Natural Radioactivity

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AcknowledgementI wish to express my deep thanks and gratitude to my supervisors for all their help and support during the execution of this study.

Prof. Dr. Waleed Moslem Moslem

Prof. Dr. Ahmed. H. Korna

Associate Prof. Dr. Soad Saad Fares

Dr.Abdelelah Eltawil

Evaluation of Natural Radioactivity Around Some Fertilizer Factories in Egypt

Presented By / Fatma Abd_Elhamied Ahmed

Supervisors / Prof.Dr /Waleed Moslem Dr/Soad Fares Dr/Abdelelah Eltawil

OutlinesIAim of the workII Radioactive decayIIIConclusionIVExperimental TechniqueVResults and discussion

Aim of the work

Why we are interested in the assessment of natural radioactivity around fertilizer plants in Egypt ??

The analyses of radionuclide concentrations and activity level would provide us some important information to evaluate the extent, degree and the different pathways for the radioactive contamination to interrupt the natural system.

The objective of the present study is to detect the radionuclides and determine their concentration levels present in the wastes generated from the Abou_Zabal fertilizer factory, and to estimate their radiological impact on the public and the associated environment..

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The manufacture and the use of phosphate-based product scan lead to environmental contamination by direct contact with dust from fertilizers Also, during handling, packing and transporting fertilizers. Furthermore such measurements provide basic data for the estimation of the amount of radioactivity spread on agricultural land along with fertilizers.

Radioactivity and radioactive decay

Radioactive Decay

spontaneous disintegration of a nucleus into more stable nucleus, accompanied by emission of particles, electromagnetic radiation or both.

Types of Radioactive Decay Alpha Emission

Beta Emission

Positron Emission

Electron Capture

Gamma Emission

Gamma rays () are high-energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground energy state.

Units of Radiation Dose and ExposureRadioactivity is measured in unit of disintegration per second (dps).1 Becquerel is 1Bq = 1 dps1 Curie is 1Ci = 3 x 1010 dps

The current units designated by SI :Unit of Dose Equivalent is 1Sievert = 1 Sv (1 Joule/kg)Unit of Dose is 1 Gray = 1Gy (1 Joule/kg)1 Gy = 100 rad; 1 rad = 0.01 Joule/kg1 Sv = 100 rem; 1 rem = rad x quality factor

The amount of radiation is usually referred to as Dose. Dose is different from Exposure13

Actinium series

headed byuranium-235parentDaughter

Decay Series

Uranium series

The U-238 Series Represents almost 95% of the Radioactivity parentDaughter

Thorium series

headed by thorium-232parentDaughter

Transient Equilibrium

( parent > daughter)Secular Equilibrium

( parent >> daughter)

( parent daughterNo EquilibriumDecay Equilibrium

Transient equilibrium The daughter activity starts to increase, achieves a maximum, and then decreases to attain the same rate of decay as the parent. The total activity of the sample is then the sum of the two radionuclide activities.Secular equilibrium The number of daughter radionuclides starts to build up at the rate of the decay of the parent, and after about 7 daughter half-lives equilibrium will be reached and the activity of the daughter will become equal to the activity of the parent.

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Photoelectric effect

The photo electric effectPair production and Annihilation

Compton scatteringBefore interaction

After interaction

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Incoming photonCollides with electron

Electron is ejected from atom

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Natural radioactivity

Natural RadioactivityRadioactive elements can be categorized asPrimordial present even before or ever since the existence of the Earth.Cosmogenic - formed as a result of cosmic ray interactions.

Anthropogenic - enhanced or formed due to technology, human activities.

