Plutonium Biokinetics in Human Body A. Luciani - Kit-Bibliothek - FZK

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HPGe crystals are produced in cylindrical shape (called coaxial) for the detection of high energy photons emitters (typically for energy higher then 100 keV): their large volume enhances the probability of interaction of the penetrating energetic photons with the crystal. For the detection of low energy photon emitters (typically for energy lower then 100 keV) planar shaped Germanium detectors are normally used because low penetrating photons have high probability of interacting, i.e. of being detected, already with thin Germanium crystals. At FZK coaxial and planar HPGe detectors are coupled: a coaxial detector is placed back to the planar detector in order that high energy photons cross the planar detector and can be detected by the coaxial detector. They can operate as a anticoincidence guard for background suppression purposes of high energy photons, in the same way as a phoswich detector. Both the detectors are cooled by means of a cooling rod with an extremity dipped in the liquid nitrogen contained in a dewar (see Figure 2.3.2). Figure 2.3.2 The basic elements of a coaxial and planar germanium detectors assembly with the dewar for the cooling. 2.3.1.3 Geometry Planar HPGe Dewar Coaxial HPGe Cooling rod Geometry is defined as the detector-source configuration, where the source is given by the distribution of photon emitting radionuclides in human body. The direct measurements systems can be divided in two different types: geometry independent and geometry dependent systems, often named whole body and partial body counters, respectively. Whole body counters can be efficiently used when radionuclides can be reasonably assumed as uniformly distributed within human body without particular concentration in organs and tissues. Typical photon emitters for which such system can be used are 137 Cs or 60 Co. The most common example of such geometry is the tilting chair, introduced for the first time by Marinelli [130]. The subject was sitting in a chair tilted about 45° backwards and a large scintillation detector was placed above the abdomen. The result of a measurement relates to the activity diffused within the whole body. Partial body counter is characterized by detectors positioned close to the subject, in order to view a specific organ or tissue. Therefore the results refer to the activity in such organ. The advantages of such geometry are a higher efficiency (the detector is closer to the source of radiation) and better detection capabilities (background radioactivity is shielded by the same subject body too). Geometry dependent configuration is extremely important in measuring low energy photons, where the efficiency of the system must be maximized. On 52 Liquid nitrogen
the other hand calibration and measurements must be carried out for each geometry distribution of radionuclides, making the use of such configuration particularly time spending. Other geometries were developed to a smaller extent. They are based on scanning devices where the detector, by moving above the subject, reveals the real distribution of the radionuclide within the body. Yet calibration procedures for such systems are hardly performed. In the case of direct measurements performed in the frame of the present work, transuranium elements must be detected in a contaminated subject. Low level activity and affinity for specific organs generally characterize contamination from transuranium elements. Therefore Partial body counters are more efficiently applied. According to their biokinetics, measurements of activity in liver and skeleton should be carried out. For cases of contamination via inhalation, particularly for insoluble compounds, measurements of activity in lung can be efficiently performed too. 2.3.1.4 Energy calibration The purpose of the energy calibration is to associate an energy value to the respective channel of a multichannel analyzer (MCA). Calibration sources are normally used with certified amounts of activity of one or more radionuclides. The detection of the emitted radiations provides a complex spectrum due to the different kind of radiation-material interactions, basically photoelectric, Compton and pair production interactions. For calibration purposes the full energy peak, due to the total energy absorption of the photon interacting with the detecting materials, is considered. The full energy peak is generally due to the photoelectric interaction but, at a lesser extent, Compton and, to a smaller extent, pair production interactions too can contribute to the full energy peak if the detector is large enough to virtually absorb all the secondary radiations produced through such effects [128]. Several methods have been developed for the automatic identification of the full energy peaks in the spectrum. One is based on second derivative analysis of the spectrum, as the second derivative of a smooth symmetric peak has a large negative excursion at the center of the peak. Other methods are based on filter functions that approximate the shape of the peak, and they operate by identifying those structures of the spectrum that can be assimilated to the filter function, mainly Gaussian. Even if these methods provide good results, a visual location procedure should be always performed for verification purposes. Particularly visual location is easily performed in energy calibration phase when simple spectra with few peaks from known calibrated sources are available. After the location of the full energy peak, its center (called centroid) is evaluated with different methods. Generally it can be calculated by means of a weighted mean of the counts of the peak channels. When the filter function method is applied, the centroid is calculated as a central parameter of the filter function. The possibility of locating single full energy peaks that don’t derive from a convolution of two or more peaks depends on the detecting system capacity of distinguishing full energy peaks of photons with different energy. This is quantified by the energy resolution of the system, based on the width of the full energy peak for the spectrum of a monoenergetic photon. The width is measured at half of the maximum and is named FWHM (Full Width Half Maximum) and the energy resolution (R(E 0)) is calculated as the ratio of FWHM by the photon energy E 0: R(E 0 ) = FWHM E 0 53 equation 2.3.1
