SI9111472A

SI9111472A - Probe for measuring radon air levels featuring a solid detector of nuclear traces

Info

Publication number: SI9111472A
Application number: SI9111472A
Authority: SI
Inventors: Tomaz Sutej; Milko Krizman; Radomir Ilic
Original assignee: Inst Jozef Stefan
Priority date: 1991-09-02
Filing date: 1991-09-02
Publication date: 1997-10-31

Abstract

V sondi po izumu je trdni detektor (D) jedrskih sledi nameščen znotraj prizmatičnega obroča (R), katerega konca pokrivata pokrova (C1, C2). Na notranja obodna prislona (F1, F2) obroča (R), ki sta pravokotna na vzdolžno obročevno os (A), sta prislonjena filter (F) oziroma zaščitna ploščica (PP), ki obdajata aktivno oglje (AC). Filter (F) prekriva na prislon (F1) opirajoča se zaščitna mrežica (PN). Detektor (D) je vstavljen v centrirni obroček (CR2) nad zaščitno ploščico (PP).In the probe of the invention is a solid detector (D) of nuclear the trace placed inside the prism ring (R), whose ends are covered by lids (C1, C2). On the inner circumferential stop (F1, F2) of the ring (R) which are perpendicular to the longitudinal annular axis (A), they are supported filter (F) or protection plate (PP) which they surround activated carbon (AC). Filter (F) overlaps to backrest (F1) retractable safety net (PN). The detector (D) is inserted into the centering ring (CR2) above protection plate (PP).

Description

Institut Jožef Stefan'Jozef Stefan Institute '

Sonda za merilnik koncentracije radona v zraku, opremljena s trdnim detektorjem jedrskih slediAirborne radon concentration meter probe equipped with a solid nuclear trace detector

Področje tehnikeThe field of technology

Izum spada v področje zaznavanja elementov s pomočjo jedrskega sevanja.The invention falls within the field of element detection by means of nuclear radiation.

Predmet izuma je po mednarodni klasifikaciji patentov uvrščen v razred G 01V 5/00.According to the international patent classification, the subject matter of the invention is classified in class G 01V 5/00.

Tehnični problemA technical problem

Glede na pomanjkljivosti dosedaj znanih sond za merjenje koncentracije radona (^Rn) s trdnim detektorjem jedrski sledi je tehnični problem izuma v tem, kako skonstruirati preprosto in kompaktno sondo omenjene vrste vendar z močno povečano občutljivostjo za radon, pri čemer naj bo detektor ves čas zaščiten pred ultravioličnimi žarki, sondin filter, ki deluje kot difuzijska ovira za zrak, pa naj bo varen pred mehanskimi poškodbami.In view of the disadvantages of the known radon (^ Rn) probes with a solid nuclear trace detector, the technical problem of the invention is how to construct a simple and compact probe of the aforementioned type, but with greatly increased radon sensitivity, with the detector being protected at all times against ultraviolet rays, the probe filter acting as an air diffusion barrier should be protected from mechanical damage.

Stanje tehnikeThe state of the art

Za določanje koncentracije radona, mišljen je ²²²Rn, v okolju se v zadnjem desetletju precej uporablja sonde s trdnim detektorjem jedrskih sledi. Te sonde se izvede tako, da so neobčutljive na aktivnost drugih dveh radioaktivnih izotopov plinastega radona, to je torona (²²⁰Rn) ter aktinona (²¹⁹Rn). Meritve namreč kažejo, da je povprečen prispevek radonovih kratkoživih razpadnih produktov k efektivni ekvivalentni dozi naravnega sevanja okoli 45%. Detektor sonde je od področja, v katerem se želi meriti koncentracijo radona, ločen z difuzijsko oviro sonde. V tej oviri razpadeta toron (razpolovna doba 54 s) in aktinon (3,9 s), preden v sondi dosežeta občutljivi prostor blizu detektorja. Difuzijska ovira je v obliki daljše zračne poti do detektorja ali pa je izvedena kot filter oziroma vrečka iz polimera. ²²² Rn is meant to determine radon concentration, and probes with a solid nuclear trace detector have been used extensively in the environment over the last decade. These probes are designed to be insensitive to the activity of the other two radioactive isotopes of gaseous radon, namely torone ( ²²⁰ Rn) and actinone ( ²¹⁹ Rn). The measurements show that the average contribution of radon's short-lived decay products to the effective equivalent dose of natural radiation is about 45%. The probe detector is separated by a diffusion barrier from the area in which the radon concentration is to be measured. In this obstacle, the toron (half-life 54 s) and actinone (3.9 s) decay before reaching a sensitive space near the detector in the probe. The diffusion barrier is in the form of a longer airway to the detector or is made as a filter or polymer bag.