EXPERIMENTAL TECHNIQUE

Soil sampling and sample preparation23 Soil samples were collected at random positions from several different locations around Abou Zabal

Abou- Zabal fertilizer factory location and soil samples location

For gamma-ray spectrometry, each sample was transferred to a plastic container of 250 cc capacity and sealed for About four weeks.The soil samples were grinded and sieved through a 2 mm nylon mesh to ensure homogeneity.These samples were oven-dried at 110 C for 24 h to remove moisture

Four weeks to reach secular equilibrium between 226Ra and 228Ra, and their progenies, to prevent the escape of airborne 222Rn and 220Rn from the samples 24

Instrumentation and Instrument Set UpCR-39 detectorHPGe-Gamma Ray SpectrometryX-Ray Diffraction (XRD)

The arrangement of the HPGe detector with the lead shieldHPGe-Gamma Ray SpecrometryA hyper pure germanium coaxial detector ( N-type and 40 % relative efficiency) of a vertical configuration that is mounted on a 30 liter liquid nitrogen Dewar for germanium crystal temperature control.Radioactivity from room background sources was reduced by surrounding the detector with a cylindrical lead shield of about 10 cm thickness

Block diagram of Gamma ray Spectrometer set up.Spectroscopy amplifier which is an integral part of the low noise system.Analog-to-digital converter (ADC) which is intended to offer the ultimate in resolution, stability and linearityMultichannel analyzer with 8192 channels and with counting capacity of 228counts per channelData acquisition, display and analysis of gamma-ray spectra were performed using Genie 2000 software

CalibrationIn this study, the gamma reference source containing mixed radionuclides named NG3 with gamma ray lines was chosen for energy calibration.

Gamma-ray energy (KeV)Radio NuclidesActivityBqRelative intensities59.54241Am3.41x10335.9088.03109Cd1.5x1043.7122.0657Co5.03x10285.60165.86139Ce6.07x10279.90279.20203Hg8.42x10281.46391.70111Sn1.99x10364.97514.0185Sr1.95x10395.70661.662.68x10385.10898.0488Y4.15x10393.701173.2460Co3.12x10399.971332.5060Co3.12x10399.981826.0688Y4.15x10399.20

Gamma -ray lines of NG3 reference source

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Energy Calibration and Peak IdentificationGamma spectrum for the NG3 Radionuclide Mixture Stander Source .

Efficiency Calibration of HPGe DetectorThe principle of radiation detection is generally to measure an output pulse for each radiation event that interacts within the active volume in a detector.

Relative efficiency as function of gamma-ray energy forThe HPGe detector used in the current work.

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The observed relationship between the published gamma-ray energies and their centroid channel number from the NG3 source used for the energy calibrationThe linear relationship between the gamma-ray energies and channel numbers is given by Energy (keV) = 1.53keV + 0.422 x Channel Number

CR-39 detector

A schematic diagram of the sealed-cup technique in soil sampleThe concentration and exhalation rate of radon can be made using CR-39 detectors Each 25 g of these soil samples was transferred to separate plastic cans (8 cm diameter 14 cm height) and was then sealedEach sample was equipped with a CR-39 plastic track detector (1.5 cm 1.5 cm)

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X-Ray Diffraction (XRD)

Schematic Diagram of X-Ray diffractometer (XRD).

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Results and dissection

Soil Samples Spectra

Background-subtracted gamma-ray spectrum associated with decays from radionuclides detected from a sample no. S1 .

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Activity Concentration of Radionuclides in Soil Samples:The activity concentrations of the investigated samples were calculated by using equation A = (CSP)net / I x Eff x M 1 % K = 313 Bq.kg-1 of 40K 1ppm U = 12.35 Bq.kg-1of 238U 1 ppm Th = 4.06 Bq.kg-1of 232Th Conversion from Activity Concentration to Elemental Concentrations (ppm):

The level of natural background radiation varies depending on the location, and in some areas the level is significantly higher than average (sample S0 inside the factory). Where ATh and AK are the activity concentration of 232Th and 40K respectively in Bq/kg.

