Measuring probe and device for passive long-term measurement of soil air radon concentration

Abstract

Measuring probe (1) for the passive long-term measurement of the air concentration of radon, consisting of a base body (2) with a recess (3) provided in the base body (2) and a solid-state track detector (4) insertable into the recess (3), and a diffusion membrane (5) sealingly covering the base body (2) with the solid-state track detector (4) inserted into the recess (3), and a measuring volume (6) remaining between the solid-state track detector (4) and the diffusion membrane (5).

Description

[0001] The invention relates to a measuring probe for the passive long-term measurement of the air concentration of radon, in particular the soil air concentration or the air concentration in walls, according to claim 1 and to a device for the passive long-term measurement of the air concentration of radon, in particular the soil air concentration or the air concentration in walls, according to claim 9.

[0002] Radon is a radioactive noble gas that occurs as a component of natural radioactive decay chains and is found primarily in mountain ranges with a relatively high proportion of uranium ore in the basement. Radon accumulates primarily in poorly ventilated spaces and is absorbed through the air we breathe. The ionizing radiation emitted by radon and the decay products produced during its radioactive decay, particularly the directly formed alpha-emitting polonium nuclides and the other decay products in the decay chain, pose a significant health risk.

[0003] For these reasons, it is necessary to determine the concentration of radon in the air, especially in the soil air, or in walls, especially before construction work takes place in an area where high radon levels are expected.

[0004] A number of state-of-the-art devices are known for determining the radon concentration in soil air. Typically, these systems rely on so-called active detection systems, which involve drilling into the soil at a series of predetermined points on the ground surface. Devices are then inserted into these holes through which air or another largely radioactive gas is added or extracted at a known flow rate. The gas, acting as a carrier medium, carries the radon present there with it. After the gaseous carrier medium, now laden with radon, is subsequently discharged, the carrier medium is fed to a detection device, where the absorbed radon components are analyzed.After a defined period of operation of such a device and a corresponding distribution of boreholes in the field, topographical maps of the radon contamination of a given area are then created.

[0005] For example, DE 43 10 096 A1 discloses a method and device for measuring the radon content in soil gas. According to the teaching contained therein, a measuring tube is inserted into a borehole of a predetermined depth in the ground, and the soil gas is extracted and fed to a measuring point for measuring radon. A vacuum generated by a suction pump is continuously regulated and set to predetermined values. The vacuum and the volume flow of the soil gas are measured separately and recorded in a characteristic curve.

[0006] DE 20 2018 004 790 U1 discloses a soil probe carrier for accommodating soil inlet probes. It features a closable tubular structure made of hard metal for accommodating soil probes, which is equipped with a mounting device for measuring probes.

[0007] It is clear that the use of active detection and monitoring systems of this type is associated with high costs and installation effort. Radon detection in an area is therefore correspondingly expensive and ultimately results in increased costs for the development of building land overall. Previous methods for determining radon soil gas concentrations (RBLK) require either complex drilling work (e.g. in conjunction with driven core drilling), which must be carried out with diameters of approximately 30 millimeters or more. In addition to the high costs, changes in soil properties in the created measurement volume occur that have a significant impact on the results, particularly in the form of soil compaction and thus changes in soil structure. Soil probes with a packer system operate with only short measurement times, ranging from a few minutes to single-digit hours.The installation and operation of such measuring devices also requires considerable specialist knowledge and can therefore only be carried out by appropriately trained personnel.

[0008] Given the aforementioned problems, the task arises of providing means that can significantly simplify the determination of radon concentrations in the air, especially in the soil, so that the equipment and personnel required, as well as the associated costs, can be minimized. Furthermore, changes in soil structure, which can ultimately distort the measurement results, should be minimized or largely avoided, and the desired means should enable long-term measurements that can be carried out for virtually any length of time in the designated area.

