RU198442U1 - A device for storing objects in a low-air atmosphere - Google Patents

Abstract

The claimed utility model relates to devices for maintaining the specified parameters of the air environment within a certain volume, and is designed to provide a specified value of the volumetric activity of radon in the air inside the boxes used for storing objects, in particular integral passive detectors for recording ionizing radiation, or performing operations with detectors or other objects in which the radon content should be equal to or less than the specified value. The scope of application of the device is dosimetry and radiometry of ionizing radiation, in particular, radiation and hygienic examinations of residential, public and industrial premises for the content of radon in premises, monitoring compliance with radiation safety requirements at workplaces, conducting research and applied work, works on radon rehabilitation of buildings teaching pupils and students. The claimed device for storing objects in a low-radon atmosphere includes a housing with a sealed chamber for placing objects in the inner volume of the housing and a cell with activated carbon inside the sealed chamber, and inside the sealed chamber there is also an air pressure sensor connected to the power supply circuit inside or outside the casing a vacuum pump, which is cyclically turned on to pump out air upon a sensor signal that the set pressure in the internal volume of the housing is exceeded and is turned off when the set pressure in the internal volume of the housing is reached, while the recommended value of the set pressure is 5-6 kPa, which ensures the maintenance of the average value the volumetric activity of radon inside the box body at a level below its value in the atmospheric air. The technical result consists in ensuring the minimum possible value of the average volumetric activity of radon throughout the entire period of storage of the object in the box, while the air pumping system, both after opening the cover of the airlock and in the intervals between openings, makes it possible to reduce the duration of increased radon contents in the internal volume box and simplify the operation of the box, since due to this, the time intervals between replacements of activated carbon are increased several times. 9 p.p. f-ly, 1 dwg.

Description

The utility model relates to devices for storing objects that are not sensitive to air pressure and its composition and the composition of another (non-radioactive) gas inside the device, but having increased requirements for ionizing radiation.

The device is used to maintain the specified parameters of the air environment within a certain volume, in particular to provide a given radon content in the air inside the boxes used to store integral passive detectors for recording ionizing radiation or performing operations with detectors or other objects in which the radon content should be equal or less than the set value. The scope of application is dosimetry and radiometry of ionizing radiation, in particular radiation-hygienic examinations of residential, public and industrial premises for the content of radon in rooms, monitoring compliance with radiation safety requirements at workplaces, conducting research and applied work, works on radon rehabilitation of buildings, Learning for pupils and students.

It is known that one of the main reasons for the distortion of the results of mass measurements of volumetric activity (OA) of radon using integrated track exposure meters is the improper storage of exposure meters during their collection after exposure until they are sent to the laboratory for processing (see Marenny AM Methodological aspects of measuring average volumetric activity radon in the premises by the integral track method // ANRI, No. 4, 2012, p. 13-19). This is due to the fact that the collected exposure meters during this period are often stored in random rooms with an uncontrolled increased content of radon in the air, which, in turn, leads to an overestimation of the results of measuring the volumetric activity of radon in the examined objects after laboratory processing of the exposure meters.

A similar problem arises with the long-term storage (months, years) of track detectors in laboratories that prepare exposure meters for measurements and process them after the measurements are completed. Therefore, the creation of equipment for storing track detectors and their equipped exposure meters in a controlled atmosphere with a low radon content is an urgent task.

Currently, there are a number of methods and devices for reducing or maintaining at a given level of OA radon in the air of various objects. They are based, as a rule, on preventing radon from entering the internal volume of the object, or on the absorption of radon in the air inside the object. Most often, measures to prevent the ingress of radon inside an object are applied to buildings for various purposes, i.e. in cases when radon enters the building mainly from the underlying soils and soils (Marenny A.M., Tsapalov A.A., Miklyaev P.S., Petrova TB. Patterns of formation of the radon field in the geological environment // Publisher " Feather ", M., 2016, 394 pp.). For this, various engineering and construction measures are carried out, which are to isolate the ground floor from basements or open ground and / or reduce the concentration of radon in the underground of the first floor (SP 321.1325800.2017. Code of practice. Residential and public buildings. Design rules for anti-radar protection ").

At facilities in which the predominant intake of radon into the air of internal volumes comes from building envelopes made of materials with a high content of radium-226 (SP 321.1325800.2017. Code of practice. Residential and public buildings. Rules for the design of anti-radon protection "), measures are being taken to isolating the surfaces of building envelopes from air of internal volumes (multilayer oil painting, gluing with films with low permeability, etc.).

