COMPARING LUNGS, LIVER AND KNEE MEASUREMENT GEOMETRIES AT VARIOUS TIMES POST INHALATION OF 239Pu AND 241Am

COMPARING LUNGS, LIVER AND KNEE MEASUREMENT GEOMETRIES AT VARIOUS TIMES POST INHALATION OF 239Pu... ABSTRACT In-vivo measurement of Pu/241Am in workers is carried out by placing suitable detector above lungs, liver and skeleton, as major fraction of Pu/Am is transferred to liver and skeleton, after its retention in entry organ. In this work, committed effective dose (CED) corresponding to minimum detectable activity for Type M and Type S 239Pu/241Am deposited in these organs are presented and a monitoring protocol of organ measurement giving lowest CED at different time intervals post inhalation is described. We have observed, for Type M compounds, lung measurement is most sensitive method during initial days after exposure. Liver measurement yields lowest CED between 100 and 5000 d and beyond that bone measurement gives lowest CED. For Type S compounds lung measurement remains most sensitive method even up to 10 000 d post inhalation. This study will be useful for the assessment of CED due to internally deposited 239Pu/241Am in the workers. INTRODUCTION Plutonium is handled in fuel fabrication facilities and reprocessing plants, where, in spite of stringent safety measures, internal contamination of workers due to plutonium cannot be ruled out(1). The internally deposited 239Pu, other isotopes of plutonium and 241Am can be evaluated by in-vivo measurements, excreta monitoring or a combination of these techniques(2). Initially, 239Pu and 241Am are deposited at the route of the entry and then gets translocated to other organs depending on the chemical and physical form. In working areas of Pu/Am handling facility, inhalation is the most common route of intake to the worker. Inhaled activity is deposited in respiratory tract and a fraction is absorbed to blood and/or transferred to alimentary tract/lymph nodes through particle transport. Absorption to blood depends on the solubility of the inhaled material which is classified as fast (Type F), moderate (Type M) and slow (Type S) categories. Human respiratory tract model (HRTM) provides details of deposition and clearance from various parts of respiratory tract(3). In case of moderately soluble plutonium (e.g. nitrates and all unspecified compounds)(2, 4) and all americium compounds, the deposited lung activity is absorbed into the blood with a biological half-time of ~140 d. But, oxides of 239Pu and 241Am embedded in plutonium matrix behaves as lung absorption Type S(5) and are retained in the lungs for years which are subsequently absorbed to the blood with a biological half-time of ~7000 d. There have been a number of updates to the International Commission on Radiological Protection (ICRP) publication 66 HRTM based on new data involving experiments on animals and humans. The revised HRTM is published in ICRP Publication 130(6). In revised HRTM, deposition in parts of extrathoracic region, rates of particle transport and absorption to blood have been modified. According to ICRP publication 67 biokinetic model, 80% of systemic activity of plutonium and americium is transferred to liver and skeleton. In case of plutonium, ~30% of systemic activity is transferred to the liver. Based on various studies(7–11) carried out after ICRP 67 publication, an improved biokinetic model for plutonium is developed by Leggett et al.(12), which is being incorporated in new ICRP publication(13). In this improved biokinetic model of plutonium, initially 60% of systemic activity is transferred to liver and 30% to the skeleton. The bioassay predictions obtained with new model gives better fits to the measured data. Therefore, measurement of 239Pu and 241Am deposited at the organs associated with the route of entry (lungs, wound, stomach) and organs where it is transferred and retained for long time (skeleton and liver) is an important aspect of radiation protection program. The measurement of 239Pu and 241Am long time post exposure can be carried out by measuring activity deposited in the skeleton and liver. The skeleton measurement is performed by placing detector above knee or skull(14). Total skeleton activity is estimated using the fraction of skeleton mass in knee or skull. In this work, we have calibrated an actinide lung monitor using Lawrence Livermore National Laboratory (LLNL) thorax phantom for 241Am deposited in the lungs and liver. The calibration factor for 241Am, deposited in bone is taken from our results on knee phantom measurement carried out under International Atomic Energy Agency (IAEA) inter-comparison exercise(15). The biokinetic model of 239Pu and 241Am has been solved to evaluate its retention in lungs, liver and skeleton at a different time post inhalation. For direct measurement, to identify which measurement geometry will give lower intake and committed effective dose (CED) estimate, internal dose is estimated at various days post inhalation using lung, liver and skeleton measurement data of 241Am at MDA level. Intake and CED values were calculated first using ICRP-66 HRTM, ICRP-30 GI tract model(16) and ICRP-67 biokinetic model(4), then intake values were calculated using revised ICRP-130 HRTM(6), ICRP-100 human alimentary tract model (HATM)(17) and new plutonium biokinetic model published by Leggett et al.(12). The results of this study will be useful to identify the organ whose in-vivomeasurement will give lowest intake and CED at various days post inhalation. MATERIALS AND METHODS Detection system An array of three 70 mm dia. and 25 mm thick n-type HPGe detectors (Make: Canberra Eurisys S.A.) installed inside totally shielded steel room is used for the measurement of gamma/X-rays of Pu/241Am and U(18, 19). The three detectors of the array are enclosed in a 20 cm diameter hollow copper cylinder, positioned at 120° apart. Their centers lie on the circumference of 10 cm dia. and each has 0.8 mm thick carbon window. The total area of all the three detectors is 115.4 cm2. The signals from each detector are acquired separately through three multi-channel analyzer cards, which can be summed into a single spectrum as per the requirement. Inter Winner gamma ray spectrometry software is used for analyzing the spectra. The full width at half maxima of each detector is ~0.6 keV at 59.5 keV photon energy. Figure 1 shows actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. Figure 1. View largeDownload slide Actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. Figure 1. View largeDownload slide Actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. The efficiency and MDA The in-vivo monitoring system used in this study is calibrated with realistic LLNL thorax phantom(20) for activity deposited in the lungs and liver. The LLNL phantom is a physical thorax phantom based on a Caucasian man with mass 76 kg and height 177 cm(21). This phantom has a simulated rib cage, removable lungs, heart, liver, major trachea and bronchial lymph nodes. Four numbers of 100% muscle equivalent chest overlay plates are available with the phantom. The overlay plates were used for placement over phantom for the representation of individuals with different tissue thicknesses above chest and liver. Thickness of the overlay plates above lungs varies from 1.77 to 6.18 cm and thickness above liver varies from 1.33 to 5.76 cm. For measurement of activity deposited in lungs, detectors are placed tangentially to suprasternal notch covering maximum lungs area and for liver measurement; detectors are placed near right sub-costal area covering liver. The counting efficiency, K (cps Bq−1) of the detection system at X cm of chest wall thickness (CWT) for photon energy, Ei is estimated using the following equation: