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

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excretion at long time (after 2,000 days post intake) predicted by the model still underestimates the experimental results. In this time range the subject’s excretion is characterized by the enhancement that made this case a particularly interesting contamination event. The Americium burden in lungs at long time, due to the 241 Pu decay, overestimates the experimental findings in the scenario 1 (up to a factor 4) and underestimates them in the scenario 3 (by about a factor 12). Therefore such fraction of Americium seems to behave in the respiratory tract with an absorption type ranging from the type S (the absorption type for the father Plutonium in the scenario 1) and the type M (the reference absorption type for Americium adopted in the scenario 3). In order to improve model’s predictions of Americium lung retention, the absorption parameter determining the Americium retention in lungs at long time (s t) was varied in the range from 0.0001 d -1 (the reference value for absorption type S) to 0.005 d -1 (the reference value for absorption type M). It was found that model’s predictions for the Americium burden in lungs significantly improve their agreement with the experimental findings at long time if a value 0.001 d -1 is assumed for s t (Figure 3.2.7). The other absorption parameters (s p and s pt) were set to the default values for the absorption type S. Such modification may have a reasonable physiological explanation: • The Americium just formed after Plutonium decay behaves at short time in the respiratory tract as the father (Plutonium default values of s p and s pt for the absorption type S are therefore assumed); • At longer time Americium own specific metabolic characteristics gets more and more evident (therefore the value of s t has reasonably a value between the default values for S and M absorption types). Therefore such approach can be considered more realistic in comparison to the assumption of an Americium ingrowth with all the same absorption parameters of the father Plutonium (as usually assumed by ICRP and here in the scenario 1) or with its own default absorption characteristics (as in case of a direct inhalation). On the basis of the previous assumed value of s t for Americium ingrowth from 241 Pu decay, the intake of 241 Am directly inhaled was evaluated as 9 kBq. The intakes of all the other involved radionuclides are easily evaluated by means of the their ratio at the moment of the intake. The relating value of the F target function calculated on lung measurements is 50% and 1% of the value calculated in case of the scenarios 1 and 3 respectively. This quantitatively points out the improvement of the model’s predictions of Americium lung retention when the absorption parameters are changed according to the previous assumptions. The model’s predictions for the urinary excretion of Plutonium are equal to those ones evaluated in case of the scenario 1 (Figure 3.2.4) because only the default s t absorption parameter for Americium ingrowth was modified and no parameter relating to Plutonium was modified. Model’s predictions for the lymph nodes burden of Americium were compared to few available measurements too and a good agreement was found even for this set of data. At conclusion of the analysis of the most reliable measurements for modelling and testing purposes, a good agreement of model’s predictions with the experimental data was obtained. Furthermore the considered modification (the change of the s t absorption parameter for Americium ingrowth from Plutonium decay) seems to be reasonably acceptable from a physiological point of view too. However the enhancement of Plutonium urinary excretion at 144
long time is not yet described by the considered assumption in the previous model. A specific paragraph is dedicated to this issue (see paragraph 3.2.5). Americium in the lungs [Bq] 1000 100 10 Measurements Model total retention Directly inhaled 241Am 241 241 241Am Am from from Pu 241Pu decay decay 241 Am 1 10 100 1000 10000 100000 Days post intake Figure 3.2.7 Measurements and model predictions for Americium activity retained in lungs based on s t = 0.001 d -1 for the lung absorption of 241 Am ingrowth from 241 Pu decay. It should be pointed out also that according to the approach followed by some participants to the IAEA intercomparison exercise, where this case of contamination was already proposed [123], a mixture of soluble (M) and insoluble compounds (S) could be also considered. In the frame of the present work it was found that an inhaled compound formed by about 30% of Plutonium of S type (as in Scenario 1) and 70% of M type (as in Scenario 2) determine a retention of Americium in the lungs in a very good agreement with the experimental findings. Unfortunately it was also observed that the consequent urinary excretion of Plutonium would not agree with the available measurements: as the excreted Plutonium is mainly given (about 70%) by the inhaled compound of type M, the urinary excretion curve will not significantly differ from the plot in Figure 3.2.5, relating to scenario 2. 3.2.4 ANALYSIS OF THE SET OF LESS RELIABLE MEASUREMENTS By adopting the assumptions based on the lung burden of Americium and the urinary excretion of Plutonium, the data set formed by the less reliable groups of measurements was also analyzed. 145
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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
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1 INDEX OF CONTENTS INDEX OF SYMBOL
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3 INDEX OF SYMBOLS Here a short glo