There are facilities for which preventing the entry of radon into internal volumes is not efficient enough, impossible, or economically impractical. In these cases, natural or forced ventilation is used as the main or additional measure to remove radon from the air. In this case, air with a high radon content is replaced with air with a lower radon content or air free from radon, and the air exchange rate is calculated based on the required radon content reduction ratio (SP 321.1325800.2017. Code of practice. Residential and public buildings. Design rules for anti-radon protection " )

Other methods and means of removing radon from the air are known. For example, there is a method for reducing the equivalent equilibrium volumetric activity of radon isotopes in a room by removing short-lived daughter products of radioactive decay from the air by creating an electrostatic field using a generator with cold electron emission (Patent RU 2101790 C1. A method for reducing the equivalent equilibrium volumetric activity of radon isotopes in indoors.).

To solve the same problem, a gas hydration unit is designed that works according to an open, direct-flow circuit, which ensures the continuous supply of new portions of air contaminated with radon and, as a result, the continuous capture and immobilization of radon at any concentration in air (Patent RU 135938 U1. Installation for gas hydrate purification of air from radon gas.).

A number of methods and devices for removing radon from air are based on the active absorption of radon in activated carbon (RU 2400675 C2, publ. 06/27/2010, RU 2601737 C1, publ. 10.11.2016 g).

Basically, the considered methods and devices are designed to reduce the volumetric activity (OA) of radon in the air of buildings and structures for public or industrial purposes under various restrictive conditions. They are intended, as a rule, for air purification from radon in rooms with a volume of tens or more cubic meters. Their work should not worsen the living conditions of people in the premises, in particular, change the composition, pressure, temperature and humidity. In view of this, the complexity and cost of both the devices themselves and their operation are important, but not the main indicators.

However, the problem solved in this application is to ensure that the device inside the device automatically maintains an optimally low radon content, which is practically not sufficient for reliably fixed radiation exposure on track detectors or other objects in the device. The device is designed to store objects that are not sensitive to the composition and pressure of air or other (non-radioactive) gas inside the device. Obviously, the solution to the problem of reducing the radon content inside the device does not have to be technically complicated and expensive.

Researchers have long been faced with the need to create an airtight box, which makes it possible to automatically maintain a given composition in the chamber of the atmosphere for carrying out work with oxygen, moisture, and other components that are sensitive.

The prior art also knows the solution of a sealed box for experiments in an inert gas atmosphere. This device is for a different purpose than the declared one, but having technical characteristics similar to the declared one:

The proposed device (patent for utility model RU 65217, published July 27, 2007) is a sealed box, which, with the help of reducers and valves for precise pressure control, provides the ability to maintain a specified composition of the gas medium inside the box in automatic mode with fairly high accuracy.

The use of a modern elemental base, in particular, a touch panel for control of pumping systems, automatic filling and regeneration, allows you to fully automate the process of working with the box according to a given program.

As can be seen from the description of the specified device, it is intended to maintain a constant gas composition of the gas in the internal volume of the device (apparently, at normal atmospheric pressure). As a device that provides directional gas movement throughout the chamber volume, gas purification, and maintaining a constant predetermined gas composition, a certain device for gas carrier cleaning CF-10 from LECO, USA can be used. Using the CF-10 device, which has two stages of gas purification (cold and hot), it is possible to purify both inert gases and oxygen. The device is used as reagents, depending on the gas used: metallic copper, zirconium, copper oxide, activated carbon, etc. There is a gateway for placing items in an airtight box.

Thus, in the known technical solution, the common with the proposed solution is the sealing of the internal volume of the body, the use of activated carbon to absorb some unwanted impurities to the main components of the gas mixture, the presence of a sealed lid for placing objects in the internal volume of the box. However, this box with considerable complexity does not ensure the achievement of the goals indicated in the description of the proposed utility model.

The closest of the existing prior art to the claimed utility model is described in the thesis on Environmental Monitoring of the Radioactive Situation in the city of Krasnokamensk (the work was published on the website https://www.bibliofond.ru/downIoad_list.aspx?id=517254 and was viewed on 18.10. 2019) a “radon-free” box for storing coal samplers designed to measure the volumetric activity of radon in air. The device is a sealed rectangular chamber made of transparent plexiglass with two rubber gloves, hermetically closing the holes in the housing.

With the gloves removed, the holes are gateways for placing and retrieving objects stored inside the box. In the tense position, gloves are used to manipulate objects inside the box. To reduce OA of radon in the air of the internal volume of the box, open cuvettes with activated charcoal placed inside it are used, in which passive absorption of radon occurs. To eliminate the difference in barometric air pressure between the internal volume of the box and the external atmosphere, a flowing sorption column with activated carbon is used.

