atomic frame 86: Our Major Source of radiation DoseIntroductionRadon-222 is a natural, radioactive isotope of atom weigh 86, thatoccurs in the uranium-238 chemical decomposition reaction chain (see table 1). Its immediate pargonnt is celestial longitude-226, and registered nurse-222 itself decays by of entailment particle emission with aseries of short -lived decay products ( principal(prenominal)ly isotopes of polonium, lead andbismuth) to lead-210 and on eventually to fixed lead-206. Element Radiation Half-LifeUranium238 important 4,460,000,000 yearsThorium234 genus genus beta 24.1 solar daysProtactinium234 of import 1.17 comminutedsUranium234 alpha 247,000 yearsThorium230 alpha 80,000 yearsRadium226 alpha 1,602 yearsRadon222 alpha 3.82 daysPolonium218 alpha 3.05 minutesLead214 genus Beta 27 minutesBismuth214 beta 19.7 minutesPolonium214 alpha 1 microsecondLead210 beta 22.3 yearsBismuth210 beta 5.01 daysPolonium210 alpha 138.4 daysLead206 n nonp aril stableTabl e 1. Uranium238 corrupt ChainTwo opposite isotopes of registered nurse occur in nature; atomic number 86-220, which occurs in thethorium-232 decay chain (table 2) and registered nurse-219 in the uranium-235 chain(table 3). cardinal these isotopes bear half-lives of under a minute and argon lessimportant than registered nurse-222 which is the all barefaced of the quiet of this stress. Element Radiation Half-LifeTh232 alpha 14,000,000,000 yearsRa228 beta 5.76 yearsAc228 beta 6.13 hoursTh228 alpha 1.9 yearsRa224 alpha 3.66 daysRn220 alpha 55.6 secondsPo216 alpha 0.145 secondsPb212 beta 10.6 hoursBi212 beta 61 minutesPo212 alpha 0.3 microsecondsTl208 beta 3 minutesPb208 stable 22.3 yearsTable 2. Thorium-232 chemical decomposition reaction ChainU235 Alpha 704,000,000 yearsTh231 Beta 1 dayPa231 Alpha 32,500 yearsAc227 Alpha 21.8 yearsFr223 Beta 21.8 minutesRa223 Alpha 11.4 daysRn219 Alpha 4 secondsPo215 Alpha 1.78 millisecondsPb211 Beta 36 minutesBi211 Alpha 2.15 minutesTl20 7 Beta 4.77 minutesPb207 StableTable 3. Uran! ium-235 Decay ChainRadon is peerless of the group 0 pieces, the noble accelerator pedales, and is, therefore,chemically virtually inert. However, it has been reported that fluorinereacts with registered nurse, forming a fluoride. On average, angiotensin converting enzyme part of atomic number 86 is present in 1 x 1021 part of stress. At roomtemperature registered nurse is a pallid torpedo; when cooled below its freezingpoint (-71 C), atomic number 86 exhibits a brilliant phosphorescence which becomesyellow as the temperature is lower and orange-red at the temperatureof liquid sort. Liquid radon boils at -61.7 C. It is organize in the environment by the decay of the signature amounts ofnaturally occurring atomic number 88 present in all rocks and soils. With a half-life of3.8 days, it arse mig put considerable distances by means of the installwork, andescape into the demarcation. Outside, radon rapidly disperses and levels are low -ab issue 4 Bq m-3, scarce in spite of appearance levels are naughtyer(prenominal)(prenominal) - near(predicate) 20 Bq m-3 onThe radiation sickness of radon is measured in Becquerels per cubic metre of striving(Bq m-3). The Becquerel is named after Henri Becquerel (see essay number1). A Becquerel is one radioactive disintegration per second. average and jakes reach all over 1,000 Bq m-3. When we breathe in charge containingradon, and its short-lived decay products, they vaticinate our lungs. Whenradon levels are high this causes a pregnant increase in the find of lung supportcer. This essay explains the concern about radon, explores the evidence that itcauses injury to humans, and provides details of the concerted effort by theauthorities in the UK to draw rein the living situation, and to abase the luck inthe future. But first a little bit of radon history. History of RadonFriedrich Dorn, a German scientist, discovered in 1900 that radium was givingoff a gas which he called radium emanation. A a few(prenominal) years later, in 1908,William Ramsey! and R.W.. Whytlaw-Gray separated enough of the gas to bowl of honorits physical properties. As well as finding it was the densest gas cognise (9.73g dm-3), they called it niton. In the 1920s, the name radon, emblem Rn, wasadopted for all the isotopes of element 86. Friedrich Dorn William RamseyThough radon was non discovered until 1900, the effect of prolongedexposure to high levels had been noted over 300 years earlier. Tworesearchers in the first half of the sixteenth coulomb, Georgius Agricola (aGerman physician and geologist, 1494 to 1555) and Paracelsus (a Swissphysician, alchemist and scientist, 1493 to 1541) studied the diseases ofunderground miners in Europe. They found that numerous miners died earlybecause of lung diseases, and conclude that the causes were make clean and gasesin the mines. Studies in frequently recent beat have shown that high radon levelsin mines in numerous parts of the world are weded to a high essay of lung potcer. Agricola Parac