ICRP Publication 144: Dose Coefficients for External Exposures to Environmental Sources

This publication presents radionuclide-specific organ and effective dose rate for members of the public resulting from environmental external exposures to emissions of both photons and electrons, calculated using computational representing the ICRP reference newborn, 1-year-old, 5-year-old, 10-year-old, 15--old, and adult males and females. Environmental radiation fields of monoenergetic and electron sources were firstly computed using the Monte Carlo radiation transport PHITS (Particle and Heavy Ion Transport code System) for source geometries environmental radionuclide exposures including planar sources on and within ground at different depths (representing radionuclide ground contamination from fall-out naturally occurring terrestrial sources), volumetric sources in air (representing a cloud), and uniformly distributed sources in simulated contaminated water. For above geometries, the exposed reference individual is considered to be completely within radiation field. Organ equivalent dose rate coefficients for monoenergetic photons and were next computed employing the PHITS code thus simulating photon and interactions within the tissues and organs of the exposed reference individual. For assurance purposes, further cross-check calculations were performed using GEANT4,, MCNPX, MCNP6, and the Visible Monte Carlo radiation transport codes. From the values, nuclide-specific effective and organ equivalent dose rate coefficients several radionuclides for the above environmental exposures were computed using the decay data from Publication 107. The coefficients are given as dose rates normalised radionuclide concentrations in environmental media, such as radioactivity concentration, in of nSv h-1 Bq-1 m-2 or nSv h-1 Bq-1 m-3 and can be re-normalised to ambient dose (Sv Sv-1) or air kerma (Sv Gy-1). The findings showed that, in general, the smaller body mass of the phantom, the higher the organ and effective dose due to (1) closer to the source (in the case of ground contamination) and (2) the smaller amount of shielding of internal organs in the younger and smaller reference phantoms. The in effective dose between an adult and an infant is 60-140% at a photon energy of50 keV, while it is less than 70% above a photon energy of 100 keV, where the smaller are observed for air submersion and the largest differences are observed for soil on the surface of the ground. For realistic exposure situations of radionuclide contamination, the difference was found to be more moderate. For example, radioactive caesium (134Cs, 136Cs, 137Cs/137mBa) deposited on and in the ground, the in effective dose between an adult and an infant was in the range of 20-60%, on the radioactivity deposition depth within the soil. ICRP solicits comments on most draft documents prior to , with the exception of those that are basically compilations of computed values such as specific absorbed fraction values or dose factors.View comments Draft Document