KX,Ei=C−CbkgAT (1) where A is the amount of activity (Bq) present in the lungs or liver of LLNL phantom, C is the total counts in energy region. Cbkg is the background counts recorded with blank lung sets in respective energy region and T is the measurement time. Measurement geometry is kept same for the phantom as well as for the person. The minimum detectable activity (MDA) of the system at 95% confidence level is evaluated using the following equation(22): MDA=(4.65σb+2.7)KT (2) where σb is the standard deviation in the gross counts of reference energy band of an uncontaminated person measured in appropriate geometry, K is the counting efficiency (cps Bq−1); and T is the counting time.The efficiency and MDA of the detection system for 241Am in the skeleton is evaluated from our results of IAEA inter-comparison exercise. Under this exercise the leg phantom distributed with an unknown amount of 241Am was received by the laboratory. The measurement of activity was carried out with phoswich detector and results were reported to IAEA. Later on, the actual amount of 241Am distributed in the knee phantom was published(15). Using this value, efficiency and MDA of the phoswich detector is evaluated. To evaluate efficiency of HPGe detector, measurements were carried out for 241Am deposited in the knee of a worker with phoswich and HPGe array and counts obtained by both system were compared to derive efficiency of HPGe detector. The results were also verified with Monte Carlo simulation of knee voxel phantom(23). Method of in-vivo measurement of 239Pu and its intake estimation The in-vivo measurement of 239Pu can be carried out by detecting L X-rays of its daughter 235U which emits 13.5, 17.2 and 20.2 keV photons with a total yield of 4.6%. These U-L X-rays are not energetic enough to get transmitted through lungs and liver overlay tissues. Therefore, the detection limit of in-vivo monitoring system for the measurement of 239Pu using its X-ray energy is ~2000 Bq, which is quite high compared to relevant reference level. Therefore, direct measurement of Pu in various organs is carried out using 241Am as a tracer and by measuring its 59.5 keV gamma-rays having 36% yield. Then using following method amount of 239Pu present in the organ or its intake is estimated. In the case of inhalation of 239Pu, if 241Am is measured in the lungs then it is assumed that 241Am is embedded in plutonium matrix and follows biokinetics of plutonium in the lungs(5). Using 239Pu/241Am ratio obtained from radiochemical analysis of fecal/workplace sample, and measured activity of 241Am, total amount of 239Pu present in the lung is estimated. The 239Pu/241Am ratio depends on burn-up of the fuel and also the time elapsed after the purification of 239Pu. Typically the 239Pu/241Am ratio found for high burn-up fuel is ~3(24). Therefore, in this work for the evaluation of 239Pu, from MDA level of 241Am measured in the lungs of worker 239Pu/241Am ratio of three is used. Then using ICRP-78 methodology intake of plutonium is estimated. When 241Am is measured in liver or skeleton, the 239Pu/241Am ratio cannot be used directly for the estimation of 239Pu deposited in the measured organ. This is because, according to ICRP, plutonium and americium follow their own biokinetics and deposition in liver and skeleton will be different than actual radionuclide composition of this material at the time of intake. Therefore, from measured 241Am in liver and knee, first intake of 241Am is estimated, then this value is multiplied by the 239Pu/241Am ratio to evaluate 239Pu intake(25). The measured 241Am in lungs, liver and skeleton can be residual activity from intake of 241Am as well as due to in-growth from 241Pu (T1/2 = 14.35 y) decay. The 241Pu activity can vary from 84 to 97% of the total plutonium activity in irradiated nuclear fuel(26). In-growth of 241Am can take place in the organ where activity is deposited after intake as well as systemically. The ICRP publication 130 recommends that if 241Am is born systemically then americium biokinetics should be used in place of plutonium for dosimetric calculations. If measured 241Am without in-growth correction is used for plutonium dose estimation it will lead to overestimation of intake and CED values. Hence, first in-growth of 241Am from 241Pu should be evaluated using isotopic composition of inhaled material at the time of intake, then, after its correction, 241Am values should be used for intake and CED estimation(26). Computer software used for computations of organ contents of 239Pu and 241Am A computer program based on Birchall’s algorithm(27) for compartmental analysis with recycling was developed and standardized(28, 29). This program can be used for biokinetic studies of various radionuclides for any input parameters. The method incorporates the compartmentalized forms of biokinetic model of a selected radionuclide. It provides a solution for the complete compartmental model and can compute the daily urinary excretion and the amount of radioactivity retained in any organ at any time for both acute as well as for chronic intake by inhalation and ingestion. The transfer rate constants of plutonium and americium, d−1, (defined as the fractional flow per unit time between different compartments) for the HRTM, the GI tract and the biokinetic models were taken from ICRP Publication 66(3), 78(2) and 67(4), respectively. The above-mentioned methodology was applied to compute 239Pu and 241Am content in different organs for inhaled particle of 5 μm activity median aerodynamic diameter (AMAD) of absorption Type M and Type S for acute intake. For the purpose of the quality assurance of the software used, 239Pu and 241Am content in lungs and its daily urinary excretion were computed for inhaled activity of 5 μm AMAD particle size of absorption Types M and S and compared with the values given in the ICRP publication 78.(2) An excellent agreement was observed. Also, we have estimated retained fractions after inhalation of Type M and Type S plutonium compounds in lungs, liver and skeleton at different time by solving the improved plutonium biokinetic model developed by Leggett et al.(12) incorporated with ICRP-130 revised HRTM(6) and ICRP-100 HATM(17). RESULTS AND DISCUSSION Table 1 shows the efficiency and MDA of HPGe array based in-vivo monitoring system, obtained with 241Am distributed in the lungs and liver of LLNL phantom for various overlay thicknesses above these organs. The MDA of the system is calculated using average value of background counts obtained in energy region of the interest of 30 non-radiation workers monitored for 3000 s in the lungs, liver and knee measurement geometries. The mean value of muscle equivalent CWT (MEQ-CWT) for Indian worker is 1.77 ± 0.31 cm(30). The basic LLNL phantom is having MEQ-CWT of 1.77 cm (which is equivalent to mean MEQ-CWT for Indian worker) and liver overlay thickness of 1.33 cm. Therefore, efficiency and MDA obtained with the basic LLNL phantom was used for the interpretation of measurement results in terms of intake and CED. The efficiency and MDA of the system are 2.60E-03 cps Bq−1 and 6.0 Bq for 241Am in lungs and 5.55E-03 cps Bq−1 and 4.0 Bq for 241Am in liver with basic LLNL phantom. Table 1. The efficiency and MDA of HPGe array at 59.5 keV photon energy of 241Am distributed in the lungs and liver of LLNL phantom for the measurement time of 3000 s at various overlay thicknesses. Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Table 1. The efficiency and MDA of HPGe array at 59.5 keV photon energy of 241Am distributed in the lungs and liver of LLNL phantom for the measurement time of 3000 s at various overlay thicknesses. Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 The total surface area of lungs and liver of the LLNL phantom is ~2109 and 946 cm2, respectively(31). It is observed that liver geometry gives better efficiency and lower MDA compared to lungs geometry. This is because, detector covers larger fraction of liver area than lungs and lower overlying tissues thickness above liver (1.33 cm) as compared to lungs (1.77 cm). Table 1 shows that with increase in the thickness of overlay tissues above lungs and liver of the phantom, efficiency of the system decreases and MDA increases. Decrease in the efficiency is due to higher attenuation of photons with increase in the overlay thickness. Empirical equations have been derived to estimate efficiency at various overlay thicknesses for lungs and liver geometry. Efficiency (Y) of HPGe detector based system at 59.5 keV photon energy of 241Am in lungs and liver with x cm overlay thickness can be evaluated by the following equation: Y(HPGe,lung,59.5)(x)=0.00474e(−0.34x) (3) and equation: Y(HPGe,liver,59.5)(x)=0.00863e(−0.33x) (4) respectively. The efficiency and MDA of the HPGe system for 241Am in the knee were 4.5E-3 cps Bq−1 and ~3.0 Bq, respectively. Considering that knee contains 9.3% of the total bone mass(23), 30 Bq of the 241Am in skeleton can be measured using this system. The above results show that MDA of in-vivo monitoring system for 241Am deposited in lungs, liver and skeleton of worker having average physique are 6.0, 4.0 and 30.0 Bq, respectively, for measurement time of 3000 s. Using these values, intake and CED at various days post inhalation is evaluated to determine sensitivity of the techniques used for the measurement. Cross talk between 241Am in lungs, liver and skeleton It is known that 241Am gets transferred to liver and skeleton as time passes after inhalation, which interferes in estimating correct amount of activity deposited in lungs and liver. The cross talk between lungs, liver and skeleton (ribs) should be calculated before estimating amount of activity in any of these organs. The cross talk between liver and lungs for the system, used in this work, is estimated using LLNL phantom for 241Am. These values between lungs and liver is found to be <8% of the counting efficiency of that organ(32, 33). Also Lobaugh et al. have carried out extensive study for estimation of cross talk between lungs and other organs (ribs, lymph nodes and liver) in thorax region. Analysis of their results show that contribution to the measured organ due to activity in the source organ is <5% of the counting efficiency for the source organ(34). Therefore, if in-vivo measurement of 241Am is conducted long time after intake, cross talk from the activity deposited in other organs in the thorax region should be considered before estimating activity. Estimation of CED using ICRP-66 HRTM, ICRP-30 GI tract model and ICRP 67 biokinetic model of plutonium and americium at MDA level of 241Am measured in lungs, liver and skeleton Tables 2 and 3 give intake and CED calculated at MDA level of 241Am measured in the lungs, liver and skeleton at various days since inhalation for absorption Type M and Type S compounds respectively. The dose coefficients of these radionuclides have been taken from ICRP-68(35). If intake of Type M 241Am occurs one day prior to lung measurement, 2.8 mSv CED can be estimated. The CED estimated using MDA level of 241Am measured in liver and skeleton after one day of intake is ~8.6 and 107.0 mSv, respectively. This shows that lung measurement of 241Am is the most sensitive method for Type M compounds during initial days post inhalation. The estimated CED values at 100 d after inhalation for 241Am measured in lungs, liver and skeleton were 8.01, 4.93 and 53.2 mSv, respectively. Thus, measured 241Am deposited in the liver yields lower CED than lung measurement data at 100 d post inhalation intake. Table 2. The intake and CED from MDA equivalent Type M 241Am measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. Table 2. The intake and CED from MDA equivalent Type M 241Am measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. Table 3. The intake and CED from MDA equivalent 241Am embedded in Pu oxide (Type S) and measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Table 3. The intake and CED from MDA equivalent 241Am embedded in Pu oxide (Type S) and measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Table 2, therefore, indicates that post 100–5000 d, liver measurement becomes sensitive, while post 5000 d, skeleton measurement becomes sensitive as it yields lowest CED among three geometries. From Table 3, it can be observed that for 241Am embedded in Type S plutonium matrix, lung geometry yields lowest CED even up to 10 000 d post inhalation compared to other two geometries. If measurements are conducted up to initial 200 d post inhalation, estimated CED will not be more than 1.6 mSv. Intake and CED of absorption Type M and S 239Pu calculated from MDA equivalent 241Am measured in lungs, liver and knee of a worker at various days post inhalation intake are given in Table 4 and Table 5 respectively. In the case of Type M 239Pu, lung monitoring of 241Am is the most sensitive technique during initial days after inhalation up to 100 d. About 9–10 mSv of CED from measured 239Pu can be estimated if measurements are conducted within a week after inhalation. Table 4. The intake and CED of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 4. The intake and CED of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 5. The intake and CED of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 5. The intake and CED of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 4, therefore, indicates that post 100 d, measurement of activity deposited in the liver becomes most sensitive method, while post 5000 d, skeleton becomes sensitive as it yields lowest CED out of the three geometries. From Table 5 it can be observed that for Type S 239Pu lung geometry yields lowest CED even up to 10 000 d post inhalation compared to other two geometries. If lung measurements are conducted for 241Am up to initial 200 d post inhalation, estimated 239Pu CED will not be more than 4.8 mSv. Effect of revised ICRP-130 HRTM, ICRP-100 HATM and Leggett’s systemic biokinetic model of Plutonium on intake estimation For inhalation of Type M and S 239Pu, the ICRP-130 revised HRTM, ICRP-100 HATM and revised ICRP-67 systemic biokinetic model of plutonium published by Leggett et al. is integrated together and solved for default parameters of reference radiation worker. These models were used to calculate retention fractions in lungs, liver and skeleton at various days after inhalation. ICRP has not published dose coefficient using revised biokinetic models, therefore, only intake values were estimated. CED can be calculated by multiplying these intake values with new dose coefficients whenever it will be available. The retained values in lungs, liver and skeleton is compared with those obtained with earlier models and are presented in Figures 2 and 3 for absorption Type M and S 239Pu, respectively. It is observed from Figure 2 that with previous models, initially lower amount of systemic activity is transferred to liver than skeleton. In revised model, larger fraction of plutonium is transferred to liver than skeleton in initial days. At 1 000 d post inhalation skeleton deposit exceeds liver deposit. For Type M 239Pu after 100 d since inhalation, liver deposit exceeds lung deposit. Therefore, measurements carried out after 100 d post inhalation of Type M 239Pu, the liver measurement gives lower intake. Figure 3 shows, for Type S 239Pu lung retention is similar with both models up to 600 d, afterwards lung retention is higher with the new model. The higher lung retention obtained with new model than previous model is likely to results into higher lung dose. The initial deposition in liver and skeleton are lower with revised model than earlier. In revised model for Type S 239Pu, liver content is higher than skeleton up to 4 000 d, after that skeleton content is higher. For Type S compounds of plutonium, lung retention is higher than liver and skeleton even up to 10 000 d. Figure 2. