A PASSIVE RADON GAS MEASUREMENT SYSTEM

TECHNICAL FIELD

The invention relates to a passive radon gas measurement system, comprising a bath unit, a reading unit and a software, in which CR-39 (Colombia Resin) and LR- 115 detectors that have been exposed to radioactivity are made ready for reading.

BACKGROUND

Inhalation of radon gas, which is accepted as a Class A cancerogenic by the World Health Organization and USA Environmental Protection Agency (EPA), is shown as the second most important cause of lung cancer after smoking.

In environments where the limit values of radioactive radon gas are exceeded, there is a threat to human health. Regarding to this, it is a legal requirement to measure the radon gas concentration in places determined by law (Art. 37 & 38 - 24.3.2000 dated and 23999 numbered Official Gazette).

TENMAK (Turkish Energy, Nuclear and Mining Research Institute) is the only authorized institution in the measurement of radon concentration in our country. Since there are no locally produced Radon measurement systems, there is a foreign dependency. With producing these measurement systems in our country, we will be able to take faster and more reliable measurements, while our foreign dependency will be eliminated. Increasing the number and quality of measuring devices is important for our country.

A "radon free" certificate is required for residences that are on sale in European Union countries. Since the increasing cancer cases are taken into account, the radon gas concentration must be measured first for the new residential areas.

Today, radon gas measurements are accepted as one of the most effective and important methods in earthquake prediction studies. Especially the United States of America and Japan gave importance to this method and allocated a large amount of resources. For this reason, they have created many radon measurement networks. For example, the United States has more than 100 radon measurement stations only in the Parkfield, California area for predicting earthquakes. (https://tinyurl.com/2d5634wh). Since radon element can be found in the raw material used in concrete production or stone materials used in construction, it creates a cancer hazard. Therefore, since the mentioned building materials contain radon, the radon rate is a necessary value within the scope of the urban transformation project.

Especially the radon hazard in mines is higher than the level of danger in homes and other workplaces. Therefore, it is a legal obligation to make radon measurement in mines. Radon measurements in mines and various public institutions and organizations in our country are carried out partially in cooperation with TENMAK and the Ministry of Health.

In addition to the harmful effects of radon gas, there are very few therapy centers in our country that use the positive effects of radon gas for therapeutic purposes.

In accordance with the 37th and 38th articles of the Official Gazette dated 24.3.2000 and numbered 23999, the annual average value of 400Bq/m3 in homes and 1000Bq/m3 in workplaces should not be exceeded. Therefore, it is a legal requirement to measure radon in residences and workplaces.

