RU2781858C1 - Neutron detector with solid and liquid moderators for measuring neutrons in various energy ranges - Google Patents

Abstract

FIELD: neutron radiation measurement.

SUBSTANCE: invention relates to the field of measurement of neutron radiation. The detector contains a cylindrical chamber (1) for the movement of a solid moderator, a detector measuring chamber (2) and a chamber (3) containing a liquid moderator, which are installed on top of each other. The detection measuring chamber (2) contains a detector (4) in the center and a tungsten shell (9) that provides protection of the detector surrounding it from gamma radiation. The lever (5) for moving the solid moderator is attached to the solid moderators (7) and therefore allows them to move along the vertical axis.

EFFECT: improving the accuracy of neutron measurements in various energy ranges.

11 cl, 8 dwg

Description

Technical field

The present invention relates to a detector whose task is to provide a variable layer of solid and liquid moderators and therefore measure neutron radiation in different energy ranges by programming before the measurement or by remote control during the measurement.

State of the art

The main task of neutron detectors is to reduce the energy of neutrons received by the detector through scattering. In such a case, the solution is the need to slow down the neutrons to a low energy level, the so-called thermal energy level, in order to capture them. Otherwise, neutrons whose energy will not be reduced to this level will not be captured and will leave the detector without capture, and, therefore, the user cannot measure these neutrons in the medium. For this purpose, materials called moderators are used in the outer layer of neutron detectors. A neutron in the medium first passes through this material and, after losing its energy, enters the main detector tube.

The required intensity of neutron interaction to reduce its energy to the thermal energy level, which is the measured level, varies depending on the value of its initial energy. Since the neutron, which has a high energy, scatters to a greater extent, therefore, its energy can decrease to a thermal energy level, compared to a neutron, which has a lower amount of energy. High-energy neutrons require moderation by means of a thicker moderator layer.

In a variety of applications, such as particle accelerators, the use of which is gradually becoming more common, and nuclear power plants, secondary neutron radiation is produced in a wide energy range. In this context, it is known that measurements made using detectors containing a thick layer of a single and fixed moderator are unsuitable for counting most of these neutrons.

In most neutron detectors currently in commercial use, fixed-size moderators or moderator arrays of varying thicknesses are found to be preferred. In such cases, neutrons that do not have sufficient energy to pass through the moderator layer are unable to enter the main detector tube in which the measurement is to be made. Even though they may pass through the moderator layer, neutrons that are high in energy and are not moderated to a measurable energy level exit the detector tube uncaptured.

The prior art finds use in the neutron detector model FHT 762 Wendi-2, which is supplied by Thermofisher. In this detector, a solid material having a wall thickness of 22 cm is used as a moderator. With this design approach, taking into account the above description, the detector has a low sensitivity.

Another neutron detector that finds use in the prior art is the Microspec neutron probe from Bubble Technology Industries. This design uses two detectors that have different moderator thicknesses to increase the energy range of the measurement. In this case, the degree of sensitivity of the detector measurement is increased, but it still turns out to be impossible to measure in a wide energy range.

Other designs that find industrial application and meet the requirements for detectors having different moderator thicknesses are detectors in which the moderator thickness can be changed by using a plurality of detectors surrounded by moderators having different thicknesses, or these changes can be made manually by users. .

Other prior art spectrometers are the Bonner Spherical Spectrometer from Else Nuclear and the Nested Neutron Spectrometer from Detec. Considering the space they occupy, their mass and the difficulties in operation, it becomes obvious that it would be impractical to carry out neutron measurements using these detectors. In the case of the Nested neutron spectrometer, the user must enter the irradiated room and change the moderator after each measurement. In this case, the duration of the measurement must be increased so that measurements can be made over a wide energy range. In addition, since the level of radiation in the irradiated room does not drop sharply to zero immediately after the completion of the irradiation process, entering the irradiated room is inappropriate in terms of radiation safety.

Another spectrometer used in the prior art is a rotating neutron spectrometer manufactured by Bubble Technology Industries. This design is achieved by arranging seven individual detectors with different moderator thicknesses in a rotating system. Although this design is more successful than other designs because it can measure in the thermal energy range up to 4.5 MeV, this energy range is still insufficient for most applications in which secondary neutrons are produced. In addition, this system cannot provide variety in accordance with the requirements of users. During the rotation process, the measurement resolution will decrease depending on the detectors located in different irradiated areas of the primary irradiation zone.

