Investigation of Background Radiation in an Industrial Area - Assignment Example

Investigation Of Background Radiation In An Industrial Area Student University ABSTRACT A measurement of the background radiation was carried out at the site and in the neighboring Holt Street Pinkenba. Laboratory survey meters were primarily used to take all the measurements required in and around the site location. For the purposes of this experiment a total of five measurements from five different points were taken. These included one measurement from outside the university, three measurements from Holt Street Pinkenba and a final measurement on the top 10cm soil at the site. The dose rate range obtained were as follows: at the point outside the university the average dose rate range was 14.0 (µ Sv), at the first measurement point taken on Holt Street Pinkenba the average dose rate range was 12.0 (µ Sv), at the second measure point on holt street the average dose rate range was 15.0 (µ Sv), at the third measurement point on Holt street the average dose rate range was 39.0 (µ Sv) and finally the top 10cm of the soil at the site had an average dose rate range of 93.0 (µ Sv). The average readings on the first three measurement points indicate normal radiation levels which can be attributed to natural causes. However the radiation on the last two measurement points that is the third point on Holt Street Pinkenba and the top 10cm soil layer of the site clearly indicates an unnatural spike in the average radiation levels which could be attributed to various factors such as industrial poisoning or human activity. (UNSCEAR) (1993) INTRODUCTION: Radiation is a naturally part of the universe since the beginning. There are over 60 known naturally occurring radio nuclides also known as radioactive elements. Nuclides are usually found in everything from the soil, air, water and even in humans. These elements are usually widely divided into three main categories that is Primordial which are usually long lived and usually date back to the beginning of the universe, Cosmogenic usually from extraterrestrial sources are formed as a result of cosmic ray interactions and human produced - enhanced or formed due to human actions such as industrialization. Radiation can also be categorized as ionized (nuclear) or not. The main difference between nuclear radiation and other types of radiation is that nuclear radiation has large amounts of energy that usually causes ionization. In the human body which has a large amount of water in the cells, the presence of radiation energy causes ionization of the water molecules. This ionization caused by nuclear radiation usually leads to molecular changes and the formation of chemical elements which usually lead to damaged chromosomes. In most cases the gravity of the nuclear radiation depends on the nature of this radiation that is whether it is alpha (α), beta (β), or gamma (γ). Other factors that determine the level of damage to the body cells include the energy of the radiation, the dosage, and time of exposure, the homogeneity of the dose and the nature of protection that one might be using. Normally when the dose rate levels are normal the effects are usually minimal. The human body is always irradiated both internally and from other external radiation sources such as primordial and cosmic radiation. Internally the most common radioactive element that is usually found in a person’s body throughout their lives is the K-40. Although harmful in large doses this particular element is usually relatively safe to humans. Other internal radiation generators include ingestion of food that might contain these radioactive elements and inhalation of air usually containing these radioactive elements such as radon. On the other hand, external sources which usually pose an elevated risk to humans can either be natural or artificial such as from radiation generators and other industrial applications such as the production of nuclear energy. ICRP (2000). Radiation is naturally occurring in all elements including the soil, air and the surrounding environment. In most cases the levels of naturally occurring radiation also known as background radiation are usually safe unless an environmental or artificial trigger causes a spike. The main factors that trigger the increase in the dosage levels of background radiation vary from place to place. In soil, the levels of naturally occurring radiation and other forms of radiation such as gamma radiation mainly depend on geological and the geographical conditions of a particular area. The geological and geographical nature of a particular environment dictates to a large extent the number of radionuclide found in a particular soil sample from that region. Geologically, the level of background radiation in Soils of a particular area is determined by the rock structure and the process of the soil formation. Consequently rocks formed metaphorically usually contain higher levels of background radiation compared to other types of rocks. Thus the soil, usually the top 30cm layer usually largely contributes to the overall background radiation of a particular area. Kocher DC, Sjoreen AL (1985) The most important nuclides that largely contribute to background radiation of the soil and the surrounding environment usually have a half-life comparable to the earth’s age. These nuclides usually include the Uranium-238, Thorium-232 and potassium-40 also written scientifically as 238U, 232Th and 40K. These elements are usually naturally occurring in the earth’s crust and they usually fall in the primordial radionuclide category. Normally uranium is the most visible of these elements because it decays to form radon. Radon is one of the most dangerous and common sources of background radiation as it usually radiates the soil and seeps into underground water sources causing radiation poisoning. Some places such as Cornwall found in the United Kingdom, already has very high