LIST OF FIGURES

Figure 1 . General View of the Bath Unit

Figure2. General View of the Exposure Bath

Figures. Track Bath

Figure4. General View of the Reader Unit

Figures. General View the Movement Parts of the X, Y, Z Axis

Figures. The Carrier Platform for X/Y Axis

Figure?. The Carrier Platform for Z Axis

Figures. Movement Mechanism of Z Axis

1. Track Etching Unit

2. Rinse Tank

3. Exposure Tank Drain Valve

4. Rinse Tank Drain Valve

5. CR39 Cartridge

6. Cartridge Circle

7. Resistance 8. Exposure Tank

9. Temperature Sensor

10. Reading Unit

11 . Upper Cover

12. Side Cover

13.220V Energy Input

14. Device on/off switch

15. USB Connector

16. Front Cover

17.Z-Axis carrier platform

18. Vibration absorbing carrier feet 19.20x20 Sigma aluminum profile

20.X/Y Axis carrier platform

21 . illuminated surface

22. Bottom isolation surface

23. Electronic control circuits chamber

24.X axis step motor

25.X axis step motor carrier

26.X axis coupling

27.X axis GT2 gear

28.X axis pillow bearing

29.X axis optical limit switch

30.X axis buttress shaft

31. Y axis pillow bearing

32. Y axis step motor carrier

33. Y axis step motor

34. Y axis coupling

35. Y axis pillow bearing

36.X axis pillow bearing

37.X axis locked shaft nut and carriage

38. Y axis carrier carriage

39. Y axis shaft locked nut

40. Y axis buttress shaft

41. Y axis pillow bearing 42. Y axis pillow bearing

43. Y axis shaft locked nut

44. Y axis buttress shaft

45. Electronic Microscope Camera

46.X axis Gt2 belt tightener

47.X axis Gt2 gear

48.X axis pillow bearing

49.X axis buttress shaft

50.X axis locked shaft nut and carriage

51.Y axis Gt2 gear

52. Y axis Gt2 belt tightener

53.X axis locked shaft nut and carriage

54. Y axis Gt2 gear

55. Y axis optical limit switch

56.X axis bearing nut

57. Z axis shaft bearing

58. Z axis steel shaft

59. Z axis locked shaft nut and carriage

60. Z axis buttress shaft

61 . Z axis shaft bearing

62. Z axis steel shaft

63. Cable canal

64. Z axis steel shaft

65. Z axis shaft bearing

66. Z axis buttress shaft

67. Electronic Control Card

68. Z axis shaft fixer

69. Z axis shaft bearing

70. Z axis steel shaft

71 . Z axis pillow bearing

72. Z axis locked shaft nut and carriage

73. Z axis shaft fixer

74. Detector Carrier Cartridge

75. SMPS Feeding Unit 76. Z axis shaft fixer

77. Z axis ball bearing

78. Z axis Gt2 gear

79. Z axis coupling

80. Z axis step motor

81 . Z axis step motor carrier

82. Z axis optical limit switch

83. Z axis belt tightener

84. Z axis Gt2 gear

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a passive radon gas measurement system, comprising two separate units and a software, in which the radioactive CR-39 (Colombia Resin) and LR-115 detectors are made ready for reading.

The chemical structure of passive nuclear trace detectors, whose trade name is CR-39, consists of allyl diglycol carbonate. The CR-39 detector, which is a kind of plastic made by combining the optical properties of glass with mechanical and physical properties and hardened under heat, can only record ions with high atomic numbers. It has optical properties comparable to glass, and its surface is shiny and smooth like glass. The chemical formula of CR-39, which is a polymer, is C12H18O7.

Another Radon detector is the LR-115 film detectors. It comprises a 100pm thick polyester base coated with a 12pm thick red colored thin film of cellulose nitrate. These film detectors, developed by KODAK, are sensitive only to oc particles and are insensitive to other types of radiation. The requirement of a certain minimum distance from the source in order for LR-115 film detectors to detect alpha particles provides these film detectors two different advantages. The detectors are insensitive to surface depositions of alpha emission radon decay products such as Po-218. Therefore, the plate out effect cannot be mentioned in dosimeters. In addition, in the protection containers produced for the protection of LR-115 film detectors, the distance between the film surface and the container surface is less than the distance required for alpha detection. For this reason, no background formation is observed in such dosimeters. It is possible to attach these detectors to the existing system and to measure the Radon concentration. For this, it is sufficient to install LR-115 cartridges on the system. The first unit is a bath unit. The bath unit is a device used to prepare radioactive CR-39 (Colombia Resin) and LR-115 solid state nuclear trace detectors for reading. This is called the "Nuclear Track Etching Unit". The CR-39 is a polymer with a chemical formula of C12H18O7 in plastic structure. And the LR-115 has a polyester structure of 100pm thickness covered with a thin red cellulose nitrate film. The radon concentration is measured by counting the traces left by the nuclear particles originating from radon gas on the CR-39 and LR-115 polymer.

The track etching unit (1 ) comprises two separate tanks. An exposure tank (8) and a rinse tank (2). Sodium hydroxide in the exposure tank (8) is used for exposure of the CR-39 and the LR-115. This process ensures that the polymer chain, which is broken by being exposed to nuclear particles, is separated from the surface of CR-39 and LR-115.

The exposure tank (8) comprises Sodium Hydroxide dissolved in the liquid during processing. This tank comprises a mechanical mixer so that the Sodium Hydroxide is dispersed homogeneously in the liquid and does not get crystallized into the liquid, a timer that controls the mixer and an electronic control unit which further comprises the heater controls. The tanks are made of stainless steel in order not to be affected by chemicals. Teflon, a chemical resistant material, is used in plastic connection hoses and other parts.