Another invention known from the prior art is US 20180224565. When analyzing said patent document, it can be seen that the aim is to offer a moderator layer of varying thickness through the use of a liquid moderator. This embodiment is achieved by filling the containers located in the detector, which are presented in a spherical shape, with the introduction of liquid from the reservoir. When analyzing the description of this invention, it becomes apparent that this design does not meet the established requirements for preventing gamma radiation in the environment. In most embodiments where neutron production occurs, high intensity gamma radiation is also present. To allow the detector to efficiently measure neutrons, gamma radiation must be filtered out. According to this patent document, it can be understood that the detection container has a spherical geometry. Since movement with such a spherical geometry would be impossible, the chambers that will fill the liquid moderator are made of a material such as aluminum or lead and occupy a fixed position with respect to the detector. In this regard, even if the liquid moderator flows out when there are enough attached layers around the detector tube, it can be understood that this design is not applicable to the measurement of low energy neutrons.

The most important feature of the design according to the present invention is that the user can control time dependent changes such as the location of the solid moderators and the stage of filling the chambers with liquid. In different neutron radiation environments, when different parameters are required, the design must be adjustable.

The essence and purpose of the present invention

The object of the present invention is to develop a neutron detector that is capable of measuring at high levels of sensitivity over a wide energy range using a new design logic that is quite different from neutron observation instruments currently used in industry.

It has been suggested that solid and liquid moderators, which have variable thickness, be used in the same design instead of a single solid moderator that is not applicable to thickness variation. Due to its variable moderator design, such a detector allows the user to measure at various moderator thicknesses in a single exposure through pre-programming or remote control during the measurement.

Thus, a neutron detector is provided that is capable of making accurate measurements, overcomes measurement limitations in the low energy range, and allows the user to make measurements at the energy levels determined by the detector. Another important and significant feature of the detector is to allow the use of various solid and liquid moderators in the detector in research and development.

In a neutron detector with solid and liquid moderators, the user can control time-dependent changes, including the location of solid moderators, as well as the stage of liquid filling of the chambers. In different zones of neutron radiation, when different parameters are required, the design must be made with the possibility of regulation.

Brief description of the drawings

The following are figures and corresponding descriptions used for the purpose of better understanding the solid and liquid moderator neutron detector that has been developed according to the present invention.

In FIG. 1 is a perspective view of a neutron detector according to the present invention.

In FIG. 2 is a side view of a neutron detector according to the present invention.

In FIG. 3 is a plan view of a neutron detector according to the present invention.

In FIG. 4 is a block diagram of the electronic construction of the neutron detector according to the present invention.

In FIG. 5 is a sectional view of a neutron detector according to the present invention.

In FIG. 6 is a top perspective view of a neutron detector according to the present invention.

In FIG. 7 is a side view of a neutron detector according to the present invention.

In FIG. 8 is a side perspective view of a neutron detector according to the present invention.

Figure Legend Definitions

In order to better understand the solid and liquid moderator neutron detector that was developed according to the present invention, the elements and details shown in the figures are numbered, with each number having its corresponding definition given below.

1. Chamber for the movement of a solid moderator

2. Detection measuring chamber

3. Chamber containing liquid moderator

4. Detector

5. Lever for the movement of the solid retarder

6. Trajectory of the liquid moderator

7. Solid moderator

8. Holes for moving the liquid moderator

9. Tungsten shell

10. Sliding gaps

11. Cable connecting the detector to the signal processing device

12. Cable connecting signal processing unit to external processing unit

13. Signal processing device

14. External processor device

15. Driving device

16. Touch device

17. Liquid tank control

18. Control device of power supply circuits

19. Storage device

20. Warning device

21. Status Reader

Detailed description of the present invention

The present invention is a neutron detector which is capable of measuring neutrons in various energy ranges according to the present invention, said detector having:

• a chamber (1) for the movement of the solid moderator, containing solid moderators (7), and the solid moderators can move along the vertical axis,

• a lever (5) for moving the solid moderator, which allows the solid moderators (7) to move along the vertical axis in the chamber (1) for the movement of the solid moderator,

• a detector (4) that measures neutrons,

• detector measuring chamber (2), in which the detector (4) is located,

• chamber containing liquid moderator (3), which contains liquid moderator,

• the trajectory (6) of the liquid moderator, which is connected to the chamber (3) containing the liquid moderator, through which the liquid moderator passes,

• openings (8) for moving the liquid moderator, which are located on the ceiling of the chamber containing the liquid moderator (3),

• shell (9), which prevents gamma radiation in the environment, surrounding the detector (4),

• sliding gaps (10), which are located on the solid retarder (7), through which, during movement, the ends fixing the solid retarder can pass, located on the lever (5) for the movement of the solid retarder, and

• electronic control device.

