connected optically to the first input of the first optical switch, the optical output of the first optical the switch by means of the first fiber adapter and the first fiber optical line is connected to the optical input of the first beam expander in the first optical sensor, the control inputs of the first and second optical switches, the first and second laser generators are connected to the control unit, the first and second laser radiation meters are connected to the processing unit information, the output of the first photodetector unit is connected to the information processing unit, the outputs of the first and second laser generators by means of a translucent of the mirrors are connected respectively to the inputs of the first and second laser radiation meters, the second and third optical sensors, three optical shutters, the second and third, photodetector blocks, the second and third controlled optical filters, the third and fourth optical switches, and the fast Fourier transform (FFT) are introduced ), seven fiber-optic lines, seven fiber adapters, an optical illuminator, a television camera, a second reflective and two translucent mirrors, as well as an analog model of a nuclear reactor, introduced neighing container filled with water, with the fourth, fifth and sixth optical sensors placed in it, a heating element, a temperature sensor, two ultrasonic exciters and a fan, while the analog model is equipped with input and output optical windows, the second, fourth and fifth optical sensors are similar the first optical sensor and contain a beam expander and an optical reflector, the third and sixth optical sensors contain located on the same optical axis at a fixed distance dr d from each other beam expanders connected to fiber optic lines, the second and third optical sensors are located together with the first optical sensor in the coolant pipe of the nuclear reactor, the optical input of the second photodetector through a second controlled optical filter and a newly introduced translucent mirror is connected to the optical input of the third optical switch, the first optical shutter is mounted on the optical axis between the optical output of the first laser generator and the optical input of the first about the optical switch and optically connects the outputs of the laser generators with the optical input of the first optical switch, the optical input of the second optical shutter by means of three translucent mirrors and the first reflective mirror is connected simultaneously with the optical outputs of the first and second laser generators, the optical output of the second optical shutter is optically connected to the optical input a third optical switch, an optical input of a third optical shutter by a second reflective A mirror, three translucent mirrors and a first reflective mirror are optically coupled simultaneously with the optical outputs of the first and second laser generators, the optical output of the third optical shutter is optically connected to the optical input of the fourth optical switch, the optical output of the third optical switch is connected via the second fiber adapter and fiber-optic line with the optical input of the second beam expander of the second optical sensor, the optical output of the fourth optical switch through the third fiber adapter and the fiber optic line is optically connected to the optical input of the third beam expander in the third optical sensor, and the second optical output of the fourth optical switch is optically connected via the sixth fiber adapter and the fiber optic line to the seventh beam expander of the sixth optical sensor, in the analog model of a nuclear reactor, the second optical output of the first optical switch is optically coupled through a fourth fiber adapter and a fiber optic line with an optical input of a fifth beam expander in a fourth optical sensor housed in an analog model of a nuclear reactor, a second optical output of a third optical switch by means of a fifth fiber adapter and a fiber optic line is optically coupled to an optical input of a sixth beam expander in a fifth optical the sensor placed in the analog model of a nuclear reactor, the optical output of the fourth beam expander in the third optical sensor through a fiber optic line and in of the eightth fiber adapter is optically coupled to the first optical input of the second optical switch, the optical output of the eighth beam extender of the sixth optical sensor is optically coupled through the fiber optic line and the seventh fiber adapter to the second optical input of the second optical switch, the optical output of the second optical switch is connected to the optical input of the third controlled optical filter, the output of which is optically coupled to the optical input of the third photodetector, outputs the second and third photodetector units are connected to the inputs of the information processing unit, the output of the third photodetector unit is additionally connected to the input of the fast Fourier transform unit, the output of which is connected to the information processing unit, the control inputs of the third and fourth optical switches are connected to the control unit, the control inputs of the second and third controlled optical filters are connected to the control unit, the control inputs of three optical shutters are connected to the control unit, television the amer and the optical illuminator are located on the same optical axis passing through the volume of the container of the analog model of a nuclear reactor, moreover, the optical input of the television camera is optically connected to the first optical illuminator of the analog model, and the optical output of the optical illuminator is connected to the second optical illuminator of the analog model, the output of the television camera is connected to the information processing unit, the optical illuminator is connected to the control unit, the first and second ultrasonic exciters are connected to the control the generator, the input of which is connected to the control unit, the heating element and the fan are connected to the control unit, the temperature sensor is connected to the information processing unit.

2. In the system according to paragraph 1, the optical reflectors are made on the basis of a multi-element matrix of corner optical reflectors.

3. In the system according to paragraph 1, the beam expander is placed in a waterproof box equipped with an optical porthole.

4. In the system of claim 1, the optical sensor comprises sequentially optically coupled beam expander, a rotary reflective mirror and an optical reflector, the rotary optical mirror and the optical reflector are provided with fairings.

5. In the system of claim 1, the second laser generator is configured to tune the wavelength of the generated laser radiation within the visible wavelength range.

6. In the system of claim 1, the controllable optical filter is based on an acousto-optic cell operating in the visible wavelength range.

7. In the system of claim 1, the optical sensor comprises sequentially optically coupled input beam expander, first optical reflective mirror, second optical reflective mirror and output beam expander.

In the presented claims of the laser measuring system in the restrictive part of the formula contains one photodetector, since the remaining photodetectors in the prototype serve as laser radiation meters and are presented under this name in the aforementioned restrictive part.

In FIG. 1 shows a block diagram of the proposed laser system for measuring the vapor content in the coolant of a nuclear power reactor. Numbers denote the following elements.

1 The first laser generator.

2 Second laser generator.

3 The first laser radiation meter (LI).

4 Second laser radiation meter.

5 The first translucent mirror.

6 Second translucent mirror.

7, 8, 9 - Translucent mirrors (third, fourth and fifth translucent mirrors).

10. The first reflective mirror.

11. The first optical switch.

12. The first fiber adapter.

13. The first fiber optic line.

14. The first beam expander.

15. The first optical reflector (elements pos. 14 and 15 comprise the first optical sensor).

16. The first photodetector unit (FPB).

17. The first controlled optical filter.

18. The second optical switch.

The laser measuring system also contains the following elements:

70. The control unit.

71. Information processing unit.

Next, the numbers indicate the newly entered elements:

19. The first optical shutter.

20. The second beam expander.

21. The second optical reflector (elements pos. 20 and 21 constitute the second optical sensor).

22. Third extender pike.

23. The fourth beam expander (elements pos. 22 and 23 make up the third optical sensor).

The first, second and third optical sensors are located in the coolant pipe pos. 66.

24. The second fiber optic line.

25. Third fiber optic line.

26. The second fiber adapter.

27. Third fiber adapter.

28. Fourth fiber optic line.

29. The third optical switch.

30. Fourth optical switch.

31. The second optical shutter.

32. The third optical shutter.

33. The second controlled optical filter.

34. The second photodetector unit.

35. The third photodetector unit.

36. The third controlled optical filter.

37. Fourth fiber adapter.

38. Fifth fiber adapter.

39. Sixth fiber adapter.

40. An analogue model of a nuclear power reactor.

152. A container filled with water, an analog model of a nuclear reactor.

The analogue model consists of the following elements, indicated by positions 41-49 and 55, 56 and placed in a container filled with water, pos. 152.

41. Fifth beam expander.

42. The third optical reflector (elements pos. 41 and 42 make up the fourth optical sensor).

43. Sixth beam expander.

44. Fourth optical reflector (elements pos. 43 and 44 make up the fifth optical sensor).

45. Seventh beam expander.

46. The eighth beam expander (elements pos. 45 and 46 make up the sixth optical sensor).

47. Heating element.

48. 49 - Ultrasonic pathogens.

50. Control generator.

51. Optical illuminator.

52. A television camera.

53. 54 - Optical portholes.

55. The fan.

56. Temperature sensor.

Further, the laser system contains the following elements.

57. Fifth fiber optic line.

58. Sixth fiber optic line.

59. Seventh fiber optic line.

60. Seventh fiber adapter.

61. The eighth fiber adapter.

62. The eighth fiber optic line.

63. Sixth translucent mirror.

64. Seventh translucent mirror.

65. The second reflective mirror.

66. The coolant pipe in which the first, second and third optical sensors are placed (shown conditionally). Fastenings of optical sensors in this pipeline are not shown, and also elements of an output of fiber-optic lines from the pipeline (bushings) are not shown.

67. Block fast Fourier transform (FFT).

68. 69 - arrows showing the direction of movement of the coolant and vapor bubbles.

70. The control unit.

71. Information processing unit.

152. A container filled with water, in which elements of the model analogue 40 of a nuclear reactor are placed.

In FIG. 1, the optical axes of the optical sensors are parallel to the plane of the drawing. The direction of the pipeline 66 and the direction of movement of the coolant 68 in the pipeline are parallel to the plane of the drawing. The optical axes of the optical sensors are perpendicular to the direction of the pipeline.

In FIG. 2 separately presents the design of the optical sensor of the first (reflective) type, containing the beam expander 14 and the optical reflector 15. Here, the numbers denote the elements:

72. The supporting frame.

73. The optical axis of the optical sensor; d is the thickness of the frame, "a" is the direction of movement of the coolant.

In FIG. 3, the construction of an optical sensor of the second (pass-through) type, comprising two beam expanders 22 and 23, is separately presented.

74. Bearing frame.

75. The optical axis of the optical sensor.

Identical elements of FIG. 1 are marked with the same numbers.

FIG. 4 is a side view of the optical sensor of FIG. 2 view along arrow "a".

In FIG. 5 shows the relative positioning of three optical sensors in the coolant pipe (pos. 66 in Fig. 1). Side view parallel to the optical axes of the optical sensors (view along the optical axes of the optical sensors). The numbering corresponds to FIG. one.

An option is presented when the optical axes of the optical sensors are parallel, but not in the same plane. Fasteners for optical sensors are not shown.

66. The coolant pipe in which the optical sensors are located.

The direction of the pipeline parallel to the plane of the drawing. The outputs of the fiber optic lines from the pipeline 66 are shown conditionally. The optical axes of the optical sensors are perpendicular to the direction of the pipeline and perpendicular to the plane of the drawing.

76. This position marks the conditionally shown bushings that ensure the exit of fiber optic lines from the pipeline 66, in which the optical sensors are located. Pos. 68 - the direction of the pipeline 66 and the direction of movement of the coolant.

As the coolant pipe 66, in which the optical sensors are located, the main total pipe of the technological channels of the nuclear reactor or the bypass of this pipe (bypass pipe) can be used below.

In FIG. 6 shows a block diagram of the operation of the first optical sensor. The numbering of the positions corresponds to FIG. one.

In FIG. 7 is a flowchart of a third optical sensor. The numbering of the positions corresponds to FIG. one.

