1. 236 U Stephan Winkler (Univ. of Vienna)

2. Production of 236 U (n,3n) Main Production channel in thermonuclear devices is (n,3n) of 14MeV neutrons on 238 U. (Sakaguchi et al) Main Production in Reactors via (n,γ) of thermal neutrons on 235 U stephan.winkler@univie.ac.atAMS-12, Wellington, NZ, 2011

3. 236 U inventory Natural Uranium ore: 236 U/U typ. 4×10 -11. In U ore recoverable: 1.5 kg 236 U. Typical deep lithosphere: equilibrium 236 U/U = 2...5×10 -14 Inventory of the topmost 1000 m: ~22 kg 236 U Cosmic radiation: ~0.5 at 236 U cm -2 yr -1 (half of this in the upmost 1 m) Equilibrium inventory: 10 kg. Total transfer to rivers would rise the ratio in rivers by +5×10 -14 Signature of river water: 1...10×10 -14 also valid for the global oceans (U residence time: several 10 5 years, well mixed) Natural 236 U inventory in oceans: 0.2 kg (!) Anthropogenic 236 U produced by nuclear power reactors: ~10 6 kg (!) Global fall-out from nuclear weapons testing ~10 3 kg Leakage by reprocessing plants (e.g. Sellafield)

4. The HMF-1 236 U and 14 C record

5. Ocean Water Data So Far Depth profiles from Atlantic Northern Seas Sea of Japan