Dragana Krstic

Input files with ORNL—mathematical phantoms of the human body for MCNP-4B

Abstract Protection against ionizing radiation requires information on the absorbed doses in organs of the human body. Implantation of many dosimeters in the human body is undesirable (or impossible), so the doses in organs are not measurable and some kind of dose calculation has to be applied. Calculation of doses in organs requests: (a) an exact description of the geometry of organs, (b) the chemical constitution of tissues, and (c) appropriate computer programs. The first two items, (a) and (b), make a so-called “phantom”. In another words, the “phantom of a human body” is a mathematical representation of the human body including all other relevant information. All organs are represented with geometrical bodies (like cylinders, ellipsoids, tori, cones etc.), which are described with suitable mathematical equations. A corresponding chemical constitution for various types of organ tissues is also defined. MCNP-4B ( M onte C arlo N - P article) is often used as transport code. Users of this software prepare an “input file” providing all necessary information for program execution. This information includes: (a) source definition—type of ionizing radiation, energy spectrum, and geometry of the source; (b) target definition—material constitution, geometry, location in respect to the source etc.; (c) characterization of absorbing media between the source and target; (d) output tally, etc. This paper presents input files with “human phantoms” for the MCNP-4B code. The input files with “phantoms” were prepared based on publications issued by the Oak Ridge National Laboratory (ORNL). Seven input files relating to different age groups (newborn, 1, 5, 10, 15 years, as well as, male and female adults) are presented here. A test example and comparison with other data found in literature are also given. Program summary Title of program: INPUT FILES, AMALE, AFEMALE, AGE15, AGE10, AGE5, AGE01, NEWB Catalogue identifier: ADYF_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADYF_v1_0 Program obtainable from: CPC Program Library, Queens University of Belfast, N. Ireland Computer: PC Pentium 3+ Operating systems: Windows 98 Programming language used: Fortran Memory required to execute with typical data: 128 MB No. of lines in distributed program, including test data, etc.: 2879 No. of bytes in distributed program, including test data, etc.: 23 151 Distribution format: tar.gz External subprograms used: The entire code must be linked with the MCNP-4B Nature of problem: The human body and all organs are represented with equations of 3D geometrical bodies. All equations and other relevant data (material composition, densities, etc.) were programmed as input files for MCNP-4B

Heavy metals, organics and radioactivity in soil of western Serbia

Western Serbia is a region well-known for potato production. Concentrations of selected metals, polycyclic aromatic hydrocarbons (PAHs) and radioactivity were measured in the soil in order to evaluate the quality and characteristics. The examined soils (Luvisol and Pseudogley) showed unsuitable agrochemical characteristics (acid reaction, low content of organic matter and potassium). Some samples contained Ni, Mn and Cr above the maximal permissible concentration (MPC). The average concentration of total PAHs was 1.92 mg/kg, which is larger than the maximal permissible concentration in Serbia but below the threshold values in the European Union for food production. The average radioactivity of (238)U, (226)Ra, (232)Th, (40)K and the fission product (137)Cs were 60.4+/-26.2, 33.2+/-13.4, 49.1+/-18.5, 379+/-108 and 36.4+/-23.3 Bq/kg. Enhanced radioactivity in the soils was found. The total absorbed dose rate in air above the soil at 1m height calculated for western Serbia was 73.4 nGy/h and the annual effective dose was 90 microSv, which are similar to earlier reports for the study region.

Gamma and beta doses in human organs due to radon progeny in human lung

A great deal of work has been devoted to determine the effect of tissue damage produced by alpha particles emitted from radon and its progeny. (214)Pb and (214)Bi deposited in the human lungs emit beta particles followed by the gamma quanta, which cause smaller damage of tissue in comparison with alpha particles. Because of that, this type of irradiation has not been studied in detail. In this paper, doses from beta and gamma rays emitted by radon progeny (214)Pb and (214)Bi in the lungs have been calculated in all main organs and the remainder tissues of the human body. Human Oak Ridge National Laboratory phantom of adult male and female was used, where simulation was performed using MCNP-4B simulation code. The sources of beta and gamma radiations, namely, the radon progeny were located in lungs. Furthermore, dose conversion coefficients have been calculated.

Determination of the soil-to-grass transfer of 137Cs and its relation to several soil properties at various locations in Serbia

Transfer coefficients of 137Cs from soil to grass were determined for the terrain around the city of Kragujevac in central Serbia. Mass activity concentrations of 137Cs in soil and grass samples were determined with a high-purity Ge-detector (HPGe). The activity concentration at the depth of 20 cm was found to be in the range of 14.92–124.05 Bq kg−1, whereas the activity in grass for the same location was in the range of 4.60–84.95 Bq kg−1. Transfer factors (TFs) were in the range of 0.07 up to 1.94. Dependences of TFs on different soil characteristics were presented graphically. Weak dependences were determined between them. Absaloms model was used to predict TFs based on soil characteristics: pH value, contents of clay, exchangeable potassium and humus. A comparison of measured and predicted values from Absaloms model is shown graphically. It has been found that Absaloms model might be carefully used for the prediction of 137Cs in grass for specific regions.

