A THESIS SUBMITTED TO THE DEPARTMENT OF PHYSICS, KHULNA UNIVERSITY OF ENGINEERING AND TECHNOLOGY, IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE. This is to certify that the thesis work entitled "Study on Probable Radionuclide Contents and Their Dose Determination in Sand, Soil and Water Samples collected from the Rupsha River, Khulna" by Tuhina Islam in the Department of Physics, Khulna University of Engineering and Technology, Khulna, Bangladesh.
LIST OF TABLES
Description Page 4.1 Activity concentration of daughter radionuclides of soil samples 77 4.2 Activity concentration and activity ratio of different radionuclides in soil 79 4.3 Activity concentration of daughter radionuclides of sediment samples 80 4.4 Activity concentration and activity ratio of different radionuclides in 82 4. Daughter radionuclides of water samples 85 4.6 Activity concentration of different radionuclides in river water samples 86 4.7 Activity concentrations of daughter radionuclides in well water.
Bar graph of the activity concentrations of daughters (212Pb,208Tl,228Ac) from 232Thin sediment samples.
Introduction
- General Introduction
- Radiation
- Radioactivity
- Background Radiation
- Radioactive Secular Equilibrium
- Radioactive Decay
- Basic Radiation Safety Criteria
- Motivation of the Present Study
- Layout of the dissertation
A number of naturally occurring radionuclides are primordial, that is, associated with the formation of the Earth. A major contribution to radioactivity in the body comes from the gaseous decay products of the radioactive series uranium and thorium, namely radon and thoron.
Theoretical Background
- Introduction
- Review of the Previous Work
- Theoretical Background of Radiation
- Gamma Emission
- Gamma Ray Spectroscopy
- Interaction of Radiation with Matter
Faanu et al., (2011), Activity concentrations of natural radionuclides 226Ra, 232Th and 40K in soil, rock, waste and tailings samples were measured by gamma spectrometry using high purity germanium detector. The conclusions of the results of these tests and measurements are given in this table.
Z Nucleons Photonuclear Reactions
Units of Radioactivity
The Becquerel (Bq) is the amount of radioactive material into which one atom is converted per second. It should be emphasized that although the Becquerel is defined in terms of the number of atoms transformed per second, it is not a measure of the rate of transformation. For many purposes, the Becquerel is a very small amount of activity, and multiples of the Becquerel are often used.
The curie, symbolized by Ci, is the unit for the amount of radioactivity that was used before the adoption of the SI and Becquerel units.
Radiation Dosimetry
The curie is the activity of that amount of radioactive material in which 3.7×1010 atoms are transformed per second. Before the universal acceptance of the SI units, radiation dose was measured by a unit called the rad (Radiation Absorbed Dose). One roentgen is defined as that amount of x-ray or gamma radiation that produces ions that carry one statcoulomb charge (or sign) per cubic centimeter of air at 00C and.
The utility of air Kerma can be extended to determining the radiation output at a given distance from a radiation source in terms of mGy per hour.
Relative Biological Effectiveness
The initial kinetic energy of the primary ionizing particles (e.g. photoelectrons, Compton electrons) produced by the interaction of the incident indirect ionizing radiation (e.g. X-rays, gamma rays, fast neutrons) per mass unit of the interacting medium is called Kerma. The air Kerma rate at 1 meter and the activity of the gamma source can be correlated using the exposure rate constant applicable to that source.
Quality Factor and Dose Equivalent
When the absorbed dose of any radiation is multiplied by the corresponding quality factor, the obtained quantity is known as dose equivalent. The value of the quality factor has been found to depend on the density of radiation-induced ionization in the tissue.
Effective Dose Equivalent
Biological Effects of Radiation
Because of the minimum dose that must be exceeded before an individual shows the effect, non-stochastic effects are also called threshold effects. The result of exposure to a carcinogen (substance that produces cancer, tobacco) increases the likelihood of the effect occurring. In this case, the increase in the probability of the effect is directly proportional to the dose.
Another important point regarding such stochastic effects as mentioned earlier is that the severity of the effect is not related to radiation dose.
The Interaction of Radiation with Cells
When the frequency of occurrence or percentage response of a stochastic effect is plotted against increasing dose to obtain a quantitative relationship, a linear dose-response curve (B) is observed in Figure 2.1. This stage lasts only a fraction of a minute (~10-16) of a second, during which energy is loaded into the cell and causes ionization. This stage lasts about 10-6 seconds, during which the ions interact with other water molecules, resulting in many new products.
This step lasts a few seconds, during which the reaction products interact with the cell's important organic molecules.
Acute and Chronic Exposure
The Somatic and Hereditary Effects of Radiation
Some fatal cancer risk estimates derived from the work of Throne et al. are shown in the following Table 2.8. For women, the number of radiation-induced cancers would be expected to be about 15 because of the additional risk of breast cancer (Casarett, 1968). This damage takes the form of changes, known as genetic mutations, in the hereditary material of the cell.
All available information leads to the conclusion that the likelihood of developing one of the.
