Abstract: The transfer factor of radionuclides from soil to plants is one of the most important parameters in the biosphere assessment model of high-level radioactive waste disposal. The value and uncertainty of the transfer factors have significant impact on the assessment results. In order to obtain the transfer parameters and uncertainty level for the site of Beishan underground research laboratory, the dominant plant type plant Sympegma regelii Bunge was selected to carry out a preliminary study on the radionuclides transfer factor of soil to plant. In this paper, the natural radionuclides ²³⁸U, ²³²Th, ²²⁶Ra and artificial radionuclides ¹³⁷Cs in representative soil samples and Sympegma regelii Bunge were measured and analyzed; the transfer factor and uncertainty level of nuclides from soil to roots, stems and leaves of Sympegma regelii Bunge were obtained. The results showed that the transfer factor of natural radionuclides ²³⁸U, ²³²Th and ²²⁶Ra in stems were generally higher than those in roots and leaves, while the transfer factor of artificial radionuclides ¹³⁷Cs in roots were significantly higher than those in stems and leaves. The fluctuation range of transfer factor of natural radionuclides ²³⁸U, ²³²Th and ²²⁶Ra was within 1 order of magnitude, while the fluctuation range of artificial radionuclide ¹³⁷Cs was up to 2 orders of magnitude. The fluctuation range of radionuclide transfer factor showed that the leaves were significantly higher than that in the stems and roots.

Key words: high-level radioactive waste, Beishan, safety assessment, biosphere assessment, transfer factor