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type M 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 2. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type M 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 3. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type S 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 3. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type S 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Intake values at MDA level of activity measured in lungs, liver and skeleton based on revised ICRP models are estimated and these values are given in Tables 6 and 7 for absorption Type M and Type S 239Pu, respectively. It is observed from Table 6 that for Type M 239Pu, with revised model also, in-vivo measurement of lungs is most sensitive technique up to 200 d post inhalation, after that liver measurement is the most sensitive method. After 5 000 d, knee/skeleton measurement result yields lowest intake. In case of Type S 239Pu lungs measurement remains the most sensitive method even up to 10 000 d post inhalation compared to other two geometries. Table 6. Estimated intake of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Note: Intake values are not given if it exceeds MBq. View Large Table 6. Estimated intake of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Note: Intake values are not given if it exceeds MBq. View Large Table 7. Estimated intake of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake of 239Pu. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Note: Intake values are not given if it exceeds MBq. View Large Table 7. Estimated intake of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake of 239Pu. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Note: Intake values are not given if it exceeds MBq. View Large Estimation of intake and CED from in-vivo measurement after acute inhalation intake of 241Am We have used a case study to show that follow-up measurement data of various geometries such as lungs, liver and skeleton should be used for intake and CED calculations. Kathren et al.(36) have described a case involving a person who was exposed while examining an old 370 MBq sealed 241Am source on 1 February 1996. Long-term follow-up measurement (up to 6 years) of 241Am deposited in lungs, liver and skeleton of this worker was carried out. The authors(36) have interpreted this material primarily being Type S perhaps mixed with Type M material. Based on this interpretation, they have estimated intake as 6.3 kBq. This case was also listed in IDEAS internal dosimetry database; Case Id 206(37). The intake and CED estimated by IDEAS are 7.2 kBq and 116.0 mSv, respectively. We have estimated retention factors for lungs and liver and calculated CED using ICRP 78 methodology (dose coefficient and biokinetic model) from lungs and liver measurement data, assuming material behaving as absorption Type M and S. The calculated CED assuming Type M material using lung and liver data are 1753.0 and 70.0 mSv, respectively. If inhaled material is assumed as Type S, estimated CED using lung and liver data are 54.9 and 705.6 mSv, respectively. Though the lung data support Type S behavior, liver measurement supports Type M behavior of inhaled compound which indicates it to be a mixture of Type S and Type M materials. Therefore while estimating CED, importance should be given not only to lungs measurement data but also to other organ measurement data. Using integrated modules for bioassay (IMBA)(38) software, best estimated intake and CED for this case are 7.1 kBq and 128.0 mSv, respectively. CONCLUSIONS The CEDs corresponding to MDA equivalent activity measured in lungs, liver and knee of worker for absorption Type M and Type S 239Pu and 241Am are estimated. The efficiency and MDA of HPGe array based in-vivo monitoring system for 241Am deposited in lungs, liver and skeleton were estimated using LLNL phantom and IAEA leg phantom. Retained fractions in lungs, liver and skeleton at different time post inhalation have been estimated using HRTM, GI tract model and ICRP-67 systemic model of 239Pu and 241Am. Retained values in these organs were compared with those obtained from the improved biokinetic model for plutonium developed by Leggett et al. incorporating ICRP-130 revised HRTM and HATM. 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Dose coefficients for intake of radionuclides by workers. ICRP Publication 68 . Ann. ICRP 4 ( 24 ), ( 1994 ). 36 Kathren , R. L. , Lynch , T. P. and Traub , R. J. Six-year follow-up of an acute 241Am inhalation intake . Health Phys. 84 ( 5 ), 576 – 581 ( 2003 ). Google Scholar CrossRef Search ADS PubMed 37 IDEAS Internal Contamination Database. Available on http://www.sckcen.be/ideas/. 38 Birchall , A. , Jarvis , N. S. , Peace , M. S. , Riddell , A. E. and Battersby , W. P. The IMBA suite: integrated modules for bioassay analysis . Radiat. Prot. Dosim. 79 ( 1–4 ), 107 – 110 ( 1998 ). Google Scholar CrossRef Search ADS © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

COMPARING LUNGS, LIVER AND KNEE MEASUREMENT GEOMETRIES AT VARIOUS TIMES POST INHALATION OF 239Pu AND 241Am

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Abstract

ABSTRACT In-vivo measurement of Pu/241Am in workers is carried out by placing suitable detector above lungs, liver and skeleton, as major fraction of Pu/Am is transferred to liver and skeleton, after its retention in entry organ. In this work, committed effective dose (CED) corresponding to minimum detectable activity for Type M and Type S 239Pu/241Am deposited in these organs are presented and a monitoring protocol of organ measurement giving lowest CED at different time intervals post inhalation is described. We have observed, for Type M compounds, lung measurement is most sensitive method during initial days after exposure. Liver measurement yields lowest CED between 100 and 5000 d and beyond that bone measurement gives lowest CED. For Type S compounds lung measurement remains most sensitive method even up to 10 000 d post inhalation. This study will be useful for the assessment of CED due to internally deposited 239Pu/241Am in the workers. INTRODUCTION Plutonium is handled in fuel fabrication facilities and reprocessing plants, where, in spite of stringent safety measures, internal contamination of workers due to plutonium cannot be ruled out(1). The internally deposited 239Pu, other isotopes of plutonium and 241Am can be evaluated by in-vivo measurements, excreta monitoring or a combination of these techniques(2). Initially, 239Pu and 241Am are deposited at the route of the entry and then gets translocated to other organs depending on the chemical and physical form. In working areas of Pu/Am handling facility, inhalation is the most common route of intake to the worker. Inhaled activity is deposited in respiratory tract and a fraction is absorbed to blood and/or transferred to alimentary tract/lymph nodes through particle transport. Absorption to blood depends on the solubility of the inhaled material which is classified as fast (Type F), moderate (Type M) and slow (Type S) categories. Human respiratory tract model (HRTM) provides details of deposition and clearance from various parts of respiratory tract(3). In case of moderately soluble plutonium (e.g. nitrates and all unspecified compounds)(2, 4) and all americium compounds, the deposited lung activity is absorbed into the blood with a biological half-time of ~140 d. But, oxides of 239Pu and 241Am embedded in plutonium matrix behaves as lung absorption Type S(5) and are retained in the lungs for years which are subsequently absorbed to the blood with a biological half-time of ~7000 d. There have been a number of updates to the International Commission on Radiological Protection (ICRP) publication 66 HRTM based on new data involving experiments on animals and humans. The revised HRTM is published in ICRP Publication 130(6). In revised HRTM, deposition in parts of extrathoracic region, rates of particle transport and absorption to blood have been modified. According to ICRP publication 67 biokinetic model, 80% of systemic activity of plutonium and americium is transferred to liver and skeleton. In case of plutonium, ~30% of systemic activity is transferred to the liver. Based on various studies(7–11) carried out after ICRP 67 publication, an improved biokinetic model for plutonium is developed by Leggett et al.