In FIG. 8 is a design diagram of a beam expander placed in a waterproof box. The numbers denote the elements:

77. The lens.

78. Fiber optic line.

79. The case of a waterproof box.

80. Protective glass.

In FIG. 9 is a diagram of a power unit of a nuclear power plant with a RBMK type nuclear reactor. The numbers denote the following elements of the reactor and power unit.

81. Technological (fuel) channels of RBMK.

82. Channels of the control and protection system (CPS).

83. The main total pipeline of the technological channels of a nuclear reactor, then the main total pipeline (GTS).

84. Graphite moderator.

85. A steam separator with steam exits 86 and an aqueous fraction 87. Pos. 86 - outlet pipe of the steam separator.

88. Circulation pumps.

89. Cooling water.

90. The main pipeline for supplying water (coolant) to the inputs of the technological channels of the reactor.

91. The direction of movement of the coolant in the technological channels.

92. High pressure turbines.

93. Low pressure turbines.

94. Electric generator.

149. Auxiliary water circuit.

The locations of the optical sensors of the proposed laser measurement system are indicated by the following numbers:

95. In the bypass of the main total pipeline, or directly in the main total pipeline 83.

96. In the technological channels 81 in the reactor core.

97. In the channel of the control and protection system (CPS 82).

98. At the outlet of the steam separator 85.

99. In the main pipeline for supplying coolant to the inputs of the technological channels 90, or on the bypass of this pipeline.

In FIG. 10 shows the layout of the triad of optical sensors (Fig. 5) in the bypass of the main total pipeline of technological channels. Numbers denote the following elements.

100. The outputs of the technological (fuel) channels of a nuclear reactor.

101. The main total pipeline.

102. Bypass of the main total pipeline.

103. The location of the triad of optical sensors similar to that shown in FIG. 5.

104. Steam separator.

105. Steam output to steam turbines.

106. The output of the aqueous fraction to the circulation pumps.

In FIG. 11 is a diagram of the upper part of the fuel assembly (FA) of the RBMK reactor with an optical sensor of a through type located in the upper part of the fuel assembly.

In FIG. 12 is a sectional view of FIG. 11 of the upper part of the fuel assembly with an optical sensor located in the upper part of the fuel assembly. A view is presented down from the plane of section AA. The numbers in FIG. 11 and FIG. 12, the following elements are indicated.

107. The beam expander (input).

108, 109 - optical reflective mirrors.

110. The beam expander (output).

111. Rim and spacing protrusions.

112. Structural elements of fuel assemblies.

113. The central pipe of the fuel assembly.

114. Output channels of fuel assemblies filled with moving coolant.

115. A beam of laser probe radiation crossing the output channels of a fuel assembly.

116. Fiber optic line.

119. A support rod located in the central pipe (key 113).

120. Fiber optic line.

The optical sensor contains the elements indicated by the positions 107-110.

151. A fuel assembly adapter is the upper part of a fuel assembly, for which a fuel assembly is mounted in the technological channel of the reactor.

In FIG. 13 is a sectional diagram of the upper part of a fuel assembly of the RBMK reactor with fuel elements (TVEL) placed. Numbers denote the following elements.

111. The rim and the spacers (corresponding to pos. 111 in Fig. 11 and Fig. 12).

117. Intermediate cell (structural elements of the fuel assembly ensuring the fixation of fuel elements).

118. Fuel elements (fuel elements), which are metal waterproof cylinders (sleeves) filled with nuclear fuel, are uranium oxide tablets.

119. Bearing rod.

113. The central pipe of the fuel assembly (corresponds to pos. 113 in Fig. 12)

150. Channels for the through passage of the coolant through the fuel assembly (filled with water).

In FIG. 14 is a diagram of the middle part of a fuel assembly with an optical sensor located in this part, similar to the optical sensor in FIG. 11 - FIG. 12. The numbers indicate the following elements.

121. The upper section of the fuel assemblies of the RBMK reactor.

122. The lower section of the fuel assembly.

118. The fuel elements corresponding to pos. 118 in FIG. 13.

The optical sensor (pos. 108, 107) is located in the intersection space in the plane AA. The optical sensor mounts are not shown.

The same as in FIG. 11 - FIG. 13 elements are marked with the same numbers.

In FIG. 15 shows a sectional view of the middle part of a fuel assembly with an optical sensor placed. A view is presented down from the plane of section AA. This circuit corresponds to the circuit of FIG. 14. In this diagram, fuel elements with a nuclear fuel pos. 118, design elements of fuel assemblies and optical sensor elements. The designations of the elements correspond to FIG. 11 - FIG. fourteen.

The presented diagrams do not show the elements for attaching optical sensors to the structural elements of a fuel assembly.

In FIG. 16 shows the location of the optical sensor in the channel of the control and protection system (CPS). Numbers denote the following elements.

124. The body of the channel CPS.

125. The drain valve.

123. Drain pipe.

126. The core of the CPS, consisting of the lower part 127 - the displacer, and the upper part 128 - the absorber.

129. The rod of the channel CPS (provides movement of the rods CPS).

130. The reactor core.

131. Optical reflector.

132. The beam expander.

133. Fiber optic line.

134 Channel emphasis CPS.

In FIG. 17 shows a location scheme of an optical sensor of a reflective type in the core of a VVER reactor. Numbers denote the following elements.

135. Fuel assembly (fuel assembly of the WWER reactor).

136. The beam expander.

137. Optical reflector.

138. Supporting rod.

139. Fairing.

140. Fiber optic line.

In FIG. 18 is a diagram of a second embodiment of a reflective type optical sensor in the core of a VVER reactor. Numbers denote the following elements.

141. Supporting bar.

142. The beam expander.

143. Optical reflector.

144. Reflective mirror.

145, 146 - fairings.

147. Fiber optic line.

148. The fuel assembly.

Presented in FIG. 17 and FIG. 18 optical sensors with their mounting elements and a supporting rod form a measuring channel located in the core of the WWER reactor.

In FIG. 19 shows a layout of an optical sensor of a reflective type outside the coolant pipe. The following elements are indicated by numbers (the elements corresponding to Fig. 1 are denoted by the same figures as in Fig. 1).

66. Heat transfer pipe.

20. The beam expander of the optical sensor.

21. The optical reflector of the optical sensor.

24. Fiber optic line.

153, 154 - Optical portholes built into the coolant pipe 66.

In FIG. Figure 20 shows a graph of the flow rate (1) and the true steam content in the technological channel of maximum power (2) and in the technological channel 50% of the power from maximum (3) depending on the dryness of the steam.

In FIG. 21 is a graph of dryness (1, 2) and humidity (3, 4) of steam in the process channel at maximum power (1, 3), at a power of 50% of maximum (2, 4) depending on the measured true steam content.

The principle of operation of the laser system for measuring the vapor content in the coolant of a nuclear reactor is as follows.

The proposed laser system continuously monitors the level of vapor content at the points of the coolant circuit in which the optical sensors are located. In the embodiment of FIG. 1 a block diagram of a laser measuring system shows three optical sensors located in the coolant pipe of a nuclear reactor: the first optical sensor, the elements of which are indicated by positions 14 and 15, the second optical sensor, indicated by the numbers 20 and 21, and the third optical sensor, whose elements are indicated by the positions 22 and 23. These optical sensors form a triad and are located inside the coolant pipe pos. 66, through which the water coolant flows from the outlet of the technological channels of a nuclear reactor. Optical sensors are located in close proximity to one another. In this case, the optical axes of the sensors are parallel to each other and can be in the same plane, as shown in FIG. 1, and may also be in different planes, as shown in FIG. 5. Using an optical sensor, the coolant is exposed to a beam of laser probe radiation, which is formed by means of the corresponding beam expander pos. 14, 20, and 22. When laser probe radiation passes through the coolant layer, the parameters of laser radiation (LI) change depending on the optical characteristics of the coolant in a given place of its movement through the process pipeline. In the presence of steam in the composition of the coolant, laser radiation scatters on steam bubbles or other places in the coolant in which its density is less than the density of homogeneous water in the absence of steam elements. The level of scattering of laser radiation is due to the level of steam in the steam-water mixture, which is a coolant at the outlet of the technological channel of a nuclear reactor. Using an optical sensor, the amount of scattered laser radiation is measured as it passes through the coolant layer, which provides a measure of the level of steam in the steam-water mixture at the corresponding point in the coolant in the nuclear reactor. Based on the information about the parameters of the scattered laser radiation coming from the three indicated optical sensors, an estimate of the level of vapor content in the coolant at the location of these optical sensors is formed in the information processing unit 71. The proposed laser system uses two types of optical sensors: the first optical reflective type sensor pos. 14, 15, the second reflective type sensor 20, 21 and the optical transmitted radiation sensor pos. 20, 21 (the third optical sensor is an optical sensor of a through type). These types of sensors differ somewhat in their characteristics and complement each other well. The construction of the optical sensor of the first type is shown in FIG. 2. The optical sensor contains a support frame pos. 72, on which a beam expander 14 and an optical reflector 15 are mounted. FIG. 4 is a side view of an optical sensor of the first type — a view along arrow “a” in FIG. 2. An optical sensor in working condition is placed directly in the coolant flow, which passes through the controlled volume of the sensor either along arrow “a” or perpendicular to the plane of the drawing. The beam expander 14 and the optical reflector 15 are located on the optical axis of the sensor 73. The fiber-optic line 13 provides the supply of probing laser radiation to the beam expander 14 and simultaneously removes the laser radiation transmitted through the controlled volume of the coolant and reflected from the optical reflector 15. The optical reflector is made on based on a multi-element matrix of corner reflectors. It is also possible to use a conventional reflective mirror made on the basis of a polished metal plate. In FIG. Figure 3 shows the construction of an optical sensor of the second type - a transmitted radiation sensor. This sensor contains a supporting frame 74, on which the beam expanders are mounted: an input beam expander 22 and an output beam expander 23. These beam expanders are located on the optical axis of the sensor pos. 75. Thus, the second pass-through optical sensor differs from the first-type optical sensor in that in the second-type sensor, the optical reflector 15 is replaced with a beam expander 23. In this case, the laser radiation is supplied through the fiber-optic line 25, and the radiation transmitted through the coolant in the controlled volume of the sensor, it is carried out through the fiber-optic line 28. The controlled volume in both sensors has the form of a cylinder, the axis of which coincides with the optical axis of the sensors, and the base of the cylinder azuet circumference beam expander output aperture pos. 14 and 22. Support frame pos. 72 and 74 has a small thickness "d" (Fig. 2) and does not affect the movement of the coolant through the pipeline. Beam expanders and an optical reflector also have limited dimensions and do not significantly affect the movement of the coolant. Optical sensors in working condition can be located in one plane in the coolant pipe 66, as shown in FIG. 1, and may also be located in more than one plane, as shown in FIG. 5. At the latter, the optical axes of the optical sensors are perpendicular to the direction of the axis of the coolant pipe 66. Here is a side view of the optical sensors located in the pipe 66 (view along the direction of the optical axes of the sensors). In FIG. 5, reference numerals 76 show the bushings providing the output of fiber optic lines from the coolant pipe.