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Activity concentrations of 238U, 226Ra, 232Th and 40K for all soil samples.SampleAU(Bq/Kg)U(ppm)ARa(Bq/Kg)Ra( ppm)Ath(Bq/Kg)Th(ppm)Ak (Bq/Kg)K %S0462.60 44.4633.28514.00 48.0646.2637.00 0.199.1419.00 1.170.07S1410.85 39.4829.09456.50 42.6841.0925.93 0.136.40104.80 1.040.40S2359.10 34.5126.38399.00 37.3135.9120.07 0.104.96138.80 0.910.54S3325.70 31.3026.91407.12 38.0736.6423.67 0.125.85146.70 0.930.57S4332.20 31.9226.25415.25 38.8337.3722.67 0.125.60148.44 0.940.57S5324.10 31.1525.60405.12 37.8836.4619.82 0.104.90162.10 0.920.63S6316.00 30.3723.42395.00 36.9335.5516.70 0.094.12161.30 0.900.62S7289.10 27.7822.57361.38 33.7932.5217.48 0.094.32131.31 0.820.51S8278.59 26.7721.41327.75 30.6429.5015.56 0.083.84156.50 0.740.60S9264.30 25.4020.25310.94 29.0727.989.91 0.052.45130.90 0.710.51S10250.01 24.0320.65294.13 27.5026.4712.73 0.063.14142.00 0.670.55S11254.99 24.5026.01277.00 25.9027.0012.30 0.063.04147.20 0.630.57S12321.14 30.8615.05305.85 28.6027.5314.55 0.073.59146.60 0.690.57S13185.80 17.869.11265.43 24.8223.8917.00 0.094.20146.60 0.600.57S14112.50 10.8114.53225.00 21.0420.2514.55 0.073.59146.59 0.510.57S15179.42 17.2414.49224.27 20.9720.1813.63 0.073.37164.50 0.510.64S16178.83 17.1914.74223.54 20.9020.1220.00 0.104.94160.00 0.510.62S17181.93 17.4810.46173.27 16.2015.599.79 0.052.42156.10 0.390.60S18129.15 12.415.63123.00 11.5011.0711.79 0.062.91179.88 0.280.69S1969.45 6.676.02105.23 9.849.479.37 0.052.31174.70 0.240.67S2074.35 7.149.0887.47 8.187.878.00 0.041.98160.80 0.200.62S21112.07 10.7710.72106.73 9.989.619.45 0.052.33166.80 0.240.64S22132.30 12.719.16126.00 11.7811.349.37 0.052.31174.70 0.290.67Mean241.06 23.1718.30283.87 26.5325.6416.15 1.453.99146.36 6.90.57Max462.6033.28514.0046.2637.009.14179.880.69Min69.455.6387.477.878.001.9819.000.07

(A,B,C,D):238U,226Ra 232Th and 40K activity concentrations for all soil samples measured in the current work, together with the weighted mean activity concentrations for overall results. The worldwide mean values reported in the UNSCEAR report 2000 are also shown for comparison. ABCD

The worldwide mean values reported in the UNSCEAR report 2000 are also shown for comparison38

Radium Equivalent Activity

Calculation of Air Absorbed Dose Rate Dab

Effective Dose Rates H E(indoor) , H E(outdoor)

1) Where: AU, ARa, ATh and AK are the activity concentrations of 238U, 232Th and 40K, respectively. The Raeq index it has been assumed that 370 Bqkg-1 of 238U, 259 Bqkg-1 of 232Th and 4810 Bqkg-1 of 40K produce the same gamma doses2) Where: AU, ATh and Akare in Bqkg-1 , The conversion factors used to compute absorbed gamma dose rate (Dab) in air per unit activity concentration in Bq/kg (dry weight) corresponds to 0.462 nGy/h for 226Ra, 0.604 nGy/h for 232Th and 0.042 nGy/h for 40K