Solid moderators (7) are made of polyethylene or high-density polyethylene material, to which cylinders having a wall thickness of 1 cm are connected and attached to a lever (5) for moving the solid moderator. The solid moderators (7) move in the sliding gaps (10) for the solid moderator as a result of the movement of the lever (5) for moving the solid moderator along the vertical axis. After the solid moderator (7) is placed in the detection measurement chamber (2), the lever (5) for moving the solid moderator releases the user-defined solid moderator (7) by rotating at a certain angle with respect to the horizontal axis. After completion of the process, the lever (5) for moving the solid moderator returns to the chamber (1) for moving the solid moderator.

The detector (4) containing gaseous BF ₃ or ³ He is fixed in the center of the detector measuring chamber (2). The information cable attached to the detector (11) is connected to the signal processing device (13) by moving out of the gap in the lever (5) for the movement of the solid moderator. The detector (4) is covered by a hollow cylindrical shell (9) made of tungsten material and having walls 1 cm thick to protect the detector (4) from gamma radiation in the medium.

In cases where the measurement is not carried out, the part remaining outside the detector measurement chamber (2) outside the detector (4) and the tungsten sheath (9) is called the gap.

The liquid moderator-containing chamber (3) is a container that contains a liquid intended for use as a moderator. The trajectory (6) of the movement of the liquid moderator is attached to the chamber containing the liquid moderator, and the liquid is loaded and unloaded through this trajectory. When necessary, the trajectory (6) of the liquid moderator moves along the vertical axis, and thus the liquid can be supplied to fill the corresponding gaps in the detection measurement chamber (2). Holes (8) for moving the liquid moderator are present in the ceiling of the chamber (3) containing the liquid moderator. The openings (8) for moving the liquid moderator by their action allow the liquid contained in the chamber (3) containing the liquid moderator to pass into the detection measuring chamber (2). All of said holes are controlled by the user using an electronic control device, and the passage of the liquid moderator is allowed from the holes to be filled with liquid moderator, according to the zone between the solid moderators (7), which is intended to be filled.

In research and development, various detector configurations can be obtained, since the liquid intended for use as a moderator in the detector can be loaded and unloaded using the trajectory (6) of the movement of the liquid moderator, and solid moderators (7) can be installed and removed from the lever (5) for the movement of the solid moderator. Thus, the user is given the opportunity to improve the detector.

The neutron detector consists of several components and many different electronic devices that have been standardized for nuclear instrumentation. They are a signal processor device (13), an external processor device (14), a drive device (15), a sensor device (16), a control device (17) of a liquid reservoir, a control device (18) of power supply circuits, a memory device (19) , a warning device (20) and a device (21) for reading status data. In FIG. 4 is a block diagram of the electronic control device of the neutron detector. The electronic control device consists of components which are detailed below.

Signal processor (13)

The signal processing device (13) of the neutron detector performs the function of the brain of the system. The signal processing device (13) performs all the actions that the system must perform, and also provides communication between other components in the electronic control device.

Drive unit (15)

The motion of the moderator layers in the neutron detector is controlled by means of a DC motor.

Touch device (16)

Since the neutron detector operates in the radiation zone, state data such as temperature, humidity, pressure must be obtained. The reading of said data is carried out in the sensor device.

Control device (17) liquid reservoir

The chamber (3) containing the liquid moderator is located at the bottom of the neutron detector. Said chamber must be adjusted to protect the detector from any damage that may result from fluid leakage. The liquid contained in the chamber (3) containing the liquid moderator is continuously regulated by the liquid reservoir control device (17).

Control device (18) of power supply circuits

The power circuit manager supplies power to electronic components and regulates the amount of current that electronic devices draw.

