[wffurr]

There was just an article about a whole array of “nuclear batteries” using all sorts of decent chemistry: https://news.ycombinator.com/item?id=42118306

Are any of those candidates or are they just too small or with too poor a mass ratio compared to plutonium RTGs?

[jordanb]

Maybe. I don't know. I'd point out that tritium is a gas, so it may be hard to contain for long periods of time especially in space.