Monte Carlo determination of dose coefficients at different developmental stages of zebrafish (Danio rerio) in experimental condition

The release of liquid effluent of nuclear power into aquatic system increases with the rapid development of nuclear facilities in coastal and inland regions. Aquatic model animals are very important for the study of the radiation hazards to non-human biota in water environment and its extrapolation of dose-effect relationship to human models. However, the study of the radiation dose rate calculation model of the aquatic animal zebrafish is still on the homogeneous isotropic model used for the protection of the environment. A series of zebrafish models (including adults, larvae and embryos, named zebrafish-family: ZF-family) with multiple internal organs are established in this study to investigate the mechanism of radiation damage effect in order to protect non-human species. The internal and external dose coefficients (DCs) of the whole body, heart and gonads of zebrafishes are calculated in water environment with the combination of the real experimental culture condition, using Monte Carlo application package GATE (Geant4 Application for Emission Tomography) and eight nuclides, i.e., ³H, ¹⁴C, ⁹⁰Sr, ⁶⁰Co, ^110mAg, ¹³⁴Cs, ¹³⁷Cs, ¹³¹I, which are commonly found in the liquid effluent of nuclear power plants, as the source items, The results show that the level of nuclide γ energy determines the external DCs (DC_ext), and ⁹⁰Sr plays the most important role in internal DCs (DC_int). The comparison between the external DCs of the heart and gonad and that of the whole body shows that DCs (DC_ext) of heart and gonad for females are 80% and 43% lower than that of whole body, respectively, while for males, the DCs (DC_ext) of heart is 44% lower than that of the whole body, and DCs (DC_ext) of gonad is slightly higher than that of the whole body for most nuclides (up to 25%).The dose of internal radiation makes greater contribution than that of external radiation to pure beta emitter (³H, ¹⁴C, ⁹⁰Sr). This internal DCs of ZF-family model with complex internal structure turns out to demonstrate more sensitive DCs change trend and higher calculation values compared with the internal DCs of the simple ellipsoid model. In this model, the photon emitter with strong penetrating power has higher internal DCs, while the low-energy pure beta nuclide does not alter much. In conclusion, it is vital to carry out refined systematic modeling for model organisms, and the determination of DCs of model organs can promote the evaluation of the radiation effects on non-human species.