Iz patentnega spisa YU 42 445 je poznana sonda za detekcijo radona (²²²Rn) s trdnim detektorjem sledi, kije namenjena prospekciji ležišč urana. Dejanska sonda je pritrjena v cevi, ki služi zbiranju radona in nameščanju sonde na terenu, in obstoji iz druge cevi iz plasta, na katere dnu je v njeni notranjosti pritrjen detektor, drugi konec cevi pa je zaprt s tanko polimerno folijo. Med prenosom nezaščitene sonde je detektor izpostavljen ultravioličnim žarkom, polimerna folija pa ni zaščitena pred mehanskimi poškodbami. Ta sonda je uporabna pri veliki koncentraciji radona, sicer je čas ekspozije zelo dolg. Najmanjša koncentracija C_mjn radona, ki se jo še lahko določi s trdnimi detektorji jedrskih sledi, je namreč določena z izrazomYU 42 445 discloses a radon probe ( ²²² Rn) with a solid trace detector for the uranium prospecting. The actual probe is attached to a tube that serves to collect radon and locate the probe in the field, and consists of a second tube of layer with a detector at its bottom and the other end of the tube sealed with a thin polymer film. During the transmission of the unprotected probe, the detector is exposed to ultraviolet rays and the polymer film is not protected from mechanical damage. This probe is useful for high radon concentrations, otherwise the exposure time is very long. The minimum concentration of C _mjn radon, which can still be determined by solid nuclear trace detectors, is determined by the expression

C_min = [k² + 2k V(po.A + s².A²)] / (A.K.t). Odvisno od konstrukcije in vrste detektorja ter od postopka njegove naknadne obdelave je njegov odziv K med 0,5 in 8 sledi/ cm².kBq.m'³.h, kot njegova teoretična zgornja meja pa velja 10 sledi/cm².kBq.m'³.h. Faktor k zanesljivosti je vrednost standardizirane normalne porazdelitve pri predpisani stopnji verjetnosti za napačno določitev signala, ko ga dejansko ni, in obratno; pri verjetnosti 5 % je k = 1,65. Pri značilni gostoti po = 20 sledi ozadja na cm² in faktorju s = 5 cm'², ki podaja spremembo gostote sledi ozadja, se z detektorjem s površino 1 cm²lahko pri času eksponiranja t = 1 dan določi najmanjšo koncentracijo radona v zraku C_min = 100 Bq/m³. Značilne koncentracije radona na prostem so od 0,1 do 10 Bq/m³, v hišah pa od 10 do 100 Bq/m³. Za meritve koncentracije radona v bivalnem okolju je torej spodnja meja občutljivosti opisane sonde premajhna, da bi ekspozicije lahko bile krajše od okoli 1 tedna.C _min = [k ² + 2k V (po.A + s ² .A ² )] / (AKt). Depending on the design and type of the detector and the process of its post-processing, its response K is between 0.5 and 8 traces / cm ² .kBq.m ' ³ .h, and its theoretical upper limit is considered to be 10 traces / cm ² .kBq. m ' ³ .h. The reliability factor is the value of the standardized normal distribution at the prescribed probability level for the wrong determination of the signal when it is not actually present, and vice versa; at a probability of 5%, k = 1.65. For a characteristic density of = 20 trace backgrounds per cm ² and a factor s = 5 cm ' ² , which gives a change in the trace background density, a minimum radon concentration in air C can be determined at an exposure time of t = 1 for exposures of 1 cm ² _mi n = 100 Bq / m ³ . Typical outdoor radon concentrations are from 0.1 to 10 Bq / m ³ and in houses from 10 to 100 Bq / m ³ . Therefore, for measurements of radon concentration in the living environment, the lower limit of sensitivity of the probe described is too small to allow exposures to be shorter than about 1 week.

