F. Parozzi, F. Polidoro: FEASIBILITY OF FUEL CYCLE BASED ON Th-MOX IN SMALL MODULAR REACTORS
Abstract. Uranium resources are secure for a long time, but prices are likely to be substantially higher after 2020. Nowadays, conventional industry, built on uranium, is watching with interest to thorium that could represent an alternative to uranium as fuel. Moreover, Thorium-MOX fuels, designed to be used in conventional LWRs, can utilize plutonium from spent fuel and weapons dismantling in order to provide a new option for reducing civil and military plutonium stocks. In this context, the sustainability of a fuel cycle based on thorium-plutonium mixed oxides in a Small Modular Reactor, is analyzed by using state-of-art neutronic numerical models. The work, in particular, analyzes the behavior of a SMR core fueled with Th-MOX fuel assemblies, and compares it with the analogous behavior of a SMR core fueled with conventional MOX. Main advantages and drawbacks of this option are also highlighted.
F. Polidoro: PROLIFERATION RESISTANCE OF NUCLEAR FUELS FOR SMALL MODULAR REACTORS
Abstract. Proliferation resistance has become one of the primary topics to be addressed if new nuclear energy systems are being developed as any nuclear system presents potential proliferation risks. In a near future, the diffusion of a nuclear fleet of Small Modular Reactors (SMRs), with inherent safety characteristics and with low level of attractiveness to the proliferation, could further enhance the capability to utilize plutonium from spent fuel and weapons dismantling, so providing a new option for reducing civil and military plutonium stocks. In this context, the objective of the present study is to identify the level of proliferation attractiveness of fuel loaded in SMR cores based on pressurized light water technology (PWR). In order to face the proliferation risk, a core designed to use MOX (Mixed Oxide) fuel is proposed, its performance investigated and the level of usability of the plutonium for non-peaceful applications assessed.
F. Polidoro: PROLIFERATION RISK RELATED TO THE DIVERSION OF REACTOR-GRADE PLUTONIUM
Abstract. The reactor-grade plutonium produced in the fuel of a typical LWR, at the time of discharge, is generally considered no-attractive for the realization of nuclear weapons, due to the presence of 240Pu in high concentration (a strong neutron emitter due to its spontaneous fission) and 238Pu (a strong α-emitter). However, in the last decades, doubts on the possible use of reactor-grade plutonium for nuclear weapons have arisen. It is, therefore, important to understand how reactor-grade plutonium, from nuclear fuel cycle, can be potentially used to produce nuclear explosives. Aim of this work is to evaluate, making use of available literature data and physical models, what is the potential nuclear explosive yield of an Hypothetical Nuclear Explosive Device (HNED) of the implosion type, based on the reactor-grade plutonium and low technology, i.e. a technology comparable to that of the first plutonium weapons. The results of the numerical analysis shows that the high inherent spontaneous fission neutron source of 240Pu, strongly affects the explosion yield, so limiting the energy released to the range of fraction of kilotons (TNT equivalent).