236U

Stephan Winkler(Univ. of Vienna)

Production of 236U

(n,3n)

Main Production channel in thermonuclear devices is (n,3n) of 14MeV neutrons on 238U.(Sakaguchi et al)

Main Production in Reactors via (n,γ) of thermal neutrons on 235U

stephan.winkler@univie.ac.at AMS-12, Wellington, NZ, 2011

236U inventoryNatural

• Uranium ore: 236U/U typ. 4×10-11. In U ore recoverable: 1.5 kg 236U.

• Typical deep lithosphere: equilibrium 236U/U = 2...5×10-14 Inventory of the topmost 1000 m: ~22 kg 236U

• Cosmic radiation: ~0.5 at 236U 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 105 years, well mixed)

• Natural 236U inventory in oceans: 0.2 kg (!)

Anthropogenic

• 236U produced by nuclear power reactors: ~106 kg (!)

• Global fall-out from nuclear weapons testing ~103 kg

• Leakage by reprocessing plants (e.g. Sellafield)

The HMF-1 236U and 14C record

Ocean Water Data So Far

Depth profiles from • Atlantic • Northern Seas• Sea of Japan