PuMMA aims to define different options for Plutonium (Pu) management in Generation IV nuclear reactors. Find out more about Pu and why its management matters to enable fuel recycling and closing the fuel cycle, and to improve reactor safety and performance, paving the way for a more sustainable nuclear energy production.
What is plutonium?
Plutonium (Pu) is formed in nuclear power reactors from uranium-238 by neutron capture. Pu is recovered as a by-product of typical used fuel from a nuclear reactor, after the fuel has been irradiated (‘burned’) for about three years. Pu is a valuable energy source when integrated into the nuclear fuel cycle. In a conventional nuclear reactor, one kilogram of Pu-239 can produce sufficient heat to generate nearly 8 million kilowatt-hours of electricity. For several decades, the operation of nuclear reactors in Europe has led to the production of several hundred tons of plutonium, which is sometimes partly recycled as MOX fuels.
How are used fuels reprocessed into
MOX fuels?
A 1000 MWe light water reactor gives rise to about 25 tons of used fuel a year, containing up to 290 kilograms of plutonium. In order to extract it for recycle, the used fuel is reprocessed, and the recovered plutonium oxide is mixed with depleted uranium oxide to produce mixed-oxide fuels (MOX fuel), with about 8% Pu-239. Recycling Pu into MOX fuels is an opportunity to maximise its energetic potential, reducing the use of natural resources and the radiotoxicity of waste. Recycling as operated in France allows already saving of about 18% of the natural uranium resources that would be needed if there was no recycling.
Can Plutonium be
multi-recycled?
The recycling of Pu multiple times translates into an increase in Pu content in the fuel, limiting the Pu recycling ability of Generation II and III reactors whose fuel composition cannot exceed a relatively low Pu content limit. In the future context of sustainable nuclear energy, fast neutron reactors (FNR) are needed to efficiently multi-recycle plutonium and to reach a close and sustainable nuclear fuel cycle. The Generation IV reactors will be able to use and multi-recycle the accumulated Pu but also to overcome the use of fresh uranium coming from ores, thus reducing the use of natural fissile resources.
HOW does this contribute
to closing the
fuel cycle?
Generation IV reactors can support large quantities of Pu and recycle it many times, offering the ability to efficiently manage Pu, close the fuel cycle, and increase the sustainability of nuclear energy. The multiple recycling of plutonium and uranium in fast reactors will result in the following fuel cycle improvements:
- Only use of depleted uranium
- Use more than 80% of the uranium natural resource instead of 0.6 – 0.7% in current light water reactor systems,
- Providing additional burning of fissile plutonium and avoiding its accumulation in spent fuel stockpiles, decreasing the risk of diversion (resistance to proliferation).
- Once through recycling in pressurized water reactors already leads today to a reduction in High Level Waste by a factor of 3.6 compared to a light-water reactors fleet operating an open cycle. Used MOX multi recycling in fast neutron reactors will allow an additional reduction by a factor of 2.52.
The evolution of the fuel composition with the increase of Pu content compared to previous driver fuels justifies the need to launch new studies in all the fuel cycle step. The PUMMA project will define different options for Pu management in Generation IV systems and evaluate the impact on the whole fuel cycle in addition to safety and performance aspects.