Optical sensors operate individually sequentially over time. When working, for example, the first optical sensor pos. 14 and 15, the first optical shutter 19 corresponding to this sensor opens and one of the laser generators pos. 1 or 2. Other optical shutters pos. 31 and 32 are closed and measurements by optical sensors 20, 21 and 22, 23 are not performed at this point in time. Individual work is carried out in a similar way — measuring the level of probe laser radiation transmitted through a coolant — by other optical sensors when opening the corresponding optical shutters 31 or 32. The actual process of one measurement cycle with one optical sensor is a short time of the order of several microseconds. It should be noted the possibility of simultaneous operation of two or all three optical sensors, but at different wavelengths. For this, the second laser generator pos. 2 generates probing laser radiation at a different wavelength different from the wavelength of the first laser generator 1. It is possible to use a special laser generator pos. 2, generating two or more wavelengths. In this case, controlled optical filters 17, 33 and 36 carry out the allocation of the corresponding wavelengths of the probe laser radiation arriving after passing through the coolant to the inputs of the photodetector blocks pos. 16, 34 and 35.

The operation of the optical sensors is illustrated in FIG. 6 and FIG. 7.

In FIG. 6 shows a block diagram of the operation of the first optical sensor pos. 14 and 15, separated from the general block diagram of the laser system for measuring the vapor content in FIG. 1. In the block diagram of FIG. 6 only those elements of the general block diagram are shown which function at the time of operation of the first optical sensor pos. 14, 15. The numbering of the positions in FIG. 6 corresponds to FIG. 1. The operation of the first optical sensor is as follows. At the command of the control unit 70, the laser generator 1 generates a pulse of laser probe radiation, which through the first optical shutter 19 and the first optical switch 11 enters the optical input of the first fiber adapter 12 and then passes through the fiber optic line 13 to the beam expander 14. In this case by commands from the control unit, the first optical shutter is put into an open state for transmitted radiation, and the first optical switch 11 is put into a switching state for radiation passage in s the defense of the first fiber adapter 12. From the optical output of the beam expander 14, a laser pulse propagates along the optical axis 73 of the sensor through the coolant, is reflected in the opposite direction from the optical reflector 15, passes through the coolant a second time, and then again enters the beam expander 14 and into the fiber optic line 13. Then, from the output of the fiber adapter 12, the laser pulse passes through the first optical switch 11 and, after reflection from the translucent mirror 9, is fed to the optical input first controllable optical filter 17. Last is set to the transmission of laser radiation with a wavelength corresponding to an emission wavelength generated by the first laser oscillator 1. The controllable optical filter 17 performs the spectral filtering of the laser radiation and the suppression of extraneous interference. From the output of the controlled optical filter 17, the filtered laser pulse arrives at the input of the first photodetector unit 16, which receives, registers, and digitizes the laser pulse. Next, the laser pulse in digital form comes from the output of the photodetector unit 16 to the information processing unit 71. In the latter, the received information is processed and the vapor content in the coolant is determined from the measured parameters of the laser pulse transmitted through the coolant within the location of the optical sensor 14, 15 The vapor content level is estimated by the magnitude of the decrease in the amplitude of the laser pulse transmitted through the coolant. The reference value for this assessment is the intensity of the laser pulse generated by the first laser generator 1. This value is measured by the first laser radiation meter 3, the input of which receives a part of the laser radiation pulse from the output of the laser generator 1 by means of a translucent mirror 5. Information about the parameters of the generated laser radiation comes from the outputs of the laser radiation meters 3 and 4 to the information processing unit 71. With an increase in the vapor content in the coolant, through which passes the pulse of the probe laser radiation, there is a decrease in the intensity of laser radiation, which is recorded in the information processing unit 71. On this, one cycle of measuring the vapor content in the coolant in the corresponding optical sensor is completed. In one measurement cycle, one laser pulse corresponds to obtaining the value of one estimate (reference) of the level of vapor content in the coolant at a specific location of the optical sensor and at the time of passage of the probe laser radiation through the coolant. The operation of the second optical sensor pos. 20 and 21. In this case, the optical shutter 31 is brought into the open state, and the optical shutters 19 and 32 are in the closed state.

In FIG. 7 shows a block diagram of the operation of the third optical sensor pos. 22 and 23. In this diagram, only elements of the general block diagram of FIG. 1 involved in the operation of this optical sensor. The numbering of the positions of FIG. 7 corresponds to FIG. 1. As noted, the third optical sensor operates according to the registration scheme of laser radiation passing through the coolant. In this case, the third optical shutter 32 is in the open state, and the fourth optical switch 30 is mounted on the direct passage of the probing laser radiation to the input of the third fiber adapter 27. When the third optical sensor is in the operating mode of generating the probing laser radiation, the first or second laser generators. In this case, the laser radiation from the output of the beam expander 22 passes along the optical axis 75 and enters the optical input of the beam expander 23, which is similar to the beam expander 22. Next, the laser radiation from the output of the beam expander 23 enters the fiber optic line 28 and then to the fiber adapter 61 , from the output of which the laser radiation enters the input of the second optical switch 18. From the output of the last laser radiation enters the input of the third controlled optical filter 36. From the output of the controlled optical filter 36, the laser radiation enters the optical input of the third photodetector unit 35, in which the laser radiation is recorded and digitized. From the output of the photodetector unit 35, the information enters the information processing unit 71. Thus, information on the parameters of the probe laser radiation received from three optical sensors and, accordingly, information on the parameters of the vapor content of the coolant at the locations of these sensors are accumulated in the information processing unit 71.

The presence in the proposed laser measuring system of three optical sensors of two different types allows implementing various algorithms for measuring the parameters of probe laser radiation transmitted through the coolant of a nuclear reactor, which provides higher accuracy in measuring the vapor content and increasing the reliability and reliability of the information received. One of these measurement algorithms is carried out using the third optical sensor pos.22, 23, and consists in the use of continuous laser radiation generated by the second laser generator 2. In this case, the first laser generator is in the off state. When the third optical sensor is operating, the third optical shutter 32 is in the open state. The fourth optical switch 30 is open in the direction of direct transmission of laser radiation from the output of the optical shutter 32 to the input of the fiber adapter 27. Using continuous laser radiation allows not only to obtain an estimate of the vapor content at a fixed point in time , but also to obtain information on the dynamics of changes in the level of steam content over time. To measure the spectral temporal characteristics of the change in vapor content, the proposed laser system comprises a fast Fourier transform (FFT) unit 67 of FIG. 1. The input of the latter continuously receives a digital signal from the output of the third photodetector block 35. Block 67 is a specialized processor that implements an algorithm for the fast Fourier transform of the incoming digitized signal from the output of the third photodetector block 35 in real time. The generated one-dimensional Fourier spectrum is transmitted digitally from the output of the FFT 67 to the information processing unit 71. The latter accumulates information about the level of laser radiation transmitted through the coolant at the location of the third optical sensor 22, 23, as well as about the dynamics of the change in laser radiation and its spectral temporal characteristics. This allows one to obtain additional important information on the nature of fluctuations in time of the density of the coolant and the mode of vaporization in the coolant of a nuclear reactor. So, for example, at a high level of vapor content, the level of fluctuations of the laser radiation transmitted through the coolant increases, and the spectrum of fluctuations shifts to the high-frequency region and contains higher frequencies. Thus, the triad of optical sensors measures the vapor content in the coolant at three adjacent points of the coolant, and the third optical sensor additionally provides information on temporal fluctuations and spectral temporal characteristics of the laser radiation transmitted through the coolant. Optical sensors can work simultaneously or sequentially in time. The operation of the optical sensors is controlled by the control unit 70 by turning on or off the first or second laser generators and opening and closing the corresponding optical shutters pos. 19, 31 and 32. At the same time, the first and second optical sensors can operate at the same wavelength. In this case, the third optical sensor is turned off by closing the optical shutter 32. Simultaneous with the two indicated, the operation of the third optical sensor is possible using a different working wavelength in the second laser generator 2. The third optical sensor at a different wavelength is operated using a controlled optical filter 36 which, due to the narrow optical spectral bandwidth, eliminates the influence of pulsed laser radiation from the first two sensors on the operation of the third of the optical sensor. For this, it is possible to use a second laser generator with laser wavelength tuning. The summation of the radiation of two laser generators pos. 1 and 2 in one direction using a translucent mirror 7 is implemented to realize the possibility of using in each sensor different types of radiation and different wavelengths generated by each laser generator. This is especially important when optical sensors are located at different points in the coolant circuit of a nuclear reactor. When the optical sensors are co-located, an operation mode is possible in which the optical sensors record not only a decrease in the level of transmitted laser radiation (LI), but also a level of scattered laser radiation, which makes it possible to increase the accuracy of measuring the vapor content in the coolant. This mode of operation of optical sensors is as follows. When working with laser probe radiation of only the first optical sensor 14, 15 in the open state, only the first optical shutter 19 is installed, and the remaining optical shutters 31 and 32 are in the closed state. When the probe laser radiation (pulse) passes through the coolant from the beam expander 14, the laser radiation scatters both forward in the direction of the laser beam propagation and backward scattering in the lateral direction. In this case, the LI, scattered backward, enters the input of the beam expander 20 of the second optical sensor (pos. 20, 21) and then along the fiber-optic line 24 and through the third optical switch 29, which is open for direct passage, the LI is transmitted through a translucent mirror 64 to the optical input of the second controlled optical filter 33. From the output of the last LI is fed to the optical input of the second photodetector unit 34 and then, in digital form, information about the parameters of the scattered LI is fed to the information processing unit 71. Scattered across To the propagation of the initial probe pulse, the LI (forward scattering) enters the optical input of the fourth beam expander 23 in the third optical sensor. Further, this LI in a similar way through the fiber optic line 28 and through the second optical switch 18 is fed to the input of a controlled optical filter 36 and to the input of the third photodetector block 35, and then digitally to the information processing unit 71. Similarly, when the probe pulse is reflected from of the optical reflector 15 and its propagation in the opposite direction along the optical axis, the beam expanders 20 and 23 register laterally scattered laser radiation due to the presence of vapor bubbles in the heat Ithel in the zone of the probe LEE forward and backward along the optical axis 73 (FIG. 6) of the first optical sensor. Thus, in the information processing unit 71, information is generated on the magnitude of the decrease in the level of the probe laser radiation transmitted through the coolant, as well as information on the magnitude of the scattered laser radiation due to this probe pulse. The levels of these two types of laser radiation are due to the same factor - the presence of vapor bubbles in the coolant. Therefore, obtaining this information allows you to more accurately determine the level of vapor content in the coolant of a nuclear reactor. Similarly, when working with probing laser radiation of only one second optical sensor 20, 21, it is possible to register the levels of scattered laser radiation in the adjacent first and third optical sensors. Thus, the measurement of the parameters of the probe laser radiation using three adjacent optical sensors (triads) containing sensors of two different types, allows to increase the amount of information received (information content) and to provide higher accuracy in determining the vapor content in the coolant of a nuclear reactor. The presence of three optical sensors makes it possible to implement various algorithms for measuring the vapor content and to increase the accuracy of measurements and the reliability of the obtained estimates of the vapor content in the coolant of a nuclear reactor.

