Absorbed Internal Dose Conversion Coefficients for Domestic Reference Animals and Plant

Traditionally, radiation protection has focused on the radiation exposure of human beings. Recently, since the Rio Declaration emphasized the issue of sustainable development [1], the protection of the environment from the effects of ionizing radiations has become a key subject for all relevant international organizations in the field of radiation protection. There have been a number of international meetings that have tried to exchange information on the subject [2-4]. Based on all these international activities, the International Commission on Radiological Protection (ICRP) stressed the importance of environmental protection from ionizing radiations in the new recommendation issued in 2007 [5], and subsequently has made efforts in setting up a methodology that can assess the radiological impact of ionizing radiations on non human species. Animals and plants in the ecosystem are exposed to environmental radioactivity both externally and internally. Internal exposure arises from the bioaccumulation of radionuclides in organisms throughout the food chain network. The extent of the internal exposure is influenced by several factors, such as the concentration of radioactivity in an organism, the size of the organism, and the type of radionuclides. Internal dose conversion coefficients have been derived by a number of approaches for the purpose of assessing radiological impact on non-human species. Amiro [6] calculated the radiological dose conversion factors for generic non-human biota with a conservative assumption that all energies emitted by radionuclide from within the organism are fully absorbed by the organism. Higley et al. [7] also calculated the internal dose conversion coefficient for a biota by using a similar assumption (the organism is extremely large) for a general screening purpose. However, these assumptions are reasonable for a certain type of low-energy radiation that has a short transport distance in the material, such as alpha particles and low-energy electrons. In recent years, more realistic approaches that considered the finite organism size and the intensity of the emitted energy have been attempted by several researchers [8-10]. Ulanovsky and Pröhl [9] proposed a practical method for assessing the dose conversion coefficients for aquatic biota. They applied the Monte Carlo simulation in order to account for the effect of the sizes of the organism and energy intensity. Taranenko et al. [10] presented a dosimetric model by using Monte Carlo simulation in order to calculate the absorbed dose rate conversion coefficients for some terrestrial biota. These two studies have been adopted in This paper describes the methodology of calculating the internal dose conversion coefficient in order to assess the radiological impact on non-human species. This paper also presents the internal dose conversion coefficients of 25 radionuclides (H, Be, C, K, Cr, Mn, Fe, Co, Co, Zn, Sr, Zr, Nb, Tc, Ru, I, I, Cs, Cs, Ba, La, Ce, U, Pu, Pu) for domestic seven reference animals (roe deer, rat, frog, snake, Chinese minnow, bee, and earthworm) and one reference plant (pine tree). The uniform isotropic model was applied in order to calculate the internal dose conversion coefficients. The calculated internal dose conversion coefficient (μGyd per Bqkg) ranged from 10 to 10 according to the type of radionuclides and organisms studied. It turns out that the internal does conversion coefficient was higher for alpha radionuclides, such as U, Pu, and Pu, and for large organisms, such as roe deer and pine tree. The internal dose conversion coefficients of Pu, Pu, U, C, H and Tc were independent of the organism.