[0009] The object is achieved with a measuring probe for passive long-term measurement of the air concentration of radon having the features of claim 1 and a device provided therefor having the features of claim 9. The respective subclaims contain expedient and advantageous designs and embodiments.

[0010] The measuring probe according to the invention for the passive long-term measurement of the air concentration of radon consists of a base body with a recess provided in the base body and a solid-state track detector insertable into the recess and a diffusion membrane sealingly covering the base body with the solid-state track detector inserted into the recess and a measuring volume remaining between the solid-state track detector and the diffusion membrane.

[0011] The basic idea behind the probe is to use a solid-state trace detector to determine the air concentration. This detector operates passively, meaning that the radon decay processes leave traces in the detector during the measurement period. The density of the traces can be evaluated under a microscope after removing the solid-state trace detector, allowing a conclusion to be drawn about the radon concentration that has accumulated during the measurement period. The solid-state trace detector is housed in a recess in a base body, and this recess is also covered by the diffusion membrane.

[0012] This overlap achieves two things. Firstly, the diffusion membrane prevents unwanted radionuclides from entering the solid-state track detector. Secondly, it significantly reduces and simultaneously defines the effective measurement volume. This ensures that the density of the tracks within the detector remains sufficiently low even over an extended period of time, so that microscopic analysis still delivers meaningful and analyzable results. Furthermore, the diffusion membrane protects the solid-state track detector from contamination and damage.

[0013] In an advantageous design, the base body is in the form of a rod, wherein the recess is arranged in a lateral surface of the rod.

[0014] The base body can expediently consist of a stable, radon-tight material, in particular a plastic.

[0015] In an advantageous design, the base body also has recesses for attaching the end of a probe guide. This makes the base body, and thus the measuring sensor, part of a higher-level detector component that can be handled as a whole.

[0016] In a suitable embodiment, the solid-state tracking detector is designed as a detector plate that can be releasably clamped into the recess of the base body. This significantly simplifies the construction of the measuring probe and allows for a miniaturized design of the measuring probe.

[0017] The diffusion membrane is designed, in particular, as an elastic tube that can be pushed over the base body. The tube is constructed with a material and a wall thickness that prevents the passage of at least one specific radon isotope into the measurement volume. In particular, this prevents the nuclide Rn-220 (so-called thoron) from entering the measurement volume, favoring the longer-lived nuclide Rn-222. This results in a predominantly to practically exclusive selectivity of the solid-state track detector for the detection of a single nuclide. The shorter-lived nuclide Rn-220 decays during diffusion within the diffusion membrane; it does not reach the measurement volume above the solid-state track detector and thus does not contribute to the traces to be evaluated.

[0018] A holding device (tube or rod) of any length can be provided as the probe guide, with the base body being insertable into / attachable to the holding device at its end and coupled to a locking device connecting the holding device and the base body. This allows the measuring probe to be advanced to virtually any depth and borehole.

[0019] In one embodiment, the probe guide, in particular the holding device, together with the coupled base body, the solid-state tracking detector and the diffusion membrane is inserted as a probe unit into an outer protective tube, wherein a locking means, in particular a cap screw, which can be attached to the upper end of the holding device is provided for holding the probe unit in the protective tube.

[0020] The device according to the invention for passive long-term measurement of the air concentration of radon comprises a protective tube and a measuring chamber arranged in at least one section of the protective tube, accessible to the radon occurring in the ground area, as well as a probe unit that can be inserted into the protective tube. The probe unit consists of a probe guide and a passive measuring probe attached to the end of the probe guide and located in the area of ​​the measuring chamber.

[0021] In one embodiment, the protective tube contains a propelling tip at its lower end as a salvage tip. The protective tube can therefore be removed from the ground area in such a way that the propelling tip remains in the ground.

[0022] In one embodiment, the probe guide is designed as a holding device with a passive measuring probe that can be locked in / on the holding device.

[0023] A locking device that can be attached to the upper end of the probe guide, in particular the holding device, can be provided for positioning the probe guide within the protective tube.

