The article suggests that 7 kilograms of Plutonium can generate 300 Watts of electricity. That means that it would take about 61,833 metric tonnes to generate 2.65 Gigawatts of electricity needed to power electrodynamic stationkeeping engines for a Rotavator that can launch 50 tonnes of payload to orbit every hour.

Unfortunately the article also says that 7 kilograms represents slightly more than half the US inventory, so I guess they won't be enough Plutonium to power a space elevator using radiothermal generators.

Fortunately, it may be possible to burn small amounts of nuclear fuel for shorter times and generate the necessary power.