This report is a compilation of dose coefficients for intakes of radionuclides by workers and members of the public, and conversion coefficients for use in occupational radiological protection against external radiation from Publications 68, 72, and 74 (ICRP, 1994b, 1996a,b). It serves as a comprehensive reference for dose coefficients based on the primary radiation protection guidance given in the Publication 60 recommendations (ICRP, 1991). The coefficients tabulated in this publication will be superseded in due course by values based on the Publication 103 recommendations (ICRP, 2007).

A computational phantom with moving arms and legs and an accompanying graphical user interface, PIMAL, was previously developed to enable radiation dose estimation for different postures in a user-friendly manner. This initial version of the software was useful in adjusting the posture, generating the corresponding MCNP input file, and performing the radiation transport simulations for dose calculations using MCNP5 or MCNPX. However, it only included one mathematical phantom model (hermaphrodite) and allowed only isotropic point sources. Recently, the software was enhanced by adding two more mathematical phantom models, a male and female, and the source features were enhanced significantly by adding internal and external source options in a pull-down menu. Although the initial version of the software included only a mathematical hermaphrodite phantom, the features and models in the software are constantly being enhanced by adding more phantoms as well as other options to enable dose assessment for different configurations/cases in a user-friendly manner. In this latest version of the software, ICRP's recently released reference male and female voxel phantoms are included in a pull-down menu. The male and female models are described using 7 and 14 million voxels, respectively. Currently, the software is being modified further to include themore » International Commission on Radiation Protection's (ICRP) reference male and female voxel phantoms. Additionally, some case studies are being implemented and included in a library of input files. This paper describes recent updates to the software.« less

For correct radiation dose assessment, it is important to take the posture into account. A computational phantom with moving arms and legs was previously developed to address this need. Further, an accompanying graphical user interface (GUI), called PIMAL, was developed to enable dose estimation using realistic postures in a user-friendly manner such that the analyst's time could be substantially reduced. The importance of the posture for correct dose estimation has been demonstrated with a few case studies in earlier analyses. The previous version of PIMAL was somewhat limited in its features (i.e., it contained only a hermaphrodite phantom model and allowed only isotropic source definition). Currently GUI is being further enhanced by incorporating additional phantom models, improving the features, and increasing the user friendliness in general. This paper describes recent updates to the PIMAL software. In this summary recent updates to the PIMAL software, which aims to perform radiation transport simulations for phantom models in realistic postures in a user-friendly manner, are described. In future work additional phantom models, including hybrid phantom models, will be incorporated. In addition to further enhancements, a library of input files for the case studies that have been analyzed to date will be included inmore » the PIMAL.« less

In an earlier effort, the Oak Ridge National Laboratory (ORNL) mathematical phantom has been revised to enable assessment of radiation dose for different postures in occupational exposures by enabling freely positioning arms and legs. The revised phantom is called PIMAL: Phantom wIth Moving Arms and Legs. Further, to assist the analyst with input preparation and output manipulation for different postures, a graphical user interface has been developed. Also, at ORNL a hybrid computational phantom, which uses a combination of voxelized and stylized geometry, for radiation dose assessment was recently developed. This phantom is based on the International Commission on Radiological Protection's (ICRP's) male phantom model and is called VOXMAT. For VOXMAT, the head and torso, which contain significant anatomical details, were described using voxel geometry. The arms and legs, which contain less-detailed anatomical structures, were modeled using the mathematical equations (stylized approach). With this approach the number of voxels was reduced from 7 million to 2.3 million, which translated into a proportional reduction in computational time and memory requirements. More importantly, VOXMAT allows easy the movement of arms and legs for radiation dose assessment for realistic postures. To determine/demonstrate the importance of the realistic posture for a case study, PIMALmore » and VOXMAT are applied to assess the dose to a glovebox worker. In this paper, the comparative computational results for the estimated dose are presented.« less

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Estimates of the dose to the extrathoracic airway (nasal vestibule) from inhaled beta-emitting radionuclides, obtained using the respiratory tract model presented in Publication 66 of the International Commission on Radiological Protection, frequently predict that the basal cells in this region are the most highly irradiated tissues of the body. The dose to the basal cells is averaged over a layer of tissue 10 microm thick located at a depth of 40 microm into the airway assuming that charged particle equilibrium exists. Since the target (basal cell layer) is very small and thin (10 cm(2) area and 10 microm thickness), charged particle equilibrium does not exist. In this work the effect on the absorbed fraction of the lack of charged particle equilibrium is investigated.

