PL237746B1 - Method of determining the activity of radioactive Pb-210 lead on filter inserts, in particular in gas filter-separator batteries and the arrangement of devices for determining the activity of radioactive Pb-210 lead on the inserts - Google Patents

Description

The subject of the invention is a method for determining the radioactive activity of lead Pb-210 on filter cartridges, especially in gas filter separator batteries, and a system of devices for determining the radioactive activity of lead Pb-210 on filter cartridges, especially in filter separator batteries, applicable, inter alia, in the gas transmission and distribution industry. natural gas.

In the publication of the International Atomic Energy Agency entitled: "Radiation protection and the management of radioactive waste in the oil and gas industry", Safety Reports Series No. 34, 2003 and in the guidelines of the International Association of Oil and Natural Gas Producers entitled: "Guidelines for the management of Naturally Occurring Radioactive Material (NORM) in the oil & gas industry", Report No. 412, 2008, the current state of knowledge on the radiological hazard resulting from the presence of natural radioactive elements in the mining industry is presented. In the case of natural gas transmission networks, the problem of radioactivity is related to the presence of Rn-222 radon and its decay products. The radon concentration in the natural gas transported in the pipeline fluctuates over a wide range from several Bq / m ³ to several thousand Bq / m3. Radon itself, without being a threat, is only the primary cause of a radiological threat in the gas transmission infrastructure, as its presence in the network causes the formation of radioactive dust in the elements of the transmission network. The formation of these dusts is related to the gradual decay of radon during its transport with gas. The decay produces short-lived products and the long-lived Pb-210 lead with a half-life of 22.3 years. Due to their chemical properties, radon decay products are easily adsorbed on various types of surfaces, e.g. aerosols. Consequently, this leads to the creation of the so-called a thin radioactive film on the inner surfaces of components in contact with the transported gas, and for accumulation in filters and filter separators of dust containing radioactive lead Pb-210. In accordance with the Atomic Law (Journal of Laws 2001 No. 3 item 18) and the Regulation of the Council of Ministers of December 14, 2015 on radioactive waste and spent nuclear fuel (Journal of Laws of 2015, item 2267), Pb-210 dust concentrations above 10 kBq / kg should be treated as low-level radioactive waste.

Due to the properties of the emitted low-energy gamma radiation, the lead accumulated in the filters is not visible for gamma radiation dosimeters, which work on the basis of a sodium iodide scintillation crystal or Geiger counter, but it is very clearly visible in the results of laboratory measurements performed with the use of spectrometry gamma, using the Pb-210 emission line with gamma radiation energy - 46.5 keV. The method of gamma spectrometry, commonly known and used, requires collecting a dust sample from the filter, which involves taking the device out of use, opening and replacing the filter cartridges. For example, the method of Pb-210 lead content determination using gamma spectrometry was described in the scientific publication by H. Gaggeler et al., Entitled: "Determination of Pb-210 in lake sediments and in air samples by direct gamma-ray measurement", Earth and Planetary Science Letters 33 (1), 1976, or in the publication by C. Dovlete, "Gamma spectrometric measurement of Pb-210 in environmental samples", Environment International 22 (1), 1996).

From the German patent application DE3727903A1 a method of measuring the concentration of aerosols in a gaseous medium is known, characterized in that the concentration measurement is based on the measurement of lead Pb-211, i.e. the short-lived product of radon 219 decay. In this method, the gaseous medium passes through the first chamber equipped with into a radioactive source with known activity of the actinium 227 isotope, which is the source of the Rn-219 radon isotope, which decays into the Pb-211 isotope. This, in turn, is adsorbed on the aerosols in the test gas, which is then passed through a filter in the second chamber. Based on the measurement of the filter activity by a detector placed in its vicinity, the concentration of aerosols in the gaseous medium is determined. The detector measurements are recorded with a recording device.

