A slight digression; there are approximately 1500 tons of Plutonium on the earth today, most made for the fission bombs of the cold war.
As it takes only 2Kg or so to make a bomb this is a real threat to the future.
The only really practical and the safest way to dispose of it is to burn it in Nuclear Power stations.
I'm not generally in favour of Nuclear power but needs must when the devil vomits in your kettle.
In the UK on average 300 Watts/square meter of energy reaches the ground from the Sun. Solar cells are about 15% efficient at the moment but this may rise to around 20%.
That's 45W for on average 12 hours a day, which is 500Wh a day (half a unit). Multiply by your average usable roof area, say 5 square meters, gives you about 2.5 units a day = 2.5x90= 225 units a quarter.
Of cause it would cost an arm and a leg, but prices are falling and the Government could give grants.

PP