Nuclear, ENEA studies fuel recycling to reduce waste

Improving the sustainability and performance of Generation IV nuclear reactors by promoting the recycling of spent fuel to reduce long-lived waste. This is the aim of the Pumma (Plutonium Management for More Agility) project involving 20 partners from 12 European countries, including Enea for Italy. The project, co-funded by the Euratom programme, aims to assess the impact of the high plutonium content (around 40%) in the nuclear fuel of fast reactors and to examine the possible implications on safety and performance, as well as scenarios for integrating the technology with those currently in use, for an increasingly sustainable nuclear power.

'By using Mox, a fuel composed of a mixture of uranium oxide and plutonium, it is possible to obtain a more sustainable nuclear fuel that is available in large quantities,' explains Alessandro Del Nevo, head of ENEA's Experimental Engineering Division at the Nuclear Department and project leader. 'However, this is a fuel whose behaviour needs to be studied further in order to improve its performance and ensure adequate plant safety.

Project-related activities included both simulations through modelling and software and experimental analyses. For the tests, data already available on high plutonium MOX, irradiated and analysed by destructive and non-destructive examinations were used. 'The preliminary results are promising, but we need to improve our models based mainly on data from experiments on conventional water reactors,' Del Nevo clarifies. Specifically, Enea is contributing together with seven other partners to simulation and modelling activities to increase knowledge of the behaviour of the materials used during reactor operation.

Nuclear fuel 'pads', stacked inside cylindrical rods, represent, together with the outer sheath of the rod itself, the first barriers against the release of fission products. "Understanding how the materials of which the 'pads' are composed can be deformed or damaged by irradiation activity is essential to increase reliability and extend fuel life, without compromising safety margins," adds Del Nevo.

"During the course of the project, a significant milestone was achieved by replicating the behaviour of the nuclear fuel through FEM (Finite Element Method) analysis, the simulation technique that allows the structural behaviour of a complex system to be calculated by breaking it down into a large number of elements that can be solved in a simpler way," concludes Del Nevo.