In a previous work we reported that the fraction of the electron energy absorbed in the basal cell layer of the anterior nasal passages was not very sensitive to changes in the surface area or radius of the cylindrical model adopted in Publication 66 of the International Commission on Radiological Protection. These absorbed fraction data are used in calculation of the dose to a 10-mum-thick basal cell layer located at a depth of 40 mum in the epithelial cell layer of the extrathoracic (ET1) region. However, these data may only be applicable to the assumed cylindrical geometry and may not be valid for more realistic ET1 geometries. The nose differs in size and shape from one person to another, its shape is not cylindrical but closer to a truncated elliptical cone, and in most humans the nostrils are elliptical in shape. We propose herein a more realistic geometry model, the frustum of a cone, for the anterior nose region (ET1) as an alternative to the cylinder model provided in ICRP 66. The results of absorbed fraction calculations using MCNP4B with the new model are reported. These absorbed fractions are compared to the values previously obtained using the MCNP4B code and a cylindrical model (10 cm(2) surface area). We also investigate the effects of changing the size of the truncated cone to represent variations due to sex and age.

The Human Respiratory Tract Model of ICRP Publication 66 is used for calculations of dose in the extrathorathic (ET1) airways. Scaling for age and body size is included in determining the mass of the target tissue (basal cells) in ET1 but is not included in deriving the absorbed fraction for particulate radiation. For dose calculations, it has been assumed that all absorbed fractions for particulate radiation published in ICRP Publication 66 are independent of age and body size. Therefore, these absorbed fractions are applied to calculate specific effective energy values not only for the Reference Worker but also for non-adults with noses of different sizes. In this note changes to the size of the cylinder model of the anterior nose in ICRP 66 are made by varying the surface area, the cylinder radius, and the thickness of tissue beyond the target region (basal cell). The energy deposition (absorbed fractions) in the target region (basal cells) is calculated using the MCNP4B (Monte Carlo) code to study the effects of these changes on the predicted absorbed fractions within the cylinder model.

The electron absorbed fraction in the anterior nose is estimated in the International Commission on Radiological Protection Publication 66 using the ECS4 Code anti it cylinder model. The electrons are assumed to come from point sources lining the inner surface of the nose. Although the radioactive source particles are carried in dust, self-absorption in the dust is ignored. Consequently, the absorbed fractions Published in ICRP 66 cannot represent the correct energy deposition in the basal cell region. In this work we estimate the energy lost by the emitted electrons inside spherical dust particles. which vary in diameter front 1 mum to 100 mum. The absorbed fractions in the basal cell layer are then estimated using the modified electron energy spectrum. To illustrate these effects, modified absorbed fractions for a dust particle radius of 20 mum are compared to the absorbed fractions presented in ICRP 66. Significant differences are noted.

Dose calculations using the respiratory tract model presented in Publication 66 of the International Commission on Radiological Protection (ICRP) frequently predict that the basal cells of the anterior portion of the nose, the extrathoracic region ET1 of the model, are the most highly irradiated tissue of the body. The dose to the basal cells is averaged over a layer of tissue 10 microm thick located at a depth of 40 microm into the airway. Reported here are the results of a series of absorbed fraction calculations undertaken to compare with values tabulated in ICRP Publication 66. The Monte Carlo code MCNP4B and the geometric model of the ET1 region specified in Publication 66 were used in the calculations. Although some calculated differences are evident between the two sets of absorbed fractions, typically less than 20%, the calculations confirm that the electron absorbed fractions tabulated in Publication 66 are not responsible for the high estimates of the ET1 dose.

Following more than a decade of scientific debate about the setting of a standard for 222Rn in drinking water, Congress established a timetable for the promulgation of a standard in the 1996 Amendments to the Safe Drinking Water Act. As a result of those Amendments, the EPA contracted with the National Academy of Sciences to undertake a risk assessment for exposure to radon in drinking water. In addition, the resulting committee was asked to address several other scientific issues including the national average ambient 222Rn concentration and the increment of 222Rn to the indoor-air concentration arising from the use of drinking water in a home. A new dosimetric analysis of the cancer risk to the stomach from ingestion was performed. The recently reported risk estimates developed by the BEIR VI Committee for inhalation of radon decay products were adopted. Because the 1996 Amendments permit states to develop programs in which mitigation of air-producing health-rsik reductions equivalent to that which woul...