The disadvantages of the considered device are:

- limited speed of passive absorption of radon from the air,

- the need to control the decrease in the absorption capacity of the sorbent (activated carbon) and to carry out its replacement or regeneration,

- restrictions on the use of the box associated with the contamination of the sorbing surface of activated carbon granules in a dusty or having an admixture of other gases atmosphere.

These shortcomings are aggravated by frequent (several times a day) opening the lock chamber, the process of cleaning the air to the desired condition after each opening of the lock chamber is quite inert, it requires from one to several hours.

The purpose of this application for a utility model is to develop a box that is free from the above disadvantages of the analog without a significant deterioration in its economic performance.

The problem to be solved is to ensure the lowest possible value of the average volumetric activity of radon throughout the entire period of storage of the object in the device while reducing maintenance costs.

The problem is solved due to the fact that the device for storing objects in a low-radial atmosphere, including a housing with a sealed lid and a sealed chamber for placing objects in the internal volume of the sealed chamber through a hermetically sealed lid and activated carbon cells inside the sealed chamber, according to the proposed technical solution, has a vacuum pump, and the case has a technical compartment, in which the control unit and the power supply unit with a battery are placed, a (electronic) pressure sensor is mounted inside the sealed chamber (for measuring air pressure in the internal volume of the sealed chamber) and at the same time a sealed chamber (internal volume chamber) is connected to the vacuum pump through the vacuum valve of the nozzle to ensure that the pump can maintain the pressure (vacuum) parameters set by the control unit.

In this case, the sealed chamber may be equipped with a vacuum check valve, which is configured to equalize the pressures inside the sealed chamber and on the outside of the device before opening the sealed cover.

As the sealed cover of the sealed chamber, any removable wall of the housing or its cover made with a vacuum seal between it and the housing of the device can be used.

The control unit can be made manual or automatic.

The device may be equipped with one or more additional pressure sensors.

In this case, the vacuum pump can be placed inside the technical compartment of the housing.

Or a vacuum pump can be placed outside the housing.

The device may be equipped with an additional one or more vacuum pumps.

The power supply can be made universal, providing the ability to connect the device to an external electrical network and long-term work in standalone mode using a battery.

The housing may be made in the form of a parallelepiped, hemisphere or pipe.

The technical result provided by the given set of features is to provide the minimum possible value of the average volumetric activity of radon throughout the entire storage period of the object in the device, regardless of external conditions, including the stability of power supply. At the same time, pumping out the air, both after opening the sealed cover of the sealed chamber and between the openings, makes it possible to reduce the duration of increased radon contents in the internal volume of the device and to simplify the operation of the device, since, due to this, the time intervals between exchanges of activated carbon are increased several times .

In contrast to the analogue, the goal is achieved in that the proposed device implements two approaches to reduce the radon content in the internal atmosphere of a sealed chamber:

- a rapid decrease in OA of radon after sealing by quickly reducing the air pressure in the internal volume, during which the OA of radon also decreases by a factor of one,

- passive sorption of radon by activated carbon in the intervals between depressurization of the box, which leads to a smooth further decrease in OA of radon in the internal volume of the box.

To implement this approach, the claimed device for reducing the radon content uses, in addition to ditches with activated carbon, a vacuum pump pumping air from the sealed chamber to a set pressure at which the proportionally decreasing radon content reaches a predetermined value.

The essence of the claimed device is illustrated in Fig. 1, schematically representing the main elements.

This illustration does not cover and, moreover, does not limit the scope of claims for this solution, but only illustrates a particular case of the device.

The device is a sealed chamber 1 made of transparent plexiglass with a hermetically sealed inlet (gateway) - a sealed cover 2 and a technical compartment 10. Inside the chamber 1 body there are cuvettes 3 with activated carbon and an electronic pressure sensor 4 for measuring air pressure inside the chamber is mounted. In the technical compartment are the control unit 9, the vacuum pump 5 and the battery 8. The internal volume of the sealed chamber and the vacuum pump are connected by a vacuum valve to the nozzle 6. There is a vacuum check valve 7 on the body to equalize the pressures inside the sealed chamber and outside the housing before opening the sealed cover 2 The housing as a whole can be airtight, and can only have a sealed chamber with a sealed cover, and the technical compartment is not sealed.

The control unit of the device 9 allows you to:

1. Turn on (turn off) the device;

2. Set the device operation mode (manual, automatic);

3. Set the required values of pressure (vacuum) inside the chamber;

4. On the display unit, constantly display the current pressure inside the chamber;

5. Display the battery status and charge it automatically when discharged.

The presence of a power source (battery) allows the device to work in standalone mode and provide long-term preservation of pressure (vacuum) parameters without connecting to the mains, which is extremely important outside the laboratory environment.