To ensure high reliability and accuracy of measuring the parameters of the coolant, an analog model of a nuclear reactor 40 has been introduced into the proposed laser measurement system. This analog model provides the creation of a reference measurement base for more accurate measurements of the parameters of probing laser radiation and interpretation of the measurement results. An analog model of a nuclear reactor 40 performs full-scale analog simulation of the optical parameters of the coolant in a nuclear power reactor. The analog model is a container pos. 152 (Fig. 1) (reservoir), filled with water, in which three optical sensors pos. 41-46, similar to the first three optical sensors, the operation of which is discussed above. Inside the container 152 are also elements that ensure the creation in the aqueous medium filling the container of physical conditions of vaporization similar to the conditions in the coolant of the measured nuclear reactor with respect to the optical properties of the coolant. The creation of such an analogue model with respect to the optical properties of the coolant is possible without using the full coincidence of all physical parameters of the coolant in a nuclear reactor and in the analogue model with respect to pressure and temperature of the coolant. This is due to the phenomenon of incompressibility of the liquid (water) and the dependence of the boiling point of water on pressure. Therefore, the same level of vaporization intensity can be provided at different levels of temperature and water pressure. In the used analog model, the pressure level corresponds to normal atmospheric pressure, and the vaporization rate is ensured by the necessary intensity of heating the water in the container 152, which is carried out by the heating element 47. The intensity level of the heating of the latter is set by the control unit 70 to which this heating element is connected. As a result of constant heating in the container 152, the boiling mode of water with a certain amount of vaporization is established. The resulting vapor bubbles rise up and fall into the range of the optical sensors pos. 41, 42, 43, 44 and 45, 46. Two ultrasonic pathogens 48 and 49 are located inside the container in the zone of action of the heating element 47. The latter excite ultrasonic waves of sufficiently high intensity in the aqueous medium. This provides, within certain limits, control of the process of vaporization. At the same time, ultrasonic (ultrasound) waves break the largest vapor bubbles, contribute to an increase in vaporization when the ultrasound wave falls on the surface of the heating element and reflects from it due to the rapid removal of already formed steam. Pulse-periodic excitation of ultrasonic waves of a certain amplitude and pulse repetition rate is used. Ultrasonic exciters 48, 49 are made on the basis of piezoelectric elements connected to a special electric oscillation control generator 50, the operation mode of which is determined by the control unit 70. For a more complete mixing of the contents of the container 152 and a more uniform steam-water mixture, a fan 55 is provided, the operation mode of which is controlled control unit 70. To control the temperature inside the container, a temperature sensor 56 is used with a digital representation of the measurement results, connected information to the information processing unit 71. At a certain high level of excitation of ultrasonic waves, the formation of so-called cavitation vapor bubbles is possible, which, depending on the frequency of excitation and intensity of ultrasonic waves, can have different sizes and density (number of bubbles) per unit volume of water. Thus, in the analog model, two methods (types) of creating vapor bubbles are used: using intensive heating of the liquid and using ultrasonic excitation of cavitation bubbles. To measure the level of vapor content in the container 152 of the analog model 40, a television camera 52 and an optical illuminator 51 — a source of illuminated optical radiation — are used. The illuminator 51 and the television camera 52 are mounted on the same optical axis parallel to the optical axes of the optical sensors pos. 41-46. The light beam formed by the illuminator 51 passes through the aqueous medium in the container 152. For the passage of the light beam in the container 152 optical windows 53, 54 are provided. The television camera 52 is equipped with a lens that builds on the photosensitive area of the receiving matrix of the camera the image of the entire path of the light beam along optical axis. In this case, the camera registers images of all vapor bubbles located at this moment in time within the limits of the light beam. The image of this scene in digital form is sent to the information processing unit 71. In the latter, according to a special program, each image frame received from the television camera 52 is individually processed. At the same time, the images of individual steam bubbles are contoured and their number is counted in one current television frame. Next, the average value N1 of the number of steam bubbles is calculated by averaging the number of bubbles in several frames over a fixed period of time. The obtained value is taken as an estimate of the vapor content in the analog model of nuclear reactor 40. Next, in the test mode of the laser measuring system, the vapor content in the analog model 40 is measured using the fourth, fifth and sixth optical sensors (keys 41-46) located inside the container 152 of FIG. 1. To carry out this measurement process, the optical switches 11, 29, 30, as well as the optical switch 18 are switched in the direction of transmission of optical (laser) radiation to the optical inputs of the fiber adapters 37, 38, 39, as well as in the direction of the fiber adapter 60 in the optical switch 18. The measurement is carried out using the same photodetector units 16, 34, 35 in the same manner as described above for the measurement process using the first three optical sensors. In the information processing unit 71, information is generated about the parameters of the laser radiation levels recorded by the optical sensors 41-46 in the analog model 40 and the corresponding vapor content estimation value N1 measured using the television camera 52 in the analog model 40. Further, in the information processing block 71 compare the parameters of the LI measured by optical sensors in the analog model 40 and the parameters of laser radiation measured by the first three optical sensors in the coolant of a nuclear reactor. Based on this comparison, a judgment is made about the level of vapor content in the coolant of a nuclear reactor at the location of the first three optical sensors. With a slight difference in the LI parameters recorded by the sensors in the coolant and the sensors in the analogue model 40 (less than 15%), a decision is made to take a value equal to N1 of the measured level of vapor content in the analogue model 40 for the level of steam content in the coolant. With a larger difference the measured parameters of the laser radiation, the vaporization level is changed in the analog model 40 by changing the heating level by the heating element 47 and by changing the level of excitation of ultrasonic waves using Of pathogens 48,49 and carry out repeated measurements of the vapor content in the analog model 40. At this point, the cycle of measuring the vapor content in the coolant of the nuclear reactor and in the analog model of the nuclear reactor 40 is completed. In the future, the cycles of measuring the vapor content in the coolant and in the analog model are periodically and continuously repeated during the operation of a nuclear reactor. It should be noted that the process of modeling the optical properties of the coolant in the analogue model 40 is carried out at normal atmospheric pressure in the container 152. At the same time, fiber-optic lines (pos. 57, 58, 59 and 62) connected to the beam expanders (pos. 41- 46) located inside the container 152, pass through the upper open hatches of the container. In this case, there is no need to use bushings (key 76 in FIG. 5) to output fiber optic lines from container 152.

An important issue that arises when using the proposed laser measuring system is the issue of installing optical sensors at various points of the nuclear reactor and the coolant circuit of the nuclear reactor. The laser measuring system is designed for use in two types of aqueous nuclear power reactors: RBMK and VVER. RBMK is a reactor with a boiling coolant and here the application of the proposed laser system for measuring steam content is the most important. The main use of the laser system for measuring the steam content in the RBMK reactor is associated with measuring the parameters of the coolant at the outlet of the technological (fuel) channels. It is advisable to establish a triad of optical sensors (Fig. 5) - the joint location of the optical sensors at a small distance from each other. It is advisable to install one optical sensor at separate points of the reactor core and reactor coolant loop, the readings of which together reflect the parameters of the operating mode of the nuclear reactor as a whole.

In FIG. 9 is a diagram of a power unit of a nuclear power plant with a RBMK type nuclear reactor. Presented in FIG. 9 and the following figures, schemes are developed using materials from monographs [15], [16], [17], [21]. (terminology and names of individual elements correspond to the indicated monographs).

In FIG. 9, the special positions mark the elements and points of the RBMK circuit, in which optical sensors of the proposed laser measuring system can be installed (pos. 95-99). Optical sensors can be installed in the technological channels pos. 96 and in the channels of CPS 97, as well as in the main total pipeline 95 at the outlet of the technological channels of a nuclear reactor. The optical sensor pos. 98 is installed on the outlet pipe 86 of the steam separator 85 to control the quality of the steam coming from the steam separator output to the steam turbines. It is advisable to install the optical sensor in the main pipeline 90 for supplying water to the inputs of the technological channels pos. 99.

In FIG. 10 shows the layout of the triad of optical sensors in the bypass pipeline of the main total pipeline, in which the outputs of all technological channels of the RBMK reactor coolant circuit are combined. Here, the numbers indicate the following elements. Output pipelines of technological channels pos. 100 are combined in the main total pipeline pos. 101. The bypass of the main total pipeline is indicated by pos. 102. The location of the triad of optical sensors is indicated by pos. 103. Next, the output of the main total pipeline 101 is connected to a steam separator 104, in which the steam is separated from the water. The steam component is sent via line 105 to the steam turbine. The water component through pipeline 106 is sent to the circulation pumps and again enters the working area of the nuclear reactor at the entrances of the technological channels. The arrangement of the triad of optical sensors in the coolant pipe is shown in FIG. 5. The location of the optical sensors in the main total pipeline allows you to quickly measure the average vapor content in the coolant at the outlet of the nuclear reactor. In accordance with the regulations of the nuclear reactor, this value should be 14.5%. An important parameter is also the vapor content in the coolant at the outlet of one technological channel. This value is 19.7% according to the regulations of a nuclear reactor [17]. The vapor content in the coolant at the outlet of the process channel can be measured using an optical sensor installed in the outlet pipe of one process channel, pos. 100 in FIG. 10, or in the bypass of this pipeline. It is also possible to install optical sensors directly on the fuel assembly (FA) of a nuclear reactor.