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SampleRaeq (Bq/Kg)Dab (nGy|\h)HE outdoor(mSv\y)HE indoor(mSv\y)S0568.37261.240.321.28S1501.65231.380.281.14S2438.39202.590.250.99S3452.27208.910.261.02S4459.09212.110.261.04S5445.95206.230.251.01S6431.30199.590.240.98S7396.48183.290.220.90S8362.05167.610.210.82S9335.20155.270.190.76S10323.27149.710.180.73S11305.92152.370.190.75S12337.94156.450.190.77S13301.02139.300.170.68S14257.09119.100.150.58S15256.43118.940.150.58S16264.46122.370.150.60S17199.2992.640.110.45S18153.7171.650.090.35S19132.0861.720.080.30S20111.2952.080.060.26S21133.0962.130.080.30S22152.8571.320.090.35Mean318.23147.740.180.72Max568.37261.240.321.28Min111.2952.080.060.26

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External and Internal Hazard Index Hex ,Hin

The measurement of radon exposure and the internal hazard index is given as follows

Gamma Index I

Alpha Index (I)

Excess Lifetime Cancer Risk (ELCR)ELCR = HE x DL x RFwhere HE, is the annual effective dose equivalent, DL is the duration of life (70 years) andDL and RF the risk factor (Sv-1), fatal cancer risk per Sievert.

SampleIGammaIalphaHexHinELCR x10-3S03.812.571.542.931.12S13.372.281.362.590.99S22.952.001.182.260.87S33.052.041.222.320.90S43.092.081.242.360.91S53.012.031.212.300.89S62.911.981.172.230.86S72.671.811.072.050.79S82.441.640.981.860.72S92.261.550.911.750.67S102.181.470.871.670.64S112.221.500.891.700.65S122.281.530.911.740.67S132.041.330.811.530.60S141.741.130.691.300.51S151.741.120.691.300.51S161.801.120.711.320.53S171.360.870.541.010.40S181.060.620.420.750.31S190.910.530.360.640.26S200.770.440.300.540.22S210.920.530.360.650.27S221.050.630.410.750.31Mean2.161.420.861.630.63Max3.812.081.542.931.12Min0.770.440.300.540.22

Correlation Studies

Linear regression of the activity concentrations of 238U versus 226Ra for all soil samples.

Linear regression of the elemental activity concentrations of 232Th versus 238U for all soil samples

Linear regression of the activity concentrations of 226Ra versus 40K for all soil samples.Linear regression of the activity concentrations of 232Th versus 40K for all soil samples.

SampleElemental Activity Concentrations (PPm) Ratio ofTh/UActivity Concentrations (Bq/Kg) Ratio of Ra/UActivity Concentrations (Bq/Kg) Ratio ofTh/KActivity Concentrations (Bq/Kg) Ratio of Ra/KS00.271.251.9527.05S10.221.270.254.36S20.191.230.142.87S30.221.230.162.78S40.211.280.152.80S50.191.280.122.50S60.181.370.102.45S70.191.300.132.75S80.181.240.102.09S90.121.240.082.38S100.151.150.092.07S110.120.930.082.04S120.241.650.102.09S130.462.360.121.81S140.251.250.101.53S150.231.250.081.36S160.341.230.131.40S170.231.340.061.11S180.521.770.070.68S190.381.420.050.60S200.220.780.050.54S210.220.810.060.64S220.251.110.050.72Mean0.241.290.182.98Max0.522.361.9527.05Min0.120.780.050.54

Radon Concentration (222Rn) The radon and radium concentration of all soil samples calculated from the following formula equation

The effective radium concentration of the soil samples can be calculated from the formula

The mass, surface exhalation rate of the sample for the radon is given by

where M is the mass of samples (0.025 kg), A is the area of the cross section of cylinder in m2 (A=2 r2, r is the radius of the cylinder equal to r = 0.011 m), h is the distance between the detector and the top of the solid sample in m that equal to (0.095 m), is the number of tracks per cm2, K is the radon diffusion constant that equals to 1.23 x 10-3 track/cm2 h/Bq/m3 at the radius of cylinder (maintained above) and Te denotes, by definition to the effective exposure time given by46

