External exposure to environmental sources is an important pathway of exposure of the public after major releases of radionuclides to the environment. In the early stage after a nuclear accident, internal exposures due to inhalation and ingestion of radionuclides are likely to significantly contribute to organ doses and effective dose. However, some time after an accidental release external exposure is a major contributor to the doses of members of the public. This is also the case after the accident at the nuclear power plant (NPP) in Fukushima Prefecture, Japan in March 2011. Age-dependent dose coefficients for the internal exposures have been evaluated comprehensively by ICRP (Publications 56, 67, 69, 71, 72 currently under revision), while age-dependent dose conversion coefficients for external exposures have not been evaluated by ICRP. The purpose of the proposed report is, therefore, to provide age-dependent dose conversion coefficients for external environmental exposures.
Conversion coefficients are needed to evaluate effective dose from measurements of air kerma, the absorbed dose in air, or the ambient dose equivalent. Calculation of the conversion coefficients requires the evaluation of the environmental field (i.e. density and composition of soil, radionuclide distribution), the model of the human body, i.e. the phantoms that represent the members of the public, and the simulation of the radiation transport. Organ doses depend on body mass since, in external photon exposure, increasing amounts of overlying tissue enhances the shielding of the organs located beneath the subcutaneous adipose mass. Therefore, reference models of adults as well as of children of different ages will be used in the calculations.
Conversion coefficients for environmental exposures will be computed for the ICRP voxel-based adult male and female reference computational phantoms (ICRP Publication 110) as well as for the 10 pediatric NURB-based phantoms of the University of Florida. The latter have been selected to become the reference ICRP pediatric phantoms. The Task Group (TG) will identify the most probable exposure scenarios for the simulation (see outline of the task). The TG will have close collaboration with DOCAL.
|Nina Petoussi-Henss (Chair), Helmholtz Zentrum München, Germany|
|Michael Bellamy (Corresponding Member), Oak Ridge National Laboratory, USA|
|Wesley E. Bolch (Member), University of Florida, USA|
|Keith Eckerman (Member), Oak Ridge National Laboratory (ORNL), USA|
|Akira Endo (Member), Japan Atomic Energy Agency (JAEA), Japan|
|Nolan E. Hertel (Corresponding Member), Georgia Institute of Technology, USA|
|John G.S. Hunt (Corresponding Member), The Instituto de Radioproteção e Dosimetria, Brazil|
|Jan T.M. Jansen (Corresponding Member), Public Health England, UK|
|Choonsik Lee (Corresponding Member), National Cancer Institute, USA|
|Kimiaki Saito (Corresponding Member), Japan Atomic Engergy Agency, Japan|
|Daiki Satoh (Corresponding Member), Japan Atomic Engergy Agency, Japan|
|Helmut Schlattl (Member), Helmholtz Zentrum München , Germany|
|Yeon Soo Yeom (Corresponding Member), National Cancer Institute, USA|
|Song Jae Yoo (Corresponding Member), Korea Institute of Nuclear Safety(KINS), Korea|