As you know, the RBMK technological channel is a vertical metal pipe made of a special alloy, in which one fuel assembly is placed. Therefore, the placement of optical sensors on a fuel assembly is actually the installation of sensors in the technological channel of the RBMK nuclear reactor. Variants of the arrangement of optical sensors on the RBMK reactor fuel assembly are presented in FIG. 11-15. In FIG. 11 is a diagram of the upper part of a fuel assembly with an optical sensor of a through type located at this part (keys 107, 108), and fiber optic lines 116, 120 are also shown. FIG. 12 is a sectional view of the upper part of a fuel assembly corresponding to FIG. 11. A view from the plane of section AA below is presented. Here, against the background of the cross section of the upper part of the fuel assembly, the location of the through-type optical sensor is shown. This optical sensor comprises a first beam expander 107, two optical reflective mirrors 108, 109 and a second beam expander 110. The first beam expander 107 is an input expander emitting a probe laser beam. The second beam expander 110 is an output expander that receives a beam of laser radiation that has passed through the coolant and directs it into the fiber optic line 116. The elements of the optical sensor are mounted on structural elements 112 of the fuel assembly and are located around the circumference. At the same time, the elements ensuring the fastening of the optical sensor on the structural elements of the fuel assemblies are not shown. In FIG. 12 does not show fuel elements (TVEL) in order to simplify the drawing. As a result of the presented embodiment of the arrangement of the optical sensor, the probe laser beam 115 passes through three output streams of coolant propagation (pos. 114) at the output of its passage through the fuel assembly in the upper part of the latter. This ensures the measurement of the vapor content in the coolant directly at the outlet of the fuel assembly. In FIG. 13 is a sectional diagram of the upper part of a fuel assembly with fuel elements (TVEL) located in this part, indicated by pos. 118, similar to the designation in FIG. 11. Here schematically shows the various structural elements of the fuel assemblies that provide for the fastening of the fuel rods, such as the central tube 113 and the intermediate grid 117. As a result of this arrangement and fastening of the fuel rods in the fuel assemblies, through channels of pos. 150 for the passage of the coolant through the entire design of the fuel assembly. The main heat sink of thermal energy from fuel elements 118 is carried out through these channels.

As you know, in a RBMK reactor, a fuel assembly consists of two parts-sections fixed to a single supporting central rod 119. There is a spatial gap between these sections in which it is advisable to install an optical sensor. Such an arrangement of the optical sensor in the intersectional space of a fuel assembly is shown in FIG. 14, which shows a diagram of the middle part of a fuel assembly with an optical sensor of a through type. In the following FIG. 15 shows a section of the middle part of the fuel assembly and a view down from the plane of section AA. Here, the fuel elements pos.118 located at the bottom of the fuel assembly are also shown. The numbering of the same elements is uniform in FIG. 11 - FIG. 15. The complete designation of all elements in FIG. 11 - FIG. 15 is presented above together with the list of illustrations of FIG. 1 - FIG. 18. The location of the optical sensors in the middle of the fuel assembly, as shown in FIG. 14-15 allows you to measure the vapor content in the center of the fuel assembly, which provides valuable information on the parameters of the coolant and vapor content in the center of the active zone of a nuclear reactor. The fastening elements of the optical sensors to the fuel assemblies are not shown. It should be noted that at the indicated points of the fuel assemblies in FIG. 11-15, reflective-type optical sensors discussed above may also be located. In this case, instead of reflective mirrors pos. 108, 109 in FIGS. 11-15, optical reflectors are installed, similar to the reflectors of pos. 15 and 21 in FIG. 1, made on the basis of angular reflector arrays. Beam expanders pos. 107, 110 in this case provide the emission of probe laser pulses and the reception of laser pulses reflected from the corresponding optical reflectors.

It is advisable to install an optical sensor in the RBMK type reactor to monitor the conditions of the water filling the channels in the control and protection system (CPS). The location of the optical sensor in the CPS channel is shown in FIG. 16. Here are shown the body of the CPS channel pos. 124, equipped with a drain valve 123. In the upper part of the CPS channel there is a CPS rod 126, shown in the first operating state in the fully extended position. The CPS core consists of two parts: a displacer 127 containing graphite, and a neutron absorber based on boron compounds 128. To ensure cooling, the CPS channel is filled with water. In the second operating state, the CPS rod is pushed into the reactor core by the length of the displacer 126. In the shutdown mode of the reactor, the CPS rod is pushed to the lower mark - to the stop 134. At this lower position of the CPS rod, the absorbing part 128 is located in the reactor core. Optical beam expander 132 the sensor is located in the lower part of the CPS channel below the 134 mark, to which the CPS rod lowers. At the bottom of the CPS rod is an optical reflector 131 of the optical sensor. This allows you to monitor the state of the entire column of water (coolant) filling the CPS channel in the first working condition, and to timely receive information about the occurrence of thermal overload of this reactor channel in the presence of excessively high vapor content. As you know, at the Chernobyl nuclear power plant there were no sensors for the vapor content of the coolant. As a result, during thermal overload of the reactor, the level of vapor content in the coolant reached an unacceptably high value, at which difficulties arose in the CPS channel to lower the CPS rod to shut off the reactor due to the high vapor pressure.

Thus, as shown above, the optical sensors of the laser measuring system can be installed in various technological zones of the RBMK nuclear power reactor and provide continuous operational monitoring of the operating mode of this reactor in real time. Optical sensors can be installed at any location and movement of the coolant, including the reactor core, if there is a small space for their location. So, for example, optical sensors can be installed in the through channels of the fuel assembly pos. 150 FIG. 15. It should be noted the feasibility of installing an optical sensor pos. 98 at the outlet of the steam separator 95 for controlling the quality of the steam entering the steam turbines of FIG. 9.

The laser system for measuring the vapor content in the coolant is proposed for use as part of a VVER-type water reactor. VVER-type reactors are water-based vessel reactors in which fuel assemblies are located in a single high-strength housing and are cooled by a common stream of water coolant.

In the VVER reactor, fuel assemblies (FAs) are located in the core along with several standard measuring channels. Moreover, in the intervals between the fuel assemblies, it is possible to install additional measuring channels, including optical sensors. In FIG. 17 shows such an additional measuring channel in the VVER core, located close to the fuel assembly, indicated by pos. 135. This measuring channel includes an optical sensor of a reflective type based on a beam expander 136 and an optical reflector 137 mounted on a support rod pos. 138. The optical reflector 137 is equipped with a fairing pos. 139. The support rod 138 is mounted so that the probe laser beam passes in the forward and reverse directions directly near the surface of the fuel assembly 135. The optical sensor in FIG. 17 controls the entire coolant zone along the surface of the fuel assembly 135. The fiber-optic line 140 is removed from the reactor core in its upper part through the main connector of the reactor. The supporting rod, as well as the fuel assemblies, are installed and fixed in the lower part of the reactor core. The arrows indicate the direction of movement of the coolant in the VVER core. The advantage of this arrangement of the optical sensor near the surface of the fuel assembly is the ability to control vaporization near the surface of the fuel assembly, which is especially important to prevent the destruction of the surface of the fuel assembly caused by the presence of a surface vapor film. Optical sensor pos. 136, 137 is equivalent to the optical sensor pos. 20, 21 in FIG. 1. In FIG. 18 shows an embodiment of an optical sensor capable of measuring the parameters of the coolant with perpendicular directions of motion of the coolant and the probe laser beam. On the support bar pos. 141, a beam expander 142, an optical reflector 143, and an additional reflective mirror 144 are secured here, allowing the optical axis to rotate 90 degrees. In this case, a probing laser beam passing in the forward and reverse directions passes through a wider part of the coolant flow propagating from below. The optical sensor is equipped with fairings pos. 145 and 146. Fiber optic line 147 is removed from the reactor core through its upper part. This optical sensor is installed in the reactor core at a certain fixed distance from the fuel assembly pos. 148 and at any height from the base of the reactor. Thus, optical sensors can be installed at various points in the VVER core, including directly near the fuel assembly working surface and provide continuous real-time monitoring of the state of the coolant vapor content. Optical sensors can also be installed at any point on the primary circuit of the WWER coolant to monitor both the vapor content and the concentration of boric acid, which is part of the coolant in water reactors of the WWER type. It should be noted that the location of the optical sensors directly in the coolant flow is a simpler technical embodiment of the laser measuring system than the use of a special measuring cuvette with optical windows, windows similar to those used in the prototype [11]. However, in some cases, it becomes necessary to install optical sensors outside the coolant pipe, for example, in various auxiliary piping lines. Such an option for installing an optical sensor outside the coolant pipe is shown in FIG. 19. In this embodiment, for monitoring the parameters of the coolant using an optical sensor, the coolant pipe 66 is equipped with optical windows pos. 153 and 154. In this embodiment, sensors of both the reflective type and the passage type can be used, as well as the possible arrangement of several optical sensors similar to those shown in FIG. 1 and FIG. 5.

The following is an analysis of the method for determining the vapor content based on the transmission of the coolant by probing laser radiation. When a steam-water mixture is illuminated by a probe laser pulse, the photodetector (photodetector unit) detects a decrease in the LI pulse intensity due to scattering on the vapor bubbles present in the coolant.

Let us estimate the thickness of the layer of the steam-water mixture, which can be illuminated by a laser beam. For this assessment, it is sufficient to consider a steam-water mixture with vapor bubbles of the same size, the so-called monodisperse mixture. For this, we present a quantity called dry steam [16] and denoted as x in the form

where ρ _s is the density of dry steam on the saturation line (kg / m ³ ), ρ _w is the density of water on the saturation line (kg / m ³ ), V _b is the volume of the vapor bubble (m ³ ), C _b is the concentration of bubbles (m ^-3 ).

From the presented expression for dry steam, we can express the product V _b C _b :

where β (x) is the volumetric steam content [17, p. 69], or as it is also called expendable steam content [18, p. 89].

As is known, in the case of a monodisperse medium, the optical thickness of the medium τ is defined as [19, P. 25, 26]

- толщина слоя пароводяной смеси. Данная величина равна удвоенному расстоянию между элементами поз. 14 и 15 в первом оптическом датчике на фиг. 1 и соответствует расстоянию между элементами поз. 22 и 23 в третьем оптическом датчике на фиг. 1.where D _b is the diameter of the vapor bubbles, Q is the efficiency factor of attenuation of the probe laser radiation, [19, C. 21],

- the thickness of the layer of steam-water mixture. This value is equal to twice the distance between the elements of pos. 14 and 15 in the first optical sensor of FIG. 1 and corresponds to the distance between the elements of pos. 22 and 23 in the third optical sensor of FIG. one.

