Well, this thread is thoroughly hijacked. But of the options for nuclear waste disposal I like the subduction zone idea the best (assuming you have used the waste efficiently too). It seems like a lot less risk and cost than trying to bury it manually or blast it off the planet, and has a finality to it that does not imply any major maintenance tasks for some future generation to inherit, maybe keep an eye on the groundwater, might be worth some technology to ensure the waste gets buried deep and be able to track it, but I don't think you have to "guard" it at the bottom of a trench.
Course someone could devise a mud stirrir-upper, or the ocean currents could change and by some freak scenario move the mud, which could be a far fetched mess. It would also be nice to know there is nothing of "value" in the subduction zones, would want take a closer look before committing it to dump land.
It is kind of like "sweeping it under the rug" on a real grand scale