Sodium hydroxide has a solid, crystalized structure. In order for the Sodium Hydroxide to dissolve in the liquid and ensure its activity, the liquid is heated up to 90°C for CR-39 and 60°C for LR-115. These data are obtained from the literature. Therefore, there is a heater under the exposure tank (8). With this heater, the liquid in the exposure tank (8) can be adjusted between 0-120°C at 0,5°C intervals. The exposure unit, which is controlled by the system settings made by the user (heating temperature, mixing speed, time), automatically controls itself according to the value coming from the sensor and automatically stops the system and gives an alarm when the exposure time is completed.

The mechanical mixer can be adjusted between 5-30 rpm. These speed values are determined as a result of multiple tests. Very fast mixing causes the liquid to splash out from the lid, while mixing at low speed causes crystallization to start. For this reason, the experimentally found speed values are loaded into the system as a preset.

Sodium hydroxide (NaOH) acidic solution is brought to 90°C and 60°C temperature values, which are the most suitable temperatures in the literature, and tracking procedure is performed. In the literature, tracking procedure basically includes the following function. If CR-39 and LR-115 are exposed to nuclear particles, the chain breaks in the polymer chain that makes up the CR-39 structure. In LR-115, degradation occurs in the cellulose nitrate covering the surface. The broken/degraded structure can no longer hold on to the surface as before. However, since it is not appropriate to mechanically separate this broken/degraded structure from the surface, it is ensured that the structure is separated from the surface by a chemical method without damaging the detector. NaOH is used for this. These temperature values are necessary for the crystallized NaOH to dissolve in water and remain stable. The system is designed to operate at different temperature values (0-120°C) than the temperature value accepted in the literature, taking into account factors such as the NaOH to be used will not always be taken from the same place, it may be fresh or stale, its quality and density may change. As stated in the literature for CR-39, 75% distilled water and 25% NaOH solution are used at 90°C, and for LR-115, 90% pure water and 10% NaOH solution are used at 60°C. After the tracking process, it is taken to the second tank and cleaned in an alkaline environment. CR-39 and LR-115 cartridges, whose exposure process has been completed, are put into the rinse water, so that the Sodium Hydroxide is separated from the detectors and overexposure is prevented. If cleaning is not done, surface deterioration may occur on the CR-39 and LR-115 surfaces due to exposure to excessive acid, which may cause reading errors.

Detectors that have been cleaned are taken to a dust-free, light-free place to dry.

A temperature sensor (9) with NTC type is used in the track etching unit. This sensor is a temperature sensor with a resistance value that changes depending on the temperature. This sensor is connected to one of the microcontroller's ADC (Analog to Digital Converter) input terminals. The ADC unit in the microcontroller has a resolution of 10 bits. 10-bit resolution corresponds to 1023 measuring steps. Since the supply voltage of the circuit is 5V and an external ADC Vref is not used, the Vref unit of the ADC also works with 5V. Thus, a step voltage is calculated with the formula 5000mV/1023 = 4.88mV. NTC is connected to the system with a 4.7K voltage divider resistor. Since the V value obtained from the ADC unit is the V value on the voltage divider, the R value on the NTC is calculated using this and this value is converted into the temperature value depending on the beta value of the NTC. By comparing the temperature data with the settings made by the user, a resistance (7), which is connected to the electronic control unit via the relay, is activated in cases where the temperature of the exposure tank (8) falls, and the liquid is heated. When it rises above the required temperature, the resistance (7) is turned off and the temperature is checked to be at appropriate values. The mixer motor is a geared DC motor. A bridge circuit has been prepared by using mosfet (metal oxide semiconductor field-effect transistor) for speed control of this motor. The PWM unit of the microcontroller is used to control this full bridge circuit. This unit produces PWM frequency at the desired frequency and duty ratio (not more than of the operating speed of the microcontroller). It has 10-bit resolution. PWM at 10Khz is used to ensure the rotation of the motor at the desired speeds. The speed adjustment is made by changing the duty ratio of this PWM between 0% and 100% duty with 1024 steps. This speed adjustment takes place in accordance with the setting made by the user. A led driver circuit is used to display the settings made on the screen. With the same microcontroller, a display is provided by using LED lighting and seven segment displays.

Detectors that have been traced and made ready for reading are taken to the micro-controlled reading unit which is the second unit. With the detector carrier cartridge (74), which can carry CR-39 or LR-115, the detectors are placed in the reading unit.