The attenuation efficiency factor depends on the diffraction parameter α = πD _b / λ, where λ is the wavelength of the probe laser radiation. For α> 30, the attenuation efficiency factor is almost constant: Q = const = 2 [19, P. 24]. When the wavelength of laser radiation λ = 0.5 × 10 ^-6 m, the efficiency factor reaches its asymptotic value of 2, with a size of scattering particles of ~ 5 μm. Depending on the vapor content, steam bubbles of various sizes with diameters from a few micrometers to several millimeters move in a steam-water stream [18, p. 83]. Therefore, when scattering from vapor bubbles, Q = 2 should be set. Substituting this value into formula (3), we obtain

If a laser pulse with energy E _{0 is} incident on the layer of the steam-water mixture, then at the output of the layer, the pulse energy will become equal

This energy is recorded by a photodetector. The photodetector is part of the photodetector blocks pos. 16, 34 and 35 in FIG. one.

From relation (5) follows the relation for the number of photons at the input and output of the steam-water layer

- число фотонов на входе, а

- число фотонов на выходе пароводяного слоя,

- энергия кванта лазерного излучения. Из (6) следует, чтоWhere

is the number of photons at the input, and

- the number of photons at the output of the steam-water layer,

- energy of a quantum of laser radiation. It follows from (6) that

From (7) it is seen that the more sensitive the photodetector, the thicker the layer of the steam-water mixture can be illuminated. Modern photodetectors are capable of detecting individual photons. Putting the signal-to-noise ratio equal to 25, and the energy of the laser pulses E ₀ = 100 mJ, we obtain at a wavelength of laser radiation λ = 0.5 × 10 ^-6 m

In FIG. Figure 20 shows the dependence β (x) calculated for the steam-water mixture of the RBMK reactor. For its calculation, we used the values of the density of water and steam on the saturation line given in the tables [20, p. 102] and taken at an average pressure value along the length of the technological channel (TC). As it is known [21, p. 12], at the inlet of the HK and at the exit of the HK, the water temperature is 270 and 284.5 ° C, respectively, the pressure is 79.6 and 75.3 kg / cm ² . Because in the tables [20, p. 102], the pressure is expressed in bars, and 1 kg / cm ² = 0.980665 bar, then recalculating the pressure in bars, we get 78.06 and 73.84 bar at the input of the TC and at the output of the TC. The average pressure is 75.95 bar. At this pressure, the density of water on the saturation line ρ _w = 729.7 kg / m ³ and the density of dry steam ρ _s = 40.09 kg / m ³ .

From the figure in FIG. 20 we see that for all values of x β≤1. Therefore, the thickness of the water-vapor layer, as follows from formula (8), is not less than 12D _b . In experiments simulating the process of vaporization in a technological channel using an air-water mixture, the diameter of air bubbles ranged from 2 to 15 mm [18, p. 87]. In the steam-water flow, as noted above, depending on the vapor content, there are vapor bubbles of different sizes with diameters from a few micrometers to several millimeters.

It should be noted that, due to the movement of water, the true volumetric vapor content, usually denoted by the letter ϕ, differs from β due to the ablation of bubbles by an upward flow of water [18, p. 83]. To determine ϕ, there are many theoretical dependences for determining the true vapor content ϕ in an ascending steam-water adiabatic flow [18, P. 89; 7; 8]. To calculate the true steam content in the fuel cell of the RBMK reactor, the formula is used [18, P. 91; 17, p. 69]

where K is the phase slip coefficient:

d _g = 4S / P and S is the hydraulic diameter of the section and its area for the passage of the coolant, P is the wetted perimeter of the section, g = 9.81 m / s ² is the acceleration of gravity, w ₀ = G / (ρ _w S) - the velocity of the circulating coolant, G is the mass flow rate of the coolant, P is the pressure of the steam-water mixture, P _cr = 225 kg / cm ² = 220.65 bar.

As is known [18, p. 15], the parameters of the technological channel (TC) are as follows: inner diameter of the TC d _TC = 80 mm; the diameter of the fuel rod d _{fuel rod} = 13.6 mm; the diameter of the central pipe d _CT = 14.5 mm; the maximum mass flow rate of the coolant G = 7.764 kg / s [17, p. 50]. Using the above parameters, we find:

P = π (d _TK + 18d _{fuel rod} + d _CT ) = 1.06 × 10 ³ mm;

d _g = 8.44 mm; w ₀ = 4.74 m / s.

The true vapor content ϕ calculated with these parameters is shown in FIG. 20: curve 2 in the technological channel of maximum power, curve 3 in the channel 50% of the maximum power.

From FIG. 20 shows that the true steam content can significantly differ from the consumption. In this case, formula (8) should be written as

не менее 60 мм, что вполне достаточно для просвечивания ТК.Because ϕ≤1, then setting D _b ~ 5 mm, we obtain

not less than 60 mm, which is quite enough for translucent TC.

Further, on the basis of the foregoing, it is possible to solve the problem of measuring the dryness of steam, and therefore its moisture, denoted as y = 1, by attenuating the intensity or energy of the pulses of the probe laser radiation passing through the steam-water mixture (coolant). Using formulas (5) and (4), in which ϕ will now appear instead of β, we obtain

where can we find the dryness of steam by constructing the function inverse to (12):

.In FIG. 21, this function is shown as an example for the case of power equal to 50% of the maximum power channel (curve 1). In addition, for the same case, the dependence of steam humidity y = 1 on the true steam content is shown

.

A function that describes the dryness (humidity) of steam in a steam-water mixture of a nuclear reactor depending on the measured true value of the steam content can be obtained analytically, which is important for processing the measurement results using a computer. For this, we note that formula (9) can be represented in the form [18, P. 89]

Introducing in the formula (10) to simplify the calculations, the notation

представим K в виде

represent K in the form

and substitute in (14). As a result, we obtain with respect to β an algebraic equation of the third degree of the form

As is known [24, p. 43], algebraic equations of the third degree are solvable in radicals. Using now formula (2), the dryness of steam can be expressed through β in the form

and substituting here the solution for β, we obtain the analytical dependence of dryness or humidity y = 1 pair on the measured value ϕ.

In the case of a polydisperse medium (12) will have the form

- средний объемно-поверхностный диаметр пузырька (диаметр Соттера) [19, С. 16], ƒ(D_b) - дифференциальная функция счетного распределения пузырьков пара по размерам, которая определена таким образом, чтоWhere

is the average volume-surface diameter of the bubble (Sotter diameter) [19, C. 16], ƒ (D _b ) is the differential function of the countable size distribution of vapor bubbles, which is defined in such a way that

- вероятность того, что диаметр пузырьков лежит в интервале

,

[19, С. 13].Where

- the probability that the diameter of the bubbles lies in the range

,

[19, p. 13].

Thus, the humidity of the steam-water mixture anywhere in the reactor where the optical sensors are located can be determined on the basis of the presented formulas and graphs of the measured attenuation of the energy of the laser radiation E detected by the photodetector unit.

To process the obtained measurement results using a computer, the solution of the algebraic equation of the third degree, compiled for the corresponding power of the technological channel and the measured attenuation of the laser radiation energy,

written in the form of radicals and substituted in the expression

as a result, the computer gives the value of humidity in the steam-water mixture.

Thus, in the information processing unit pos. 71 in FIG. 1, the following algorithm for processing information from photodetector units 16, 34, and 35 is implemented. For each of the optical sensors, information is processed individually. From the corresponding photodetector block, block 71 receives information about the energy E of the LI pulse passing through the coolant layer. At the same time, information on the initial pulse energy level of the probe laser radiation E _{0 is} received from the corresponding laser radiation meter (pos. 3 or 4). Further, based on this information, according to the above formulas and parameters of the operating mode of a nuclear reactor (pressure, temperature, etc.), the following parameters of the vapor content of the coolant are determined:

β - volumetric steam content

ϕ is the true volumetric vapor content.

x - dry steam.

y = 1 - steam humidity.

It should be noted that the main measured parameter of the coolant of a nuclear reactor here is the last parameter y — the so-called steam humidity, which is the mass fraction of water droplets per unit mass of the coolant. The value of γ is the main controlled parameter of the vapor content and is (according to the regulation) at the output of the core of a nuclear reactor ~ 14%. These measured parameters of the vapor content from the information processing unit 71 go to the central control panel of the nuclear reactor. Similarly, in the information processing unit, the vapor content in the container of the analog model of the nuclear reactor 40 of FIG. 1. In this case, the parameters of temperature, pressure and speed of movement of the steam-water mixture, specified by the fan and the ultrasonic exciter, are taken into account. The pressure value can correspond to atmospheric pressure with the upper hatches of the container 152 open. It is possible to use a special container of the analog model, in which a special preset pressure level corresponding to the real pressure in a nuclear reactor is realized. In this case, the vapor content is controlled by the optical method using a television camera and an optical illuminator. This implements additional control of the vapor content in the analog model of a nuclear reactor. In the information processing unit 71, the vapor content parameters measured by the same optical sensors in the coolant of a nuclear reactor and in a model analogue of a nuclear reactor are continuously compared. This allows you to increase the accuracy and reliability of the obtained measurement results of the parameters of the coolant of a nuclear reactor. An additional factor in increasing the accuracy of measuring the vapor content and the reliability of the results obtained is the simultaneous use of three adjacent optical sensors located nearby and the simultaneous measurement of lateral scattered radiation by these sensors along with the measurement of attenuation of direct transmitted probe laser radiation.