[0024] According to the invention, the measuring probe is designed as a base body with a solid-state track detector releasably clamped into a recess and a diffusion membrane covering the recess with the solid-state track detector.

[0025] In addition, in one embodiment, a closure cap may be provided that covers an upper end of the protective tube protruding from the base area.

[0026] In one embodiment, the closure cap can have a passive signaling device that can be detected by an external locating device. This allows the measuring probe to be left in the field for an extended period, while the location of the device remains detectable even if the area becomes overgrown or otherwise covered.

[0027] The subject matter of the invention will be explained in more detail below using exemplary embodiments. The attached drawings serve to clarify Fig. 1 to 4. The same reference symbols are used for identical and / or equivalent parts.

[0028] It shows: Fig. 1 an exemplary passive measuring probe in longitudinal and cross-sectional view, Fig. 2 the exemplary measuring probe from Fig. 1 in combination with a holding tube, combined in an exemplary probe unit, Fig. 3 the exemplary probe unit from Fig. 2 in combination with a surrounding protective tube and other components, Fig. 3a an exemplary probe unit with a rod as probe guide, Fig. 4 exemplary measured soil air concentrations of Radon-222 according to the state of the art for comparison.

[0029] Fig. Figure 1 shows an exemplary passive measuring probe 1 in a longitudinal section and, below, in a cross-section. The measuring probe 1 has a base body 2.

[0030] This contains a recess 3. The recess 3 can, in principle, be located anywhere on the base body. For a cylindrical base body, as in the present example, a recess in the area of ​​the lateral surface of the base body cylinder is suitable.

[0031] A solid-state track detector 4 can be inserted into the recess 3. The contour of the recess and the contour of the solid-state track detector are arbitrary. Both contours can be expediently designed in such a way that they allow for a slightly clamped insertion of the solid-state track detector, at least in sections. Such a fastening eliminates the need for additional fastening means and simultaneously positions the solid-state track detector in a defined position. Of course, the solid-state track detector can also be secured in the recess using an additional fastening means.

[0032] The arrangement of the recess 3 and the solid-state track detector 4 mounted therein is covered with a diffusion membrane 5. The diffusion membrane 5 completely and sealingly covers at least the recess with the solid-state track detector located therein and the adjacent edge areas, in such a way that a gap remains between the free surface of the solid-state track detector 4 and the diffusion membrane. This gap forms the measuring volume 6 of the measuring probe 1.

[0033] The detector system implemented in this measuring probe thus uses a solid-state track detector adapted to the detector geometry in a geometry optimized for radon soil gas measurement and features a simple, robust construction that is largely insensitive to water and the nuclide Rn-220 (thoron).

[0034] The base body 2 consists, for example, of an approximately 5 cm long, rod-shaped plastic base body, into which a recess for accommodating the solid-state tracking detector is machined approximately 1 cm from one end of the rod. The solid-state tracking detector (SSTD) is designed here as a detector plate 7 and has dimensions of, for example, 10 x 5 x 1 mm. In particular, the base body has a diameter that almost corresponds to the inner diameter of a holding tube or a corresponding receptacle in a holding device.

[0035] Recess 3, for example, has a length of approximately 10 mm and a depth of approximately 2.5 mm. The FKSD fits precisely into this recess and is secured in place.

[0036] In this example, a piece of elastic tubing 8 is formed over the plastic base body as a diffusion membrane 5. In this example, this tubing is pushed over the base body 2 in an absorbent and watertight manner in the form of a piece of silicone tubing of the appropriate length. This ensures an overlap of the recess of the FKSD at the top and bottom. The overlap is, for example, 1 cm. This additionally holds the FKSD in a defined and stable position. The remaining cavity between the FKSD and the inside of the tubular silicone membrane forms the aforementioned measuring volume 6.

