233U/236U signature allows to distinguish environmental emissions of civil nuclear industry from weapons fallout

K Hain; P Steier; M B Froehlich; R Golser; X Hou; J Lachner; T Nomura; J Qiao; F Quinto; A Sakaguchi

doi:10.1038/s41467-020-15008-2

²³³U/²³⁶U signature allows to distinguish environmental emissions of civil nuclear industry from weapons fallout

Nat Commun. 2020 Mar 9;11(1):1275. doi: 10.1038/s41467-020-15008-2.

Authors

K Hain¹, P Steier², M B Froehlich³, R Golser², X Hou⁴, J Lachner^{2

5}, T Nomura⁶, J Qiao⁴, F Quinto⁷, A Sakaguchi⁸

Affiliations

¹ Faculty of Physics, Isotope Physics, University of Vienna, Währinger Str. 17, 1090, Vienna, Austria. karin.hain@univie.ac.at.
² Faculty of Physics, Isotope Physics, University of Vienna, Währinger Str. 17, 1090, Vienna, Austria.
³ Department of Nuclear Physics, Australian National University, Canberra, ACT 2601, Australia.
⁴ Department of Environmental Engineering, Technical University of Denmark, DTU Risø Campus, 4000, Roskilde, Denmark.
⁵ Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Dresden, Germany.
⁶ Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
⁷ Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), Hermann-von-Helmholtz Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
⁸ Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.

Abstract

Isotopic ratios of radioactive releases into the environment are useful signatures for contamination source assessment. Uranium is known to behave conservatively in sea water so that a ratio of uranium trace isotopes may serve as a superior oceanographic tracer. Here we present data on the atomic [Formula: see text]U/[Formula: see text]U ratio analyzed in representative environmental samples finding ratios of (0.1-3.7)[Formula: see text]10[Formula: see text]. The ratios detected in compartments of the environment affected by releases of nuclear power production or by weapons fallout differ by one order of magnitude. Significant amounts of [Formula: see text]U were only released in nuclear weapons fallout, either produced by fast neutron reactions or directly by [Formula: see text]U-fueled devices. This makes the [Formula: see text]U/[Formula: see text]U ratio a promising new fingerprint for radioactive emissions. Our findings indicate a higher release of [Formula: see text]U by nuclear weapons tests before the maximum of global fallout in 1963, setting constraints on the design of the nuclear weapons employed.