The method of radon measurement with the use of a scintillation chamber described in the article by H.F. Lucas Fri: "Improved Low-Level Alpha-Scintillation Counter for Radon", Review of Scientific Instruments 28 (9), 1957. This chamber, the so-called the Lucas chamber is usually a cylindrical container covered on the inside with a thin layer of ZnS (Ag) scintillation crystal, the bottom of which is transmissive to scintillation light incident on a photomultiplier tube connected to the chamber. The measurement of the radon concentration consists in filling the chamber with the tested gas and counting the number of pulses per unit

PL 237 746 Β1 time after the formation of the radioactive equilibrium of radon with the derivatives formed in the chamber. A particles falling on the walls covered with a scintillator cause scintillation - short flashes of light, which are converted into electrical pulses by means of a photomultiplier, and which, after amplification, are counted by a pulse counter. The Lucas chamber allows direct measurement of radon in gas transported through the gas pipeline, and an example of its use for the measurement of radon in gas is described in the publication by M.E. Kitto et al. Fri: "Radon measurement ofnatural gas using alpha scintillation cells", Journal of Environmental Radioactivity 138, 2014.

The aim of the invention is to develop a method and a system of devices that allow to measure the activity of lead Pb-210 in the dust accumulated in the filtering device during its operation, without the need to replace the filter cartridge, and thus - to select places where there is a potential radiological hazard associated with increased lead content of Pb-210 in the dust, as well as allowing the classification of dusts in terms of their radioactivity in accordance with applicable law - even before starting the replacement of filter cartridges.

The essence of the method of determining the radioactive activity of lead Pb-210 on filter cartridges, especially in gas filter separator batteries, consists in the fact that known measurement methods are used to measure the average radon concentration of Rn-222 CRn in the gas flowing through the filter separator, as well as the gas volume flow Q and the average content of solid particles kw in the gas, while the activity of lead Pb-210 Apb in the dust collected on the filter element is calculated from the dependence:

λ h LA) 1 ^ = ^ / ^ - (^^^ - 1) -where:

Apb - activity of Pb-210 lead in dust,

Apb - Pb-210 lead decay constant,

CRn - Rn-222 radon concentration,

Aro - radon decay constant Rn-222, k - solids content in the gas, I - distance between the analyzed gas cleaning system and the system preceding it, A - pipeline cross-sectional area, Q - average gas volume flow.

It is preferred that the measurement of the average radon concentration Rn-222 CRn is carried out with a scintillation chamber, which is a Lucas chamber equipped with a measuring device, and it is also preferred that the measurement of the average concentration of radon Rn-222 CRn in the gas is performed at least once every time. 24 hours for the entire period of operation of the filter cartridge.

It is also advantageous if the gas volume flow Q is measured with a flow meter belonging to the gas pipeline infrastructure in the filter separator station.

Moreover, it is preferred that the measurement of the average solids content of the gas is carried out at least once a day for the entire lifetime of the filter cartridge by means of a filtering and flow meter.

The essence of the system of devices for determining the radioactive activity of lead Pb-210 on filter cartridges, especially in filter separator batteries, is that it has two measuring circuits, i.e. a solid fraction measuring circuit connected in parallel to the gas pipeline, including a flow meter and a filtering and measuring device, connected with each other by means of hydraulic lines in a series manner in any order, and also led out from the gas pipeline or from the solid fraction measuring circuit and having at the end discharge to the atmosphere, the Rn-222 radon concentration measurement circuit, containing at least one pressure reducer arranged staggered, gas tank, control manometer, inlet shut-off valve and a scintillation chamber equipped with a measuring device, connected to each other by means of hydraulic lines.

It is advantageous if the solid fraction measuring circuit is connected to the gas pipeline by shut-off valves: the supply valve and the discharge valve, and that the output of the Rn-222 radon concentration measuring circuit from the solid fraction measuring circuit is realized through the first three-way valve.

PL 237 746 Β1

It is advantageous if the discharge of the Rn222 radon concentration measuring circuit to the atmosphere from the solid fraction measuring circuit is effected through an outlet shut-off valve and a throttle.

It is also advantageous if the inlet shut-off valve is a three-way valve to which a pressurized nitrogen reservoir is additionally connected by means of a hydraulic line.

Moreover, it is advantageous if the device system additionally comprises a recording, control and calculation module, equipped with a data input panel and a data transmission system, connected by signal cables or wirelessly to a measuring device, a flow meter, a filtering and measuring device and a flow meter in the filter separator station, as well as when the recording, control and computing module is connected via signal lines or wirelessly to the supply and discharge valves, the first three-way valve, the inlet shut-off valve, the outlet shut-off valve and pressure regulators, and a control manometer and a throttle, which have an automatic control mechanism.