[0037] The thickness and material of the diffusion membrane 5 and in particular of the silicone tube 8 are selected such that the outer diameter of the tube, when pushed onto the base body, is slightly smaller than the inner diameter of a surrounding outer protective tube. The inner diameter of the tube should allow it to be pulled tightly and elastically onto the base body. At the same time, the material of the diffusion membrane and the tube is selected such that the diffusion through of certain undesirable nuclides is prevented. This ensures, in particular, that the nuclide Rn-220 (thoron) is effectively retained. This is achieved by the material and thickness of the diffusion membrane only allowing diffusion of radon over a sufficiently long time. With an exemplary diffusion time of more than 15 minutes in the material of the diffusion membrane, the nuclide Rn-220 (thoron), with a half-life of approximately57 s practically no longer occupies the measuring volume 6 of the measuring probe and thus cannot affect the solid-state track detector 4. This ensures that practically only the nuclide Rn-222 remains in the measuring volume, which, with a half-life of approximately 3.8 days, can easily penetrate the diffusion membrane without the majority of the Rn-222 having already decayed on the diffusion path in the diffusion membrane.

[0038] Fig. 2 shows the exemplary measuring probe 1 from Fig. 1 in combination with a holding device 9, which here is designed as a holding tube. The holding device 9, i.e., the holding tube, is the probe guide in this example. The probe guide serves to attach an extension of any length to the measuring probe and simultaneously position the measuring probe at a predetermined location.

[0039] Instead of the holding tube, a continuous solid rod can of course also be provided, which has a corresponding holder for the measuring probe at the end.

[0040] The measuring probe 1 and the probe guide, in particular the holding tube, are combined in an exemplary probe unit 10. In the present example, in which the holding device 9 serves as the probe guide, the base body 2 is inserted into the holding device 9 at its end. The thickness of the diffusion membrane 5 or the tube 8 acting as the diffusion membrane is dimensioned such that it does not protrude beyond the outer dimensions of the holding device. This largely prevents damage when the probe unit 10 is inserted into a surrounding borehole or into a protective tube.

[0041] The measuring probe 1 is expediently sufficiently firmly connected to the probe guide. In the present example, for example, the base body 2 can be pushed into the holding device 9 at its end and clamped there. In the present example, a locking means 11 is provided which, in addition to or instead of the clamp connection, is pushed through the holding device 9 and the base body 2 and thus realizes a secure connection between the measuring sensor and the holding tube. The locking means is, for example, a bolt, a screw, or another comparable fastening means. Plastic, for example, can be used as the material for the holding device. A certain degree of flexibility is particularly expedient here, whereby the holding device can also be pushed along certain curves.

[0042] Of course, instead of the holding tube, a solid rod with a shaped end for attaching the measuring probe can also be used as the probe guide. Wire- or thread-like designs (not shown) connected to the base body of the measuring probe are also possible.

[0043] In the present example, the measuring probe 1 is inserted into the lower end of the holding tube and secured in the holding tube by means of a suitable holding device against falling out.

[0044] Fig. 3 shows the exemplary probe unit 10 from Fig. 2 in combination with a surrounding protective tube 12 and other components. The probe guide, ie the holding device 9 according to the illustrated embodiment of Fig. 2, is inserted here together with the measuring probe 1 into the surrounding protective tube 12.

[0045] In the present example, a matching cap screw 13 is screwed into the upper end of the holding device 9. The cap screw 13 has a screw head diameter that is at least larger than the inner diameter of this protective tube 12. The screw head of the cap screw 13 thus holds the entire probe unit construction, consisting of the holding device 9 and the measuring probe, in the protective tube 12 and prevents this construction of the probe unit 10 from slipping downward.

[0046] The protective tube 12 has, at least in the area in which the measuring probe 1 is located when the probe unit 10 is inserted, a measuring chamber 14 into which soil gases can reach the measuring probe 1 located inside the protective tube via suitable openings, so that the radon present in the soil gas can ultimately be detected there in the manner described.

