Plenty of retiring Nuclear plants. Just do a conversion on the same real-estate and use the waste as fuel.

[EDIT] For a deep dive into Thorium, check out any one of the "Thorium Remix" vids: http://thoriumremix.com/2015/

Terrestrial Energy, Flibe Energy, Molten Energy, Transatomic, ThorCon Power, Copenhagen Atomics, Seaborg, Chinese Academy Of Sciences.

I uprooted unique_parrot2's comment, as it reflected my view about nuclear power, up until last year. Here is the documentary that changed my mind: http://pandoraspromise.com

There is no repository in the world available, that is either guaranteed to be secure for thousands of years of accepted by the population.

Also putting it in the earth has one huge disadvantage: You cannot get it back if something goes wrong.

I can recommend this documentation about the waste disposal problem http://www.imdb.com/title/tt2979302/

But we would have no need for "thousands of years" if the development of nuclear reactors is allowed to advance. Fast breeder reactors can use our current "waste" as fuel, leaving only stable and short-halflife isotopes as waste.

We deposited lots of nuclear waste, and years later discovered it was leaking into the tap water.

Now we have to dig it all back up.

Space dumping is a terrible idea. Expensive and risky.

Best storage solution so far found is what we've mostly been doing so far. Just having a sealed of area and store it for 20 or so years in a special low population and high security area that is protected from rain, frost, and temperature swings and have a good containment in case of container leaks. And then repackage in 20 years time for another 20 years. And so on. I.e. "actively managing" nuclear waste until the end of time.

Fun fact: The inner core of earth is not cooling mostly because of naturally occurring nuclear fission... so in a way our very own planet is full of radioactive waste already :)

(Basically, to hit the sun, you have to scrub out all/most of the velocity from the Earth's orbit, or what you've done is put your waste in an orbit around the Sun that may intersect the Earth's at some point in the future)

To slow down enough that you could fall into the sun you need to kill 30 km/s of velocity. To go fast enough to escape the solar system you only need about 15 km/s. And crashing into Jupiter is even cheaper than that.

http://i.imgur.com/SqdzxzF.png

EDIT: To give some orders of magnitude, the back of the envelope tells me that the sun inflicts about 700 TBq of carbon-14 on us every year. For comparison, countries like the USSR and UK have dumped 85,000 TBq of radioactive waste into the ocean (and Fukushima added another 15,000). I don't know how to judge how much of the vaporized waste would end up back on Earth so it's quite possible I'm wrong in the above.

Besides, exposing radioactive materials to heat does not affect their radioactivity.

1e5 K? You're missing a couple orders of magnitude, there.

The hottest parts of the Sun's surface go up to 20 million Kelvin, and that doesn't "cease to look like any kind of matter we know anything about".

Plus, putting the stuff on top of a highly energetic vehicle is not the safest thing we can do with it.