S sondami s trdnim detektorjem jedrskih sledi se kumulativno beleži koncentracijo radona skozi daljše obdobje. To je zelo pomembno, ker koncentracija radona dnevno fluktuira tudi za več redov velikosti. Prav zato se pogosto ne potrebuje podatka o trenutni vrednosti koncentracije in so zato merilniki, kot so ionizacijska celica, scintilacijska celica, termolumiscentni detektor, ki je razen tega očutljiv še na γ žarke, in spektrometri v povezavi z adsorbcijskim filtrom iz aktivnega oglja, po nepotrebnem prekompleksni.Probes with a solid nuclear trace detector cumulatively record radon concentrations over a long period. This is very important because the concentration of radon fluctuates over several orders of magnitude daily. For this reason, information on the current concentration value is often not required, and therefore meters such as an ionization cell, a scintillation cell, a thermoluminescent detector that is also sensitive to γ rays, and spectrometers in conjunction with an activated carbon adsorption filter are unnecessary too complex.

Opis rešitve tehničnega problema s primerom izvedbeDescription of a solution to a technical problem with an example implementation

Navedeni tehnični problem je rešen s sondo za merilnik koncentracije radona v zraku, ki je opremljena s trdnim detektorjem jedrskih sledi in v kateri je omenjeni detektor nameščen znotraj prizmatičnega obroča .na enem koncu sondinega občutljivega prostora, katerega drugi konec je zaprt s filtrom, in ki je značilna po tem, da je na obodna prislona, ki sta pravokotna na vzdolžno os prizmatičnega obroča in do katerih je ta obroč znotraj obojestransko skoncema prizmatično razširjen, prislonjen filter oziroma zaščitna ploščica in da je aktivno oglje nameščeno med filtrom in zaščitno ploščico in da je na filter nameščena z njim kongruentna in od njega manjša, a še vedno na prislon preko filtra opirajoča se zaščitna mrežica in da se na filter in na zaščitno mrežico opira do prvega robu prizmatičnega obroča segajoč prvi centrirni obroček in da je na prizmatičen obroč odstranljivo pritrjen prvi pokrov, tako da njegova notranja tesnilka pritiska ob njegov prvi rob in ob prvi centrirni obroček, in da je omenjeni detektor vstavljen v drugi centrirni obroček, ki se opira na zaščitno ploščico in sega do drugega robu prizmatičnega obroča, in da je na prizmatičen obroč odstranljivo pritrjen drugi pokrov, tako da njegova notranja tesnilka pritiska ob drugi rob prizmatičnega obroča in ob drugi obroček.Said technical problem is solved by a probe for a radon in air meter equipped with a solid nuclear trace detector in which said detector is housed inside a prism ring at one end of the probe sensitive space, the other end of which is closed by a filter, and which characterized by the fact that the circumference, perpendicular to the longitudinal axis of the prism ring, to which the ring is extending in a two-way extremity, is supported by a filter or protective plate, and that activated charcoal is placed between the filter and the protective plate and that the filter mounted on it is congruent and smaller, but still supported by a filter mesh supported by the filter and that the first centering ring extends to the first edge of the prism ring and that the first centering ring extends to the prism ring and that the first one is removably attached to the prism ring. cover so that his inner seal presses against his the first edge and the first centering ring, and said detector being inserted into the second centering ring, which rests on the protective plate and extends to the second edge of the prism ring, and that a second cover is removably attached to the prism ring so that its inner seal is pressed along the other edge of the prism ring and along the other ring.

Sonda po izumu ima glede na znane sonde opisane vrste znižano spodnjo mejo detekcije radona. Detektor v sondi je ves čas zaščiten pred ultravioličnimi žarki in so zato latentne sledi a delcev obstojne. Nameščanje sonde na terenu je preprosto prav tako pa tudi prenašanje majhne in kompaktne sonde na merilno mesto nazaj v laboratorij. Filter, ki deluje kot difuzijska ovira za zrak, je zaščiten pred mehanskimi poškodbami.The probe of the invention has, according to the known probes of the species described, a lower radon detection limit. The detector in the probe is protected against ultraviolet rays at all times and therefore the latent traces of the particles are stable. Installing the probe in the field is easy, as is the transfer of the small and compact probe to the measuring point back to the laboratory. The filter, which acts as an air diffusion barrier, is protected from mechanical damage.

Izum bomo v nadaljnjem podrobno opisali na osnovi izvedbenega primera ter pripadajočega načrta, ki prikazuje na sl.l sondo po izumu za merilnik koncentracije radona v zraku, ki je opremljena s trdnim detektorjem jedrskih sledi, v delnem osnem prerezu in sl.2 sondo s sl. 1 v prerezu II - II.The invention will now be described in further detail based on an embodiment and an accompanying plan showing in FIG. 1 a probe of the invention for a radon in air meter equipped with a solid nuclear trace detector in partial axial cross section and FIG. . 1 in section II - II.