[0047] The holding device 9 is in the embodiment of Fig. 3 is designed such that its outer diameter can be slidably inserted into the inner volume of the surrounding protective tube 12, leaving only a narrow clearance between the holding device 9 and the protective tube, thus sealing the measuring chamber 14 practically airtight at the top. This reliably prevents external air volumes from penetrating the measuring chamber 14, which could distort the measured values.

[0048] The protective tube 12 serves on the one hand to protect the probe unit 10 from the surrounding ground area, but on the other hand also as a propulsion means for introducing the probe unit into the ground area. This introduction can be carried out by hammering it into the ground, e.g. after pre-drilling a hole with a slightly smaller diameter than the outer diameter of the protective tube 12, or by a rotating drilling movement, in which case the usual tools such as hammers or drills or other means can be used. For introduction by means of a drilling movement, the upper end of the protective tube can be provided with an adapter, for example, via which a conventional drill can be coupled to the protective tube. It is also possible to insert parts into the protective tube that provide a striking surface for a hammer or similar ramming device.

[0049] To facilitate advancement, a propulsion tip 15 can be arranged at the lower end of the protective tube 12. The propulsion tip can, in particular, be designed as a lost tip that remains in the ground when the protective tube is pulled out of the ground area.

[0050] Finally, the protective tube 12 is sealed at the upper end protruding from the ground with a tightly closing cap 16, for example a cap made of PVC or another plastic, to make it airtight against the outside air and corresponding weather influences.

[0051] The entire assembly thus formed and inserted into the ground, comprising the protective tube 12, the closure cap 16 and the components of the probe unit 10 located in the protective tube, can now remain at the measurement location for a predetermined, but in principle arbitrary, time. The probe unit 10 can be withdrawn as a whole from the protective tube at predetermined intervals. The measuring sensor 1 is then separated from the probe guide, i.e. in particular from the holding device 9. Finally, the solid-state track detector 4 is removed from the measuring sensor 1 for further analysis, i.e. for microscopic evaluation. A new solid-state track detector 4 is inserted into the base body of the measuring probe, the measuring probe is assembled in the manner described and connected to the probe guide, i.e. the holding device 9.The probe unit 10 thus formed is then inserted into the protective tube still located in the ground and the measurement can be continued after the closure cap 16 has been put on.

[0052] Fig. 3a shows as a supplement to Fig. 3 shows an embodiment in which the probe guide is realized by a thin rod and / or a thread 10a. All other components are in the Fig. 3a given example otherwise has the same effect as the example from Fig. 3. In particular, the rod and / or thread 10a is attached to the cap screw 13 and the base body 2 of the measuring sensor 1, so that the measuring sensor 1 hangs freely on the wire or thread 10 in the protective tube 12.

[0053] At the Fig. 3a, the measuring chamber 14 is upwardly arranged compared to the embodiment of Fig. 3 is naturally less effectively sealed. The sealing effect is practically only achieved via the cap. In principle, the Fig. 3a also serves its purpose and enables the determination of the radon concentration to be measured.

[0054] The protective tube 12 can remain in the ground for an extended period of time even without internal components. To facilitate retrieval of the protective tube even after extended periods and when the measurement area becomes increasingly overgrown with vegetation, the closure cap 16 can have a signaling device 17 detectable by an external locating device. In the simplest case, this signaling device can be a ferromagnetic piece of metal, which is therefore particularly easy to locate using a metal detector; however, a readable passive RFID data carrier with a corresponding antenna device is also possible. The latter allows for more targeted and unambiguous identification of the measuring point located in the ground.

[0055] The measuring system described here is characterized by its ability to determine radon soil air concentrations (RBLK) as a long-term mean value (e.g. as an annual mean value) under largely realistic, non-distorting environmental conditions.

[0056] The quality assurance of the measuring system can be carried out centrally by a recognized measuring body and thus, in contrast to the established procedures, this system can be used and implemented by anyone without their own quality assurance.