levels of radon occurrence leading to large radiation dosages that make this place unfit for habitation or development of any kind. Other factors that contribute to the average dosage of radiation in soil include human activities such as industrial processes such as ore mining and whether the soil is under cultivation or not. In most cases the soil of a cultivated area usually has higher levels of radiation mostly due to the use of potassium fertilizer which injects the radioactive 40K into the soil, compared to virgin land. (UNSCEAR) (2000) This paper presents the background radiation level and the gamma absorption dose rate in a piece of land located in an industrial estate along Holt Street Pinkenba. The measurements used to conduct this experiment were obtained from five different sites along Holt Street Pinkenba. The values obtained from this experiment will be important in determining the efficacy of continuing with this particular project. MATERIALS AND METHODS The piece of land is found in an industrial estate along Holt Street Pinkenba. The monitor was suspended in air by a retort stand at one meter above the ground level at an open and undisturbed level ground surface. At each of the five chosen locations: outside the university, along Holt Street and on the actual site, three soil samples were taken to conduct the radiometric study. The bulk soil samples were collected in undisturbed, uncultivated level areas and away from roads or any high-rise buildings to prevent any external influence on the results. At each point, the total count for several minutes was recorded. Three successive readings were taken for each point. Each soil sample was collected from three subsamples in an area of approximately 100 m2 and up to a depth of 10 to 15 cm. The subsamples were mixed thoroughly and were collected in polythene bags. RESULTS AND ANALYSIS Figures (background in µ Sv). *102 Average (µ Sv) *102 Location. 0.10 15.0 17.0 14.0 Outside the University 0.09 10.0 17.0 12.0 Holt St (shown in the map attached with paper). 11.0 16.0 18.0 15.0 Holt St (shown in the map attached with paper). 0.27 44.0 46.0 39.0 Holt St (shown in the map attached with paper). 0.83 96.0 01.1 93.0 At the top (10cm) of soil. Results Discussion A total of five points were surveyed for background radiation. The radiation amounts obtained at each point is presented in table1. According to these results the amount of radiation seems to vary widely from the first reading outside the university at an average of 0.14 μSv, to the readings on Holt Street which range from 12 μSv, 15 μSv, 39 μSv and finally the highest reading was recorded at 93μSv. In all the 5 points surveyed the mean radiation amount was 34.6 μSv. The last readings taken from the top 10cm soil layer of the site indicate an elevated level of radiation which led to the conclusion that the environmental factors causing background radiation were more pronounced at this point. Dosage Rate: Radiation emitted by a radioactive substance is absorbed by any material it encounters. In this experiment we used the dosage conversion rates as follows: 238U, 232Th series and 40K with Dose Conversion Factors (k factors) of 0.39996, 0.54373, and 0.03995 nGy h-1 Bq-1 kg. Calculating the dosage rate: D = (0.427CRa+0.662CTh + 0.043CK) nGyh-1, The activity per cubic meter for local uncontaminated soil: Soil gravity = 1.6 x 103 kg m-3. Radiation amounts on the site=93.0 μSv Soil volume=1×1×0.1 =0.1m3 Radiation activity/ cubic meter μSv/m3 = 93.0÷0.1m3 =9.3 μSv/m3 Assuming the levels of 238U, 232Th series and 40K are the same in the sample soil For 40K =0.043×31 μSv =1.33μSv 238U =0.3996×31 μSv =12.4 μSv 232Th =0.662×31 μSv =20.46 μSv Given that the allowed activity in Queensland under the Radiation Safety Act are 1 x 102 Bq/g for Potassium 40, 1 x 101 Bq/g for 238U and its progeny when in secular equilibrium, and 1 x 100 Bq/g the calculated rates are within the required standards. Uncertainty analysis In the course of performing this experiment some variables whose accurate determination was beyond the scope of this paper were given arbitrary values. Assumptions made in the obtaining the results include: Assuming that background radiation consists of 50% cosmic and 50% terrestrial. Assuming that terrestrial radiation detected by your dose meter comes from the top 10cm of soil. Assuming that the soil contains equal amounts of 238U, 232Th series and 40K with Dose Conversion Factors (k factors) of 0.39996, 0.54373, and 0.03995 nGy h-1 Bq-1 kg. Also assume soil density of 1.6 x 103 kg m-3. CONCLUSION: The high background radiation observed in the area could be due the fact the site is located in an industrial area. Other possible factors affecting the background radiation of this area could be natural factors such as terrestrial and cosmic conditions. Further the nature of the soil in this area could also be affecting the background radiation of this area. There is thus a need for a comprehensive radiological study in the areas covered by this work to ascertain the radionuclide responsible for the elevated radiation dose rates. Bobiliography United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (2000). Sources, Effects and Risks of Ionization Radiation, New York: Publishers. ICRP (2000). Protection of The Public in Situations of Prolonged Radiation Exposure; ICRP Publication 82; Pergamon Press, Oxford. Ann. ICRP, 29(1–2). Kocher DC, Sjoreen AL (1985). Dose-rate Conversion Factors for External Exposure to Photon Emitters in Soil. Health Physics, 48: 193- 205. Speer J, Solberg T, Becker S (1981). Phase1: Assemblages and Migration of Uranium in Granitoid Rocks. Econ.Geol., pp. 110-120. Environmental Problems. Oxford, Clarendon Press, 51-55. (UNSCEAR) (1993) Sources and effect of Ionizing Radiation. New York: Publishers. Beaza, A, dei Rio M, Miro, C and Paniagua, J. (1994). Natural Radionuclide Distribution in Soils of Caceres (Spain) Environ. Radioactivity, 23: 19-37. Read More