Ultra-Low-Level Measurements of Argon, Krypton and Radio xenon for Treaty Verification Purposes

Various noble gases are created in nuclear processes like burn-up of nuclear fuel, target irradiation and nuclear explosion. Being chemically inert, they won't react with the ambient environment or deposit on the ground once entered into the atmosphere but keep on travelling and only disappear due to radioactive decay. They are, therefore, very good tracers for revealing specific nuclear activities and can help in verifying non-proliferation treaties. Krypton-85 and radio xenon isotopes are anthropogenic isotopes produced through fission of uranium or plutonium. The analysis of krypton in the atmosphere could help, e.g. in verifying compliance with the Nuclear Non-Proliferation Treaty by monitoring nuclear fuel re-processing activities. The detection of the radio xenon isotopes could give indications e.g. on a nuclear explosion, clandestine nuclear reactors or other violations of nonproliferation treaties. Argon-37 is an anthropogenic isotope produced when e.g. fission neutrons react with calcium in rock. Its identification in the lower troposphere or in soil gas can be an indication for the detonation of a nuclear device and can be used to verify the Comprehensive Nuclear Test-Ban-Treaty e.g. during an on-site inspection. Other noble gases like argon-41 and various short lived krypton isotopes may be used for nuclear safety monitoring or reactor operation surveillance. This paper will describe how these noble gases are created, measured at ultra-low sensitivity level and used to trace back a violence of treaties dealing with nuclear arms control and non-proliferation and propose additional applications of these new ultralow environmental measurement techniques