Trace Fission Product Ratios for Nuclear Forensics Attribution of Weapons-Grade Plutonium from Fast and Thermal Reactors

The growing concern about nuclear terrorism threats has enhanced the need to develop fast and accurate nuclear forensics analysis techniques for nuclear material source attribution and to create a credible nuclear deterrence. Plutonium produced as a by-product in nuclear reactor fuel, especially in fuel discharged at low burn-up (1 to 2 MWd/kg), is potentially weapons usable material. In the event of plutonium interdiction from a smuggling act, its origin has to be established through nuclear forensics attribution methods before any response is initiated against this malicious act. The characteristics of separated plutonium from discharged reactor fuel and the associated fission product traces depend on factors such as the reactor type (thermal or fast reactor), fuel burn-up, irradiation history, and the chemical process used to separate plutonium. A new methodology of using trace fission product to plutonium ratios for nuclear forensics attribution of plutonium to the type of reactor used for its production is presented along with results obtained for case studies of a fast neutron spectrum breeder reactor and a thermal neutron spectrum reactor using open literature design information of these two types of nuclear reactors.