Ogrodje sonde po izumu za merilnik koncentracije radona v zraku obstoji iz prizmatičnega, prednostno valjastega obroča R (sl. 1). Na enem koncu občutljivega prostora SV je znotraj obroča R nameščen detektor D jedrskih sledi, drugi konec prostora SV pa je zaprt s filtrom F. Obroč R je z obeh svojih koncev, ki se zaključujeta z robovoma El, E2, znotraj skoncema prizmatično razširjen do obeh obodnih prislonov Fl, F2. Ravnini prislonov Fl, F2 sta pravokotni na vzdolžno os A obroča R. V obroč R sta vstavljena filter F oziroma zaščitna ploščica PP, tako da se opirata na prislon Fl oziroma F2. Med filtrom F in ploščico PP se razteza sondin občutljivi prostor SV, ki je izpolnjen z aktivnim ogljem AC. Nad filter F je nameščena zaščitna mrežica PN. Mrežica PN je kongruentna s fitrom F in je od njega nekoliko manjša, a se še vedno sicer preko filtra F opira na prislon Fl. Na filter F in na mrežico PN se opira centrirni obroček CR1, ki sega do robu El obroča R. Na obroč R je odstranljivo pritrjen pokrov Cl sonde, npr. s pomočjo navoja T, tako da notranja tesnilka Sl pokrova Cl pritiska ob rob El in ob zunanji rob obročka CR1. Na ploščico PP se opira centrirni obroček CR2, ki sega do robu E2. Na obroč R je z njegove druge strani odstranljivo pritrjen pokrov C2, tako da njegova notranja tesnilka S2 pritiska ob rob E2 in ob obroček CR2. Detektor D je vstavljen v centrirni obroček CR2, npr tako da njegovi vogali Co segajo v izreze G v obročku CR2 (sl. 2). Detektor D, ki je npr. v obliki kvadratne ploščice s stranico 25 mm in iz alil diglikol karbonata, je torej obdan s tesnilko S2 in s ploščico PP, ki mu preprečuje dotik z aktivnim ogljem AC.The probe frame of the invention for the radon in air meter consists of a prismatic, preferably cylindrical ring R (Fig. 1). At one end of the sensitive SV space, a detector D is installed inside the ring R, and the other end of the SV space is closed by a filter F. The ring R is prismatically extended to both ends at its ends ending with edges El, E2. of flanges fl, F2. The planes of the flaps F, F2 are perpendicular to the longitudinal axis A of the ring R. The filter F or the PP protection plate are inserted in the ring R, so that they rely on the fl fl or F2. A probe-sensitive SV space filled with AC activated carbon extends between filter F and PP plate. A PN protective mesh is mounted above filter F. The PN mesh is congruent with the F filter and is slightly smaller than it, but still relies on the F backrest through the F filter. The filter ring F and the PN mesh are supported by the centering ring CR1, which extends to the edge El of ring R. The probe cover Cl is removably attached to ring R, e.g. by means of a T-thread so that the inner seal Sl of the cover Cl presses against the edge El and the outer edge of the ring CR1. The PP plate is supported by the CR2 centering ring extending to the edge E2. On the other side of the ring R, the cover C2 is removable, so that its inner seal S2 presses against the edge E2 and onto the ring CR2. The detector D is inserted into the CR2 centering ring, for example, so that its corners Co extend into the grooves G in the CR2 ring (Fig. 2). Detector D, which is e.g. in the form of a 25 mm square tile and allyl diglycol carbonate, it is therefore surrounded by a S2 seal and a PP tile which prevents it from contacting AC with activated carbon.

Prednostno valjast obroč R zunanjega premera 45 mm in notranjega premera 40 mm je izdelan tako kot pokrova Cl, C2 iz aluminija. Zaščitna ploščica PP je iz kovinske folije, katere debelina mora biti znatno manjša od dosega a delcev, ki jih sevajo radon in njegov potomci. Filter Fl mora biti iz hidrofobnega materiala; uporabi se lahko plast steklenih vlaken debeline npr. 0,15 mm. Zaščitna mrežica PN je kovinska in mora imeti odprt velik del svoje površine.Preferably, the cylindrical ring R of the outer diameter of 45 mm and the inner diameter of 40 mm is made in the same way as the aluminum caps Cl, C2. The PP protection plate is made of metal foil, the thickness of which must be significantly less than the reach of the particles emitted by radon and its progeny. The filter Fl must be of hydrophobic material; a layer of fiberglass with a thickness of e.g. 0.15 mm. The PN mesh is metallic and must have a large portion of its surface open.

