Abstract: Calculation of containment radionuclide concentration is an important part of estimating containment radiation dose rate, and the latter is a primary parameter for core damage assessment. This paperprovides the calculation of concentration of three typical nuclides within containment post-accident in both simplified analytical method and indirect methodwith ORIGEN2 code. The results show that the indirect method can simulate the release and decay of radionuclides and the transformation among them, and suggests it can be used in the early core damage assessment. But if the containment radionuclide concentration is evaluated after a long time since the accident, whenthe nuclides with short half-lives have little effects on the result, the simplified method is appropriate.

Key words: Core damage assessment, Containment radiation dose rate, Containment radionuclide concentration, ORIGEN2 model