[0057] The system is suitable for measurements to determine the radon potential, e.g. for the designation of radon precaution areas, as well as for the assessment of subsoil for individual objects.

[0058] The complex drilling work (e.g., driven core drilling) with diameters of approximately > 30 mm required by previous methods for determining the RBLK, and the associated, result-relevant changes in soil properties within the created measurement volume (e.g., soil compaction and thus changes in soil structure), are not required with the present system or are reduced to a minimum. The relatively short measurement times of conventional soil probes with packer systems, ranging from a few minutes to the single-digit hour range, can be exceeded many times over with the present system. This significantly improves the comparability of Rn-222 long-term indoor measurement values ​​with the Rn-222 long-term soil gas measurement values ​​made possible by the invention.

[0059] In the diagram in Fig.Figure 4 shows the temporal progression of radon concentration using real measurements from a discontinuously actively sampled radon soil air probe. This progression is typical for radon concentrations in soil air. Each individual measurement represents a complete measurement, as would be obtained using active probes.

[0060] The fluctuations in the measured values ​​(min: approx. 19 kBq / m 3 - Max: approx. 104 kBq / m 3 ) throughout the entire measurement period. As can be seen, a technically accurate correlation of soil radon concentrations to the annual mean indoor radon concentrations in houses can hardly be established with active short-term measurements (which are usually only measured once per location), or only with very large uncertainties.

[0061] This means that RBLK's active measurement systems are not ideally suited for long measurement periods (days to a year) and thus for the comprehensive assessment of the radon situation in soils. The passive radon soil gas measurement system described here fills this gap.

[0062] The advantages of the measuring system according to the invention are therefore as follows: 1. The probe can be inserted without digging, but only by rotary drilling and / or percussive drilling. 2. There is only a very slight influence on the soil structure due to a possible small diameter of the overall arrangement (10 to 12 mm), a "lost" tip at the end of the probe, the possibility of "pre-drilling" a thinner hole (e.g. 8 to 10 mm) than the outer diameter of the protective tube, the possibility of careful insertion of the protective tube, e.g. with constant pressure or with minimal impact load to minimize leaks between the protective tube and the surrounding soil and thus to minimize possible short-circuit flows with outside air. 3. The solid-state tracking detector is reliably protected against water and the nuclide Rn-220 (Thoron). 4. There is a wide range of measurement times from 1 day to 1 year and more at radon soil air concentrations in the range of approximately 10 kBq / m 3 - more than 300 kBq / m 3 (For a radon potential value of less than 40, 300 kBq / m 3a soil gas permeability of less than 1*10-17 m 2 needed.) 5. It is possible to use the measuring point several times by replacing the detector under constant conditions of the protective tube. 6. The integration of soil permeability measurements at the beginning and end of a measurement campaign is possible in any case. 7. The measurements can be performed with minimal personnel effort. All that is required is driving in the protective tube, inserting the probe unit, attaching or removing the cap, pulling the probe unit out of the protective tube, and finally pulling out the protective tube itself. 8. Averaging over an exposure period is easily possible due to the long measurement periods. 9. The waiting time at the measuring point, which is required with conventional measuring systems, until a radioactive equilibrium is established in active sampling systems, is no longer necessary. 10. There are no changes in the pressure conditions during the measurement period, ie the ground conditions prevailing at the measuring point with regard to gas transport remain undisturbed. 11. The qualification requirements for personnel applying the measurement principle on-site are low. Basic technical knowledge is sufficient.

[0063] The achievable measurement and evaluation period is highly variable and can range from one day to one year, or even longer. The technical effort required for the measurement is very low, and the costs per measurement are sustainably minimized. The qualification requirements are so low that virtually anyone can install the measuring device in the ground. Soil system disturbances caused by probe installation are minimal. The dynamic range of measurable radon exposures is very high, ranging from 10 to 1,000,000 kBq*h / m 3 . In addition, the measuring system is very robust.