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Forschungszentrum Karlsruhe in der
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Für diesen Bericht behalten wir un
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i ABSTRACT The biokinetic model pre
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ZUSAMMENFASSUNG Das von der Interna
Page 11 and 12: 1 INDEX OF CONTENTS INDEX OF SYMBOL
Page 13 and 14: 3 INDEX OF SYMBOLS Here a short glo
Page 15: Chapter 1 Introduction 5
Page 18 and 19: the duties of the Department for Ra
Page 20 and 21: adionuclide. Therefore only isotope
Page 22 and 23: stabilise the +4 oxidation state [1
Page 24 and 25: techniques adopted in the early pha
Page 26 and 27: present in spent and MOX reactor fu
Page 28 and 29: INTRAVENOUS INJECTION skin WOUND bl
Page 30 and 31: functions, defined as retained and
Page 32 and 33: the contamination event, of such as
Page 34 and 35: Table 1.3.2 Indicative 239 Pu detec
Page 36 and 37: The kinetics of Plutonium in the ki
Page 38 and 39: 1.4.2 COMMENTS ON THE ICRP 67 MODEL
Page 41: Chapter 2 Data and measurements 31
Page 44 and 45: Therefore the radiolysis process, m
Page 46 and 47: Recent technologic developments in
Page 48 and 49: eu(t) = 0.19e −0.272t + 0.023e
Page 50 and 51: function for each of the considered
Page 52 and 53: the minimum detectable activity of
Page 54 and 55: 2.2.2 AVAILABLE MEASUREMENTS Immedi
Page 56 and 57: Table 2.2.4 Daily fecal excretion o
Page 58 and 59: elements the spectral distribution
Page 60 and 61: The phoswich detector is based on t
Page 64 and 65: This quantity is normally expressed
Page 66 and 67: The peak is located in the region B
Page 68 and 69: To introduce the second quantity, t
Page 70 and 71: 117 cm 3 h -1 for the incoming and
Page 72 and 73: Figure 2.3.8 The Lawrence Livermore
Page 74 and 75: three detectors are used. Two detec
Page 76 and 77: Table 2.3.4 Efficiency factors of p
Page 78 and 79: • the necessity of performing mea
Page 80 and 81: Table 2.3.7 Impulses in the measure
Page 82 and 83: 2.4 ACTIVITY MEASUREMENTS IN BIOASS
Page 84 and 85: If more then one radionuclide is ma
Page 86 and 87: L A is the air layer in µgcm -2 ;
Page 88 and 89: The electrodeposition cell used for
Page 90 and 91: Table 2.4.1 238 Pu, 239 Pu and 241
Page 93 and 94: 3.1.1 MATHEMATICAL TOOLS 3.1.1.1 So
Page 95 and 96: calculating the amount of Plutonium
Page 97 and 98: 3.1.2 ANALYSIS OF THE ICRP 67 MODEL
Page 99 and 100: empirical curves given by Langham,
Page 101 and 102: the worst performance of the group.
Page 103 and 104: leave the total clearance from the
Page 105 and 106: Figure 3.1.4 shows that the use of
Page 107 and 108: 3.1.3 MODIFICATION OF ICRP 67 MODEL
Page 109 and 110: The structure of Polig’s skeleton
Page 111 and 112: Percentage daily urinary excretion
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of 0.693d -1 . The values of the F
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Percentage daily urinary excretion
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the basis of all the reference data
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Table 3.1.10 Transfer rates of the
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3.1.4 VERIFICATION OF THE OPTIMIZED
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Table 3.1.13 Intakes and percentage
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soft tissue ST2 soft tissue ST0 sof
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For the routine application of Mode
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excreted by individuals aged sixty
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Table 3.1.20 Exponents and coeffici
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tract [57] to consider a contaminat
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The sensitivity coefficients for th
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Sensitivity coefficients S i Figure
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transfer rates on the Plutonium uri
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Geometric standard deviations rangi
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3.2 APPLICATION OF THE OPTIMIZED MO
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lymph nodes, as in the LLNL phantom
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Americium in the lungs [Bq] 1000 10
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Daily urinary excretion [Bqd -1 ] 1
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long time is not yet described by t
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excretion that is one of the main i
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The comparison of model’s predict
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Americium in the lungs [Bq] 1000 10
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153 CONCLUSIONS The optimized model
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Annex Quantities used in Radiologic
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present. As the radiation weighting
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w R is the radiation weighting fact
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161 BIBLIOGRAPHY 1. Plutonium. W. K
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29. Nenot, J.-C. and Stather, J. W.
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55. International Atomic Energy Age
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81. Crowley, J., Lanz, H., Scott, K
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107. Hempelmann, L.H., Langham,W.H.
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137. Breitestein, B.D., Newton, C.E
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167. Harrison, J.D., Khursheed, A.,
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JOURNALS OWN PUBLICATIONS RELATED T
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177 ACKNOWLEDGEMENTS Special thanks
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Name: Andrea Luciani Date and place
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