(12), which is being incorporated in new ICRP publication(13). In this improved biokinetic model of plutonium, initially 60% of systemic activity is transferred to liver and 30% to the skeleton. The bioassay predictions obtained with new model gives better fits to the measured data. Therefore, measurement of 239Pu and 241Am deposited at the organs associated with the route of entry (lungs, wound, stomach) and organs where it is transferred and retained for long time (skeleton and liver) is an important aspect of radiation protection program. The measurement of 239Pu and 241Am long time post exposure can be carried out by measuring activity deposited in the skeleton and liver. The skeleton measurement is performed by placing detector above knee or skull(14). Total skeleton activity is estimated using the fraction of skeleton mass in knee or skull. In this work, we have calibrated an actinide lung monitor using Lawrence Livermore National Laboratory (LLNL) thorax phantom for 241Am deposited in the lungs and liver. The calibration factor for 241Am, deposited in bone is taken from our results on knee phantom measurement carried out under International Atomic Energy Agency (IAEA) inter-comparison exercise(15). The biokinetic model of 239Pu and 241Am has been solved to evaluate its retention in lungs, liver and skeleton at a different time post inhalation. For direct measurement, to identify which measurement geometry will give lower intake and committed effective dose (CED) estimate, internal dose is estimated at various days post inhalation using lung, liver and skeleton measurement data of 241Am at MDA level. Intake and CED values were calculated first using ICRP-66 HRTM, ICRP-30 GI tract model(16) and ICRP-67 biokinetic model(4), then intake values were calculated using revised ICRP-130 HRTM(6), ICRP-100 human alimentary tract model (HATM)(17) and new plutonium biokinetic model published by Leggett et al.(12). The results of this study will be useful to identify the organ whose in-vivomeasurement will give lowest intake and CED at various days post inhalation. MATERIALS AND METHODS Detection system An array of three 70 mm dia. and 25 mm thick n-type HPGe detectors (Make: Canberra Eurisys S.A.) installed inside totally shielded steel room is used for the measurement of gamma/X-rays of Pu/241Am and U(18, 19). The three detectors of the array are enclosed in a 20 cm diameter hollow copper cylinder, positioned at 120° apart. Their centers lie on the circumference of 10 cm dia. and each has 0.8 mm thick carbon window. The total area of all the three detectors is 115.4 cm2. The signals from each detector are acquired separately through three multi-channel analyzer cards, which can be summed into a single spectrum as per the requirement. Inter Winner gamma ray spectrometry software is used for analyzing the spectra. The full width at half maxima of each detector is ~0.6 keV at 59.5 keV photon energy. Figure 1 shows actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. Figure 1. View largeDownload slide Actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. Figure 1. View largeDownload slide Actinide monitoring system, consists of an array of three HPGe detectors placed above lungs of the LLNL phantom inside totally shielded steel room. The efficiency and MDA The in-vivo monitoring system used in this study is calibrated with realistic LLNL thorax phantom(20) for activity deposited in the lungs and liver. The LLNL phantom is a physical thorax phantom based on a Caucasian man with mass 76 kg and height 177 cm(21). This phantom has a simulated rib cage, removable lungs, heart, liver, major trachea and bronchial lymph nodes. Four numbers of 100% muscle equivalent chest overlay plates are available with the phantom. The overlay plates were used for placement over phantom for the representation of individuals with different tissue thicknesses above chest and liver. Thickness of the overlay plates above lungs varies from 1.77 to 6.18 cm and thickness above liver varies from 1.33 to 5.76 cm. For measurement of activity deposited in lungs, detectors are placed tangentially to suprasternal notch covering maximum lungs area and for liver measurement; detectors are placed near right sub-costal area covering liver. The counting efficiency, K (cps Bq−1) of the detection system at X cm of chest wall thickness (CWT) for photon energy, Ei is estimated using the following equation: KX,Ei=C−CbkgAT (1) where A is the amount of activity (Bq) present in the lungs or liver of LLNL phantom, C is the total counts in energy region. Cbkg is the background counts recorded with blank lung sets in respective energy region and T is the measurement time. Measurement geometry is kept same for the phantom as well as for the person. The minimum detectable activity (MDA) of the system at 95% confidence level is evaluated using the following equation(22): MDA=(4.65σb+2.7)KT (2) where σb is the standard deviation in the gross counts of reference energy band of an uncontaminated person measured in appropriate geometry, K is the counting efficiency (cps Bq−1); and T is the counting time.The efficiency and MDA of the detection system for 241Am in the skeleton is evaluated from our results of IAEA inter-comparison exercise. Under this exercise the leg phantom distributed with an unknown amount of 241Am was received by the laboratory. The measurement of activity was carried out with phoswich detector and results were reported to IAEA. Later on, the actual amount of 241Am distributed in the knee phantom was published(15). Using this value, efficiency and MDA of the phoswich detector is evaluated. To evaluate efficiency of HPGe detector, measurements were carried out for 241Am deposited in the knee of a worker with phoswich and HPGe array and counts obtained by both system were compared to derive efficiency of HPGe detector. The results were also verified with Monte Carlo simulation of knee voxel phantom(23). Method of in-vivo measurement of 239Pu and its intake estimation The in-vivo measurement of 239Pu can be carried out by detecting L X-rays of its daughter 235U which emits 13.5, 17.2 and 20.2 keV photons with a total yield of 4.6%. These U-L X-rays are not energetic enough to get transmitted through lungs and liver overlay tissues. Therefore, the detection limit of in-vivo monitoring system for the measurement of 239Pu using its X-ray energy is ~2000 Bq, which is quite high compared to relevant reference level. Therefore, direct measurement of Pu in various organs is carried out using 241Am as a tracer and by measuring its 59.5 keV gamma-rays having 36% yield. Then using following method amount of 239Pu present in the organ or its intake is estimated. In the case