[0064] The subject matter of the invention has been explained using exemplary embodiments. Further embodiments are possible within the scope of one skilled in the art. These are also set forth in the dependent claims. List of reference symbols 1 measuring probe 2 basic bodies 3 recess 4 Solid-state track detector 5 Diffusion membrane 6 measuring volumes 7 detector plates 8 Elastic hose 9 Holding device as probe guide 10 probe unit 10a Rod, wire and / or thread as probe guide 11 locking devices 12 protective tube 13 Cap screw 14 Measuring room 15 Tunneling tip 16 Cap 17 Signaling devices

Claims

[1] Measuring probe (1) for the passive long-term measurement of the air concentration of radon, consisting of a base body (2) with a recess (3) provided in the base body (2) and a solid-state track detector (4) insertable into the recess (3) and a diffusion membrane (5) sealingly covering the base body (2) with the solid-state track detector (4) inserted into the recess (3) and a measuring volume (6) remaining between the solid-state track detector (4) and the diffusion membrane (5). [2] Measuring probe according to claim 1, characterized by that the base body (2) is designed in the form of a rod, wherein the recess (3) is arranged in a lateral surface of the rod. [3] Measuring probe according to one of claims 1 or 2, characterized by that the base body (2) consists of a stable, radon-tight material, in particular of a plastic. [4] Measuring probe according to one of claims 1 to 3, characterized bythat the base body (2) has formations for the terminal attachment to a probe guide. [5] Measuring probe according to one of claims 1 to 4, characterized by that the solid-state track detector (4) is designed as a detector plate (7) which can be releasably clamped into the recess (3) of the base body (2). [6] Measuring probe according to one of the preceding claims, characterized by in that the diffusion membrane (5) is designed as an elastic tube (8) which can be pushed over the base body (6), the tube (8) being designed with a material and a wall thickness, the tube (8) being designed with a material and a wall thickness in which the passage of at least one specific radon isotope into the measuring volume (6) is prevented. [7] Measuring probe according to claim 4, characterized bythat a holding device (9) of any length is provided as the probe guide, wherein the base body (2) can be inserted into the holding device (9) at its end and / or attached to the holding device (9) and secured with a locking means connecting the holding device (9) and the base body (2). [8] Measuring probe according to claim 7, characterized by that the holding device (9) together with the measuring probe (1) is inserted as a probe unit (10) into an outer protective tube (12), wherein a locking means, in particular a cap screw (13), which can be attached to the upper end of the holding device (9) is provided for holding the probe unit (10) in the protective tube (12). [9] Device for the passive long-term measurement of the air concentration of radon, comprising a protective tube (12) with at least one measuring chamber (14) arranged in a section of the protective tube (12) and accessible for accumulating radon, and a probe unit (10) which can be inserted into the protective tube (12), consisting of a probe guide and a passive measuring probe (1) fastened to the end of the probe guide and located in the region of the measuring chamber, wherein the measuring probe (1) is designed as a base body (2) with a solid-state track detector (4) which is releasably clamped into a recess (3) and a diffusion membrane (5) covering the recess (3) with the solid-state track detector (4). [10] Device according to claim 9, characterized by that the protective tube (12) contains a lost tip at the lower end as a propulsion tip (15). [11] Device according to claim 9, characterized bythat the probe guide is designed as a holding device (9) for the passive measuring probe (1) which can be locked at the end in the holding device (9). [12] Device according to one of claims 9 or 11, characterized by that a locking means which can be attached to the upper end of the probe guide, in particular the holding device (9), is provided for positioning the probe guide within the protective tube (12). [13] Device according to one of claims 9 to 12, characterized by a closure cap (16) covering the upper end of the protective tube (12) protruding from the base area. [14] Device according to claim 13, characterized by that the closure cap (16) has a passive signaling means (17) which can be detected by means of an external locating device.

Images