At the recent World Nuclear Fuel Cycle conference in Abu Dhabi, a new concept of nuclear fuel leasing was publicly proposed, writes Ian Hore-Lacy.  

The leasing concept has been nebulous, but essentially means that the uranium supplier retains ownership right through to accepting back the high-level wastes, relieving the utility of any responsibility for those wastes. For several years the Khlopin Institute in Russia has been developing for Tenex a new fuel recycling model. REMIX (from Regenerated Mixture) fuel is produced directly from a non-separated mix of recycled uranium and plutonium from reprocessing used fuel, with a low-enriched uranium (LEU, up to 17% U-235) make-up comprising about 20% of the mix. This gives fuel initially with about 1% Pu-239 and 4% U-235 which can sustain burn-up of 50 GWd/t over four years.

The used REMIX fuel is then reprocessed and recycled again, after low-enriched uranium top up. The wastes (fission products and minor actinides) are vitrified, as today from reprocessing for MOX, and stored for geological disposal. REMIX-fuel can be repeatedly recycled with 100% core load in current VVER-1000 reactors, and correspondingly reprocessed many times - up to five times according to Tenex, so that with less than three fuel loads in circulation a reactor could run for 60 years using the same fuel, with LEU recharge and waste removal on each cycle. As with MOX, the use of REMIX fuel reduces consumption of natural uranium in reactors by about 20% at each recycle as compared with open fuel cycle. REMIX can serve as a replacement for existing reactor fuel, though fuel fabrication will be more costly due to high activity levels.

REMIX will give a saving in used fuel storage and disposal costs compared with once-through fuel cycle, matched by the reprocessing cost, though this is expected to reduce. Compared with MOX cycle it has the virtue of not giving rise to any accumulation of reprocessed uranium (RepU) or allowing any separated plutonium. The increasing concentrations of even isotopes of both elements is compensated by the fresh uranium top-up, presumably at increasing enrichment levels. Rosatom plans to load experimental REMIX fuel assemblies into Balakovo unit 3 in June, subject to a Rostechnadzor licence.

Tenex suggests this as a form of fuel leasing from a supplier to a utility, with repeated recycle between them. While the concept is initially for both power plant and fuel cycle set-up in Russia, it can be applied to a power plant in another country, with the utility paying for both enriched uranium top-up and disposal of vitrified waste in Russia as well as the processing. A further extension of the model, in line with tentative findings of the South Australian Royal Commission on the Nuclear Fuel Cycle, is if that utility wanted to acquire uranium from Australia with the benefit of being able to send its high-level wastes for disposal in Australia (valued at about $1.3 million per tonne), an Australian entity could own the uranium throughout the whole REMIX cycle and also the eventual vitrified high-level wastes. In this case Russia (or France, the UK or Japan) simply handles reprocessing, enrichment of fresh uranium, and fuel fabrication, all on some toll basis.

The final report of the SA Royal Commission is due by 6 May, and it is clear that high-level waste storage and disposal will be a significant part of this, along with some way of relating this activity to Australia's role as a significant uranium supplier. Any involvement in the front end of the fuel cycle beyond mining has already been rejected. After a few months of public discussion the state government will respond to the Royal Commission later in the year.

Ian Hore-Lacy  

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Ian Hore-Lacy is a Senior Research Analyst with the World Nuclear Association. One of the WNA's longest serving staffers, Ian is the author of the organisation's Information Library.  

Date: Tuesday, 26 April 2016
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