Studies on fast reactors have historically concentrated on their capability to use plutonium produced in thermal reactors as initial fuel, and subsequently their capacity to produce electricity while breeding new plutonium fuel from the uranium they consume. Since such breeder reactors are unlikely to be deployed at a large industrial scale in the medium term, an excess of plutonium from thermal reactors is accumulating. Consequently some countries are seeking to balance their stockpile of separated plutonium by recycling it in thermal reactors. However, there is a limit to the number of times plutonium can be recycled this way, because its isotopic quality degrades with every cycle. For this reason, fast reactors which are configured for net plutonium burning are being considered for the medium term as means for reducing the stock of plutonium of variable isotopic quality.
In order to understand better the physics of such fast burner reactor systems, benchmark studies were specified for four scenarios: one for an oxide-fuelled fast reactor and three for a metal-fuelled one.
This report covers the performance of fast burner reactors operating in a multirecycle mode. Benchmark results assess metal- fuelled fast burner reactor performance parametrically in transuranic conversion ratio (0.5 to 1.0), and determine the net toxicity flow to a geologic repository when a closed fast burner fuel cycle is used to burn the thermal reactor spent fuel. It is found that a fast burner reactor closed fuel cycle could be utilised to reduce significantly the radiotoxicity originating in the light-water reactor cycle which otherwise was destined for burial in the repository.