But if you’ve seen this thorium ball for the 653d time, you may start wondering what exactly the ball summarizes. And what size it should be – apparently, there are different opinions here.

Does it supply all the energy needed to sustain the life you live? Does it include your yearly trip to the Bahama’s? Your kilometers made for commuting? Or just the electricity to last you a lifetime? It looks so small.

Fortunately, we have David MacKays great calculations of what we actually use. A handy number is the consumption of 195 kWh’s per person per day: the amount of energy used by the average affluent person, including household electricity, heating, transportation, food, energy contained in the ‘stuff’ we buy: everything that fits our western lifestyle.

From here, it’s easy to calculate how much energy we need for a lifetime. Let’s say we live 80 years. Of course, we live a bit longer, but I assume we use a bit less energy at infancy and at old age. That means we need 80 x 365 x 195 kWh’s = 5.694.000 kWh’s. This equals 0,00065 GWyr. And in our previous Numbers page, we saw that 1 tonne of thorium or uranium equals 1GWe-yr. This means the energy of a lifetime can be produced with 650 grams of metal.

In the case of Thorium, which has a density of 11,7 kg’s/ltr, 650 grams, equals 55,5 ml. In that case, the ball would be 4,74 cm diameter.

If the ball would be made of Uranium, which has a density of 18,95 kg’s/ltr, the same 650 grams would eaqual 4,04 cm diameter.

On my screen, Sorensen’s hand measures 7,5 cm, and the ball 2,3 cm. If I compare this to my own hand (11 cm wide), the ball should be slightly bigger, about one third in the case of Thorium (the slightly less dense and bigger ball of the two).

But although slightly bigger, it’s still perfectly possible to hold the energy for a lifetime in the palm of your hand, if this energy is produced in a molten salt reactor. //

I went over my calculations again – and realized I had made a mistake. In my calculation, I had used the grams to kWh ratio for electric power, where MacKay provides his number (195kWh per person per day) for thermal power.

This means my thorium balls are … too BIG! The weights should be divided by about 2,5…