Beyond one million years: The intrinsic radiation hazard of high-level nuclear wastes

Abstract This paper highlights the absence of quantitative estimates regarding the intrinsic radiation hazard of high-level nuclear wastes, namely, spent fuel (SF) and vitrified high-level wastes (VHLW), for periods exceeding one million years. Using available data, conducting scoping calculations of radiation doses, and comparing the results to radiation protection guidelines and natural background radiation, this paper shows that high-level wastes cannot be safely handled or left unprotected essentially indefinitely. By quantitatively evaluating the dose rates of unshielded SF and VHLW, this study identifies critical new insights, such as the roles of the Np-237 decay chain; the eventual, long-term dominance of the U-238 decay chain; and the interplay of three actinide decay chains, including the significant role of Bi-214. These findings fill a gap in the literature and emphasize the need for more detailed investigations in this as-yet-unexplored research area, which has a direct bearing on technical and societal decision-making for both waste disposal safety and the choice of the back end of the nuclear fuel cycle.