Storage device (19)

The memory device (19) of the neutron detector stores the received and processed data. Thus, there is a possibility of data redundancy. Warning device (20)

The warning device (20) warns about the activation of the detector when the intensity of the incoming neutrons or the dose rate of the medium reaches a value that exceeds a certain level.

Device (21) for reading status data

The reception and interpretation of the data received from the sensor device is carried out in the device for reading the status data. Said device ensures that the detector operates smoothly by evaluating the status data.

External processor device (14)

When the entire system is operated jointly, the user can manage all data from a single center using an external processor device (14).

The neutron detector of the present invention allows the user to change the moderator thickness by programming prior to irradiation or remote control during irradiation, which may distinguish the neutron detector of the present invention from prior art neutron detectors. Variable thicknesses of the moderators can be obtained by filling liquid moderator with constant volume channels located in the moderator chamber. Thus, it becomes possible to measure neutrons in a wide energy range, and this is the difference from the neutron detectors known from the prior art.

The use of a neutron detector having all of these characteristics in critical areas of research in which the neutron energy range must be known in detail contributes to the fulfillment of important industrial requirements. In addition, the neutron detector according to the present invention does not take up much space and is quite portable.

According to an embodiment of the present invention, the neutron detector has a length of 88 cm and a cylindrical structure having a diameter of 21 cm.

Claims (30)

1. A neutron detector capable of measuring neutrons in various energy ranges, characterized in that it contains: a chamber (1) for the movement of a solid moderator containing solid moderators (7), and the solid moderators can move along a vertical axis, a lever (5) for moving the solid moderator, which allows the solid moderators (7) to move along the vertical axis in the chamber (1) for the movement of the solid moderator, a detector (4) that measures neutrons, detector measuring chamber (2), in which the detector (4) is located, chamber containing liquid moderator (3), which contains liquid moderator, the trajectory of movement (6) of the liquid moderator, which is connected to the chamber (3) containing the liquid moderator, through which the liquid moderator passes, openings (8) for moving the liquid moderator, which are located on the ceiling of the chamber containing the liquid moderator (3), shell (9), which prevents gamma radiation in the medium, surrounding the detector (4), sliding gaps (10), which are located on the solid retarder (7), through which, during movement, the ends fixing the solid retarder can pass, located on the lever (5) for the movement of the solid retarder, and electronic control device. 2. The neutron detector according to claim 1, wherein the electronic control device comprises: a signal processing device (13), which performs all the system actions to be carried out and provides communication between other devices, a drive device (15) that regulates the movements of the moderator layers in the neutron detector, a sensor device (16) that reads out status data such as temperature, humidity and pressure, a control device (17) of the liquid reservoir, which constantly regulates the liquid contained in the chamber (3) containing the liquid moderator, a control device (18) of the power supply circuits, which ensures the transfer of energy to electronic components and regulates the amount of current consumed by electronic devices, a storage device (19) in which the received and processed data are stored, a warning device (20) that provides a warning about the activation of the detector when the level of incoming neutrons or the dose rate of the medium reaches higher values than a certain level, device (21) for reading status data, in which data is received from the sensor device (16) and data is interpreted, an external processing device (14) that allows the user to manage all data from a single device. 3. A neutron detector according to any one of the preceding claims, wherein the thicknesses of the solid and liquid moderators can be changed by remote control by the user. 4. A neutron detector according to any one of the preceding claims, which comprises a cable (11) connecting the detector to the signal processor device, which provides a connection between the detector (4) and the signal processor device (13). 5. A neutron detector according to any one of the preceding claims, wherein it comprises a cable (12) which provides a connection between the signal processor device (13) and the external processor device (14). 6. The neutron detector according to claim 1, wherein it has a length of 88 cm and a cylindrical structure having a diameter of 21 cm. 7. The neutron detector according to claim 1, wherein the detector (4) is a BF ₃ based detector. 8. A neutron detector according to claim 1, wherein the detector (4) is a ³ He based detector. 9. Neutron detector according to claim 1, wherein the sheath (9) is a tungsten sheath. 10. Neutron detector according to claim 9, wherein the tungsten shell (9) has a wall thickness of 1 cm. 11. Neutron detector according to claim 1, wherein the solid moderators (7) have a wall thickness of 1 cm.

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