The radon 222Rn and radium 226Ra concentrations in all soil samples.SampleMass exhalation *10-8 (Bq/kg day-1)Surface exhalation *10-6 (Bq/kg day-1)Effective radium concentration (Bq/kg)S0122.9481.8210.46S1109.1972.679.29S295.4363.518.12S397.3864.818.28S499.3266.108.45S596.9064.498.24S694.4862.888.04S786.4457.537.35S878.3952.176.67S974.3749.506.33S1070.3546.825.98S1166.2544.095.64S1273.1548.696.22S1363.4942.255.40S1453.8235.824.58S1553.6435.704.56S1653.4735.584.55S1741.4427.583.53S1829.4219.582.50S1925.1716.752.14S2020.9213.921.78S2125.5316.992.17S2230.1420.062.56Mean67.9045.195.78Max122.9481.8210.46Min20.9213.921.78

Correlation between mass exhalation of 222Rn and 238U in all selected samples.

Correlation between surface exhalation rate of radon and 238U in all selected samples

Theoretical Interpretation to Estimate the Activity Concentrations of 222Rn in the air with the Activities of 226Ra Contents in Soil Samples Measured by Gamma Spectrometer.Determination the Activity Concentration of 226Ra Inside the SoilCRa(n)= C(En) B(En)/ m.f.t.P(En)Determination of the Radioactive Concentration of 222Rn in airGs (n)= Fr . .C Ra(n)Determination the Concentration of 226Ra in Vegetables CP = An .C Ra(n)Determination the Annual Effective Dose Resulting from Inhalation of Radon Gas or Vegetables Consumption Hp =Cp .Ip . DCF

Where ..49

SampleActivity concentration of 226Ra inside the soilCRa (Bq/Kg)concentration of 222Rn inside the soilGs(n) (Bq/m3)concentration of 222Rn gas in AirCa(n)( Bq/m3)Concentration of 226Ra in vegetablesCp(Bq/Kg)Annual effective dose from 222Rn inhalationHp(sv/y)Annual effective dose from 226Ra consumptionin vegetablesHp (sv/y)S0514.00 48.0683268263.68466.3547.35838.39S1456.50 42.6873953234.18414.14486.12745.37S2399.00 37.3164638204.69361.97424.89652.35S3407.12 38.0758625.64185.65328.3385.37592.3S4415.25 38.8359795.28189.35334.85393.05603.98S5405.12 37.8858337.64184.74326.69383.47589.43S6395.00 36.9356880180.12318.53373.89574.87S7361.38 33.7952038164.79291.41342.06526.52S8327.75 30.6450145.75158.79280.82329.62507.62S9310.94 29.0747573.82150.65266.41312.72481.94S10294.13 27.5045001.89142.51252.01295.81456.25S11277.00 25.9045898.47145.35257.03301.71465.2S12305.85 28.6057805.65183.05323.71379.98584.11S13265.43 24.8233443.55105.9187.28219.84340.82S14225.00 21.042025064.13113.4133.11209.07S15224.27 20.9732294.88102.27180.85212.29329.35S16223.54 20.9032189.76101.93180.26211.59328.3S17173.27 16.2032748.03103.7183.39215.26333.88S18123.00 11.502324773.62130.18152.81239S19105.23 9.8412501.62139.5970.0182.18131.69S2087.47 8.1813382.14542.3874.9487.97140.48S21106.73 9.9820172.442563.88112.97132.6208.29S22126.00 11.782381475.41133.36156.54244.66Mean283.87 26.5343391.50137.41242.99285.23440.17

Element and Mineralogical Composition of Phosphate Soil Analyzed by X-ray Diffraction

A & B Figure X-ray diffraction diagram of phosphate soil from different sits. A=Apatite, CFA= Carbonate Fluor apatite, CH = Carbonate hydroxyapatite. F=Fluorapatite, HA=Hydroxyapatite, Q = Quartz.. A B

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ConclusionOur result shows that the 226Ra, 232Th and 40K activity concentration in the soil samples decrease as the sampling distance from the fertilizer factory increases.

This may be due to contribution of fallout of phosphate ore dusts generated during the processing of the phosphate ore in the immediate vicinity of the fertilizer factory.

Thank you for your attention

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