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Chapter 1 Introduction 5
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the duties of the Department for Ra
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adionuclide. Therefore only isotope
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stabilise the +4 oxidation state [1
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techniques adopted in the early pha
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present in spent and MOX reactor fu
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INTRAVENOUS INJECTION skin WOUND bl
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functions, defined as retained and
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the contamination event, of such as
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Table 1.3.2 Indicative 239 Pu detec
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The kinetics of Plutonium in the ki
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1.4.2 COMMENTS ON THE ICRP 67 MODEL
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Chapter 2 Data and measurements 31
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Therefore the radiolysis process, m
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Recent technologic developments in
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eu(t) = 0.19e −0.272t + 0.023e
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function for each of the considered
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the minimum detectable activity of
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2.2.2 AVAILABLE MEASUREMENTS Immedi
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Table 2.2.4 Daily fecal excretion o
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elements the spectral distribution
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The phoswich detector is based on t
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HPGe crystals are produced in cylin
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This quantity is normally expressed
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The peak is located in the region B
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To introduce the second quantity, t
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117 cm 3 h -1 for the incoming and
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Figure 2.3.8 The Lawrence Livermore
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three detectors are used. Two detec
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Table 2.3.4 Efficiency factors of p
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• the necessity of performing mea
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Table 2.3.7 Impulses in the measure
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2.4 ACTIVITY MEASUREMENTS IN BIOASS
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If more then one radionuclide is ma
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L A is the air layer in µgcm -2 ;
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The electrodeposition cell used for
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Table 2.4.1 238 Pu, 239 Pu and 241
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3.1.1 MATHEMATICAL TOOLS 3.1.1.1 So
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calculating the amount of Plutonium
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3.1.2 ANALYSIS OF THE ICRP 67 MODEL
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empirical curves given by Langham,
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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
Page 113 and 114: of 0.693d -1 . The values of the F
Page 117 and 118: the basis of all the reference data
Page 119 and 120: Table 3.1.10 Transfer rates of the
Page 121 and 122: 3.1.4 VERIFICATION OF THE OPTIMIZED
Page 123 and 124: Table 3.1.13 Intakes and percentage
Page 125 and 126: soft tissue ST2 soft tissue ST0 sof
Page 127 and 128: For the routine application of Mode
Page 129 and 130: excreted by individuals aged sixty
Page 131 and 132: Table 3.1.20 Exponents and coeffici
Page 133 and 134: tract [57] to consider a contaminat
Page 135 and 136: The sensitivity coefficients for th
Page 137 and 138: Sensitivity coefficients S i Figure
Page 139 and 140: transfer rates on the Plutonium uri
Page 141 and 142: Geometric standard deviations rangi
Page 147 and 148: 3.2 APPLICATION OF THE OPTIMIZED MO
Page 149 and 150: lymph nodes, as in the LLNL phantom
Page 151 and 152: Americium in the lungs [Bq] 1000 10
Page 153: Daily urinary excretion [Bqd -1 ] 1
Page 157 and 158: excretion that is one of the main i
Page 159 and 160: The comparison of model’s predict
Page 161 and 162: Americium in the lungs [Bq] 1000 10
Page 163 and 164: 153 CONCLUSIONS The optimized model
Page 165 and 166: Annex Quantities used in Radiologic
Page 167 and 168: present. As the radiation weighting
Page 169 and 170: w R is the radiation weighting fact
Page 171 and 172: 161 BIBLIOGRAPHY 1. Plutonium. W. K
Page 173 and 174: 29. Nenot, J.-C. and Stather, J. W.
Page 175 and 176: 55. International Atomic Energy Age
Page 177 and 178: 81. Crowley, J., Lanz, H., Scott, K
Page 179 and 180: 107. Hempelmann, L.H., Langham,W.H.
Page 181 and 182: 137. Breitestein, B.D., Newton, C.E
Page 183 and 184: 167. Harrison, J.D., Khursheed, A.,
Page 185 and 186: JOURNALS OWN PUBLICATIONS RELATED T
Page 187 and 188: 177 ACKNOWLEDGEMENTS Special thanks
Page 189 and 190: Name: Andrea Luciani Date and place
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Plutonium Biokinetics in Human Body A. Luciani - Kit-Bibliothek - FZK

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