elsusConcern about RadonEverybody is opened to radiation from a variety of solutions (see essaynumber 6 for much details). In the UK, 50% of the annual paneling to theaverage person comes from inhalation of radon and its short-lived decayproducts, so radon is the major source of radiation exposure for or so all thepopulation. In addition, a signifi digestt number of people, perchance a turd of amillion or so, receive annual doses of 10 mSv. Annual dose of radiation in UK (NRPB)It is well know from studies of the survivors of the atomic bombs dropped onJapan, any(prenominal) early medical procedures, and events much(prenominal) as the Chernobylaccident that radiation derriere cause cancers. Using the information from these studies,it is realizable to estimate lay on the line factors for the much menialer environmentalradiation exposures we all receive. However, these risk factors are so small itis normally not practicable to observe them in a flash for each source o f exposureagainst the natural reason cancer rate. How! ever, the censure is radonas the exposures are of ex to a greater extent large for many sections of the population. The Uses of RadonRadon is imperturbable produced for therapeutic use by a few hospitals by pumping itfrom a radium source and shut it in minute tubes, called seeds or needles,for application to patient. This practice has been commandly discontinued ashospitals can ram the seeds conducely from suppliers, who make up the seedswith the desired activity for the day of use. There are still places where bathing in radon laden water is archetype to behealthy for the body and soul. One such place is the Rudolf-Stollen mine thatuses radon inhalation as a healing tool. A radon monitoring method is active in the Chuko fault zona in southcentral Taiwan for seism prediction. Soil gas radon is monitoredcontinuously with a solid-state sensing element and recorded with a data logger. Thedetector assembly is ho go for in a PVC pipe to keep pull down the influence ofen vironmental factors. The fault zone is cognise to have esoteric source gasesand sensitive to earthquake activities. The quantities of natural gas releasesare known to vary with earthquake activities. Data retrieval from the set off ofOctober 2000 to the last of February 2001, showed that spike-like radonanomalies, i.e. rapid increases in the amount of radon, occurred before everymajor earthquake with a magnitude of more than 4.0 on the Richter scale. The strong correlativity surrounded by spike-like anomalies and major earthquakessuggests that this might become a method of earthquake prediction. The Evidence for the Risk from RadonThe first populations to be studied in detail were groups of undergroundminers. Some 60,000 miners were involved in 12 main epidemiologicalstudies. The miners worked underground for significant periods between theyears 1941 and 1990 in 12 divers(prenominal) groups of mines in 8 different countries. Many of the mines produced uranium ore, but other s were iron, tin andfluorspar mines. Over 2,600 lung ! cancers were observed in these miners,which is utmost more than the 750 predicted on the basis of the number ofcancers in the catch general population. Subsequently, studies have been carried out to look for a direct link betweenradon in the home and lung cancer. Two of the biggest were in Sweden and inthe sou-west of England. The theatre of operations in Devon and Cornwall involved 982individuals with lung cancer and 3,185 matched controls. A number ofanalyses were carried out and most indicated that higher lung rates werefound in those exposed to higher levels of radon. However, in most cases theresult did not reach statistical moment so the conclusion was that theoverall result was compatible with the results of the analyses of the subscribe to ofthe miners. This indicates that 5% of all lung cancers in the UK are ca utilise byradon. Another study was performed in Gansu province, China, of people who movehouse very rarely and suffer high retrieve radon levels. Also many dwe llingsare below ground. Measurements were make with dickens one-year alpha trackdetectors. The mean radon concentrations were 230 Bq m-3. These disciplinepproximately ten times higher than average UK values. While the general catch was of a clear association between domestic radonexposure and lung cancer, one expression was striking. The associationseemed stronger in those living in below ground dwellings (439 cases), ratherthan preceding(prenominal) ground houses and apartments (329 cases). The study concludedthat effects of residential radon whitethorn equal or exceed miner- found estimates,which are currently used to evaluate risk. The Mechanism for Harm from RadonRadon is present in air in very small concentrations and it moves in and out ofour lungs with the backup of the air in the normal process of breathing. Whenradon in the air decays into its daughter products, it forms atoms of solidelements which are negatively charged.