Briefly, the method of storing measuring equipment before and after measurements up to sending it to the laboratory for processing the results can also be described as follows: the equipment is placed in a sealed enclosure with a lock chamber for placing objects in the internal volume of the enclosure, containing inside the cuvette with activated charcoal, a pressure sensor air connected to the power supply circuit of the vacuum pump located outside the lock chamber, which is cyclically turned on to pump air by the signal of the sensor when the set pressure value is exceeded and turns off when the set pressure value in the lock chamber is reached, while the recommended set pressure value is 5-6 kPA, which ensures the maintenance of the average volumetric activity of radon inside the box body at a level below its value in atmospheric air.

The device operates as follows. Inoperative, i.e. in the absence of stored objects inside the sealed chamber 1, the vacuum check valve 7 is open, on the control unit the toggle switch “on” is in the “off2” position, the power cord is disconnected from the mains. Bringing the camera into working condition is carried out in the following order: open the lid 2, place the storage objects inside the chamber 1, close the airtight lid 2, close the check valve 7, connect the power cord to the power supply, set the device operation mode to “manual” on the control unit, the “on” toggle switch is set to the “on” position, the required pressure (vacuum) values are set inside the chamber (displayed on the indicator), the “device operation mode” toggle switch is set to the “automatic” position. Then everything happens automatically: the vacuum pump is turned on and it works until the pressure inside the sealed chamber reaches the set values. In the process of pumping air out of the chamber and after it, passive absorption of residual radon in the air of the sealed chamber with activated carbon located in cuvettes 3 occurs, which, together with pumping air to a predetermined value, allows to achieve the lowest possible average radon content inside chamber 1 during the storage period stored object inside the camera. At the same time, the disadvantages of the analogue - boxing with activated carbon only, noted above, can be largely leveled, because activated carbon "works" almost always with a relatively low content of radon in the air.

To retrieve stored objects from the camera, you must turn off the device. To do this: on the control unit, the device’s operating mode is switched to the “manual” position, the “on” toggle switch is put into the “off” position, the check valve 7 is opened to equalize the pressures inside and outside the device case, loosening the locking screw, open the sealed cover 2.

It is proposed to choose the optimal preset air pressure in the sealed chamber based on the following considerations. As a value of a given OA of radon inside an airtight chamber, it is advisable to choose the average RF volumetric activity of radon in rooms 60 Bq / m ³ . Moreover, in more than 95% of the premises, the average OA of radon does not exceed 1000 Bq / m ³ . The ratio of the two given values is 17. Thus, in order to achieve the proposed target value of OA of radon inside the box, in almost the worst situation, it is necessary to pump out air to a residual pressure of about 5-6 kPa (40-45 mm Hg). If we take into account that in most rooms the OA of radon does not exceed 200 Bq / m ³ , then the OA of radon inside the box at the indicated air pumping ratio does not exceed 12 Bq / m ³ , i.e. will be at the level of radon in atmospheric air. Recall that the above estimates characterize the situation immediately after air evacuation. However, in the interval between air pumpings, passive sorption of radon by activated carbon occurs, so that the real average radon OA values will be even lower, up to 2-5 Bq / m ³ .

An analysis of the proposals on the market of vacuum pumps shows that, in this case, pumps for pumping air into the produced ones, for example, for use in medical equipment, air sampling devices, etc., can be used as such pumps. For example, in the class of inexpensive (500-1000 rubles) models, pumps with a residual pressure of 5-10 kPa (40-80 mm Hg) with a productivity of 5-10 l / min are available. The cost of pressure controllers in the right range is 300-700 rubles, the battery - 500-650 rubles. Thus, the cost of additional boxing equipment is economically acceptable.

The optimum performance of the vacuum pump (or pump) can be determined from the following considerations. It is known that the duration t of evacuation of volume V (l) by a pump with a capacity of S ((l / min) from the initial P ₁ (kPa) to the final pressure P ₂ (kPa) is determined by the formula (“Calculation of the evacuation time of the capacity” _ Internet resource https: / /www.ampika.ru/online-kalkulyatory-dlya-nasosov/raschet-vremeni-vakuumirovaniya-emkosti-nasosom/):

where F is the correction factor, the value of which depends on the final pressure in the tank P2.