The subject of the invention has been presented in an exemplary embodiment in a schematic drawing showing schematically the system of devices for measuring the radioactive activity of Pb-210 lead on filter cartridges in natural gas filter separator batteries.

An example of the application of the method according to the invention for the determination of the activity of lead Pb-210 on sections of two gas pipelines is presented below.

Marking 1. The test was performed on a gas pipeline node with a diameter of d = 700 [mm] with filtration systems. The distance of the gas purification system upstream is 1 = 150 [km]. The average stream of flowing gas was measured with the use of flow meters belonging to the node infrastructure and was 0 = 4.2: 5.6 [m3 / s]. The content of the solid fraction with a size greater than 5 µm was measured by measuring the weight gain of a filter made in the form of a sinter through which gas samples with a volume of min. 12 [m ³ ] and amounts to k = 0.28-0.45 [mg / m ³ ]. Moreover, by means of a scintillation chamber 14, the so-called in the Lucas chamber, equipped with a measuring device 17, which is a photomultiplier with a pulse counter, the average radon concentration Rn-222 in the gas was determined, which is CRn = 400 [Bq / m ³ ].

Then, the Apb activity of lead Pb-210 in the dust on the filter cartridge was calculated using the relationship _{A = c} -n.ł where:

Apb - activity of Pb-210 lead in dust [Bq / kg],

Apb = [1 / s] - Pb-210 lead decay constant,

CRn - radon concentration Rn-222 [Bq / m3],

Aro = [1 / s] - radon decay constant Rn-222, k - solids content in the gas [kg / m3], I - distance between the analyzed gas cleaning system and the system preceding it [m], A - gas pipeline cross-sectional area [ m ² ],

Q - average gas flow rate [m ³ / s].

The calculated activity of lead Pb-210 in the dust on the filter cartridge is Apb = 12.3-14.8 [kBq / kg] and corresponds to the activity of lead Pb-210 measured by gamma spectrometry directly on the filter cartridges, which is Apb = 12.8 ± 1.3 [kBq / kg],

Marking 2. The test was performed on a gas pipeline node with a diameter of d = 700 [mm] with filtration systems. The distance of the gas purification system upstream is 1 = 180 [km]. The average stream of flowing gas was measured with the use of flow meters belonging to the node infrastructure and was 0 = 5: 6 = 9.7 [m ³ / s]. The content of the solid fraction with a size greater than 5 µm was measured by measuring the weight gain of a filter made in the form of a sinter through which gas samples with a volume of min. 12 [m ³ ] and amounts to k = 0.20-0.30 [mg / m ³ ]. Moreover, by means of a scintillation chamber 14, the so-called in the Lucas chamber, equipped with a measuring device 17, which is a photomultiplier with a pulse counter, the average radon concentration Rn-222 in the gas was tested, which is CRn = 52 [Bq / m ³ ].

The calculated activity of lead Pb-210 in the dust on the filter cartridge is Apb = 1.84-2.16 [kBq / kg] and corresponds to the activity of lead Pb-210 measured by gamma spectrometry directly on the filter cartridges, which is Apb = 2.07 ± 0.2 [kBq / kg],

PL 237 746 Β1

The results of the determinations and the data for both determinations are presented in the table below

Data: Designation 1 Designation 2 Gas pipeline diameter [mm] 700 700 Length of the gas pipeline [km] 150 180 Stream [m ³ / s] 4.2-5.6 5.6-9.7 Solid fraction [mg / m ³ ] 0.28 - 0.45 0.20 - 0.30 The average concentration of Rn-222 [Bq / m3] 400 52 Pb-210 activity [kBq / kg] in situ method 12.3- 14.8 1.84-2.16 Pb-210 activity [kBq / kg] by gamma spect. 12.8 ± 1.3 2.07 ± 0.20