Sondo po izumu se umeri s pomočjo kalibracijske prirave. Kot izvor radona v pripravim stekleni komori s prostornino 20 dm³ je predvidena zdrobljena uranova ruda. V komoro se vstavi sonde po izumu in z umerjeno scintilacijsko celico (s prostornino 0,2 dm³) se določi koncentracijo radona v komori.The probe of the invention is calibrated using a calibration device. Crushed uranium ore is envisaged as the source of radon in the prepared glass chamber with a volume of 20 dm ³ . The probes of the invention are inserted into the chamber and a radial concentration of the radon is determined with a calibrated scintillation cell (volume 0.2 dm ³ ).

Sondo se postavi na primeren predmet v prostoru, v katerem se želi določiti koncentracijo radona v zraku. Beleženje koncentracije radona se začne, ko snamemo pokrov Cl. Radon difundira skozi filter F v občutljivi prostor SV in se nabira na površini zrn aktivnega oglja AC. a delci radona in njegovih kratkoživih izotopov zadevajo detektor D in na njegovi površini zapuščajo sevalne poškodbe. Vstopanje radona v sondo zaključimo, s tem dajo ponovno pokrijemo s pokrovom Cl.The probe shall be placed on a suitable object in the room in which the radon concentration in the air is to be determined. The recording of radon concentration begins when the cover of Cl. Radon diffuses through filter F into a sensitive SV space and accumulates on the surface of AC charcoal grains. but the particles of radon and its short-lived isotopes hit the detector D and leave radiation damage on its surface. The entry of radon into the probe is terminated to cover again with the Cl cover.

V laboratoriju se iz sonde, ki se jo položi na pokrov Cl in se ji sname pokrov C2, vzame detektor D ter se ga kemijsko ali elektrokemijsko jedka, da postanejo sevalne poškodbe vidne sledi. Le-te se avtomatsko prešteje z merilnikom, seveda pa lahko tudi z optičnim mi-kroskopom. Obroč R z zaščitno mrežico PN, filtrom F in aktivnim ogljem AC se v sušilniku nekaj ur segreva pri temperaturi 120°C, s čimer se regenerira aktivno oglje AC. Sondo po izumu se pripravi za ponovno uporabo, s tem da se v obroček CR2 vstavi svež detektor D in sejo pokrije s pokrovom C2.In the laboratory, detector D is taken from the probe, which is placed on the Cl cover and the C2 lid is removed, and is chemically or electrochemically etched to cause visible radiation damage to the radiation. These are automatically counted with the meter, but of course they can also be counted with an optical microscope. Ring R with PN shielding, filter F and activated charcoal AC is heated for a few hours at a temperature of 120 ° C in the oven, thereby regenerating activated charcoal AC. The probe of the invention is prepared for reuse by inserting a fresh detector D in the CR2 ring and covering the session with a C2 cover.

Claims

Patent claim

An air radon concentration meter probe equipped with a solid nuclear trace detector in which a solid nuclear trace detector D is housed inside a prismatic ring R at one end of the probe sensitive SV space, the other end of which is closed by a filter F, characterized in that the filter (F) or the protective plate (PP) is perpendicularly extended to the circumferential stop (Fl, F2) perpendicular to the longitudinal axis (A) of the ring (R) and to which the ring (R) is extending inside the two-sided skeleton activated charcoal (AC) is placed between the filter (F) and the plate (PP); it is congruent to and smaller than the filter (F), but still retained on the filter (Fl) via the filter (F). (PN) to support the filter (F) and the mesh (PN) to the edge (El) of the ring (R) extending centrally (CR1) so that the cover (Cl) is removably attached so that its the inner seal (Sl) presses against the edge (El) and onto the ring (CR1) to hold the child ktor (D) centered ring (CR2) that rests on the tile (PP) and extends to the edge (E2) of the ring (R), and that the cover (C) is removably fastened so that its the inner seal (S2) presses against the edge (E2) and against the ring (CR2).