Recycling uranium and plutonium: where’s it heading?

Currently 12 of the countries with nuclear energy programmes are committed to a closed nuclear fuel cycle but there are signs that the number will soon increase. In particular, the USA is reassessing its previous policy, set strongly against reprocessing with subsequent recycling of recovered materials. The decision to introduce MOX fuel from ex-weapons plutonium in civil reactors was an important factor in that country’s change of policy and the first assemblies are now in use in reactors operated by Duke Power. In November 2005 the American Nuclear Society released a position statement saying that it “believes that the development and deployment of advanced nuclear reactors based on fast neutron fission technology is important to the sustainability, reliability and security of the world’s long-term energy supply.”
This will enable “extending by a hundred-fold the amount of energy extracted from the same amount of mined uranium.” The statement envisages onsite reprocessing of used fuel from fast reactors and says that “virtually all long-lived heavy elements are eliminated during fast reactor operation, leaving a small amount of fission product waste which requires assured isolation from the environment for less than 500 years.”

The Global Nuclear Energy Partnership (GNEP) programme, announced by the US Department of Energy in early 2006, fits in closely with this. A major issue addressed is the efficiency of the current nuclear fuel cycle. The ‘once through’ cycle only uses part of the potential energy in the fuel, while effectively wasting substantial amounts of useable energy that could be tapped through recycling. While European countries and Japan have recycled some of the residual uranium and plutonium recovered from the spent fuel in light water reactors through MOX utilisation, no one has yet employed a comprehensive technology that includes full actinide recycle. In the USA this question is pressing since significant amounts of used nuclear fuel are stored in different locations around the country awaiting shipment to the planned geological repository at Yucca Mountain in Nevada. This project is much-delayed, and in any case will fill very rapidly if it is used simply for used fuel rather than the separated wastes after reprocessing.

An early priority in GNEP is therefore the development of new reprocessing technologies to enable recycling of most of the used fuel. One of the concerns when reprocessing used nuclear fuel is ensuring that elements separated are not used to create a weapon. The Purex process, used in all existing reprocessing plants, has been employed for over half a century and has resulted in the accumulation of 240 tonnes of separated reactor-grade plutonium around the world (though some has been used in MOX). While this is not viable for weapons use, it is no longer seen as appropriate and future reprocessing will result in the plutonium being combined with some uranium and possibly with minor actinides. GNEP creates a framework where states that currently employ reprocessing technologies can collaborate to design and deploy advanced separations and fuel fabrication techniques that do not result in the accumulation of separated pure plutonium.

Nuclear Engineering International