of inhalation of 239Pu, if 241Am is measured in the lungs then it is assumed that 241Am is embedded in plutonium matrix and follows biokinetics of plutonium in the lungs(5). Using 239Pu/241Am ratio obtained from radiochemical analysis of fecal/workplace sample, and measured activity of 241Am, total amount of 239Pu present in the lung is estimated. The 239Pu/241Am ratio depends on burn-up of the fuel and also the time elapsed after the purification of 239Pu. Typically the 239Pu/241Am ratio found for high burn-up fuel is ~3(24). Therefore, in this work for the evaluation of 239Pu, from MDA level of 241Am measured in the lungs of worker 239Pu/241Am ratio of three is used. Then using ICRP-78 methodology intake of plutonium is estimated. When 241Am is measured in liver or skeleton, the 239Pu/241Am ratio cannot be used directly for the estimation of 239Pu deposited in the measured organ. This is because, according to ICRP, plutonium and americium follow their own biokinetics and deposition in liver and skeleton will be different than actual radionuclide composition of this material at the time of intake. Therefore, from measured 241Am in liver and knee, first intake of 241Am is estimated, then this value is multiplied by the 239Pu/241Am ratio to evaluate 239Pu intake(25). The measured 241Am in lungs, liver and skeleton can be residual activity from intake of 241Am as well as due to in-growth from 241Pu (T1/2 = 14.35 y) decay. The 241Pu activity can vary from 84 to 97% of the total plutonium activity in irradiated nuclear fuel(26). In-growth of 241Am can take place in the organ where activity is deposited after intake as well as systemically. The ICRP publication 130 recommends that if 241Am is born systemically then americium biokinetics should be used in place of plutonium for dosimetric calculations. If measured 241Am without in-growth correction is used for plutonium dose estimation it will lead to overestimation of intake and CED values. Hence, first in-growth of 241Am from 241Pu should be evaluated using isotopic composition of inhaled material at the time of intake, then, after its correction, 241Am values should be used for intake and CED estimation(26). Computer software used for computations of organ contents of 239Pu and 241Am A computer program based on Birchall’s algorithm(27) for compartmental analysis with recycling was developed and standardized(28, 29). This program can be used for biokinetic studies of various radionuclides for any input parameters. The method incorporates the compartmentalized forms of biokinetic model of a selected radionuclide. It provides a solution for the complete compartmental model and can compute the daily urinary excretion and the amount of radioactivity retained in any organ at any time for both acute as well as for chronic intake by inhalation and ingestion. The transfer rate constants of plutonium and americium, d−1, (defined as the fractional flow per unit time between different compartments) for the HRTM, the GI tract and the biokinetic models were taken from ICRP Publication 66(3), 78(2) and 67(4), respectively. The above-mentioned methodology was applied to compute 239Pu and 241Am content in different organs for inhaled particle of 5 μm activity median aerodynamic diameter (AMAD) of absorption Type M and Type S for acute intake. For the purpose of the quality assurance of the software used, 239Pu and 241Am content in lungs and its daily urinary excretion were computed for inhaled activity of 5 μm AMAD particle size of absorption Types M and S and compared with the values given in the ICRP publication 78.(2) An excellent agreement was observed. Also, we have estimated retained fractions after inhalation of Type M and Type S plutonium compounds in lungs, liver and skeleton at different time by solving the improved plutonium biokinetic model developed by Leggett et al.(12) incorporated with ICRP-130 revised HRTM(6) and ICRP-100 HATM(17). RESULTS AND DISCUSSION Table 1 shows the efficiency and MDA of HPGe array based in-vivo monitoring system, obtained with 241Am distributed in the lungs and liver of LLNL phantom for various overlay thicknesses above these organs. The MDA of the system is calculated using average value of background counts obtained in energy region of the interest of 30 non-radiation workers monitored for 3000 s in the lungs, liver and knee measurement geometries. The mean value of muscle equivalent CWT (MEQ-CWT) for Indian worker is 1.77 ± 0.31 cm(30). The basic LLNL phantom is having MEQ-CWT of 1.77 cm (which is equivalent to mean MEQ-CWT for Indian worker) and liver overlay thickness of 1.33 cm. Therefore, efficiency and MDA obtained with the basic LLNL phantom was used for the interpretation of measurement results in terms of intake and CED. The efficiency and MDA of the system are 2.60E-03 cps Bq−1 and 6.0 Bq for 241Am in lungs and 5.55E-03 cps Bq−1 and 4.0 Bq for 241Am in liver with basic LLNL phantom. Table 1. The efficiency and MDA of HPGe array at 59.5 keV photon energy of 241Am distributed in the lungs and liver of LLNL phantom for the measurement time of 3000 s at various overlay thicknesses. Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Table 1. The efficiency and MDA of HPGe array at 59.5 keV photon energy of 241Am distributed in the lungs and liver of LLNL phantom for the measurement time of 3000 s at various overlay thicknesses. Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 Lungs Liver Chest wall thickness (cm) Efficiency (cps Bq−1) MDA (Bq) Liver overlay thickness (cm) Efficiency (cps Bq−1) MDA (Bq) 1.77 2.60E-03 ± 3.17E-05 6.0 1.33 5.55E-03 ± 5.90E-06 4.0 2.84 1.81E-03 ± 5.10E-05 9.1 2.31 3.96E-03 ± 1.03E-05 4.5 3.50 1.41E-03 ± 6.27E-05 11.7 3.04 3.12E-03 ± 1.35E-05 5.0 4.32 1.04E-03 ± 7.74E-05 15. 9 3.87 2.36E-03 ± 1.72E-05 7.0 6.18 6.31E-04 ± 7.92E-05 26.2 5.76 1.29E-03 ± 2.56E-05 12.8 The total surface area of lungs and liver of the LLNL phantom is ~2109 and 946 cm2, respectively(31). It is observed that liver geometry gives better efficiency and lower MDA compared to lungs geometry. This is because, detector covers larger fraction of liver area than lungs and lower overlying tissues thickness above liver (1.33 cm) as compared to lungs (1.77 cm). Table 1 shows that with increase in the thickness of overlay tissues above lungs and liver of the phantom, efficiency of the system decreases and MDA increases. Decrease in the efficiency is due to higher attenuation of photons with increase in the overlay thickness. Empirical equations have been derived to estimate efficiency at various overlay thicknesses for lungs and liver geometry. Efficiency (Y) of HPGe detector based system at 59.5 keV photon energy of 241Am in lungs and liver with x cm overlay thickness can be evaluated by the following equation: Y(HPGe,lung,59.5)(x)=0.00474e(−0.34x) (3) and equation: Y(HPGe,liver,59.5)(x)=0.00863e(−0.33x) (4) respectively. The efficiency and MDA of the HPGe system for 241Am in the knee were 4.5E-3 cps Bq−1 and ~3.0 Bq, respectively. Considering that knee contains 9.3% of the total bone mass(23), 30 Bq of the 241Am in skeleton can be measured using this system. The above results show that MDA of in-vivo monitoring system for 241Am deposited in lungs, liver and skeleton of worker having average physique are 6.0, 4.0 and 30.0 Bq, respectively, for measurement time of 3000 s. Using these values, intake and CED at various days post inhalation is evaluated to determine sensitivity of the techniques used for the measurement. Cross talk between 241Am in lungs, liver and skeleton It is known that 241Am gets transferred to liver and skeleton as time passes after inhalation, which interferes in estimating correct amount of activity deposited in lungs and liver. The cross talk between