With regard to the device under consideration, the values included in formula (1) should be interpreted as follows: V is the capacity of the box chamber, S≡v is the capacity of the vacuum pump (pump), P ₁ and P ₂ are the standard air pressure and the set pressure inside the box. For the justified value of the set pressure at the level of 5-6 kPa, the value of F is 1.75.

Suppose that a sealed chamber is opened N times during the day. Then the total pumping time is N⋅t minutes. About the same amount of time will take the placement-extraction of the storage object. In total, the total duration of time intervals during which the volumetric activity of radon inside the chamber will exceed a predetermined value is, according to the maximum estimate, 2N⋅t minutes per day. Assuming that it is perfectly acceptable if the total duration of such deviations of the storage conditions of the objects is 60 minutes per day, we will get 2N⋅t = 60, from where:

From (1) and (2) we obtain:

where from:

Substituting in (4) the numerical values of the quantities, we obtain:

From the ratio it follows that the optimal performance of the vacuum pump (pump) under given conditions varies in the range from ν⋅ = 0.18F to ν⋅ = V with the estimated number of openings-closures of the sealed chamber per day from 1 to 6. Note that one of The assumptions made during these evaluations were that when vacuuming the OA of radon in air should decrease from 1000 to 60 Bq / m ³ . However, this is a rare situation, in most cases, the initial OA of radon is not higher than 200 Bq / m ³ , i.e. the OA ratio of radon before and after pumping, as well as the pressure ratio, is about 3. Substituting this value in (4), we obtain:

Those. the optimal performance of the pumping device (vacuum pump, pump) in these cases may be less than three times.

The housing of the device can be made in various geometric shapes. In determining the shape and size of the box, in addition to its main functional purpose, it is necessary to take into account the atmospheric pressure on its structural elements. This usually comes down to the selection of material for the camera body.

The manufactured two copies of the device (box) were tested in operation for 30 days with an average volumetric activity of radon in the room of 27 Bq / m ³ . Boxing is made in the form of a parallelepiped with a volume of 12.5 liters. The role of the gateway is performed by a removable top cover with a diameter of 15 cm. Pump performance - 10 l / min. During the period, 5-8 manipulations with the top cover per working day were performed. During the entire testing period of the box, the average volumetric activity inside the box was measured using the integral method using a REI-4 radon exposure meter. The obtained value is less than 3 Bq / m.

For comparison, the same box was tested under the conditions of the prototype, that is, in a completely identical setting, but without air evacuation after each manipulation with the top cover, using only activated carbon to reduce the radon content. The average volumetric activity of radon was 17 Bq / m ³ .

Thus, the proposed technical solution ensures the achievement of the goal. The proposed design of the box provides the lowest possible value of the average OA of radon over the entire period of storage of the object in the device, regardless of environmental pollution and the presence of a stable power supply.

At the same time, the applied two-stage reduction in the radon content in the sealed chamber, both after opening the sealed chamber cover and in the intervals between openings, allows one to reduce the duration of increased radon OA values in the internal volume of the sealed chamber and simplify the operation of the device, since, due to this, several times the time intervals between checks and replacements of activated carbon are increased.

Claims (10)

1. A device for storing objects in a low-radion atmosphere, including a housing with a sealed cover and a sealed chamber for placing objects in the internal volume of the sealed chamber through a hermetically sealed lid and activated carbon cells inside the sealed chamber, characterized in that the device is equipped with a vacuum pump, and the housing has a technical compartment in which the control unit and the power supply unit with the battery are located, a pressure sensor is mounted inside the sealed chamber, and the sealed chamber is connected to the vacuum pump through the nozzle's vacuum valve, ensuring that the pump can maintain the pressure parameters set by the control unit. 2. The device according to claim 1, characterized in that the sealed chamber is equipped with a vacuum check valve, which is configured to equalize the pressures inside the sealed chamber and outside the device body before opening the sealed cover. 3. The device according to claim 1, characterized in that any removable wall of the housing or its cover, made with a vacuum seal between it and the housing of the device, is used as the airtight cover of the lock chamber. 4. The device according to p. 1, characterized in that the control unit is made manual or automatic. 5. The device according to claim 1, characterized in that it is equipped with one or more additional pressure sensors. 6. The device according to claim 1, characterized in that the vacuum pump is located inside the technical compartment of the housing. 7. The device according to claim 1, characterized in that the vacuum pump is located outside the housing. 8. The device according to p. 1, characterized in that it is equipped with an additional one or more vacuum pumps. 9. The device according to p. 1, characterized in that the power supply is universal, providing the ability to connect the device to an external electrical network and long-term battery life using a battery. 10. The device according to p. 1, characterized in that the casing is made in the form of a parallelepiped, hemisphere or pipe.

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