The system of devices for measuring the radioactive activity of lead Pb-210 on the filter cartridges in the natural gas filter separator batteries in the embodiment (Fig. 2) is connected in parallel to the gas pipeline 1 in front of the filter separator station 2 through two cut-off valves: the inlet valve 3 and the discharge valve 4 and includes two circuits: solid fraction measurement circuit and Rn-222 radon concentration measurement circuit, as well as a recording, control and calculation module 5. The inlet valve 3 is connected to the outlet valve 5 successively through the controlled first three-way valve 6, flow meter 7 and a filtering and measuring device 8 and is a closed solid fraction measurement circuit. The measuring circuit for the radon concentration Rn-222 is connected to the first three-way valve 6 and is constituted by the first pressure reducer 9, connected to the tank 10 equipped with a manometer, with a capacity of 2.5 l and a maximum working pressure of 30 bar. The tank 10 outlet is connected to the second pressure reducer 11 and the control manometer 12, and further to the three-way shut-off valve 13 connected to the entrance to the scintillation chamber 14, which is the so-called Lucas chamber - model PYLON 300A. The output of the scintillation chamber 14 is connected to the atmosphere through a shut-off valve 15 and a throttle 16. Moreover, a three-way shut-off valve 13 is connected to a nitrogen reservoir 18, which is a cylinder for technical gases at a pressure of 200 bar. The scintillation chamber 14 is equipped with a measuring device 17, which is a photomultiplier with a pulse counter of the PYLON AB5 type, which is connected via a signal cable with the recording, control and computing module 5. Moreover, the recording, control and computing module 5 is connected by means of cables signal with a flow meter in the filter separator station 2, as well as with a flow meter 7 and a filtering and measuring device 8 in the solid fraction measuring circuit. The recording, control and calculation module 5 is also connected with the supply valve 3, discharge valve 4, three-way valve 6, first pressure reducer 9, second pressure reducer 11, control manometer 12 and three-way shut-off valve 13 by means of signal lines not shown in the drawing. .

An example of a system of devices for measuring the radioactive activity of Pb-210 lead on filter cartridges in gas filter separator batteries can be described more fully by presenting the method of its operation. In order to measure the solids content, the recording, control and calculation module 5 sends control signals which automatically open the inlet valve 3 and the outlet valve 4 and set the three-way valve 6 in a position that allows gas to flow through the solid fraction measurement circuit. The flow meter 7 measures the volume of gas that flows through the filtering and measuring device 8, measuring the weight gain of the measuring filter. It is possible to carry out the measurement according to any schedule programmed in the recording, control and calculation module 5, e.g. measurement for 1 hour a day. The measured values of the gas volume and the mass of the solid particles are sent to the recording, control and computation module 5 and on their basis the content of solid particles k in the gas is calculated, expressed as the quotient of the measured mass of these particles in the gas sample and the volume of this gas sample. Moreover, information on the volumetric flow of gas Q flowing through gas pipeline 1, measured by gas, is sent to the recording, control and computing module 5.

By means of flow meters belonging to the infrastructure of the filter separator station 2. In order to measure the radon concentration Rn-222, the recording, control and calculation module 5 sends control signals, which automatically open the inlet valve 3, close the outlet valve 4 and set the three-way valve 6 in a position that allows gas flow through the Rn-222 radon concentration measuring circuit. In a first step, the gas pressure is reduced in the first pressure reducer 9 and the gas tank 10 is charged. Then, the pressure of the gas flowing from the tank 10 is reduced in the second pressure reducer 11, and its pressure at the outlet from the second pressure reducer 11 is controlled by the control manometer 12. The opening of the automatic inlet shut-off valve 13 controlled by the recording, control and computing module 5 and the outlet shut-off valve 15 causes the scintillation chamber 15 to be filled with gas, then the shut-off valves: inlet 13 and outlet 15 are closed and the measuring device 17 measures the radon concentration Rn-222 in a closed gas volume, and the results of this measurement are sent to a recording, control and computing module 5. A 16-gas choke installed at the outlet from the Lucas chamber, suppresses pressure surges inside the Lucas chamber while filling the chamber with a gas sample. To perform a re-measurement, the scintillation chamber 14 is flushed with gas from the vessel 10, or the gas supply is shut off with the inlet shut-off valve 13 while applying nitrogen gas in the nitrogen vessel 18 under pressure to the chamber. Flushing is performed with the outlet shut-off valve 15 open. The system operation can be controlled automatically, controlled by the recording, control and calculation module 5, or manually.

The recording, control and computing module 5, has the option of entering additional data using the keyboard or wirelessly, such as the distance I between the analyzed gas purification system and the one preceding it, the cross-sectional area of the gas pipeline A. The software of the recording, control and computing module 5 has the possibility of introducing any dependence on the basis of which the activity of lead Pb-210 is calculated.