The reading unit (10) is produced in the form of a closed box in order to protect it from external effects (dust, sunlight, fluorescent light, etc.). For this, an upper cover (11 ), a side cover (12) and a front cover (16) are placed around the device. On the right side of the device, a 220V energy input (13), a device on/off switch (14) and a USB connector (15) are located. It is mounted on a multiple of vibration absorbing carrier legs (18) to prevent vibration during axis movements. There is a window on the front cover (16) to place the detector cartridges. The detector cartridges are attached to the slots on a Z-axis carrier platform (17) from this window.

20x20 sigma aluminum profiles (19) are used to ensure both the strength of the outer frame and its assembly. X and Y axes are mounted on a X/Y axis carrier platform (20). The upper surface of the Z-axis carrier platform (17) is designed as an illuminated surface (21 ) in order to illuminate the detectors. A lower isolation surface (22) is used to separate an electronic control circuits chamber (23) used for electronic circuits from the reading part. This surface is designed with a temperature protection. It does not transmit the heat of the below electronic chamber into the reading chamber. A step motor (24) is used for X-axis movement. This motor is mounted on an x- axis step motor carrier (25). The motor is connected to an X-axis buttress shaft (30) with an x-axis coupling (26) at the motor end. An X-axis Gt2 gear (27) is placed on the shaft for Gt2 belt connection. A multiple of X-axis pillow bearings (28, 36) are used to fix the X-axis buttress shaft (30). In order to provide movement on the X-axis buttress shaft (30), an x-axis locked shaft nut and carnage (37) are used. There is a second X- axis buttress shaft (49), which takes its motion via the Gt2 gear connected to the X- axis step motor (24) by being connected the other buttress shaft with an X-axis gt2 gear (47) in order to ensure the error-free movement of the X-axis. The belt tension between these shafts is provided by an X-axis Gt2 belt tightener (46). A multiple of X- axis pillow bearings (48) and an X-axis bearing nut (56) are used to fix the X-axis buttress shaft (49). The X-axis table moves with the x-axis locked shaft nut and carriage (37). Since the system uses a single motor for the X-axis and allows the two X-axis buttress shafts (30, 49) to rotate at the same rate via the connecting belt, the upper and lower movements are the same, and there is never any overturned or distorted movement. The starting point of the X axis is adjusted by an X axis optical limit switch (29), which makes precise measurements.

A Y axis step motor (33) is used for Y axis movement. In this system, there is a double shaft structure just like the X axis. The motor is fixed on a Y-axis step motor carrier (32). The connection between the motor and a Y axis buttress shaft (40) is provided by a Y axis coupling (34). The Y axis buttress shaft (40) is fixed with a multiple of Y axis pillow bearings (31 , 41 ). A multiple of Y axis pillow bearings (35, 42) are also fixed on a second Y-axis buttress shaft (44). A Y axis Gt2 gear (54) at the tip of the buttress shaft and a Y axis Gt2 gear (51 ) at the end of the other shaft are connected to each other with a Gt2 belt, and a Y axis Gt2 belt tightener (52) is used for the tensioning of this belt. An electronic microscope camera (45) is mounted on a Y-axis carrier carriage (38). This carriage has a multiple of Y axis shaft locked nuts (39, 43) on it. There is also an optical limit switch (55) on the Y axis.

In the design, the electronic microscope camera (45) provides movement only in the X and Y axes. The detector cartridges placed on the Z axis provide Z movement. For this, the Z-axis carrier platform (17) is designed. On the illuminated surface (21 ) above this platform; in order to provide illumination, plexiglass is used to distribute the light homogeneously in the appearance of a frosted glass. It is designed in such a way that light sources with different wavelengths can be placed under it. A Z axis step motor (80) is mounted on a Z axis motor carrier (81 ) for the movement of the Z axis. The connection of the motor to a Z axis buttress shaft (60) is made with a Z axis coupling (79). A Z axis Gt2 gear (78) is connected to the Z axis buttress shaft (60). The Z axis Gt2 gear (78) connected to the motor end is connected to an opposite Z axis buttress shaft (66) via a Z axis belt tightener (83) with a Gt2 belt. The second Z-axis buttress shaft (66) is fixed by a Z-axis pillow bearing (71 ). Since both Z axis buttress shafts (60, 66) are connected to a single Z axis step motor (80) with Gt2 belt, there is a stable movement in Z axis. A multiple of Z axis locked shaft nut and carriages (59, 72) are used to transfer this movement to the Z axis carrier platform (17). A multiple of Z-axis steel shafts (58, 62, 64, 70) are fixed with a multiple of z-axis shaft fixers (76, 68, 73) to ensure the stability of the Z-axis carrier platform. The Z-axis carrier platform is connected to the Z-axis steel shafts (58, 62, 64, 70) by a multiple of Z-axis shaft bearings (57, 61 , 69, 65). A Z axis optical limit switch (82) is used as the z axis limit switch.