The laser measuring system is developed on the basis of modern laser technology and optoelectronics and incorporates elements and products mastered and manufactured by the industry. In the measuring system, laser generators of the visible wavelength range and the ultraviolet wavelength range are used, which generate pulsed laser radiation, continuous laser radiation, and also provide tuning of the generated laser radiation within the entire visible wavelength range (laser generator pos. 2) in various embodiments and building a laser measuring system. Changing the parameters of the generated laser radiation, as well as turning on and off the laser generators, is carried out by commands from the control unit. As photodetector blocks, highly sensitive visible photodetector devices based on, for example, photoelectronic multipliers or semiconductor diodes are used. Photodetector blocks contain photodetectors, amplifiers, and blocks for digitizing received signals. Controlled optical filters are based on acousto-optic crystals, in which ultrasonic acoustic waves are excited using piezoelectric elements. Acoustic waves are excited using a high-frequency electric generator, which is part of a controlled optical filter. The interaction of laser radiation passing through an acousto-optic crystal with an excited ultrasonic wave provides filtering of laser radiation at a fixed wavelength determined by the wavelength of the ultrasound. This ensures the transmission of the received laser radiation with a wavelength generated by the laser generator, and filtering interference optical radiation arising from the operation of a nuclear reactor. Controlled optical filters, also called spectral tunable filters, are manufactured by industry [13], [14]. Optical shutters and optical switches are made on the basis of optical diaphragms and remote mirrors that block the luminous flux or introduced into the luminous flux using controlled stepper motors. It is also possible to use acousto-optic cells based on acousto-optic crystals operating in the mode of overlapping or switching the transmitted light flux. Important elements of the proposed laser measurement system are fiber optic lines paired with fiber adapters and beam expanders. Currently, the industry produces a wide range of fiber-optic lines and related elements - fiber adapters, which provide the interface of the fiber with the propagating laser beam. The beam expander is a fiber adapter that provides the formation of a wider laser beam cross section. Fiber adapters and beam expanders have the same composition. A diagram of a beam expander placed in a special waterproof box is shown in FIG. 8. The beam expander itself is a lens pos. 77, in the focus of which the output end of the fiber optic line 78 is located. The waterproof box body 79 ends with a flat output protective glass 80, adjacent to which the beam expander lens 77 is placed. It is possible to perform a beam expander without a protective glass, the functions of which are performed by the lens itself. The internal volume of the box is filled with inert gas. The industry produces fiber-optic lines operating in conditions of a high level of radiation, as well as high temperatures and ambient pressures. The industry has also mastered optical elements - lenses and lenses operating in conditions of radiation and elevated pressures and temperatures. Thus, at present, the creation of optical sensors suitable for operation in an active zone of a nuclear reactor is not a problem. It is also not a problem to create elements for outputting a fiber optic line from a coolant pipeline, or from a nuclear reactor vessel (terminal sleeve, pos. 76 in Fig. 5). An analogue model 40 of a nuclear reactor is made on the basis of a container filled with water (pos. 152 in Fig. 1), located outside the radiation zone and operating under normal atmospheric pressure. Due to the operation of the analog model in normal atmospheric pressure, the fiber-optic lines connecting the optical sensors to the optical measuring units are removed from the container 152 through its upper open hatches without the use of bushings. The required level of vaporization in the container is achieved by an electric heater. It is possible to use a special container adapted for operation under high pressure and temperature and fully reproducing the parameters of the coolant in a nuclear reactor, except for the presence of radiation. Ultrasonic pathogens 48, 49 are made on the basis of piezoelectric elements designed and designed to operate in an aqueous medium with an increased operating temperature. The optical illuminator 51 comprises a light source and a condenser forming a parallel light flux. It is possible to use a laser generator equipped with a beam expander as a illuminator. The television camera 52 contains a lens, a multi-element photodetector, and a block for digitizing signals from the matrix output. A high-performance computer equipped with a special program for processing television images, extracting image contours and counting processed elements — images of individual localized vapor bubbles — was used as an information processing unit. Such methods and image processing programs are known and used, for example, in laser locations [12]. As the control unit, a standard computer is used, equipped with interface units for communication with a set of controllable elements and devices of the laser measurement system. As a block of fast Fourier transform (FFT) 67, a specialized high-performance processor is used, equipped with a special program for performing digital fast Fourier transform of temporary signals from the output of the photodetector block. The information processing unit is equipped with a display on which the results of processing the incoming information and the parameters of the vapor content of the coolant at various points of the reactor where the optical sensors of the laser measurement system are installed are displayed. The measurement results from the information processing unit are also transmitted to the central control panel of the nuclear reactor.

The proposed laser system for measuring vapor content is intended for use in two types of aqueous nuclear reactors: RBMK and VVER. In both nuclear reactors, water is used as a coolant. The design and operating modes of the reactors have significant differences. This causes features in the installation of optical sensors of the laser measuring system in the working areas of nuclear reactors. RBMK is a single-circuit reactor with a boiling coolant, in which steam is formed directly in the reactor core. RBMK consists of many technological (fuel) channels, in each of which one fuel assembly (FA) is installed, through which coolant water passes under the influence of powerful circulation pumps. The outputs of all technological channels are combined in the main total pipeline and fed to a steam separator that separates the steam formed in the technological channels from water. Next, the steam from the steam separator enters the steam turbines rotating electric generators, and the water from the output of the steam separator enters the circulation pumps, from which the water again enters the entrances of the technological channels. Thus, the beginning of vaporization in these types of reactors is carried out in the technological channels of the reactor. Such a RBMK operation scheme (Fig. 9) determines the particular importance of measuring the vapor content at all points of the coolant circulation in the core of a nuclear reactor — in the places of steam formation in the RBMK technological channels. In the proposed laser system, optical sensors can be installed in all these critical places in the core of the nuclear reactor and its coolant circuit. Optical sensors can be installed in several selected technological channels of a nuclear reactor, for example, in a number of central channels, and in a number of peripheral channels in the core of a nuclear reactor. This will allow you to get a fairly reliable picture of the operating mode and vaporization in general in the technological channels of a nuclear reactor. It is possible to install optical sensors of the laser system in each of the available technological channels of a nuclear reactor. This will allow you to get the most complete picture of the vaporization and operating modes of each of the available technological channels and to quickly respond to any deviations from the standard operating mode of each individual technological channel. The installation of optical sensors in the main total output pipeline of technological channels (or the bypass of the main total pipeline) allows you to obtain important information about the operating mode of the entire nuclear reactor. It should be noted that it is possible to install optical sensors at the outlet of the steam separator to evaluate the parameters of the steam entering the steam turbines, as well as at the second water outlet of the steam separator to estimate the parameters of the vapor content in the return coolant at the entrances to the technological channels. This assessment can serve as a reference level for measuring vapor content in technological channels. To ensure the operation of additionally several optical sensors in the laser system, it is necessary to additionally include the appropriate number of optical switches and optical shutters, appropriately connected to the newly added optical sensors. In this case, laser generators and photodetector blocks remain in the same amount.

Thus, the use of the proposed laser system for measuring the vapor content in the RBMK system at various points in the reactor coolant circuit, as well as in the reactor core when installing optical sensors in the technological channels and in the control and monitoring channels, can significantly increase the amount of information about the operating mode and parameters of the coolant and active RBMK zones and, on the basis of this, increase the safety of this type of nuclear reactor.

The use of the proposed laser measurement system in VVER-type reactors also makes it possible to increase the operational efficiency and operational safety of these reactors. It is well known that VVER are double-loop case reactors in which steam generation is carried out by steam generators connected with the second coolant circuit. In the first coolant circuit, steam formation is unacceptable, since this leads to a decrease in the reactor operation efficiency, deterioration of heat removal from fuel assemblies, destruction of the surface layer of fuel assemblies and reduction of fuel assembly service life. Therefore, the installation of optical sensors in the VVER core directly near the surface of a fuel assembly provides important information on the operating mode of the reactor in its core and timely warning of the appearance of even small amounts of steam in the surface layer of a fuel assembly. It is advisable to install optical sensors in the second VVER circuit, as well as at the output of the steam generator, to obtain information on the parameters and quality of the steam coming further to the steam turbines. At present, the design of VVER hull reactors with boiling coolant in the reactor core is being carried out. Such reactors combine the advantages of RBMK and VVER double-loop reactors, in particular, steam generators are not required to operate nuclear power plants with such reactors. However, to ensure the efficiency and safety of operation of reactors of this type, it is very important to obtain accurate and reliable information on the parameters of the vapor content at various points in the reactor core and coolant. To solve this problem, it is advisable to use the proposed laser measurement system, which provides this information by placing optical sensors at various points in the active zone of nuclear reactors of this type.

It should be noted the possibility and prospects of using the proposed laser measurement system to control the quality of the steam coming from the steam separator to steam turbines. To implement the measurement of steam quality, optical sensors of the laser measurement system can be installed in the steam line at the entrance to the steam turbines, as well as at points of technological control inside the steam turbine.

Based on the materials of this application, a theoretical analysis and mathematical modeling of the process of probing laser radiation passing through the steam-water mixture of the coolant and measurements on this basis of the vapor content in the coolant with parameters corresponding to the current nuclear reactor are carried out. Field experimental studies of the analog model of a nuclear reactor were carried out. The conducted studies have confirmed the high accuracy of measuring the vapor content in the coolant based on the method of probing the coolant with laser radiation, implemented in the proposed laser measuring system.

In the submitted application for the invention, the following two factors of novelty of the invention should be noted. Firstly, it should be noted as a novelty the implementation of the on-line measurement of the coolant vapor content by the method of transmission of the coolant by probe laser radiation at any point of the coolant circuit, including in the reactor core of the RBMK type and also of the WWER type. An important factor is the removal of measuring equipment from the technical zone of a nuclear reactor through fiber optic lines. Secondly, as a novelty, a significant increase in information content should be noted when measuring the characteristics of the coolant of a nuclear power reactor. The proposed laser measuring system implements the possibility of using several optical sensors located at different points of the coolant and the core of a nuclear reactor. These optical sensors carry out continuous and constant monitoring of the optical parameters of the coolant in various operating modes of a nuclear reactor throughout its entire life from the start of fuel assembly loading to the completion of burning of nuclear materials. At the same time, a large amount of information is accumulated about the optical parameters of the coolant of a nuclear reactor throughout its entire operation. An information portrait of the state of the optical parameters of the coolant is formed in various stages and cycles of a nuclear power reactor. This information is of significant interest and can improve the efficiency of controlling a nuclear reactor, increase the safety of its operation.

The proposed laser measurement system provides high accuracy and reliability of the received information about the vapor content in the coolant of a nuclear reactor. This is ensured by using the optical method for measuring the parameters of the probe laser radiation that passed through the coolant at various points in the core of the nuclear reactor and the coolant circuit. High accuracy is ensured by the use of modern powerful laser generators of the visible wavelength range and highly sensitive photodetector blocks. This makes it possible to register one single vapor bubble in the coolant in the zone of passage of the probe laser radiation. Additional information is provided by the use of laser generators with a tunable wavelength of the generated radiation and measurements of the spectral transmittance of the coolant in a wide range of wavelengths. The proposed laser measuring system has high noise immunity and protection from all types of interference and electromagnetic influences, which are high in a nuclear reactor. This is due to the use of fiber optic lines and laser radiation proper, characterized by the absence of interaction of photons with the surrounding electromagnetic field and radiation-neutron radiation. The provision of high noise immunity is facilitated by the removal of the actual measuring equipment from the zone of operation of the nuclear reactor. An important factor in increasing the accuracy and reliability of measuring the vapor content is the use of an analog model of a nuclear reactor, which is used to model and create an aqueous medium (reference substance), the optical parameters of which correspond to the optical parameters of a real coolant in a nuclear reactor. Important information on the operating modes of a nuclear reactor is information on the nature of the temporal transmission spectrum of the coolant obtained using the fast Fourier transform (FFT) block. An important advantage of the proposed laser measurement system is the use of fiber-optic lines that allow measuring equipment to be moved outside the technical zone of the reactor to a distance of about 1000 meters or more. In the reactor core, only simple optical sensors are installed, connected by fiber optic lines to the measuring equipment. These optical sensors and fiber optic lines are adapted for operation in radiation, high pressures and temperatures. Thus, the proposed laser measurement system provides continuously received information on important parameters of the core and coolant of a nuclear reactor, as well as timely receipt of information on invalid or emergency parameters of the coolant in the technological channels of the core of a nuclear reactor. It can be argued that the existence of such a system for measuring the vapor content in the RBMK Chernobyl reactor would allow timely information on the start of an emergency increase in steam content and prevent thermal explosion of the reactor.