The designed system guarantees safe operation with explosive gas, which is natural gas, thanks to the isolation of the gas sample in the Lucas scintillation chamber from the power source of the measuring system.

Description of drawing markings:

- gas pipeline

- filter separator station

- inlet valve

- discharge valve

- recording, control and computing module

- the first three-way valve

- flow meter

- filtering and measuring device

- the first pressure reducer

- tank

- second pressure reducer

- control manometer

- inlet shut-off valve

- scintillation chamber

- outlet shut-off valve

- choke

- measuring device

- nitrogen tank

Claims (12)

1. Method for determining the radioactive activity of Pb-210 lead on filter cartridges, especially in gas filter separator batteries, characterized in that the average radon concentration Rn-222 CRn in the gas flowing through the filter separator is measured by known measurement methods, as well as the gas volume flow Q and the average content of solid particles kw in the gas, while the activity of lead Pb-210 Apb in the dust collected on the filter element is calculated from the dependence: where: Apb - activity of Pb-210 lead in dust, Apb - Pb-210 lead decay constant, CRn - Rn-222 radon concentration, Aro - radon decay constant Rn-222, k - solids content in the gas, I - distance between the analyzed gas cleaning system and the system preceding it, A - pipeline cross-sectional area (1) Q - average gas volume flow. 2. The method according to p. The method according to claim 1, characterized in that the measurement of the average radon concentration Rn-222 CRn is performed by means of a scintillation chamber (14), which is a Lucas chamber equipped with a measuring device (17). 3. The method according to p. 1 or 2, characterized in that the measurement of the average radon concentration Rn222 CRn in the gas is performed at least once a day for the entire period of operation of the filter cartridge 4. The method according to p. The method of claim 1, characterized in that the measurement of the gas flow rate Q is performed with a flow meter belonging to the gas pipeline infrastructure in the filter separator station (2). 5. The method according to p. The method according to claim 1, characterized in that the measurement of the average solids content in the gas k is performed at least once a day for the entire period of operation of the filter cartridge by means of a filtering and measuring device (8) and a flow meter (7). 6. A system of devices for determining the radioactive activity of Pb-210 lead on filter cartridges, especially in filter separator batteries, characterized by having two measuring circuits: - a solid fraction measuring circuit connected in parallel to the gas pipeline (1), including a flow meter (7) and a filtering and measuring device (8), connected with each other by means of hydraulic lines in series in any order, and - led out from the gas pipeline (1) or from the solid fraction measurement circuit and discharged to the atmosphere, the Rn-222 radon concentration measurement circuit, containing at least one pressure reducer (9, 11) arranged in succession, gas tank (10), control manometer ( 12), an inlet shut-off valve (13) and a scintillation chamber (14) equipped with a measuring device (17), connected to each other by means of hydraulic lines. Device arrangement according to claim 1. 6. The method according to claim 6, characterized in that the connection of the solid fraction measuring circuit to the gas pipeline (1) is effected through the supply valve (3) and the discharge valve (4). 8. An apparatus arrangement according to claim 1. 6. The method of claim 6, characterized in that the output of the Rn-222 radon concentration measuring circuit from the solid fraction measuring circuit is effected through the first three-way valve (6). An apparatus arrangement according to claim 1. The method of claim 6, characterized in that the discharge of the Rn-222 radon concentration measuring circuit from the solid fraction measuring circuit to the atmosphere is effected through the outlet shut-off valve (15) and the throttle (16). PL 237 746 Β1 10. An arrangement of devices according to claim 1. A valve as claimed in claim 6, characterized in that the inlet shut-off valve (13) is a three-way valve to which a pressurized nitrogen reservoir (18) is additionally connected via a hydraulic line. Device arrangement according to claim 11. 6, characterized in that it additionally comprises a recording, control and computing module (5), equipped with a data input panel and a data transmission system, connected by signal cables or wirelessly to a measuring device (17), a flow meter (7), a filtering and measuring device ( 8) and a flow meter in the filter separator station (2). 12. An apparatus arrangement according to claim 1. 11, characterized in that the recording, control and computing module (5) is connected via signal lines or wirelessly to the supply (3) and discharge (4) valves, the first three-way valve (6), the inlet shut-off valve (13), the outlet shut-off valve (15) and pressure reducers (9, 11) as well as a control manometer (12) and a throttle (16), which have an automatic control mechanism.