lungs, liver and skeleton (ribs) should be calculated before estimating amount of activity in any of these organs. The cross talk between liver and lungs for the system, used in this work, is estimated using LLNL phantom for 241Am. These values between lungs and liver is found to be <8% of the counting efficiency of that organ(32, 33). Also Lobaugh et al. have carried out extensive study for estimation of cross talk between lungs and other organs (ribs, lymph nodes and liver) in thorax region. Analysis of their results show that contribution to the measured organ due to activity in the source organ is <5% of the counting efficiency for the source organ(34). Therefore, if in-vivo measurement of 241Am is conducted long time after intake, cross talk from the activity deposited in other organs in the thorax region should be considered before estimating activity. Estimation of CED using ICRP-66 HRTM, ICRP-30 GI tract model and ICRP 67 biokinetic model of plutonium and americium at MDA level of 241Am measured in lungs, liver and skeleton Tables 2 and 3 give intake and CED calculated at MDA level of 241Am measured in the lungs, liver and skeleton at various days since inhalation for absorption Type M and Type S compounds respectively. The dose coefficients of these radionuclides have been taken from ICRP-68(35). If intake of Type M 241Am occurs one day prior to lung measurement, 2.8 mSv CED can be estimated. The CED estimated using MDA level of 241Am measured in liver and skeleton after one day of intake is ~8.6 and 107.0 mSv, respectively. This shows that lung measurement of 241Am is the most sensitive method for Type M compounds during initial days post inhalation. The estimated CED values at 100 d after inhalation for 241Am measured in lungs, liver and skeleton were 8.01, 4.93 and 53.2 mSv, respectively. Thus, measured 241Am deposited in the liver yields lower CED than lung measurement data at 100 d post inhalation intake. Table 2. The intake and CED from MDA equivalent Type M 241Am measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. Table 2. The intake and CED from MDA equivalent Type M 241Am measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 1.04E+02 2.81E+00 3.20E+02 8.64E+00 3.97E+03 1.07E+02 2 1.07E+02 2.90E+00 2.92E+02 7.88E+00 3.62E+03 9.77E+01 5 1.12E+02 3.04E+00 2.71E+02 7.33E+00 3.35E+03 9.04E+01 10 1.21E+02 3.26E+00 2.59E+02 7.00E+00 3.17E+03 8.56E+01 20 1.38E+02 3.73E+00 2.41E+02 6.52E+00 2.90E+03 7.84E+01 50 1.94E+02 5.24E+00 2.08E+02 5.63E+00 2.40E+03 6.48E+01 100 2.97E+02 8.01E+00 1.83E+02 4.93E+00 1.97E+03 5.32E+01 200 5.69E+02 1.54E+01 1.65E+02 4.47E+00 1.58E+03 4.27E+01 500 3.30E+03 8.92E+01 1.76E+02 4.74E+00 1.21E+03 3.26E+01 1000 5.93E+04 1.60E+03 2.40E+02 6.49E+00 1.03E+03 2.79E+01 2000 — — 4.24E+02 1.15E+01 9.49E+02 2.56E+01 5000 — — 1.03E+03 2.78E+01 1.02E+03 2.76E+01 10 000 — — 1.84E+03 4.97E+01 1.25E+03 3.38E+01 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. Table 3. The intake and CED from MDA equivalent 241Am embedded in Pu oxide (Type S) and measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Table 3. The intake and CED from MDA equivalent 241Am embedded in Pu oxide (Type S) and measured in lungs, liver and skeleton at various days post inhalation. Intake and CED are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of americium with default ICRP parameter for occupational workers. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED(mSv) 1 9.33E+01 7.75E−01 1.88E+04 1.56E+02 2.33E+05 1.94E+03 2 9.57E+01 7.94E−01 1.69E+04 1.40E+02 2.09E+05 1.74E+03 5 9.89E+01 8.20E−01 1.55E+04 1.28E+02 1.91E+05 1.58E+03 10 1.04E+02 8.60E−01 1.45E+04 1.21E+02 1.78E+05 1.48E+03 20 1.13E+02 9.37E−01 1.32E+04 1.09E+02 1.59E+05 1.32E+03 50 1.37E+02 1.14E+00 1.06E+04 8.83E+01 1.23E+05 1.02E+03 100 1.64E+02 1.36E+00 8.53E+03 7.08E+01 9.31E+04 7.73E+02 200 1.92E+02 1.60E+00 6.58E+03 5.46E+01 6.50E+04 5.39E+02 500 2.57E+02 2.13E+00 4.61E+03 3.83E+01 3.59E+04 2.98E+02 1000 3.98E+02 3.30E+00 3.93E+03 3.26E+01 2.23E+04 1.85E+02 2000 8.32E+02 6.90E+00 4.33E+03 3.59E+01 1.49E+04 1.24E+02 5000 2.71E+03 2.25E+01 7.60E+03 6.31E+01 1.15E+04 9.57E+01 10 000 7.04E+03 5.84E+01 1.26E+04 1.05E+02 1.18E+04 9.81E+01 Table 2, therefore, indicates that post 100–5000 d, liver measurement becomes sensitive, while post 5000 d, skeleton measurement becomes sensitive as it yields lowest CED among three geometries. From Table 3, it can be observed that for 241Am embedded in Type S plutonium matrix, lung geometry yields lowest CED even up to 10 000 d post inhalation compared to other two geometries. If measurements are conducted up to initial 200 d post inhalation, estimated CED will not be more than 1.6 mSv. Intake and CED of absorption Type M and S 239Pu calculated from MDA equivalent 241Am measured in lungs, liver and knee of a worker at various days post inhalation intake are given in Table 4 and Table 5 respectively. In the case of Type M 239Pu, lung monitoring of 241Am is the most sensitive technique during initial days after inhalation up to 100 d. About 9–10 mSv of CED from measured 239Pu can be estimated if measurements are conducted within a week after inhalation. Table 4. The intake and CED of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 4. The intake and CED of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 3.12E+02 9.99E+00 9.60E+02 3.07E+01 1.19E+04 3.82E+02 2 3.22E+02 1.03E+01 8.76E+02 2.80E+01 1.09E+04 3.47E+02 5 3.37E+02 1.08E+01 8.14E+02 2.61E+01 1.00E+04 3.21E+02 10 3.63E+02 1.16E+01 7.78E+02 2.49E+01 9.52E+03 3.05E+02 20 4.15E+02 1.33E+01 7.24E+02 2.32E+01 8.71E+03 2.79E+02 50 5.82E+02 1.86E+01 6.25E+02 2.00E+01 7.20E+03 2.30E+02 100 8.90E+02 2.85E+01 5.48E+02 1.75E+01 5.91E+03 1.89E+02 200 1.71E+03 5.46E+01 4.96E+02 1.59E+01 4.74E+03 1.52E+02 500 9.91E+03 3.17E+02 5.27E+02 1.69E+01 3.62E+03 1.16E+02 1000 1.78E+05 5.69E+03 7.21E+02 2.31E+01 3.10E+03 9.93E+01 2000 — — 1.27E+03 4.07E+01 2.85E+03 9.11E+01 5000 — — 3.09E+03 9.90E+01 3.06E+03 9.80E+01 10 000 — — 5.52E+03 1.77E+02 3.75E+03 1.20E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 5. The intake and CED of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 5. The intake and CED of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The 239Pu/241Am ratio of 3 was taken for the calculation. The values are calculated using ICRP-66 HRTM, ICRP 30 GIT and ICRP 67 biokinetic model of Pu with default ICRP parameter. Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Days (post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) Intake (Bq) CED (mSv) 1 2.80E+02 2.32E+00 5.64E+04 4.68E+02 — — 2 2.87E+02 2.38E+00 5.06E+04 4.20E+02 — — 5 2.97E+02 2.46E+00 4.64E+04 3.85E+02 — — 10 3.11E+02 2.58E+00 4.36E+04 3.62E+02 — — 20 3.39E+02 2.81E+00 3.95E+04 3.28E+02 — — 50 4.11E+02 3.41E+00 3.19E+04 2.65E+02 — — 100 4.91E+02 4.08E+00 2.56E+04 2.13E+02 — — 200 5.77E+02 4.79E+00 1.97E+04 1.64E+02 1.95E+05 1.62E+03 500 7.71E+02 6.40E+00 1.38E+04 1.15E+02 1.08E+05 8.94E+02 1000 1.19E+03 9.90E+00 1.18E+04 9.78E+01 6.68E+04 5.54E+02 2000 2.50E+03 2.07E+01 1.30E+04 1.08E+02 4.47E+04 3.71E+02 5000 8.13E+03 6.75E+01 2.28E+04 1.89E+02 3.46E+04 2.87E+02 10 000 2.11E+04 1.75E+02 3.79E+04 3.14E+02 3.55E+04 2.94E+02 Note: Intake and CED values are not given if CED exceeded 2.0 Sv. View Large Table 4, therefore, indicates that post 100 d, measurement of activity deposited in the liver becomes most sensitive method, while post 5000 d, skeleton becomes sensitive as it yields lowest CED out of the three geometries. From Table 5 it can be observed that for Type S 239Pu lung geometry yields lowest CED even up to 10 000 d post inhalation compared to other two geometries. If lung measurements are conducted for 241Am up to initial 200 d post inhalation, estimated 239Pu CED will not