The proposed laser measurement system is the most appropriate means of solving the urgent problem of measuring the coolant parameters in modern RBMK and VVER reactors.

Information sources

1. RF patent No. 2065604 from 08.20.1996, the Method and device for determining the boiling of a liquid.

2. RF patent No. 2238547 dated 10/20/2004. A method for determining bubble boiling.

3. RF patent No. 2167457 dated 05/20/2001. A method for inertialess control of the vapor content in the coolant of a nuclear reactor.

4. RF patent No. 2437176. Publ. 12/20/2011. Bull. Number 35. Method and channel for detecting coolant boiling in the core of a WWER reactor.

5. RF patent No. 2136062 dated 08/27/1999, the Method for determining the steam reactivity coefficient at nuclear power plants with RBMK type reactor plants.

6. US 12/945,680. 12/12/2010.

7. RF patent No. 2580380, publ. 04/10/2016, Bull. No. 10. Method and system for steam quality control.

8. Mankevich S.K., Orlov E.P. Absorption-spectral photometric method for measuring the concentration of boric acid in the coolant of a cooling circuit of a nuclear power reactor. Atomic Energy, 2016, vol. 121, no. 5, S. 265-269.

9. Mankevich S.K., Orlov E.P. Absorption-spectral method for monitoring the characteristics of the coolant in a nuclear power reactor. Preprint FIAN No. 12. M. 2015, 34 p.

10. Mankevich S.K., Orlov E.P. A system for measuring the concentration of boric acid in the primary coolant circuit of a nuclear power reactor. RF patent No. 2594364 with priority dated 05/14/2015. Publ.: Application 10.10.2015. Patent publ. 08/20/2016 Bul. Number 23.

11. Mankevich S.K., Orlov E.P., Filichkina L.L. A system for measuring the concentration of boric acid in the coolant circuit of a nuclear power reactor. RF patent №2606369. Publ. 01/10/2017. Bull. No. 1. (prototype).

12. Mankevich S.K., Nosach O.Yu., Orlov E.P. et al. Laser location method and location device for its implementation. RF patent No. 229234. Publ. Bull. No. 9. 03/27/2005

13. Balakshiy V.I., Parygin V.N., Chirkov L.E. Physical foundations of acousto-optics. M .: Radio and communication. 1985.S. 134-234.

14. Balakshiy V.I., Mankevich S.K., Parygin V.N. Quantum Electronics. 1985, T. 12, No. 4.

15. Emelyanov I.Ya. et al. Management and safety of nuclear reactors. M .: Atomizdat, 1985.

16. Turbines of thermal and nuclear power plants. Ed. A.G. Kostyuk and V.V. Frolova. M .: Publishing House MPEI 2001, S. 488.

17. Dollezhal N.A., Emelyanov I.Ya. Channel nuclear power reactor. M .: Atomizdat, 1980 .-- 208 p.

18. Fedorov L.F., Rassokhin N.G. The processes of steam generation in nuclear power plants. M .: Energoatomizdat, 1985 .-- 288 p.

19. Arkhipov V.A. Laser methods for the diagnosis of heterogeneous flows. // Under. ed. Doctor of Philosophy THEM. Vasenina. Tomsk .: Publishing house of Tomsk University, 1987. - 141 p.

20. Vukalovich M.P. Thermophysical properties of water and water vapor. M .: Engineering, 1967. - 160 p.

21. Shelegov A.S., Leskin S.T., Slobodchuk V.I. Physical features and design of the RBMK-1000 reactor: a training manual. M.: NRNU MEPhI, 2011, 64 p.

22. Miropolsky Z. L., Shneerova R.I., Karamysheva A.I. Vapor contents during pressure movement of a steam-water mixture with heat supply and in adiabatic conditions. - Heat engineering, 1971, No. 5, p. 60-64.

23. Styrikovich M.A., Martynova O.I., Miropolsky Z. L. The processes of steam generation in power plants. M .: Energy, 1969. - 312 p.

24. Korn G., Korn T. Handbook of mathematics (for scientists and engineers). Definitions, theorems, formulas. // Per. from the second American revised edition of I.G. Aramanovich, A.M. Berezman, I.A. Weinstein, L.Z. Rumshisky, L.Ya. Zlafa. Under the general ed. I.G. Aramanovich

Claims (7)

1. A laser system for measuring the vapor content in the coolant of a nuclear power reactor, comprising first and second laser generators, first and second laser radiation meters, first and second optical switches, a first fiber adapter connected to a first fiber optic line, a first optical sensor located in the coolant pipeline of a nuclear power reactor and consisting of a first beam expander and a first optically sequentially installed at a fixed distance from each other reflector, as well as containing five translucent and one reflective mirrors, a control unit connected to the information processing unit, a first photodetector unit, optically coupled to the first controlled optical filter, the optical input of which is connected via a semitransparent mirror to the optical input of the first optical switch mounted on the optical axis of the first laser generator, the optical outputs of the first and second laser generators are simultaneously optically coupled through the first from pressure and translucent mirrors with the optical input of the first optical switch, the optical output of the first optical switch through the first fiber adapter and the first fiber optic line is connected to the optical input of the first beam expander in the first optical sensor, the control inputs of the first and second optical switches, the first and second laser generators and the first controlled optical filter are connected to the control unit, the first and second laser radiation meters are connected to to the information processing unit, the output of the first photodetector unit is connected to the information processing unit, the outputs of the first and second laser generators by means of translucent mirrors are connected respectively to the inputs of the first and second laser radiation meters, characterized in that the second and third optical sensors, three optical shutters, and the second are introduced and third photodetector blocks, second and third controlled optical filters, third and fourth optical switches, fast Fourier transform (FFT) block, seven fibers optical lines, seven fiber adapters, an optical illuminator, a television camera, a second reflective mirror, two translucent mirrors and an analog model of a nuclear reactor containing a container filled with water, with fourth, fifth and sixth optical sensors placed in it, a heating element, a temperature sensor, two ultrasonic exciters and a fan, while the analog model of a nuclear reactor is equipped with input and output optical windows, the second, fourth and fifth optical sensors with are made up of a beam expander and an optical reflector, the third and sixth optical sensors consist of two beam expanders located on the same optical axis at a fixed distance from each other, connected to fiber optic lines, the second and third optical sensors are located together with the first optical sensor in the pipeline the coolant of a nuclear reactor, the optical input of the second photodetector through a second controlled optical filter and a newly introduced translucent mirror is connected to the optical input ohm of the third optical switch, the first optical shutter is mounted on the optical axis of the first laser generator in front of the optical input of the first optical switch and optically connects the outputs of the first and second laser generators simultaneously with the optical input of the first optical switch, the optical input of the second optical shutter by means of three translucent mirrors and the first reflective mirrors connected simultaneously with the optical outputs of the first and second laser generators, the optical output the second optical shutter is optically connected to the optical input of the third optical switch, the optical input of the third optical shutter by means of a second reflective mirror, three translucent mirrors and the first reflective mirror is optically coupled simultaneously with the optical outputs of the first and second laser generators, the optical output of the third optical shutter is optically connected to the optical the input of the fourth optical switch, the optical output of the third optical switch by w The optical fiber adapter and the optical fiber line are connected to the optical input of the second beam expander of the second optical sensor, the optical output of the fourth optical switch by the third optical adapter and the optical fiber line is optically connected to the optical input of the third beam expander in the third optical sensor, and the second optical output the fourth optical switch through the sixth fiber adapter and fiber optic line is optically connected to the seventh beam expander of the sixth of the optical sensor located in the container of the analog model of a nuclear reactor, the second optical output of the first optical switch is optically connected via the fourth fiber adapter and fiber optic line to the optical input of the fifth beam expander in the fourth optical sensor located in the container of the analog model of the nuclear reactor, the second the optical output of the third optical switch by means of the fifth fiber adapter and fiber optic line is optically connected to the optical input of the sixth expansion of the beam detector in the fifth optical sensor located in the container of the analog model of a nuclear reactor, the optical output of the fourth beam expander in the third optical sensor is optically coupled to the first optical input of the second optical switch by the fiber optic line and the eighth fiber adapter, and the optical output of the eighth beam expander of the sixth the optical sensor is optically coupled via a fiber optic line and a seventh fiber adapter to a second optical input of a second optical switch studio, the optical output of the second optical switch is connected to the optical input of the third controlled optical filter, the output of which is optically connected to the optical input of the third photodetector unit, the outputs of the second and third photodetector units are connected to the inputs of the information processing unit, the output of the third photodetector unit is additionally connected to the input of the fast unit Fourier transform, the output of which is connected to the information processing unit, the control inputs of the third and fourth optical switches are are connected to the control unit, the control inputs of the second and third controlled optical filters are connected to the control unit, the control inputs of the three optical shutters are connected to the control unit, the television camera and the optical illuminator are located on the same optical axis passing through the volume of the container of the analog model of a nuclear reactor, the optical input of the television camera is optically connected to the first optical porthole of the analog model, and the optical output of the optical illuminator is connected to the second optical illumination the luminaire of the analog model, the output of the television camera is connected to the information processing unit, the optical illuminator is connected to the control unit, the first and second ultrasonic exciters are connected to the control generator, the input of which is connected to the control unit, the temperature sensor is connected to the information processing unit, a heating element and a fan connected to the control unit. 2. The system according to claim 1, characterized in that in it the optical reflectors are made on the basis of a multi-element matrix of corner optical reflectors. 3. The system according to claim 1, characterized in that the beam expander is placed in a waterproof box provided with an optical porthole. 4. The system of claim 1, wherein the optical sensor comprises sequentially optically coupled beam expander, a rotary reflective mirror and an optical reflector, wherein the rotary reflective mirror and the optical reflector are provided with fairings. 5. The system according to claim 1, characterized in that the second laser generator in it is configured to tune the wavelength of the generated laser radiation within the visible wavelength range. 6. The system according to claim 1, characterized in that in it a controlled optical filter is made on the basis of an acousto-optic cell operating in the visible wavelength range. 7. The system according to claim 1, characterized in that the optical sensor contains a series-optically coupled input beam expander, a first optical reflective mirror, a second optical reflective mirror and an output beam expander.

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