Sensitivity of radon measurements with CR-39 track etch detector : A Monte Carlo study

Abstract Sensitivity of radon measurements with solid state nuclear trak detector CR-39 was determined theoretically. Calculations were done for five types of different diffusion chambers. Calculational model is based on Betthe-Blochs expression for the stopping power oh the heavy charged particles in a medium, as well as, on the Monte Carlo Methods. Sensitivity dependence on the removed layer is studied in this work. The highest sensitivity in the studied diffusion chambers is approximately 0.15 (t/cm2)/(Bqd/m3).

Calculation of the effective dose from natural radioactivity in soil using MCNP code.

Effective dose delivered by photon emitted from natural radioactivity in soil was calculated in this work. Calculations have been done for the most common natural radionuclides in soil (238)U, (232)Th series and (40)K. A ORNL human phantoms and the Monte Carlo transport code MCNP-4B were employed to calculate the energy deposited in all organs. The effective dose was calculated according to ICRP 74 recommendations. Conversion factors of effective dose per air kerma were determined. Results obtained here were compared with other authors.

A calibration method for realistic neutron dosimetry in radiobiological experiments assisted by MCNP simulation.

Many studies on biological effects of neutrons involve dose responses of neutrons, which rely on accurately determined absorbed doses in the irradiated cells or living organisms. Absorbed doses are difficult to measure, and are commonly surrogated with doses measured using separate detectors. The present work describes the determination of doses absorbed in the cell layer underneath a medium column (DA) and the doses absorbed in an ionization chamber (DE) from neutrons through computer simulations using the MCNP-5 code, and the subsequent determination of the conversion coefficients R (= DA/DE). It was found that R in general decreased with increase in the medium thickness, which was due to elastic and inelastic scattering. For 2-MeV neutrons, conspicuous bulges in R values were observed at medium thicknesses of about 500, 1500, 2500 and 4000 μm, and these were attributed to carbon, oxygen and nitrogen nuclei, and were reflections of spikes in neutron interaction cross sections with these nuclei. For 0.1-MeV neutrons, no conspicuous bulges in R were observed (except one at ~2000 μm that was due to photon interactions), which was explained by the absence of prominent spikes in the interaction cross-sections with these nuclei for neutron energies <0.1 MeV. The ratio R could be increased by ~50% for small medium thickness if the incident neutron energy was reduced from 2 MeV to 0.1 MeV. As such, the absorbed doses in cells (DA) would vary with the incident neutron energies, even when the absorbed doses shown on the detector were the same.

Assessment of indoor absorbed gamma dose rate from natural radionuclides in concrete by the method of build-up factors

The specific absorbed gamma dose rates, originating from natural radionuclides in concrete, were calculated at different positions of a detection point inside the standard room, as well as inside an example room. The specific absorbed dose rates corresponding to a wall with arbitrary dimensions and thickness were also evaluated, and appropriate fitting functions were developed, enabling dose rate calculation for most realistic rooms. In order to make calculation simpler, the expressions fitting the exposure build-up factors for whole (238)U and (232)Th radionuclide series and (40)K were derived in this work, as well as the specific absorbed dose rates from a point source in concrete. Calculated values of the specific absorbed dose rates at the centre point of the standard room for (238)U, (232)Th and (40)K are in the ranges of previously obtained data.

Application of Mcnp5 Software for Efficiency Calculation of a Whole Body Counter

AbstractEfficiency of a whole body counter was calculated using MCNP5 code and measured experimentally. Measurements were performed using standard phantoms filled with water and a dissolved 137Cs isotope. The results obtained by calculation agree very well with the experimental ones for a set of different distances and axial shifts. The ORNL phantom of a human body was applied to investigate how representative the experimental calibration source is of the measured human subjects. Differences were found to be up to 20%, so corrections should be made if an accurate value of activity in the human body is desired. Experimental and theoretical work presented in this paper is related to a sodium iodide (NaI) detector, which has relatively low resolution. However, such systems are still in use in many laboratories. On the other hand, detection efficiency of a low-resolution system is larger than that for HpGe detectors, which might be important in an accidental situation when shorter measuring time is very important.

Doses in human organs due to alpha, beta and gamma radiations emitted by thoron progeny in the lung

This work consists of two parts. In the first part, the doses in the human lung per unit exposure to thoron progeny, the dose conversion factor (DCF), was calculated. Dependence of the DCF on various environmental and subject-related parameters was investigated. The model used in these calculations was based on ICRP 66 recommendations. In the second part, the human lungs were considered as the source of beta and gamma radiation which target the other organs of the human body. The DCF to other organs was obtained as 20 µSv WLM(-1), which is larger than the DCF for radon progeny, which was 13 µSv WLM(-1). This is a consequence of the longer half-life of the relevant thoron progeny than that of the radon progeny. It is interesting to note that after the lungs, where the radiation source is actually located, muscle tissue receives the largest dose.