The SMPS feeding unit (75) and the electronic control card are placed in the electronic control circuits chamber (23). In order to prevent vibration, to provide ventilation and natural flowing air, cooling is provided with air channels placed opposite to the covers. The cables to the motors, limit switches and microscopic camera are carried via a cable canal (63).

In addition, under the illuminated surface (21 ), there are blue (450-500 nm wavelength, peak wavelength 450-470 nm) illumination LEDs for LR-115 and white (380-500 wavelength) illumination LEDs for CR-39. Blue light is used to improve readability from the LR-115. Thus, the system can be used for both CR-39 and LR-115 at the same time.

The third unit is the control software. The control software is connected to the control cards via USB. It performs mechanical controls of the reading unit by using the Geode command system used in CNC machines. In addition, the reader microscopic CCD camera is also connected to the computer via USB. The images coming to the computer are processed by the software and reporting data is obtained. GCode is the generic name for the CNC machine control language. CNC Machine is told what to do with Geode commands. GCode commands tell the CNC machine how fast, where, what kind of movement it should do. The CNC milling machine lifts, engraves and cuts the material while executing the Geode command. But a CNC doing 3D Printing creates a shape by knitting the filament while applying the GCode file. Whereas, a laser bums on a material with a Geode file.

Current systems consist of a camera connected to a microscope and a mechanism that enables the movement of detectors under the lens over the microscope. Existing systems allow only one detector type to be read. Only either CR- 39 or LR-115 is used in the system. While their software slides the CR-39 or LR-115 detector under the lens, it also counts the pits present in the image taken on the screen. In this counting process, a detector is counted five times for the circles left unfinished on the screen, and the average of the counting results is taken. In this method, errors may occur during the counting process. In order to minimize these errors, average is taken as a statistical method.

One of the greatest benefits of the invention is that, compared to other existing automatic measurement systems, first of all, the full image of the detector is taken with the image stitching method for once. This full detector image can be stored in the computer and can be called back to the screen at any time. In this way, when a new operation with the detector is required, it is sufficient to simply recall the detector from the archive without the need to read it again.

This is the area within a square mm2 determined by us to be read on the acquired image. In order to determine this area, the readings made during the test studies are used. Since the radon traces remaining in this area are not cut and not displayed in parts, the data read is equal to each other every time. Therefore, the reading and evaluation process gives the same result every time. For this reason, as in other systems, there is no need for a large number of reading operations and taking average values. In addition, the detectors were counted one by one visually during the tests, and these counts were compared with the values given by the system. It was observed that there were errors in counting only the circles that were above the specified limits and only less than half of the circle was within the reading limit. The ratio of these erroneous counts to the total counts is three in ten thousand, and this error rate is negligible and will not affect the total result.

Depending on this image, a complete and error-free measurement can be made, and a detailed report can be generated about the energies, directions, color values, coordinates, and sizes of the traces on the detector with the analytical examinations (shape, length, size, slope, color) made on this image. These features are not available on other systems. Considering the circularity ratio in this reporting, if a trace is fully circular, it should be perceived as a collision of an oncoming particle. If the trace is more elliptical, this indicates that it hit the surface at a certain angle. The software finds and reports the individual values of this data for each trace. Depending on these values, the system leaves the interpretation to the user. Currently, there is no report prepared with this much detail. Based on these reports, it is planned to provide opportunities for different academic studies.

In the current system, the traces on a detector are counted five times under the microscope. This causes a great loss of time. In the system that is the subject of our invention, the same results can always be obtained after an image of the detector is taken once by using the image stitching technique. However, the current image can be counted as many times as desired. Because the image of each detector is stored on the system. In addition, many features of the traces on the detector such as diameters, positions, energies, angles of hitting the detector, circularity rates are automatically reported at the end of the measurement. In addition, the detector screenshot is included in the report as marked.

