The Density

Energy density of nuclear energy is by far the most significant factor in reducing Carbon emissions. We all know that nuclear power is known as powerful. We think of phrases like "harness the atom" and "split the atom." What is hard to grasp about nuclear energy is just how much energy is contained in uranium, plutonium or thorium. It is because of this huge amount of energy created per unit of fuel that makes it so appealing.

From Booklet on IAEA website Energy density comparisons (fuel and land requirements)

The quantity of fuel used to produce a given amount of energy - the energy density - determines in a large measure the magnitude of environmental impacts as it influences the fuel extraction activities, transport requirements, and the quantities of environmental releases and waste. The extraordinary high energy density of nuclear fuel relative to fossil fuels is an advantageous physical characteristic.

One kilogram (kg) of firewood can generate 1 kilowatt-hour (kW·h) of electricity. The values for the other solid fossil fuels and for nuclear power are:

1 kg coal: 3 kW·h
1 kg oil: 4 kW·h
1 kg uranium: 50,000 kW·h
(3,500,000 kW·h with reprocessing)

Consequently, a 1,000 MW(e) plant requires the following number of tonnes (t) of fuel annually:

2,600,000 t coal: 2,000 train cars
(1,300 t each)
2,000,000 t oil: 10 supertankers
30 t uranium: reactor core
(10 cubic metres)

The energy density of fossil and of nuclear fuel allows relatively small power plant areas of some several square kilometers (km²). The low energy density of renewables, measured by land requirements per unit of energy produced, is demonstrated by the large land areas required for a 1000 MW(e) system with values determined by local requirements and climate conditions (solar and wind availability factors ranging from 20 to 40%):

Fossil and nuclear sites: 1–4 km²
Solar thermal or photovoltaic
(PV) parks:
20–50 km²
(a small city)
Wind fields: 50–150 km²
Biomass plantations: 4000–6000 km²
(a province)

Comparing the energy output difference of Uranium to Coal

Comparing the energy output difference of Thorium in Molten Salt Reactors to Uranium to coal

Comparing liquid fuels for automobiles

Explaining the good existing plants and designs and the advantages of new reactors and how the old ones are still good just not as good.