Introduction
Study Area
Sampling Locations
Sample Collection and Preparation
The homogenized samples were then transferred to sealable cylindrical plastic containers of 7 cm height and 5.5 cm in diameter and the weights (after grinding) of the samples were recorded using an electric balance. After measuring the sample (260 ml), samples were then transferred to sealable cylindrical plastic containers of 8 cm height and 6.5 cm diameter. The weights of the samples were determined from the difference of weights of sample filled and empty container.
Radiometric measurements of these samples were also done at the Health Physics and Radioactive Waste Management Unit, INST, AERE, Savar, Dhaka.
Experimental Set up
Finally, the containers were filled with samples closed with caps, wrapped around their necks with thick vinyl tape and left for 30 days to achieve the secular equilibrium between gaseous and non-gaseous decay products of naturally occurring radionuclide series. The sample for this must contain several radionuclides, which have a good range of energies, i.e. the energies must range from the detectable minimum to the detectable maximum. However, it is necessary to subtract the background counts from the standard source counts to measure accurate counts of standard samples (Debertin and Helmer, 1988; Koddis et al.).
The high-purity germanium detector is widely used for the quantitative determination of radionuclide concentrations in radioactive waste samples.
Apparatus Used
The ADC is therefore a key element in determining the performance characteristics of the analyzer. Shielding the detector from ambient radiation is an absolute necessity for measuring low-level activity. Detector energy resolution (FWHM at 1332 KeV from 60C. Gamma rays): 2 KeV (specified by manufacturer).
To measure the sample's radionuclide, the liquid and solid samples were transferred to the plastic container and then placed on top of the detector.
Calibration of the Detector Parameters
The lower limit of detection (LLD) at the 95% confidence level is defined by Pasternak as: LLD Sb, where Sb is the standard deviation of the background. The standard deviation of the distribution is the square root of the mean value for a given sampling interval; S. D. The standard deviation is a measure of the distribution of a set of observations around their mean value.
The standard deviation of the net counting rate is 3.17) Where, = standard deviation of gross count rate.
Measurement Set-up
Calibration of the Detector
The radionuclide content and their activity levels of each sample were measured using a calibrated HPGe detector with an energy resolution of 2.0 KeV to 1.33 MeV of Cobalt-60 over a period of 10,000 seconds. Cps= Net counts per second= cps per sample-cps per background value E = Gamma energy counting efficiency. Where, Ns is the sample count measured at time Ts, and Nb is the background count measured at time Tb.
Absorbed Dose Rate
Outdoor Annual Effective Dose
Where, ARa, ATh and AK are the specific activities of 226Ra, 232Th and 40K respectively in BqKg-1.
External Hazard Index
Radiometric Measurement
From the gamma spectrometric analysis, the present study represents that three naturally occurring radionuclides (226Ra, 232Th and 40K) were determined in the soil, sediment and water samples. Activity concentration of natural 226Ra, 232Th and 40K, energy and efficiency calibration, lower limit of detection, radium equivalent activity, external hazard index, absorbed dose rate and annual effective outdoor dose in the samples were determined experimentally. The results obtained in the present study were also compared with other studies conducted at home and abroad.
Activity concentration in soil, sediment, river water, river well water and village well water samples collected from the Rupsha River bed and Rupsha area of Khulna District, Bangladesh were measured using a High Purity Germanium (HPGe) detector.
Radioactivity in soil samples
Since 40K is direct γ-emitter, so its activity concentration could be determined from its single photopeak at 1460 Kev.
Radioactivity in sediment samples
Radioactivity in water samples
- Radioactivity in Rupsha River water samples
- Radioactivity in tube-well water
The rest of the radionuclides were below the detection limit in almost all water samples. Therefore, the activity content of the water samples collected from the Rupsha River and the local Rupsha area in Khulna city did not show any significant evidence of radioactive enhancement.
Radiological Indices
The average value of the radium equivalent activity is 226.99 BqKg-1 for soil samples and 223.97 BqKg-1 for sediment samples. It is clear that the Radium equivalent activity coming from different regions shows some variations, which are probably related to the position of collected soil samples, sediment samples, water samples, transport processes, etc. This is important in selecting suitable soils, sediment, water and rice , not only for construction, but also for agricultural purposes to keep the radiation hazard to a minimum.
The mean value of the external radiation hazard index was 0.61 for the soil samples and 0.61 for the sediment samples, which was much less than the unit indicating the non-hazardous category of the samples.
Conclusions
S., 1999: Distribution of radionuclides in the river sediments and coastal soils of Chittagong, Bangladesh and evaluation of the radiation hazard, Applied Radiation and Isotope, vol 51, pp 747-755. ICRP, 1977: Recommendations of the International Commission on Radiological Protection, vol 1, no 3, published in the Annals of the ICRP, Pergamon Press, Oxford Publication. Paul, D., 2007: Lecture delivered on “Biological Effects of Ionizing Radiation” in the 49th Radiation Protection Training Course for Radiation Control Officers (RCOs) of Diagnostic X-ray Installations held at the Atomic Energy Center (AEC) Auditorium, BAEC, Dhaka , 09-10 July.
M., 1991: Fallout and natural radioactivity in the sand samples from coastal areas and in the rock samples from the northeastern part of Bangladesh, M.Sc.