Edge detection algorithm is used to mark the tracks. After converting the image to black and white, if edge detection algorithms are desired to be used, the most popular of several options is the sobel edge detection filter. The following core matrices (convolution matrices) are used to find vertical, horizontal and diagonal shaped edges. The Sobel operator reveals areal high frequency regions (sharp edges) that correspond to the edges of an image. Theoretically, the operator consists of a 3x3 convolution matrix as shown below. These matrices are arranged separately for the horizontally and vertically visible edges. Matrices can be applied independently of each other to the input image. Thus, the value of the pixel for each direction is measured separately. These values can then be combined with the following formulas to find the absolute value and find the direction (angle) of the diagonal sides. Pixel absolute value can be calculated as follows.

For faster calculation of pixel value, the following formula can be used.

|G| — |Gx| + |Gy|

The direction angle of the resulting edge (relative to the pixel grid) is found by looking at its values in the x and y directions as follows.

Gx 0 = arctan (— )

In this case, 0 degrees will show horizontal lines and 90 degrees will show vertical lines. Oblique lines will also form other angles. Here, in the zero-degree line, the lower part shows the transition from black to the upper part white. In the horizontal line at 180 degrees, which is similar to 0 degrees, the upper part will show a transition from the black region to the lower part white region. The angles are measured counterclockwise. Here, if the Gx convolution matrix is used alone, it will find the color change horizontally, so we see the resulting lines vertically. Similarly, if the Gy convolution matrix is used alone, the resulting lines will be horizontal since it will show the color transition (from black to white) from bottom to top. If we want to see the lines on the picture in their natural positions instead of seeing them horizontally or vertically, we can add both convolution matrices with the calculation given above. Similarly, we can use the square root formula given above. If we want to reveal lines at certain angles on the picture, we can determine these lines by calculating with the angle formula given. Below, if we apply the edge detection algorithm to a 9-pixel image, which corresponds to a 3x3 pixel, on the image we have obtained;

| Gx\ = | - Pl + P3 - 2P4 + 2P6 - P7 + P9|

|Gy| = |P1 + 2P2 + P3 - P7 - 2P8 - P9\ is obtained. The value obtained at the end of the calculation is written to the pixel in the middle of the matrix, and these operations are repeated on the entire image. As a result, the edges are highlighted on the new image obtained.

The steps showing the method of the system subject to the invention are respectively given below.

- Starting the system,

- Performing mechanical control (checking for errors in the mechanical units of the device),

- Stopping the system if there is an error information,

- Opening a new project file on the database if there is no error information,

- Taking 128 images, each with a resolution of 320x200 dpi, measuring the image focusing quality in each shot, re-shooting if there are errors,

- Applying the image stitching algorithm to the images and obtaining a single high-resolution image (image stitching),

- Highlighting edges in an image by replacing each pixel with the neighborhood variance (variance filter),

- Converting the obtained image into 256 grayscale image, taking the luminance value of each pixel for this, summing the red 30%, green 59%, blue 11 % values, creating a new image and saving it,

- Filling holes in the background (fill holes filter),

- Automatic separation of touching particles (wathershed filter),

- Generating the final eroded points of the Euclidean distance map from a binary image (ultimate points filter), - Obtaining binary images from 8 and 16 bit images using global thresholding methods (application of threshold filter according to Li Dark method),

- Converting the image to black and white based on a threshold calculated by analyzing the histogram (convert to mask),

- Adding pixels to the edges of black objects (dilate filter),

- Blurring the active image or selection (replacing each pixel by the average of its 3x3 neighborhood) (smooth filter),

- Removal of smooth continuous backgrounds (subtract background filter),

- Determining the maximum in the image and marking the binary particle of the same size as the maximum (find maxima filter),

- Adjusting the actual size of the pixels (1 pixel = 0.392526299262051 micrometer),

- Marking the region to be read on the picture,

- Performing mathematical analysis of particles with a size of 2.5 pixels and above and removing other particles from the picture,

- Preparing the preliminary excel file for the report (the file contains data such as x position, y position, average value, particle position, angle, circularity ratio, brightness, stability),

- Giving the sequence number by placing a mark around the particles on the original picture combined using the position and size information,

- Preparation of final report in PDF format using available information.