Using 0.005% ore, nuclear has higher carbon emissions than gas
Nuclear fuel preparation begins with the mining of uranium containing ores, followed by the crushing of the ore then extraction of the uranium from the powdered ore chemically. All three stages take a lot of energy, most of which comes from fossil fuels. The inescapable fact is that the lower the concentration of uranium in the ore, the higher the fossil fuel energy required to extract uranium.
Table 12 in the Berteen paper confirms the van Leeuwen result that for ore with uranium concentration around 0.01% the carbon footprint of nuclear electricity could be as high as that of electricity generation from natural gas.
This remarkable observation has been further confirmed in a report from the Austrian Institute of Ecology by Andrea Wallner and co-workers. They also point out that using ore with uranium concentration around 0.01% could result in more energy being input to prepare the fuel, build the reactor and so on, than will be generated by the reactor in its lifetime.
According to figures van Leeuwen has compiled from the WISE Uranium Project around 37% of the identified uranium reserves have an ore grade below 0.05%.
A conservative estimate for the future LCA of nuclear power for power stations intended to continue operating into the 2090s and beyond would assume the lowest uranium concentration currently in proven sources, which is 0.005%.
On the basis that the high concentration ores are the easiest to find and exploit, this low concentration is likely to be more typical of yet to be discovered deposits.
Using 0.005% concentration uranium ores, the van Leeuwen, Berteen and Wallner analyses agree a nuclear reactor will have a carbon footprint larger than a natural gas electricity generator. Also, it is unlikely to produce any net electricity over its lifecycle.