be more than 4.8 mSv. Effect of revised ICRP-130 HRTM, ICRP-100 HATM and Leggett’s systemic biokinetic model of Plutonium on intake estimation For inhalation of Type M and S 239Pu, the ICRP-130 revised HRTM, ICRP-100 HATM and revised ICRP-67 systemic biokinetic model of plutonium published by Leggett et al. is integrated together and solved for default parameters of reference radiation worker. These models were used to calculate retention fractions in lungs, liver and skeleton at various days after inhalation. ICRP has not published dose coefficient using revised biokinetic models, therefore, only intake values were estimated. CED can be calculated by multiplying these intake values with new dose coefficients whenever it will be available. The retained values in lungs, liver and skeleton is compared with those obtained with earlier models and are presented in Figures 2 and 3 for absorption Type M and S 239Pu, respectively. It is observed from Figure 2 that with previous models, initially lower amount of systemic activity is transferred to liver than skeleton. In revised model, larger fraction of plutonium is transferred to liver than skeleton in initial days. At 1 000 d post inhalation skeleton deposit exceeds liver deposit. For Type M 239Pu after 100 d since inhalation, liver deposit exceeds lung deposit. Therefore, measurements carried out after 100 d post inhalation of Type M 239Pu, the liver measurement gives lower intake. Figure 3 shows, for Type S 239Pu lung retention is similar with both models up to 600 d, afterwards lung retention is higher with the new model. The higher lung retention obtained with new model than previous model is likely to results into higher lung dose. The initial deposition in liver and skeleton are lower with revised model than earlier. In revised model for Type S 239Pu, liver content is higher than skeleton up to 4 000 d, after that skeleton content is higher. For Type S compounds of plutonium, lung retention is higher than liver and skeleton even up to 10 000 d. Figure 2. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type M 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 2. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type M 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 3. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type S 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Figure 3. View largeDownload slide Predicted values (Bq per Bq intake) in lungs, liver and skeleton following acute inhalation intake of Type S 239Pu using default ICRP metabolic parameters. The values marked with * denotes results obtained with revised HRTM, new HATM and Leggett’s Pu biokinetic model. Intake values at MDA level of activity measured in lungs, liver and skeleton based on revised ICRP models are estimated and these values are given in Tables 6 and 7 for absorption Type M and Type S 239Pu, respectively. It is observed from Table 6 that for Type M 239Pu, with revised model also, in-vivo measurement of lungs is most sensitive technique up to 200 d post inhalation, after that liver measurement is the most sensitive method. After 5 000 d, knee/skeleton measurement result yields lowest intake. In case of Type S 239Pu lungs measurement remains the most sensitive method even up to 10 000 d post inhalation compared to other two geometries. Table 6. Estimated intake of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Note: Intake values are not given if it exceeds MBq. View Large Table 6. Estimated intake of Type M 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Days (post exposure) Absorption Type M Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 3.10E+02 5.89E+03 — 2 3.36E+02 3.36E+03 4.18E+04 5 3.90E+02 1.97E+03 2.44E+04 10 4.34E+02 1.61E+03 1.98E+04 20 4.79E+02 1.40E+03 1.70E+04 50 5.92E+02 1.08E+03 1.26E+04 100 8.34E+02 8.52E+02 9.36E+03 200 1.63E+03 6.96E+02 6.85E+03 500 1.06E+04 6.89E+02 4.92E+03 1000 1.71E+05 9.25E+02 4.12E+03 2000 — 1.64E+03 3.66E+03 5000 — 4.67E+03 3.67E+03 10 000 — 1.11E+04 4.02E+03 Note: Intake values are not given if it exceeds MBq. View Large Table 7. Estimated intake of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake of 239Pu. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Note: Intake values are not given if it exceeds MBq. View Large Table 7. Estimated intake of Type S 239Pu from MDA equivalent 241Am measured in lungs, liver and skeleton at various days post inhalation. The Pu/241Am ratio of 3 was taken for the calculation of intake of 239Pu. Intake is calculated using ICRP-130 HRTM, ICRP-100 HATM and Legget’s biokinetic model of Pu with default parameters for occupational workers. Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Days(Post exposure) Absorption Type S Lungs Liver Skeleton Intake (Bq) Intake (Bq) Intake (Bq) 1 2.89E+02 9.98E+04 — 2 2.98E+02 6.02E+04 — 5 3.18E+02 3.76E+04 — 10 3.36E+02 3.21E+04 — 20 3.51E+02 2.95E+04 — 50 3.75E+02 2.50E+04 — 100 4.13E+02 2.05E+04 2.24E+05 200 4.94E+02 1.60E+04 1.58E+05 500 7.42E+02 1.17E+04 9.01E+04 1000 1.03E+03 1.02E+04 5.70E+04 2000 1.25E+03 9.74E+03 3.54E+04 5000 1.72E+03 1.02E+04 1.93E+04 10 000 2.90E+03 1.30E+04 1.35E+04 Note: Intake values are not given if it exceeds MBq. View Large Estimation of intake and CED from in-vivo measurement after acute inhalation intake of 241Am We have used a case study to show that follow-up measurement data of various geometries such as lungs, liver and skeleton should be used for intake and CED calculations. Kathren et al.(36) have described a case involving a person who was exposed while examining an old 370 MBq sealed 241Am source on 1 February 1996. Long-term follow-up measurement (up to 6 years) of 241Am deposited in lungs, liver and skeleton of this worker was carried out. The authors(36) have interpreted this material primarily being Type S perhaps mixed with Type M material. Based on this interpretation, they have estimated intake as 6.3 kBq. This case was also listed in IDEAS internal dosimetry database; Case Id 206(37). The intake and CED estimated by IDEAS are 7.2 kBq and 116.0 mSv, respectively. We have estimated retention factors for lungs and liver and calculated CED using ICRP 78 methodology (dose coefficient and biokinetic model) from lungs and liver measurement data, assuming material behaving as absorption Type M and S. The calculated CED assuming Type M material using lung and liver data are 1753.0 and 70.0 mSv, respectively. If inhaled material is assumed as Type S, estimated CED using lung and liver data are 54.9 and 705.6 mSv, respectively. Though the lung data support Type S behavior, liver measurement supports Type M behavior of inhaled compound which indicates it to be a mixture of Type S and Type M materials. Therefore while estimating CED, importance should be given not only to lungs measurement data but also to other organ measurement data. Using integrated modules for bioassay (IMBA)(38) software, best estimated intake and CED for this case are 7.1 kBq and 128.0 mSv, respectively. CONCLUSIONS The CEDs corresponding to MDA equivalent activity measured in lungs, liver and knee of worker for absorption Type M and Type S 239Pu and 241Am are estimated. The efficiency and MDA of HPGe array based in-vivo monitoring system for 241Am deposited in lungs, liver and skeleton were estimated using LLNL phantom and IAEA leg phantom. Retained fractions in lungs, liver and skeleton at different time post inhalation have been estimated using HRTM, GI tract model and ICRP-67 systemic model of 239Pu and 241Am. Retained values in these organs were compared with those obtained from the improved biokinetic model for plutonium developed by Leggett et al. incorporating ICRP-130 revised HRTM and HATM. 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