If we are still positive at the five-year mark, that means zero at, say, the ten-year mark, and negative emissions for many decades.
Natural gas has no place in this long-term.
Carbon sequestration is possibly a viable solution. There seem to be solutions in trial (there are numerous questions around it), and even with added costs of capture, it's considerably cheaper and more reliable than other form of energy - moreover, we have it in abundance.
Natural Gas is as viable for the horizon of our future we're able to predict.
In 100 years, every dimension of our tech will have changed so much it's hard to predict. Maybe we solve the nuclear wast problem. Maybe we get fusion. Maybe we have uber cheap solar. Maybe we have dirty easy sequestration. Maybe we have alternatives.
1) Long term storage has some existential risks. Over very long time horizons, these risks become real.
2) Transportation, processing and storage: all of this operational stuff is totally ripe for accidents.
I don't see how that's reasonable, I suggest you might have typed something incorrectly.
There are still quite a number of risks inherent in the Nuclear process that require only a few operational failures for disaster.
If very smart countries and operationally efficient countries like Japan screw up the risks, then anyone can. And that there were mitigating circumstances does not change the fact that Japan still had great governance and scientists and persisted with either risky models or a failure to measure the risk.
Basically, we'd need to suck the risk out of every part of the process in order for it to work well.
I think it's possible.
Again, waste storage is incredibly secure and safe. It wouldn't leech into the water. Nuclear subs have sank into the ocean, and, surprise, there wasn't a global disaster.