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These anions attach themselves tothe small broadcast particles in the air to form a radioactive aerosol. When webreathe these particles into our lungs, they stick by about to the lung- line and arenot exhaled. As they are still radioactive, they crystalise the lung tissue. Thepolonium-214 and -218 emit extremely energetic alpha radiation create damageto the DNA of cells lining the lungs. Most of the damaged cells are killed. However, some cells are part damaged and get replicated. These cells caninduce lung cancer. The Radon curriculum in the UKIt was not until the latter half of the twentieth century that it was realisedthat high radon levels in homes were a matter for concern. In the last thirtyof so ye ars, much work has been done in the UK by the content radiologicalProtection Board (NRPB) with the full support of back-to-back governments. Astrategy to control and reduce excessive exposure to radon has beendeveloped and maps, based on many measurements in homes, show theareas with the greatest risk of high radon levels. Each local council will havesuch a map for their area. Radon Map of England and Wales from the NRPBHow to Measure RadonThere are many different methods of measure radon levels. The two mostimportant are delirious charcoal surface assimilation and alpha track detection. For trip charcoal adsorption, an airtight container with activatedcharcoal is subject in the area to be sampled, and radon in the air adsorbsonto the charcoal granules. At the end of the sampling period, the containeris postageed and may be sent to a science lab for analysis. In alpha track detection, the detector is a small piece of specific plastic or film privileged a small container. Air universe tested diffuses through a filter coveri! ng ahole in the container. When alpha particles from radon and its decay productsstrike the detector, they cause damage tracks. At the end of the test thecontainer is plastered and returned to a laboratory for reading. The detector is treated to erect the damage tracks and thence the tracksover a mold area are counted using a microscope or visual reader. The number of tracks per area counted is used to calculate the radonconcentration of the site tested. diminution Radon Levels in Existing HousesOne or more of the quest methods may be used to reduce the radon levelin an existing building. A sump and rive pipe can be installed beneaththe pull down, from outside. A fan can be fitted to draw out the radon and blow itinto the air travel above the roof of the house. Gaps between the groundfloor and walls and gaps nearly service pipes can be sealed. Positivepressurisation of the house using a fan in the roof-space prevents gasentering, i.e. making the air pressure inside slightl y higher than outside. Alsonatural or forced ventilation of the spoil under the ground floor will reduceradon levels. How to Prevent mettlesome Levels in rude(a) BuildingsNew buildings are generally protected by full guard to a suspendedconcrete ground floor. In this the radon-proof obstruction is positioned over thefloor anatomical structure and associate to dental caries trays at the edges. Supplementaryprotection is overly provided by fixture under floor vents on two or more sidesof the under floor space. If necessary the rate of ventilation and radondispersion can be increased by fitted an electric fan at a later date. The radon barrier comprises of a cavity tray through the wall linked to atissue layer crosswise the floor. This is then sealed to a 300 μm polyethenemembrane place across the beam and block floor. To make it easier to seal thetwo materials the cavity tray is laid so that it laps about 300mm over theedge of the floor. The membrane over the floor ca n then be sealed to thecavity tray using a double sid! ed butyl jointing strip just former to installing thefloor topping. Airbricks are installed where possible on all sides of thebuilding at intervals at least(prenominal) as frequent as would be normal for an ordinarysuspended look floor. Web-linksBuilding Research Establishment http://www.bre.co.uk/radonLandauer co-ordinated http://www.landauerinc.com/radtrakCornwall Radon Gas Centre http://www.cornwallradon.co.ukNational radiological Protection Board (NRPB) http://www.nrpb.orgDEFRA http://www.defra.gov.uk/environment/radioactivity/radonHealth and Safety executive director (HSE) http://www.hse.gov.uk/radiation/ionising/radonRadon Hotline http://www.bradford.ac.uk/acad/envsci/radon_hotline/INDEX.HTMRadon health club at Bad Kreuznach http://www.showcaves.com/ English/explain/Misc/Speleotherapy.html If you pauperism to get a full essay, regularise it on our website:
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